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  Subjects -> CHEMISTRY (Total: 846 journals)
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    - CHEMISTRY (597 journals)
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CHEMISTRY (597 journals)                  1 2 3 | Last

Showing 1 - 200 of 735 Journals sorted alphabetically
2D Materials     Hybrid Journal   (Followers: 7)
Accreditation and Quality Assurance: Journal for Quality, Comparability and Reliability in Chemical Measurement     Hybrid Journal   (Followers: 26)
ACS Catalysis     Full-text available via subscription   (Followers: 31)
ACS Chemical Neuroscience     Full-text available via subscription   (Followers: 17)
ACS Combinatorial Science     Full-text available via subscription   (Followers: 23)
ACS Macro Letters     Full-text available via subscription   (Followers: 22)
ACS Medicinal Chemistry Letters     Full-text available via subscription   (Followers: 39)
ACS Nano     Full-text available via subscription   (Followers: 217)
ACS Photonics     Full-text available via subscription   (Followers: 10)
ACS Synthetic Biology     Full-text available via subscription   (Followers: 20)
Acta Chemica Iasi     Open Access   (Followers: 2)
Acta Chimica Sinica     Full-text available via subscription  
Acta Chimica Slovaca     Open Access   (Followers: 1)
Acta Chromatographica     Full-text available via subscription   (Followers: 9)
Acta Facultatis Medicae Naissensis     Open Access  
Acta Metallurgica Sinica (English Letters)     Hybrid Journal   (Followers: 5)
Acta Scientifica Naturalis     Open Access   (Followers: 2)
adhäsion KLEBEN & DICHTEN     Hybrid Journal   (Followers: 5)
Adhesion Adhesives & Sealants     Hybrid Journal   (Followers: 7)
Adsorption Science & Technology     Full-text available via subscription   (Followers: 5)
Advanced Functional Materials     Hybrid Journal   (Followers: 48)
Advanced Science Focus     Free   (Followers: 3)
Advances in Chemical Engineering and Science     Open Access   (Followers: 53)
Advances in Chemical Science     Open Access   (Followers: 12)
Advances in Chemistry     Open Access   (Followers: 12)
Advances in Colloid and Interface Science     Full-text available via subscription   (Followers: 18)
Advances in Drug Research     Full-text available via subscription   (Followers: 22)
Advances in Enzyme Research     Open Access   (Followers: 10)
Advances in Fluorine Science     Full-text available via subscription   (Followers: 8)
Advances in Fuel Cells     Full-text available via subscription   (Followers: 14)
Advances in Heterocyclic Chemistry     Full-text available via subscription   (Followers: 8)
Advances in Materials Physics and Chemistry     Open Access   (Followers: 18)
Advances in Nanoparticles     Open Access   (Followers: 12)
Advances in Organometallic Chemistry     Full-text available via subscription   (Followers: 15)
Advances in Polymer Science     Hybrid Journal   (Followers: 40)
Advances in Protein Chemistry     Full-text available via subscription   (Followers: 18)
Advances in Protein Chemistry and Structural Biology     Full-text available via subscription   (Followers: 18)
Advances in Quantum Chemistry     Full-text available via subscription   (Followers: 5)
Advances in Science and Technology     Full-text available via subscription   (Followers: 10)
African Journal of Bacteriology Research     Open Access  
African Journal of Chemical Education     Open Access   (Followers: 2)
African Journal of Pure and Applied Chemistry     Open Access   (Followers: 7)
Agrokémia és Talajtan     Full-text available via subscription   (Followers: 2)
Alkaloids: Chemical and Biological Perspectives     Full-text available via subscription   (Followers: 3)
AMB Express     Open Access   (Followers: 1)
Ambix     Hybrid Journal   (Followers: 3)
American Journal of Biochemistry and Biotechnology     Open Access   (Followers: 65)
American Journal of Biochemistry and Molecular Biology     Open Access   (Followers: 14)
American Journal of Chemistry     Open Access   (Followers: 25)
American Journal of Plant Physiology     Open Access   (Followers: 13)
American Mineralogist     Full-text available via subscription   (Followers: 12)
Analyst     Full-text available via subscription   (Followers: 38)
Angewandte Chemie     Hybrid Journal   (Followers: 153)
Angewandte Chemie International Edition     Hybrid Journal   (Followers: 203)
Annales UMCS, Chemia     Open Access   (Followers: 1)
Annals of Clinical Chemistry and Laboratory Medicine     Open Access   (Followers: 1)
Annual Reports in Computational Chemistry     Full-text available via subscription   (Followers: 3)
Annual Reports Section A (Inorganic Chemistry)     Full-text available via subscription   (Followers: 3)
