Subjects -> CHEMISTRY (Total: 1001 journals)
    - ANALYTICAL CHEMISTRY (59 journals)
    - CHEMISTRY (726 journals)
    - CRYSTALLOGRAPHY (23 journals)
    - ELECTROCHEMISTRY (28 journals)
    - INORGANIC CHEMISTRY (45 journals)
    - ORGANIC CHEMISTRY (49 journals)
    - PHYSICAL CHEMISTRY (71 journals)

CHEMISTRY (726 journals)                  1 2 3 4 | Last

Showing 1 - 200 of 735 Journals sorted alphabetically
Accounts of Materials Research     Hybrid Journal  
Accreditation and Quality Assurance: Journal for Quality, Comparability and Reliability in Chemical Measurement     Hybrid Journal   (Followers: 36)
ACS Applied Polymer Materials     Hybrid Journal   (Followers: 14)
ACS Catalysis     Hybrid Journal   (Followers: 77)
ACS Chemical Neuroscience     Hybrid Journal   (Followers: 25)
ACS Combinatorial Science     Hybrid Journal   (Followers: 25)
ACS Macro Letters     Hybrid Journal   (Followers: 34)
ACS Materials Letters     Open Access   (Followers: 3)
ACS Medicinal Chemistry Letters     Hybrid Journal   (Followers: 49)
ACS Nano     Hybrid Journal   (Followers: 448)
ACS Photonics     Hybrid Journal   (Followers: 19)
ACS Symposium Series     Full-text available via subscription   (Followers: 3)
ACS Synthetic Biology     Hybrid Journal   (Followers: 40)
Acta Chemica Iasi     Open Access   (Followers: 8)
Acta Chemica Malaysia     Open Access  
Acta Chimica Slovaca     Open Access   (Followers: 4)
Acta Chimica Slovenica     Open Access   (Followers: 2)
Acta Chromatographica     Full-text available via subscription   (Followers: 9)
Acta Facultatis Medicae Naissensis     Open Access   (Followers: 1)
Acta Metallurgica Sinica (English Letters)     Hybrid Journal   (Followers: 10)
Acta Scientifica Naturalis     Open Access   (Followers: 3)
adhäsion KLEBEN & DICHTEN     Hybrid Journal   (Followers: 9)
Adhesion Adhesives & Sealants     Hybrid Journal   (Followers: 10)
Adsorption Science & Technology     Open Access   (Followers: 9)
Advanced Electronic Materials     Hybrid Journal   (Followers: 7)
Advanced Functional Materials     Hybrid Journal   (Followers: 81)
Advanced Journal of Chemistry, Section A     Open Access   (Followers: 15)
Advanced Journal of Chemistry, Section B     Open Access   (Followers: 14)
Advanced Science Focus     Free   (Followers: 7)
Advanced Theory and Simulations     Hybrid Journal   (Followers: 5)
Advanced Therapeutics     Hybrid Journal   (Followers: 1)
Advances in Chemical Engineering and Science     Open Access   (Followers: 108)
Advances in Chemical Science     Open Access   (Followers: 50)
Advances in Chemistry     Open Access   (Followers: 39)
Advances in Chemistry     Full-text available via subscription   (Followers: 6)
Advances in Colloid and Interface Science     Full-text available via subscription   (Followers: 21)
Advances in Drug Research     Full-text available via subscription   (Followers: 27)
Advances in Environmental Chemistry     Open Access   (Followers: 11)
Advances in Enzyme Research     Open Access   (Followers: 13)
Advances in Fluorine Science     Full-text available via subscription   (Followers: 8)
Advances in Fuel Cells     Full-text available via subscription   (Followers: 20)
Advances in Heterocyclic Chemistry     Full-text available via subscription   (Followers: 11)
Advances in Materials Physics and Chemistry     Open Access   (Followers: 35)
Advances in Nanoparticles     Open Access   (Followers: 20)
Advances in Organometallic Chemistry     Full-text available via subscription   (Followers: 20)
Advances in Polymer Science     Hybrid Journal   (Followers: 53)
Advances in Protein Chemistry     Full-text available via subscription   (Followers: 19)
Advances in Protein Chemistry and Structural Biology     Full-text available via subscription   (Followers: 22)
Advances in Quantum Chemistry     Full-text available via subscription   (Followers: 7)
Advances in Science and Technology     Full-text available via subscription   (Followers: 17)
Aerosol Science and Engineering     Hybrid Journal  
African Journal of Bacteriology Research     Open Access  
African Journal of Chemical Education     Open Access   (Followers: 6)
African Journal of Pure and Applied Chemistry     Open Access   (Followers: 7)
Aggregate     Open Access   (Followers: 3)
Agrokémia és Talajtan     Full-text available via subscription   (Followers: 3)
Al-Kimia : Jurnal Penelitian Sains Kimia     Open Access  
Alchemy : Journal of Chemistry     Open Access   (Followers: 5)
Alchemy : Jurnal Penelitian Kimia     Open Access   (Followers: 2)
Alkaloids: Chemical and Biological Perspectives     Full-text available via subscription   (Followers: 2)
Alotrop     Open Access  
AMB Express     Open Access   (Followers: 1)
Ambix     Hybrid Journal   (Followers: 3)
American Journal of Biochemistry and Biotechnology     Open Access   (Followers: 71)
American Journal of Biochemistry and Molecular Biology     Open Access   (Followers: 24)
American Journal of Chemistry     Open Access   (Followers: 41)
American Journal of Plant Physiology     Open Access   (Followers: 13)
Analyst     Full-text available via subscription   (Followers: 40)
Analytical Science Advances     Open Access   (Followers: 2)
Angewandte Chemie     Hybrid Journal   (Followers: 235)
Angewandte Chemie International Edition     Hybrid Journal   (Followers: 353)
Annales Universitatis Mariae Curie-Sklodowska, sectio AA – Chemia     Open Access   (Followers: 1)
Annals of Clinical Chemistry and Laboratory Medicine     Open Access   (Followers: 8)
Annual Reports in Computational Chemistry     Full-text available via subscription   (Followers: 4)
Annual Reports Section A (Inorganic Chemistry)     Full-text available via subscription   (Followers: 6)
Annual Reports Section B (Organic Chemistry)     Full-text available via subscription   (Followers: 9)
Annual Review of Chemical and Biomolecular Engineering     Full-text available via subscription   (Followers: 13)
Annual Review of Food Science and Technology     Full-text available via subscription   (Followers: 16)
Antiviral Chemistry and Chemotherapy     Open Access   (Followers: 2)
Applied Organometallic Chemistry     Hybrid Journal   (Followers: 12)
Applied Spectroscopy     Full-text available via subscription   (Followers: 27)
Applied Surface Science     Hybrid Journal   (Followers: 33)
Arabian Journal of Chemistry     Open Access   (Followers: 6)
ARKIVOC     Open Access   (Followers: 1)
Asian Journal of Applied Chemistry Research     Open Access   (Followers: 2)
Asian Journal of Biochemistry     Open Access   (Followers: 3)
Asian Journal of Chemical Sciences     Open Access   (Followers: 1)
Asian Journal of Chemistry and Pharmaceutical Sciences     Open Access   (Followers: 2)
Asian Journal of Physical and Chemical Sciences     Open Access   (Followers: 3)
Atomization and Sprays     Full-text available via subscription   (Followers: 8)
Australian Journal of Chemistry     Hybrid Journal   (Followers: 7)
Autophagy     Hybrid Journal   (Followers: 7)
Avances en Quimica     Open Access  
Biochemical Pharmacology     Hybrid Journal   (Followers: 11)
Biochemistry     Hybrid Journal   (Followers: 484)
Biochemistry Insights     Open Access   (Followers: 7)
Biochemistry Research International     Open Access   (Followers: 6)
BioChip Journal     Hybrid Journal  
Bioinorganic Chemistry and Applications     Open Access   (Followers: 11)
Biointerface Research in Applied Chemistry     Open Access   (Followers: 3)
Biointerphases     Open Access   (Followers: 1)
Biology, Medicine, & Natural Product Chemistry     Open Access   (Followers: 4)
Biomacromolecules     Hybrid Journal   (Followers: 27)
Biomass Conversion and Biorefinery     Partially Free   (Followers: 11)
Biomedical Chromatography     Hybrid Journal   (Followers: 6)
Biomolecular NMR Assignments     Hybrid Journal   (Followers: 4)
BioNanoScience     Partially Free   (Followers: 6)
Bioorganic & Medicinal Chemistry     Hybrid Journal   (Followers: 214)
Bioorganic & Medicinal Chemistry Letters     Hybrid Journal   (Followers: 88)
Bioorganic Chemistry     Hybrid Journal   (Followers: 10)
Biopolymers     Hybrid Journal   (Followers: 18)
Biosensors     Open Access   (Followers: 4)
Biotechnic and Histochemistry     Hybrid Journal   (Followers: 1)
Bitácora Digital     Open Access  
Boletin de la Sociedad Chilena de Quimica     Open Access  
Bulletin of Institute of Chemistry and Chemical Technology, Mongolian Academy of Sciences     Open Access  
Bulletin of the Chemical Society of Ethiopia     Open Access   (Followers: 1)
Bulletin of the Chemical Society of Japan     Full-text available via subscription   (Followers: 26)
Bulletin of the Korean Chemical Society     Hybrid Journal   (Followers: 1)
C - Journal of Carbon Research     Open Access   (Followers: 5)
Cakra Kimia (Indonesian E-Journal of Applied Chemistry)     Open Access  
Canadian Association of Radiologists Journal     Full-text available via subscription   (Followers: 2)
Canadian Journal of Chemistry     Hybrid Journal   (Followers: 13)
Canadian Mineralogist     Full-text available via subscription   (Followers: 7)
Carbohydrate Polymer Technologies and Applications     Open Access   (Followers: 3)
Carbohydrate Polymers     Hybrid Journal   (Followers: 13)
Carbohydrate Research     Hybrid Journal   (Followers: 26)
Carbon     Hybrid Journal   (Followers: 76)
Catalysis Reviews: Science and Engineering     Hybrid Journal   (Followers: 9)
Catalysis Science and Technology     Hybrid Journal   (Followers: 13)
Catalysis Surveys from Asia     Hybrid Journal   (Followers: 4)
Catalysts     Open Access   (Followers: 14)
Cell Reports Physical Science     Open Access  
Cellulose     Hybrid Journal   (Followers: 17)
Cereal Chemistry     Full-text available via subscription   (Followers: 6)
ChemBioEng Reviews     Full-text available via subscription   (Followers: 3)
ChemCatChem     Hybrid Journal   (Followers: 11)
Chemical and Engineering News     Free   (Followers: 25)
Chemical Bulletin of Kazakh National University     Open Access  
Chemical Communications     Full-text available via subscription   (Followers: 88)
Chemical Engineering Research and Design     Hybrid Journal   (Followers: 28)
Chemical Physics Letters : X     Open Access   (Followers: 4)
Chemical Research in Chinese Universities     Hybrid Journal   (Followers: 4)
Chemical Research in Toxicology     Hybrid Journal   (Followers: 25)
Chemical Reviews     Hybrid Journal   (Followers: 265)
Chemical Science     Open Access   (Followers: 44)
Chemical Science International Journal     Open Access   (Followers: 1)
Chemical Technology     Open Access   (Followers: 71)
Chemical Vapor Deposition     Hybrid Journal   (Followers: 5)
Chemie in Unserer Zeit     Hybrid Journal   (Followers: 56)
Chemie-Ingenieur-Technik (Cit)     Hybrid Journal   (Followers: 23)
ChemInform     Hybrid Journal   (Followers: 9)
Chemistry     Open Access  
Chemistry & Biodiversity     Hybrid Journal   (Followers: 7)
Chemistry & Biology     Full-text available via subscription   (Followers: 31)
Chemistry & Industry     Full-text available via subscription   (Followers: 8)
Chemistry - A European Journal     Hybrid Journal   (Followers: 224)
Chemistry - An Asian Journal     Hybrid Journal   (Followers: 20)
Chemistry Africa : A Journal of the Tunisian Chemical Society     Hybrid Journal  
Chemistry and Materials Research     Open Access   (Followers: 24)
Chemistry Central Journal     Open Access   (Followers: 5)
Chemistry Education Research and Practice     Free   (Followers: 8)
Chemistry Education Review     Open Access   (Followers: 5)
Chemistry in Education     Open Access   (Followers: 9)
Chemistry Letters     Full-text available via subscription   (Followers: 49)
Chemistry of Heterocyclic Compounds     Hybrid Journal   (Followers: 4)
Chemistry of Materials     Hybrid Journal   (Followers: 336)
Chemistry of Natural Compounds     Hybrid Journal   (Followers: 10)
Chemistry World     Full-text available via subscription   (Followers: 20)
Chemistry-Didactics-Ecology-Metrology     Open Access   (Followers: 1)
ChemistryOpen     Open Access   (Followers: 1)
ChemistrySelect     Hybrid Journal  
Chemistry–Methods     Open Access   (Followers: 2)
Chemkon - Chemie Konkret, Forum Fuer Unterricht Und Didaktik     Hybrid Journal  
ChemNanoMat     Hybrid Journal   (Followers: 1)
Chemoecology     Hybrid Journal   (Followers: 3)
Chemometrics and Intelligent Laboratory Systems     Hybrid Journal   (Followers: 14)
Chemosensors     Open Access   (Followers: 1)
ChemPhotoChem     Hybrid Journal  
ChemPhysChem     Hybrid Journal   (Followers: 14)
ChemPlusChem     Hybrid Journal   (Followers: 2)
Chempublish Journal     Open Access   (Followers: 1)
ChemSystemsChem     Hybrid Journal   (Followers: 2)
ChemTexts     Hybrid Journal   (Followers: 1)
CHIMIA International Journal for Chemistry     Open Access   (Followers: 2)
Chinese Journal of Chemistry     Hybrid Journal   (Followers: 6)
Chinese Journal of Polymer Science     Hybrid Journal   (Followers: 13)
Chromatographia     Hybrid Journal   (Followers: 22)
Chromatography     Open Access   (Followers: 3)
Chromatography Research International     Open Access   (Followers: 5)
Ciencia     Open Access   (Followers: 1)
Clay Minerals     Hybrid Journal   (Followers: 9)
Cogent Chemistry     Open Access   (Followers: 3)
Colloid and Interface Science Communications     Open Access  
Colloid and Polymer Science     Hybrid Journal   (Followers: 12)
Colloids and Interfaces     Open Access  
Colloids and Surfaces B: Biointerfaces     Hybrid Journal   (Followers: 8)
Combinatorial Chemistry & High Throughput Screening     Hybrid Journal   (Followers: 4)
Combustion Science and Technology     Hybrid Journal   (Followers: 24)
Comments on Inorganic Chemistry: A Journal of Critical Discussion of the Current Literature     Hybrid Journal   (Followers: 2)

        1 2 3 4 | Last

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Journal Prestige (SJR): 0.829
Citation Impact (citeScore): 4
Number of Followers: 4  

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ISSN (Print) 2079-6374
Published by MDPI Homepage  [238 journals]
  • Biosensors, Vol. 11, Pages 305: Immunosensing Based on Optical Fiber
           Technology: Recent Advances

    • Authors: Maria Simone Soares, Miguel Vidal, Nuno F. Santos, Florinda M. Costa, Carlos Marques, Sónia O. Pereira, Cátia Leitão
      First page: 305
      Abstract: The evolution of optical fiber technology has revolutionized a variety of fields, from optical transmission to environmental monitoring and biomedicine, given their unique properties and versatility. For biosensing purposes, the light guided in the fiber core is exposed to the surrounding media where the analytes of interest are detected by different techniques, according to the optical fiber configuration and biofunctionalization strategy employed. These configurations differ in manufacturing complexity, cost and overall performance. The biofunctionalization strategies can be carried out directly on bare fibers or on coated fibers. The former relies on interactions between the evanescent wave (EW) of the fiber and the analyte of interest, whereas the latter can comprise plasmonic methods such as surface plasmon resonance (SPR) and localized SPR (LSPR), both originating from the interaction between light and metal surface electrons. This review presents the basics of optical fiber immunosensors for a broad audience as well as the more recent research trends on the topic. Several optical fiber configurations used for biosensing applications are highlighted, namely uncladded, U-shape, D-shape, tapered, end-face reflected, fiber gratings and special optical fibers, alongside practical application examples. Furthermore, EW, SPR, LSPR and biofunctionalization strategies, as well as the most recent advances and applications of immunosensors, are also covered. Finally, the main challenges and an outlook over the future direction of the field is presented.
      Citation: Biosensors
      PubDate: 2021-08-30
      DOI: 10.3390/bios11090305
      Issue No: Vol. 11, No. 9 (2021)
  • Biosensors, Vol. 11, Pages 306: A Smart Core-Crosslinked Supramolecular
           Drug Delivery System (SDDS) Enabled by Pendant Cyclodextrins Encapsulation
           of Drug Dimers via Host-Guest Interaction

    • Authors: Xin Xing, Zhijun Guo, Yue Su, Zhen Yang, Jiwen Qian, Chunlai Tu, Lijuan Zhu, Feng Xu
      First page: 306
      Abstract: Owing to poor aqueous solubility and low delivery efficiency, most of anti-cancer chemodrugs depend on various smart drug delivery platforms to enhance the treatment efficacy. Herein, a stimuli-responsive supramolecular drug delivery system (SDDS) is developed based on polymeric cyclodextrins (PCD) which crosslinked by stimuli-cleavable drug dimers via host-guest interaction. PEGylated PCD was precisely controlled synthesized by ring-opening polymerization and azide-alkyne click chemistry, and two doxorubicins (DOX) were linked with a disulfide bond to form a drug dimer (ss-DOX). They then co-assembled into supramolecular micelles. Drug dimers were utilized as cross-linkers to stabilize the micelles. The drug loading efficiency was very high that could be up to 98%. The size and morphology were measured by DLS and TEM. Owing to the disulfide bonds of drug dimers, these supramolecular micelles were dissociated by treating with dithiothreitol (DTT). In the meanwhile, the free DOXs were recovered and released from cavities of cyclodextrins because of dynamic equilibrium and hydrophilicity changes. The release profile was studied under mimic physiological conditions. Furthermore, in vitro cytotoxicity study showed excellent anti-cancer efficacy of reduced-responsive supramolecular polymeric micelles. Therefore, it can be served as a safe and stimuli-responsive SDDS for cancer therapy.
      Citation: Biosensors
      PubDate: 2021-08-30
      DOI: 10.3390/bios11090306
      Issue No: Vol. 11, No. 9 (2021)
  • Biosensors, Vol. 11, Pages 307: Super-Resolution Imaging with Graphene

    • Authors: Xiaoxiao Jiang, Lu Kong, Yu Ying, Qiongchan Gu, Jiangtao Lv, Zhigao Dai, Guangyuan Si
      First page: 307
      Abstract: Super-resolution optical imaging is a consistent research hotspot for promoting studies in nanotechnology and biotechnology due to its capability of overcoming the diffraction limit, which is an intrinsic obstacle in pursuing higher resolution for conventional microscopy techniques. In the past few decades, a great number of techniques in this research domain have been theoretically proposed and experimentally demonstrated. Graphene, a special two-dimensional material, has become the most meritorious candidate and attracted incredible attention in high-resolution imaging domain due to its distinctive properties. In this article, the working principle of graphene-assisted imaging devices is summarized, and recent advances of super-resolution optical imaging based on graphene are reviewed for both near-field and far-field applications.
      Citation: Biosensors
      PubDate: 2021-08-30
      DOI: 10.3390/bios11090307
      Issue No: Vol. 11, No. 9 (2021)
  • Biosensors, Vol. 11, Pages 308: In-Situ Monitoring of Real-Time
           Loop-Mediated Isothermal Amplification with QCM: Detecting Listeria

    • Authors: Sirirat Wachiralurpan, Isaratat Phung-On, Narong Chanlek, Supatra Areekit, Kosum Chansiri, Peter A. Lieberzeit
      First page: 308
      Abstract: Functionalized DNA sequences are promising sensing elements to combine with transducers for bio-sensing specific target microbes. As an application example, this paper demonstrates in situ detection of loop-mediated isothermal amplification products by hybridizing them with thiolated-ssDNA covalently anchored on the electrodes of a quartz crystal microbalance (QCM). Such hybridization leads to a frequency signal, which is suitable for monitoring real-time LAMP amplification based on mass-sensing: it detects interactions between the complementary nucleobases of LAMP products in solution and the thiolated-ssDNA probe sequence on the gold surface. Target DNA LAMP products cause irreversible frequency shifts on the QCM surfaces during hybridization in the kHz range, which result from both changes in mass and charge on the electrode surface. In order to confirm the LAMP assay working in the QCM sensing system at elevated temperature, the sky blue of positive LAMP products solution was achieved by using the Hydroxy Naphthol Blue (HNB) and agarose gel electrophoresis. Since on-QCM sensing of DNA hybridization leads to irreversible sensor responses, this work shows characterization by X-ray photoelectron spectroscopy (XPS) core spectra of S2p, N1s, Mg1s, P2p and C1s. XPS results confirmed that indeed both DNA and by-products of LAMP attached to the surface. Listeria monocytogenes DNA served to study in-situ detection of amplified LAMP products on DNA-functionalized surfaces.
      Citation: Biosensors
      PubDate: 2021-08-31
      DOI: 10.3390/bios11090308
      Issue No: Vol. 11, No. 9 (2021)
  • Biosensors, Vol. 11, Pages 309: Olfactory Optogenetics: Light Illuminates
           the Chemical Sensing Mechanisms of Biological Olfactory Systems

