Subjects -> CHEMISTRY (Total: 928 journals)
    - ANALYTICAL CHEMISTRY (59 journals)
    - CHEMISTRY (661 journals)
    - CRYSTALLOGRAPHY (23 journals)
    - ELECTROCHEMISTRY (28 journals)
    - INORGANIC CHEMISTRY (45 journals)
    - ORGANIC CHEMISTRY (47 journals)
    - PHYSICAL CHEMISTRY (65 journals)

CHEMISTRY (661 journals)            First | 1 2 3 4 | Last

Showing 201 - 400 of 735 Journals sorted alphabetically
Comptes Rendus : Physique     Open Access   (Followers: 3)
Computational and Theoretical Chemistry     Hybrid Journal   (Followers: 11)
Computational Biology and Chemistry     Hybrid Journal   (Followers: 13)
Computational Chemistry     Open Access   (Followers: 3)
Computers & Chemical Engineering     Hybrid Journal   (Followers: 12)
Coordination Chemistry Reviews     Full-text available via subscription   (Followers: 6)
Corrosion Communications     Open Access  
Critical Reviews in Biochemistry and Molecular Biology     Hybrid Journal   (Followers: 17)
Croatica Chemica Acta     Open Access  
CrystEngComm     Hybrid Journal   (Followers: 10)
Current Catalysis     Hybrid Journal   (Followers: 2)
Current Opinion in Colloid & Interface Science     Hybrid Journal   (Followers: 8)
Current Opinion in Green and Sustainable Chemistry     Hybrid Journal  
Current Opinion in Molecular Therapeutics     Full-text available via subscription   (Followers: 8)
Current Protocols in Nucleic Acid Chemistry     Hybrid Journal  
Current Protocols in Protein Science     Hybrid Journal   (Followers: 1)
Current Research in Chemical Biology     Open Access  
Current Research in Chemistry     Open Access   (Followers: 7)
Current Research in Green and Sustainable Chemistry     Open Access  
Current Science     Open Access   (Followers: 117)
Current Topics in Medicinal Chemistry     Hybrid Journal   (Followers: 7)
Dalton Transactions     Hybrid Journal   (Followers: 23)
Detection     Open Access   (Followers: 3)
Diamond and Related Materials     Hybrid Journal   (Followers: 10)
Doklady Chemistry     Hybrid Journal  
Drying Technology: An International Journal     Hybrid Journal   (Followers: 4)
Ecological Chemistry and Engineering S     Open Access   (Followers: 2)
Educação Química en Punto de Vista     Open Access  
Educación Química     Open Access   (Followers: 1)
Education for Chemical Engineers     Hybrid Journal   (Followers: 5)
EDUSAINS     Open Access  
EJNMMI Radiopharmacy and Chemistry     Open Access  
Elements     Full-text available via subscription   (Followers: 3)
Energetic Materials Frontiers     Open Access  
EnergyChem     Hybrid Journal   (Followers: 1)
Environmental Chemistry     Hybrid Journal   (Followers: 9)
Environmental Chemistry and Ecotoxicology     Open Access  
Environmental Chemistry Letters     Hybrid Journal   (Followers: 4)
Environmental Science & Technology Letters     Hybrid Journal   (Followers: 8)
Environmental Science : Nano     Hybrid Journal   (Followers: 2)
Environmental Toxicology & Chemistry     Hybrid Journal   (Followers: 22)
Enzyme Research     Open Access   (Followers: 4)
Eurasian Chemico-Technological Journal     Open Access  
European Journal of Chemistry     Open Access   (Followers: 25)
European Journal of Histochemistry     Open Access   (Followers: 4)
European Journal of Medicinal Chemistry     Hybrid Journal   (Followers: 20)
European Journal of Medicinal Chemistry Reports     Open Access  
European Online Journal of Natural and Social Sciences     Open Access   (Followers: 4)
Faraday Discussions     Hybrid Journal   (Followers: 3)
Fine Chemical Technologies / Тонкие химические технологии     Open Access  
FirePhysChem     Open Access  
Fitoterapia     Hybrid Journal   (Followers: 4)
FlatChem : Chemistry of Flat Materials     Hybrid Journal  
Fluid Phase Equilibria     Hybrid Journal   (Followers: 4)
Folia Histochemica et Cytobiologica     Open Access  
Folia Microbiologica     Hybrid Journal   (Followers: 2)
Food Chemistry : Molecular Sciences     Open Access   (Followers: 1)
Food Digestion     Hybrid Journal   (Followers: 5)
Food Security     Open Access   (Followers: 11)
Food Structure     Hybrid Journal   (Followers: 3)
Forensic Chemistry     Hybrid Journal   (Followers: 9)
Foundations of Chemistry     Hybrid Journal   (Followers: 4)
Frontiers in Chemistry     Open Access   (Followers: 4)
Frontiers in Soil Science     Open Access  
Frontiers of Chemical Science and Engineering     Hybrid Journal   (Followers: 5)
Fullerenes, Nanotubes and Carbon Nanostructures     Hybrid Journal   (Followers: 9)
Future Medicinal Chemistry     Full-text available via subscription   (Followers: 5)
Gases     Open Access   (Followers: 1)
Gels     Open Access  
Geochemical Transactions     Open Access   (Followers: 2)
Geofluids     Open Access   (Followers: 5)
Giant     Open Access   (Followers: 1)
Graphene     Open Access   (Followers: 7)
Graphene     Full-text available via subscription   (Followers: 3)
Graphene Technology     Hybrid Journal  
Green Analytical Chemistry     Open Access   (Followers: 7)
Green and Sustainable Chemistry     Open Access   (Followers: 4)
Green Chemistry Letters and Reviews     Open Access   (Followers: 6)
Green Synthesis and Catalysis     Open Access  
GSTF Journal of Chemical Sciences (JChem)     Open Access  
Helvetica Chimica Acta     Hybrid Journal   (Followers: 30)
Heritage Science     Open Access   (Followers: 5)
Heteroatom Chemistry     Open Access   (Followers: 3)
High Energy Chemistry     Hybrid Journal  
Indian Chemical Engineer     Hybrid Journal   (Followers: 4)
Indian Journal of Chemical Technology (IJCT)     Open Access   (Followers: 9)
Indian Journal of Chemistry - Section B (IJC-B)     Open Access   (Followers: 10)
Indian Journal of Natural Products and Resources (IJNPR)     Open Access   (Followers: 1)
Indonesian Journal of Chemical Science     Open Access  
Indonesian Journal of Chemistry     Open Access   (Followers: 1)
Indonesian Journal of Pure and Applied Chemistry     Partially Free  
Industrial & Engineering Chemistry     Full-text available via subscription   (Followers: 10)
InfoMat     Open Access  
Inorganic Chemistry     Hybrid Journal   (Followers: 31)
Inorganic Chemistry Communications     Hybrid Journal   (Followers: 13)
Inorganic Materials     Hybrid Journal   (Followers: 5)
Inorganica Chimica Acta     Hybrid Journal   (Followers: 6)
Instrumentation Science & Technology     Hybrid Journal   (Followers: 7)
International Archives of Science and Technology     Open Access  
International Journal for Ion Mobility Spectrometry     Hybrid Journal   (Followers: 1)
International Journal of Adhesion and Adhesives     Hybrid Journal   (Followers: 18)
International Journal of Advanced Chemistry     Open Access   (Followers: 1)
International Journal of Agrochemistry     Full-text available via subscription  
International Journal of Analytical Mass Spectrometry and Chromatography     Open Access   (Followers: 7)
International Journal of Biological and Chemical Sciences     Open Access   (Followers: 4)
International Journal of Biological Chemistry     Open Access   (Followers: 2)
International Journal of Biological, Physical and Chemical Studies     Open Access  
International Journal of Chemical Kinetics     Hybrid Journal   (Followers: 7)
International Journal of Chemical Technology     Open Access   (Followers: 7)
International Journal of Chemistry     Open Access   (Followers: 10)
International Journal of Chemistry and Technology     Open Access   (Followers: 1)
International Journal of Chemoinformatics and Chemical Engineering     Full-text available via subscription   (Followers: 2)
International Journal of Corrosion     Open Access   (Followers: 10)
International Journal of Energetic Materials     Full-text available via subscription  
International Journal of Environmental Chemistry     Full-text available via subscription  
International Journal of Materials and Chemistry     Open Access   (Followers: 7)
International Journal of Medicinal Chemistry     Open Access   (Followers: 4)
International Journal of Minerals, Metallurgy, and Materials     Hybrid Journal   (Followers: 9)
International Journal of Molecular Sciences     Open Access   (Followers: 2)
International Journal of Nano Dimension     Open Access   (Followers: 2)
International Journal of Photoenergy     Open Access   (Followers: 3)
International Journal of Spray and Combustion Dynamics     Full-text available via subscription   (Followers: 15)
International Journal of Thermodynamics and Chemical Kinetics     Full-text available via subscription   (Followers: 2)
International Journal of Tryptophan Research     Open Access  
International Letters of Chemistry, Physics and Astronomy     Open Access   (Followers: 9)
International Research Journal of Pure and Applied Chemistry     Open Access  
Iranian Journal of Chemistry and Chemical Engineering (IJCCE)     Open Access   (Followers: 1)
Iranian Polymer Journal     Hybrid Journal   (Followers: 3)
Iraqi Journal of Pharmacy     Open Access  
Israel Journal of Chemistry     Full-text available via subscription   (Followers: 4)
IUCrData     Open Access   (Followers: 1)
JACS Au     Open Access  
JBIC Journal of Biological Inorganic Chemistry     Hybrid Journal   (Followers: 2)
JCIS Open     Open Access   (Followers: 1)
JOT Journal für Oberflächentechnik     Hybrid Journal   (Followers: 1)
JOT-International Surface Technology     Hybrid Journal   (Followers: 1)
Journal of Adhesion     Hybrid Journal   (Followers: 7)
Journal of Adhesion Science and Technology     Hybrid Journal   (Followers: 10)
Journal of Advances in Chemistry     Open Access   (Followers: 4)
Journal of Agricultural and Food Chemistry     Hybrid Journal   (Followers: 9)
Journal of Agricultural Chemistry and Environment     Open Access   (Followers: 3)
Journal of Al-Qadisiyah for Pure Science     Open Access  
Journal of Amino Acids     Open Access   (Followers: 1)
Journal of Analytical Methods in Chemistry     Open Access   (Followers: 1)
Journal of Analytical Sciences, Methods and Instrumentation     Open Access   (Followers: 4)
Journal of AOAC International     Hybrid Journal   (Followers: 4)
Journal of Applied Chemistry     Open Access   (Followers: 6)
Journal of Applied Solution Chemistry and Modeling     Hybrid Journal   (Followers: 1)
Journal of Applied Spectroscopy     Hybrid Journal   (Followers: 9)
Journal of Biomaterials and Nanobiotechnology     Open Access   (Followers: 6)
Journal of Boron     Open Access  
Journal of Carbohydrate Chemistry     Hybrid Journal   (Followers: 4)
Journal of Catalysis     Hybrid Journal   (Followers: 11)
Journal of Catalyst & Catalysis     Full-text available via subscription   (Followers: 2)
Journal of Chemical & Engineering Data     Hybrid Journal   (Followers: 10)
Journal of Chemical Education     Hybrid Journal   (Followers: 20)
Journal of Chemical Information and Modeling     Hybrid Journal   (Followers: 18)
Journal of Chemical Research     Open Access   (Followers: 6)
Journal of Chemical Reviews     Open Access  
Journal of Chemical Sciences     Partially Free   (Followers: 22)
Journal of Chemical Theory and Computation     Hybrid Journal   (Followers: 21)
Journal of Chemical Thermodynamics     Hybrid Journal   (Followers: 7)
Journal of Cheminformatics     Open Access   (Followers: 7)
Journal of Chemistry     Open Access   (Followers: 6)
Journal of Chemistry, Environmental Sciences and its Applications     Open Access   (Followers: 2)
Journal of Chemometrics     Hybrid Journal   (Followers: 9)
Journal of Chromatography A     Hybrid Journal   (Followers: 61)
Journal of Chromatography Open     Open Access   (Followers: 1)
Journal of Coating Science and Technology     Hybrid Journal  
Journal of Colloid and Interface Science     Hybrid Journal   (Followers: 16)
Journal of Computational Chemistry     Hybrid Journal   (Followers: 21)
Journal of Coordination Chemistry     Hybrid Journal   (Followers: 5)
Journal of Dispersion Science and Technology     Hybrid Journal  
Journal of Education and Science     Open Access   (Followers: 2)
Journal of Encapsulation and Adsorption Sciences     Open Access   (Followers: 1)
Journal of Energy Chemistry     Full-text available via subscription   (Followers: 3)
Journal of Flow Chemistry     Full-text available via subscription   (Followers: 1)
Journal of Fluorescence     Hybrid Journal   (Followers: 3)
Journal of Fluorine Chemistry     Hybrid Journal   (Followers: 7)
Journal of Fuel Chemistry and Technology     Full-text available via subscription   (Followers: 1)
Journal of Great Lakes Research     Hybrid Journal   (Followers: 5)
Journal of Heterocyclic Chemistry     Hybrid Journal   (Followers: 9)
Journal of Immunoassay and Immunochemistry     Hybrid Journal   (Followers: 8)
Journal of Inclusion Phenomena and Macrocyclic Chemistry     Hybrid Journal   (Followers: 1)
Journal of Inorganic Biochemistry     Hybrid Journal   (Followers: 4)
Journal of Ionic Liquids     Open Access  
Journal of Labelled Compounds and Radiopharmaceuticals     Hybrid Journal   (Followers: 4)
Journal of Macromolecular Science, Part A: Pure and Applied Chemistry     Hybrid Journal   (Followers: 1)
Journal of Mass Spectrometry     Hybrid Journal   (Followers: 39)
Journal of Materials Chemistry A : Materials for Energy and Sustainability     Hybrid Journal   (Followers: 40)
Journal of Materials Chemistry B : Materials for Biology and Medicine     Hybrid Journal   (Followers: 11)
Journal of Materials Chemistry C : Materials for Optical, Magnetic and Electronic Devices     Hybrid Journal   (Followers: 17)
Journal of Materials Physics and Chemistry     Open Access   (Followers: 7)
Journal of Materials Research     Full-text available via subscription   (Followers: 13)
Journal of Materials Science and Chemical Engineering     Open Access   (Followers: 1)
Journal of Mathematical Chemistry     Hybrid Journal   (Followers: 5)
Journal of Medicinal Chemistry     Hybrid Journal   (Followers: 136)
Journal of Membrane Science     Hybrid Journal   (Followers: 22)
Journal of Metastable and Nanocrystalline Materials     Full-text available via subscription   (Followers: 1)
Journal of Modern Chemistry & Chemical Technology     Open Access   (Followers: 2)

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ISSN (Online) 2310-2861
Published by MDPI Homepage  [84 journals]
  • Gels, Vol. 8, Pages 391: Polycarboxybetaine-Based Hydrogels for the
           Capture and Release of Circulating Tumor Cells

    • Authors: Hsiu-Wen Chien, Jen-Chia Wu, Ying-Chih Chang, Wei-Bor Tsai
      First page: 391
      Abstract: Circulating tumor cells (CTCs) are indicators for the detection, diagnosis, and monitoring of cancers and offer biological information for the development of personalized medicine. Techniques for the specific capture and non-destructive release of CTCs from millions of blood cells remain highly desirable. Here, we present a CTC capture-and-release system using a disulfide-containing poly(carboxybetaine methacrylate) (pCB) hydrogel. The non-fouling characteristic of pCB prevents unwanted, nonspecific cell binding, while the carboxyl functionality of pCB is used for the conjugation of anti-epithelial cell adhesion molecule (anti-EpCAM) antibodies for the capture of CTCs. The results demonstrated that the anti-EpCAM-conjugated pCB hydrogel captured HCT116 cells from blood, and the capture ratio reached 45%. Furthermore, the captured HCT116 cells were released within 30 min from the dissolution of the pCB hydrogel by adding cysteine, which breaks the disulfide bonds of the crosslinkers. The cells released were viable and able to grow. Our system has potential in the development of a device for CTC diagnosis.
      Citation: Gels
      PubDate: 2022-06-21
      DOI: 10.3390/gels8070391
      Issue No: Vol. 8, No. 7 (2022)
  • Gels, Vol. 8, Pages 392: Silica-Based Aerogel Composites Reinforced with
           Reticulated Polyurethane Foams: Thermal and Mechanical Properties

    • Authors: Beatriz Merillas, Alyne Lamy-Mendes, Fernando Villafañe, Luisa Durães, Miguel Ángel Rodríguez-Pérez
      First page: 392
      Abstract: In this work, silica aerogel composites reinforced with reticulated polyurethane (PU) foams have been manufactured having densities in the range from 117 to 266 kg/m3 and porosities between 85.7 and 92.3%. Two different drying processes were employed (ambient pressure drying and supercritical drying) and a surface modification step was applied to some of the silica formulations. These composites, together with the reference PU foam and the monolithic silica aerogels, were fully characterized in terms of their textural properties, mechanical properties and thermal conductivities. The surface modification with hexamethyldisilazane (HMDZ) proved to improve the cohesion between the reticulated foam and the silica aerogels, giving rise to a continuous network of aerogel reinforced by a polyurethane porous structure. The samples dried under supercritical conditions showed the best interaction between matrixes as well as mechanical and insulating properties. These samples present better mechanical properties than the monolithic aerogels having a higher elastic modulus (from 130 to 450 kPa), a really exceptional flexibility and resilience, and the capacity of being deformed without breaking. Moreover, these silica aerogel-polyurethane foam (Sil-PU) composites showed an excellent insulating capacity, reaching thermal conductivities as low as 14 mW/(m·K).
      Citation: Gels
      PubDate: 2022-06-21
      DOI: 10.3390/gels8070392
      Issue No: Vol. 8, No. 7 (2022)
  • Gels, Vol. 8, Pages 393: Chitosan: Sources, Processing and Modification

    • Authors: Alessandro Pellis, Georg M. Guebitz, Gibson Stephen Nyanhongo
      First page: 393
      Abstract: Chitosan, a copolymer of glucosamine and N-acetyl glucosamine, is derived from chitin. Chitin is found in cell walls of crustaceans, fungi, insects and in some algae, microorganisms, and some invertebrate animals. Chitosan is emerging as a very important raw material for the synthesis of a wide range of products used for food, medical, pharmaceutical, health care, agriculture, industry, and environmental pollution protection. This review, in line with the focus of this special issue, provides the reader with (1) an overview on different sources of chitin, (2) advances in techniques used to extract chitin and converting it into chitosan, (3) the importance of the inherent characteristics of the chitosan from different sources that makes them suitable for specific applications and, finally, (4) briefly summarizes ways of tailoring chitosan for specific applications. The review also presents the influence of the degree of acetylation (DA) and degree of deacetylation (DDA), molecular weight (Mw) on the physicochemical and biological properties of chitosan, acid-base behavior, biodegradability, solubility, reactivity, among many other properties that determine processability and suitability for specific applications. This is intended to help guide researchers select the right chitosan raw material for their specific applications.
      Citation: Gels
      PubDate: 2022-06-21
      DOI: 10.3390/gels8070393
      Issue No: Vol. 8, No. 7 (2022)
  • Gels, Vol. 8, Pages 394: Spatially-Resolved Network Dynamics of Poly(vinyl
           alcohol) Gels Measured with Dynamic Small Angle Light Scattering

    • Authors: Sujata Dhakal, Zehao Chen, Daniel Estrin, Svetlana Morozova
      First page: 394
      Abstract: Hydrogels are cross-linked polymer networks swollen in water. The large solvent content enables hydrogels to have unique physical properties and allows them to be used in diverse applications such as tissue engineering, drug delivery, and absorbents. Gel properties are linked to internal dynamics. While bulk gel dynamics have been studied extensively, how gel networks respond locally to deformation has yet to be understood. Here, poly(vinyl alcohol) (PVA) gels have been stretched to study the effects of deformation on gel dynamics parallel and perpendicular to the stretching direction using dynamic small angle light scattering (DSALS). The implementation of DSALS is described and compared to traditional DLS for PVA gels with different crosslink densities, ranging from 0.75–2%. Despite the orders of magnitude difference in the scattering vector, q, range of the techniques, the dynamics match, and the apparent elastic diffusion coefficient, DA increases linearly with the crosslink density for unstretched gels at a constant 2 wt% concentration. We observe that the elastic motion depends on the direction of stretch, decreasing perpendicular to stretching and increasing at parallel direction. Using DSALS can therefore be an effective tool to evaluate local hydrogel response to deformation.
      Citation: Gels
      PubDate: 2022-06-22
      DOI: 10.3390/gels8070394
      Issue No: Vol. 8, No. 7 (2022)
  • Gels, Vol. 8, Pages 395: Response Surface Methodology for Optimization of
           Buspirone Hydrochloride-Loaded In Situ Gel for Pediatric Anxiety

    • Authors: Marwa H. Abdallah, Dina M. Abdelnabi, Hanaa A. Elghamry
      First page: 395
      Abstract: The purpose of the current investigation was to formulate, assess, and optimize oral in situ gels of buspirone hydrochloride (BH) with the specific end goal of expanding the time the medication spends in the stomach, thereby ensuring an extended medication discharge. This would allow the use of a once-a-day dose of liquid BH formulations, which is ideal for the treatment of pediatric anxiety. In situ gels loaded with BH were prepared using various concentrations of sodium alginate (Na alg.), calcium chloride (CaCl2), and hydroxypropyl methylcellulose (HPMC K15M). The in situ gels exhibited the desired consistency, drug distribution, pH, ability to form gel, and prolonged drug release in vitro. The (33) full factorial design was utilized for the revealing of the ideal figures for the selected independent variables, Na alg. (X1), HPMC (X2), and CaCl2 (X3) based on measurements of the viscosity (Y1) and percentage drug release after 6 h (Y2). A pharmacokinetic study of the optimum formulation on rabbits was also performed. The formulation containing 2% of Na alg., 0.9% of HPMC-K15M, and 0.1125% of CaCl2 was selected as the ideal formulation, which gave the theoretical values of 269.2 cP and 44.9% for viscosity and percentage of drug released after 6 h, respectively. The pharmacokinetic study showed that the selected oral Na alg. in situ gel formulation displayed a prolonged release effect compared to BH solution and the marketed tablet (Buspar®), which was confirmed by the low Cmax and high Tmax values. The optimum oral Na alg. in situ gel showed a 1.5-fold increment in bioavailability compared with the drug solution.
      Citation: Gels
      PubDate: 2022-06-22
      DOI: 10.3390/gels8070395
      Issue No: Vol. 8, No. 7 (2022)
  • Gels, Vol. 8, Pages 396: Effect Evaluation and Action Mechanism Analysis
           of “Profile Control + Plugging Removal” after Chemical