Annual Reports Section B (Organic Chemistry)     Full-text available via subscription   (Followers: 7)
Annual Review of Chemical and Biomolecular Engineering     Full-text available via subscription   (Followers: 12)
Annual Review of Food Science and Technology     Full-text available via subscription   (Followers: 14)
Anti-Infective Agents     Hybrid Journal   (Followers: 3)
Antiviral Chemistry and Chemotherapy     Hybrid Journal  
Applied Organometallic Chemistry     Hybrid Journal   (Followers: 6)
Applied Spectroscopy     Full-text available via subscription   (Followers: 22)
Applied Surface Science     Hybrid Journal   (Followers: 26)
Arabian Journal of Chemistry     Open Access   (Followers: 6)
ARKIVOC     Open Access   (Followers: 2)
Asian Journal of Biochemistry     Open Access   (Followers: 1)
Atomization and Sprays     Full-text available via subscription   (Followers: 3)
Australian Journal of Chemistry     Hybrid Journal   (Followers: 7)
Autophagy     Hybrid Journal   (Followers: 2)
Avances en Quimica     Open Access   (Followers: 1)
Biochemical Pharmacology     Hybrid Journal   (Followers: 9)
Biochemistry     Full-text available via subscription   (Followers: 277)
Biochemistry Insights     Open Access   (Followers: 5)
Biochemistry Research International     Open Access   (Followers: 6)
BioChip Journal     Hybrid Journal  
Bioinorganic Chemistry and Applications     Open Access   (Followers: 9)
Bioinspired Materials     Open Access   (Followers: 3)
Biointerface Research in Applied Chemistry     Open Access   (Followers: 2)
Biointerphases     Open Access   (Followers: 1)
Biology, Medicine, & Natural Product Chemistry     Open Access  
Biomacromolecules     Full-text available via subscription   (Followers: 18)
Biomass Conversion and Biorefinery     Partially Free   (Followers: 10)
Biomedical Chromatography     Hybrid Journal   (Followers: 6)
Biomolecular NMR Assignments     Hybrid Journal   (Followers: 3)
BioNanoScience     Partially Free   (Followers: 4)
Bioorganic & Medicinal Chemistry     Hybrid Journal   (Followers: 107)
Bioorganic & Medicinal Chemistry Letters     Hybrid Journal   (Followers: 99)
Bioorganic Chemistry     Hybrid Journal   (Followers: 10)
Biopolymers     Hybrid Journal   (Followers: 18)
Biosensors     Open Access   (Followers: 2)
Biotechnic and Histochemistry     Hybrid Journal   (Followers: 1)
Bitácora Digital     Open Access  
Boletin de la Sociedad Chilena de Quimica     Open Access  
Bulletin of the Chemical Society of Ethiopia     Open Access   (Followers: 2)
Bulletin of the Chemical Society of Japan     Full-text available via subscription   (Followers: 24)
Bulletin of the Korean Chemical Society     Hybrid Journal   (Followers: 1)
C - Journal of Carbon Research     Open Access   (Followers: 2)
Canadian Association of Radiologists Journal     Full-text available via subscription   (Followers: 2)
Canadian Journal of Chemistry     Full-text available via subscription   (Followers: 10)
Canadian Mineralogist     Full-text available via subscription   (Followers: 3)
Carbohydrate Research     Hybrid Journal   (Followers: 26)
Carbon     Hybrid Journal   (Followers: 67)
Catalysis for Sustainable Energy     Open Access   (Followers: 6)
Catalysis Reviews: Science and Engineering     Hybrid Journal   (Followers: 8)
Catalysis Science and Technology     Free   (Followers: 6)
Catalysis Surveys from Asia     Hybrid Journal   (Followers: 3)
Catalysts     Open Access   (Followers: 7)
Cellulose     Hybrid Journal   (Followers: 7)
Cereal Chemistry     Full-text available via subscription   (Followers: 4)
ChemBioEng Reviews     Full-text available via subscription   (Followers: 1)
ChemCatChem     Hybrid Journal   (Followers: 8)
Chemical and Engineering News     Free   (Followers: 12)
Chemical Bulletin of Kazakh National University     Open Access  
Chemical Communications     Full-text available via subscription   (Followers: 69)
Chemical Engineering Research and Design     Hybrid Journal   (Followers: 23)
Chemical Research in Chinese Universities     Hybrid Journal   (Followers: 3)
Chemical Research in Toxicology     Full-text available via subscription   (Followers: 19)
Chemical Reviews     Full-text available via subscription   (Followers: 165)
Chemical Science     Open Access   (Followers: 21)
Chemical Technology     Open Access   (Followers: 15)
Chemical Vapor Deposition     Hybrid Journal   (Followers: 4)
Chemical Week     Full-text available via subscription   (Followers: 7)
Chemie in Unserer Zeit     Hybrid Journal   (Followers: 55)
Chemie-Ingenieur-Technik (Cit)     Hybrid Journal   (Followers: 25)
ChemInform     Hybrid Journal   (Followers: 7)
Chemistry & Biodiversity     Hybrid Journal   (Followers: 6)