    • Authors: Ping Zhu, Yulan Tian, Yating Chen, Wei Chen, Ping Wang, Liping Du, Chunsheng Wu
      First page: 309
      Abstract: The mammalian olfactory system has an amazing ability to distinguish thousands of odorant molecules at the trace level. Scientists have made great achievements on revealing the olfactory sensing mechanisms in decades; even though many issues need addressing. Optogenetics provides a novel technical approach to solve this dilemma by utilizing light to illuminate specific part of the olfactory system; which can be used in all corners of the olfactory system for revealing the olfactory mechanism. This article reviews the most recent advances in olfactory optogenetics devoted to elucidate the mechanisms of chemical sensing. It thus attempts to introduce olfactory optogenetics according to the structure of the olfactory system. It mainly includes the following aspects: the sensory input from the olfactory epithelium to the olfactory bulb; the influences of the olfactory bulb (OB) neuron activity patterns on olfactory perception; the regulation between the olfactory cortex and the olfactory bulb; and the neuromodulation participating in odor coding by dominating the olfactory bulb. Finally; current challenges and future development trends of olfactory optogenetics are proposed and discussed.
      Citation: Biosensors
      PubDate: 2021-08-31
      DOI: 10.3390/bios11090309
      Issue No: Vol. 11, No. 9 (2021)
  • Biosensors, Vol. 11, Pages 310: State of the Art on the SARS-CoV-2 Toolkit
           for Antigen Detection: One Year Later

    • Authors: Laura Fabiani, Veronica Caratelli, Luca Fiore, Viviana Scognamiglio, Amina Antonacci, Silvia Fillo, Riccardo De Santis, Anella Monte, Manfredo Bortone, Danila Moscone, Florigio Lista, Fabiana Arduini
      First page: 310
      Abstract: The recent global events of COVID-19 in 2020 have alerted the world to the risk of viruses and their impacts on human health, including their impacts in the social and economic sectors. Rapid tests are urgently required to enable antigen detection and thus to facilitate rapid and simple evaluations of contagious individuals, with the overriding goal to delimitate spread of the virus among the population. Many efforts have been achieved in recent months through the realization of novel diagnostic tools for rapid, affordable, and accurate analysis, thereby enabling prompt responses to the pandemic infection. This review reports the latest results on electrochemical and optical biosensors realized for the specific detection of SARS-CoV-2 antigens, thus providing an overview of the available diagnostics tested and marketed for SARS-CoV-2 antigens as well as their pros and cons.
      Citation: Biosensors
      PubDate: 2021-08-31
      DOI: 10.3390/bios11090310
      Issue No: Vol. 11, No. 9 (2021)
  • Biosensors, Vol. 11, Pages 311: MoS2/PPy Nanocomposite as a Transducer for
           Electrochemical Aptasensor of Ampicillin in River Water

    • Authors: M. Hamami, M. Bouaziz, N. Raouafi, A. Bendounan, H. Korri-Youssoufi
      First page: 311
      Abstract: We report the design of an electrochemical aptasensor for ampicillin detection, which is an antibiotic widely used in agriculture and considered to be a water contaminant. We studied the transducing potential of nanostructure composed of MoS2 nanosheets and conductive polypyrrole nanoparticles (PPyNPs) cast on a screen-printed electrode. Fine chemistry is developed to build the biosensors entirely based on robust covalent immobilizations of naphthoquinone as a redox marker and the aptamer. The structural and morphological properties of the nanocomposite were studied by SEM, AFM, and FT-IR. High-resolution XPS measurements demonstrated the formation of a binding between the two nanomaterials and energy transfer affording the formation of heterostructure. Cyclic voltammetry and electrochemical impedance spectroscopy were used to analyze their electrocatalytic properties. We demonstrated that the nanocomposite formed with PPyNPs and MoS2 nanosheets has electro-catalytic properties and conductivity leading to a synergetic effect on the electrochemical redox process of the redox marker. Thus, a highly sensitive redox process was obtained that could follow the recognition process between the apatamer and the target. An amperometric variation of the naphthoquinone response was obtained regarding the ampicillin concentration with a limit of detection (LOD) of 10 pg/L (0.28 pM). A high selectivity towards other contaminants was demonstrated with this biosensor and the analysis of real river water samples without any treatment showed good recovery results thanks to the antifouling properties. This biosensor can be considered a promising device for the detection of antibiotics in the environment as a point-of-use system.
      Citation: Biosensors
      PubDate: 2021-09-01
      DOI: 10.3390/bios11090311
      Issue No: Vol. 11, No. 9 (2021)
  • Biosensors, Vol. 11, Pages 312: Real-Time Detection of Tumor Cells during
           Capture on a Filter Element Significantly Enhancing Detection Rate

    • Authors: Astrid Lux, Hannah Bott, Nisar Peter Malek, Roland Zengerle, Tanja Maucher, Jochen Hoffmann
      First page: 312
      Abstract: Circulating tumor cells (CTCs) that enter the bloodstream play an important role in the formation of metastases. The prognostic significance of CTCs as biomarkers obtained from liquid biopsies is intensively investigated and requires accurate methods for quantification. The purpose of this study was the capture of CTCs on an optically accessible surface for real-time quantification. A filtration device was fabricated from a transparent material so that capturing of cells could be observed microscopically. Blood samples were spiked with stained tumor cells and the sample was filtrated using a porous structure with pore sizes of 7.4 µm. The possible removal of lysed erythrocytes and the retention of CTCs were assessed. The filtration process was observed in real-time using fluorescence microscopy, whereby arriving cells were counted in order to determine the number of CTCs present in the blood. Through optimization of the microfluidic channel design, the cell retention rate could be increased by 13% (from 76% ± 7% to 89% ± 5%). Providing the possibility for real-time detection significantly improved quantification efficiency even for the smallest cells evaluated. While end-point evaluation resulted in a detection rate of 63% ± 3% of the spiked cells, real-time evaluation led to an increase of 21% to 84% ± 4%. The established protocol provides an advantageous and efficient method for integration of fully automated sample preparation and CTC quantification into a lab-on-a-chip system.
      Citation: Biosensors
      PubDate: 2021-09-03
      DOI: 10.3390/bios11090312
      Issue No: Vol. 11, No. 9 (2021)
  • Biosensors, Vol. 11, Pages 313: Cocaine Detection by a Laser-Induced
           Immunofluorometric Biosensor

    • Authors: Martin Paul, Robert Tannenberg, Georg Tscheuschner, Marco Ponader, Michael G. Weller
      First page: 313
      Abstract: The trafficking of illegal drugs by criminal networks at borders, harbors, or airports is an increasing issue for public health as these routes ensure the main supply of illegal drugs. The prevention of drug smuggling, including the installation of scanners and other analytical devices to detect small traces of drugs within a reasonable time frame, remains a challenge. The presented immunosensor is based on a monolithic affinity column with a large excess of immobilized hapten, which traps fluorescently labeled antibodies as long as the analyte cocaine is absent. In the presence of the drug, some binding sites of the antibody will be blocked, which leads to an immediate breakthrough of the labeled protein, detectable by highly sensitive laser-induced fluorescence with the help of a Peltier-cooled complementary metal-oxide-semiconductor (CMOS) camera. Liquid handling is performed with high-precision syringe pumps and microfluidic chip-based mixing devices and flow cells. The biosensor achieved limits of detection of 7 ppt (23 pM) of cocaine with a response time of 90 s and a total assay time below 3 min. With surface wipe sampling, the biosensor was able to detect 300 pg of cocaine. This immunosensor belongs to the most sensitive and fastest detectors for cocaine and offers near-continuous analyte measurement.
      Citation: Biosensors
      PubDate: 2021-09-03
      DOI: 10.3390/bios11090313
      Issue No: Vol. 11, No. 9 (2021)
  • Biosensors, Vol. 11, Pages 314: Parallelizable Microfluidic Platform to
           Model and Assess In Vitro Cellular Barriers: Technology and Application to
           Study the Interaction of 3D Tumor Spheroids with Cellular Barriers

    • Authors: Arya Lekshmi Nair, Lena Mesch, Ingo Schulz, Holger Becker, Julia Raible, Heiko Kiessling, Simon Werner, Ulrich Rothbauer, Christian Schmees, Marius Busche, Sebastian Trennheuser, Gert Fricker, Martin Stelzle
      First page: 314
      Abstract: Endothelial and epithelial cellular barriers play a vital role in the selective transport of solutes and other molecules. The properties and function of these barriers are often affected in case of inflammation and disease. Modelling cellular barriers in vitro can greatly facilitate studies of inflammation, disease mechanisms and progression, and in addition, can be exploited for drug screening and discovery. Here, we report on a parallelizable microfluidic platform in a multiwell plate format with ten independent cell culture chambers to support the modelling of cellular barriers co-cultured with 3D tumor spheroids. The microfluidic platform was fabricated by microinjection molding. Electrodes integrated into the chip in combination with a FT-impedance measurement system enabled transepithelial/transendothelial electrical resistance (TEER) measurements to rapidly assess real-time barrier tightness. The fluidic layout supports the tubeless and parallelized operation of up to ten distinct cultures under continuous unidirectional flow/perfusion. The capabilities of the system were demonstrated with a co-culture of 3D tumor spheroids and cellular barriers showing the growth and interaction of HT29 spheroids with a cellular barrier of MDCK cells.
      Citation: Biosensors
      PubDate: 2021-09-03
      DOI: 10.3390/bios11090314
      Issue No: Vol. 11, No. 9 (2021)
  • Biosensors, Vol. 11, Pages 315: Electrochemical Biosensors for Tracing
           Cyanotoxins in Food and Environmental Matrices

    • Authors: Antonella Miglione, Maria Napoletano, Stefano Cinti
      First page: 315
      Abstract: The adoption of electrochemical principles to realize on-field analytical tools for detecting pollutants represents a great possibility for food safety and environmental applications. With respect to the existing transduction mechanisms, i.e., colorimetric, fluorescence, piezoelectric etc., electrochemical mechanisms offer the tremendous advantage of being easily miniaturized, connected with low cost (commercially available) readers and unaffected by the color/turbidity of real matrices. In particular, their versatility represents a powerful approach for detecting traces of emerging pollutants such as cyanotoxins. The combination of electrochemical platforms with nanomaterials, synthetic receptors and microfabrication makes electroanalysis a strong starting point towards decentralized monitoring of toxins in diverse matrices. This review gives an overview of the electrochemical biosensors that have been developed to detect four common cyanotoxins, namely microcystin-LR, anatoxin-a, saxitoxin and cylindrospermopsin. The manuscript provides the readers a quick guide to understand the main electrochemical platforms that have been realized so far, and the presence of a comprehensive table provides a perspective at a glance.
      Citation: Biosensors
      PubDate: 2021-09-04
      DOI: 10.3390/bios11090315
      Issue No: Vol. 11, No. 9 (2021)
  • Biosensors, Vol. 11, Pages 316: Disposable Paper-Based Biosensors for the
           Point-of-Care Detection of Hazardous Contaminations—A Review

    • Authors: Mohammad Mahdi Bordbar, Azarmidokht Sheini, Pegah Hashemi, Ali Hajian, Hasan Bagheri
      First page: 316
      Abstract: The fast detection of trace amounts of hazardous contaminations can prevent serious damage to the environment. Paper-based sensors offer a new perspective on the world of analytical methods, overcoming previous limitations by fabricating a simple device with valuable benefits such as flexibility, biocompatibility, disposability, biodegradability, easy operation, large surface-to-volume ratio, and cost-effectiveness. Depending on the performance type, the device can be used to analyze the analyte in the liquid or vapor phase. For liquid samples, various structures (including a dipstick, as well as microfluidic and lateral flow) have been constructed. Paper-based 3D sensors are prepared by gluing and folding different layers of a piece of paper, being more user-friendly, due to the combination of several preparation methods, the integration of different sensor elements, and the connection between two methods of detection in a small set. Paper sensors can be used in chromatographic, electrochemical, and colorimetric processes, depending on the type of transducer. Additionally, in recent years, the applicability of these sensors has been investigated in various applications, such as food and water quality, environmental monitoring, disease diagnosis, and medical sciences. Here, we review the development (from 2010 to 2021) of paper methods in the field of the detection and determination of toxic substances.
      Citation: Biosensors
      PubDate: 2021-09-04
      DOI: 10.3390/bios11090316
      Issue No: Vol. 11, No. 9 (2021)
  • Biosensors, Vol. 11, Pages 317: Rapid Detection of Pathogenic Bacteria by
           the Naked Eye

    • Authors: Karthikeyan Kandasamy, Miftakhul Jannatin, Yu-Chie Chen
      First page: 317
      Abstract: Escherichia coli O157:H7 and Staphylococcus aureus are common pathogens. Gram-negative bacteria, such as E. coli, contain high concentrations of endogenous peroxidases, whereas Gram-positive bacteria, such as S. aureus, possess abundant endogenous catalases. Colorless 3,5,3′,5′-tetramethyl benzidine (TMB) changes to blue oxidized TMB in the presence of E. coli and a low concentration of H2O2 (e.g., ~11 mM) at pH of 3. Moreover, visible air bubbles containing oxygen are generated after S. aureus reacts with H2O2 at a high concentration (e.g., 180 mM) at pH of 3. A novel method for rapidly detecting the presence of bacteria on the surfaces of samples, on the basis of these two endogenous enzymatic reactions, was explored. Briefly, a cotton swab was used for collecting bacteria from the surfaces of samples, such as tomatoes and door handles, then two-step endogenous enzymatic reactions were carried out. In the first step, a cotton swab containing bacteria was immersed in a reagent comprising H2O2 (11.2 mM) and TMB for 25 min. In the second step, the swab was dipped further in H2O2 (180 mM) at pH 3 for 5 min. Results showed that the presence of Gram-negative bacteria, such as E. coli with a cell number of ≥ ~105, and Gram-positive bacteria, such as S. aureus with a cell number of ≥ ~106, can be visually confirmed according to the appearance of the blue color in the swab and the formation of air bubbles in the reagent solution, respectively, within ~30 min. To improve visual sensitivity, we dipped the swab carrying the bacteria in a vial containing a growth broth, incubated it for ~4 h, and carried out the two-stage reaction steps. Results showed that bluish swabs resulting from the presence of E. coli O157: H7 with initial cell numbers of ≥ ~34 were obtained, whereas air bubbles were visible in the samples containing S. aureus with initial cell numbers of ≥ ~8.5 × 103.
      Citation: Biosensors
      PubDate: 2021-09-06
      DOI: 10.3390/bios11090317
      Issue No: Vol. 11, No. 9 (2021)
  • Biosensors, Vol. 11, Pages 318: Objectively Measured Physical Activity in
           Patients with Coronary Artery Disease: A Cross-Validation Study

    • Authors: Tim Kambic, Nejc Šarabon, Vedran Hadžić, Mitja Lainscak
      First page: 318
      Abstract: Physical activity (PA) and sedentary behavior (SB) levels in healthy adults are predominately based on self-reporting measures, which generally overestimate PA but underestimate SB. Patients with coronary artery disease (CAD) eligible for cardiac rehabilitation (CR) follow an individualized program; thus, objective assessment of physical performance and regular daily activity is required. This study aimed to compare self-reported and objectively measured PA and SB in patients with CAD prior to out-patient CR. We included 91 patients with CAD and assessed their PA with an accelerometer for 8 days prior to CR, along with the short form of the international physical activity questionnaire. We found that most patients were sedentary (61%, ~8 h/day), and on average performed 63 min/day of moderate-to-vigorous-intensity physical activity (MVPA). Males performed less daily light-intensity physical activity (−5%, p = 0.011) and performed more MVPA (+2%, p = 0.002) compared to females. Maximal aerobic capacity was significantly associated with MVPA (Spearman rho = 0.483, p < 0.001) and MVPA >10 min bouts (Spearman rho = 0.391, p < 0.001). Self-reported measures overestimated MVPA (total MVPA, +108 min/day, p < 0.001; MVPA >10 min bouts, +152 min, p < 0.001) and underestimated SB (−174 min/day, p < 0.001) compared to objective measures. There was no significant correlation between methods in MVPA (Spearman rho = 0.147, p = 0.165)), MVPA >10 min bouts (Spearman rho = −0.059, p = 576), and SB (Spearman rho = 0.139, p = 0.187). Quantitative analysis demonstrated the huge proportional bias for MVPA, MVPA >10 min bouts, and SB. Our findings demonstrate that self-reported physical activity provides inaccurate estimates of MVPA and SB in patients with CAD entering the ambulatory CR. This strongly supports the more objective assessments of daily PA, preferably using an accelerometer.
      Citation: Biosensors
      PubDate: 2021-09-06
      DOI: 10.3390/bios11090318
      Issue No: Vol. 11, No. 9 (2021)
  • Biosensors, Vol. 11, Pages 319: The Current State of Traumatic Brain
           Injury Biomarker Measurement Methods

    • Authors: Alyse D. Krausz, Frederick K. Korley, Mark A. Burns
      First page: 319
      Abstract: Traumatic brain injury (TBI) is associated with high rates of morbidity and mortality partially due to the limited tools available for diagnosis and classification. Measuring panels of protein biomarkers released into the bloodstream after injury has been proposed to diagnose TBI, inform treatment decisions, and monitor the progression of the injury. Being able to measure these protein biomarkers at the point-of-care would enable assessment of TBIs from the point-of-injury to the patient’s hospital bedside. In this review, we provide a detailed discussion of devices reported in the academic literature and available on the market that have been designed to measure TBI protein biomarkers in various biofluids and contexts. We also assess the challenges associated with TBI biomarker measurement devices and suggest future research directions to encourage translation of these devices to clinical use.
      Citation: Biosensors
      PubDate: 2021-09-07
      DOI: 10.3390/bios11090319
      Issue No: Vol. 11, No. 9 (2021)
  • Biosensors, Vol. 11, Pages 320: A Variable Height Microfluidic Device for
           Multiplexed Immunoassay Analysis of Traumatic Brain Injury Biomarkers

    • Authors: Alyse D. Krausz, Frederick K. Korley, Mark A. Burns
      First page: 320
      Abstract: Traumatic brain injury (TBI) is a leading cause of global morbidity and mortality, partially due to the lack of sensitive diagnostic methods and efficacious therapies. Panels of protein biomarkers have been proposed as a way of diagnosing and monitoring TBI. To measure multiple TBI biomarkers simultaneously, we present a variable height microfluidic device consisting of a single channel that varies in height between the inlet and outlet and can passively multiplex bead-based immunoassays by trapping assay beads at the point where their diameter matches the channel height. We developed bead-based quantum dot-linked immunosorbent assays (QLISAs) for interleukin-6 (IL-6), glial fibrillary acidic protein (GFAP), and interleukin-8 (IL-8) using DynabeadsTM M-450, M-270, and MyOneTM, respectively. The IL-6 and GFAP QLISAs were successfully multiplexed using a variable height channel that ranged in height from ~7.6 µm at the inlet to ~2.1 µm at the outlet. The IL-6, GFAP, and IL-8 QLISAs were also multiplexed using a channel that ranged in height from ~6.3 µm at the inlet to ~0.9 µm at the outlet. Our system can keep pace with TBI biomarker discovery and validation, as additional protein biomarkers can be multiplexed simply by adding in antibody-conjugated beads of different diameters.
      Citation: Biosensors
      PubDate: 2021-09-07
      DOI: 10.3390/bios11090320
      Issue No: Vol. 11, No. 9 (2021)
  • Biosensors, Vol. 11, Pages 321: Simultaneous Detection of Dihydroxybenzene
           Isomers Using Electrochemically Reduced Graphene Oxide-Carboxylated Carbon
           Nanotubes/Gold Nanoparticles Nanocomposite

    • Authors: Angélica Domínguez-Aragón, Rocio B. Dominguez, Erasto Armando Zaragoza-Contreras
      First page: 321
      Abstract: An electrochemical sensor based on electrochemically reduced graphene oxide (ErGO), carboxylated carbon nanotubes (cMWCNT), and gold nanoparticles (AuNPs) (GCE/ErGO-cMWCNT/AuNPs) was developed for the simultaneous detection of dihidroxybenzen isomers (DHB) hydroquinone (HQ), catechol (CC), and resorcinol (RS) using differential pulse voltammetry (DPV). The fabrication and optimization of the system were evaluated with Raman Spectroscopy, SEM, cyclic voltammetry, and DPV. Under optimized conditions, the GCE/ErGO-cMWCNT/AuNPs sensor exhibited a linear concentration range of 1.2–170 μM for HQ and CC, and 2.4–400 μM for RS with a detection limit of 0.39 μM, 0.54 μM, and 0.61 μM, respectively. When evaluated in tap water and skin-lightening cream, DHB multianalyte detection showed an average recovery rate of 107.11% and 102.56%, respectively. The performance was attributed to the synergistic effects of the 3D network formed by the strong π–π stacking interaction between ErGO and cMWCNT, combined with the active catalytic sites of AuNPs. Additionally, the cMWCNT provided improved electrocatalytic properties associated with the carboxyl groups that facilitate the adsorption of the DHB and the greater amount of active edge planes. The proposed GCE/ErGO-cMWCNT/AuNPs sensor showed a great potential for the simultaneous, precise, and easy-to-handle detection of DHB in complex samples with high sensitivity.
      Citation: Biosensors
      PubDate: 2021-09-07
      DOI: 10.3390/bios11090321
      Issue No: Vol. 11, No. 9 (2021)
  • Biosensors, Vol. 11, Pages 322: The Kinetic and Analytical Aspects of
           Enzyme Competitive Inhibition: Sensing of Tyrosinase Inhibitors

    • Authors: Raouia Attaallah, Aziz Amine
      First page: 322
      Abstract: An amperometric biosensor based on tyrosinase, immobilized onto a carbon black paste electrode using glutaraldehyde and BSA was constructed to detect competitive inhibitors. Three inhibitors were used in this study: benzoic acid, sodium azide, and kojic acid, and the obtained values for fifty percent of inhibition (IC50) were 119 µM, 1480 µM, and 30 µM, respectively. The type of inhibition can also be determined from the curve of the degree of inhibition by considering the shift of the inhibition curves. Amperometric experiments were performed with a biosensor polarized at the potential −0.15 V vs. Ag/AgCl and using 0.1 M phosphate buffer (pH 6.8) as an electrolyte. Under optimized conditions, the proposed biosensor showed a linear amperometric response toward catechol detection from 0.5 µM to 38 µM with a detection limit of 0.35 µM (S/N = 3), and its sensitivity was 66.5 mA M−1 cm−2. Moreover, the biosensor exhibited a good storage stability. Conversely, a novel graphical plot for the determination of reversible competitive inhibition was represented for free tyrosinase. The graph consisted of plotting the half-time reaction (t1/2) as a function of the inhibitor concentration at various substrate concentrations. This innovative method relevance was demonstrated in the case of kojic acid using a colorimetric bioassay relying on tyrosinase inhibition. The results showed that the t1/2 provides an extended linear range of tyrosinase inhibitors.
      Citation: Biosensors
      PubDate: 2021-09-08
      DOI: 10.3390/bios11090322
      Issue No: Vol. 11, No. 9 (2021)
  • Biosensors, Vol. 11, Pages 323: Voltammetric Electrochemical Sensor for
           Phylogenetic Study in Acer Linn.