    • Authors: Jianchong Gao, Xiangguo Lu, Xin He, Jinxiang Liu, Kaiqi Zheng, Weijia Cao, Tianyu Cui, Huiru Sun
      First page: 396
      Abstract: The existing plugging removal operation in JZ9-3 oilfield has the disadvantages of small amount of plugging remover, fast injection speed, and short construction time. Under the condition of injection well suction profile reversal, plugging remover is difficult to enter the low permeability part and play the role of deep plugging removal. In order to improve the plugging removal effect, this paper used the physical simulation method to carry out the experimental study and mechanism analysis on the effect of water flooding, chemical flooding, and plugging removal measures of the multi-layer system combination model. The results showed that the recovery of general plugging removal after chemical flooding increases by only 0.70%, while the recovery of ‘profile control + plugging removal’ increases by ‘9.34% + 2.59%’, and the amount of produced liquid decreases by more than 40%. It can be seen that the combined operation of profile control and plugging removal has dual effects of plugging and dredging and synergistic effect, which not only expands the swept volume, but also reduces the inefficient and ineffective cycles. On this basis, the optimization design and effect prediction of the target well W4-2 plugging removal scheme were carried out by using the numerical simulation method. Recommended scheme: inorganic gel profile control agent volume 13,243.6 m3, produced by the main agent (Na2O·nSiO2), isolation fluid (Water), and auxiliary agent (CaCl2) through multiple rounds of alternating injection into the reservoir. The plug removal agent (K2S2O8) injection volume is 100 m3, the concentration is 0.8%. The post-implementation ‘Output/Input’ ratio is expected to be 3.7.
      Citation: Gels
      PubDate: 2022-06-22
      DOI: 10.3390/gels8070396
      Issue No: Vol. 8, No. 7 (2022)
  • Gels, Vol. 8, Pages 397: Gelatinase Responsive Nanogel for Antibacterial
           Phototherapy and Wound Healing

    • Authors: Qianqian Han, Xuan Wang, Lin Qiu, Xinpei Zhou, Zexuan Hui, Xinye Ni, Yang Xuan, Xiaoling Lei, Jianhao Wang
      First page: 397
      Abstract: The unique bactericidal mechanism of metal nanoparticles (MNPs) is considered to be an effective strategy to deal with antibiotic resistance, but the oxidative stress damage caused by excessive accumulation of MNPs to normal cells cannot be ignored. Achieving on-demand release of nano-drugs in specific infection environments is highly attractive. Herein, we constructed a “core-shell” nanogel (G@CuS) based on a copper sulfide (CuS) antimicrobial agent and gelatin for targeted drug release and bacterial clearance in a gelatinase infected microenvironment. G@CuS produced heat and reactive oxygen species (ROS) under the irradiation of a laser, which together with the released Cu2+ cause irreversible and efficient physical damage to the bacteria. Moreover, the encapsulation of gelatin not only limits the biotoxicity of CuS nanodots (NDs), but also effectively promotes the proliferation of mammalian cells. Under the synergy of multiple mechanisms, G@CuS eradicated the colonized bacteria in the wound of mice infected with Staphylococcus aureus (S. aureus) and accelerated wound healing. The proposed application strategy of nanogel is expected to provide a new idea for clinical transformation.
      Citation: Gels
      PubDate: 2022-06-23
      DOI: 10.3390/gels8070397
      Issue No: Vol. 8, No. 7 (2022)
  • Gels, Vol. 8, Pages 398: Eco-Friendly Bio-Hydrogels Based on Antheraea
           Pernyi Silk Gland Protein for Cell and Drug Delivery

    • Authors: Jia Li, Bo-Xiang Wang, De-Hong Cheng, Yan-Hua Lu
      First page: 398
      Abstract: The Antheraea Pernyi silk gland protein originates from natural organisms and synthesized by tussah silk glands and has widely potential biomaterial applications due to the superior biocompatibility. This study investigates the Antheraea Pernyi silk gland protein-based drug-loaded bio-hydrogels for bioengineered tissue fabricated by using an eco-friendly method without the harsh extracting process and the usage of toxic chemicals. The drug-loaded bio-hydrogels exhibited a porous structure and interconnected pore walls. The swelling ratio and water absorption of drug-loaded bio-hydrogels were, respectively, above 95% and 1.5 × 103%. The cumulative release of drug loaded hydrogels all reached more than 90% within 4 h, and this indicates the potential of drug-loaded hydrogels as future drug-carrying biomaterials. RSC96 Schwann cells cultured on drug-loaded hydrogels for 72 h under cell culture medium show no toxic effects and more pro-proliferative effects. The results suggest the suitability of drug-loaded bio-hydrogels as natural biopolymer for the potential in vitro RSC96 cell culture platform and other biomaterial applications.
      Citation: Gels
      PubDate: 2022-06-23
      DOI: 10.3390/gels8070398
      Issue No: Vol. 8, No. 7 (2022)
  • Gels, Vol. 8, Pages 399: High-Protein Foods for Dysphagia: Manipulation of
           Mechanical and Microstructural Properties of Whey Protein Gels Using
           De-Structured Starch and Salts

    • Authors: Cai Ling Ang, Kelvin Kim Tha Goh, Kaiyang Lim, Lara Matia-Merino
      First page: 399
      Abstract: This study focuses on understanding the effect of ionic strength on the mechanical and microstructural properties of novel composite gels containing 13% whey protein isolate (WPI) and 4% de-structured waxy potato starch (DWPS). The DWPS is a physically modified waxy potato starch treated at 140 °C for 30 min under constant shear. Thermodynamic incompatibility between WPI and DWPS was observed upon the addition of NaCl (~75 mM) or CaCl2 (10–75 mM). The combined effects of such thermodynamic incompatibility with the changes in protein connectivity induced by varied ionic strength led to the formation of distinctive gel structures (inhomogeneous self-supporting gels with a liquid centre and weak gels with paste-like consistency) that were different from thermodynamic compatible homogeneous self-supporting gels (pure WPI and WPI + maltodextrin gels). At ≥ 250 mM NaCl, instead of a paste-like texture, a recovered soft and creamy self-supporting gel structure was observed when using DWPS. The ability to generate a range of textures in WPI gelation-based foods by using DWPS under different ionic conditions, is a feasible strategy for formulating high-protein foods for dysphagia—aimed to be either thickened fluids or soft solids. Additionally, this acquired knowledge is also relevant when formulating food gels for 3-D printing.
      Citation: Gels
      PubDate: 2022-06-23
      DOI: 10.3390/gels8070399
      Issue No: Vol. 8, No. 7 (2022)
  • Gels, Vol. 8, Pages 400: Injectable DNA Hydrogel-Based Local Drug Delivery
           and Immunotherapy

    • Authors: Qi Wang, Yanfei Qu, Ziyi Zhang, Hao Huang, Yufei Xu, Fengyun Shen, Lihua Wang, Lele Sun
      First page: 400
      Abstract: Regulated drug delivery is an important direction in the field of medicine and healthcare research. In recent years, injectable hydrogels with good biocompatibility and biodegradability have attracted extensive attention due to their promising application in controlled drug release. Among them, DNA hydrogel has shown great potentials in local drug delivery and immunotherapy. DNA hydrogel is a three-dimensional network formed by cross-linking of hydrophilic DNA strands with extremely good biocompatibility. Benefiting from the special properties of DNA, including editable sequence and specificity of hybridization reactions, the mechanical properties and functions of DNA hydrogels can be precisely designed according to specific applications. In addition, other functional materials, including peptides, proteins and synthetic organic polymers can be easily integrated with DNA hydrogels, thereby enriching the functions of the hydrogels. In this review, we first summarize the types and synthesis methods of DNA hydrogels, and then review the recent research progress of injectable DNA hydrogels in local drug delivery, especially in immunotherapy. Finally, we discuss the challenges facing DNA hydrogels and future development directions.
      Citation: Gels
      PubDate: 2022-06-24
      DOI: 10.3390/gels8070400
      Issue No: Vol. 8, No. 7 (2022)
  • Gels, Vol. 8, Pages 401: Fabrication and Characterization of Poly (Vinyl
           Alcohol)-Chitosan-Capped Silver Nanoparticle Hybrid Membranes for
           Pervaporation Dehydration of Ethanol

    • Authors: Manu L. Naik, Ashok M. Sajjan, T. M. Yunus Khan, Ashwini M, Sharanappa Achappa, Nagaraj R. Banapurmath, Narasimha H. Ayachit, Mostafa A. H. Abdelmohimen
      First page: 401
      Abstract: Chitosan-capped silver nanoparticle (CS-capped AgNPs)-incorporated poly (vinyl alcohol) (PVA) hybrid membranes were prepared by a solution-casting technique for ethanol dehydration via pervaporation. The incorporation of CS-capped AgNPs into the PVA membrane and its influence on membrane properties and pervaporation-separation process of azeotropic water/ethanol mixture was studied. The addition of CS-capped AgNPs into the PVA membrane reduced the crystallinity, thereby increasing the hydrophilicity and swelling degree of the hybrid membrane, supported by contact angle (CA) analyzer and swelling degree experiments, respectively. Fourier transform infrared spectroscopy (FTIR) demonstrated the formation of polymeric matrix between PVA and CS and also the binding of AgNPs onto the functional group of CS and PVA, which was also reflected in the microstructure images demonstrated by scanning electron microscopy (SEM) and by 2θ angle of wide-angle X-ray diffraction (WAXD). The effect of CS-capped AgNPs on the thermal stability of the hybrid membrane was demonstrated by differential scanning calorimetry (DSC) and thermogravimetric analyzer (TGA). These characteristics of the hybrid membrane positively impact the efficiency of the dehydration of ethanol, as indicated by pervaporation experiments. The best performances in total flux (12.40 ± 0.20 × 10−2 kg/m2 h) and selectivity (3612.33 ± 6.03) at 30 °C were shown for CS-capped AgNPs PVA hybrid membrane containing 2 wt.% CS-capped AgNPs (M-4). This confirms that the developed hybrid membranes can be efficiently used to separate water from azeotropic aqueous ethanol.
      Citation: Gels
      PubDate: 2022-06-24
      DOI: 10.3390/gels8070401
      Issue No: Vol. 8, No. 7 (2022)
  • Gels, Vol. 8, Pages 402: Preparation, Characterization of Pregabalin and
           Withania coagulans Extract-Loaded Topical Gel, and Their Comparative
           Effect on Burn Injury

    • Authors: Anam Asghar, Muhammad Naeem Aamir, Fatima Akbar Sheikh, Naveed Ahmad, Nasser F. Alotaibi, Syed Nasir Abbas Bukhari
      First page: 402
      Abstract: The current study depicts the comparative effects of nanogel using Withania coagulans extract, pregabalin alone, and a co-combination gel. The gels prepared were then analyzed for conductivity, viscosity, spread ability, globule size, zeta potential, polydispersity index, and TEM. The globule size of the co-combination gel, determined by zeta sizer, was found to be (329 ± 0.573 nm). FTIR analysis confirms the successful development of gel, without any interaction. Drug distribution at the molecular level was confirmed by XRD. DSC revealed no bigger thermal changes. TEM images revealed spherical molecules with sizes of 200 nm for the co-combination gel. In vivo studies were carried out by infliction of third degree burn wounds on rat skin, and they confirmed that pregabalin and Withania coagulans heals the wound more effectively, with a wound contraction rate of 89.95%, compared to remaining groups. Anti-inflammatory activity (IL-6 and TNF-α), determined by the ELISA technique, shows that the co-combination gel group reduces the maximum inflammation with TNF-α value (132.2 pg/mL), compared to the control (140.22 pg/mL). Similarly, the IL-6 value was found to be (78 pg/mL) for the co-combination gel and (81 pg/mL) in the case of the control. Histopathologically, the co-combination gel heals wounds more quickly, compared to individual gel. These outcomes depict that a co-combination gel using plant extracts and drugs can be successfully used to treat burn injury.
      Citation: Gels
      PubDate: 2022-06-24
      DOI: 10.3390/gels8070402
      Issue No: Vol. 8, No. 7 (2022)
  • Gels, Vol. 8, Pages 403: Gene Expression and Characterization of Iturin A
           Lipopeptide Biosurfactant from Bacillus aryabhattai for Enhanced Oil

    • Authors: Deepak A. Yaraguppi, Zabin K. Bagewadi, Nilkamal Mahanta, Surya P. Singh, T. M. Yunus Khan, Sanjay H. Deshpande, Chaitra Soratur, Simita Das, Dimple Saikia
      First page: 403
      Abstract: Biosurfactants are eco-friendly surface-active molecules recommended for enhanced oil recovery techniques. In the present study, a potential lipopeptide (biosurfactant) encoding the iturin A gene was synthesized from Bacillus aryabhattai. To improvise the yield of the lipopeptide for specific applications, current research tends toward engineering and expressing recombinant peptides. An iturin A gene sequence was codon-optimized, amplified with gene-specific primers, and ligated into the pET-32A expression vector to achieve high-level protein expression. The plasmid construct was transformed into an E. coli BL21 DE3 host to evaluate the expression. The highly expressed recombinant iturin A lipopeptide was purified on a nickel nitrilotriacetic acid (Ni-NTA) agarose column. Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) revealed that the purity and molecular mass of iturin A was 41 kDa. The yield of recombinant iturin A was found to be 60 g/L with a 6.7-fold increase in comparison with our previously published study on the wild strain. The approach of cloning a functional fragment of partial iturin A resulted in the increased production of the lipopeptide. When motor oil was used, recombinant protein iturin A revealed a biosurfactant property with a 74 ± 1.9% emulsification index (E24). Purified recombinant protein iturin A was characterized by mass spectrometry. MALDI-TOF spectra of trypsin digestion (protein/trypsin of 50:1 and 25:1) showed desired digested mass peaks for the protein, further confirming the identity of iturin A. The iturin A structure was elucidated based on distinctive spectral bands in Raman spectra, which revealed the presence of a peptide backbone and lipid. Recombinant iturin A was employed for enhanced oil recovery through a sand-packed column that yielded 61.18 ± 0.85% additional oil. Hence, the novel approach of the high-level expression of iturin A (lipopeptide) as a promising biosurfactant employed for oil recovery from Bacillus aryabhattai is not much reported. Thus, recombinant iturin A demonstrated its promising ability for efficient oil recovery, finding specific applications in petroleum industries.
      Citation: Gels
      PubDate: 2022-06-25
      DOI: 10.3390/gels8070403
      Issue No: Vol. 8, No. 7 (2022)
  • Gels, Vol. 8, Pages 404: An Engineered Protein-Based Building Block
           (Albumin Methacryloyl) for Fabrication of a 3D In Vitro Cryogel Model

    • Authors: Xueming Niu, Mian Lin, Bae Hoon Lee
      First page: 404
      Abstract: Drug-induced liver injury (DILI) is a leading cause of attrition in drug development or withdrawal; current animal experiments and traditional 2D cell culture systems fail to precisely predict the liver toxicity of drug candidates. Hence, there is an urgent need for an alternative in vitro model that can mimic the liver microenvironments and accurately detect human-specific drug hepatotoxicity. Here, for the first time we propose the fabrication of an albumin methacryloyl cryogel platform inspired by the liver’s microarchitecture via emulating the mechanical properties and extracellular matrix (ECM) cues of liver. Engineered crosslinkable albumin methacryloyl is used as a protein-based building block for fabrication of albumin cryogel in vitro models that can have potential applications in 3D cell culture and drug screening. In this work, protein modification, cryogelation, and liver ECM coating were employed to engineer highly porous three-dimensional cryogels with high interconnectivity, liver-like stiffness, and liver ECM as artificial liver constructs. The resulting albumin-based cryogel in vitro model provided improved cell–cell and cell–material interactions and consequently displayed excellent liver functional gene expression, being conducive to detection of fialuridine (FIAU) hepatotoxicity.
      Citation: Gels
      PubDate: 2022-06-25
      DOI: 10.3390/gels8070404
      Issue No: Vol. 8, No. 7 (2022)
  • Gels, Vol. 8, Pages 405: Edible Xanthan/Propolis Coating and Its Effect on
           Physicochemical, Microbial, and Sensory Quality Indices in Mackerel Tuna
           (Euthynnus affinis) Fillets during Chilled Storage

    • Authors: Aly Farag El Sheikha, Ayman Younes Allam, Emel Oz, Muhammad Rizwan Khan, Charalampos Proestos, Fatih Oz
      First page: 405
      Abstract: Worldwide aquaculture production is increasing, but with this increase comes quality and safety related problems. Hence, there is an urgent need to develop potent technologies to extend the shelf life of fish. Xanthan gum is commonly used in the food industry because of its high-water solubility, stability of its aqueous solutions in a wide pH range, and high viscosity. One of its modern food applications is its use as a gelling agent in edible coatings building. Therefore, in this study, the effect of xanthan coating containing various concentrations (0, 1, 2%; w/v) of ethanolic extract of propolis (EEP) on physicochemical, microbial, and sensory quality indices in mackerel fillets stored at 2 °C for 20 days was evaluated. The pH, peroxide value, K-value, TVB-N, TBARS, microbiological and sensory characteristics were determined every 5 days over the storage period (20 days). Samples treated with xanthan (XAN) coatings containing 1 and 2% of EEP were shown to have the highest level of physicochemical protection and maximum level of microbial inhibition (p < 0.05) compared to uncoated samples (control) over the storage period. Furthermore, the addition of EEP to XAN was more effective in notably preserving (p < 0.05) the taste and odor of coated samples compared to control.
      Citation: Gels
      PubDate: 2022-06-25
      DOI: 10.3390/gels8070405
      Issue No: Vol. 8, No. 7 (2022)
  • Gels, Vol. 8, Pages 406: In Vitro Evaluation of Smart and pH-Sensitive
           Chondroitin Sulfate/Sodium Polystyrene Sulfonate Hydrogels for Controlled
           Drug Delivery

    • Authors: Muhammad Suhail, I-Hui Chiu, Ming-Chia Hung, Quoc Lam Vu, I-Ling Lin, Pao-Chu Wu
      First page: 406
      Abstract: Ibuprofen is an antipyretic and analgesic drug used for the management of different inflammatory diseases, such as rheumatoid arthritis and osteoarthritis. Due to a short half-life and rapid elimination, multiple doses of ibuprofen are required in a day to maintain pharmacological action for a long duration of time. Due to multiple intakes of ibuprofen, certain severe adverse effects, such as gastric irritation, bleeding, ulcers, and abdominal pain are produced. Therefore, a system is needed which not only prolongs the release of ibuprofen but also overcomes the drug’s adverse effects. Hence, the authors have synthesized chondroitin sulfate/sodium polystyrene sulfonate–co-poly(acrylic acid) hydrogels by the free radical polymerization technique for the controlled release of ibuprofen. Sol-gel, porosity, swelling, and drug release studies were performed on the fabricated hydrogel. The pH-responsive behavior of the fabricated hydrogel was determined by both swelling and drug release studies in three different pH values, i.e., pH 1.2, 4.6, and 7.4. Maximum swelling and drug release were observed at pH 7.4, as compared to pH 4.6 and 1.2. Similarly, the structural arrangement and crosslinking of the hydrogel contents were confirmed by Fourier transform infrared spectroscopy (FTIR). Scanning electron microscopy (SEM) evaluated the hard and irregular surface with a few macrospores of the developed hydrogel, which may be correlated with the strong crosslinking of polymers with monomer content. Similarly, thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) demonstrated the high thermal stability of the formulated hydrogel, as compared to pure polymers. A decrease in the crystallinity of chondroitin sulfate and sodium polystyrene sulfonate after crosslinking was revealed by powder X-ray diffraction (PXRD). Thus, considering the results, we can demonstrate that a developed polymeric network of hydrogel could be used as a safe, stable, and efficient carrier for the controlled release of ibuprofen.
      Citation: Gels
      PubDate: 2022-06-25
      DOI: 10.3390/gels8070406
      Issue No: Vol. 8, No. 7 (2022)
  • Gels, Vol. 8, Pages 407: Anti-Fouling Performance of Hydrophobic Hydrogels
           with Unique Surface Hydrophobicity and Nanoarchitectonics

    • Authors: Liangpeng Zeng, Ziqi Liu, Jingliang Huang, Xiaolin Wang, Hui Guo, Wei-Hua Li
      First page: 407
      Abstract: Hydrogel is a kind of soft and wet matter, which demonstrates favorable fouling resistance owing to the hydration anti-adhesive surfaces. Different from conventional hydrogels constructed by hydrophilic or amphiphilic polymers, the recently invented “hydrophobic hydrogels” composed of hydrophobic polymers exhibit many unique properties, e.g., surface hydrophobicity and high water content, suggesting promising applications in anti-fouling. In this paper, a series of hydrophobic hydrogels were prepared with different chemical structures and water content for anti-fouling investigations. The hydrophobic hydrogels showed high static water contact angles (WCAs > 90°), indicating remarkable surface hydrophobicity, which is abnormal for conventional hydrogels. Compared with the conventional hydrogels, all the hydrophobic hydrogels exhibited less than 4% E. coli biofilm coverage, showing a contrary trend of anti-fouling ability to the water content inside the polymer. Typically, the poly(2-(2-ethoxyethoxy)ethyl acrylate) (PCBA) and poly(tetrahydrofurfuryl acrylate) (PTHFA) hydrogels with relatively high surface hydrophobicity showed as low as 5.1% and 2.4% E. coli biofilm coverage even after incubation for 7 days in bacteria suspension, which are about 0.32 and 0.15 times of that on the hydrophilic poly(N,N-dimethylacrylamide) (PDMA) hydrogels, respectively. Moreover, the hydrophobic hydrogels exhibited a similar anti-adhesion ability and trend to algae S. platensis. Based on the results, the surface hydrophobicity mainly contributes to the excellent anti-fouling ability of hydrophobic hydrogels. In the meantime, the too-high water content may be somehow detrimental to anti-fouling performance.
      Citation: Gels
      PubDate: 2022-06-27
      DOI: 10.3390/gels8070407
      Issue No: Vol. 8, No. 7 (2022)
  • Gels, Vol. 8, Pages 408: Concentration-Dependent Emission of Annealed
           Sol-Gel Layers Incorporated with Rhodamine 19 and 6G as the Route to
           Tunable High-Temperature Luminescent Materials

    • Authors: Maria Zdończyk, Bartłomiej Potaniec, Marta Fiedot-Toboła, Tomasz Baraniecki, Joanna Cybińska
      First page: 408
      Abstract: The sol-gel technology allows for the development of materials for nonlinear optics and photonics through the synthesis of multifunctional ceramic materials. Although the nature of the amorphous matrix allows the material to be doped with a large amount of the active components without quenching, it may affect the spectroscopic characteristics of the dye (e.g., result in a shift of absorption and emission peaks with drying time, presumably with a change of concentration). This study presents the material (SiO2 impregnated with organic dyes—Rhodamine 6G and 19) with tunable emissions obtained by the authors upon annealing at different temperatures within the range of 100–300 °C. Possible observed effects were discussed based on spectroscopic properties and thermal studies of the synthesized material. Concerning annealing at different temperatures, an effect on concentration was observed. At the same time, a longer heating process at 300 °C revealed a protective function of sol-gel-derived silica for the organic dye; the longer heating did not cause any further significant changes in the dye’s emission, which indicates the preservative role of the sol-gel layers. Furthermore, etching tests of thin layers were conducted, resulting in smooth side edges of the waveguide. The tests have shown that it is possible to use dye-doped sol-gel layers as active components in photonics platforms.
      Citation: Gels
      PubDate: 2022-06-28
      DOI: 10.3390/gels8070408
      Issue No: Vol. 8, No. 7 (2022)
  • Gels, Vol. 8, Pages 409: Significant Interfacial Dielectric Relaxation of
           Covalently Bonded Ice-Hydrogels