Chemistry & Biology     Full-text available via subscription   (Followers: 30)
Chemistry & Industry     Hybrid Journal   (Followers: 5)
Chemistry - A European Journal     Hybrid Journal   (Followers: 136)
Chemistry - An Asian Journal     Hybrid Journal   (Followers: 15)
Chemistry and Materials Research     Open Access   (Followers: 17)
Chemistry Central Journal     Open Access   (Followers: 4)
Chemistry Education Research and Practice     Free   (Followers: 5)
Chemistry in Education     Open Access   (Followers: 9)
Chemistry International     Hybrid Journal   (Followers: 2)
Chemistry Letters     Full-text available via subscription   (Followers: 43)
Chemistry of Materials     Full-text available via subscription   (Followers: 189)
Chemistry of Natural Compounds     Hybrid Journal   (Followers: 9)
Chemistry-Didactics-Ecology-Metrology     Open Access  
ChemistryOpen     Open Access   (Followers: 2)
Chemkon - Chemie Konkret, Forum Fuer Unterricht Und Didaktik     Hybrid Journal  
Chemoecology     Hybrid Journal   (Followers: 2)
Chemometrics and Intelligent Laboratory Systems     Hybrid Journal   (Followers: 15)
Chemosensors     Open Access  
ChemPhysChem     Hybrid Journal   (Followers: 8)
ChemPlusChem     Hybrid Journal   (Followers: 2)
ChemTexts     Hybrid Journal  
CHIMIA International Journal for Chemistry     Full-text available via subscription   (Followers: 2)
Chinese Journal of Chemistry     Hybrid Journal   (Followers: 6)
Chinese Journal of Polymer Science     Hybrid Journal   (Followers: 10)
Chromatographia     Hybrid Journal   (Followers: 23)
Chromatography Research International     Open Access   (Followers: 7)
Clay Minerals     Full-text available via subscription   (Followers: 9)
Cogent Chemistry     Open Access  
Colloid and Interface Science Communications     Open Access  
Colloid and Polymer Science     Hybrid Journal   (Followers: 10)
Colloids and Surfaces B: Biointerfaces     Hybrid Journal   (Followers: 8)
Combinatorial Chemistry & High Throughput Screening     Hybrid Journal   (Followers: 3)
Combustion Science and Technology     Hybrid Journal   (Followers: 18)
Comments on Inorganic Chemistry: A Journal of Critical Discussion of the Current Literature     Hybrid Journal   (Followers: 2)
Composite Interfaces     Hybrid Journal   (Followers: 6)
Comprehensive Chemical Kinetics     Full-text available via subscription   (Followers: 2)
Comptes Rendus Chimie     Full-text available via subscription  
Comptes Rendus Physique     Full-text available via subscription   (Followers: 1)
Computational and Theoretical Chemistry     Hybrid Journal   (Followers: 9)
Computational Biology and Chemistry     Hybrid Journal   (Followers: 12)
Computational Chemistry     Open Access   (Followers: 2)
Computers & Chemical Engineering     Hybrid Journal   (Followers: 9)
Coordination Chemistry Reviews     Full-text available via subscription   (Followers: 2)
Copernican Letters     Open Access  
Critical Reviews in Biochemistry and Molecular Biology     Hybrid Journal   (Followers: 5)
Crystal Structure Theory and Applications     Open Access   (Followers: 3)
CrystEngComm     Full-text available via subscription   (Followers: 10)
Current Catalysis     Hybrid Journal   (Followers: 2)
Current Metabolomics     Hybrid Journal   (Followers: 4)
Current Opinion in Colloid & Interface Science     Hybrid Journal   (Followers: 9)
Current Research in Chemistry     Open Access   (Followers: 8)
Current Science     Open Access   (Followers: 48)
Dalton Transactions     Full-text available via subscription   (Followers: 18)
Detection     Open Access   (Followers: 2)
Developments in Geochemistry     Full-text available via subscription   (Followers: 2)
Diamond and Related Materials     Hybrid Journal   (Followers: 11)
Dislocations in Solids     Full-text available via subscription  
Doklady Chemistry     Hybrid Journal  
Drying Technology: An International Journal     Hybrid Journal   (Followers: 3)
Eclética Química     Open Access   (Followers: 1)
Ecological Chemistry and Engineering S     Open Access   (Followers: 4)
Ecotoxicology and Environmental Contamination     Open Access  
Educación Química     Open Access   (Followers: 1)
Education for Chemical Engineers     Hybrid Journal   (Followers: 5)
EJNMMI Radiopharmacy and Chemistry     Open Access  
Elements     Full-text available via subscription   (Followers: 2)
Environmental Chemistry     Hybrid Journal   (Followers: 8)
Environmental Chemistry Letters     Hybrid Journal   (Followers: 4)
Environmental Science & Technology Letters     Full-text available via subscription   (Followers: 5)
Environmental Science : Nano     Partially Free   (Followers: 1)
Environmental Toxicology & Chemistry     Hybrid Journal   (Followers: 19)