    • Authors: Qingwei Zhou, Kewei Liu, Xiaolong Li, Yonghua Gu, Yuhong Zheng, Boyuan Fan, Weihong Wu
      First page: 323
      Abstract: Acer Linn. is a highly divergent species morphology in the maple family (Aceraceae). It is one of the genera facing a very difficult taxonomic situation. The phylogeny of the genus and the taxonomic system under the genus remain unclear. The use of electrochemical fingerprints for plant phylogenetic study is an emerging application in biosensors. In this work, leaves of 18 species of Acer Linn. with an exo-taxa were selected for electrochemical fingerprint recording. Two different conditions were used for improving the data abundance. The fingerprint of all species showed a series of oxidation peaks. These peaks can be ascribed to the oxidation of flavonols, phenolic acids, procyanidins, alkaloids, and pigments in plant tissue. These electrochemical fingerprints can be used for the identification of plant species. We also performed a phylogenetic study with data from electrochemical fingerprinting. The phylogenetic tree of Acer is divided into three main clades. The result is in full agreement with A. shangszeense var. anfuense, A. pictum subsp. mono, A. amplum, A. truncatum, and A. miaotaiense, belonging to the subsection Platanoidea. A. nikoense and A. griseum were clustered together in the dendrogram. Another group that fits the traditional classification results is in the subsection Integrifolia.
      Citation: Biosensors
      PubDate: 2021-09-08
      DOI: 10.3390/bios11090323
      Issue No: Vol. 11, No. 9 (2021)
  • Biosensors, Vol. 11, Pages 324: Binding Analysis of Functionalized
           Multimode Optical-Fiber Sandwich-like Structure with Organic Polymer and
           Its Sensing Application for Humidity and Breath Monitoring

    • Authors: Daniel Jauregui-Vazquez, Paulina Lozano-Sotomayor, Jorge Emmanuel Mejía-Benavides, Erik Díaz-Cervantes
      First page: 324
      Abstract: In recent years, the chemical modification of optical fibers (OFs) has facilitated the manufacture of sensors because OFs can identify several analytes present in aqueous solutions or gas phases. Nevertheless, it is imperative better to understand the chemical interactions in this molecular system to generate low-cost and efficient sensors. This work presents a theoretical and experimental study of organic polymeric functionalized OF structures and proposes a cost-effective alternative to monitor breathing and humidity. The device is based on silicon optical fibers functionalized with (3-Aminopropyl) triethoxysilane (APTES) and alginate. The theoretical analysis is carried out to validate the activation of the silicon dioxide fiber surface; moreover, the APTES–alginate layer is discussed. The computational simulation suggests that water can be absorbed by alginate, specifically by the calcium atom linked to the carboxylic acid group of the alginate. The analysis also demonstrates a higher electrostatic interaction between the water and the OF–APTES–alginate system; this interaction alters the optical fiber activated surface’s refractive index, resulting in transmission power variation. The humidity analysis shows a sensitivity of 3.1288 mV/RH, a time response close to 25 s, and a recovery time around 8 s. These results were achieved in the range of 50 to 95% RH. Moreover, the recovery and response time allow the human breath to be studied. The proposed mechanism or device is competitive with prior works, and the components involved made this sensor a cost-effective alternative for medical applications.
      Citation: Biosensors
      PubDate: 2021-09-08
      DOI: 10.3390/bios11090324
      Issue No: Vol. 11, No. 9 (2021)
  • Biosensors, Vol. 11, Pages 325: An Analytical Method Based on
           Electrochemical Sensor for the Assessment of Insect Infestation in Flour

    • Authors: Li Fu, Jiangwei Zhu, Hassan Karimi-Maleh
      First page: 325
      Abstract: Uric acid is an important indicator of the insect infestation assessment in flour. In this work, we propose a method for uric acid detection based on voltammetry. This technique is particularly considered for the physicochemical properties of flour and contains a simple pretreatment process to rapidly achieve extraction and adsorption of uric acid in flour. To achieve specific recognition of uric acid, graphene and poly(3,4-ethylenedioxythiophene) (PEDOT) were used for the adsorption and concentration of uric acid in flour. The adsorbed mixture was immobilized on the surface of a screen-printed electrode for highly sensitive detection of the uric acid. The results showed that electrocatalytic oxidation of uric acid could be achieved after adsorption by graphene and PEDOT. This electrocatalytic reaction allows its oxidation peak to be distinguished from those of other substances that commonly possess electrochemical activity. This voltammetry-based detection method is a portable and disposable analytical method. Because it is simple to operate, requires no professional training, and is inexpensive, it is a field analysis method that can be promoted.
      Citation: Biosensors
      PubDate: 2021-09-09
      DOI: 10.3390/bios11090325
      Issue No: Vol. 11, No. 9 (2021)
  • Biosensors, Vol. 11, Pages 326: A Portable Micro-Gas Chromatography with
           Integrated Photonic Crystal Slab Sensors on Chip

    • Authors: Priyanka Biswas, Chen Zhang, Yudong Chen, Zhonghe Liu, Seyedmohsen Vaziri, Weidong Zhou, Yuze Sun
      First page: 326
      Abstract: The miniaturization of gas chromatography (GC) systems has made it possible to utilize the analytical technique in various on-site applications to rapidly analyze complex gas samples. Various types of miniaturized sensors have been developed for micro-gas chromatography (µGC). However, the integration of an appropriate detector in µGC systems still faces a significant challenge. We present a solution to the problem through integration of µGC with photonic crystal slab (PCS) sensors using transfer printing technology. This integration offers an opportunity to utilize the advantages of optical sensors, such as high sensitivity and rapid response time, and at the same time, compensate for the lack of detection specificity from which label-free optical sensors suffer. We transfer printed a 2D defect free PCS on a borofloat glass, bonded it to a silicon microfluidic gas cell or directly to a microfabricated GC column, and then coated it with a gas responsive polymer. Realtime spectral shift in Fano resonance of the PCS sensor was used to quantitatively detect analytes over a mass range of three orders. The integrated µGC–PCS system was used to demonstrate separation and detection of a complex mixture of 10 chemicals. Fast separation and detection (4 min) and a low detection limit (ng) was demonstrated.
      Citation: Biosensors
      PubDate: 2021-09-09
      DOI: 10.3390/bios11090326
      Issue No: Vol. 11, No. 9 (2021)
  • Biosensors, Vol. 11, Pages 327: Immunosensor for Assessing the Welfare of
           Trainee Guide Dogs

    • Authors: Hannah Perkins, Michelle Higgins, Marinara Marcato, Paul Galvin, Sofia Rodrigues Teixeira
      First page: 327
      Abstract: Cortisol is a well established biomarker hormone that regulates many processes in the body and is widely referred to as the stress hormone. Cortisol can be used as a stress marker to allow for detection of stress levels in dogs during the training process. This test will indicate if they will handle the stress under the training or if they might be more suitable as an assistant or companion dog. An immunosensor for detection of cortisol was developed using electrochemical impedance spectroscopy (EIS). The sensor was characterized using chemical and topographical techniques. The sensor was calibrated and its sensitivity determined using a cortisol concentration range of 0.0005 to 50 μg/mL. The theoretical limit of detection was found to be 3.57 fg/mL. When the immunosensor was tested on canine saliva samples, cortisol was detected and measured within the relevant physiological ranges in dogs.
      Citation: Biosensors
      PubDate: 2021-09-09
      DOI: 10.3390/bios11090327
      Issue No: Vol. 11, No. 9 (2021)
  • Biosensors, Vol. 11, Pages 328: Origami Paper-Based Electrochemical
           (Bio)Sensors: State of the Art and Perspective

    • Authors: Noemi Colozza, Veronica Caratelli, Danila Moscone, Fabiana Arduini
      First page: 328
      Abstract: In the last 10 years, paper-based electrochemical biosensors have gathered attention from the scientific community for their unique advantages and sustainability vision. The use of papers in the design the electrochemical biosensors confers to these analytical tools several interesting features such as the management of the solution flow without external equipment, the fabrication of reagent-free devices exploiting the porosity of the paper to store the reagents, and the unprecedented capability to detect the target analyte in gas phase without any sampling system. Furthermore, cost-effective fabrication using printing technologies, including wax and screen-printing, combined with the use of this eco-friendly substrate and the possibility of reducing waste management after measuring by the incineration of the sensor, designate these type of sensors as eco-designed analytical tools. Additionally, the foldability feature of the paper has been recently exploited to design and fabricate 3D multifarious biosensors, which are able to detect different target analytes by using enzymes, antibodies, DNA, molecularly imprinted polymers, and cells as biocomponents. Interestingly, the 3D structure has recently boosted the self-powered paper-based biosensors, opening new frontiers in origami devices. This review aims to give an overview of the current state origami paper-based biosensors, pointing out how the foldability of the paper allows for the development of sensitive, selective, and easy-to-use smart and sustainable analytical devices.
      Citation: Biosensors
      PubDate: 2021-09-10
      DOI: 10.3390/bios11090328
      Issue No: Vol. 11, No. 9 (2021)
  • Biosensors, Vol. 11, Pages 329: A Vascular Intervention Assist Device
           Using Bi-Motional Roller Cartridge Structure and Clinical Evaluation

    • Authors: Jueun Choi, Sangeun Park, Young-Hak Kim, Youngjin Moon, Jaesoon Choi
      First page: 329
      Abstract: Conventional vascular intervention procedures present issues including X-ray exposure during operation, and an experience-dependent success rate and clinical outcome. This paper presents a novel robotic system using modularized bi-motional roller cartridge assemblies for robotic vascular interventions, specifically percutaneous coronary interventions (PCIs). The patient-side robot manipulates instruments such as the guiding catheter, guidewire, balloon/stent catheter, and diagnostic sensor catheter via commands from the user interface device, which is controlled by the physician. The proposed roller cartridge assembly can accommodate instruments of various sizes with an active clamping mechanism, and implements simultaneous translation and rotation motions. It also implements force feedback in the physician-side system, to effectively monitor the patient-side system’s status. The positioning accuracy and precision in using the robotic system showed satisfactory performance in a phantom-based test. It was also confirmed, through animal experiments and a pilot clinical trial, that the system demonstrates feasibility for clinical use.
      Citation: Biosensors
      PubDate: 2021-09-10
      DOI: 10.3390/bios11090329
      Issue No: Vol. 11, No. 9 (2021)
  • Biosensors, Vol. 11, Pages 330: Low-Power Two-Color Stimulated Emission
           Depletion Microscopy for Live Cell Imaging

    • Authors: Zhang, Gao, Wang, Guo, Zhu, Yang, Yan, Qu
      First page: 330
      Abstract: Stimulated emission depletion (STED) microscopy is a typical laser-scanning super-resolution imaging technology, the emergence of which has opened a new research window for studying the dynamic processes of live biological samples on a nanometer scale. According to the characteristics of STED, a high depletion power is required to obtain a high resolution. However, a high laser power can induce severe phototoxicity and photobleaching, which limits the applications for live cell imaging, especially in two-color STED super-resolution imaging. Therefore, we developed a low-power two-color STED super-resolution microscope with a single supercontinuum white-light laser. Using this system, we achieved low-power two-color super-resolution imaging based on digital enhancement technology. Lateral resolutions of 109 and 78 nm were obtained for mitochondria and microtubules in live cells, respectively, with 0.8 mW depletion power. These results highlight the great potential of the novel digitally enhanced two-color STED microscopy for long-term dynamic imaging of live cells.
      Citation: Biosensors
      PubDate: 2021-09-10
      DOI: 10.3390/bios11090330
      Issue No: Vol. 11, No. 9 (2021)
  • Biosensors, Vol. 11, Pages 331: Detection of the Complete ECG Waveform
           with Woven Textile Electrodes

    • Authors: Katya Arquilla, Laura Devendorf, Andrea K. Webb, Allison P. Anderson
      First page: 331
      Abstract: Wearable physiological monitoring systems are becoming increasingly prevalent in the push toward autonomous health monitoring and offer new modalities for playful and purposeful interaction within human computer interaction (HCI). Sensing systems that can be integrated into garments and, therefore, daily activities offer promising pathways toward ubiquitous integration. The electrocardiogram (ECG) signal is commonly monitored in healthcare and is increasingly utilized as a method of determining emotional and psychological state; however, the complete ECG waveform with the P, Q, R, S, and T peaks is not commonly used, due to the challenges associated with collecting the full waveform with wearable systems. We present woven textile electrodes as an option for garment-integrated ECG monitoring systems that are capable of capturing the complete ECG waveform. In this work, we present the changes in the peak detection performance caused by different sizes, patterns, and thread types with data from 10 human participants. These testing results provide empirically-derived guidelines for future woven textile electrodes, present a path forward for assessing design decisions, and highlight the importance of testing novel wearable sensor systems with more than a single individual.
      Citation: Biosensors
      PubDate: 2021-09-13
      DOI: 10.3390/bios11090331
      Issue No: Vol. 11, No. 9 (2021)
  • Biosensors, Vol. 11, Pages 332: Use of PEDOT:PSS/Graphene/Nafion Composite
           in Biosensors Based on Acetic Acid Bacteria

    • Authors: Yulia Plekhanova, Sergei Tarasov, Anatoly Reshetilov
      First page: 332
      Abstract: Immobilization of the biocomponent is one of the most important stages in the development of microbial biosensors. In this study, we examined the electrochemical properties of a novel PEDOT:PSS/graphene/Nafion composite used to immobilize Gluconobacter oxydans bacterial cells on the surface of a graphite screen-printed electrode. Bioelectrode responses to glucose in the presence of a redox mediator 2,6-dichlorophenolindophenol were studied. The presence of graphene in the composite reduced the negative effect of PEDOT:PSS on cells and improved its conductivity. The use of Nafion enabled maintaining the activity of acetic acid bacteria at the original level for 120 days. The sensitivity of the bioelectrode based on G. oxydans/PEDOT:PSS/graphene/Nafion composite was shown to be 22 μA × mM−1 × cm−2 within the linear range of glucose concentrations. The developed composite can be used both in designing bioelectrochemical microbial devices and in biotechnology productions for long-term immobilization of microorganisms.
      Citation: Biosensors
      PubDate: 2021-09-13
      DOI: 10.3390/bios11090332
      Issue No: Vol. 11, No. 9 (2021)
  • Biosensors, Vol. 11, Pages 333: Metal Ions Sensing by Biodots Prepared
           from DNA, RNA, and Nucleotides

    • Authors: Maofei Wang, Masaki Tsukamoto, Vladimir G. Sergeyev, Anatoly Zinchenko
      First page: 333
      Abstract: Nucleic acids that exhibit a high affinity toward noble and transition metal ions have attracted growing attention in the fields of metal ion sensing, toxic metal ion removal, and the construction of functional metal nanostructures. In this study, fluorescent nanoparticles (biodots) were synthesized from DNA, RNA, and RNA nucleotides (AMP, GMP, UMP, and CMP) using a hydrothermal (HT) method, in order to study their metal ion sensing characteristics. The fluorescent properties of biodots differ markedly between those prepared from purine and pyrimidine nucleobases. All biodots demonstrate a high sensitivity to the presence of mercury cations (Hg2+), while biodots prepared from DNA, RNA, and guanosine monophosphate (GMP) are also sensitive to Ag+ and Cu2+ ions, but to a lesser extent. The obtained results show that biodots inherit the metal ion recognition properties of nucleobases, while the nucleobase composition of biodot precursors affects metal ion sensitivity and selectivity. A linear response of biodot fluorescence to Hg2+ concentration in solution was observed for AMP and GMP biodots in the range 0–250 μM, which can be used for the analytic detection of mercury ion concentration. A facile paper strip test was also developed that allows visual detection of mercury ions in solutions.
      Citation: Biosensors
      PubDate: 2021-09-13
      DOI: 10.3390/bios11090333
      Issue No: Vol. 11, No. 9 (2021)
  • Biosensors, Vol. 11, Pages 334: Amperometric Sensing of Carbon Monoxide:
           Improved Sensitivity and Selectivity via Nanostructure-Controlled
           Electrodeposition of Gold

    • Authors: Taehui Kwon, Hee Young Mun, Sunghwa Seo, Areum Yu, Chongmok Lee, Youngmi Lee
      First page: 334
      Abstract: A series of gold (Au) nanostructures, having different morphologies, were fabricated for amperometric selective detection of carbon monoxide (CO), a biologically important signaling molecule. Au layers were electrodeposited from a precursor solution of 7 mM HAuCl4 with a constant deposition charge (0.04 C) at various deposition potentials. The obtained Au nanostructures became rougher and spikier as the deposition potential lowered from 0.45 V to 0.05 V (vs. Ag/AgCl). As prepared Au layers showed different hydrophobicity: The sharper morphology, the greater hydrophobicity. The Au deposit formed at 0.05 V had the sharpest shape and the greatest surface hydrophobicity. The sensitivity of an Au deposit for amperometric CO sensing was enhanced as the Au surface exhibits higher hydrophobicity. In fact, CO selectivity over common electroactive biological interferents (L-ascorbic acid, 4-acetamidophenol, 4-aminobutyric acid and nitrite) was improved eminently once the Au deposit became more hydrophobic. The most hydrophobic Au was also confirmed to sense CO exclusively without responding to nitric oxide, another similar gas signaling molecule, in contrast to a hydrophobic platinum (Pt) counterpart. This study presents a feasible strategy to enhance the sensitivity and selectivity for amperometric CO sensing via the fine control of Au electrode nanostructures.
      Citation: Biosensors
      PubDate: 2021-09-13
      DOI: 10.3390/bios11090334
      Issue No: Vol. 11, No. 9 (2021)
  • Biosensors, Vol. 11, Pages 335: An Electrochemical Enzyme Biosensor for
           Ammonium Detection in Aquaculture Using Screen-Printed Electrode Modified
           by Gold Nanoparticle/Polymethylene Blue

    • Authors: Cong Wang, Tan Wang, Zhen Li, Xianbao Xu, Xiaoshuan Zhang, Daoliang Li
      First page: 335
      Abstract: A SPEC/AuNPs/PMB modified electrode was prepared by electrodeposition and electro-polymerization. The electrochemical behavior of reduced nicotinamide adenine dinucleotide (NADH) on the surface of the modified electrode was studied by cyclic voltammetry. A certain amount of substrate and glutamate dehydrogenase (GLDH) were coated on the modified electrode to form a functional enzyme membrane. The ammonia nitrogen in the water sample could be calculated indirectly by measuring the consumption of NADH in the reaction. The results showed that the strength of electro-catalytic current signal was increased by two times; the catalytic oxidation potential was shifted to the left by 0.5 V, and the anti-interference ability of the sensor was enhanced. The optimum substrate concentration and enzyme loading were determined as 1.3 mM NADH, 28 mM α-Ketoglutarate and 2.0 U GLDH, respectively. The homemade ceramic heating plate controlled the working electrode to work at 37 °C. A pH compensation algorithm based on piecewise linear interpolation could reduce the measurement error to less than 3.29 μM. The biosensor exhibited good linearity in the range of 0~300 μM with a detection limit of 0.65 μM NH4+. Compared with standard Nessler’s method, the recoveries were 93.71~105.92%. The biosensor was found to be stable for at least 14 days when refrigerated and sealed at 4 °C.
      Citation: Biosensors
      PubDate: 2021-09-13
      DOI: 10.3390/bios11090335
      Issue No: Vol. 11, No. 9 (2021)
  • Biosensors, Vol. 11, Pages 336: Recent Advances in Electrochemical
           Biosensors: Applications, Challenges, and Future Scope