    • Authors: Yongqiang Li, Liufang Chen, Chuanfu Li, Lin Lin, Zhibo Yan, Junming Liu
      First page: 409
      Abstract: Hydrogels are composed of a three-dimensional network of cross-linked hydrophilic polymer chains and large amounts of water. The physicochemical properties of the polymer-water interface in hydrogels draw our attention. Due to the complex structure of hydrogel systems, it is still a challenge to investigate the interfacial layer properties of hydrogels through experiments. In this work, we investigate the properties of the covalently bonded chitosan-based ice-hydrogels interfacial layer by dielectric relaxation spectroscopy (DRS) techniques in the presence of avoided electrode polarization. The DRS data exhibit that the polymer-water interfacial layer has a strong dielectric signal response, which indicates that a large number of polar electric dipoles or polar molecules may be contained in the interfacial layer. The variable temperature dielectric relaxation behavior of a series of chitosan-base ice-hydrogels showed that the value of dielectric activation energy for different water contents is about 180 kJ/mol, which is much larger than that of the polymer and ice phases, suggesting a strong coupling of polar electric dipoles within the interfacial layer. This work demonstrates the important role of the polymer-water interface in covalently bonded hydrogels, which will provide assistance in the design and application of covalently bonded hydrogels.
      Citation: Gels
      PubDate: 2022-06-28
      DOI: 10.3390/gels8070409
      Issue No: Vol. 8, No. 7 (2022)
  • Gels, Vol. 8, Pages 410: Influence of Gel Stage from Cellulose Dissolution
           in NaOH-Water System on the Performances of Cellulose Allomorphs-Based

    • Authors: Diana Elena Ciolacu, Daniela Rusu, Raluca Nicoleta Darie-Niţă, Daniel Tîmpu, Florin Ciolacu
      First page: 410
      Abstract: Novel hydrogels were prepared starting from different cellulose allomorphs (cellulose I, II, and III), through a swelling stage in 8.5% NaOH aqueous solution, followed by freezing at low temperature (−30 °C), for 24 h. After thawing at room temperature, the obtained gels were chemical cross-linked with epichlorohydrin (ECH), at 85 °C. The swelling degrees of the hydrogels were investigated, and a complex dependence on the type of the cellulose allomorph was found. Moreover, the gel stage has been shown to play a key role in the design of hydrogels with different performances, following the series: H-CII > H-CI > H-CIII. The correlations between the allomorph type and the morphological characteristics of hydrogels were established by scanning electron microscopy (SEM). The hydrogel H-CII showed the biggest homogeneous pores, while H-CIII had the most compacted pores network, with small interconnected pores. The rheological studies were performed in similar shear regimes, and a close correlation between the strength of the gel structure and the size of the gel fragments was observed. In the case of hydrogels, it has been shown that H-CII is softer, with a lower resistance of the hydrogel (G′) above the oscillation frequencies tested, but it maintains its stable structure, while H-CIII has the highest modulus of storage and loss compared to H-CI and H-CII, having a stronger and more rigid structure. The X-ray diffraction (XRD) method showed that the crystalline organization of each type of allomorph possesses a distinctive diffraction pattern, and, in addition, the chemically cross-linking reaction has been proved by a strong decrease of the crystallinity. Attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy provided clear evidence of the chemical cross-linking of cellulose allomorphs with ECH, by the alteration of the crystal structure of cellulose allomorphs and by the formation of new ether bands.
      Citation: Gels
      PubDate: 2022-06-29
      DOI: 10.3390/gels8070410
      Issue No: Vol. 8, No. 7 (2022)
  • Gels, Vol. 8, Pages 411: Editorial on Special Issue “New Era in the
           Volume Phase Transition of Gels”

    • Authors: Masayuki Tokita, Masahiko Annaka, Gerald S. Manning
      First page: 411
      Abstract: The Special Issue of gels titled “Advancements in Gel Science” has been published from MDPI in 2019 [...]
      Citation: Gels
      PubDate: 2022-06-30
      DOI: 10.3390/gels8070411
      Issue No: Vol. 8, No. 7 (2022)
  • Gels, Vol. 8, Pages 412: Synthesis and Characterization of
           Chitosan-Decorated Nanoemulsion Gel of 5-Fluorouracil for Topical Delivery

    • Authors: Asif Nawaz, Muhammad Shahid Latif, Maha Abdallah Alnuwaiser, Shafi Ullah, Muhammad Iqbal, Mulham Alfatama, Vuanghao Lim
      First page: 412
      Abstract: (1) Background: The present study aimed to prepare chitosan-coated nanoemulsion gel containing 5-fluorouracil for enhanced topical delivery. (2) Methods: To formulate the nanoemulsion gel, oleic acid was used as the oil phase and Carbopol 940 as a gelling agent. Chitosan was used as a coating agent to control the release of 5-FU. Drug–excipient compatibility was evaluated using ATR-FTIR. The prepared nanoemulsion formulations were characterized based on particle size distribution, zeta potential, % encapsulation efficiency and drug content. In vitro drug release, skin drug retention and ex vivo permeation profiles were performed across rat skin using a Franz diffusion cell. Skin irritation experiments were also conducted on rats to examine the irritation potential of the formulations. (3) Results: It was found that the drug and excipients were compatible and chitosan successfully coated 5-FU, as demonstrated by ATR-FTIR results. The introduction of chitosan increased the size and zeta potential of the nanoemulsion. The 5-FU release in vitro was significantly lowered in the case of chitosan-decorated nanoemulsion (5-FU-C-NE), whereas the permeation and skin drug retention were higher in the case of 5-FU-C-NE. The formulations were proven non-irritant to the skin of the rats. The optimized formulation of the nanoemulsion was introduced into 1% Carbopol 940 gel. Incorporating the nanoemulsion into the gel further reduced the drug release in vitro and ex vivo permeation, whereas the retention of the drug in the skin was significantly increased (ANOVA; p < 0.05). The increase in skin retention was due to the presence of chitosan and Carbopol 940. The in vitro and ex vivo results were also confirmed with in vivo studies. Incorporating nanoemulsion into gel has resulted in higher Tmax, longer half-life and greater skin drug retention. (4) Conclusion: The results suggest that chitosan-decorated nanoemulsion gel is safe and can potentially be used to promote 5-FU skin retention, which is ideal for skin diseases such as melanoma.
      Citation: Gels
      PubDate: 2022-06-30
      DOI: 10.3390/gels8070412
      Issue No: Vol. 8, No. 7 (2022)
  • Gels, Vol. 8, Pages 413: Application of Xanthan Gum and Hyaluronic Acid as
           Dermal Foam Stabilizers

    • Authors: Fanni Falusi, Szilvia Berkó, Anita Kovács, Mária Budai-Szűcs
      First page: 413
      Abstract: Foams are increasingly popular in the field of dermatology due to their many advantages such as easy spreading, good skin sensation, and applicability in special skin conditions. One of the critical points of foam formulation is the choice of the appropriate stabilizing ingredients. One of the stability-increasing strategies is retarding the liquid drainage of liquid films from the foam structure. Therefore, our aim was the application of different hydrogel-forming polymers in order to retain the stabilizing liquid film. Dexpanthenol and niacinamide-containing foams were formulated, where xanthan gum and hyaluronic acid were used as foam-stabilizing polymers. Amplitude (LVE range) and frequency sweep (G’, G”, tanδ, and frequency dependency) were applied as structure- and stability-indicating rheological parameters. The rheological data were compared with the results of the cylinder method, microscopical images, and the spreadability measurements.
      Citation: Gels
      PubDate: 2022-06-30
      DOI: 10.3390/gels8070413
      Issue No: Vol. 8, No. 7 (2022)
  • Gels, Vol. 8, Pages 414: Azobenzene Based Photo-Responsive Hydrogel:
           Synthesis, Self-Assembly, and Antimicrobial Activity

    • Authors: Runmiao Yang, Wei Jin, Chingcheng Huang, Yuhai Liu
      First page: 414
      Abstract: A new azobenzene-based symmetric amphiphile was synthesized and characterized using 1H NMR spectroscopy. Its self-assembly behavior as well as photo-responsive behavior in its solution and gel states were investigated. Such a compound can self-assemble into fiber mesophases in water solvent. After irradiation of the gels with UV light, the trans isomer of the compound rapidly photoisomerized to the cis isomer, which resulted in a rapid destruction of the gel. High temperature also caused a rapid drop in viscosity. To verify the antimicrobial activity of the hydrogel, live and death assays of human fibroblasts L929 properties were used for in vitro cell viability studies. The compound was converted to the terminal tertiary amine in a quaternary ammonium salt molecule by using hydrochloric acid. This azobenzene quaternary ammonium salt has a relatively better antimicrobial effect biocidal activity that was demonstrated when challenged against Escherichia coli on in vitro conditions.
      Citation: Gels
      PubDate: 2022-07-01
      DOI: 10.3390/gels8070414
      Issue No: Vol. 8, No. 7 (2022)
  • Gels, Vol. 8, Pages 415: Construction and Tribological Properties of
           Biomimetic Cartilage-Lubricating Hydrogels

    • Authors: Qiuyi Chen, Sa Liu, Zhongrun Yuan, Hai Yang, Renjian Xie, Li Ren
      First page: 415
      Abstract: Articular cartilage provides ultralow friction to maintain the physiological function of the knee joint, which arises from the hierarchical complex composed of hyaluronic acid, phospholipids, and lubricin, covering the cartilage surface as boundary lubrication layers. Cartilage-lubricating polymers (HA/PA and HA/PM) mimicking this complex have been demonstrated to restore the lubrication of cartilage via hydration lubrication, thus contributing to the treatment of early osteoarthritis (OA) in vivo. Here, biomimetic cartilage-lubricating hydrogels (HPX/PVA) were constructed by blending HA/PA and HA/PM (HPX) with polyvinyl alcohol (PVA) to improve the boundary lubrication and wear properties, so that the obtained hydrogels may offer a solution to the main drawbacks of PVA hydrogels used as cartilage implants. The HPX/PVA hydrogels exhibited good physicochemical and mechanical properties through hydrogen-bonding interactions, and showed lower friction and wear under the boundary lubrication and fluid film lubrication mechanisms, which remained when the hydrogels were rehydrated. Our strategy may provide new insights into exploring cartilage-inspired lubricating hydrogels.
      Citation: Gels
      PubDate: 2022-07-01
      DOI: 10.3390/gels8070415
      Issue No: Vol. 8, No. 7 (2022)
  • Gels, Vol. 8, Pages 416: Mucoadhesive and Antimicrobial Allantoin/β

    • Authors: Filip, Macocinschi, Zaltariov, Gafitanu, Tuchilus, Bele, Ciubotaru, Stoleru, Bargan
      First page: 416
      Abstract: Allantoin and its -cyclodextrin and hydroxypropyl-β-cyclodextrin inclusion complexes 1:1 have been used to prepare carbopol-based mucoadhesive gels. The gelation process occurred by adjustment with glycerol 10% in the presence of triethanolamine. The structural features induced by the presence of allantoin and the corresponding β-cyclodextrins inclusion complexes have been first investigated by infrared spectroscopy highlighting strong interactions within the gels network and ideal crosslinks for the self-healing behavior. The hydrophilicity of the gels was investigated by the determination of the surface tension parameters and the free energy of hydration. The interfacial free energy values indicated prolonged biocompatibility with blood. The gels-water molecule interactions in terms of sorption, permeability, and diffusion coefficients were evaluated by dynamic vapor sorption analysis. The self-assembly process through intermolecular H-bonding, the high hydrophilicity, the mechanical performance, the hydrolytic stability in simulated biological media, the biocompatibility with normal human dermal fibroblast (NHDF) cells, the mucoadhesivity and antimicrobial activity on selected microorganism species (S. Aureus and C. albicans) of the allantoin-based gels recommend them as promising scaffold alternatives in regenerative medicine.
      Citation: Gels
      PubDate: 2022-07-02
      DOI: 10.3390/gels8070416
      Issue No: Vol. 8, No. 7 (2022)
  • Gels, Vol. 8, Pages 327: Ginger Essential Oil as an Active Addition to
           Composite Chitosan Films: Development and Characterization

    • Authors: Sawsan Ali Al-Hilifi, Rawdah Mahmood Al-Ali, Anka Trajkovska Petkoska
      First page: 327
      Abstract: The recent interest in food biopackaging is showing an increasing trend, especially in the development of antimicrobial coatings and films. The focus of this study is to assess the potential application of ginger (Zingiber officinale) essential oil (GEO) to polysaccharide films based on chitosan (CHf) and their utilization as an active edible packaging. The films were characterized by different instrumental techniques, and data indicated significant differences (p < 0.05) in the chemical composition of the samples. Forty-seven active compounds from ginger rhizomes were identified in the examined essential oil by gas chromatography mass spectrometer (GC-MS). Fourier transforms infrared spectra (FT-IR) confirmed an interaction between the hydroxyl groups of the phenolic compounds of the essential oil and the amine groups of the bioactive matrix, as shown by the peaks at wavenumbers 1639 cm−1 and 1558 cm−1. X-ray diffraction data suggested a lower crystallinity in the CHf due to the addition of GEO. Differential scanning calorimetric (DSC) analysis revealed that the CHf possessed high thermal stability, especially when different concentrations of GEO were added. The bioactive CHf showed distinct activity against both Gram-positive and Gram-negative bacteria, such as Staphylococcus aureus, Bacillus subtilis, Streptococcus sp., Escherichia coli, Salmonella sp., and Pseudomonas aeruginosa, thus improving the antimicrobial activity to these films. The results provide a comprehensive insight into the importance of films with incorporated EOs as novel types of active food packaging. Antimicrobial food packaging is one of the most promising kinds of active packaging, and acts to reduce, inhibit, or retard any microorganism growth that could contaminate packaged food items.
      Citation: Gels
      PubDate: 2022-05-24
      DOI: 10.3390/gels8060327
      Issue No: Vol. 8, No. 6 (2022)
  • Gels, Vol. 8, Pages 328: Hydrogels for Exosome Delivery in Biomedical

    • Authors: Yaxin Xie, Qiuyue Guan, Jiusi Guo, Yilin Chen, Yijia Yin, Xianglong Han
      First page: 328
      Abstract: Hydrogels, which are hydrophilic polymer networks, have attracted great attention, and significant advances in their biological and biomedical applications, such as for drug delivery, tissue engineering, and models for medical studies, have been made. Due to their similarity in physiological structure, hydrogels are highly compatible with extracellular matrices and biological tissues and can be used as both carriers and matrices to encapsulate cellular secretions. As small extracellular vesicles secreted by nearly all mammalian cells to mediate cell–cell interactions, exosomes play very important roles in therapeutic approaches and disease diagnosis. To maintain their biological activity and achieve controlled release, a strategy that embeds exosomes in hydrogels as a composite system has been focused on in recent studies. Therefore, this review aims to provide a thorough overview of the use of composite hydrogels for embedding exosomes in medical applications, including the resources for making hydrogels and the properties of hydrogels, and strategies for their combination with exosomes.
      Citation: Gels
      PubDate: 2022-05-24
      DOI: 10.3390/gels8060328
      Issue No: Vol. 8, No. 6 (2022)
  • Gels, Vol. 8, Pages 329: Nanoparticle-Containing Wound Dressing:
           Antimicrobial and Healing Effects

    • Authors: Pavel Yudaev, Yaroslav Mezhuev, Evgeniy Chistyakov
      First page: 329
      Abstract: The dressings containing nanoparticles of metals and metal oxides are promising types of materials for wound repair. In such dressings, biocompatible and nontoxic hydrophilic polymers are used as a matrix. In the present review, we take a look at the anti-microbial effect of the nanoparticle-modified wound dressings against various microorganisms and evaluate their healing action. A detailed analysis of 31 sources published in 2021 and 2022 was performed. Furthermore, a trend for development of modern antibacterial wound-healing nanomaterials was shown as exemplified in publications starting from 2018. The review may be helpful for researchers working in the areas of biotechnology, medicine, epidemiology, material science and other fields aimed at the improvement of the quality of life.
      Citation: Gels
      PubDate: 2022-05-24
      DOI: 10.3390/gels8060329
      Issue No: Vol. 8, No. 6 (2022)
  • Gels, Vol. 8, Pages 330: Development of Bigels Based on Date Palm-Derived
           Cellulose Nanocrystal-Reinforced Guar Gum Hydrogel and Sesame
           Oil/Candelilla Wax Oleogel as Delivery Vehicles for Moxifloxacin

    • Authors: Hamid M. Shaikh, Arfat Anis, Anesh Manjaly Poulose, Niyaz Ahamad Madhar, Saeed M. Al-Zahrani
      First page: 330
      Abstract: Bigels are biphasic semisolid systems that have been explored as delivery vehicles in the food and pharmaceutical industries. These formulations are highly stable and have a longer shelf-life than emulsions. Similarly, cellulose-based hydrogels are considered to be ideal for these formulations due to their biocompatibility and flexibility to mold into various shapes. Accordingly, in the present study, the properties of an optimized guar gum hydrogel and sesame oil/candelilla wax oleogel-based bigel were tailored using date palm-derived cellulose nanocrystals (dp-CNC). These bigels were then explored as carriers for the bioactive molecule moxifloxacin hydrochloride (MH). The preparation of the bigels was achieved by mixing guar gum hydrogel and sesame oil/candelilla wax oleogel. Polarizing microscopy suggested the formation of the hydrogel-in-oleogel type of bigels. An alteration in the dp-CNC content affected the size distribution of the hydrogel phase within the oleogel phase. The colorimetry studies revealed the yellowish-white color of the samples. There were no significant changes in the FTIR functional group positions even after the addition of dp-CNC. In general, the incorporation of dp-CNC resulted in a decrease in the impedance values, except BG3 that had 15 mg dp-CNC in 20 g bigel. The BG3 formulation showed the highest firmness and fluidity. The release of MH from the bigels was quasi-Fickian diffusion mediated. BG3 showed the highest release of the drug. In summary, dp-CNC can be used as a novel reinforcing agent for bigels.
      Citation: Gels
      PubDate: 2022-05-24
      DOI: 10.3390/gels8060330
      Issue No: Vol. 8, No. 6 (2022)
  • Gels, Vol. 8, Pages 331: Anti-Freezing, Non-Drying, Localized Stiffening,
           and Shape-Morphing Organohydrogels

    • Authors: Jiayan Shen, Shutong Du, Ziyao Xu, Tiansheng Gan, Stephan Handschuh-Wang, Xueli Zhang
      First page: 331
      Abstract: Artificial shape-morphing hydrogels are emerging toward various applications, spanning from electronic skins to healthcare. However, the low freezing and drying tolerance of hydrogels hinder their practical applications in challenging environments, such as subzero temperatures and arid conditions. Herein, we report on a shape-morphing system of tough organohydrogels enabled by the spatially encoded rigid structures and its applications in conformal packaging of “island–bridge” stretchable electronics. To validate this method, programmable shape morphing of Fe (III) ion-stiffened Ca-alginate/polyacrylamide (PAAm) tough organohydrogels down to −50 °C, with long-term preservation of their 3D shapes at arid or even vacuum conditions, was successfully demonstrated, respectively. To further illustrate the potency of this approach, the as-made organohydrogels were employed as a material for the conformal packaging of non-stretchable rigid electronic components and highly stretchable liquid metal (galinstan) conductors, forming a so-called “island–bridge” stretchable circuit. The conformal packaging well addresses the mechanical mismatch between components with different elastic moduli. As such, the as-made stretchable shape-morphing device exhibits a remarkably high mechanical durability that can withstand strains as high as 1000% and possesses long-term stability required for applications under challenging conditions.
      Citation: Gels
      PubDate: 2022-05-25
      DOI: 10.3390/gels8060331
      Issue No: Vol. 8, No. 6 (2022)
  • Gels, Vol. 8, Pages 332: Self-Assembled Peptide Habitats to Model Tumor

    • Authors: Noora Al Balushi, Mitchell Boyd-Moss, Rasika M. Samarasinghe, Aaqil Rifai, Stephanie J. Franks, Kate Firipis, Benjamin M. Long, Ian A. Darby, David R. Nisbet, Dodie Pouniotis, Richard J. Williams
      First page: 332
      Abstract: Metastatic tumours are complex ecosystems; a community of multiple cell types, including cancerous cells, fibroblasts, and immune cells that exist within a supportive and specific microenvironment. The interplay of these cells, together with tissue specific chemical, structural and temporal signals within a three-dimensional (3D) habitat, direct tumour cell behavior, a subtlety that can be easily lost in 2D tissue culture. Here, we investigate a significantly improved tool, consisting of a novel matrix of functionally programmed peptide sequences, self-assembled into a scaffold to enable the growth and the migration of multicellular lung tumour spheroids, as proof-of-concept. This 3D functional model aims to mimic the biological, chemical, and contextual cues of an in vivo tumor more closely than a typically used, unstructured hydrogel, allowing spatial and temporal activity modelling. This approach shows promise as a cancer model, enhancing current understandings of how tumours progress and spread over time within their microenvironment.
      Citation: Gels
      PubDate: 2022-05-25
      DOI: 10.3390/gels8060332
      Issue No: Vol. 8, No. 6 (2022)
  • Gels, Vol. 8, Pages 333: Heat Treatment of Geopolymer Samples Obtained by
           Varying Concentration of Sodium Hydroxide as Constituent of Alkali

    • Authors: Ljiljana Kljajević, Miloš Nenadović, Marija Ivanović, Dušan Bučevac, Miljana Mirković, Nataša Mladenović Nikolić, Snežana Nenadović
      First page: 333
      Abstract: In this paper, raw natural metakaolin (MK, Serbia) clay was used as a starting material for the synthesis of geopolymers for thermal treatment. Metakaolin was obtained by calcination of kaolin at 750 °C for 1 h while geopolymer samples were calcined at 900 °C, which is the key transition temperature. Metakaolin was activated by a solution of NaOH of various concentrations and sodium silicate. During the controlled heat treatment, the geopolymer samples began to melt slightly and coagulate locally. The high-temperature exposure of geopolymer samples (900 °C) caused a significant reduction in oxygen, and even more sodium, which led to the formation of a complex porous structure. As the concentration of NaOH (6 mol dm−3 and 8 mol dm−3) increased, new semi-crystalline phases of nepheline and sanidine were formed. Thermal properties were increasingly used to better understand and improve the properties of geopolymers at high temperatures. Temperature changes were monitored by simultaneous use of thermogravimetric analysis (TGA) and differential thermal analysis (DTA). The loss of mass of the investigated samples at 900 °C was in the range of 8–16%. Thermal treatment of geopolymers at 900 °C did not have much effect on the change in compressive strength of investigated samples. The results of thermal treatment of geopolymers at 900 °C showed that this is approximately the temperature at which the structure of the geopolymer turns into a ceramic-like structure. All investigated properties of the geopolymers are closely connected to the precursors and the constituents of the geopolymers.
      Citation: Gels
      PubDate: 2022-05-26
      DOI: 10.3390/gels8060333
      Issue No: Vol. 8, No. 6 (2022)
  • Gels, Vol. 8, Pages 334: Insights into the Role of Biopolymer-Based
           Xerogels in Biomedical Applications