        1 2 3 | Last

Journal Cover Biosensors
  [SJR: 0.618]   [H-I: 12]   [2 followers]  Follow
    
  This is an Open Access Journal Open Access journal
   ISSN (Print) 2079-6374
   Published by MDPI Homepage  [148 journals]
  • Biosensors, Vol. 7, Pages 15: Detection of 17 β-Estradiol in
           Environmental Samples and for Health Care Using a Single-Use,
           Cost-Effective Biosensor Based on Differential Pulse Voltammetry (DPV)

    • Authors: Yifan Dai, Chung Liu
      First page: 15
      Abstract: Environmental estrogen pollution and estrogen effects on the female reproductive system are well recognized scientifically. Among the estrogens, 17 β-estradiol is a priority in environmental estrogen pollution, and it is also a major contributor to estrogen which regulates the female reproductive system. 17 β-estradiol is carcinogenic and has a tumor promotion effect relating to breast cancer, lung cancer and others. It also affects psychological well-being such as depression, fatigue and others. Thus, a simple method of detecting 17 β-estradiol will be important for both environmental estrogen pollution and health care. This study demonstrates a single-use, cost-effective 17 β-estradiol biosensor system which can be used for both environmental and health care applications. The bio-recognition mechanism is based on the influence of the redox couple, K3Fe(CN)6/K4Fe(CN)6 by the interaction between 17 β-estradiol antigen and its α-receptor (ER-α; α-estrogen antibody). The transduction mechanism is an electrochemical analytical technique, differential pulse voltammetry (DPV). The levels of 17 β-estradiol antigen studied were between 2.25 pg/mL and 2250 pg/mL; Phosphate buffered saline (PBS), tap water from the Cleveland regional water district, and simulated urine were used as the test media covering the potential application areas for 17 β-estradiol detection. An interference study by testosterone, which has a similar chemical structure and molecular weight as those of 17 β-estradiol, was carried out, and this 17 β-estradiol biosensor showed excellent specificity without any interference by similar chemicals.
      PubDate: 2017-03-29
      DOI: 10.3390/bios7020015
      Issue No: Vol. 7, No. 2 (2017)
       
  • Biosensors, Vol. 7, Pages 16: Electrochemical Field-Effect Transistor
           Utilization to Study the Coupling Success Rate of Photosynthetic Protein
           Complexes to Cytochrome c

    • Authors: Arash Takshi, Houman Yaghoubi, Jing Wang, Daniel Jun, J. Beatty
      First page: 16
      Abstract: Due to the high internal quantum efficiency, reaction center (RC) proteins from photosynthetic organisms have been studied in various bio-photoelectrochemical devices for solar energy harvesting. In vivo, RC and cytochrome c (cyt c; a component of the biological electron transport chain) can form a cocomplex via interprotein docking. This mechanism can be used in vitro for efficient electron transfer from an electrode to the RC in a bio-photoelectrochemical device. Hence, the success rate in coupling RCs to cyt c is of great importance for practical applications in the future. In this work, we use an electrochemical transistor to study the binding of the RC to cytochrome. The shift in the transistor threshold voltage was measured in the dark and under illumination to estimate the density of cytochrome and coupled RCs on the gate of the transistor. The results show that ~33% of the cyt cs on the transistor gate were able to effectively couple with RCs. Due to the high sensitivity of the transistor, the approach can be used to make photosensors for detecting low light intensities.
      PubDate: 2017-03-30
      DOI: 10.3390/bios7020016
      Issue No: Vol. 7, No. 2 (2017)
       
  • Biosensors, Vol. 7, Pages 17: Ultrasensitive Label-Free Sensing of IL-6
           Based on PASE Functionalized Carbon Nanotube Micro-Arrays with
           RNA-Aptamers as Molecular Recognition Elements

    • Authors: Farhad Khosravi, Seyed Loeian, Balaji Panchapakesan
      First page: 17
      Abstract: This study demonstrates the rapid and label-free detection of Interleukin-6 (IL-6) using carbon nanotube micro-arrays with aptamer as the molecular recognition element. Single wall carbon nanotubes micro-arrays biosensors were manufactured using photo-lithography, metal deposition, and etching techniques. Nanotube biosensors were functionalized with 1-Pyrenebutanoic Acid Succinimidyl Ester (PASE) conjugated IL-6 aptamers. Real time response of the sensor conductance was monitored with increasing concentration of IL-6 (1 pg/mL to 10 ng/mL), exposure to the sensing surface in buffer solution, and clinically relevant spiked blood samples. Non-specific Bovine Serum Albumin (BSA), PBS samples, and anti-IgG functionalized devices gave similar signatures in the real time conductance versus time experiments with no significant change in sensor signal. Exposure of the aptamer functionalized nanotube surface to IL-6 decreased the conductance with increasing concentration of IL-6. Experiments based on field effect transistor arrays suggested shift in drain current versus gate voltage for 1 pg and 1 ng of IL-6 exposure. Non-specific BSA did not produce any appreciable shift in the Ids versus Vg suggesting specific interactions of IL-6 on PASE conjugated aptamer surface gave rise to the change in electrical signal. Both Z axis and phase image in an Atomic Force Microscope (AFM) suggested unambiguous molecular interaction of the IL-6 on the nanotube-aptamer surface at 1 pg/mL concentration. The concentration of 1 pg falls below the diagnostic gray zone for cancer (2.3 pg-4 ng/mL), which is an indicator of early stage cancer. Thus, nanotube micro-arrays could potentially be developed for creating multiplexed assays involving cancer biomarker proteins and possibly circulating tumor cells all in a single assay using PASE functionalization protocol.
      PubDate: 2017-04-17
      DOI: 10.3390/bios7020017
      Issue No: Vol. 7, No. 2 (2017)
       