    • Authors: Anoop Singh, Asha Sharma, Aamir Ahmed, Ashok K. Sundramoorthy, Hidemitsu Furukawa, Sandeep Arya, Ajit Khosla
      First page: 336
      Abstract: The electrochemical biosensors are a class of biosensors which convert biological information such as analyte concentration that is a biological recognition element (biochemical receptor) into current or voltage. Electrochemical biosensors depict propitious diagnostic technology which can detect biomarkers in body fluids such as sweat, blood, feces, or urine. Combinations of suitable immobilization techniques with effective transducers give rise to an efficient biosensor. They have been employed in the food industry, medical sciences, defense, studying plant biology, etc. While sensing complex structures and entities, a large data is obtained, and it becomes difficult to manually interpret all the data. Machine learning helps in interpreting large sensing data. In the case of biosensors, the presence of impurity affects the performance of the sensor and machine learning helps in removing signals obtained from the contaminants to obtain a high sensitivity. In this review, we discuss different types of biosensors along with their applications and the benefits of machine learning. This is followed by a discussion on the challenges, missing gaps in the knowledge, and solutions in the field of electrochemical biosensors. This review aims to serve as a valuable resource for scientists and engineers entering the interdisciplinary field of electrochemical biosensors. Furthermore, this review provides insight into the type of electrochemical biosensors, their applications, the importance of machine learning (ML) in biosensing, and challenges and future outlook.
      Citation: Biosensors
      PubDate: 2021-09-14
      DOI: 10.3390/bios11090336
      Issue No: Vol. 11, No. 9 (2021)
  • Biosensors, Vol. 11, Pages 337: Recent Trends in Exhaled Breath Diagnosis
           Using an Artificial Olfactory System

    • Authors: Chuntae Kim, Iruthayapandi Selestin Raja, Jong-Min Lee, Jong Ho Lee, Moon Sung Kang, Seok Hyun Lee, Jin-Woo Oh, Dong-Wook Han
      First page: 337
      Abstract: Artificial olfactory systems are needed in various fields that require real-time monitoring, such as healthcare. This review introduces cases of detection of specific volatile organic compounds (VOCs) in a patient’s exhaled breath and discusses trends in disease diagnosis technology development using artificial olfactory technology that analyzes exhaled human breath. We briefly introduce algorithms that classify patterns of odors (VOC profiles) and describe artificial olfactory systems based on nanosensors. On the basis of recently published research results, we describe the development trend of artificial olfactory systems based on the pattern-recognition gas sensor array technology and the prospects of application of this technology to disease diagnostic devices. Medical technologies that enable early monitoring of health conditions and early diagnosis of diseases are crucial in modern healthcare. By regularly monitoring health status, diseases can be prevented or treated at an early stage, thus increasing the human survival rate and reducing the overall treatment costs. This review introduces several promising technical fields with the aim of developing technologies that can monitor health conditions and diagnose diseases early by analyzing exhaled human breath in real time.
      Citation: Biosensors
      PubDate: 2021-09-14
      DOI: 10.3390/bios11090337
      Issue No: Vol. 11, No. 9 (2021)
  • Biosensors, Vol. 11, Pages 338: A Co-Culture-Based Multiparametric Imaging
           Technique to Dissect Local H2O2 Signals with Targeted HyPer7

    • Authors: Melike Secilmis, Hamza Yusuf Altun, Johannes Pilic, Yusuf Ceyhun Erdogan, Zeynep Cokluk, Busra Nur Ata, Gulsah Sevimli, Asal Ghaffari Zaki, Esra Nur Yigit, Gürkan Öztürk, Roland Malli, Emrah Eroglu
      First page: 338
      Abstract: Multispectral live-cell imaging is an informative approach that permits detecting biological processes simultaneously in the spatial and temporal domain by exploiting spectrally distinct biosensors. However, the combination of fluorescent biosensors with distinct spectral properties such as different sensitivities, and dynamic ranges can undermine accurate co-imaging of the same analyte in different subcellular locales. We advanced a single-color multiparametric imaging method, which allows simultaneous detection of hydrogen peroxide (H2O2) in multiple cell locales (nucleus, cytosol, mitochondria) using the H2O2 biosensor HyPer7. Co-culturing of endothelial cells stably expressing differentially targeted HyPer7 biosensors paved the way for co-imaging compartmentalized H2O2 signals simultaneously in neighboring cells in a single experimental setup. We termed this approach COMPARE IT, which is an acronym for co-culture-based multiparametric imaging technique. Employing this approach, we detected lower H2O2 levels in mitochondria of endothelial cells compared to the cell nucleus and cytosol under basal conditions. Upon administering exogenous H2O2, the cytosolic and nuclear-targeted probes displayed similarly slow and moderate HyPer7 responses, whereas the mitochondria-targeted HyPer7 signal plateaued faster and reached higher amplitudes. Our results indicate striking differences in mitochondrial H2O2 accumulation of endothelial cells. Here, we present the method’s potential as a practicable and informative multiparametric live-cell imaging technique.
      Citation: Biosensors
      PubDate: 2021-09-14
      DOI: 10.3390/bios11090338
      Issue No: Vol. 11, No. 9 (2021)
  • Biosensors, Vol. 11, Pages 339: Rapid Detection of Gut Microbial
           Metabolite Trimethylamine N-Oxide for Chronic Kidney Disease Prevention

    • Authors: Yu-Chun Chang, Yi-Hsuan Chu, Chien-Cheng Wang, Chih-Hsuan Wang, You-Lin Tain, Hung-Wei Yang
      First page: 339
      Abstract: The gut microbiota plays a critical role in chronic kidney disease (CKD) and hypertension. Trimethylamine-N-oxide (TMAO) and trimethylamine (TMA) are gut microbiota-derived metabolites, and both are known uraemic toxins that are implicated in CKD, atherosclerosis, colorectal cancer and cardiovascular risk. Therefore, the detection and quantification of TMAO, which is a metabolite from gut microbes, are important for the diagnosis of diseases such as atherosclerosis, thrombosis and colorectal cancer. In this study, a new “colour-switch” method that is based on the combination of a plasma separation pad/absorption pad and polyallylamine hydrochloride-capped manganese dioxide (PAH@MnO2) nanozyme was developed for the direct quantitative detection of TMAO in whole blood without blood sample pretreatment. As a proof of concept, a limit of quantitation (LOQ) of less than 6.7 μM for TMAO was obtained with a wide linear quantification range from 15.6 to 500 μM through quantitative analysis, thereby suggesting potential clinical applications in blood TMAO monitoring for CKD patients.
      Citation: Biosensors
      PubDate: 2021-09-14
      DOI: 10.3390/bios11090339
      Issue No: Vol. 11, No. 9 (2021)
  • Biosensors, Vol. 11, Pages 340: FLIM-Based Intracellular and Extracellular
           pH Measurements Using Genetically Encoded pH Sensor

    • Authors: Alexander S. Goryashchenko, Alexey A. Pakhomov, Anastasia V. Ryabova, Igor D. Romanishkin, Eugene G. Maksimov, Alexander N. Orsa, Oxana V. Serova, Andrey A. Mozhaev, Margarita A. Maksimova, Vladimir I. Martynov, Alexander G. Petrenko, Igor E. Deyev
      First page: 340
      Abstract: The determination of pH in live cells and tissues is of high importance in physiology and cell biology. In this report, we outline the process of the creation of SypHerExtra, a genetically encoded fluorescent sensor that is capable of measuring extracellular media pH in a mildly alkaline range. SypHerExtra is a protein created by fusing the previously described pH sensor SypHer3s with the neurexin transmembrane domain that targets its expression to the cytoplasmic membrane. We showed that with excitation at 445 nm, the fluorescence lifetime of both SypHer3s and SypHerExtra strongly depend on pH. Using FLIM microscopy in live eukaryotic cells, we demonstrated that SypHerExtra can be successfully used to determine extracellular pH, while SypHer3s can be applied to measure intracellular pH. Thus, these two sensors are suitable for quantitative measurements using the FLIM method, to determine intracellular and extracellular pH in a range from pH 7.5 to 9.5 in different biological systems.
      Citation: Biosensors
      PubDate: 2021-09-15
      DOI: 10.3390/bios11090340
      Issue No: Vol. 11, No. 9 (2021)
  • Biosensors, Vol. 11, Pages 341: Genetically Encoded Sensor Cells for the
           Screening of Glucocorticoid Receptor (GR) Effectors in Herbal Extracts

    • Authors: Chungwon Kang, Soyoun Kim, Euiyeon Lee, Jeahee Ryu, Minhyeong Lee, Youngeun Kwon
      First page: 341
      Abstract: Although in vitro sensors provide facile low-cost ways to screen for biologically active targets, their results may not accurately represent the molecular interactions in biological systems. Cell-based sensors have emerged as promising platforms to screen targets in biologically relevant environments. However, there are few examples where cell-based sensors have been practically applied for drug screening. Here, we used engineered cortisol-detecting sensor cells to screen for natural mimetics of cortisol. The sensor cells were designed to report the presence of a target through signal peptide activation and subsequent fluorescence signal translocation. The developed sensor cells were able to detect known biological targets from human-derived analytes as well as natural product extracts, such as deer antlers and ginseng. The multi-use capability and versatility to screen in different cellular environments were also demonstrated. The sensor cells were used to identify novel GR effectors from medicinal plant extracts. Our results suggest that decursin from dongquai had the GR effector function as a selective GR agonist (SEGRA), making it a potent drug candidate with anti-inflammatory activity. We demonstrated the superiority of cell-based sensing technology over in vitro screening, proving its potential for practical drug screening applications that leads to the function-based discovery of target molecules.
      Citation: Biosensors
      PubDate: 2021-09-16
      DOI: 10.3390/bios11090341
      Issue No: Vol. 11, No. 9 (2021)
  • Biosensors, Vol. 11, Pages 342: Self-Powered Biosensor for Specifically
           Detecting Creatinine in Real Time Based on the Piezo-Enzymatic-Reaction
           Effect of Enzyme-Modified ZnO Nanowires

    • Authors: Meng Wang, Guangting Zi, Jiajun Liu, Yutong Song, Xishan Zhao, Qi Wang, Tianming Zhao
      First page: 342
      Abstract: Creatinine has become an important indicator for the early detection of uremia. However, due to the disadvantages of external power supply and large volume, some commercial devices for detecting creatinine concentration have lost a lot of popularity in everyday life. This paper describes the development of a self-powered biosensor for detecting creatinine in sweat. The biosensor can detect human creatinine levels in real time without the need for an external power source, providing information about the body’s overall health. The piezoelectric output voltage of creatininase/creatinase/sarcosine oxidase-modified ZnO nanowires (NWs) is significantly dependent on the creatinine concentration due to the coupling effect of the piezoelectric effect and enzymatic reaction (piezo-enzymatic-reaction effect), which can be regarded as both electrical energy and biosensing signal. Our results can be used for the detection of creatinine levels in the human body and have great potential in the prediction of related diseases.
      Citation: Biosensors
      PubDate: 2021-09-16
      DOI: 10.3390/bios11090342
      Issue No: Vol. 11, No. 9 (2021)
  • Biosensors, Vol. 11, Pages 343: Design of a Wearable Eye-Movement
           Detection System Based on Electrooculography Signals and Its Experimental

    • Authors: Chin-Teng Lin, Wei-Ling Jiang, Sheng-Fu Chen, Kuan-Chih Huang, Lun-De Liao
      First page: 343
      Abstract: In the assistive research area, human–computer interface (HCI) technology is used to help people with disabilities by conveying their intentions and thoughts to the outside world. Many HCI systems based on eye movement have been proposed to assist people with disabilities. However, due to the complexity of the necessary algorithms and the difficulty of hardware implementation, there are few general-purpose designs that consider practicality and stability in real life. Therefore, to solve these limitations and problems, an HCI system based on electrooculography (EOG) is proposed in this study. The proposed classification algorithm provides eye-state detection, including the fixation, saccade, and blinking states. Moreover, this algorithm can distinguish among ten kinds of saccade movements (i.e., up, down, left, right, farther left, farther right, up-left, down-left, up-right, and down-right). In addition, we developed an HCI system based on an eye-movement classification algorithm. This system provides an eye-dialing interface that can be used to improve the lives of people with disabilities. The results illustrate the good performance of the proposed classification algorithm. Moreover, the EOG-based system, which can detect ten different eye-movement features, can be utilized in real-life applications.
      Citation: Biosensors
      PubDate: 2021-09-17
      DOI: 10.3390/bios11090343
      Issue No: Vol. 11, No. 9 (2021)
  • Biosensors, Vol. 11, Pages 344: Applications of Aptamer-Bound
           Nanomaterials in Cancer Therapy

    • Authors: Liangxi Zhu, Jingzhou Zhao, Zhukang Guo, Yuan Liu, Hui Chen, Zhu Chen, Nongyue He
      First page: 344
      Abstract: Cancer is still a major disease that threatens human life. Although traditional cancer treatment methods are widely used, they still have many disadvantages. Aptamers, owing to their small size, low toxicity, good specificity, and excellent biocompatibility, have been widely applied in biomedical areas. Therefore, the combination of nanomaterials with aptamers offers a new method for cancer treatment. First, we briefly introduce the situation of cancer treatment and aptamers. Then, we discuss the application of aptamers in breast cancer treatment, lung cancer treatment, and other cancer treatment methods. Finally, perspectives on challenges and future applications of aptamers in cancer therapy are discussed.
      Citation: Biosensors
      PubDate: 2021-09-18
      DOI: 10.3390/bios11090344
      Issue No: Vol. 11, No. 9 (2021)
  • Biosensors, Vol. 11, Pages 345: Evaluation of Cancer Cell Lines by
           Four-Point Probe Technique, by Impedance Measurements in Various

    • Authors: Georgia Paivana, Dimitris Barmpakos, Sophie Mavrikou, Alexandros Kallergis, Odysseus Tsakiridis, Grigoris Kaltsas, Spyridon Kintzios
      First page: 345
      Abstract: Cell-based biosensors appear to be an attractive tool for the rapid, simple, and cheap monitoring of chemotherapy effects at a very early stage. In this study, electrochemical measurements using a four-point probe method were evaluated for suspensions of four cancer cell lines of different tissue origins: SK–N–SH, HeLa, MCF-7 and MDA-MB-231, all for two different population densities: 50 K and 100 K cells/500 μL. The anticancer agent doxorubicin was applied for each cell type in order to investigate whether the proposed technique was able to determine specific differences in cell responses before and after drug treatment. The proposed methodology can offer valuable insight into the frequency-dependent bioelectrical responses of various cellular systems using a low frequency range and without necessitating lengthy cell culture treatment. The further development of this biosensor assembly with the integration of specially designed cell/electronic interfaces can lead to novel diagnostic biosensors and therapeutic bioelectronics.
      Citation: Biosensors
      PubDate: 2021-09-18
      DOI: 10.3390/bios11090345
      Issue No: Vol. 11, No. 9 (2021)
  • Biosensors, Vol. 11, Pages 346: Advancement in Salmonella Detection
           Methods: From Conventional to Electrochemical-Based Sensing Detection

    • Authors: Mohd Syafiq Awang, Yazmin Bustami, Hairul Hisham Hamzah, Nor Syafirah Zambry, Mohamad Ahmad Najib, Muhammad Fazli Khalid, Ismail Aziah, Asrulnizam Abd Manaf
      First page: 346
      Abstract: Large-scale food-borne outbreaks caused by Salmonella are rarely seen nowadays, thanks to the advanced nature of the medical system. However, small, localised outbreaks in certain regions still exist and could possess a huge threat to the public health if eradication measure is not initiated. This review discusses the progress of Salmonella detection approaches covering their basic principles, characteristics, applications, and performances. Conventional Salmonella detection is usually performed using a culture-based method, which is time-consuming, labour intensive, and unsuitable for on-site testing and high-throughput analysis. To date, there are many detection methods with a unique detection system available for Salmonella detection utilising immunological-based techniques, molecular-based techniques, mass spectrometry, spectroscopy, optical phenotyping, and biosensor methods. The electrochemical biosensor has growing interest in Salmonella detection mainly due to its excellent sensitivity, rapidity, and portability. The use of a highly specific bioreceptor, such as aptamers, and the application of nanomaterials are contributing factors to these excellent characteristics. Furthermore, insight on the types of biorecognition elements, the principles of electrochemical transduction elements, and the miniaturisation potential of electrochemical biosensors are discussed.
      Citation: Biosensors
      PubDate: 2021-09-18
      DOI: 10.3390/bios11090346
      Issue No: Vol. 11, No. 9 (2021)
  • Biosensors, Vol. 11, Pages 347: Diffusion-Based Separation of
           Extracellular Vesicles by Nanoporous Membrane Chip

    • Authors: Gijung Kim, Min Chul Park, Seonae Jang, Daeyoung Han, Hojun Kim, Wonjune Kim, Honggu Chun, Sunghoon Kim
      First page: 347
      Abstract: Extracellular vesicles (EVs) have emerged as novel biomarkers and therapeutic material. However, the small size (~200 nm) of EVs makes efficient separation challenging. Here, a physical/chemical stress-free separation of EVs based on diffusion through a nanoporous membrane chip is presented. A polycarbonate membrane with 200 nm pores, positioned between two chambers, functions as the size-selective filter. Using the chip, EVs from cell culture media and human serum were separated. The separated EVs were analyzed by nanoparticle tracking analysis (NTA), scanning electron microscopy, and immunoblotting. The experimental results proved the selective separation of EVs in cell culture media and human serum. Moreover, the diffusion-based separation showed a high yield of EVs in human serum compared to ultracentrifuge-based separation. The EV recovery rate analyzed from NTA data was 42% for cell culture media samples. We expect the developed method to be a potential tool for EV separation for diagnosis and therapy because it does not require complicated processes such as immune, chemical reaction, and external force and is scalable by increasing the nanoporous membrane size.
      Citation: Biosensors
      PubDate: 2021-09-19
      DOI: 10.3390/bios11090347
      Issue No: Vol. 11, No. 9 (2021)
  • Biosensors, Vol. 11, Pages 348: Electrically Controlled Neurochemical
           Delivery from Microelectrodes for Focal and Transient Modulation of
           Cellular Behavior

    • Authors: Chao Tan, Neetu Kushwah, Xinyan Tracy Cui
      First page: 348
      Abstract: Electrically controlled drug delivery of neurochemicals and biomolecules from conducting polymer microelectrode coatings hold great potentials in dissecting neural circuit or treating neurological disorders with high spatial and temporal resolution. The direct doping of a drug into a conducting polymer often results in low loading capacity, and the type of molecule that can be released is limited. Poly(3,4-ethylenedioxythiophene) (PEDOT) doped with sulfonated silica nanoparticles (SNP) has been developed as a more versatile platform for drug delivery. In this work, we demonstrate that neurochemicals with different surface charge, e.g., glutamate (GLU), gamma-Aminobutyric acid (GABA), dopamine (DA), 6,7-Dinitroquinoxaline- 2,3-dione (DNQX) and bicuculline, can be, respectively, incorporated into the SNP and electrically triggered to release repeatedly. The drug loaded SNPs were incorporated in PEDOT via electrochemical deposition on platinum microelectrodes. After PEDOT/SNP(drug) coating, the charge storage capacity (CSC) increased 10-fold to 55 ± 3 mC/cm2, and the impedance at 1 kHz was also reduced approximately 6-fold. With the aid of a porous SNP, the loading capacity and number of releases of GLU was increased >4-fold and 66-fold, respectively, in comparison to the direct doping of PEDOT with GLU (PEDOT/GLU). The focal release of GLU and GABA from a PEDOT/SNP (drug) coated microelectrode were tested in cultured neurons using Ca imaging. The change in fluo-4 fluorescence intensity after electrically triggered GLU (+6.7 ± 2.9%) or GABA (−6.8 ± 1.6%) release indicated the successful modulation of neural activities by neurotransmitter release. In addition to activating neural activities, glutamate can also act on endothelial cells to stimulate nitric oxide (NO) release. A dual functional device with two adjacent sensing and releasing electrodes was constructed and we tested this mechanism in endothelial cell cultures. In endothelial cells, approximately 7.6 ± 0.6 nM NO was detected in the vicinity of the NO sensor within 6.2 ± 0.5 s of GLU release. The rise time of NO signal, T0–100, was 14.5 ± 2.2 s. In summary, our work has demonstrated (1) a platform that is capable of loading and releasing drugs with different charges; (2) proof of concept demonstrations of how focal release of drugs can be used as a pharmacological manipulation to study neural circuitry or NO’s effect on endothelial cells.
      Citation: Biosensors
      PubDate: 2021-09-20
      DOI: 10.3390/bios11090348
      Issue No: Vol. 11, No. 9 (2021)
  • Biosensors, Vol. 11, Pages 349: A Review of THz Technologies for Rapid
           Sensing and Detection of Viruses including SARS-CoV-2

    • Authors: Naznin Akter, Muhammad Mahmudul Hasan, Nezih Pala
      First page: 349
      Abstract: Virus epidemics such as Ebola virus, Zika virus, MERS-coronavirus, and others have wreaked havoc on humanity in the last decade. In addition, a coronavirus (SARS-CoV-2) pandemic and its continuously evolving mutants have become so deadly that they have forced the entire technical advancement of healthcare into peril. Traditional ways of detecting these viruses have been successful to some extent, but they are costly, time-consuming, and require specialized human resources. Terahertz-based biosensors have the potential to lead the way for low-cost, non-invasive, and rapid virus detection. This review explores the latest progresses in terahertz technology-based biosensors for the virus, viral particle, and antigen detection, as well as upcoming research directions in the field.
      Citation: Biosensors
      PubDate: 2021-09-22
      DOI: 10.3390/bios11100349
      Issue No: Vol. 11, No. 10 (2021)
  • Biosensors, Vol. 11, Pages 350: Mitigation of Data Packet Loss in
           Bluetooth Low Energy-Based Wearable Healthcare Ecosystem