    • Authors: H. P. S. Abdul Khalil, Esam Bashir Yahya, Husnul Azan Tajarudin, Venugopal Balakrishnan, Halimatuddahliana Nasution
      First page: 334
      Abstract: Xerogels are advanced, functional, porous materials consisting of ambient, dried, cross-linked polymeric networks. They possess characteristics such as high porosity, great surface area, and an affordable preparation route; they can be prepared from several organic and inorganic precursors for numerous applications. Owing to their desired properties, these materials were found to be suitable for several medical and biomedical applications; the high drug-loading capacity of xerogels and their ability to maintain sustained drug release make them highly desirable for drug delivery applications. As biopolymers and chemical-free materials, they have been also utilized in tissue engineering and regenerative medicine due to their high biocompatibility, non-immunogenicity, and non-cytotoxicity. Biopolymers have the ability to interact, cross-link, and/or trap several active agents, such as antibiotic or natural antimicrobial substances, which is useful in wound dressing and healing applications, and they can also be used to trap antibodies, enzymes, and cells for biosensing and monitoring applications. This review presents, for the first time, an introduction to biopolymeric xerogels, their fabrication approach, and their properties. We present the biological properties that make these materials suitable for many biomedical applications and discuss the most recent works regarding their applications, including drug delivery, wound healing and dressing, tissue scaffolding, and biosensing.
      Citation: Gels
      PubDate: 2022-05-29
      DOI: 10.3390/gels8060334
      Issue No: Vol. 8, No. 6 (2022)
  • Gels, Vol. 8, Pages 335: Fabrication of Ethosomes Containing Tocopherol
           Acetate to Enhance Transdermal Permeation: In Vitro and Ex Vivo

    • Authors: Naheed Akhtar, Naveed Akhtar, Farid Menaa, Walaa Alharbi, Fatima Saad Salem Alaryani, Ali Musfer Alqahtani, Faizan Ahmad
      First page: 335
      Abstract: Background: Tocopherol acetate (TA) is known as a skin moisturizing and photoprotective agent. One major drawback with tocopherol and its derivatives remains its limited stability. Aim: To develop highly stable TA-containing ethosomal gel (TAEG) as an advanced dosage form. Methods: A cold method technique was used to produce the ethosomes. An in vitro evaluation of viscosity, conductivity, and pH stability was carried out for three months. An in vitro physical characterization of the nanoparticles (NPs) that included particle size (PS), zeta potential (ZP), transmission electron microscopy (TEM), and Fourier-transform infrared (FTIR) spectroscopy analysis was then performed. Organoleptic evaluation, thermostability at 8 °C, 25 °C, 40 °C and 40 °C ± 75% RH, pH, conductivity, viscosity, and spreadability measurements were also performed in vitro for three months. An ex vivo permeation study was performed in phosphate-buffered solution (1× PBS; pH 5.5 or pH 7.4) at 37 ± 0.2 °C by using rat abdominal skin and the Franz diffusion cell method. The data of three independent experiments were expressed as mean ± SD. A two-way ANOVA was applied to compare data on TAEG versus TA control gel (TACG). Results: PS of the ethosomes was in the range of 144–289 nm. A total of nine formulations were developed. Optimized TAEG formulation (TA-5) was selected based on the highest entrapment efficiency (EE) of 99.71%, while the stability, the PS, and the uniformity-based polydispersity index (PDI) were also among the best. TA-5 exhibited smooth spherical ethosomal NPs with PS of 200.6 nm, ZP value of −18.6 V, and PDI of 0.465. Stability data obtained for TA-5 in terms of rheology, conductivity, and pH presented no significant change (p > 0.05) during the entire study duration. Rheological studies indicated that TA-5 followed a non-Newtonian behavior of shear thinning system. The ex vivo drug permeation was 44.55 ± 0.01% in TA-5 and the drug retention in skin was 51.20%, which was significantly higher than TACG as observed after 24 h permeation study (p < 0.05). Conclusions: The newly developed TAEG formulation appears promising to enhance the effectivity of TA and its topical application.
      Citation: Gels
      PubDate: 2022-05-30
      DOI: 10.3390/gels8060335
      Issue No: Vol. 8, No. 6 (2022)
  • Gels, Vol. 8, Pages 336: Tissue Adhesive, Conductive, and Injectable
           Cellulose Hydrogel Ink for On-Skin Direct Writing of Electronics

    • Authors: Subin Jin, Yewon Kim, Donghee Son, Mikyung Shin
      First page: 336
      Abstract: Flexible and soft bioelectronics used on skin tissue have attracted attention for the monitoring of human health. In addition to typical metal-based rigid electronics, soft polymeric materials, particularly conductive hydrogels, have been actively developed to fabricate biocompatible electrical circuits with a mechanical modulus similar to biological tissues. Although such conductive hydrogels can be wearable or implantable in vivo without any tissue damage, there are still challenges to directly writing complex circuits on the skin due to its low tissue adhesion and heterogeneous mechanical properties. Herein, we report cellulose-based conductive hydrogel inks exhibiting strong tissue adhesion and injectability for further on-skin direct printing. The hydrogels consisting of carboxymethyl cellulose, tannic acid, and metal ions (e.g., HAuCl4) were crosslinked via multiple hydrogen bonds between the cellulose backbone and tannic acid and metal-phenol coordinate network. Owing to this reversible non-covalent crosslinking, the hydrogels showed self-healing properties and reversible conductivity under cyclic strain from 0 to 400%, as well as printability on the skin tissue. In particular, the on-skin electronic circuit printed using the hydrogel ink maintained a continuous electrical flow under skin deformation, such as bending and twisting, and at high relative humidity of 90%. These printable and conductive hydrogels are promising for implementing structurally complicated bioelectronics and wearable textiles.
      Citation: Gels
      PubDate: 2022-05-30
      DOI: 10.3390/gels8060336
      Issue No: Vol. 8, No. 6 (2022)
  • Gels, Vol. 8, Pages 337: Poly(curcumin β-amino ester)-Based Tablet
           Formulation for a Sustained Release of Curcumin

    • Authors: Vinod S. Patil, Benjamin C. Burdette, J. Zach Hilt, Douglass S. Kalika, Thomas D. Dziubla
      First page: 337
      Abstract: Oral drug delivery remains the most common and well tolerated method for drug administration. However, its applicability is often limited due to low drug solubility and stability. One approach to overcome the solubility and stability limitations is the use of amorphous polymeric prodrug formulations, such as poly(β-amino ester) (PBAE). PBAE hydrogels, which are biodegradable and pH responsive, have shown promising results for the controlled release of drugs by improving the stability and increasing the solubility of these drugs. In this work, we have evaluated the potential use of PBAE prodrugs in an oral tablet formulation, studying their sustained drug release potential and storage stability. Curcumin, a low solubility, low stability antioxidant drug was used as a model compound. Poly(curcumin β-amino ester) (PCBAE), a crosslinked amorphous network, was synthesized by a previously published method using a commercial diacrylate and a primary diamine, in combination with acrylate-functionalized curcumin. PCBAE-based tablets were made and exhibited a sustained release for 16 h, following the hydrolytic degradation of PCBAE particles into native curcumin. In addition to the release studies, preliminary storage stability was assessed using standard and accelerated stability conditions. As PCBAE degradation is hydrolysis driven, tablet stability was found to be sensitive to moisture.
      Citation: Gels
      PubDate: 2022-05-30
      DOI: 10.3390/gels8060337
      Issue No: Vol. 8, No. 6 (2022)
  • Gels, Vol. 8, Pages 338: A Temperature-Sensitive Polymeric Rheology
           Modifier Used in Water-Based Drilling Fluid for Deepwater Drilling

    • Authors: Zhongyi Wang, Jinsheng Sun, Kun Zhang, Kaihe Lv, Xianbin Huang, Jintang Wang, Ren Wang, Xu Meng
      First page: 338
      Abstract: Rheology modifiers are essential for the flat rheology of water-based drilling fluids in deepwater. The low temperature thickening of deepwater water-based drilling fluids results in dramatic rheological changes in the 20–30 °C range. To address such problems, NIPAM with a self-polymerized product LCST of 32–35 °C was selected as the main body for synthesis. While introducing the hydrophilic monomer AM to enhance the thickening properties, the hydrophobic monomer BA was selected to reduce the LCST of the product. In this paper, a temperature-sensitive polymeric rheology modifier (PNBAM) was synthesized by emulsion polymerization using N-isopropyl acrylamide, acrylamide, and butyl acrylate as monomers. The PNBAM was characterized using infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), and nuclear magnetic resonance hydrogen spectroscopy (NMR). The rheological properties, temperature resistance, and salt resistance of PNBAM in the base fluid (BF) were tested. The performance of PNBAM in the drilling fluid system was also evaluated, and a water-based drilling fluid system of flat rheology for deepwater was formulated. The rheological modification mechanism of PNBAM was analyzed by turbidity analysis, particle size analysis, and zeta analysis. Experimental results show that PNBAM has good rheological properties. PNBAM is temperature resistant to 150 °C, salt-resistant to 30 wt%, and calcium resistant to 1.0 wt%. PNBAM also has good flat rheology characteristics in drilling fluid systems: AV4°C:AV25°C = 1.27, PV4°C:PV25°C = 1.19. Mechanistic analysis showed that the LCST (Lower Critical Solution Temperature) of 0.2 wt% PNBAM in an aqueous solution was 31 °C. Through changes in hydrogen bonding forces with water, PNBAM can regulate its hydrophilic and hydrophobic properties before and after LCST, which thus assists BF to achieve a flat rheological effect. In summary, the temperature-sensitive effect of PNBAM has the property of enhancing with increasing temperature. While the tackifying effect of conventional rheology modifiers diminishes with increasing temperature, the temperature-sensitive effect of PNBAM gives it an enhanced thickening effect with increasing temperature, making it a more novel rheology modifier compared to conventional treatment additives. After LCST, compared to conventional rheology modifiers (XC), PNBAM has a more pronounced thermo-thickening effect, improving the main rheological parameters of BF by more than 100% or even up to 200% (XC less than 50%). This contributes to the flat rheology of drilling fluids. PNBAM has good application prospects and serves as a good reference for the development of other rheology modifiers.
      Citation: Gels
      PubDate: 2022-05-30
      DOI: 10.3390/gels8060338
      Issue No: Vol. 8, No. 6 (2022)
  • Gels, Vol. 8, Pages 339: Dual-Responsive Photonic Crystal Sensors Based on
           Physical Crossing-Linking SF-PNIPAM Dual-Crosslinked Hydrogel

    • Authors: Wenxiang Zheng, Xiaolu Cai, Dan Yan, Ghulam Murtaza, Zihui Meng, Lili Qiu
      First page: 339
      Abstract: Flexible wearable materials have frequently been used in drug delivery, healthcare monitoring, and wearable sensors for decades. As a novel type of artificially designed functional material, photonic crystals (PCs) are sensitive to the changes in the external environment and stimuli signals. However, the rigidity of the PCs limits their application in the field of biometric and optical sensors. This study selects silk fibroin (SF) and poly-N-isopropylacrylamide (PNIPAM) as principal components to prepare the hydrogel with the physical crosslinking agent lithium silicate (LMSH) and is then integrated with PCs to obtain the SF-PNIPAM dual-crosslinked nanocomposite for temperature and strain sensing. The structural colors of the PCs change from blue to orange-red by the variation in temperature or strain. The visual temperature-sensing and adhesion properties enable the SF-PNIPAM dual-crosslinked nanocomposite to be directly attached to the skin in order to monitor the real-time dynamic of human temperature. Based on its excellent optical properties and biocompatibility, the SF-PNIPAM dual-crosslinked nanocomposite can be applied to the field of visual biosensing, wearable display devices, and wound dressing materials.
      Citation: Gels
      PubDate: 2022-05-30
      DOI: 10.3390/gels8060339
      Issue No: Vol. 8, No. 6 (2022)
  • Gels, Vol. 8, Pages 340: Advanced CNC/PEG/PDMAA Semi-IPN Hydrogel for Drug
           Delivery Management in Wound Healing

    • Authors: Samia Afrin, Md. Shahruzzaman, Papia Haque, Md. Sazedul Islam, Shafiul Hossain, Taslim Ur Rashid, Tanvir Ahmed, Makoto Takafuji, Mohammed Mizanur Rahman
      First page: 340
      Abstract: A Semi Interpenetrating Polymer Network (semi-IPN) hydrogel was prepared and loaded with an antibiotic drug, gentamicin, to investigate the wound healing activity of this system. The semi-IPN hydrogel was synthesized by combining natural polymer cellulose nanocrystal (CNC) and synthetic polymer polyethylene glycol (PEG) and poly (N,N′-dimethyl acrylamide) (PDMAA), which was initially added as a monomer dimethyl acrylamide (DMAA). CNC was prepared from locally obtained jute fibers, dispersed in a PEG-NaOH solvent system and then mixed with monomer DMAA, where polymerization was initiated by an initiator potassium persulphate (KPS) and cross-linked by N,N′-methylenebisacrylamide (NMBA). The size, morphology, biocompatibility, antimicrobial activity, thermal and swelling properties of the hydrogel were investigated by different characterization techniques. The biocompatibility of the hydrogel was confirmed by cytotoxicity analysis, which showed >95% survival of the BHK-21, Vero cell line. The drug loaded hydrogel showed antimicrobial property by forming 25 and 23 mm zone of inhibition against Staphylococcus aureus (gram-positive) and Escherichia coli (gram-negative) bacteria, respectively, in antimicrobial analysis. At pH 5.5, 76% of the drug was released from the hydrogel within 72 h, as observed in an in vitro drug release profile. In an in vivo test, the healing efficiency of the drug loaded hydrogel was examined on a mice model with dorsal wounds. Complete healing of the wound without any scar formation was achieved in 12 days, which revealed excellent wound healing properties of the prepared drug loaded semi-IPN hydrogel. These results showed the relevance of such a system in the rapid healing of acute wounds.
      Citation: Gels
      PubDate: 2022-05-30
      DOI: 10.3390/gels8060340
      Issue No: Vol. 8, No. 6 (2022)
  • Gels, Vol. 8, Pages 341: Effect of Municipal Solid Waste Incineration Fly
           Ash on the Mechanical Properties and Microstructure of Geopolymer Concrete

    • Authors: Mengya Niu, Peng Zhang, Jinjun Guo, Jia Wang
      First page: 341
      Abstract: Geopolymers are environmentally friendly materials made from industrial solid waste with high silicon and aluminum contents, and municipal solid waste incineration fly ash (MFA) contains active ingredients such as Si, Al and Ca. According to this fact, a green and low-carbon geopolymer concrete was prepared using MFA as a partial replacement for metakaolin in this study. The mechanical properties of the MFA geopolymer concrete (MFA-GPC) were investigated through a series of experiments, including a compressive strength test, splitting tensile strength test, elastic modulus test and three-point bending fracture test. The effect of the MFA replacement ratio on the microstructure of MFA-GPC was investigated by SEM test, XRD analysis and FTIR analysis. MFA replacement ratios incorporated in GPC were 5%, 10%, 15%, 20%, 25%, 30%, 35% and 40% by replacing metakaolin with equal quality in this study. In addition, toxic leaching tests of MFA and MFA-GPC were performed by ICP-AES to evaluate the safety of MFA-GPC. The results indicated that the mechanical properties of MFA-GPC decreased with the increase of the MFA replacement ratio. Compared with the reference group of GPC without MFA, the maximum reduction rates of the cubic compressive strength, splitting tensile strength, axial compressive strength, elastic modulus, initiation fracture toughness, unstable fracture toughness and fracture energy of MFA-GPC were 83%, 81%, 78%, 93%, 77%, 73% and 61%, respectively. The microstructure of MFA-GPC was porous and carbonized; however, the type of hydrated gel products was still a calcium silicoaluminate-based silicoaluminate gel. Moreover, the leaching content of heavy metals from MFA-GPC was lower than that of the standard limit. In general, the appropriate amount of MFA can be used to prepare GPC, and its mechanical properties can meet the engineering requirements, but the amount of MFA should not be too high.
      Citation: Gels
      PubDate: 2022-05-30
      DOI: 10.3390/gels8060341
      Issue No: Vol. 8, No. 6 (2022)
  • Gels, Vol. 8, Pages 342: Intranasal Delivery of Darunavir-Loaded
           Mucoadhesive In Situ Gel: Experimental Design, In Vitro Evaluation, and
           Pharmacokinetic Studies

    • Authors: Anroop B. Nair, Sunita Chaudhary, Hiral Shah, Shery Jacob, Vivek Mewada, Pottathil Shinu, Bandar Aldhubiab, Nagaraja Sreeharsha, Katharigatta N. Venugopala, Mahesh Attimarad, Jigar Shah
      First page: 342
      Abstract: The clinical efficacy of antiretroviral therapy in NeuroAIDS is primarily limited by the low perfusion of the drug to the brain. The objective of the current investigation was to design and develop an in situ mucoadhesive gel loaded with darunavir to assess the feasibility of brain targeting through the intranasal route. Preliminary batches (F1–F9) were prepared and evaluated for various pharmaceutical characteristics. A full factorial design of the experiment was applied to optimize and assess the effect of two influencing variables (Carbopol 934P (X1) and Poloxamer 407 (X2)) on the response effects (gelation temperature (Y1) and % drug release (Y2) at 8 h). The data demonstrate that both influencing variables affect the response variables significantly (p < 0.05). The optimized formulation (F7) exhibited favorable rheological properties, adequate mucoadhesion, sustained drug release, and greater permeation across the nasal mucosa. An in vitro ciliotoxicity study confirms the nontoxicity of the optimized in situ gel (D7) on the nasal mucosa. An in vivo pharmacokinetic study in rats was performed to assess drug targeting to the brain following the nasal application of the selected in situ gel (D7). Significantly higher (p < 0.0001) Cmax (~4-fold) and AUC0-α (~3.5-fold) values were noticed in the brain after nasal application, as compared to the intravenous route. However, less systemic exposure to darunavir was noticed with nasal therapy, which confirms the low absorption of the drug into the central compartment. Overall, the data here demonstrate that the optimized in situ mucoadhesive nasal gel is effective in targeting darunavir to the brain by the nasal route and could be a viable option for the treatment of NeuroAIDS.
      Citation: Gels
      PubDate: 2022-05-30
      DOI: 10.3390/gels8060342
      Issue No: Vol. 8, No. 6 (2022)
  • Gels, Vol. 8, Pages 343: Highly Efficient Adsorption of Heavy Metals and
           Cationic Dyes by Smart Functionalized Sodium Alginate Hydrogels

    • Authors: Tianzhu Shi, Zhengfeng Xie, Xinliang Mo, Yulong Feng, Tao Peng, Dandan Song
      First page: 343
      Abstract: In this paper, functionalized sodium alginate hydrogel (FSAH) was prepared to efficiently adsorb heavy metals and dyes. Hydrazide-functionalized sodium alginate (SA) prepared hydrazone groups to selectively capture heavy metals (Pb2+, Cd2+, and Cu2+), and another functional group (dopamine grafting), serves as sites for adsorption methylene blue (MB), malachite green (MG), crystal violet (CV). Thermodynamic parameters of adsorption indicated that the adsorption process is endothermic and spontaneous. The heavy metals adsorption by FSAH was physical adsorption mainly due to ΔHθ < 40 kJ/mol, and the adsorption of cationic dyes fitted with the Langmuir models, which indicated that the monolayer adsorption is dominated by hydrogen bonds, electrostatic interactions, and π-π interactions. Moreover, the adsorption efficiency maintained above 70% after five adsorption-desorption cycles. To sum up, FSAH has great application prospect.
      Citation: Gels
      PubDate: 2022-05-31
      DOI: 10.3390/gels8060343
      Issue No: Vol. 8, No. 6 (2022)
  • Gels, Vol. 8, Pages 344: Influence of Ceria Addition on Crystallization
           Behavior and Properties of Mesoporous Bioactive Glasses in the

    • Authors: Elena Maria Anghel, Simona Petrescu, Oana Catalina Mocioiu, Jeanina Pandele Cusu, Irina Atkinson
      First page: 344
      Abstract: Knowledge of the crystallization stability of bioactive glasses (BGs) is a key factor in developing porous scaffolds for hard tissue engineering. Thus, the crystallization behavior of three mesoporous bioactive glasses (MBGs) in the 70SiO2-(26-x)CaO-4P2O5-xCeO2 system (x stands for 0, 1 and 5 mol. %, namely MBG(0/1/5)Ce), prepared using the sol–gel method coupled with the evaporation-induced self-assembly method (EISA), was studied. A thermal analysis of the multiple-component crystallization exotherms from the DSC scans was performed using the Kissinger method. The main crystalline phases of Ca5(PO4)2.823(CO3)0.22O, CaSiO3 and CeO2 were confirmed to triggered by the devitrification of the MBG with 5% CeO2, MBG5Ce. Increasing the ceria content triggered a reduction in the first crystallization temperature while ceria segregation took place. The amount of segregated ceria of the annealed MBG5Ce decreased as the annealing temperature increased. The optimum processing temperature range to avoid the crystallization of the MBG(0/1/5)Ce powders was established.
      Citation: Gels
      PubDate: 2022-05-31
      DOI: 10.3390/gels8060344
      Issue No: Vol. 8, No. 6 (2022)
  • Gels, Vol. 8, Pages 345: A Novel Method for the Preparation of Poly
           (Acrylamide−co−Acrylonitrile) Upper Critical Solution
           Temperature Thermosensitive Hydrogel by the Partial Dehydration of
           Acrylamide Grafted Polypropylene Sheets