  • Biosensors, Vol. 7, Pages 18: Erratum: Irvine, G.W.; Tan, S.N.; Stillman,
           M.J. A Simple Metallothionein-Based Biosensor for Enhanced Detection of
           Arsenic and Mercury. Biosensors 2017, 7, 14

    • Authors: Biosensors Editorial Office
      First page: 18
      Abstract: n/a
      PubDate: 2017-05-05
      DOI: 10.3390/bios7020018
      Issue No: Vol. 7, No. 2 (2017)
       
  • Biosensors, Vol. 7, Pages 19: A Label-Free, Quantitative Fecal Hemoglobin
           Detection Platform for Colorectal Cancer Screening

    • Authors: Gita Soraya, Thanh Nguyen, Chathurika Abeyrathne, Duc Huynh, Jianxiong Chan, Phuong Nguyen, Babak Nasr, Gursharan Chana, Patrick Kwan, Efstratios Skafidas
      First page: 19
      Abstract: The early detection of colorectal cancer is vital for disease management and patient survival. Fecal hemoglobin detection is a widely-adopted method for screening and early diagnosis. Fecal Immunochemical Test (FIT) is favored over the older generation chemical based Fecal Occult Blood Test (FOBT) as it does not require dietary or drug restrictions, and is specific to human blood from the lower digestive tract. To date, no quantitative FIT platforms are available for use in the point-of-care setting. Here, we report proof of principle data of a novel low cost quantitative fecal immunochemical-based biosensor platform that may be further developed into a point-of-care test in low-resource settings. The label-free prototype has a lower limit of detection (LOD) of 10 µg hemoglobin per gram (Hb/g) of feces, comparable to that of conventional laboratory based quantitative FIT diagnostic systems.
      PubDate: 2017-05-05
      DOI: 10.3390/bios7020019
      Issue No: Vol. 7, No. 2 (2017)
       
  • Biosensors, Vol. 7, Pages 20: Raman Spectroscopy of Head and Neck Cancer:
           Separation of Malignant and Healthy Tissue Using Signatures Outside the
           “Fingerprint” Region

    • Authors: Stephen Holler, Elaina Mansley, Christopher Mazzeo, Michael Donovan, Maximiliano Sobrero, Brett Miles
      First page: 20
      Abstract: The ability to rapidly and accurately discriminate between healthy and malignant tissue offers surgeons a tool for in vivo analysis that would potentially reduce operating time, facilitate quicker recovery, and improve patient outcomes. To this end, we investigate discrimination between diseased tissue and adjacent healthy controls from patients with head and neck cancer using near-infrared Raman spectroscopy. Our results indicate previously unreported peaks in the Raman spectra that lie outside the conventional “fingerprint” region (400 cm-1–1800 cm -1) played an important role in our analysis and in discriminating between the tissue classes. Preliminary multivariate statistical analyses of the Raman spectra indicate that discrimination between diseased and healthy tissue is possible based on these peaks.
      PubDate: 2017-05-14
      DOI: 10.3390/bios7020020
      Issue No: Vol. 7, No. 2 (2017)
       
  • Biosensors, Vol. 7, Pages 2: Design and Development of Non-Contact
           Bio-Potential Electrodes for Pervasive Health Monitoring Applications

    • Authors: Anthony Portelli, Slawomir Nasuto
      First page: 2
      Abstract: For the advent of pervasive bio-potential monitoring, it will be necessary to utilize a combination of cheap, quick to apply, low-noise electrodes and compact electronics with wireless technologies. Once available, all electrical activity resulting from the processes of the human body could be actively and constantly monitored without the need for cumbersome application and maintenance. This could significantly improve the early diagnosis of a range of different conditions in high-risk individuals, opening the possibility for new treatments and interventions as conditions develop. This paper presents the design and implementation of compact, non-contact capacitive bio-potential electrodes utilising a low impedance current-to-voltage configuration and a bootstrapped voltage follower, demonstrating results applicable to research applications for capacitive electrocardiography and capacitive electromyography. The presented electrodes use few components, have a small surface area and are capable of acquiring a range of bio-potential signals.
      PubDate: 2017-01-01
      DOI: 10.3390/bios7010002
      Issue No: Vol. 7, No. 1 (2017)
       
  • Biosensors, Vol. 7, Pages 3: A Strategy to Establish a Quality
           Assurance/Quality Control Plan for the Application of Biosensors for the
           Detection of E. coli in Water

    • Authors: Nikou Hesari, Nursel Kıratlı Yılmazçoban, Mohamad Elzein, Absar Alum, Morteza Abbaszadegan
      First page: 3
      Abstract: Rapid bacterial detection using biosensors is a novel approach for microbiological testing applications. Validation of such methods is an obstacle in the adoption of new bio-sensing technologies for water testing. Therefore, establishing a quality assurance and quality control (QA/QC) plan is essential to demonstrate accuracy and reliability of the biosensor method for the detection of E. coli in drinking water samples. In this study, different reagents and assay conditions including temperatures, holding time, E. coli strains and concentrations, dissolving agents, salinity and pH effects, quality of substrates of various suppliers of 4-methylumbelliferyl glucuronide (MUG), and environmental water samples were included in the QA/QC plan and used in the assay optimization and documentation. Furthermore, the procedural QA/QC for the monitoring of drinking water samples was established to validate the performance of the biosensor platform for the detection of E. coli using a culture-based standard technique. Implementing the developed QA/QC plan, the same level of precision and accuracy was achieved using both the standard and the biosensor methods. The established procedural QA/QC for the biosensor will provide a reliable tool for a near real-time monitoring of E. coli in drinking water samples to both industry and regulatory authorities.
      PubDate: 2017-01-03
      DOI: 10.3390/bios7010003
      Issue No: Vol. 7, No. 1 (2017)
       