    • Authors: Vishal Varun Tipparaju, Kyle R. Mallires, Di Wang, Francis Tsow, Xiaojun Xian
      First page: 350
      Abstract: Bluetooth Low Energy (BLE) plays a critical role in wireless data transmission in wearable technologies. The previous work in this field has mostly focused on optimizing the transmission throughput and power consumption. However, not much work has been reported on a systematic evaluation of the data packet loss of BLE in the wearable healthcare ecosystem, which is essential for reliable and secure data transmission. Considering that diverse wearable devices are used as peripherals and off-the-shelf smartphones (Android, iPhone) or Raspberry Pi with various chipsets and operating systems (OS) as hubs in the wearable ecosystem, there is an urgent need to understand the factors that influence data loss in BLE and develop a mitigation solution to address the data loss issue. In this work, we have systematically evaluated packet losses in Android and iOS based wearable ecosystems and proposed a reduced transmission frequency and data bundling strategy along with queue-based packet transmission protocol to mitigate data packet loss in BLE. The proposed protocol provides flexibility to the peripheral device to work with the host either in real-time mode for timely data transmission or offline mode for accumulated data transmission when there is a request from the host. The test results show that lowered transmission frequency and data bundling reduce the packet losses to less than 1%. The queue-based packet transmission protocol eliminates any remaining packet loss by using re-request routines. The data loss mitigation protocol developed in this research can be widely applied to the BLE-based wearable ecosystem for various applications, such as body sensor networks (BSN), the Internet of Things (IoT), and smart homes.
      Citation: Biosensors
      PubDate: 2021-09-23
      DOI: 10.3390/bios11100350
      Issue No: Vol. 11, No. 10 (2021)
  • Biosensors, Vol. 11, Pages 351: A Disposable Electrochemical Biosensor
           Based on Screen-Printed Carbon Electrodes Modified with Silver

    • Authors: Apichart Saenchoopa, Supannika Klangphukhiew, Rachata Somsub, Chanon Talodthaisong, Rina Patramanon, Jureerut Daduang, Sakda Daduang, Sirinan Kulchat
      First page: 351
      Abstract: This work describes the facile preparation of a disposable electrochemical biosensor for the detection of Hg(II) in water by modifying the surface of a screen-printed carbon electrode (SPCE). The surface modification consists of the immobilization of a composite layer of silver nanowires, hydroxymethyl propyl cellulose, chitosan, and urease (AgNWs/HPMC/CS/Urease). The presence of the composite was confirmed by scanning electron microscopy (SEM) and its excellent conductivity, due chiefly to the electrical properties of silver nanowires, enhanced the sensitivity of the biosensor. Under optimum conditions, the modified SPCE biosensor showed excellent performance for the detection of Hg(II) ions, with an incubation time of 10 min and a linear sensitivity range of 5–25 µM. The limit of detection (LOD) and limit of quantitation (LOQ) were observed to be 3.94 µM and 6.50 µM, respectively. In addition, the disposable and portable biosensor exhibited excellent recoveries for the detection of Hg(II) ions in commercial drinking water samples (101.62–105.26%). The results are correlated with those obtained from inductively coupled plasma optical emission spectrometry (ICP-OES), indicating that our developed sensor is a reliable method for detection of Hg(II) in real water samples. The developed sensor device is a simple, effective, portable, low cost, and user-friendly platform for real-time detection of heavy metal ions in field measurements with potential for other biomedical applications in the future.
      Citation: Biosensors
      PubDate: 2021-09-23
      DOI: 10.3390/bios11100351
      Issue No: Vol. 11, No. 10 (2021)
  • Biosensors, Vol. 11, Pages 352: Rolling Circle Amplification as an
           Efficient Analytical Tool for Rapid Detection of Contaminants in Aqueous

    • Authors: Kuankuan Zhang, Hua Zhang, Haorui Cao, Yu Jiang, Kang Mao, Zhugen Yang
      First page: 352
      Abstract: Environmental contaminants are a global concern, and an effective strategy for remediation is to develop a rapid, on-site, and affordable monitoring method. However, this remains challenging, especially with regard to the detection of various contaminants in complex water environments. The application of molecular methods has recently attracted increasing attention; for example, rolling circle amplification (RCA) is an isothermal enzymatic process in which a short nucleic acid primer is amplified to form a long single-stranded nucleic acid using a circular template and special nucleic acid polymerases. Furthermore, this approach can be further engineered into a device for point-of-need monitoring of environmental pollutants. In this paper, we describe the fundamental principles of RCA and the advantages and disadvantages of RCA assays. Then, we discuss the recently developed RCA-based tools for environmental analysis to determine various targets, including heavy metals, organic small molecules, nucleic acids, peptides, proteins, and even microorganisms in aqueous environments. Finally, we summarize the challenges and outline strategies for the advancement of this technique for application in contaminant monitoring.
      Citation: Biosensors
      PubDate: 2021-09-23
      DOI: 10.3390/bios11100352
      Issue No: Vol. 11, No. 10 (2021)
  • Biosensors, Vol. 11, Pages 353: Determining Particle Size and Position in
           a Coplanar Electrode Setup Using Measured Opacity for Microfluidic

    • Authors: Douwe S. de de Bruijn, Koen F. A. Jorissen, Wouter Olthuis, Albert van den van den Berg
      First page: 353
      Abstract: Microfluidic impedance flow cytometers enable high-throughput, non-invasive, and label-free detection of single-cells. Cytometers with coplanar electrodes are easy and cheap to fabricate, but are sensitive to positional differences of passing particles, owing to the inhomogeneous electric field. We present a novel particle height compensation method, which employs the dependence of measured electrical opacity on particle height. The measured electrical opacity correlates with the particle height as a result of the constant electrical double layer series capacitance of the electrodes. As an alternative to existing compensation methods, we use only two coplanar electrodes and multi-frequency analysis to determine the particle size of a mixture of 5, 6, and 7 µm polystyrene beads with an accuracy (CV) of 5.8%, 4.0%, and 2.9%, respectively. Additionally, we can predict the bead height with an accuracy of 1.5 µm (8% of channel height) using the measured opacity and we demonstrate its application in flow cytometry with yeast. The use of only two electrodes is of special interest for simplified, easy-to-use chips with a minimum amount of instrumentation and of limited size.
      Citation: Biosensors
      PubDate: 2021-09-23
      DOI: 10.3390/bios11100353
      Issue No: Vol. 11, No. 10 (2021)
  • Biosensors, Vol. 11, Pages 354: Bio-Specific Au/Fe3+ Porous Spongy
           Nanoclusters for Sensitive SERS Detection of Escherichia coli O157:H7

    • Authors: Yuzhi Li, Fei Gao, Chang Lu, Marie-Laure Fauconnier, Jinkai Zheng
      First page: 354
      Abstract: For sensitive and fast detection of Escherichia coli O157:H7, organic and inorganic hybrid Au/Fe3+ nanoclusters (NCs) were synthesized for the first time using gold nanoparticles (GNPs), bovine serum albumin, ferric chloride, phosphate-buffered saline, and antibodies. The Au/Fe3+ porous spongy NCs with large surface area showed excellent bio-specific capability for E. coli O157:H7. GNPs in Au/Fe3+ NCs functioned as signal enhancers, significantly increasing the Raman signal via the metathesis reaction product of Prussian blue and obviously improving the detection sensitivity. We combined the novel Au/Fe3+ NCs with antibody-modified magnetic nanoparticles to create a biosensor capable of sensitive detection of E. coli O157:H7, which showed a good linear response (101 to 106 cfu/mL), high detection sensitivity (2 cfu/mL), and good recovery rate (93.60–97.50%) in spiked food samples. These results make the biosensor well-suited for food safety monitoring. This strategy achieves the goal of sensitive and quantitative detection of E. coli O157:H7.
      Citation: Biosensors
      PubDate: 2021-09-24
      DOI: 10.3390/bios11100354
      Issue No: Vol. 11, No. 10 (2021)
  • Biosensors, Vol. 11, Pages 355: High-Performance Passive Plasma Separation
           on OSTE Pillar Forest

    • Authors: Zhiqing Xiao, Lexin Sun, Yuqian Yang, Zitao Feng, Sihan Dai, Hao Yang, Xingwei Zhang, Chia-Lin Sheu, Weijin Guo
      First page: 355
      Abstract: Plasma separation is of high interest for lateral flow tests using whole blood as sample liquids. Here, we built a passive microfluidic device for plasma separation with high performance. This device was made by blood filtration membrane and off-stoichiometry thiol–ene (OSTE) pillar forest. OSTE pillar forest was fabricated by double replica moldings of a laser-cut polymethylmethacrylate (PMMA) mold, which has a uniform microstructure. This device utilized a filtration membrane to separate plasma from whole blood samples and used hydrophilic OSTE pillar forest as the capillary pump to propel the plasma. The device can be used to separate blood plasma with high purity for later use in lateral flow tests. The device can process 45 μL of whole blood in 72 s and achieves a plasma separation yield as high as 60.0%. The protein recovery rate of separated plasma is 85.5%, which is on par with state-of-the-art technologies. This device can be further developed into lateral flow tests for biomarker detection in whole blood.
      Citation: Biosensors
      PubDate: 2021-09-25
      DOI: 10.3390/bios11100355
      Issue No: Vol. 11, No. 10 (2021)
  • Biosensors, Vol. 11, Pages 356: Neurophysiological Factors Affecting
           Muscle Innervation Zone Estimation Using Surface EMG: A Simulation Study

    • Authors: Chengjun Huang, Maoqi Chen, Xiaoyan Li, Yingchun Zhang, Sheng Li, Ping Zhou
      First page: 356
      Abstract: Surface electromyography (EMG) recorded by a linear or 2-dimensional electrode array can be used to estimate the location of muscle innervation zones (IZ). There are various neurophysiological factors that may influence surface EMG and thus potentially compromise muscle IZ estimation. The objective of this study was to evaluate how surface-EMG-based IZ estimation might be affected by different factors, including varying degrees of motor unit (MU) synchronization in the case of single or double IZs. The study was performed by implementing a model simulating surface EMG activity. Three different MU synchronization conditions were simulated, namely no synchronization, medium level synchronization, and complete synchronization analog to M wave. Surface EMG signals recorded by a 2-dimensional electrode array were simulated from a muscle with single and double IZs, respectively. For each situation, the IZ was estimated from surface EMG and compared with the one used in the model for performance evaluation. For the muscle with only one IZ, the estimated IZ location from surface EMG was consistent with the one used in the model for all the three MU synchronization conditions. For the muscle with double IZs, at least one IZ was appropriately estimated from interference surface EMG when there was no MU synchronization. However, the estimated IZ was different from either of the two IZ locations used in the model for the other two MU synchronization conditions. For muscles with a single IZ, MU synchronization has little effect on IZ estimation from electrode array surface EMG. However, caution is required for multiple IZ muscles since MU synchronization might lead to false IZ estimation.
      Citation: Biosensors
      PubDate: 2021-09-27
      DOI: 10.3390/bios11100356
      Issue No: Vol. 11, No. 10 (2021)
  • Biosensors, Vol. 11, Pages 357: Highly Sensitive Luminescent Bioassay
           Using Recombinant Escherichia coli Biosensor for Rapid Detection of Low
           Cr(VI) Concentration in Environmental Water

    • Authors: Guey-Horng Wang, Chiu-Yu Cheng, Teh-Hua Tsai, Pin-Kuan Chiang, Ying-Chien Chung
      First page: 357
      Abstract: In this study, we constructed a recombinant Escherichia coli strain with different promoters inserted between the chromate-sensing regulator chrB and the reporter gene luxAB to sense low hexavalent chromium (Cr(VI)) concentrations (<0.05 mg/L); subsequently, its biosensor characteristics (sensitivity, selectivity, and specificity) for measuring Cr(VI) in various water bodies were evaluated. The luminescence intensity of each biosensor depended on pH, temperature, detection time, coexisting carbon source, coexisting ion, Cr(VI) oxyanion form, Cr(VI) concentration, cell type, and type of medium. Recombinant lux-expressing E. coli with the T7 promoter (T7-lux-E. coli, limit of detection (LOD) = 0.0005 mg/L) had the highest luminescence intensity or was the most sensitive for Cr(VI) detection, followed by E. coli with the T3 promoter (T3-lux-E. coli, LOD = 0.001 mg/L) and that with the SP6 promoter (SP6-lux-E. coli, LOD = 0.005 mg/L). All biosensors could be used to determine whether the Cr(VI) standard was met in terms of water quality, even when using thawing frozen cells as biosensors after 90-day cryogenic storage. The SP6-lux-E. coli biosensor had the shortest detection time (0.5 h) and the highest adaptability to environmental interference. The T7-lux-E. coli biosensor—with the optimal LOD, a wide measurement range (0.0005–0.5 mg/L), and low deviation (−5.0–7.9%) in detecting Cr(VI) from industrial effluents, domestic effluents, and surface water—is an efficient Cr(VI) biosensor. This unprecedented study is to evaluate recombinant lux E. coli with dissimilar promoters for their possible practice in Cr(VI) measurement in water bodies, and the biosensor performance is clearly superior to that of past systems in terms of detection time, LOD, and detection deviation for real water samples.
      Citation: Biosensors
      PubDate: 2021-09-27
      DOI: 10.3390/bios11100357
      Issue No: Vol. 11, No. 10 (2021)
  • Biosensors, Vol. 11, Pages 358: Millimeter-Wave-Based Spoof Localized
           Surface Plasmonic Resonator for Sensing Glucose Concentration

    • Authors: Yelim Kim, Ahmed Salim, Sungjoon Lim
      First page: 358
      Abstract: Glucose-monitoring sensors are necessary and have been extensively studied to prevent and control health problems caused by diabetes. Spoof localized surface plasmon (LSP) resonance sensors have been investigated for chemical sensing and biosensing. A spoof LSP has similar characteristics to an LSP in the microwave or terahertz frequency range but with certain advantages, such as a high-quality factor and improved sensitivity. In general, microwave spoof LSP resonator-based glucose sensors have been studied. In this study, a millimeter-wave-based spoof surface plasmonic resonator sensor is designed to measure glucose concentrations. The millimeter-wave-based sensor has a smaller chip size and higher sensitivity than microwave-frequency sensors. Therefore, the microfluidic channel was designed to be reusable and able to operate with a small sample volume. For alignment, a polydimethylsiloxane channel was simultaneously fabricated using a multilayer bonding film to attach the upper side of the pattern, which is concentrated in the electromagnetic field. This real-time sensor detects the glucose concentration via changes in the S11 parameter and operates at 28 GHz with an average sensitivity of 0.015669 dB/(mg/dL) within the 0–300 mg/dL range. The minimum detectable concentration and the distinguishable signal are 1 mg/dL and 0.015669 dB, respectively, from a 3.4 μL sample. The reusability and reproducibility were assessed through replicates.
      Citation: Biosensors
      PubDate: 2021-09-28
      DOI: 10.3390/bios11100358
      Issue No: Vol. 11, No. 10 (2021)
  • Biosensors, Vol. 11, Pages 359: From Nanosystems to a Biosensing Prototype
           for an Efficient Diagnostic: A Special Issue in Honor of Professor Bansi
           D. Malhotra

    • Authors: Ajeet Kaushik, Raju Khan, Pratima Solanki, Sonu Gandhi, Hardik Gohel, Yogendra K. Mishra
      First page: 359
      Abstract: It has been proven that rapid bioinformatics analysis according to patient health profiles, in addition to biomarker detection at a low level, is emerging as essential to design an analytical diagnostics system to manage health intelligently in a personalized manner. Such objectives need an optimized combination of a nano-enabled sensing prototype, artificial intelligence (AI)-supported predictive analysis, and Internet of Medical Things (IoMT)-based bioinformatics analysis. Such a developed system began with a prototype demonstration of efficient diseases diagnostics performance is the future diseases management approach. To explore these aspects, the Special Issue planned for the nano-and micro-technology section of MDPI’s Biosensors journal will honor and acknowledge the contributions of Prof. B.D. Malhotra, Ph.D., FNA, FNASc has made in the field of biosensors.
      Citation: Biosensors
      PubDate: 2021-09-29
      DOI: 10.3390/bios11100359
      Issue No: Vol. 11, No. 10 (2021)
  • Biosensors, Vol. 11, Pages 360: Recent Progress in Electrochemical

    • Authors: JeeYoung Kim, Min Park
      First page: 360
      Abstract: Biosensors used for medical diagnosis work by analyzing physiological fluids. Antibodies have been frequently used as molecular recognition molecules for the specific binding of target analytes from complex biological solutions. Electrochemistry has been introduced for the measurement of quantitative signals from transducer-bound analytes for many reasons, including good sensitivity. Recently, numerous electrochemical immunosensors have been developed and various strategies have been proposed to detect biomarkers. In this paper, the recent progress in electrochemical immunosensors is reviewed. In particular, we focused on the immobilization methods using antibodies for voltammetric, amperometric, impedimetric, and electrochemiluminescent immunosensors.
      Citation: Biosensors
      PubDate: 2021-09-29
      DOI: 10.3390/bios11100360
      Issue No: Vol. 11, No. 10 (2021)
  • Biosensors, Vol. 11, Pages 361: Novel Micro-Nano Optoelectronic Biosensor
           for Label-Free Real-Time Biofilm Monitoring

    • Authors: Giuseppe Brunetti, Donato Conteduca, Mario Nicola Armenise, Caterina Ciminelli
      First page: 361
      Abstract: According to the World Health Organization forecasts, AntiMicrobial Resistance (AMR) is expected to become one of the leading causes of death worldwide in the following decades. The rising danger of AMR is caused by the overuse of antibiotics, which are becoming ineffective against many pathogens, particularly in the presence of bacterial biofilms. In this context, non-destructive label-free techniques for the real-time study of the biofilm generation and maturation, together with the analysis of the efficiency of antibiotics, are in high demand. Here, we propose the design of a novel optoelectronic device based on a dual array of interdigitated micro- and nanoelectrodes in parallel, aiming at monitoring the bacterial biofilm evolution by using optical and electrical measurements. The optical response given by the nanostructure, based on the Guided Mode Resonance effect with a Q-factor of about 400 and normalized resonance amplitude of about 0.8, allows high spatial resolution for the analysis of the interaction between planktonic bacteria distributed in small colonies and their role in the biofilm generation, calculating a resonance wavelength shift variation of 0.9 nm in the presence of bacteria on the surface, while the electrical response with both micro- and nanoelectrodes is necessary for the study of the metabolic state of the bacteria to reveal the efficacy of antibiotics for the destruction of the biofilm, measuring a current change of 330 nA when a 15 µm thick biofilm is destroyed with respect to the absence of biofilm.
      Citation: Biosensors
      PubDate: 2021-09-29
      DOI: 10.3390/bios11100361
      Issue No: Vol. 11, No. 10 (2021)
  • Biosensors, Vol. 11, Pages 362: Surface Plasmon Resonance for Protease
           Detection by Integration of Homogeneous Reaction

    • Authors: Ning Xia, Gang Liu, Xinyao Yi
      First page: 362
      Abstract: The heterogeneous assays of proteases usually require the immobilization of peptide substrates on the solid surface for enzymatic hydrolysis reactions. However, immobilization of peptides on the solid surface may cause a steric hindrance to prevent the interaction between the substrate and the active center of protease, thus limiting the enzymatic cleavage of the peptide. In this work, we reported a heterogeneous surface plasmon resonance (SPR) method for protease detection by integration of homogeneous reaction. The sensitivity was enhanced by the signal amplification of streptavidin (SA)-conjugated immunoglobulin G (SA-IgG). Caspase-3 (Cas-3) was determined as the model. A peptide labeled with two biotin tags at the N- and C-terminals (bio-GDEVDGK-bio) was used as the substrate. In the absence of Cas-3, the substrate peptide was captured by neutravidin (NA)-covered SPR chip to facilitate the attachment of SA-IgG by the avidin-biotin interaction. However, once the peptide substrate was digested by Cas-3 in the aqueous phase, the products of bio-GDEVD and GK-bio would compete with the substrate to bond NA on the chip surface, thus limiting the attachment of SA-IgG. The method integrated the advantages of both heterogeneous and homogeneous assays and has been used to determine Cas-3 inhibitor and evaluate cell apoptosis with satisfactory results.
      Citation: Biosensors
      PubDate: 2021-09-29
      DOI: 10.3390/bios11100362
      Issue No: Vol. 11, No. 10 (2021)
  • Biosensors, Vol. 11, Pages 363: An Optical Smartphone-Based Inspection
           Platform for Identification of Diseased Orchids

    • Authors: Kuan-Chieh Lee, Yen-Hsiang Wang, Wen-Chun Wei, Ming-Hsien Chiang, Ting-En Dai, Chung-Cheng Pan, Ting-Yuan Chen, Shi-Kai Luo, Po-Kuan Li, Ju-Kai Chen, Shien-Kuei Liaw, Choa-Feng Lin, Chin-Cheng Wu, Jen-Jie Chieh
      First page: 363
      Abstract: Infections of orchids by the Odontoglossum ringspot virus or Cymbidium mosaic virus cause orchid disfiguration and are a substantial source of economic loss for orchid farms. Although immunoassays can identify these infections, immunoassays are expensive, time consuming, and labor consuming and limited to sampling-based testing methods. This study proposes a noncontact inspection platform that uses a spectrometer and Android smartphone. When orchid leaves are illuminated with a handheld optical probe, the Android app based on the Internet of Things and artificial intelligence can display the measured florescence spectrum and determine the infection status within 3 s by using an algorithm hosted on a remote server. The algorithm was trained on optical data and the results of polymerase chain reaction assays. The testing accuracy of the algorithm was 89%. The area under the receiver operating characteristic curve was 91%; thus, the platform with the algorithm was accurate and convenient for infection screening in orchids.
      Citation: Biosensors
      PubDate: 2021-09-30
      DOI: 10.3390/bios11100363
      Issue No: Vol. 11, No. 10 (2021)
  • Biosensors, Vol. 11, Pages 364: Advances in Nanotechnology-Based
           Biosensing of Immunoregulatory Cytokines