    • Authors: Yi Ling, Liuyuchen Chen, Mingjun Huang, Cheng Zhou, Liming Yang, Hejingying Niu, Li Su, Yuejiao Yang, Rogério P. Pirraco, Rui L. Reis, Jie Chen
      First page: 345
      Abstract: In an attempt to find a potential application of cell culture harvesting, a novel method for the preparation of an upper critical solution temperature (UCST) thermosensitive hydrogel was studied. An electron accelerator was used as the electron beam (EB) radiation source, and acrylamide (AAm) was first grafted onto the pre−irradiated polypropylene (PP) sheet. Then, the grafting layer of poly (acrylamide−co−acrylonitrile) (P (AAm−co−AN)) was obtained by the partial dehydration of the acylamino group into the cyano group in the solution mixture of sulfoxide chloride (SOCl2) and dimethyl formamide (DMF). The effects of the absorbed dose, AAm concentration, reaction time, and temperature on the degree of grafting were studied, respectively. The effect of the SOCl2 concentration on the conversion degree of the cyano group from the acylamino group was studied, followed by the temperature of the UCST. The UCST properties of the grafted samples with P (AAm−co−AN) were studied by quartz crystal microbalance (QCM) and atomic force microscope (AFM), respectively. The cytotoxicities of the hydrogels against cells were verified by CCK−8 studies.
      Citation: Gels
      PubDate: 2022-05-31
      DOI: 10.3390/gels8060345
      Issue No: Vol. 8, No. 6 (2022)
  • Gels, Vol. 8, Pages 346: A Study on the Cement Gel Formation Process
           during the Creation of Nanomodified High-Performance Concrete Based on

    • Authors: Alexey N. Beskopylny, Sergey A. Stel’makh, Evgenii M. Shcherban’, Levon R. Mailyan, Besarion Meskhi, Valery Varavka, Nikita Beskopylny, Diana El’shaeva
      First page: 346
      Abstract: One of the most science-intensive and developing areas is nano-modified concrete. Its characteristics of high-strength, high density, and improved structure, which is not only important at the stage of monitoring their performance, but also at the manufacturing stage, characterize high-performance concrete. The aim of this study is to obtain new theoretical knowledge and experimental-applied dependencies arising from the “composition–microstructure–properties” ratio of high-strength concretes with a nano-modifying additive of the most effective type. The methods of laser granulometry and electron microscopy are applied. The existing concepts from the point of view of theory and practice about the processes of cement gel formation during the creation of nano-modified high-strength concretes with nano-modifying additives are developed. The most rational mode of the nano-modification of high-strength concretes is substantiated as follows: microsilica ground to nanosilica within 12 h. A complex nano-modifier containing nanosilica, superplasticizer, hyperplasticizer, and sodium sulfate was developed. The most effective combination of the four considered factors are: the content of nanosilica is 4% by weight of cement; the content of the superplasticizer additive is 1.4% by weight of cement; the content of the hyperplasticizer additive is 3% by weight of cement; and the water–cement ratio—0.33. The maximum difference of the strength characteristics in comparison with other combinations ranged from 45% to 57%.
      Citation: Gels
      PubDate: 2022-06-02
      DOI: 10.3390/gels8060346
      Issue No: Vol. 8, No. 6 (2022)
  • Gels, Vol. 8, Pages 347: Optical Properties and Upconversion Luminescence
           of BaTiO3 Xerogel Structures Doped with Erbium and Ytterbium

    • Authors: Ekaterina I. Lashkovskaya, Nikolai V. Gaponenko, Margarita V. Stepikhova, Artem N. Yablonskiy, Boris A. Andreev, Vadim D. Zhivulko, Alexander V. Mudryi, Igor L. Martynov, Alexander A. Chistyakov, Nikolai I. Kargin, Vladimir A. Labunov, Tamara F. Raichenok, Sergey A. Tikhomirov, Victor Yu. Timoshenko
      First page: 347
      Abstract: Erbium upconversion (UC) photoluminescence (PL) from sol-gel derived barium titanate (BaTiO3:Er) xerogel structures fabricated on silicon, glass or fused silica substrates has been studied. Under continuous-wave excitation at 980 nm and nanosecond pulsed excitation at 980 and 1540 nm, the fabricated structures demonstrate room temperature PL with several bands at 410, 523, 546, 658, 800 and 830 nm, corresponding to the 2H9/2 → 4I15/2, 2H11/2 → 4I15/2, 4S3/2 → 4I15/2, 4F9/2→ 4I15/2 and 4I9/2→ 4I15/2 transitions of Er3+ ions. The intensity of erbium UC PL increases when an additional macroporous layer of strontium titanate is used beneath the BaTiO3 xerogel layer. It is also enhanced in BaTiO3 xerogel films codoped with erbium and ytterbium (BaTiO3:(Er,Yb)). For the latter, a redistribution of the intensity of the PL bands is observed depending on the excitation conditions. A multilayer BaTiO3:(Er,Yb)/SiO2 microcavity structure was formed on a fused silica substrate with a cavity mode in the range of 650–680 nm corresponding to one of the UC PL bands of Er3+ ions. The obtained cavity structure annealed at 450 °C provides tuning of the cavity mode by 10 nm in the temperature range from 20 °C to 130 °C. Photonic application of BaTiO3 xerogel structures doped with lanthanides is discussed.
      Citation: Gels
      PubDate: 2022-06-02
      DOI: 10.3390/gels8060347
      Issue No: Vol. 8, No. 6 (2022)
  • Gels, Vol. 8, Pages 348: The Influence of the Hydroxyl Type on
           Crosslinking Process in Cyclodextrin Based Polyurethane Networks

    • Authors: Cristian Peptu, Alexandra-Diana Diaconu, Maricel Danu, Catalina A. Peptu, Mariana Cristea, Valeria Harabagiu
      First page: 348
      Abstract: The influence of the hydroxyl groups (OH) type on the polyaddition processes of isocyanates represents a critical approach for the design of multicomponent polyurethane systems. Herein, to prove the effect of hydroxyl nature on both the isocyanate-OH polyaddition reactions and the structure/properties of the resulting networks, two structurally different cyclodextrins in terms of the primary and secondary groups’ ratio were analyzed, namely native β-cyclodextrin (CD) and its derivative esterified to the primary hydroxyl groups with oligolactide chains (CDLA). Thus, polyurethane hydrogels were prepared via the polyaddition of CD or CDLA to isophorone diisocyanate polyethylene glycol-based prepolymers (PEG-(NCOO)2). The degradable character of the materials was induced by intercalating oligolactide short sequences into the polymer chains composing the polymer network. In order to establish the influence of the OH type, the synthesis of polyurethane hydrogels was analyzed by a rheological investigation of the overall system reactivity. Materials properties such as swelling behavior, thermal properties and hydrolytic degradation were influenced by the reaction feed. Specifically, the presence of primary OH groups leads to more compact networks with similar water uptake, disregarding the CD content, while the predominance of secondary OH groups together with the presence of oligolactide spacers leads to the fine tuning of the water swelling properties.
      Citation: Gels
      PubDate: 2022-06-02
      DOI: 10.3390/gels8060348
      Issue No: Vol. 8, No. 6 (2022)
  • Gels, Vol. 8, Pages 349: Oleogels and Organogels: A Promising Tool for New

    • Authors: Miguel A. Cerqueira, Fabio Valoppi, Kunal Pal
      First page: 349
      Abstract: Growing awareness concerning human health and sustainability has been continually driving the need to change consumers’ habits and develop new bio-based and environmentally friendly materials that could be used in new product formulations [...]
      Citation: Gels
      PubDate: 2022-06-02
      DOI: 10.3390/gels8060349
      Issue No: Vol. 8, No. 6 (2022)
  • Gels, Vol. 8, Pages 350: Supramolecular Rings as Building Blocks for
           Stimuli-Responsive Materials

    • Authors: Hanna Traeger, Alyssa Ghielmetti, Yoshimitsu Sagara, Stephen Schrettl, Christoph Weder
      First page: 350
      Abstract: Stimuli-responsive polymers are of great interest due to their ability to translate changing environmental conditions into responses in defined materials. One possibility to impart such behavior is the incorporation of optically active molecules into a polymer host. Here, we describe how sensor molecules that consist of a π-extended benzothiadiazole emitter and a naphthalene diimide quencher can be exploited in this context. The two optically active entities were connected via different spacers and, thanks to attractive intramolecular interactions between them, the new sensor molecules assembled into cyclic structures in which the fluorescence was quenched by up to 43% when compared to solutions of the individual dyes. Detailed spectroscopic investigations of the sensor molecules in solution show that the extent of donor/acceptor interactions is influenced by various factors, including solvent polarity and ion concentration. The new sensor molecule was covalently incorporated into a polyurethane; the investigation of the optical characteristics in both the solid and solvent-swollen states indicates that a stimulus-induced formation of associated dye pairs is possible in polymeric materials. Indeed, a solvatochromic quenching effect similar to the behavior in solution was observed for solvent-swollen polymer samples, leading to an effective change of the green emission color of the dye to a yellow color.
      Citation: Gels
      PubDate: 2022-06-03
      DOI: 10.3390/gels8060350
      Issue No: Vol. 8, No. 6 (2022)
  • Gels, Vol. 8, Pages 351: Use of Betaine-Based Gel and Its Potential
           Application in Enhanced Oil Recovery

    • Authors: Yuman Wu, Jie Zhang, Sanbao Dong, Yongfei Li, Michal Slaný, Gang Chen
      First page: 351
      Abstract: In this paper, a betaine-based gel containing 2.0% erucamide propyl betaine (EAPB), 0.5% oleic acid amide propyl betaine (OAPB), and 0.1% KCl was prepared for use as a fracturing fluid. The performance evaluation showed that KCl may improve the temperature resistance and increase the viscosity of the optimized fracturing fluid. At 80 °C, the apparent viscosity of the viscoelastic surfactant (VES)-based fracturing fluid was approximately 50 mPa·s. Furthermore, the gel had high shear resistance, good viscosity stability, and high sand-carrying performance. After being sheared at 170 s−1 for 60 min, the reduction in viscosity was 13.6%. The viscosity of the gel was relatively stable at room temperature (27 °C) for one week. In a suspension containing 10% sand (particle size < 0.45 mm, density = 2.75 g cm−3), the settling velocity of proppant particles was 1.15 cm h−1. In addition, we detected that the critical micelle concentration of this gel was approximately 0.042 wt%. The viscosity could be reduced to <5 mPa·s at 60 °C within 1 h when 6.0% crude oil was present, and oil displacement experiments showed that the broken fracturing fluid can enhance the oil displacement rate up to 14.5%. This work may facilitate research on fracturing fluids and oil recovery.
      Citation: Gels
      PubDate: 2022-06-03
      DOI: 10.3390/gels8060351
      Issue No: Vol. 8, No. 6 (2022)
  • Gels, Vol. 8, Pages 352: Soft Movable Polymer Gel for Controlling Water
           Coning of Horizontal Well in Offshore Heavy Oil Cold Production

    • Authors: Jie Qu, Pan Wang, Qing You, Guang Zhao, Yongpeng Sun, Yifei Liu
      First page: 352
      Abstract: Horizontal well water coning in offshore fields is one of the most common causes of rapid declines in crude oil production and, even more critical, can lead to oil well shut down. The offshore Y oil field with a water cut of 94.7% urgently needs horizontal well water control. However, it is a challenge for polymer gels to meet the requirements of low-temperature (55 °C) gelation and mobility to control water in a wider range. This paper introduced a novel polymer gel cross-linked by hydrolyzed polyacrylamide and chromium acetate and phenolic resin for water coning control of a horizontal well. The detailed gelant formula and treatment method of water coning control for a horizontal well in an offshore field was established. The optimized gelant formula was 0.30~0.45% HPAM + 0.30~0.5% phenolic resin + 0.10~0.15% chromium acetate, with corresponding gelation time of 26~34 h at 55 °C. The results showed that this gel has a compact network structure and excellent creep property, and it can play an efficient water control role in the microscopic model. The thus-optimized gelants were successively injected with injection volumes of 500.0 m3. The displacement fluid was used to displace gelants into the lost zone away from the oil zone. Then, the formed gel can be worked as the chemical packer in the oil–water interface to control water coning after shutting in for 4 days of gelation. The oil-field monitoring data indicated that the oil rate increased from 9.2 m3/d to 20.0 m3/d, the average water cut decreased to 60~70% after treatment, and the cumulative oil production could obtain 1.035 × 104 t instead of 3.9 × 103 t.
      Citation: Gels
      PubDate: 2022-06-05
      DOI: 10.3390/gels8060352
      Issue No: Vol. 8, No. 6 (2022)
  • Gels, Vol. 8, Pages 353: Comprehensive Review of Polymer and Polymer Gel
           Treatments for Natural Gas-Related Conformance Control

    • Authors: Ali Al Brahim, Baojun Bai, Thomas Schuman
      First page: 353
      Abstract: Conformance problems often exist in natural gas-related activities, resulting in excessive water production from natural gas production wells and/or excessive natural gas production from oil production wells. Several mechanical and chemical solutions were reported in the literature to mitigate the conformance problems. Among the chemical solutions, two classes of materials, namely polymer gels and water-soluble polymers, have been mostly reported. These systems have been mainly reviewed in several studies for their applications as water shutoff treatments for oil production wells. Natural gas production wells exhibit different characteristics and have different properties which could impact the performance of the chemical solutions. However, there has not been any work done on reviewing the applications of these systems for the challenging natural gas-related shutoff treatments. This study provides a comprehensive review of the laboratory evaluation and field applications of these systems used for water control in natural gas production wells and gas shutoff in oil production wells, respectively. The first part of the paper reviews the in-situ polymer gel systems, where both organically and inorganically crosslinked systems are discussed. The second part presents the water-soluble polymers with a focus on their disproportionate permeability reduction feature for controlling water in gas production wells. The review paper provides insights into the reservoir conditions, treatment design and intervention, and the success rate of the systems applied. Furthermore, the outcomes of the paper will provide knowledge regarding the limitations of the existing technologies, current challenges, and potential paths forwards.
      Citation: Gels
      PubDate: 2022-06-05
      DOI: 10.3390/gels8060353
      Issue No: Vol. 8, No. 6 (2022)
  • Gels, Vol. 8, Pages 354: Novel Hydrocolloids Obtained from Mango
           (Mangifera indica) var. Hilaza: Chemical, Physicochemical,
           Techno-Functional, and Structural Characteristics

    • Authors: Ronald Marsiglia-Fuentes, Somaris E. Quintana, Luis A. García Zapateiro
      First page: 354
      Abstract: Background: Hydrocolloids are ingredients used to improve the technological properties of products; currently, there is a growing demand from the food industry and consumers to use natural ingredients and reduce the environmental impact. Methods: This work evaluated the effect of pH on hydrocolloid extraction from the pulp, seed, and peel of mango (Mangifera indica) var. hilaza and their chemical, physicochemical, techno-functional, and structural properties. Results: The main component of the hydrocolloid was the carbohydrates for pulp (22.59%) and peel (24.05%), and the protein for seed (21.48%) was corroborated by NIR spectra and associated with the technological and functional properties. The solubility increases with the temperature presenting values higher than 75% at 80 °C; the swelling index was higher than 30%, while the water holding capacity was higher in samples with higher carbohydrate content (110–121%). Moreover, a higher content of total phenolic compounds (21.61 ± 0.39–51.77 ± 2.48 mg GAE/g) and antioxidant activity (≥193.82 μMol Trolox/g) was obtained. The pH of extraction changes the color parameters and microstructural properties. Conclusions: Novel ingredients from mango pulp, seed, and peel at different pH levels have technological and functional properties that are potential use in the food industry as an alternative to the development of microstructural products.
      Citation: Gels
      PubDate: 2022-06-06
      DOI: 10.3390/gels8060354
      Issue No: Vol. 8, No. 6 (2022)
  • Gels, Vol. 8, Pages 355: The Characteristic of Insect Oil for a Potential
           Component of Oleogel and Its Application as a Solid Fat Replacer in

    • Authors: Doyoung Kim, Imkyung Oh
      First page: 355
      Abstract: The larvae of Tenebrio molitor, an edible insect, have recently attracted attention in the food industry as a protein supplement or future food material. However, despite more than 30% of the total weight being fat content, few studies have been conducted on the fat (oil) derived from Tenebrio molitor larvae (TM oil) and its food utilization. In this study, TM oil was extracted and its fatty acid composition and antioxidant activity were investigated. Then, the oleogels were prepared with TM oil and oleogelators (candelilla wax, carnauba wax, and beeswax) and their rheological and thermal properties were evaluated to elucidate their utilization as a solid fat replacer in cookies. In the results, TM oil contained 73.6% unsaturated fatty acids and showed a lower antioxidant activity than olive oil. Although the highest hardness was shown in oleogel with candelilla wax, the highest viscoelasticity above 50 °C was observed for oleogel with carnauba wax. The highest melting point was observed in carnauba oleogel. Lower peroxide values were observed in the oleogel samples than for TM oil, indicating that oleogelation of structuring oil improved the oxidative stability of TM oil. In addition, the shortening replacement with carnauba wax oleogel showed a desirable cookie quality in terms of spreadability and texture properties.
      Citation: Gels
      PubDate: 2022-06-06
      DOI: 10.3390/gels8060355
      Issue No: Vol. 8, No. 6 (2022)
  • Gels, Vol. 8, Pages 356: Self-Healing Materials-Based Electronic Skin:
           Mechanism, Development and Applications

    • Authors: Jingjie Chen, Lei Wang, Xiangou Xu, Guming Liu, Haoyan Liu, Yuxuan Qiao, Jialin Chen, Siwei Cao, Quanbin Cha, Tengjiao Wang
      First page: 356
      Abstract: Electronic skin (e-skin) has brought us great convenience and revolutionized our way of life. However, due to physical or chemical aging and damage, they will inevitably be degraded gradually with practical operation. The emergence of self-healing materials enables e-skins to achieve repairment of cracks and restoration of mechanical function by themselves, meeting the requirements of the era for building durable and self-healing electronic devices. This work reviews the current development of self-healing e-skins with various application scenarios, including motion sensor, human–machine interaction and soft robots. The new application fields and present challenges are discussed; meanwhile, thinkable strategies and prospects of future potential applications are conferenced.
      Citation: Gels
      PubDate: 2022-06-06
      DOI: 10.3390/gels8060356
      Issue No: Vol. 8, No. 6 (2022)
  • Gels, Vol. 8, Pages 357: Electrospun Core
           (HPMC–Acetaminophen)–Shell (PVP–Sucralose) Nanohybrids
           for Rapid Drug Delivery

    • Authors: Xinkuan Liu, Mingxin Zhang, Wenliang Song, Yu Zhang, Deng-Guang Yu, Yanbo Liu
      First page: 357
      Abstract: The gels of cellulose and its derivatives have a broad and deep application in pharmaceutics; however, limited attention has been paid to the influences of other additives on the gelation processes and their functional performances. In this study, a new type of electrospun core–shell nanohybrid was fabricated using modified, coaxial electrospinning which contained composites of hydroxypropyl methyl cellulose (HPMC) and acetaminophen (AAP) in the core sections and composites of PVP and sucralose in the shell sections. A series of characterizations demonstrated that the core–shell hybrids had linear morphology with clear core–shell nanostructures, and AAP and sucralose distributed in the core and shell section in an amorphous state separately due to favorable secondary interactions such as hydrogen bonding. Compared with the electrospun HPMC–AAP nanocomposites from single-fluid electrospinning of the core fluid, the core–shell nanohybrids were able to promote the water absorbance and HMPC gelation formation processes, which, in turn, ensured a faster release of AAP for potential orodispersible drug delivery applications. The mechanisms of the drug released from these nanofibers were demonstrated to be a combination of erosion and diffusion mechanisms. The presented protocols pave a way to adjust the properties of electrospun, cellulose-based, fibrous gels for better functional applications.
      Citation: Gels
      PubDate: 2022-06-07
      DOI: 10.3390/gels8060357
      Issue No: Vol. 8, No. 6 (2022)
  • Gels, Vol. 8, Pages 358: The Effect of Deoxycholic Acid on
           Chitosan-Enabled Matrices for Tissue Scaffolding and Injectable Nanogels

    • Authors: Bozica Kovacevic, Corina Mihaela Ionescu, Melissa Jones, Susbin Raj Wagle, Michael Lewkowicz, Maja Đanić, Momir Mikov, Armin Mooranian, Hani Al-Salami
      First page: 358
      Abstract: The pathophysiology of a multitude of diseases is influenced by bioenergetic dysfunction. Healthy mitochondria are presented as essential for the regulation and function of multiple cell types, including the cells of relevance for this research: pancreatic beta cells, muscle cells, and liver cells. Hence, effects of hydrogels (particularly nanogels) on bioenergetics needs to be taken into account when designing optimum delivery matrices. Several polymers have been suggested for use in hydrogels and nanogels, with focus on chitosan due to its range of beneficial properties. Bile acids have emerged as beneficial excipients, including deoxycholic acid, which can increase membrane permeability of cells. Nanogels were manufactured containing various concentrations of chitosan and deoxycholic acid in addition to the staple sodium alginate. Nanogels then underwent an array of analysis including rheological studies and in vitro cell work assessing viability, hypoxia, and the bioenergetic profiles. Overall, deoxycholic acid showed enhanced gel strength although this resulted in slightly lower cell viability and impacted bioenergetic profiles. Results from this study showed the benefits of deoxycholic acid; however, this was found to be less suitable for cell delivery matrices and is perhaps more beneficial for drug-delivery systems.
      Citation: Gels
      PubDate: 2022-06-07
      DOI: 10.3390/gels8060358
      Issue No: Vol. 8, No. 6 (2022)
  • Gels, Vol. 8, Pages 359: Composite Aerogel Comprised of Sodium Alginate
           and Bentonite via Supercritical CO2 Drying: An Efficient Adsorbent for

    • Authors: Jie Zhao, Liqin Cao, Yong Dong
      First page: 359
      Abstract: To meet the demand for the separation of specific substances, the construction of porous composite aerogels with a high specific surface area and a strong adsorption capacity is still a challenge. Herein, a sodium alginate/bentonite composite aerogel was efficiently prepared through supercritical fluid drying. The aerogel’s volume shrank less during supercritical drying, maintaining its original three-dimensional mesh structure. The resulting aerogel had a large specific surface area (445 m2/g), a low density (0.059 g/cm3), and a large pore volume (3.617 cm3/g). Due to the fixation and intercalation effects, bentonite was uniformly dispersed in the sodium alginate matrixes. The adsorption of lysozyme by the composite aerogel was evaluated, and the results showed that the optimal adsorption pH was 8 when the pH of the phosphoric acid buffer solution was between pH = 5 and 8.5. The time for adsorption to reach equilibrium was 8 h. The adsorption capacity increased with the increase in bentonite content, and when the initial concentration of lysozyme was from 0.2 to 1.2 g/L, the adsorption capacity first increased and then stabilized, and the maximum adsorption amount was 697 mg/g. The adsorption behavior was simulated in the isothermal region, and the linear correlation coefficient of Langmuir isothermal adsorption fitting was found to be 0.997. Thus, this composite aerogel with strong adsorption capacity can be used as a good alternative to enzymatic adsorbents or immobilized materials.
      Citation: Gels
      PubDate: 2022-06-08
      DOI: 10.3390/gels8060359
      Issue No: Vol. 8, No. 6 (2022)
  • Gels, Vol. 8, Pages 360: Poloxamer-Based Scaffolds for Tissue Engineering
           Applications: A Review