  • Biosensors, Vol. 7, Pages 4: Alternating Current-Dielectrophoresis
           Collection and Chaining of Phytoplankton on Chip: Comparison of Individual
           Species and Artificial Communities

    • Authors: Coralie Siebman, Orlin Velev, Vera Slaveykova
      First page: 4
      Abstract: The capability of alternating current (AC) dielectrophoresis (DEP) for on-chip capture and chaining of the three species representative of freshwater phytoplankton was evaluated. The effects of the AC field intensity, frequency and duration on the chaining efficiency and chain lengths of green alga Chlamydomonas reinhardtii, cyanobacterium Synechocystis sp. and diatom Cyclotella meneghiniana were characterized systematically. C. reinhardtii showed an increase of the chaining efficiency from 100 Hz to 500 kHz at all field intensities; C. meneghiniana presented a decrease of chaining efficiency from 100 Hz to 1 kHz followed by a significant increase from 1 kHz to 500 kHz, while Synechocystis sp. exhibited low chaining tendency at all frequencies and all field intensities. The experimentally-determined DEP response and cell alignment of each microorganism were in agreement with their effective polarizability. Mixtures of cells in equal proportion or 10-times excess of Synechocystis sp. showed important differences in terms of chaining efficiency and length of the chains compared with the results obtained when the cells were alone in suspension. While a constant degree of chaining was observed with the mixture of C. reinhardtii and C. meneghiniana, the presence of Synechocystis sp. in each mixture suppressed the formation of chains for the two other phytoplankton species. All of these results prove the potential of DEP to discriminate different phytoplankton species depending on their effective polarizability and to enable their manipulation, such as specific collection or separation in freshwater.
      PubDate: 2017-01-05
      DOI: 10.3390/bios7010004
      Issue No: Vol. 7, No. 1 (2017)
       
  • Biosensors, Vol. 7, Pages 5: Aptamer Sensors

    • Authors: Giovanna Marrazza
      First page: 5
      Abstract: In the last years, great progress has been accomplished in the development of aptamer sensors with different transducers. In order to improve the sensitivity of these biosensors, several methodologies have been employed. In this Special Issue, the state of art and the future trends in the field of aptamer sensors have been explored.
      PubDate: 2017-01-04
      DOI: 10.3390/bios7010005
      Issue No: Vol. 7, No. 1 (2017)
       
  • Biosensors, Vol. 7, Pages 6: Acknowledgement to Reviewers of Biosensors in
           2016

    • Authors: Biosensors Editorial Office
      First page: 6
      Abstract: The editors of Biosensors would like to express their sincere gratitude to the following reviewers for assessing manuscripts in 2016.[...]
      PubDate: 2017-01-10
      DOI: 10.3390/bios7010006
      Issue No: Vol. 7, No. 1 (2017)
       
  • Biosensors, Vol. 7, Pages 7: Surface-Enhanced Raman Scattering-Based
           Immunoassay Technologies for Detection of Disease Biomarkers

    • Authors: Joseph Smolsky, Sukhwinder Kaur, Chihiro Hayashi, Surinder Batra, Alexey Krasnoslobodtsev
      First page: 7
      Abstract: Detection of biomarkers is of vital importance in disease detection, management, and monitoring of therapeutic efficacy. Extensive efforts have been devoted to the development of novel diagnostic methods that detect and quantify biomarkers with higher sensitivity and reliability, contributing to better disease diagnosis and prognosis. When it comes to such devastating diseases as cancer, these novel powerful methods allow for disease staging as well as detection of cancer at very early stages. Over the past decade, there have been some advances in the development of platforms for biomarker detection of diseases. The main focus has recently shifted to the development of simple and reliable diagnostic tests that are inexpensive, accurate, and can follow a patient’s disease progression and therapy response. The individualized approach in biomarker detection has been also emphasized with detection of multiple biomarkers in body fluids such as blood and urine. This review article covers the developments in Surface-Enhanced Raman Scattering (SERS) and related technologies with the primary focus on immunoassays. Limitations and advantages of the SERS-based immunoassay platform are discussed. The article thoroughly describes all components of the SERS immunoassay and highlights the superior capabilities of SERS readout strategy such as high sensitivity and simultaneous detection of a multitude of biomarkers. Finally, it introduces recently developed strategies for in vivo biomarker detection using SERS.
      PubDate: 2017-01-12
      DOI: 10.3390/bios7010007
      Issue No: Vol. 7, No. 1 (2017)
       