    • Authors: Warangkana Lohcharoenkal, Zareen Abbas, Yon Rojanasakul
      First page: 364
      Abstract: Cytokines are a large group of small proteins secreted by immune and non-immune cells in response to external stimuli. Much attention has been given to the application of cytokines’ detection in early disease diagnosis/monitoring and therapeutic response assessment. To date, a wide range of assays are available for cytokines detection. However, in specific applications, multiplexed or continuous measurements of cytokines with wearable biosensing devices are highly desirable. For such efforts, various nanomaterials have been extensively investigated due to their extraordinary properties, such as high surface area and controllable particle size and shape, which leads to their tunable optical emission, electrical, and magnetic properties. Different types of nanomaterials such as noble metal, metal oxide, and carbon nanoparticles have been explored for various biosensing applications. Advances in nanomaterial synthesis and device development have led to significant progress in pushing the limit of cytokine detection. This article reviews currently used methods for cytokines detection and new nanotechnology-based biosensors for ultrasensitive cytokine detection.
      Citation: Biosensors
      PubDate: 2021-09-30
      DOI: 10.3390/bios11100364
      Issue No: Vol. 11, No. 10 (2021)
  • Biosensors, Vol. 11, Pages 365: Distinguishing Amyloid β-Protein in a
           Mouse Model of Alzheimer’s Disease by Label-Free Vibrational Imaging

    • Authors: Shaowei Li, Ziyi Luo, Renlong Zhang, Hao Xu, Ting Zhou, Liwei Liu, Junle Qu
      First page: 365
      Abstract: Due to the increase in the average age of humans, Alzheimer’s disease (AD) has become one of the disorders with the highest incidence worldwide. Abnormal amyloid β protein (Aβ) accumulation is believed to be the most common cause of AD. Therefore, distinguishing the lesion areas can provide clues for AD diagnosis. Here, we present an optical spectroscopy and imaging approach based on coherent anti-Stokes Raman scattering (CARS). Label-free vibrational imaging of Aβ in a mouse model of AD was performed to distinguish the lesion areas by studying the spectra of regions with and without Aβ plaques. Raman spectra in Aβ and non-Aβ regions exhibited a specific difference in the intensity ratio of the wave peaks detected at 2850 and 2930 cm−1. In the non-Aβ region, the ratio of the peak intensity at 2850 cm−1 to that at 2930 cm−1 was approximately 1, whereas that in the Aβ region was 0.8. This label-free vibrational imaging may provide a new method for the clinical diagnosis and basic research of AD.
      Citation: Biosensors
      PubDate: 2021-09-30
      DOI: 10.3390/bios11100365
      Issue No: Vol. 11, No. 10 (2021)
  • Biosensors, Vol. 11, Pages 366: An FPGA-Based Machine Learning Tool for
           In-Situ Food Quality Tracking Using Sensor Fusion

    • Authors: Daniel Enériz, Nicolas Medrano, Belen Calvo
      First page: 366
      Abstract: The continuous development of more accurate and selective bio- and chemo-sensors has led to a growing use of sensor arrays in different fields, such as health monitoring, cell culture analysis, bio-signals processing, or food quality tracking. The analysis and information extraction from the amount of data provided by these sensor arrays is possible based on Machine Learning techniques applied to sensor fusion. However, most of these computing solutions are implemented on costly and bulky computers, limiting its use in in-situ scenarios outside complex laboratory facilities. This work presents the application of machine learning techniques in food quality assessment using a single Field Programmable Gate Array (FPGA) chip. The characteristics of low-cost, low power consumption as well as low-size allow the application of the proposed solution even in space constrained places, as in food manufacturing chains. As an example, the proposed system is tested on an e-nose developed for beef classification and microbial population prediction.
      Citation: Biosensors
      PubDate: 2021-09-30
      DOI: 10.3390/bios11100366
      Issue No: Vol. 11, No. 10 (2021)
  • Biosensors, Vol. 11, Pages 367: Optical Biosensor Platforms Display
           Varying Sensitivity for the Direct Detection of Influenza RNA

    • Authors: Samantha Courtney, Zachary Stromberg, Adán Myers y Gutiérrez, Daniel Jacobsen, Loreen Stromberg, Kiersten Lenz, James Theiler, Brian Foley, Jason Gans, Karina Yusim, Jessica Kubicek-Sutherland
      First page: 367
      Abstract: Detection methods that do not require nucleic acid amplification are advantageous for viral diagnostics due to their rapid results. These platforms could provide information for both accurate diagnoses and pandemic surveillance. Influenza virus is prone to pandemic-inducing genetic mutations, so there is a need to apply these detection platforms to influenza diagnostics. Here, we analyzed the Fast Evaluation of Viral Emerging Risks (FEVER) pipeline on ultrasensitive detection platforms, including a waveguide-based optical biosensor and a flow cytometry bead-based assay. The pipeline was also evaluated in silico for sequence coverage in comparison to the U.S. Centers for Disease Control and Prevention’s (CDC) influenza A and B diagnostic assays. The influenza FEVER probe design had a higher tolerance for mismatched bases than the CDC’s probes, and the FEVER probes altogether had a higher detection rate for influenza isolate sequences from GenBank. When formatted for use as molecular beacons, the FEVER probes detected influenza RNA as low as 50 nM on the waveguide-based optical biosensor and 1 nM on the flow cytometer. In addition to molecular beacons, which have an inherently high background signal we also developed an exonuclease selection method that could detect 500 pM of RNA. The combination of high-coverage probes developed using the FEVER pipeline coupled with ultrasensitive optical biosensors is a promising approach for future influenza diagnostic and biosurveillance applications.
      Citation: Biosensors
      PubDate: 2021-09-30
      DOI: 10.3390/bios11100367
      Issue No: Vol. 11, No. 10 (2021)
  • Biosensors, Vol. 11, Pages 368: Disposable Voltammetric Sensor Modified
           with Block Copolymer-Dispersed Graphene for Simultaneous Determination of
           Dopamine and Ascorbic Acid in Ex Vivo Mouse Brain Tissue

    • Authors: Dinakaran Thirumalai, Seulah Lee, Minho Kwon, Hyun-jong Paik, Jaewon Lee, Seung-Cheol Chang
      First page: 368
      Abstract: Dopamine (DA) and ascorbic acid (AA) are two important biomarkers with similar oxidation potentials. To facilitate their simultaneous electrochemical detection, a new voltammetric sensor was developed by modifying a screen-printed carbon electrode (SPCE) with a newly synthesized block copolymer (poly(DMAEMA-b-styrene), PDbS) as a dispersant for reduced graphene oxide (rGO). The prepared PDbS–rGO and the modified SPCE were characterized using a range of physical and electrochemical techniques including Raman spectroscopy, scanning electron microscopy, transmission electron microscopy, cyclic voltammetry, electrochemical impedance spectroscopy, and linear sweep voltammetry. Compared to the bare SPCE, the PDbS–rGO-modified SPCE (PDbS–rGO/SPCE) showed better sensitivity and peak-to-peak separation for DA and AA in mixed solutions. Under the optimum conditions, the dynamic linear ranges for DA and AA were 0.1–300 and 10–1100 µM, and the detection limits were 0.134 and 0.88 µM (S/N = 3), respectively. Furthermore, PDbS–rGO/SPCE exhibited considerably enhanced anti-interference capability, high reproducibility, and storage stability for four weeks. The practical potential of the PDbS–rGO/SPCE sensor for measuring DA and AA was demonstrated using ex vivo brain tissues from a Parkinson’s disease mouse model and the control.
      Citation: Biosensors
      PubDate: 2021-10-01
      DOI: 10.3390/bios11100368
      Issue No: Vol. 11, No. 10 (2021)
  • Biosensors, Vol. 11, Pages 369: A Portable RT-LAMP/CRISPR Machine for
           Rapid COVID-19 Screening

    • Authors: Meysam Rezaei, Sajad Razavi Bazaz, Dorsa Morshedi Rad, Olga Shimoni, Dayong Jin, William Rawlinson, Majid Ebrahimi Warkiani
      First page: 369
      Abstract: The COVID-19 pandemic has changed people’s lives and has brought society to a sudden standstill, with lockdowns and social distancing as the preferred preventative measures. To lift these measurements and reduce society’s burden, developing an easy-to-use, rapid, and portable system to detect SARS-CoV-2 is mandatory. To this end, we developed a portable and semi-automated device for SARS-CoV-2 detection based on reverse transcription loop-mediated isothermal amplification followed by a CRISPR/Cas12a reaction. The device contains a heater element mounted on a printed circuit board, a cooler fan, a proportional integral derivative controller to control the temperature, and designated areas for 0.2 mL Eppendorf® PCR tubes. Our system has a limit of detection of 35 copies of the virus per microliter, which is significant and has the capability of being used in crisis centers, mobile laboratories, remote locations, or airports to diagnose individuals infected with SARS-CoV-2. We believe the current methodology that we have implemented in this article is beneficial for the early screening of infectious diseases, in which fast screening with high accuracy is necessary.
      Citation: Biosensors
      PubDate: 2021-10-02
      DOI: 10.3390/bios11100369
      Issue No: Vol. 11, No. 10 (2021)
  • Biosensors, Vol. 11, Pages 370: Sub-Part-Per-Billion Level Sensing of
           Fentanyl Residues from Wastewater Using Portable Surface-Enhanced Raman
           Scattering Sensing

    • Authors: Boxin Zhang, Xingwei Hou, Cheng Zhen, Alan X. Wang
      First page: 370
      Abstract: Detection of illicit drug residues from wastewater provides a new route toward community-level assessment of drug abuse that is critical to public health. However, traditional chemistry analytical tools such as high-performance liquid chromatography in tandem with mass spectrometry (HPLC-MS) cannot meet the large-scale testing requirement in terms of cost, promptness, and convenience of use. In this article, we demonstrated ultra-sensitive and portable surface-enhanced Raman scattering sensing (SERS) of fentanyl, a synthetic opioid, from sewage water and achieved quantitative analysis through principal component analysis and partial least-squares regression. The SERS substrates adopted in this application were synthesized by in situ growth of silver nanoparticles on diatomaceous earth films, which show ultra-high sensitivity down to 10 parts per trillion in artificially contaminated tap water in the lab using a commercial portable Raman spectrometer. Based on training data from artificially contaminated tap water, we predicted the fentanyl concentration in the sewage water from a wastewater treatment plant to be 0.8 parts per billion (ppb). As a comparison, the HPLC-MS confirmed the fentanyl concentration was below 1 ppb but failed to provide a specific value of the concentration since the concentration was too low. In addition, we further proved the validity of our SERS sensing technique by comparing SERS results from multiple sewage water treatment plants, and the results are consistent with the public health data from our local health authority. Such SERS sensing technique with ultra-high sensitivity down to sub-ppb level proved its feasibility for point-of-care detection of illicit drugs from sewage water, which is crucial to assess public health.
      Citation: Biosensors
      PubDate: 2021-10-03
      DOI: 10.3390/bios11100370
      Issue No: Vol. 11, No. 10 (2021)
  • Biosensors, Vol. 11, Pages 371: Versatile Cell and Animal Models for
           Advanced Investigation of Lead Poisoning

    • Authors: Yang, Chang
      First page: 371
      Abstract: The heavy metal, lead (Pb) can irreversibly damage the human nervous system. To help understand Pb-induced damage, we applied a genetically encoded Förster resonance energy transfer (FRET)-based Pb biosensor Met-lead 1.44 M1 to two living systems to monitor the concentration of Pb: induced pluripotent stem cell (iPSC)-derived cardiomyocytes as a semi-tissue platform and Drosophila melanogaster fruit flies as an in vivo animal model. Different FRET imaging modalities were used to obtain FRET signals, which represented the presence of Pb in the tested samples in different spatial dimensions. Using iPSC-derived cardiomyocytes, the relationship between beating activity (20–24 beats per minute, bpm) determined from the fluctuation of fluorescent signals and the concentrations of Pb represented by the FRET emission ratio values of Met-lead 1.44 M1 was revealed from simultaneous measurements. Pb (50 μM) affected the beating activity of cardiomyocytes, whereas two drugs that stop the entry of Pb differentially affected this beating activity: verapamil (2 μM) did not reverse the cessation of beating, whereas 2-APB (50 μM) partially restored this activity (16 bpm). The results clearly demonstrate the potential of this biosensor system as an anti-Pb drug screening application. In the Drosophila model, Pb was detected within the adult brain or larval central nervous system (Cha-gal4 > UAS-Met-lead 1.44 M1) using fast epifluorescence and high-resolution two-photon 3D FRET ratio image systems. The tissue-specific expression of Pb biosensors provides an excellent opportunity to explore the possible Pb-specific populations within living organisms. We believe that this integrated Pb biosensor system can be applied to the prevention of Pb poisoning and advanced research on Pb neurotoxicology.
      Citation: Biosensors
      PubDate: 2021-10-04
      DOI: 10.3390/bios11100371
      Issue No: Vol. 11, No. 10 (2021)
  • Biosensors, Vol. 11, Pages 372: Recent Advances on IoT-Assisted Wearable
           Sensor Systems for Healthcare Monitoring

    • Authors: Mamidwar, R, Shakruwala, Chadha, Srinivasan, Chang
      First page: 372
      Abstract: IoT has played an essential role in many industries over the last few decades. Recent advancements in the healthcare industry have made it possible to make healthcare accessible to more people and improve their overall health. The next step in healthcare is to integrate it with IoT-assisted wearable sensor systems seamlessly. This review rigorously discusses the various IoT architectures, different methods of data processing, transfer, and computing paradigms. It compiles various communication technologies and the devices commonly used in IoT-assisted wearable sensor systems and deals with its various applications in healthcare and their advantages to the world. A comparative analysis of all the wearable technology in healthcare is also discussed with tabulation of various research and technology. This review also analyses all the problems commonly faced in IoT-assisted wearable sensor systems and the specific issues that need to be tackled to optimize these systems in healthcare and describes the various future implementations that can be made to the architecture and the technology to improve the healthcare industry.
      Citation: Biosensors
      PubDate: 2021-10-04
      DOI: 10.3390/bios11100372
      Issue No: Vol. 11, No. 10 (2021)
  • Biosensors, Vol. 11, Pages 373: Rapid COVID-19 Molecular Diagnostic System
           Using Virus Enrichment Platform

    • Authors: Yoon Ok Jang, Hyo Joo Lee, Bonhan Koo, Hye-Hee Cha, Ji-Soo Kwon, Ji Yeun Kim, Myoung Gyu Kim, Hyun Soo Kim, Sung-Han Kim, Yong Shin
      First page: 373
      Abstract: The coronavirus disease 2019 (COVID-19) pandemic, caused by the severe acute respiratory syndrome coronavirus (SARS-CoV)-2, is rapidly spreading and severely straining the capacities of public health communities and systems around the world. Therefore, accurate, rapid, and robust diagnostic tests for COVID-19 are crucial to prevent further spread of the infection, alleviate the burden on healthcare and diagnostic facilities, and ensure timely therapeutic intervention. To date, several detection methods based on nucleic acid amplification have been developed for the rapid and accurate detection of SARS-CoV-2. Despite the myriad of advancements in the detection methods for SARS-CoV-2, rapid sample preparation methods for RNA extraction from viruses have rarely been explored. Here, we report a rapid COVID-19 molecular diagnostic system that combines a self-powered sample preparation assay and loop-mediated isothermal amplification (LAMP) based naked-eye detection method for the rapid and sensitive detection of SARS-CoV-2. The self-powered sample preparation assay with a hydrophilic polyvinylidene fluoride filter and dimethyl pimelimidate can be operated by hand, without the use of any sophisticated instrumentation, similar to the reverse transcription (RT)-LAMP-based lateral flow assay for the naked-eye detection of SARS-CoV-2. The COVID-19 molecular diagnostic system enriches the virus population, extracts and amplifies the target RNA, and detects SARS-CoV-2 within 60 min. We validated the accuracy of the system by using 23 clinical nasopharyngeal specimens. We envision that this proposed system will enable simple, facile, efficient, and inexpensive diagnosis of COVID-19 at home and the clinic as a pre-screening platform to reduce the burden on the medical staff in this pandemic era.
      Citation: Biosensors
      PubDate: 2021-10-06
      DOI: 10.3390/bios11100373
      Issue No: Vol. 11, No. 10 (2021)
  • Biosensors, Vol. 11, Pages 374: A Single-Substrate Biosensor with
           Spin-Coated Liquid Crystal Film for Simple, Sensitive and Label-Free
           Protein Detection

    • Authors: Po-Chang Wu, Chao-Ping Pai, Mon-Juan Lee, Wei Lee
      First page: 374
      Abstract: A liquid crystal (LC)-based single-substrate biosensor was developed by spin-coating an LC thin film on a dimethyloctadecyl[3-(trimethoxysilyl)propyl]ammonium chloride (DMOAP)-decorated glass slide. Compared with the conventional sandwiched cell configuration, the simplified procedure for the preparation of an LC film allows the film thickness to be precisely controlled by adjusting the spin rate, thus eliminating personal errors involved in LC cell assembly. The limit of detection (LOD) for bovine serum albumin (BSA) was lowered from 10−5 g/mL with a 4.2-μm-thick sandwiched cell of the commercial LC E7 to 10−7 g/mL with a 4.2-μm-thick spin-coated E7 film and further to 10−8 g/mL by reducing the E7 film thickness to 3.4 μm. Moreover, by exploiting the LC film of the highly birefringent nematic LC HDN in the immunodetection of the cancer biomarker CA125, an LOD comparable to that determined with a sandwiched HDN cell was achieved at 10−8-g/mL CA125 using a capture antibody concentration an order of magnitude lower than that in the LC cell. Our results suggest that employing spin-coated LC film instead of conventional sandwiched LC cell provides a more reliable, reproducible, and cost-effective single-substrate platform, allowing simple fabrication of an LC-based biosensor for sensitive and label-free protein detection and immunoassay.
      Citation: Biosensors
      PubDate: 2021-10-06
      DOI: 10.3390/bios11100374
      Issue No: Vol. 11, No. 10 (2021)
  • Biosensors, Vol. 11, Pages 375: Paper-Based Airborne Bacteria Collection
           and DNA Extraction Kit

    • Authors: Seok, Lee, Kim
      First page: 375
      Abstract: The critical risk from airborne infectious diseases, bio-weapons, and harmful bacteria is currently the highest it has ever been in human history. The requirement for monitoring airborne pathogens has gradually increased to defend against bioterrorism or prevent pandemics, especially via simple and low-cost platforms which can be applied in resource-limited settings. Here, we developed a paper-based airborne bacteria collection and DNA extraction kit suitable for simple application with minimal instruments. Airborne sample collection and DNA extraction for PCR analysis were integrated in the paper kit. We created an easy-to-use paper-based air monitoring system using 3D printing technology combined with an air pump. The operation time of the entire process, comprising air sampling, bacterial cell lysis, purification and concentration of DNA, and elution of the DNA analyte, was within 20 min. All the investigations and optimum settings were tested in a custom-designed closed cabinet system. In the fabricated cabinet system, the paper kit operated effectively at a temperature of 25–35 °C and 30–70% relative humidity for air containing 10–106 CFU Staphylococcus aureus. This paper kit could be applied for simple, rapid, and cost-effective airborne pathogen monitoring.
      Citation: Biosensors
      PubDate: 2021-10-07
      DOI: 10.3390/bios11100375
      Issue No: Vol. 11, No. 10 (2021)
  • Biosensors, Vol. 11, Pages 376: Design and Analysis of a Single System of
           Impedimetric Biosensors for the Detection of Mosquito-Borne Viruses

    • Authors: Nasrin, Tsuruga, Utomo, Chowdhury, Park
      First page: 376
      Abstract: The treatment for mosquito-borne viral diseases such as dengue virus (DENV), zika virus (ZIKV), and chikungunya virus (CHIKV) has become difficult due to delayed diagnosis processes. In addition, sharing the same transmission media and similar symptoms at the early stage of infection of these diseases has become more critical for early diagnosis. To overcome this, a common platform that can identify the virus with high sensitivity and selectivity, even for the different serotypes, is in high demand. In this study, we have attempted an electrochemical impedimetric method to detect the ZIKV, DENV, and CHIKV using their corresponding antibody-conjugated sensor electrodes. The significance of this method is emphasized on the fabrication of a common matrix of gold–polyaniline and sulfur, nitrogen-doped graphene quantum dot nanocomposites (Au-PAni-N,S-GQDs), which have a strong impedimetric response based only on the conjugated antibody, resulting in minimum cross-reactivity for the detection of various mosquito-borne viruses, separately. As a result, four serotypes of DENV and ZIKV, and CHIKV have been detected successfully with an LOD of femtogram mL–1.
      Citation: Biosensors
      PubDate: 2021-10-07
      DOI: 10.3390/bios11100376
      Issue No: Vol. 11, No. 10 (2021)
  • Biosensors, Vol. 11, Pages 377: High Sensitivity Terahertz Biosensor Based
           on Mode Coupling of a Graphene/Bragg Reflector Hybrid Structure