    • Authors: Naiyu Cui, Chun-Yu Dai, Xuran Mao, Xun Lv, Yue Gu, Eui-Seok Lee, Heng-Bo Jiang, Yunhan Sun
      First page: 360
      Abstract: Poloxamer is a triblock copolymer with amphiphilicity and reversible thermal responsiveness and has wide application prospects in biomedical applications owing to its multifunctional properties. Poloxamer hydrogels play a crucial role in the field of tissue engineering and have been regarded as injectable scaffolds for loading cells or growth factors (GFs) in the last few years. Hydrogel micelles can maintain the integrity and stability of cells and GFs and form an appropriate vascular network at the application site, thus creating an appropriate microenvironment for cell growth, nerve growth, or bone integration. The injectability and low toxicity of poloxamer hydrogels make them a noninvasive method. In addition, they can also be good candidates for bio-inks, the raw material for three-dimensional (3D) printing. However, the potential of poloxamer hydrogels has not been fully explored owing to the complex biological challenges. In this review, the latest progress and cutting-edge research of poloxamer-based scaffolds in different fields of application such as the bone, vascular, cartilage, skin, nervous system, and organs in tissue engineering and 3D printing are reviewed, and the important roles of poloxamers in tissue engineering scaffolds are discussed in depth.
      Citation: Gels
      PubDate: 2022-06-08
      DOI: 10.3390/gels8060360
      Issue No: Vol. 8, No. 6 (2022)
  • Gels, Vol. 8, Pages 361: Recent Studies on Hydrogels Based on
           H2O2-Responsive Moieties: Mechanism, Preparation and Application

    • Authors: Weihua Song, Jipeng You, Yuangong Zhang, Qi Yang, Jin Jiao, Hailei Zhang
      First page: 361
      Abstract: H2O2 is essential for cellular processes and plays a vital role in the regulation of cell signaling pathways, which can be viewed as a warning signal for many kinds of disease including cancer, cardiovascular disease, reproductive abnormalities, diabetes, and renal failure. A H2O2-responsive hydrogel (H2O2-Gel) is a promising candidate for biomedical applications because of its good biocompatibility, similarity to soft biological tissues, ease of preparation, and its ability to respond to H2O2. In this study, the H2O2-responsive moieties used to fabricate H2O2-Gels were reviewed, including thioethers, disulfide bonds, selenides, diselenium bonds, diketones, boronic, and others. Next, the preparation method of H2O2-Gel was divided into two major categories according to their reaction mechanisms: either self-crosslinking or mechanisms entailing the addition of difunctional crosslinkers. Last, the applications of H2O2-Gels were emphasized, which have been viewed as desirable candidates in the fields of drug delivery, the detection of H2O2, glucose-responsive systems, ROS scavengers, tissue engineering, and cell-encapsulation.
      Citation: Gels
      PubDate: 2022-06-08
      DOI: 10.3390/gels8060361
      Issue No: Vol. 8, No. 6 (2022)
  • Gels, Vol. 8, Pages 362: New Insights and Experimental Investigation of
           High-Temperature Gel Reinforced by Nano-SiO2

    • Authors: Hongbin Guo, Jijiang Ge, Longjie Li, Guoliang Zhang, Ziwei Li, Wenhui Wang, Mingjia Liu
      First page: 362
      Abstract: The properties of a reinforced gel with partially hydrolyzed polyacrylamide (HPAM) as the main agent, water-soluble phenolic resin (WSPR) as the crosslinker, and nano-SiO2 as the stabilizer were evaluated in terms of gelation time, gel strength and thermal stability under the conditions of 110 °C and 12.124 g/L salinity in water. The results showed that the gelation time of the gel with high strength was adjustable from 3 to 23 h, remaining stable for more than 180 days under stratigraphic conditions, although with a certain degree of early dehydration in the gel. Cryo-scanning electron microscopy (cryo-SEM) and dynamic light scattering (DLS) analysis revealed that nano-SiO2 improves the dispersion of the polymer in water, resulting in a more homogeneous structure of the formed gel and thus improving the strength of the gels. In addition, rheological tests and cryo-SEM showed that the interaction between nano-SiO2 and the polymer could inhibit the degradation of polymer to a certain extent and improve the thermal stability of the gel. However, the oxidative degradation of the gel is still the main cause of early dehydration of water-soluble phenolic resin gel, and the addition of a small amount of hydroquinone to the gelants can significantly improve the antioxidative degradation properties of phenolic resin gel.
      Citation: Gels
      PubDate: 2022-06-08
      DOI: 10.3390/gels8060362
      Issue No: Vol. 8, No. 6 (2022)
  • Gels, Vol. 8, Pages 363: Plasticizers and Salt Concentrations Effects on
           Polymer Gel Electrolytes Based on Poly (Methyl Methacrylate) for
           Electrochemical Applications

    • Authors: Carmen Rizzuto, Dale C. Teeters, Riccardo C. Barberi, Marco Castriota
      First page: 363
      Abstract: This work describes the electrochemical properties of a type of PMMA-based gel polymer electrolytes (GPEs). The gel polymer electrolyte systems at a concentration of (20:80) % w/w were prepared from poly (methyl methacrylate), lithium perchlorate LiClO4 and single plasticizer propylene carbonate (PMMA-Li-PC) and a mixture of plasticizers made by propylene carbonate and ethylene carbonate in molar ratio 1:1, (PMMA-Li-PC-EC). Different salt concentrations (0.1 M, 0.5 M, 1 M, 2 M) were studied. The effect of different plasticizers (single and mixed) on the properties of gel polymer electrolytes were considered. The variation of conductivity versus salt concentration, thermal properties using DSC and TGA, anodic stability and FTIR spectroscopy were used in this study. The maximum ionic conductivity of σ = 0.031 S/cm were obtained for PMMA-Li-PC-EC with a salt concentration equal to 1 M. Ion-pairing phenomena and all ion associations were observed between lithium cations, plasticizers and host polymers through FTIR spectroscopy. The anodic stability of the PMMA-based gel polymer electrolytes was recorded up to 4 V. The glass temperatures of these electrolytes were estimated. We found they were dependent on the plasticization effect of plasticizers on the polymer chains and the increase of the salt concentration. Unexpectedly, it was determined that an unreacted PMMA monomer was present in the system, which appears to enhance ion conduction. The presence and possibly the addition of a monomer may be a technique for increasing ion conduction in other gel systems that warrants further study.
      Citation: Gels
      PubDate: 2022-06-08
      DOI: 10.3390/gels8060363
      Issue No: Vol. 8, No. 6 (2022)
  • Gels, Vol. 8, Pages 364: Advances in Cellulose-Based Hydrogels for
           Biomedical Engineering: A Review Summary

    • Authors: Pengfei Zou, Jiaxin Yao, Ya-Nan Cui, Te Zhao, Junwei Che, Meiyan Yang, Zhiping Li, Chunsheng Gao
      First page: 364
      Abstract: In recent years, hydrogel-based research in biomedical engineering has attracted more attention. Cellulose-based hydrogels have become a research hotspot in the field of functional materials because of their outstanding characteristics such as excellent flexibility, stimulus-response, biocompatibility, and degradability. In addition, cellulose-based hydrogel materials exhibit excellent mechanical properties and designable functions through different preparation methods and structure designs, demonstrating huge development potential. In this review, we have systematically summarized sources and types of cellulose and the formation mechanism of the hydrogel. We have reviewed and discussed the recent progress in the development of cellulose-based hydrogels and introduced their applications such as ionic conduction, thermal insulation, and drug delivery. Also, we analyzed and highlighted the trends and opportunities for the further development of cellulose-based hydrogels as emerging materials in the future.
      Citation: Gels
      PubDate: 2022-06-08
      DOI: 10.3390/gels8060364
      Issue No: Vol. 8, No. 6 (2022)
  • Gels, Vol. 8, Pages 365: Gelatin Nanoparticles for Targeted Dual Drug
           Release out of Alginate-di-Aldehyde-Gelatin Gels

    • Authors: Sophie Schrade, Lucas Ritschl, Regine Süss, Pia Schilling, Michael Seidenstuecker
      First page: 365
      Abstract: The aim of the present work was to develop a dual staged drug release of an antibiotic (clindamycin) and a growth factor: bone morphogenetic protein-2 (BMP-2) from a biodegradable system consisting of hydrogel and gelatin nanoparticles (GNP). Two-step de-solvation allowed us to prepare GNPs (~100 nm) as drug carriers. Fluorescein isothiocyanate (FITC)-conjugated protein A was used as a model substance for BMP-2. A 28-day release experiment was performed to determine the release kinetics from GNP for both FITC-protein A and BMP-2, and for clindamycin (CLI) from the hydrogel. The size, structure, and overall morphology of GNP samples (empty, loaded with FITC-protein A and BMP-2) were examined using an environmental scanning electron microscope (ESEM). Cell culture assays (Live/dead; cell proliferation; cytotoxicity) were performed with MG-63 cells and BMP-2-loaded GNPs. Drug release experiments using clindamycin-loaded alginate-di-aldehyde (ADA) gelatin gels containing the drug-loaded GNPs were performed for 28 days. The resulting GNPs showed an empty size of 117 ± 29 nm, 176 ± 15 nm and 216 ± 36 nm when containing 2% FITC-protein A and 1% BMP-2, respectively. No negative effects of BMP-2-loaded GNPs on MG-63 cells were observed in live/dead staining. In the proliferation assay, an increase in cell proliferation was observed for both GNPs (GNP + BMP-2 and controls). The cytotoxicity assay continuously showed very low cytotoxicity for GNPs (empty; loaded). Clindamycin release showed a concentration of 25-fold higher than the minimum inhibitory concentration (MIC) against Staphylococcus aureus throughout the 28 day period. BMP-2 showed a reduced burst release and a steady release (~2 µg/mL) over a 28 day period.
      Citation: Gels
      PubDate: 2022-06-08
      DOI: 10.3390/gels8060365
      Issue No: Vol. 8, No. 6 (2022)
  • Gels, Vol. 8, Pages 366: Synthesis and Hydrogelation of Star-Shaped Graft
           Copolypetides with Asymmetric Topology

    • Authors: Thi Ha My Phan, Yu-Hsun Yang, Yi-Jen Tsai, Fang-Yu Chung, Tooru Ooya, Shiho Kawasaki, Jeng-Shiung Jan
      First page: 366
      Abstract: To study the self-assembly and hydrogel formation of the star-shaped graft copolypeptides with asymmetric topology, star-shaped poly(L-lysine) with various arm numbers were synthesized by using asymmetric polyglycerol dendrimers (PGDs) as the initiators and 1,1,3,3-tetramethylguanidine (TMG) as an activator for OH groups, followed by deprotection and grafting with indole or phenyl group on the side chain. The packing of the grafting moiety via non-covalent interactions not only facilitated the polypeptide segments to adopt more ordered conformations but also triggered the spontaneous hydrogelation. The hydrogelation ability was found to be correlated with polypeptide composition and topology. The star-shaped polypeptides with asymmetric topology exhibited poorer hydrogelation ability than those with symmetric topology due to the less efficient packing of the grafted moiety. The star-shaped polypeptides grafted with indole group on the side chain exhibited better hydrogelation ability than those grafted with phenyl group with the same arm number. This report demonstrated that the grafted moiety and polypeptide topology possessed the potential ability to modulate the polypeptide hydrogelation and hydrogel characteristics.
      Citation: Gels
      PubDate: 2022-06-09
      DOI: 10.3390/gels8060366
      Issue No: Vol. 8, No. 6 (2022)
  • Gels, Vol. 8, Pages 367: Facile Fabrication of Transparent and Opaque
           Albumin Methacryloyl Gels with Highly Improved Mechanical Properties and
           Controlled Pore Structures

    • Authors: Mengdie Xu, Nabila Mehwish, Bae Hoon Lee
      First page: 367
      Abstract: For porous protein scaffolds to be employed in tissue-engineered structures, the development of cost-effective, macroporous, and mechanically improved protein-based hydrogels, without compromising the original properties of native protein, is crucial. Here, we introduced a facile method of albumin methacryloyl transparent hydrogels and opaque cryogels with adjustable porosity and improved mechanical characteristics via controlling polymerization temperatures (room temperature and −80 °C). The structural, morphological, mechanical, and physical characteristics of both porous albumin methacryloyl biomaterials were investigated using FTIR, CD, SEM, XRD, compression tests, TGA, and swelling behavior. The biodegradation and biocompatibility of the various gels were also carefully examined. Albumin methacryloyl opaque cryogels outperformed their counterpart transparent hydrogels in terms of mechanical characteristics and interconnecting macropores. Both materials demonstrated high mineralization potential as well as good cell compatibility. The solvation and phase separation owing to ice crystal formation during polymerization are attributed to the transparency of hydrogels and opacity of cryogels, respectively, suggesting that two fully protein-based hydrogels could be used as visible detectors/sensors in medical devices or bone regeneration scaffolds in the future.
      Citation: Gels
      PubDate: 2022-06-10
      DOI: 10.3390/gels8060367
      Issue No: Vol. 8, No. 6 (2022)
  • Gels, Vol. 8, Pages 368: Solidification of Gelatine Hydrogels by Using a
           Cryoplatform and Its Validation through CFD Approaches

    • Authors: Yasir Beeran Pottathara, Miha Jordan, Timi Gomboc, Blaž Kamenik, Boštjan Vihar, Vanja Kokol, Matej Zadravec
      First page: 368
      Abstract: In this work, we developed a numerical approach based on an experimental platform to determine the working conditions on a cryoplatform and to predict and evaluate the cryogenic printing of hydrogels. Although hydrogels have good biocompatibility, their material properties make it difficult to print them with high precision and shape fidelity. To overcome these problems, a cryogenic cooling platform was introduced to accelerate the physical stabilisation of each deposited layer during the printing process. By precisely controlling solidification (crystallisation), each printed material can withstand its own weight to maintain shape fidelity, and the porosity of the scaffolds can also be controlled more selectively. The thermophysical properties of gelatine hydrogels were investigated to gain a better understanding of the phase change upon freezing. The corresponding material properties and experimental observations of gelatine solidification served as the basis for developing a computational fluid model (CFD) to mimic the solidification of gelatine hydrogels using a cryoplatform at different process conditions and extruder speeds. The goal was to develop a tool simple enough to predict acceptable process conditions for printing gelatine hydrogels using a cryoplatform.
      Citation: Gels
      PubDate: 2022-06-10
      DOI: 10.3390/gels8060368
      Issue No: Vol. 8, No. 6 (2022)
  • Gels, Vol. 8, Pages 369: Development of β-Cyclodextrin/Konjac-Based
           Emulsion Gel for a Pork Backfat Substitute in Emulsion-Type Sausage

    • Authors: Yea-Ji Kim, Dong-Min Shin, Jong-Hyeok Yune, Hyun-Su Jung, Hyuk-Cheol Kwon, Kyung-Woo Lee, Jae-Wook Oh, Beob-Gyun Kim, Sung-Gu Han
      First page: 369
      Abstract: Emulsion gel has been used to replace animal fats in meat products. Konjac is a widely used gelling agent; however, its low emulsion stability limits its use in meat products. This study aimed to examine the quality characteristics of β-cyclodextrin (CD)-supplemented konjac-based emulsion gel (KEG) (CD-KEG) and its application as a fat substitute in emulsion-type sausages. The supplementation of CD increased hydrogen bonds and hydrophobic interactions with konjac and oil in the gels, respectively. Additionally, CD increased the structural complexity and strength of KEG. Since adding more than 6% of CD to KEG did not increase the gel strength, 6% CD-added KEG was adopted to substitute for pork backfat in manufacturing low-fat emulsion-type sausages. The following formulations of the sausages were prepared: pork backfat 20% (PF20); pork backfat 10% + KEG 10% (KEG10); KEG 20% (KEG20); pork backfat 10% + CD-KEG 10% (CD-KEG10); CD-KEG 20% (CD-KEG20); and pork backfat 5% (PF5). The CD-KEG20 formulation exhibited higher viscosity and viscoelasticity than KEG20, which suggested that CD improves the rheological properties and the thermal stability of meat batter. Additionally, CD-KEG20 showed similar emulsion stability, cooking yield and texture parameters compared with PF20. Therefore, 6% CD-added KEG is a suitable fat substitute for preparing low-fat emulsion-type sausages.
      Citation: Gels
      PubDate: 2022-06-11
      DOI: 10.3390/gels8060369
      Issue No: Vol. 8, No. 6 (2022)
  • Gels, Vol. 8, Pages 370: Gel Polymer Electrolytes with Mixture of
           Triazolium Ionic Liquids and Propylene Carbonate

    • Authors: Aneta Lewandowska, Piotr Gajewski, Katarzyna Szcześniak, Agnieszka Marcinkowska
      First page: 370
      Abstract: This study is focused on the structural influence of 1,2,4-triazolium ionic liquid (IL), that is, the effect of the length of the substituent and the type of substitution (1-methyl-4-alkyl or 1-alkyl-4-methyl) used in the mixture with propylene carbonate (PC) on the properties of thiol–ene polymer ionogels and on the preparation of an ionogel with satisfactory mechanical and conductive properties. PC allows for higher conductivity but also causes electrolyte leakage from the gel. When using triazolium IL (instead of the imidazolium one), because of the stronger interactions between components of the system, the ionogels do not leak. In this study, 1,4-dialkyl-1,2,4-triazolium ILs were successfully synthesized by the alkylation of 1,2,4-triazole. Subsequently, gel polymer electrolytes were obtained by one-pot thiol–ene photopolymerization reactions of tetrafunctional thiols with different chemical structures: pentaerythritol tetra(3-mercaptopropionate) (PETMP) or pentaerythritol tetra(3-mercaptobutyrate) (PETMB) and trifunctional ene (TATT) in the presence of a mixture of 1,4-dialkyl-1,2,4-triazolium IL with PC. Measurements made by electrochemical impedance spectroscopy showed that all ionogels with TATT+PETMB as a polymer matrix presented smaller relative ionic conductivity compared to ionogels containing TATT+PETMP. The puncture resistance and elongation at puncture, measured by the puncture resistance method, were higher for ionogels with poly(TATT+PETMB) than for those with poly(TATT+PETMP). Moreover, ILs containing a methyl group in position N1 of the 1,2,4-triazole ring presented lower puncture resistance than ionogels with ILs containing a methyl group in position N4, especially for shorter alkyl chains. Additionally, the photo-differential scanning calorimetry method was employed to characterize the course of photopolymerization. The compositions and their constituents were characterized by UV and IR spectroscopy.
      Citation: Gels
      PubDate: 2022-06-12
      DOI: 10.3390/gels8060370
      Issue No: Vol. 8, No. 6 (2022)
  • Gels, Vol. 8, Pages 371: Enhanced Oil Recovery Mechanism and Technical
           Boundary of Gel Foam Profile Control System for Heterogeneous Reservoirs
           in Changqing

    • Authors: Liang-Liang Wang, Teng-Fei Wang, Jie-Xiang Wang, Hai-Tong Tian, Yi Chen, Wei Song
      First page: 371
      Abstract: The gel plugging and flooding system has a long history of being researched and applied, but the Changqing reservoir geological characteristics are complex, and the synergistic performance of the composite gel foam plugging system is not fully understood, resulting in poor field application. Additionally, the technique boundary chart of the heterogeneous reservoir plugging system has hardly appeared. In this work, reservoir models of porous, fracture, and pore-fracture were constructed, a composite gel foam plugging system was developed, and its static injection and dynamic profile control and oil displacement performance were evaluated. Finally, combined with the experimental studies, a technical boundary chart of plugging systems for heterogeneous reservoirs is proposed. The research results show that the adsorption effect of microspheres (WQ-100) on the surface of elastic gel particles-1 (PEG-1) is more potent than that of pre-crosslinked particle gel (PPG) and the deposition is mainly on the surface of PPG. The adsorption effect of PEG-1 on the surface of PPG is not apparent, primarily manifested as deposition stacking. The gel was synthesized with 0.2% hydrolyzed polyacrylamide (HPAM) + 0.2% organic chromium cross-linking agent, and the strength of enhanced gel with WQ-100 was higher than that of PEG-1 and PPG. The comprehensive value of WQ-100 reinforced foam is greater than that of PEG-1, and PPG reinforced foam, and the enhanced foam with gel has a thick liquid film and poor foaming effect. For the heterogeneous porous reservoir with the permeability of 5/100 mD, the enhanced foam with WQ-100 shows better performance in plugging control and flooding, and the recovery factor increases by 28.05%. The improved foam with gel enhances the fluid flow diversion ability and the recovery factor of fractured reservoirs with fracture widths of 50 μm and 180 μm increases by 29.41% and 24.39%, respectively. For pore-fractured reservoirs with a permeability of 52/167 mD, the PEG + WQ-100 microsphere and enhanced foam with WQ-100 systems show better plugging and recovering performance, and the recovery factor increases are 20.52% and 17.08%, 24.44%, and 21.43%, respectively. The smaller the particle size of the prefabricated gel, the more uniform the adsorption on the foam liquid film and the stronger the stability of the foam system. The plugging performance of the composite gel system is stronger than that of the enhanced gel with foam, but the oil displacement performance of the gel-enhanced foam is better than that of the composite gel system due to the “plug-flooding-integrated” feature of the foam. Combined with the plugging and flooding performance of each plugging system, a technique boundary chart for the plugging system was established for the coexisting porous, fracture, and pore-fracture heterogeneous reservoirs in Changqing Oilfield.
      Citation: Gels
      PubDate: 2022-06-12
      DOI: 10.3390/gels8060371
      Issue No: Vol. 8, No. 6 (2022)
  • Gels, Vol. 8, Pages 372: Polyaniline Functionalized Peptide Self-Assembled
           Conductive Hydrogel for 3D Cell Culture

    • Authors: Jieling Li, Yan Xue, Anhe Wang, Shaonan Tian, Qi Li, Shuo Bai
      First page: 372
      Abstract: The functionalization of self-assembled peptide hydrogel is of great importance to broaden its applications in the field of biomedicine. In this work, conductive hydrogel is fabricated by introducing conductive polymer polyaniline into peptide self-assembled hydrogel. Compared with pure peptide formed hydrogel, the conductive hydrogel exhibits enhanced conductivity, mechanical property and stability. In addition, the hydrogel is tested to be of great injectability and 3D bio-printability and could support the viability of encapsulated cells that are sensitive to electrical signals. It should have great application prospects in the preparation of tissue engineering scaffolds.
      Citation: Gels
      PubDate: 2022-06-13
      DOI: 10.3390/gels8060372
      Issue No: Vol. 8, No. 6 (2022)
  • Gels, Vol. 8, Pages 373: Identification of Gas Channeling and Construction
           of a Gel-Enhanced Foam Plugging System for Oxygen-Reduced Air Flooding in
           the Changqing Oilfield