  • Biosensors, Vol. 7, Pages 8: Composite Hydrogels with Engineered
           Microdomains for Optical Glucose Sensing at Low Oxygen Conditions

    • Authors: Lindsey Bornhoeft, Aniket Biswas, Michael McShane
      First page: 8
      Abstract: There is a growing need for advanced tools that enable frequent monitoring of biomarkers for precision medicine. In this work, we present a composite hydrogel-based system providing real-time optical bioanalyte monitoring. The responsive material, alginate-in-alginate (AnA), is comprised of an alginate hydrogel with embedded bioactive, nanofilm-coated phosphorescent microdomains; palladium tetracarboxyphenylporphyrin serves as an optical indicator, glucose oxidase as a model enzyme, and layer-by-layer deposited polyelectrolyte multilayers (PEMs) as the diffusion barrier. Glutaraldehyde crosslinking of the nanofilms resulted in a dramatic reduction in glucose diffusion (179%) while oxygen transport was not significantly affected. The responses of the AnA hydrogels to step changes of glucose at both ambient and physiological oxygen levels were evaluated, revealing controlled tuning of sensitivity and dynamic range. Stability, assessed by alternately exposing the responsive AnA hydrogels to extremely high and zero glucose concentrations, resulted in no significant difference in the response over 20 cycles. These AnA hydrogels represent an attractive approach to biosensing based on biocompatible materials that may be used as minimally-invasive, implantable devices capable of optical interrogation. The model glucose-responsive composite material studied in this work will serve as a template that can be translated for sensing additional analytes (e.g., lactate, urea, pyruvate, cholesterol) and can be used for monitoring other chronic conditions.
      PubDate: 2017-01-22
      DOI: 10.3390/bios7010008
      Issue No: Vol. 7, No. 1 (2017)
       
  • Biosensors, Vol. 7, Pages 9: Carbon Nanotubes as an Effective Opportunity
           for Cancer Diagnosis and Treatment

    • Authors: Alessandro Sanginario, Beatrice Miccoli, Danilo Demarchi
      First page: 9
      Abstract: Despite the current progresses of modern medicine, the resistance of malignant tumors to present medical treatments points to the necessity of developing new therapeutic approaches. In recent years, numerous studies have focused their attention on the promising use of nanomaterials, like iron oxide nanowires, zinc oxide or mesoporous silica nanoparticles, for cancer and metastasis treatment with the advantage of operating directly at the bio-molecular scale. Among them, carbon nanotubes emerged as valid candidates not only for drug delivery, but also as a valuable tool in cancer imaging and physical ablation. Nevertheless, deep investigations about carbon nanotubes’ potential bio-compatibility and cytotoxicity limits should be also critically addressed. In the present review, after introducing carbon nanotubes and their promising advantages and drawbacks for fighting cancer, we want to focus on the numerous and different ways in which they can assist to reach this goal. Specifically, we report on how they can be used not only for drug delivery purposes, but also as a powerful ally to develop effective contrast agents for tumors’ medical or photodynamic imaging, to perform direct physical ablation of metastasis, as well as gene therapy.
      PubDate: 2017-02-15
      DOI: 10.3390/bios7010009
      Issue No: Vol. 7, No. 1 (2017)
       
  • Biosensors, Vol. 7, Pages 10: A Single-Use, In Vitro Biosensor for the
           Detection of T-Tau Protein, A Biomarker of Neuro-Degenerative Disorders,
           in PBS and Human Serum Using Differential Pulse Voltammetry (DPV)

    • Authors: Yifan Dai, Alireza Molazemhosseini, Chung Liu
      First page: 10
      Abstract: A single-use, in vitro biosensor for the detection of T-Tau protein in phosphate-buffer saline (PBS) and undiluted human serum was designed, manufactured, and tested. Differential pulse voltammetry (DPV) served as the transduction mechanism. This biosensor consisted of three electrodes: working, counter, and reference electrodes fabricated on a PET sheet. Both working and counter electrodes were thin gold film, 10 nm in thickness. Laser ablation technique was used to define the size and structure of the biosensor. The biosensor was produced using cost-effective roll-to-roll process. Self-assembled monolayers (SAM) of 3-mercaptopropionic acid (MPA) were employed to covalently immobilize the anti-T-Tau (T-Tau antibody) on the gold working electrode. A carbodiimide conjugation approach using N-(3-dimethylaminopropyl)-N’-ethylcarbodiimide hydrochloride (EDC) and N–hydroxysuccinimide (NHS) cross-linked anti-T-Tau to the carboxylic groups on one end of the MPA. A T-Tau protein ladder with six isoforms was used in this study. The anti-T-Tau concentration used was 500,000 pg/mL. The T-Tau protein concentration ranged from 1000 pg/mL to 100,000 pg/mL. DPV measurements showed excellent responses, with a good calibration curve. Thus, a practical tool for simple detection of T-Tau protein, a biomarker of neuro-degenerative disorders, has been successfully developed. This tool could also be extended to detect other biomarkers for neuro-degenerative disorders, such as P-Tau protein and β-amyloid 42.
      PubDate: 2017-02-19
      DOI: 10.3390/bios7010010
      Issue No: Vol. 7, No. 1 (2017)
       