    • Authors: Liu, Zheng, Yuan, Wang, Yin, Dai, Zou, Jiang
      First page: 377
      Abstract: In this work, a high-sensitivity terahertz (THz) biosensor is achieved by using a graphene/Bragg reflector hybrid structure. This high-sensitivity THz biosensor is developed from the sharp Fano resonance transmission peak created by coupling the graphene Tamm plasmons (GTPs) mode to a defect mode. It is found that the proposed THz biosensor is highly sensitive to the Fermi energy of graphene, as well as the thickness and refractive index of the sensing medium. Through specific parameter settings, the composite structure can achieve both a liquid biosensor and a gas biosensor. For the liquid biosensor, the maximum sensitivity of >1000°/RIU is obtained by selecting appropriate parameters. We believe the proposed layered hybrid structure has the potential to fabricate graphene-based high-sensitivity biosensors.
      Citation: Biosensors
      PubDate: 2021-10-08
      DOI: 10.3390/bios11100377
      Issue No: Vol. 11, No. 10 (2021)
  • Biosensors, Vol. 11, Pages 378: Aptamer Embedded Arch-Cruciform DNA
           Assemblies on 2-D VS2 Scaffolds for Sensitive Detection of Breast Cancer

    • Authors: Quan, Wang, Zhang, Huang, Wang, Jiang
      First page: 378
      Abstract: Arch-cruciform DNA are self-assembled on AuNPs/VS2 scaffold as a highly sensitive and selective electrochemical biosensor for michigan cancer foundation-7 (MCF-7) breast cancer cells. In the construction, arch DNA is formed using two single-strand DNA sequences embedded with the aptamer for MCF-7 cells. In the absence of MCF-7 cells, a cruciform DNA labeled with three terminal biotin is bound to the top of arch DNA, which further combines with streptavidin-labeled horseradish peroxidase (HRP) to catalyze the hydroquinone-H2O2 reaction on the electrode surface. The presence of MCF-7 cells can release the cruciform DNA and reduce the amount of immobilized HRP, thus effectively inhibiting enzyme-mediated electrocatalysis. The electrochemical response of the sensor is negatively correlated with the concentration of MCF-7 cells, with a linear range of 10 − 1 × 105 cells/mL, and a limit of detection as low as 5 cells/mL (S/N = 3). Through two-dimensional materials and enzyme-based dual signal amplification, this biosensor may pave new ways for the highly sensitive detection of tumor cells in real samples.
      Citation: Biosensors
      PubDate: 2021-10-08
      DOI: 10.3390/bios11100378
      Issue No: Vol. 11, No. 10 (2021)
  • Biosensors, Vol. 11, Pages 379: Alginate Bead Biosystem for the
           Determination of Lactate in Sweat Using Image Analysis

    • Authors: Sandra Garcia-Rey, Edilberto Ojeda, Udara Bimendra Gunatilake, Lourdes Basabe-Desmonts, Fernando Benito-Lopez
      First page: 379
      Abstract: Lactate is present in sweat at high concentrations, being a metabolite of high interest in sport science and medicine. Therefore, the potential to determine lactate concentrations in physiological fluids, at the point of need with minimal invasiveness, is very valuable. In this work, the synthesis and performance of an alginate bead biosystem was investigated. Artificial sweat with different lactate concentrations was used as a proof of concept. The lactate detection was based on a colorimetric assay and an image analysis method using lactate oxidase, horseradish peroxidase and tetramethyl benzidine as the reaction mix. Lactate in artificial sweat was detected with a R² = 0.9907 in a linear range from 10 mM to 100 mM, with a limit of detection of 6.4 mM and a limit of quantification of 21.2 mM. Real sweat samples were used as a proof of concept to test the performance of the biosystem, obtaining a lactate concentration of 48 ± 3 mM. This novel sensing configuration, using alginate beads, gives a fast and reliable method for lactate sensing, which could be integrated into more complex analytical systems.
      Citation: Biosensors
      PubDate: 2021-10-09
      DOI: 10.3390/bios11100379
      Issue No: Vol. 11, No. 10 (2021)
  • Biosensors, Vol. 11, Pages 380: Mesoporous One-Component Gold Microshells
           as 3D SERS Substrates

    • Authors: Anna S. Vikulina, Inna Y. Stetsyura, M. Serdar Onses, Erkan Yilmaz, Andre G. Skirtach, Dmitry Volodkin
      First page: 380
      Abstract: Surface-enhanced Raman scattering (SERS) is a powerful analytical tool for label-free analysis that has found a broad spectrum of applications in material, chemical, and biomedical sciences. In recent years, a great interest has been witnessed in the rational design of SERS substrates to amplify Raman signals and optionally allow for the selective detection of analytes, which is especially essential and challenging for biomedical applications. In this study, hard templating of noble metals is proposed as a novel approach for the design of one-component tailor-made SERS platforms. Porous Au microparticles were fabricated via dual ex situ adsorption of Au nanoparticles and in situ reduction of HAuCl4 on mesoporous sacrificial microcrystals of vaterite CaCO3. Elimination of the microcrystals at mild conditions resulted in the formation of stable mesoporous one-component Au microshells. SERS performance of the microshells at very low 0.4 µW laser power was probed using rhodamine B and bovine serum albumin showing enhancement factors of 2 × 108 and 8 × 108, respectively. The proposed strategy opens broad avenues for the design and scalable fabrication of one-component porous metal particles that can serve as superior SERS platforms possessing both excellent plasmonic properties and the possibility of selective inclusion of analyte molecules and/or SERS nanotags for highly specific SERS analysis.
      Citation: Biosensors
      PubDate: 2021-10-09
      DOI: 10.3390/bios11100380
      Issue No: Vol. 11, No. 10 (2021)
  • Biosensors, Vol. 11, Pages 381: Smartphone-Based Chemiluminescent Origami
           µPAD for the Rapid Assessment of Glucose Blood Levels

    • Authors: Donato Calabria, Martina Zangheri, Ilaria Trozzi, Elisa Lazzarini, Andrea Pace, Mara Mirasoli, Massimo Guardigli
      First page: 381
      Abstract: Microfluidic paper analytical devices (µPADs) represent one of the most appealing trends in the development of simple and inexpensive analytical systems for diagnostic applications at the point of care (POC). Herein, we describe a smartphone-based origami µPAD for the quantitative determination of glucose in blood samples based on the glucose oxidase-catalyzed oxidation of glucose leading to hydrogen peroxide, which is then detected by means of the luminol/hexacyanoferrate(III) chemiluminescent (CL) system. By exploiting the foldable µPAD format, a two-step analytical procedure has been implemented. First, the diluted blood sample was added, and hydrogen peroxide was accumulated, then the biosensor was folded, and a transport buffer was added to bring hydrogen peroxide in contact with CL reagents, thus promoting the CL reaction. To enable POC applicability, the reagents required for the assay were preloaded in the µPAD so that no chemicals handling was required, and a 3D-printed portable device was developed for measuring the CL emission using the smartphone’s CMOS camera. The µPAD was stable for 30-day storage at room temperature and the assay, displaying a limit of detection of 10 µmol L−1, proved able to identify both hypoglycemic and hyperglycemic blood samples in less than 20 min.
      Citation: Biosensors
      PubDate: 2021-10-09
      DOI: 10.3390/bios11100381
      Issue No: Vol. 11, No. 10 (2021)
  • Biosensors, Vol. 11, Pages 382: Nanozyme-Participated Biosensing of
           Pesticides and Cholinesterases: A Critical Review

    • Authors: Hengjia Zhu, Peng Liu, Lizhang Xu, Xin Li, Panwang Hu, Bangxiang Liu, Jianming Pan, Fu Yang, Xiangheng Niu
      First page: 382
      Abstract: To improve the output and quality of agricultural products, pesticides are globally utilized as an efficient tool to protect crops from insects. However, given that most pesticides used are difficult to decompose, they inevitably remain in agricultural products and are further enriched into food chains and ecosystems, posing great threats to human health and the environment. Thus, developing efficient methods and tools to monitor pesticide residues and related biomarkers (acetylcholinesterase and butylcholinesterase) became quite significant. With the advantages of excellent stability, tailorable catalytic performance, low cost, and easy mass production, nanomaterials with enzyme-like properties (nanozymes) are extensively utilized in fields ranging from biomedicine to environmental remediation. Especially, with the catalytic nature to offer amplified signals for highly sensitive detection, nanozymes were finding potential applications in the sensing of various analytes, including pesticides and their biomarkers. To highlight the progress in this field, here the sensing principles of pesticides and cholinesterases based on nanozyme catalysis are definitively summarized, and emerging detection methods and technologies with the participation of nanozymes are critically discussed. Importantly, typical examples are introduced to reveal the promising use of nanozymes. Also, some challenges in the field and future trends are proposed, with the hope of inspiring more efforts to advance nanozyme-involved sensors for pesticides and cholinesterases.
      Citation: Biosensors
      PubDate: 2021-10-09
      DOI: 10.3390/bios11100382
      Issue No: Vol. 11, No. 10 (2021)
  • Biosensors, Vol. 11, Pages 383: Fibre-Optic Surface Plasmon Resonance
           Biosensor for Monoclonal Antibody Titer Quantification

    • Authors: Thai Thao Ly, Yinlan Ruan, Bobo Du, Peipei Jia, Hu Zhang
      First page: 383
      Abstract: An extraordinary optical transmission fibre-optic surface plasmon resonance biosensing platform was engineered to improve its portability and sensitivity, and was applied to monitor the concentrations of monoclonal antibodies (Mabs). By refining the fabricating procedure and changing the material of the flow cell and the components of the optical fibre, the biosensor is portable and robust to external interference. After the implementation of an effective template cleaning procedure and precise control during the fabrication process, a consistent sensitivity of 509 ± 5 nm per refractive index unit (nm/RIU) was achieved. The biosensor can detect the Mab with a limit of detection (LOD) of 0.44 µg/mL. The results show that the biosensor is a potential tool for the rapid quantification of Mab titers. The biosensor can be regenerated at least 10 times with 10 mM glycine (pH = 2.5), and consistent signal changes were obtained after regeneration. Moreover, the employment of a spacer arm SM(PEG)2, used for immobilising protein A onto the gold film, was demonstrated to be unable to improve the detecting sensitivity; thus, a simple procedure without the spacer arm could be used to prepare the protein A-based biosensor. Our results demonstrate that the fibre-optic surface plasmon resonance biosensor is competent for the real-time and on-line monitoring of antibody titers in the future as a process analytical technologies (PATs) tool for bioprocess developments and the manufacture of therapeutic antibodies.
      Citation: Biosensors
      PubDate: 2021-10-10
      DOI: 10.3390/bios11100383
      Issue No: Vol. 11, No. 10 (2021)
  • Biosensors, Vol. 11, Pages 384: Application of Functionalized Graphene
           Oxide Based Biosensors for Health Monitoring: Simple Graphene Derivatives
           to 3D Printed Platforms

    • Authors: Agnivo Gosai, Kamil Reza Khondakar, Xiao Ma, Md. Azahar Ali
      First page: 384
      Abstract: Biosensors hold great potential for revolutionizing personalized medicine and environmental monitoring. Their construction is the key factor which depends on either manufacturing techniques or robust sensing materials to improve efficacy of the device. Functional graphene is an attractive choice for transducing material due to its various advantages in interfacing with biorecognition elements. Graphene and its derivatives such as graphene oxide (GO) are thus being used extensively for biosensors for monitoring of diseases. In addition, graphene can be patterned to a variety of structures and is incorporated into biosensor devices such as microfluidic devices and electrochemical and plasmonic sensors. Among biosensing materials, GO is gaining much attention due to its easy synthesis process and patternable features, high functionality, and high electron transfer properties with a large surface area leading to sensitive point-of-use applications. Considering demand and recent challenges, this perspective review is an attempt to describe state-of-the-art biosensors based on functional graphene. Special emphasis is given to elucidating the mechanism of sensing while discussing different applications. Further, we describe the future prospects of functional GO-based biosensors for health care and environmental monitoring with a focus on additive manufacturing such as 3D printing.
      Citation: Biosensors
      PubDate: 2021-10-10
      DOI: 10.3390/bios11100384
      Issue No: Vol. 11, No. 10 (2021)
  • Biosensors, Vol. 11, Pages 385: Applications of Microfluidics in Liquid
           Crystal-Based Biosensors

    • Authors: Deng, Han, Yang
      First page: 385
      Abstract: Liquid crystals (LCs) with stimuli-responsive configuration transition and optical anisotropic properties have attracted enormous interest in the development of simple and label-free biosensors. The combination of microfluidics and the LCs offers great advantages over traditional LC-based biosensors including small sample consumption, fast analysis and low cost. Moreover, microfluidic techniques provide a promising tool to fabricate uniform and reproducible LC-based sensing platforms. In this review, we emphasize the recent development of microfluidics in the fabrication and integration of LC-based biosensors, including LC planar sensing platforms and LC droplets. Fabrication and integration of LC-based planar platforms with microfluidics for biosensing applications are first introduced. The generation and entrapment of monodisperse LC droplets with different microfluidic structures, as well as their applications in the detection of chemical and biological species, are then summarized. Finally, the challenges and future perspectives of the development of LC-based microfluidic biosensors are proposed. This review will promote the understanding of microfluidic techniques in LC-based biosensors and facilitate the development of LC-based microfluidic biosensing devices with high performance.
      Citation: Biosensors
      PubDate: 2021-10-12
      DOI: 10.3390/bios11100385
      Issue No: Vol. 11, No. 10 (2021)
  • Biosensors, Vol. 11, Pages 386: Portable and Label-Free Quantitative
           Loop-Mediated Isothermal Amplification (LF-qLamp) for Reliable COVID-19
           Diagnostics in Three Minutes of Reaction Time: Arduino-Based Detection
           System Assisted by a pH Microelectrode

    • Authors: Mario Moisés Alvarez, Sergio Bravo-González, Everardo González-González, Grissel Trujillo-de Santiago
      First page: 386
      Abstract: Loop-mediated isothermal amplification (LAMP) has been recently studied as an alternative method for cost-effective diagnostics in the context of the current COVID-19 pandemic. Recent reports document that LAMP-based diagnostic methods have a comparable sensitivity and specificity to that of RT-qPCR. We report the use of a portable Arduino-based LAMP-based amplification system assisted by pH microelectrodes for the accurate and reliable diagnosis of SARS-CoV-2 during the first 3 min of the amplification reaction. We show that this simple system enables a straightforward discrimination between samples containing or not containing artificial SARS-CoV-2 genetic material in the range of 10 to 10,000 copies per 50 µL of reaction mix. We also spiked saliva samples with SARS-CoV-2 synthetic material and corroborated that the LAMP reaction can be successfully monitored in real time using microelectrodes in saliva samples as well. These results may have profound implications for the design of real-time and portable quantitative systems for the reliable detection of viral pathogens including SARS-CoV-2.
      Citation: Biosensors
      PubDate: 2021-10-13
      DOI: 10.3390/bios11100386
      Issue No: Vol. 11, No. 10 (2021)
  • Biosensors, Vol. 11, Pages 387: Noncontact Optical Measurement of Aqueous
           Humor Glucose Levels and Correlation with Serum Glucose Levels in Rabbit

    • Authors: Yih-Shiou Hwang, Eugene Yu-Chuan Kang, Chia-Rui Shen, Wei-Hsin Hong, Wei-Chi Wu
      First page: 387
      Abstract: The noninvasive measurement of serum glucose levels has been investigated for the monitoring of blood sugar control in diabetes. In our study, we aimed to develop a novel noncontact glucometer (NCGM) utilizing an optical approach to measure the intraocular aqueous humor glucose levels in the anterior chamber of rabbit eyes. The NCGM consists of a hybrid optical system that simultaneously measures near-infrared absorption and the polarized rotatory distribution of glucose molecules in the aqueous humor. In vitro optical measurements demonstrated that NCGM measurements had high precision and repeatability for different glucose levels, including 50 mg/dL (14.36%), 100 mg/dL (−4.05%), 200 mg/dL (−5.99%), 300 mg/dL (4.86%), 400 mg/dL (−2.84%), 500 mg/dL (−0.11%), and 600 mg/dL (4.48%). In the rabbit experiments, we found a high correlation between aqueous glucose levels and serum glucose levels, with a mean difference of 8 mg/dL. According to the testing results, the in vivo NCGM measurement of aqueous humor glucose levels also displayed a high correlation with serum glucose levels, with a mean difference of 29.2 mg/dL. In conclusion, aqueous humor glucose levels were accurately measured using the NCGM, and the results correlated with serum glucose levels.
      Citation: Biosensors
      PubDate: 2021-10-13
      DOI: 10.3390/bios11100387
      Issue No: Vol. 11, No. 10 (2021)
  • Biosensors, Vol. 11, Pages 388: Microfluidic Lab-on-a-Chip Based on
           UHF-Dielectrophoresis for Stemness Phenotype Characterization and
           Discrimination among Glioblastoma Cells

    • Authors: Elisa Lambert, Rémi Manczak, Elodie Barthout, Sofiane Saada, Elena Porcù, Francesca Maule, Barbara Bessette, Giampietro Viola, Luca Persano, Claire Dalmay, Fabrice Lalloué, Arnaud Pothier
      First page: 388
      Abstract: Glioblastoma (GBM) is one of the most aggressive solid tumors, particularly due to the presence of cancer stem cells (CSCs). Nowadays, the characterization of this cell type with an efficient, fast and low-cost method remains an issue. Hence, we have developed a microfluidic lab-on-a-chip based on dielectrophoresis (DEP) single cell electro-manipulation to measure the two crossover frequencies: fx01 in the low-frequency range (below 500 kHz) and fx02 in the ultra-high-frequency range (UHF, above 50 MHz). First, in vitro conditions were investigated. An U87-MG cell line was cultured in different conditions in order to induce an undifferentiated phenotype. Then, ex vivo GBM cells from patients’ primary cell culture were passed through the developed microfluidic system and characterized in order to reflect clinical conditions. This article demonstrates that the usual exploitation of low-frequency range DEP does not allow the discrimination of the undifferentiated GBM cells from the differentiated one. However, the presented study highlights the use of UHF-DEP as a relevant discriminant parameter. The proposed microfluidic lab-on-a-chip is able to follow the kinetics of U87-MG phenotype transformation in a CSC enrichment medium and the cancer stem cells phenotype acquirement.
      Citation: Biosensors
      PubDate: 2021-10-13
      DOI: 10.3390/bios11100388
      Issue No: Vol. 11, No. 10 (2021)
  • Biosensors, Vol. 11, Pages 389: Brain–Computer Interfacing Using
           Functional Near-Infrared Spectroscopy (fNIRS)

    • Authors: Paulmurugan, Vijayaragavan, Ghosh, Padmanabhan, Gulyás
      First page: 389
      Abstract: Functional Near-Infrared Spectroscopy (fNIRS) is a wearable optical spectroscopy system originally developed for continuous and non-invasive monitoring of brain function by measuring blood oxygen concentration. Recent advancements in brain–computer interfacing allow us to control the neuron function of the brain by combining it with fNIRS to regulate cognitive function. In this review manuscript, we provide information regarding current advancement in fNIRS and how it provides advantages in developing brain–computer interfacing to enable neuron function. We also briefly discuss about how we can use this technology for further applications.
      Citation: Biosensors
      PubDate: 2021-10-13
      DOI: 10.3390/bios11100389
      Issue No: Vol. 11, No. 10 (2021)
  • Biosensors, Vol. 11, Pages 390: Theoretical Model for a Highly Sensitive
           Near Infrared Biosensor Based on Bloch Surface Wave with Dirac Semimetal

    • Authors: Qiwen Zheng, Yamei Liu, Wenguang Lu, Xiaoyu Dai, Haishan Tian, Leyong Jiang
      First page: 390
      Abstract: In this work, we present a theoretical model of a near-infrared sensitive refractive index biosensor based on the truncate 1D photonic crystal (1D PC) structure with Dirac semimetal. This highly sensitive near-infrared biosensor originates from the sharp reflectance peak caused by the excitation of Bloch surface wave (BSW) at the interface between the Dirac semimetal and 1D PC. The sensitivity of the biosensor model is sensitive to the Fermi energy of Dirac semimetal, the thickness of the truncate layer and the refractive index of the sensing medium. By optimizing the structural parameters, the maximum refractive index sensitivity of the biosensor model can surpass 17.4 × 103/RIU, which achieves a certain competitiveness compared to conventional surface plasmon resonance (SPR) or BSW sensors. Considering that bulk materials are easier to handle than two-dimensional materials in manufacturing facilities, we judge that 3D Dirac semimetal and its related devices will provide a strong competitor and alternative to graphene-based devices.
      Citation: Biosensors
      PubDate: 2021-10-14
      DOI: 10.3390/bios11100390
      Issue No: Vol. 11, No. 10 (2021)
  • Biosensors, Vol. 11, Pages 391: Oxygen Saturation Behavior by Pulse
           Oximetry in Female Athletes: Breaking Myths