    • Authors: Tengfei Wang, Liangliang Wang, Haoliang Qin, Cong Zhao, Zongxian Bai, Xingbang Meng
      First page: 373
      Abstract: The accurate identification of gas channeling channels during foam-assisted oxygen-reduced air flooding (FAORAF) and the analysis of the main controlling factors are essential to propose reasonable and effective countermeasures to enhance oil recovery (EOR). However, there are few comprehensive studies on identifying gas channeling channels, the influencing factors, and the corresponding plugging EOR systems in FAORAF. The channeling channels of the injection and production wells of the Changqing Oilfield, China, under varying development schemes are identified utilizing fuzzy membership function theory in this work to obtain their primary distribution. The characteristics and influence factors of gas channeling channels are analyzed by numerical simulation using CMG. The recovery performance of each foam blocking system is evaluated by twin-tube sand pack models. As well, based on the features of reservoir fractures, a new gel-enhanced foam plugging system is developed. The results show that channeling channels chiefly develop along NE 60–70° and that foam could reduce gas channeling. Natural and artificial fractures are the principal factors causing gas channeling, followed by the injection method and gas injection rate. Under the premise of the injection and migration efficiency, the optimal gel system is a 0.1% HPAM + 0.1% organic chromium crosslinking agent. The addition of gel increases the viscosity of the liquid phase and strengthens the mechanical strength of the foam liquid film. At a permeability ratio of 12, the recovery factors of the binary plugging systems composed of microspheres, PEG, and gel combined with foam are 40.89%, 45.85%, and 53.33%, respectively. The movable gel foam system has a short breaking time (only 18 days) and a recovery factor of about 40% at a permeability ratio of 20. To be suitable for oil reservoirs with microfractures, an improved ternary gel foam system—0.1% HPAM + 0.1% chromium crosslinking agent + 0.05–0.1% nano-SiO2—is developed. Compared with the binary gel foam system, the recovery rate of the new nano-SiO2 gel foam system after 15 days of ageing using the core splitting test is 25.24% during the FAORAF process, increasing by 12.38%.
      Citation: Gels
      PubDate: 2022-06-13
      DOI: 10.3390/gels8060373
      Issue No: Vol. 8, No. 6 (2022)
  • Gels, Vol. 8, Pages 374: Smart Antifreeze Hydrogels with Abundant Hydrogen
           Bonding for Conductive Flexible Sensors

    • Authors: Bailin Dai, Ting Cui, Yue Xu, Shaoji Wu, Youwei Li, Wu Wang, Sihua Liu, Jianxin Tang, Li Tang
      First page: 374
      Abstract: Recently, flexible sensors based on conductive hydrogels have been widely used in human health monitoring, human movement detection and soft robotics due to their excellent flexibility, high water content, good biocompatibility. However, traditional conductive hydrogels tend to freeze and lose their flexibility at low temperature, which greatly limits their application in a low temperature environment. Herein, according to the mechanism that multi−hydrogen bonds can inhibit ice crystal formation by forming hydrogen bonds with water molecules, we used butanediol (BD) and N−hydroxyethyl acrylamide (HEAA) monomer with a multi−hydrogen bond structure to construct LiCl/p(HEAA−co−BD) conductive hydrogel with antifreeze property. The results indicated that the prepared LiCl/p(HEAA−co−BD) conductive hydrogel showed excellent antifreeze property with a low freeze point of −85.6 °C. Therefore, even at −40 °C, the hydrogel can still stretch up to 400% with a tensile stress of ~450 KPa. Moreover, the hydrogel exhibited repeatable adhesion property (~30 KPa), which was attributed to the existence of multiple hydrogen bonds. Furthermore, a simple flexible sensor was fabricated by using LiCl/p(HEAA−co−BD) conductive hydrogel to detect compression and stretching responses. The sensor had excellent sensitivity and could monitor human body movement.
      Citation: Gels
      PubDate: 2022-06-13
      DOI: 10.3390/gels8060374
      Issue No: Vol. 8, No. 6 (2022)
  • Gels, Vol. 8, Pages 375: A Novel Numerical Model of Gelant Inaccessible
           Pore Volume for In Situ Gel Treatment

    • Authors: Jianqiao Leng, Xindi Sun, Mingzhen Wei, Baojun Bai
      First page: 375
      Abstract: Inaccessible pore volume (IAPV) can have an important impact on the placement of gelant during in situ gel treatment for conformance control. Previously, IAPV was considered to be a constant factor in simulators, yet it lacked dynamic characterization. This paper proposes a numerical simulation model of IAPV. The model was derived based on the theoretical hydrodynamic model of gelant molecules. The model considers both static features, such as gelant and formation properties, and dynamic features, such as gelant rheology and retention. To validate our model, we collected IAPV from 64 experiments and the results showed that our model fit moderately into these lab results, which proved the robustness of our model. The results of the sensitivity test showed that, considering rheology and retention, IAPV in the matrix dramatically increased when flow velocity and gelant concentration increased, but IAPV in the fracture maintained a low value. Finally, the results of the penetration degree showed that the high IAPV in the matrix greatly benefited gelant placement near the wellbore situation with a high flow velocity and gelant concentration. By considering dynamic features, this new numerical model can be applied in future integral reservoir simulators to better predict the gelant placement of in situ gel treatment for conformance control.
      Citation: Gels
      PubDate: 2022-06-13
      DOI: 10.3390/gels8060375
      Issue No: Vol. 8, No. 6 (2022)
  • Gels, Vol. 8, Pages 376: Transforming Capillary Alginate Gel (Capgel) into
           New 3D-Printing Biomaterial Inks

    • Authors: Andrew Philip Panarello, Corey Edward Seavey, Mona Doshi, Andrew K. Dickerson, Thomas J. Kean, Bradley Jay Willenberg
      First page: 376
      Abstract: Three-dimensional (3D) printing has great potential for creating tissues and organs to meet shortfalls in transplant supply, and biomaterial inks are key components of many such approaches. There is a need for biomaterial inks that facilitate integration, infiltration, and vascularization of targeted 3D-printed structures. This study is therefore focused on creating new biomaterial inks from self-assembled capillary alginate gel (Capgel), which possesses a unique microstructure of uniform tubular channels with tunable diameters and densities. First, extrusions of Capgel through needles (0.1–0.8 mm inner diameter) were investigated. It was found that Capgel ink extrudes as slurries of fractured and entangled particles, each retaining capillary microstructures, and that extruded line widths W and particle sizes A were both functions of needle inner diameter D, specifically power-law relationships of W~D0.42 and A~D1.52, respectively. Next, various structures were successfully 3D-printed with Capgel ink, thus demonstrating that this biomaterial ink is stackable and self-supporting. To increase ink self-adherence, Capgel was coated with poly-L-lysine (PLL) to create a cationic “skin” prior to extrusion. It was hypothesized that, during extrusion of Capgel-PLL, the sheared particles fracture and thereby expose cryptic sites of negatively-charged biomaterial capable of forming new polyelectrolyte bonds with areas of the positively-charged PLL skin on neighboring entangled particles. This novel approach resulted in continuous, self-adherent extrusions that remained intact in solution. Human lung fibroblasts (HLFs) were then cultured on this ink to investigate biocompatibility. HLFs readily colonized Capgel-PLL ink and were strongly oriented by the capillary microstructures. This is the first description of successful 3D-printing with Capgel biomaterial ink as well as the first demonstration of the concept and formulation of a self-adherent Capgel-PLL biomaterial ink.
      Citation: Gels
      PubDate: 2022-06-14
      DOI: 10.3390/gels8060376
      Issue No: Vol. 8, No. 6 (2022)
  • Gels, Vol. 8, Pages 377: Emulsion Gels as Precursors for Porous Silicones
           and All-Polymer Composites—A Proof of Concept Based on Siloxane

    • Authors: Carmen Racles, Adrian Bele, Ana-Lavinia Vasiliu, Liviu Sacarescu
      First page: 377
      Abstract: In spite of its versatility, the emulsion templating method is rather uncommon for the preparation of porous silicones. In this contribution, two siloxane-containing stabilizers, designed to be soluble in polar (water) and non-polar (toluene) solvents, respectively, were used in low concentrations to produce stable emulsions, wherein polysiloxane gels were obtained by UV-photoinitiated thiol-ene click cross-linking. The stabilizers exhibited negative interfacial tension, as measured by Wilhelmy plate tensiometry. The emulsion gels evolved into porous silicones (xerogels), with tunable morphology and properties. According to TEM and SEM investigations, the emulsion template was preserved in the final materials. Several parameters (e.g., the structure of the polysiloxane precursors, composition of the emulsion gels, nature of the continuous phase, cross-linking conditions, or additives) can be varied in order to obtain porous elastic materials with desired properties, such as Janus membranes, absorbent monoliths, all-polymer porous composites, or silicone-swollen gels. The feasibility of these types of materials was tested, and exemplary porous silicones were briefly characterized by contact angle measurements, mechanical testing, and absorption tests. The proposed method is simple, fast, and economic, uses very little amounts of stabilizers, and can be adjusted as a green technique. In this contribution, all the silicon-based materials with a convenient design were prepared in house.
      Citation: Gels
      PubDate: 2022-06-14
      DOI: 10.3390/gels8060377
      Issue No: Vol. 8, No. 6 (2022)
  • Gels, Vol. 8, Pages 378: The Study of Amidoxime-Functionalized Cellulose
           Separate Th(IV) from Aqueous Solution

    • Authors: Yiling Zhi, Guojian Duan, Zhiwei Lei, Hui Chen, Haobo Zhang, Huining Tian, Tonghuan Liu
      First page: 378
      Abstract: Selective extraction of low-concentration thorium (Th(IV)) from wastewater is a very important research topic. In this paper, amidoxime cellulose was synthesized, and its composition and structure were characterized by FT-IR, SEM, XPS, and elemental analysis. The adsorption experiment results showed that the adsorption reaction was a spontaneous exothermic process. When the solid–liquid ratio was 0.12 g/L and the pH value was 3.5, the adsorption percentage of the Th(IV) in water onto amidoxime-functionalized cellulose (AO-CELL) could reach over 80%. The maximum adsorption capacity can reach to 450 mg/g. At the same time, the adsorption selectivity, desorption process and reusability of the material were also studied. The results showed that the AO-CELL had a good selectivity for Th(IV) in the system with Sr2+, Cu2+, Mg2+, Zn2+, Pb2+, Ni2+, and Co2+ as co-ions. In the nitric acid concentration of 0.06 mol/L system, the AO-CELL desorption rate of Th(IV) can reach 95%, and the adsorption rate of Th(IV) in aqueous solution of AO-CELL is still above 60% when the AO-CELL is reused four times. The above results show that the amidoxime cellulose adsorption material synthesized by our research group has good selective adsorption performance for Th(IV) of a low concentration in an aqueous solution and has a good practical application value.
      Citation: Gels
      PubDate: 2022-06-15
      DOI: 10.3390/gels8060378
      Issue No: Vol. 8, No. 6 (2022)
  • Gels, Vol. 8, Pages 379: Advances of Engineered Hydrogel Organoids within
           the Stem Cell Field: A Systematic Review

    • Authors: Zheng Li, Muxin Yue, Yunsong Liu, Ping Zhang, Jia Qing, Hao Liu, Yongsheng Zhou
      First page: 379
      Abstract: Organoids are novel in vitro cell culture models that enable stem cells (including pluripotent stem cells and adult stem cells) to grow and undergo self-organization within a three-dimensional microenvironment during the process of differentiation into target tissues. Such miniature structures not only recapitulate the histological and genetic characteristics of organs in vivo, but also form tissues with the capacity for self-renewal and further differentiation. Recent advances in biomaterial technology, particularly hydrogels, have provided opportunities to improve organoid cultures; by closely integrating the mechanical and chemical properties of the extracellular matrix microenvironment, with novel synthetic materials and stem cell biology. This systematic review critically examines recent advances in various strategies and techniques utilized for stem-cell-derived organoid culture, with particular emphasis on the application potential of hydrogel technology in organoid culture. We hope this will give a better understanding of organoid cultures for modelling diseases and tissue engineering applications.
      Citation: Gels
      PubDate: 2022-06-15
      DOI: 10.3390/gels8060379
      Issue No: Vol. 8, No. 6 (2022)
  • Gels, Vol. 8, Pages 380: A Facile Method for Fabricating a Monolithic
           Mullite Fiber-Reinforced Alumina Aerogel with Excellent Mechanical and
           Thermal Properties

    • Authors: Lin Liu, Xiaodong Wang, Ze Zhang, Yixin Shi, Yicheng Zhao, Shiqi Shen, Xiandong Yao, Jun Shen
      First page: 380
      Abstract: Alumina aerogels are considered to have good application prospects in the high-temperature field. In this study, monolithic mullite fiber-reinforced alumina aerogels with excellent mechanical and thermal properties were synthesized via a facile method without the use of any chelating agents. This method successfully avoids the introduction of impurities during the use of catalysts and chelating agents while greatly reducing gelation time, and thus helps mullite fibers to uniformly disperse in the sol. The compressive stress at 80% strain of the obtained mullite fiber-reinforced alumina aerogels was as high as 16.04 MPa—426% higher than that of the alumina aerogel without the addition of mullite fibers. Regarding thermal properties, the shrinkage of the mullite fiber-reinforced alumina aerogels (AM) samples was less than 1% after heat treatment at 1300 °C for 2 h. Furthermore, the rear-surface temperature of the AM samples burned by a butane blow torch was only 68 °C. These outstanding properties make AM samples promising for application in thermal insulation materials in high-temperature fields such as aerospace and industrial thermal protection in the future.
      Citation: Gels
      PubDate: 2022-06-15
      DOI: 10.3390/gels8060380
      Issue No: Vol. 8, No. 6 (2022)
  • Gels, Vol. 8, Pages 381: Photopolymerizable Ionogel with Healable
           Properties Based on Dioxaborolane Vitrimer Chemistry

    • Authors: Fengdi Li, Giao T. M. Nguyen, Cédric Vancaeyzeele, Frédéric Vidal, Cédric Plesse
      First page: 381
      Abstract: Ionogels are solid polymer gel networks loaded with ionic liquid (IL) percolating throughout each other, giving rise to ionically conducting solid electrolytes. They combine the mechanical properties of polymer networks with the ionic conductivity, non-volatility, and non-flammability of ILs. In the frame of their applications in electrochemical-based flexible electronics, ionogels are usually subjected to repeated deformation, making them susceptible to damage. It appears critical to devise a simple and effective strategy to improve their durability and lifespan by imparting them with healing ability through vitrimer chemistry. In this work, we report the original in situ synthesis of polythioether (PTE)-based vitrimer ionogels using fast photopolymerization through thiol-acrylate Michael addition. PTE-based vitrimer was prepared with a constant amount of the trithiol crosslinker and varied proportions of static dithiol spacers and dynamic chain extender BDB containing dynamic exchangeable boronic ester groups. The dynamic ionogels were prepared using 50 wt% of either 1-Ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide or 1-Ethyl-3-methylimidazolium trifluoromethanesulfonate, both of which were selected for their high ionic conductivity. They are completely amorphous (Tg below −30 °C), suggesting they can be used at low temperatures. They are stretchable with an elongation at break around 60%, soft with Young’s modulus between 0.4 and 0.6 MPa, and they have high ionic conductivities for solid state electrolytes in the order of 10−4 S·cm−1 at room temperature. They display dynamic properties typical of the vitrimer network, such as stress relaxation and healing, retained despite the large quantity of IL. The design concept illustrated in this work further enlarges the library of vitrimer ionogels and could potentially open a new path for the development of more sustainable, flexible electrochemical-based electronics with extended service life through repair or reprocessing.
      Citation: Gels
      PubDate: 2022-06-15
      DOI: 10.3390/gels8060381
      Issue No: Vol. 8, No. 6 (2022)
  • Gels, Vol. 8, Pages 382: RGD-Functionalized Hydrogel Supports the
           Chondrogenic Commitment of Adipose Mesenchymal Stromal Cells

    • Authors: Cristina Manferdini, Diego Trucco, Yasmin Saleh, Elena Gabusi, Paolo Dolzani, Enrico Lenzi, Lorenzo Vannozzi, Leonardo Ricotti, Gina Lisignoli
      First page: 382
      Abstract: Articular cartilage is known to have limited intrinsic self-healing capacity when a defect or a degeneration process occurs. Hydrogels represent promising biomaterials for cell encapsulation and injection in cartilage defects by creating an environment that mimics the cartilage extracellular matrix. The aim of this study is the analysis of two different concentrations (1:1 and 1:2) of VitroGel® (VG) hydrogels without (VG-3D) and with arginine-glycine-aspartic acid (RGD) motifs, (VG-RGD), verifying their ability to support chondrogenic differentiation of encapsulated human adipose mesenchymal stromal cells (hASCs). We analyzed the hydrogel properties in terms of rheometric measurements, cell viability, cytotoxicity, and the expression of chondrogenic markers using gene expression, histology, and immunohistochemical tests. We highlighted a shear-thinning behavior of both hydrogels, which showed good injectability. We demonstrated a good morphology and high viability of hASCs in both hydrogels. VG-RGD 1:2 hydrogels were the most effective, both at the gene and protein levels, to support the expression of the typical chondrogenic markers, including collagen type 2, SOX9, aggrecan, glycosaminoglycan, and cartilage oligomeric matrix protein and to decrease the proliferation marker MKI67 and the fibrotic marker collagen type 1. This study demonstrated that both hydrogels, at different concentrations, and the presence of RGD motifs, significantly contributed to the chondrogenic commitment of the laden hASCs.
      Citation: Gels
      PubDate: 2022-06-15
      DOI: 10.3390/gels8060382
      Issue No: Vol. 8, No. 6 (2022)
  • Gels, Vol. 8, Pages 383: Use of Carbotrace 480 as a Probe for Cellulose
           and Hydrogel Formation from Defibrillated Microalgae

    • Authors: Frederik L. Zitzmann, Ewan Ward, Avtar S. Matharu
      First page: 383
      Abstract: Carbotrace 480 is a commercially available fluorescent optotracer that specifically binds to cellulose’s glycosidic linkages. Herein, the use of Carbotrace 480 is reported as an analytical tool for linking cellulose content to hydrogel formation capability in defibrillated celluloses obtained from proprietary microalgae. Defibrillated celluloses obtained from acid-free hydrothermal microwave processing at low temperature (160 °C) showed poor hydrogel formation attributed to a low cellulose concentration as evidenced through the lack of Carbotrace fluorescence. High temperature (220 °C) processing afforded reasonable gels commensurate with a higher cellulose loading and stronger response to Carbotrace.
      Citation: Gels
      PubDate: 2022-06-16
      DOI: 10.3390/gels8060383
      Issue No: Vol. 8, No. 6 (2022)
  • Gels, Vol. 8, Pages 384: Formulation Development and Ex-Vivo Permeability
           of Curcumin Hydrogels under the Influence of Natural Chemical Enhancers

    • Authors: Asif Nawaz, Arshad Farid, Muhammad Safdar, Muhammad Shahid Latif, Shakira Ghazanfar, Nosheen Akhtar, Soad K. Al Jaouni, Samy Selim, Muhammad Waseem Khan
      First page: 384
      Abstract: Background: The aim of the present research was to formulate and evaluate curcumin hydrogel and to investigate the potential of natural essential oils as permeation enhancers. Methods: Curcumin 2% w/w hydrogel containing various concentrations of eucalyptus oil, aloe vera oil and clove oil was developed using carboxy methyl cellulose (CMC) as a gelling agent. Differential scanning calorimetry and Fourier Transform infrared spectroscopy were used to evaluate the compatibility between the drug and the excipients. In order to assess the efficacy of the formulation; rheological properties, skin irritation studies, in vitro release, ex vivo permeation and retention studies were conducted. Results: DSC and FTIR suggest no in-compatibility between curcumin and excipients. Studies proved that addition of suitable natural permeation enhancers to the hydrogels improved the in vitro release and ex vivo permeation and retention of curcumin. From the various natural essential oils, the aloe vera oil at a concentration of 3% w/w had the greatest effect on the permeability rate and skin retention of the Curcumin and produces the highest enhancement ratio amongst all the concentrations of essential oils examined. Conclusion: Aloe vera oil enhances the permeation of curcumin across the skin by altering the complex structure of the stratum corneum without itself undergoing any change. The developed curcumin hydrogels along with natural essential oils may present an effective choice regarding skin infection/wound healing.
      Citation: Gels
      PubDate: 2022-06-16
      DOI: 10.3390/gels8060384
      Issue No: Vol. 8, No. 6 (2022)
  • Gels, Vol. 8, Pages 385: Design and Development of Neomycin Sulfate Gel
           Loaded with Solid Lipid Nanoparticles for Buccal Mucosal Wound Healing

    • Authors: Khaled M. Hosny, N. Raghavendra Naveen, Mallesh Kurakula, Amal M. Sindi, Fahad Y. Sabei, Adel Al Fatease, Abdulmajeed M. Jali, Waleed S. Alharbi, Rayan Y. Mushtaq, Majed Felemban, Hossam H. Tayeb, Eman Alfayez, Waleed Y. Rizg
      First page: 385
      Abstract: Drug administration to the wound site is a potential method for wound healing. The drug retention duration should be extended, and drug permeability through the buccal mucosal layer should be regulated. Oral wounds can be caused by inflammation, ulcers, trauma, or pathological lesions; if these wounds are not treated properly, they can lead to pain, infection, and subsequent undesirable scarring. This study aimed to develop Kolliphor-407 P-based gel containing neomycin sulfate (NES) loaded in solid lipid nanoparticles (SLNs) and enhance the antimicrobial activity. By considering lipid concentrations and achieving the lowest particle size (Y1) and maximum entrapment (EE-Y2) effectiveness, the formulation of NES-SLN was optimized using the Box–Behnken design. For the selected responses, 17 runs were formulated (as anticipated by the Design-Expert software) and evaluated accordingly. The optimized formulation could achieve a particle size of 196.25 and EE of 89.27% and was further utilized to prepare the gel formulation. The NES-SLN-G formula was discovered to have a smooth, homogeneous structure and good mechanical and rheological properties. After 24 h of treatment, NES-SLN-G showed a regulated in vitro drug release pattern, excellent ex vivo permeability, and increased in vitro antibacterial activity. These findings indicate the potential application of NES-SLN-loaded gels as a promising formulation for buccal mucosal wound healing.
      Citation: Gels
      PubDate: 2022-06-16
      DOI: 10.3390/gels8060385
      Issue No: Vol. 8, No. 6 (2022)
  • Gels, Vol. 8, Pages 386: Types and Performances of Polymer Gels for
           Oil-Gas Drilling and Production: A Review