    • Authors: Pilar Martín-Escudero, Ana María Cabanas, Manuel Fuentes-Ferrer, Mercedes Galindo-Canales
      First page: 391
      Abstract: The myths surrounding women’s participation in sport have been reflected in respiratory physiology. This study aims to demonstrate that continuous monitoring of blood oxygen saturation during a maximal exercise test in female athletes is highly correlated with the determination of the second ventilatory threshold (VT2) or anaerobic threshold (AnT). The measurements were performed using a pulse oximeter during a maximum effort test on a treadmill on a population of 27 healthy female athletes. A common behavior of the oxygen saturation evolution during the incremental exercise test characterized by a decrease in saturation before the aerobic threshold (AeT) followed by a second significant drop was observed. Decreases in peripheral oxygen saturation during physical exertion have been related to the athlete’s physical fitness condition. However, this drop should not be a limiting factor in women’s physical performance. We found statistically significant correlations between the maximum oxygen uptake and the appearance of the ventilatory thresholds (VT1 and VT2), the desaturation time, the total test time, and between the desaturation time and the VT2. We observed a relationship between the desaturation time and the VT2 appearance. Indeed, a linear regression model between the desaturation time and the VT2 appearance can predict 80% of the values in our sample. Besides, we suggest that pulse oximetry is a simple, fairly accurate, and non-invasive technique for studying the physical condition of athletes who perform physical exertion.
      Citation: Biosensors
      PubDate: 2021-10-14
      DOI: 10.3390/bios11100391
      Issue No: Vol. 11, No. 10 (2021)
  • Biosensors, Vol. 11, Pages 392: On-Site Detection of Carcinoembryonic
           Antigen in Human Serum

    • Authors: Tohid Mahmoudi, Mohammad Pourhassan-Moghaddam, Behnaz Shirdel, Behzad Baradaran, Eden Morales-Narváez, Hamed Golmohammadi
      First page: 392
      Abstract: Real-time connectivity and employment of sustainable materials empowers point-of-care diagnostics with the capability to send clinically relevant data to health care providers even in low-resource settings. In this study, we developed an advantageous kit for the on-site detection of carcinoembryonic antigen (CEA) in human serum. CEA sensing was performed using cellulose-based lateral flow strips, and colorimetric signals were read, processed, and measured using a smartphone-based system. The corresponding immunoreaction was reported by polydopamine-modified gold nanoparticles in order to boost the signal intensity and improve the surface blocking and signal-to-noise relationship, thereby enhancing detection sensitivity when compared with bare gold nanoparticles (up to 20-fold in terms of visual limit of detection). Such lateral flow strips showed a linear range from 0.05 to 50 ng/mL, with a visual limit of detection of 0.05 ng/mL and an assay time of 15 min. Twenty-six clinical samples were also tested using the proposed kit and compared with the gold standard of immunoassays (enzyme linked immunosorbent assay), demonstrating an excellent correlation (R = 0.99). This approach can potentially be utilized for the monitoring of cancer treatment, particularly at locations far from centralized laboratory facilities.
      Citation: Biosensors
      PubDate: 2021-10-14
      DOI: 10.3390/bios11100392
      Issue No: Vol. 11, No. 10 (2021)
  • Biosensors, Vol. 11, Pages 393: Biomechanical and Physiological Evaluation
           of a Multi-Joint Exoskeleton with Active-Passive Assistance for Walking

    • Authors: Wujing Cao, Zhewen Zhang, Chunjie Chen, Yong He, Dashuai Wang, Xinyu Wu
      First page: 393
      Abstract: How to improve the walking efficiency while ensuring the wearability is an important issue of lower limb exoskeletons. Active devices can provide greater forces, while the passive devices have advantage in weight. We presented a multi-joint exoskeleton with active hip extension assistance and passive ankle plantarflexion assistance in this work. An admittance controller based on a feedforward model was proposed to track the desired active force of the hip extension. An underfoot clutch mechanism was adapted to realize the passive ankle plantarflexion assistance. To assess the efficacy of the multi-joint exoskeleton in assisting walking, we conducted comprehensive experiments to evaluate the force tracking performance, lower limb muscle activities and metabolic cost. The results demonstrated that: (i) The average tracking error of the peak hip extension assistance force from three subjects was less than 3%. (ii) The reductions of normalized root-mean-square EMG in the lateral soleus, medial soleus and gluteus maximus of eight subjects achieved 15.33%, 11.11%, and 3.74%, respectively. (iii) The average metabolic cost of six subjects was reduced by 10.41% under exoskeleton on (EO) condition comparing to the condition of walking with no exoskeleton (NE). This work proved that the concept of the multi-joint exoskeleton with active-passive assistance can improve the walking efficiency.
      Citation: Biosensors
      PubDate: 2021-10-15
      DOI: 10.3390/bios11100393
      Issue No: Vol. 11, No. 10 (2021)
  • Biosensors, Vol. 11, Pages 394: Liquid Biopsy-Based Biosensors for MRD
           Detection and Treatment Monitoring in Non-Small Cell Lung Cancer (NSCLC)

    • Authors: Parvaneh Sardarabadi, Amir Asri Kojabad, Davod Jafari, Cheng-Hsien Liu
      First page: 394
      Abstract: Globally, non-small cell lung cancer (NSCLC) is the leading cause of cancer deaths. Despite advancements in chemotherapy and targeted therapies, the 5-year survival rate has remained at 16% for the past forty years. Minimal residual disease (MRD) is described as the existence of either isolated tumour cells or circulating tumour cells in biological liquid of patients after removal of the primary tumour without any clinical signs of cancer. Recently, liquid biopsy has been promising as a non-invasive method of disease monitoring and treatment guidelines as an MRD marker. Liquid biopsy could be used to detect and assess earlier stages of NSCLC, post-treatment MRD, resistance to targeted therapies, immune checkpoint inhibitors (ICIs) and tumour mutational burden. MRD surveillance has been proposed as a potential marker for lung cancer relapse. Principally, biosensors provide the quantitative analysis of various materials by converting biological functions into quantifiable signals. Biosensors are usually operated to detect antibodies, enzymes, DNA, RNA, extracellular vesicles (EVs) and whole cells. Here, we present a category of biosensors based on the signal transduction method for identifying biosensor-based biomarkers in liquid biopsy specimens to monitor lung cancer treatment.
      Citation: Biosensors
      PubDate: 2021-10-15
      DOI: 10.3390/bios11100394
      Issue No: Vol. 11, No. 10 (2021)
  • Biosensors, Vol. 11, Pages 395: Topographical Vacuum Sealing of 3D-Printed
           Multiplanar Microfluidic Structures

    • Authors: Benjamin Heidt, Renato Rogosic, Nils Leoné, Eduardo J. S. Brás, Thomas J. Cleij, Jules A. W. Harings, Hanne Diliën, Kasper Eersels, Bart van Grinsven
      First page: 395
      Abstract: We demonstrate a novel way of creating three-dimensional microfluidic channels capable of following complex topographies. To this end, substrates with open channels and different geometries were 3D-printed, and the open channels were consecutively closed with a thermoplastic using a low-resolution vacuum-forming approach. This process allows the sealing of channels that are located on the surface of complex multiplanar topographies, as the thermoplastic aligns with the surface-shape (the macrostructure) of the substrate, while the microchannels remain mostly free of thermoplastic as their small channel size resists thermoplastic inflow. This new process was analyzed for its capability to consistently close different substrate geometries, which showed reliable sealing of angles >90°. Furthermore, the thermoplastic intrusion into channels of different widths was quantified, showing a linear effect of channel width and percentage of thermoplastic intrusion; ranging from 43.76% for large channels with 2 mm width to only 5.33% for channels with 500 µm channel width. The challenging sealing of substrate ‘valleys’, which are created when two large protrusions are adjacent to each other, was investigated and the correlation between protrusion distance and height is shown. Lastly, we present three application examples: a serpentine mixer with channels spun around a cuboid, increasing the usable surface area; a cuvette-inspired flow cell for a 2-MXP biosensor based on molecular imprinted polymers, fitting inside a standard UV/Vis-Spectrophotometer; and an adapter system that can be manufactured by one-sided injection molding and is self-sealed before usage. These examples demonstrate how this novel technology can be used to easily adapt microfluidic circuits for application in biosensor platforms.
      Citation: Biosensors
      PubDate: 2021-10-15
      DOI: 10.3390/bios11100395
      Issue No: Vol. 11, No. 10 (2021)
  • Biosensors, Vol. 11, Pages 396: Malignancies and Biosensors: A Focus on
           Oral Cancer Detection through Salivary Biomarkers

    • Authors: Goldoni, Scolaro, Boccalari, Dolci, Scarano, Inchingolo, Ravazzani, Muti, Tartaglia
      First page: 396
      Abstract: Oral cancer is among the deadliest types of malignancy due to the late stage at which it is usually diagnosed, leaving the patient with an average five-year survival rate of less than 50%. The booming field of biosensing and point of care diagnostics can, in this regard, play a major role in the early detection of oral cancer. Saliva is gaining interest as an alternative biofluid for non-invasive diagnostics, and many salivary biomarkers of oral cancer have been proposed. While these findings are promising for the application of salivaomics tools in routine practice, studies on larger cohorts are still needed for clinical validation. This review aims to summarize the most recent development in the field of biosensing related to the detection of salivary biomarkers commonly associated with oral cancer. An introduction to oral cancer diagnosis, prognosis and treatment is given to define the clinical problem clearly, then saliva as an alternative biofluid is presented, along with its advantages, disadvantages, and collection procedures. Finally, a brief paragraph on the most promising salivary biomarkers introduces the sensing technologies commonly exploited to detect oral cancer markers in saliva. Hence this review provides a comprehensive overview of both the clinical and technological advantages and challenges associated with oral cancer detection through salivary biomarkers.
      Citation: Biosensors
      PubDate: 2021-10-15
      DOI: 10.3390/bios11100396
      Issue No: Vol. 11, No. 10 (2021)
  • Biosensors, Vol. 11, Pages 397: Computer Simulation of a Surface Charge
           Nanobiosensor with Internal Signal Integration

    • Authors: Dmitry Dyubo, Oleg Yu. Tsybin
      First page: 397
      Abstract: The ionized states of molecular analytes located on solid surfaces require profound investigation and better understanding for applications in the basic sciences in general, and in the design of nanobiosensors, in particular. Such ionized states are induced by the interactions of molecules between them in the analyzed substance and with the target surface. Here, computer simulations using COMSOL Multiphysics software show the effect of surface charge density and distribution on the output generation in a dynamic PIN diode with gate control. This device, having built-in potential barriers, has a unique internal integration of output signal generation. The identified interactions showed the possibility of a new design for implementing a nanobiosensor based on a dynamic PIN diode in a mode with surface charge control.
      Citation: Biosensors
      PubDate: 2021-10-16
      DOI: 10.3390/bios11100397
      Issue No: Vol. 11, No. 10 (2021)
  • Biosensors, Vol. 11, Pages 398: Electrical Impedance of Upper Limb Enables
           Robust Wearable Identity Recognition against Variation in Finger Placement
           and Environmental Factors

    • Authors: Hyung Wook Noh, Joo Yong Sim, Chang-Geun Ahn, Yunseo Ku
      First page: 398
      Abstract: Most biometric authentication technologies commercialized in various fields mainly rely on acquired images of structural information, such as fingerprints, irises, and faces. However, bio-recognition techniques using these existing physical features are always at risk of template forgery threats, such as fake fingerprints. Due to the risk of theft and duplication, studies have recently been attempted using the internal structure and biological characteristics of the human body, including our previous works on the ratiometric biological impedance feature. However, one may still question its accuracy in real-life use due to the artifacts from sensing position variability and electrode–skin interfacing noise. Moreover, since the finger possesses more severe thermoregulatory vasomotion and large variability in the tissue properties than the core of the body, it is necessary to mitigate the harsh changes occurring at the peripheral extremities of the human body. To address these challenges, we propose a biometric authentication method through robust feature extraction from the upper-limb impedance acquired based on a portable wearable device. In this work, we show that the upper limb impedance features obtained from wearable devices are robust against undesirable factors such as finger placement deviations and day-to-day physiological changes, along with ratiometric impedance features. Overall, our upper-limb impedance-based analysis in a dataset of 1627 measurement from 33 subjects lowered the classification error rate from 22.38% to 4.3% (by a factor of 5), and further down to 2.4% (by a factor of 9) when combined with the ratiometric features.
      Citation: Biosensors
      PubDate: 2021-10-16
      DOI: 10.3390/bios11100398
      Issue No: Vol. 11, No. 10 (2021)
  • Biosensors, Vol. 11, Pages 399: Investigating the Regulation of Neural
           Differentiation and Injury in PC12 Cells Using Microstructure Topographic

    • Authors: Sun, Li, Gong, Hu, Ge, Wu, Gao
      First page: 399
      Abstract: In this study, we designed and manufactured a series of different microstructure topographical cues for inducing neuronal differentiation of cells in vitro, with different topography, sizes, and structural complexities. We cultured PC12 cells in these microstructure cues and then induced neural differentiation using nerve growth factor (NGF). The pheochromocytoma cell line PC12 is a validated neuronal cell model that is widely used to study neuronal differentiation. Relevant markers of neural differentiation and cytoskeletal F-actin were characterized. Cellular immunofluorescence detection and axon length analysis showed that the differentiation of PC12 cells was significantly different under different isotropic and anisotropic topographic cues. The expression differences of the growth cone marker growth-associated protein 43 (GAP-43) and sympathetic nerve marker tyrosine hydroxylase (TH) genes were also studied in different topographic cues. Our results revealed that the physical environment has an important influence on the differentiation of neuronal cells, and 3D constraints could be used to guide axon extension. In addition, the neurotoxin 6-hydroxydopamine (6-OHDA) was used to detect the differentiation and injury of PC12 cells under different topographic cues. Finally, we discussed the feasibility of combining the topographic cues and the microfluidic chip for neural differentiation research.
      Citation: Biosensors
      PubDate: 2021-10-16
      DOI: 10.3390/bios11100399
      Issue No: Vol. 11, No. 10 (2021)
  • Biosensors, Vol. 11, Pages 400: Self-Referenced Refractive Index
           Biosensing with Graphene Fano Resonance Modes

    • Authors: Xiaoyu Dai, Banxian Ruan, Yuanjiang Xiang
      First page: 400
      Abstract: A hybrid structure composed of periodic monolayer graphene nanoribbons and a dielectric multilayer structure was designed to generate a Fano resonance (FR). The strong interaction between the surface plasmon resonance of graphene and the dielectric waveguide mode results in the FR. The finite element method is utilized to investigate the behaviors of the FR, and it matches well with the theoretical calculations using rigorous coupled wave theory. The results demonstrate that the profile of the FR can be passively tuned by the period of the graphene nanoribbons and actively tuned by the Fermi level of the graphene. The decoupled nature of the FR gives it potential applications as a self-calibrated refractive index biosensor, and the sensitivity can reach as high as 4.615 μm/RIU. Thus, this work provides a new idea for an excellent self-referencing refractive index biosensor.
      Citation: Biosensors
      PubDate: 2021-10-17
      DOI: 10.3390/bios11100400
      Issue No: Vol. 11, No. 10 (2021)
  • Biosensors, Vol. 11, Pages 401: Dielectrophoretic and Electrical Impedance
           Differentiation of Cancerous Cells Based on Biophysical Phenotype

    • Authors: Ina Turcan, Iuliana Caras, Thomas Gabriel Schreiner, Catalin Tucureanu, Aurora Salageanu, Valentin Vasile, Marioara Avram, Bianca Tincu, Marius Andrei Olariu
      First page: 401
      Abstract: Here, we reported a study on the detection and electrical characterization of both cancer cell line and primary tumor cells. Dielectrophoresis (DEP) and electrical impedance spectroscopy (EIS) were jointly employed to enable the rapid and label-free differentiation of various cancer cells from normal ones. The primary tumor cells that were collected from two colorectal cancer patients and cancer cell lines (SW-403, Jurkat, and THP-1), and healthy peripheral blood mononuclear cells (PBMCs) were trapped first at the level of interdigitated microelectrodes with the help of dielectrophoresis. Correlation of the cells dielectric characteristics that was obtained via electrical impedance spectroscopy (EIS) allowed evident differentiation of the various types of cell. The differentiations were assigned to a “dielectric phenotype” based on their crossover frequencies. Finally, Randles equivalent circuit model was employed for highlighting the differences with regard to a series group of charge transport resistance and constant phase element for cancerous and normal cells.
      Citation: Biosensors
      PubDate: 2021-10-17
      DOI: 10.3390/bios11100401
      Issue No: Vol. 11, No. 10 (2021)
  • Biosensors, Vol. 11, Pages 402: Enhanced Plasmonic Biosensor Utilizing
           Paired Antibody and Label-Free Fe3O4 Nanoparticles for Highly Sensitive
           and Selective Detection of Parkinson’s α-Synuclein in Serum

    • Authors: Samuel Husin Surya Mandala, Tai-Jan Liu, Chiung-Mei Chen, Kuo-Kang Liu, Mochamad Januar, Ying-Feng Chang, Chao-Sung Lai, Kuo-Hsuan Chang, Kou-Chen Liu
      First page: 402
      Abstract: Parkinson’s disease (PD) is an acute and progressive neurodegenerative disorder, and diagnosis of the disease at its earliest stage is of paramount importance to improve the life expectancy of patients. α-Synuclein (α-syn) is a potential biomarker for the early diagnosis of PD, and there is a great need to develop a biosensing platform that precisely detects α-syn in human body fluids. Herein, we developed a surface plasmon resonance (SPR) biosensor based on the label-free iron oxide nanoparticles (Fe3O4 NPs) and paired antibody for the highly sensitive and selective detection of α-syn in serum samples. The sensitivity of the SPR platform is enhanced significantly by directly depositing Fe3O4 NPs on the Au surface at a high density to increase the decay length of the evanescent field on the Au film. Moreover, the utilization of rabbit-type monoclonal antibody (α-syn-RmAb) immobilized on Au films allows the SPR platform to have a high affinity-selectivity binding performance compared to mouse-type monoclonal antibodies as a common bioreceptor for capturing α-syn molecules. As a result, the current platform has a detection limit of 5.6 fg/mL, which is 20,000-fold lower than that of commercial ELISA. The improved sensor chip can also be easily regenerated to repeat the α-syn measurement with the same sensitivity. Furthermore, the SPR sensor was applied to the direct analysis of α-syn in serum samples. By using a format of paired α-syn-RmAb, the SPR sensor provides a recovery rate in the range from 94.5% to 104.3% to detect the α-syn in diluted serum samples precisely. This work demonstrates a highly sensitive and selective quantification approach to detect α-syn in human biofluids and paves the way for the future development in the early diagnosis of PD.
      Citation: Biosensors
      PubDate: 2021-10-18
      DOI: 10.3390/bios11100402
      Issue No: Vol. 11, No. 10 (2021)
  • Biosensors, Vol. 11, Pages 403: Biometric Identification of Taxodium spp.
           and Their Hybrid Progenies by Electrochemical Fingerprints

    • Authors: Yuhong Zheng, Da Wang, Xiaolong Li, Ziyang Wang, Qingwei Zhou, Li Fu, Yunlong Yin, David Creech
      First page: 403
      Abstract: The use of electrochemical fingerprints for plant identification is an emerging application in biosensors. In this work, Taxodium ascendens, T. distichum, T. mucronatum, and 18 of their hybrid progenies were collected for this purpose. This is the first attempt to use electrochemical fingerprinting for the identification of plant hybrid progeny. Electrochemical fingerprinting in the leaves of Taxodium spp. was recorded under two conditions. The results showed that the electrochemical fingerprints of each species and progeny possessed very suitable reproducibility. These electrochemical fingerprints represent the electrochemical behavior of electrochemically active substances in leaf tissues under specific conditions. Since these species and progenies are very closely related to each other, it is challenging to identify them directly using a particular electrochemical fingerprinting. Therefore, electrochemical fingerprints measured under different conditions were used to perform pattern recognition. We can identify different species and progenies by locating the features in different pattern maps. We also performed a phylogenetic study with data from electrochemical fingerprinting. The results proved that the electrochemical classification results and the relationship between them are closely related.
      Citation: Biosensors
      PubDate: 2021-10-18
      DOI: 10.3390/bios11100403
      Issue No: Vol. 11, No. 10 (2021)
  • Biosensors, Vol. 11, Pages 404: Chronic Study on Brainwave Authentication
           in a Real-Life Setting: An LSTM-Based Bagging Approach

    • Authors: Liuyin Yang, Arno Libert, Marc M. Van Van Hulle
      First page: 404
      Abstract: With the advent of the digital age, concern about how to secure authorized access to sensitive data is increasing. Besides traditional authentication methods, there is an interest in biometric traits such as fingerprints, the iris, facial characteristics, and, recently, brainwaves, primarily based on electroencephalography (EEG). Current work on EEG-based authentication focuses on acute recordings in laboratory settings using high-end equipment, typically equipped with 64 channels and operating at a high sampling rate. In this work, we validated the feasibility of EEG-based authentication in a real-world, out-of-laboratory setting using a commercial dry-electrode EEG headset and chronic recordings on a population of 15 healthy people. We used an LSTM-based network with bootstrap aggregating (bagging) to decode our recordings in response to a multitask scheme consisting of performed and imagined motor tasks, and showed that it improved the performance of the standard LSTM approach. We achieved an authentication accuracy, false acceptance rate (FAR), and false rejection rate (FRR) of 92.6%, 2.5%, and 5.0% for the performed motor task; 92.5%, 2.6%, and 4.9% for the imagined motor task; and 93.0%, 1.9%, and 5.1% for the combined tasks, respectively. We recommend the proposed method for time- and data-limited scenarios.
      Citation: Biosensors
      PubDate: 2021-10-18
      DOI: 10.3390/bios11100404
      Issue No: Vol. 11, No. 10 (2021)
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