    • Authors: Shaofei Lei, Jinsheng Sun, Kaihe Lv, Qitao Zhang, Jingbin Yang
      First page: 386
      Abstract: Polymer gels with suitable viscoelasticity and deformability have been widely used for formation plugging and lost circulation control, profile control, and water shutoff. This article systematically reviews the research progress on the preparation principle, temperature resistance, salt resistance, and mechanical properties of the ground and in situ crosslinked polymer gels for oil-gas drilling and production engineering. Then, it comparatively analyzes the applicable conditions of the two types of polymer gel. To expand the application range of polymer gels in response to the harsh formation environments (e.g., high temperature and high salinity), we reviewed strategies for increasing the high temperature resistance, high salt resistance, and rheological/mechanical strengths of polymer gels. This article provides theoretical and technical references for developing and optimizing polymer gels suitable for oil-gas drilling and production.
      Citation: Gels
      PubDate: 2022-06-17
      DOI: 10.3390/gels8060386
      Issue No: Vol. 8, No. 6 (2022)
  • Gels, Vol. 8, Pages 387: Tuning Myogenesis by Controlling Gelatin Hydrogel
           Properties through Hydrogen Peroxide-Mediated Cross-Linking and

    • Authors: Mubarok, Elvitigala, Sakai
      First page: 387
      Abstract: Engineering skeletal muscle tissue in vitro is important to study the mechanism of myogenesis, which is crucial for regenerating muscle cells. The physicochemical properties of the cellular microenvironment are known to govern various cell behaviours. Yet, most studies utilised synthetic materials to model the extracellular matrix that suffers from cytotoxicity to the cells. We have previously reported that the physicochemical property of hydrogels obtained from horseradish peroxidase (HRP)-catalysed cross-linking could be controlled by a simple adjustment to the exposure time to air containing H2O2. In this study, we evaluated the influence of physicochemical properties dynamics in the gelatin possessing phenol groups (Gelatin-Ph) hydrogel to regulate the myogenesis in vitro. We controlled the Young’s modulus of the Gelatin-Ph hydrogel by tuning the air containing 16 ppm H2O2 exposure time for 15–60 min. Additionally, prolonged exposure to air containing H2O2 also induced Gelatin-Ph degradation. Myoblasts showed higher adhesion and myotube formation on stiff hydrogel (3.53 kPa) fabricated through 30 min of exposure to air containing H2O2 compared to those on softer hydrogel (0.77–2.79 kPa) fabricated through 15, 45, and 60 min of the exposure. These results demonstrate that the myogenesis can be tuned by changes in the physicochemical properties of Gelatin-Ph hydrogel mediated by H2O2.
      Citation: Gels
      PubDate: 2022-06-17
      DOI: 10.3390/gels8060387
      Issue No: Vol. 8, No. 6 (2022)
  • Gels, Vol. 8, Pages 388: Imidazolium Ionic Liquids as Designer Solvents
           Confined in Silica Nanopores

    • Authors: Ana-Maria Putz, Adél Len, László Trif, Zsolt Endre Horváth, László Almásy
      First page: 388
      Abstract: Composite silica xerogels were prepared via acid catalysed sol–gel route using tetraethoxysilan (TEOS) as silica precursor, and 1-butyl-3-methylimidazolium tetrafluoroborate [BMIM][BF4] or 1-butyl-3-methylimidazolium chloride [BMIM][Cl] ionic liquids, used simultaneously as co-solvents, catalysts and pore templates, at various IL-to-silica ratios. Morphology of the xerogels prepared using the different IL templating agents were investigated using scanning electron microscopy (SEM), nitrogen sorption and small angle neutron scattering (SANS). The thermal behavior of the composites was analyzed by thermal gravimetry, whereas the compositions were checked by infrared spectroscopy and EDX. The differences in the morphology and thermal behavior of the composites due to the different IL additives were revealed.
      Citation: Gels
      PubDate: 2022-06-19
      DOI: 10.3390/gels8060388
      Issue No: Vol. 8, No. 6 (2022)
  • Gels, Vol. 8, Pages 389: Advances of Stimulus-Responsive Hydrogels for
           Bone Defects Repair in Tissue Engineering

    • Authors: Shuai Chang, Shaobo Wang, Zhongjun Liu, Xing Wang
      First page: 389
      Abstract: Bone defects, as one of the most urgent problems in the orthopedic clinic, have attracted much attention from the biomedical community and society. Hydrogels have been widely used in the biomedical field for tissue engineering research because of their excellent hydrophilicity, biocompatibility, and degradability. Stimulus-responsive hydrogels, as a new type of smart biomaterial, have more advantages in sensing external physical (light, temperature, pressure, electric field, magnetic field, etc.), chemical (pH, redox reaction, ions, etc.), biochemical (glucose, enzymes, etc.) and other different stimuli. They can respond to stimuli such as the characteristics of the 3D shape and solid–liquid phase state, and exhibit special properties (injection ability, self-repair, shape memory, etc.), thus becoming an ideal material to provide cell adhesion, proliferation, and differentiation, and achieve precise bone defect repair. This review is focused on the classification, design concepts, and research progress of stimulus-responsive hydrogels based on different types of external environmental stimuli, aiming at introducing new ideas and methods for repairing complex bone defects.
      Citation: Gels
      PubDate: 2022-06-20
      DOI: 10.3390/gels8060389
      Issue No: Vol. 8, No. 6 (2022)
  • Gels, Vol. 8, Pages 390: Unravelling the Supramolecular Driving Forces in
           the Formation of CO2-Responsive Pseudopeptidic Low-Molecular-Weight

    • Authors: Ferran Esteve, Alexis Villanueva-Antolí, Belén Altava, Eduardo García-Verdugo, Santiago V. Luis
      First page: 390
      Abstract: A new family of C2-symmetric pseudopeptides with a high functional density for supramolecular interactions has been synthetized through the attachment of four amino acid subunits to a diamino aliphatic spacer. The resulting open-chain compounds present remarkable properties as low-molecular-weight hydrogelators. The self-assembled 3D networks were characterized by SEM analyses, observing regular nanofibres with 80–100 nm diameters. Spectroscopic and molecular modelling experiments revealed the presence of strong synergic effects between the H-bonding and π–π interactions, with the best results obtained for the homoleptic tetra-pseudopeptide derived from l-Phe. In addition, these bioinspired hydrogels possessed pH- and CO2-responsive sol–gel transitions. The formation of ammonium carbamate derivatives in the presence of carbon dioxide led to a detrimental change in its adequate self-assembly. CO2 desorption temperatures of ca. 70 °C were assigned to the thermodynamically favoured recovery of the supramolecular gel.
      Citation: Gels
      PubDate: 2022-06-20
      DOI: 10.3390/gels8060390
      Issue No: Vol. 8, No. 6 (2022)
  • Gels, Vol. 8, Pages 317: Evaluation of Structural Behavior in the Process
           Dynamics of Oleogel-Based Tender Dough Products

    • Authors: Anda E. Tanislav, Andreea Pușcaș, Adriana Păucean, Andruța E. Mureșan, Cristina A. Semeniuc, Vlad Mureșan, Elena Mudura
      First page: 317
      Abstract: The current trend is represented by replacing solid fats with structured liquid oil while maintaining the plastic properties of food products. In this study, the behavior of refined sunflower oil structured with various agents (carnauba wax-CRW, β-sitosterol:beeswax-BS:BW, β-sitosterol:lecithin-BS:LEC, and glycerol monostearate-GM) was evaluated in the process dynamics of oleogel-based tender dough products. The oleogel with the mixture of β-sitosterol:beeswax (OG_BS:BW) displayed the highest capacity to retain oil inside the matrix with a percentage of oil loss as low as 0.05% and also had a significantly higher hardness (6.37 N) than the reference, a commercial margarine (MR—3.58 N). During cooling from 90 to 4 °C, the increase in oleogel’ viscosity results from oleogelator’s liquid–solid phase transition. As demonstrated by the frequency sweeps performed, storage modulus G′ was higher than loss modulus G″, no cross-over points were observed, and the strongest gel network was for the oleogel with glycerol monostearate (OG_GM). Regarding the dough, the sample prepared using the oleogel with carnauba wax (D_CRW) showed the strongest hardness (92.49 N) compared to the reference (D_MR—21.80 N). All the oleogel-containing doughs had elastic solid-like behavior. The samples with margarine (D_MR) and the mixture of β-sitosterol:lecithin (D_BS:LEC) presented the lowest value of both moduli of G’ and G” during the frequency sweep. The biscuits formulated with commercial margarine (B_MR) registered a hardness of 28.74 N. Samples with oleogels showed a specific tenderness for tender dough products, thus being suitable for this type of product (11.22–20.97 N).
      Citation: Gels
      PubDate: 2022-05-19
      DOI: 10.3390/gels8050317
      Issue No: Vol. 8, No. 5 (2022)
  • Gels, Vol. 8, Pages 318: Crisaborole Loaded Nanoemulsion Based Chitosan
           Gel: Formulation, Physicochemical Characterization and Wound Healing

    • Authors: Ansari, Soliman, Rehman, Anwer
      First page: 318
      Abstract: The development of an effective gel capable of treating eczema remains a challenge in medicine. Because of its greater retention in the affected area, good absorption of wound exudates, and induction of cell growth, nanogel is widely investigated as a topical preparation. Chitosan gel based on nanoemulsions has received much attention for its use in wound healing. In this study, four formulae (CRB-NE1-CRB-NE4) of crisaborole-loaded nanoemulsions (CRB-NEs) were developed using lauroglycol 90 as an oil, Tween-80 as a surfactant, and transcutol-HP (THP) as a co-surfactant. The prepared NEs (CRB-NE1-CRB-NE4) were evaluated for their physicochemical properties. Based on vesicle size (64.5 ± 5.3 nm), polydispersity index (PDI) (0.202 ± 0.06), zeta potential (ZP, −36.3 ± 4.16 mV), refractive index (RI, 1.332 ± 0.03), and percent transmittance (% T, 99.8 ± 0.12) was optimized and further incorporated into chitosan (2%, w/w) polymeric gels. The CRB-NE1-loaded chitosan gel was then evaluated for its drug content, spreadability, in-vitro release, flux, wound healing, and anti-inflammatory studies. The CRB-NE1-loaded chitosan gel exhibited a flux of 0.211 mg/cm2/h, a drug release of 74.45 ± 5.4% CRB released in 24 h with a Korsmeyer-Peppas mechanism release behavior. The CRB-NE1-loaded gel exhibited promising wound healing and anti-inflammatory activities.
      Citation: Gels
      PubDate: 2022-05-19
      DOI: 10.3390/gels8050318
      Issue No: Vol. 8, No. 5 (2022)
  • Gels, Vol. 8, Pages 319: Transforming Commercial Copper Sulfide into
           Injectable Hydrogels for Local Photothermal Therapy

    • Authors: Xiaoran Wang, Zizhen Yang, Zhaowei Meng, Shao-Kai Sun
      First page: 319
      Abstract: Photothermal therapy (PTT) is a promising local therapy playing an increasingly important role in tumor treatment. To maximize PTT efficacy, various near-infrared photoabsorbers have been developed. Among them, metal sulfides have attracted considerable interest due to the advantages of good stability and high photothermal conversion efficiency. However, the existing synthesis methods of metal-sulfide-based photoabsorbers suffer from the drawbacks of complicated procedures, low raw material utilization, and poor universality. Herein, we proposed a flexible, adjustable strategy capable of transforming commercial metal sulfides into injectable hydrogels for local PTT. We took copper sulfide (CuS) as a typical example, which has intense second-window near-infrared absorption (1064 nm), to systematically investigate its in vitro and in vivo characteristics. CuS hydrogel with good syringeability was synthesized by simply dispersing commercial CuS powders as photoabsorbers in alginate-Ca2+ hydrogel. This synthesis strategy exhibits the unique merits of an ultra-simple synthesizing process, 100% loading efficiency, good biocompatibility, low cost, outstanding photothermal capacity, and good universality. The in vitro experiments indicated that the hydrogel exhibits favorable photothermal heating ability, and it obviously destroyed tumor cells under 1064 nm laser irradiation. After intratumoral administration in vivo, large-sized CuS particles in the hydrogel highly efficiently accumulated in tumor tissues, and robust local PTT was realized under mild laser irradiation (0.3 W/cm2). The developed strategy for the synthesis of CuS hydrogel provides a novel way to utilize commercial metal sulfides for diverse biological applications.
      Citation: Gels
      PubDate: 2022-05-20
      DOI: 10.3390/gels8050319
      Issue No: Vol. 8, No. 5 (2022)
  • Gels, Vol. 8, Pages 320: Thermal Insulation Performance of SiC-Doped
           Silica Aerogels under Large Temperature and Air Pressure Differences

    • Authors: Sheng-Nan Zhang, Hao-Qiang Pang, Ting-Hui Fan, Qing Ye, Qi-Lin Cai, Xi Wu
      First page: 320
      Abstract: Silica aerogel composite is an excellent thermal insulator for spacecraft under high-temperature and complex air environments. This study intends to evaluate SiC-doped silica aerogel’s thermal insulation performance under large temperature and air pressure differences. In this paper, the hot surface’s temperature response of SiC-doped silica aerogel with different content was studied at significant temperature differences (ΔT) when pressure changes instantaneously. Their thermal insulation performance was evaluated by analyzing the influence of pressure gradients on the unsteady-state heat transfer. When the cold surface’s temperature of the specimen keeps constant at 15 °C and ΔT = 171~912 K, the results demonstrate that the correlative thermal conductivities of silica aerogel with 1% and 5.84% SiC are 0.02223~0.04077 W·m−1·K−1 at P ≈ 10 Pa and 0.03165~0.04665 W·m−1·K−1 at P = 1 atm, respectively. The aerogel composite with 0% SiC showed the best thermal insulation performance at ΔT < 200 K and P ≈ 10 Pa, while the aerogel with 5.84% SiC became the best at ΔT > 700 K and P = 1 atm. In addition, the transient pressure decreases will significantly impair the heat transfer of the gas inside the aerogel, thereby weakening the gaseous thermal conductivity and improving the thermal insulation performance.
      Citation: Gels
      PubDate: 2022-05-20
      DOI: 10.3390/gels8050320
      Issue No: Vol. 8, No. 5 (2022)
  • Gels, Vol. 8, Pages 321: Preparation and Enzyme Degradability of Spherical
           and Water-Absorbent Gels from Sodium Carboxymethyl Cellulose

    • Authors: Sayaka Fujita, Toshiaki Tazawa, Hiroyuki Kono
      First page: 321
      Abstract: To synthesize a biodegradable alternative to spherical polyacrylic acid absorbent resin, spherical hydrogel particles were prepared from carboxymethyl cellulose (CMC) dissolved in an aqueous solution, using ethylene glycol diglycidyl ether (EGDE) as a crosslinking agent. The effect of varying the initial CMC concentration and feed amount of EGDE on the shape, water absorbency, water-holding capacity, and enzyme degradability of the resultant CMC hydrogels was determined. The reaction solution was poured into fluid paraffin, and spherical hydrogel particles were obtained via the shear force from stirring. The shape and diameter of the spherical hydrogel particles in the swollen state depended on the CMC concentration. The spherical hydrogel particles obtained by increasing the amount of EGDE resulted in a decrease in absorbency. Additionally, all the spherical hydrogel particles were degraded by cellulase. Thus, spherical biodegradable hydrogel particles were prepared from CMC, and the particle size and water absorption of the hydrogel could be controlled in the range of 5–18 mm and 30–90 g·g−1 in the swollen state, respectively. As an alternative to conventional superabsorbent polymers, the spherical CMC hydrogels are likely to be useful in industrial and agricultural applications.
      Citation: Gels
      PubDate: 2022-05-20
      DOI: 10.3390/gels8050321
      Issue No: Vol. 8, No. 5 (2022)
  • Gels, Vol. 8, Pages 322: Novel Acrylamide/2-Acrylamide-2-3
           Methylpropanesulfonic Acid/Styrene/Maleic Anhydride Polymer-Based CaCO3
           Nanoparticles to Improve the Filtration of Water-Based Drilling Fluids at
           High Temperature

    • Authors: Zhichuan Tang, Zhengsong Qiu, Hanyi Zhong, Hui Mao, Kai Shan, Yujie Kang
      First page: 322
      Abstract: Filtration loss control under high-temperature conditions is a worldwide issue among water-based drilling fluids (WBDFs). A core–shell high-temperature filter reducer (PAASM-CaCO3) that combines organic macromolecules with inorganic nanomaterials was developed by combining acrylamide (AM), 2-acrylamide-2-methylpropane sulfonic acid (AMPS), styrene (St), and maleic anhydride (MA) as monomers and nano-calcium carbonate (NCC). The molecular structure of PAASM-CaCO3 was characterized. The average molecular weight of the organic part was 6.98 × 105 and the thermal decomposition temperature was about 300 °C. PAASM-CaCO3 had a better high-temperature resistance. The rheological properties and filtration performance of drilling fluids treated with PAASM-CaCO3 were stable before and after aging at 200 °C/16 h, and the effect of filtration control was better than that of commonly used filter reducers. PAASM-CaCO3 improved colloidal stability and mud cake quality at high temperatures.
      Citation: Gels
      PubDate: 2022-05-20
      DOI: 10.3390/gels8050322
      Issue No: Vol. 8, No. 5 (2022)
  • Gels, Vol. 8, Pages 323: Recent Advancements in Materials and Coatings for
           Biomedical Implants

    • Authors: Kamalan Kirubaharan Amirtharaj Mosas, Ashok Raja Chandrasekar, Arish Dasan, Amirhossein Pakseresht, Dušan Galusek
      First page: 323
      Abstract: Metallic materials such as stainless steel (SS), titanium (Ti), magnesium (Mg) alloys, and cobalt-chromium (Co-Cr) alloys are widely used as biomaterials for implant applications. Metallic implants sometimes fail in surgeries due to inadequate biocompatibility, faster degradation rate (Mg-based alloys), inflammatory response, infections, inertness (SS, Ti, and Co-Cr alloys), lower corrosion resistance, elastic modulus mismatch, excessive wear, and shielding stress. Therefore, to address this problem, it is necessary to develop a method to improve the biofunctionalization of metallic implant surfaces by changing the materials’ surface and morphology without altering the mechanical properties of metallic implants. Among various methods, surface modification on metallic surfaces by applying coatings is an effective way to improve implant material performance. In this review, we discuss the recent developments in ceramics, polymers, and metallic materials used for implant applications. Their biocompatibility is also discussed. The recent trends in coatings for biomedical implants, applications, and their future directions were also discussed in detail.
      Citation: Gels
      PubDate: 2022-05-21
      DOI: 10.3390/gels8050323
      Issue No: Vol. 8, No. 5 (2022)
  • Gels, Vol. 8, Pages 324: Fracture Toughness and Blocking Force of
           Temperature-Sensitive PolyNIPAAm and Alginate Hybrid Gels

    • Authors: Yong-Woo Kim, Do Yoon Kim, Jeong-Yun Sun
      First page: 324
      Abstract: In the field of actuator materials, hydrogels that undergo large volume changes in response to external stimuli have been developed for a variety of promising applications. However, most conventional hydrogels are brittle and therefore rupture when they are stretched to moderate strains (~50%). Thus, gels to be used for actuators still require improved mechanical properties and actuation performance. In this study, we synthesized a tough and thermo-sensitive hydrogel with a large actuation force by forming interpenetrating networks between covalently crosslinked poly(N-isopropylacrylamide) and ionically crosslinked alginate. Poly(N-isopropylacrylamide) was used as a thermo-sensitive actuation material, and alginate was found to enhance the mechanical properties of the hydrogels. Due to the enhanced elastic modulus and energy dissipation in the hybrid gel, the toughness was increased by a factor of 60 over that of pure PNIPAAm gel. Further, based on the results showing that the hybrid gel exhibits an actuation force that is seven times higher than that of pure PNIPAAm gel, the hybrid gel is more applicable to real actuators.
      Citation: Gels
      PubDate: 2022-05-23
      DOI: 10.3390/gels8050324
      Issue No: Vol. 8, No. 5 (2022)
  • Gels, Vol. 8, Pages 325: Study on the Structure, Magnetic Properties and
           Mechanism of Zn-Doped Yttrium Iron Garnet Nanomaterial Prepared by the
           Sol-gel Method

    • Authors: Yuheng Guo, Haiyan Li, Shouqiang Li, Leilei Chen, Zhenhai Li
      First page: 325
      Abstract: To explore the effect and mechanism of bivalent ion doping on yttrium iron garnet (YIG), Zn-YIG (Zn-doped YIG) nanoparticles with a size of 60~70 nm were prepared by the sol-gel method. It was proven that Zn ion doping resulted in lattice expansion and internal stress due to crystallite size shrinkage. A Raman spectroscopic analysis proved the influence of Zn doping on the crystal structure and peak intensity by analyzing Raman vibration modes. The characteristics and chemical mechanism of mass loss and phase evolution in each temperature region were explored through TG-DSC measurements. Moreover, it was revealed that the antiferromagnetic coupling, pinning mechanisms and particle aggregation lead to coercivity, exhibiting different variation trends. A saturation magnetization (Ms) curve variation mechanism was further revealed, which was due to the thermal effects, super-exchange effect, and coupling effect between sub-lattices. Meanwhile, the influence of the thermal effect on Ms and its mechanism were explored by spin theory, and it was proven that it was mainly caused by the random arrangement of magnetic moments and thermal vibration. These results provide theoretical support for the wider application of YIG devices in microwave and high-temperature fields.
      Citation: Gels
      PubDate: 2022-05-23
      DOI: 10.3390/gels8050325
      Issue No: Vol. 8, No. 5 (2022)
  • Gels, Vol. 8, Pages 326: New Directions in Aesthetic Medicine: A Novel and
           Hybrid Filler Based on Hyaluronic Acid and Lactose Modified Chitosan

    • Authors: Eva Daminato, Giulio Bianchini, Valerio Causin
      First page: 326
      Abstract: Fillers based on crosslinked hyaluronic acid (HA) are becoming increasingly important in the field of aesthetic medicine, for example for treating wrinkles or for volumizing purposes. However, crosslinking agents are usually associated with toxicity and adverse reactions. The aim of this study is the development of an innovative technology to manufacture high performance HA-based fillers using minimal amounts of crosslinking agent. In this work, new fillers based on HA, functionalized with different amounts of 1,4-butanediol diglycidyl ether (BDDE) (degree of modification ranging between 3.5% and 8.8%) and formulated with a lactose modified chitosan (CTL), were investigated. The relative quantities of these polymeric building blocks in the formulations were 20–25 and 5 mg/mL for HA and CTL, respectively. Due to its cationic nature, CTL could interact with the anionic HA and enhance the elastic properties of the filler. Fillers manufactured with this novel technology (HACL-CTL) were characterized and compared with several fillers available in the market. In particular, resistance against hyaluronidase, swelling, cohesivity and rheological properties were investigated. Cohesivity, resistance to hydrolysis and swelling of HACL-CTL were comparable to commercial products. However, HACL-CTL fillers showed excellent elastic performance that reached 94% of elasticity in response to shear stresses. Surprisingly, these fillers also showed a resistance to compression higher than that of currently marketed products, making them very promising for their lifting effect.
      Citation: Gels
      PubDate: 2022-05-23
      DOI: 10.3390/gels8050326
      Issue No: Vol. 8, No. 5 (2022)
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