  • Biosensors, Vol. 7, Pages 11: State-of-the-Art Methods for Skeletal Muscle
           Glycogen Analysis in Athletes—The Need for Novel Non-Invasive Techniques
           

    • Authors: Jacob Greene, Julien Louis, Olga Korostynska, Alex Mason
      First page: 11
      Abstract: Muscle glycogen levels have a profound impact on an athlete’s sporting performance, thus measurement is vital. Carbohydrate manipulation is a fundamental component in an athlete’s lifestyle and is a critical part of elite performance, since it can provide necessary training adaptations. This paper provides a critical review of the current invasive and non-invasive methods for measuring skeletal muscle glycogen levels. These include the gold standard muscle biopsy, histochemical analysis, magnetic resonance spectroscopy, and musculoskeletal high frequency ultrasound, as well as pursuing future application of electromagnetic sensors in the pursuit of portable non-invasive quantification of muscle glycogen. This paper will be of interest to researchers who wish to understand the current and most appropriate techniques in measuring skeletal muscle glycogen. This will have applications both in the lab and in the field by improving the accuracy of research protocols and following the physiological adaptations to exercise.
      PubDate: 2017-02-23
      DOI: 10.3390/bios7010011
      Issue No: Vol. 7, No. 1 (2017)
       
  • Biosensors, Vol. 7, Pages 12: High Bacterial Agglutination Activity in a
           Single-CRD C-Type Lectin from Spodoptera exigua (Lepidoptera: Noctuidae)

    • Authors: Leila Gasmi, Juan Ferré, Salvador Herrero
      First page: 12
      Abstract: Lectins are carbohydrate-interacting proteins that play a pivotal role in multiple physiological and developmental aspects of all organisms. They can specifically interact with different bacterial and viral pathogens through carbohydrate-recognition domains (CRD). In addition, lectins are also of biotechnological interest because of their potential use as biosensors for capturing and identifying bacterial species. In this work, three C-type lectins from the Lepidoptera Spodoptera exigua were produced as recombinant proteins and their bacterial agglutination properties were characterized. The lowest protein concentration producing bacterial agglutination against a panel of different Gram+ and Gram− as well as their carbohydrate binding specificities was determined for the three lectins. One of these lectins, BLL2, was able to agglutinate cells from a broad range of bacterial species at an extremely low concentration, becoming a very interesting protein to be used as a biosensor or for other biotechnological applications involving bacterial capture.
      PubDate: 2017-03-01
      DOI: 10.3390/bios7010012
      Issue No: Vol. 7, No. 1 (2017)
       
  • Biosensors, Vol. 7, Pages 13: A Urea Potentiometric Biosensor Based on a
           Thiophene Copolymer

    • Authors: Cheng-Yuan Lai, Peter Foot, John Brown, Peter Spearman
      First page: 13
      Abstract: A potentiometric enzyme biosensor is a convenient detector for quantification of urea concentrations in industrial processes, or for monitoring patients with diabetes, kidney damage or liver malfunction. In this work, poly(3-hexylthiophene-co-3-thiopheneacetic acid) (P(3HT-co-3TAA)) was chemically synthesized, characterized and spin-coated onto conductive indium tin oxide (ITO) glass electrodes. Urease (Urs) was covalently attached to the smooth surface of this copolymer via carbodiimide coupling. The electrochemical behavior and stability of the modified Urs/P(3HT-co-3TAA)/ITO glass electrode were investigated by cyclic voltammetry, and the bound enzyme activity was confirmed by spectrophotometry. Potentiometric response studies indicated that this electrode could determine the concentration of urea in aqueous solutions, with a quasi-Nernstian response up to about 5 mM. No attempt was made to optimize the response speed; full equilibration occurred after 10 min, but the half-time for response was typically <1 min.
      PubDate: 2017-03-03
      DOI: 10.3390/bios7010013
      Issue No: Vol. 7, No. 1 (2017)
       
  • Biosensors, Vol. 7, Pages 14: A Simple Metallothionein-Based Biosensor for
           Enhanced Detection of Arsenic and Mercury

    • Authors: Gordon Irvine, Swee Tan, Martin Stillman
      First page: 14
      Abstract: Metallothioneins (MTs) are a family of cysteine-rich proteins whose biological roles include the regulation of essential metal ions and protection against the harmful effects of toxic metals. Due to its high affinity for many toxic, soft metals, recombinant human MT isoform 1a was incorporated into an electrochemical-based biosensor for the detection of As3+ and Hg2+. A simple design was chosen to maximize its potential in environmental monitoring and MT was physically adsorbed onto paper discs placed on screen-printed carbon electrodes (SPCEs). This system was tested with concentrations of arsenic and mercury typical of contaminated water sources ranging from 5 to 1000 ppb. The analytical performance of the MT-adsorbed paper discs on SPCEs demonstrated a greater than three-fold signal enhancement and a lower detection limit compared to blank SPCEs, 13 ppb for As3+ and 45 ppb for Hg2+. While not being as low as some of the recommended drinking water limits, the sensitivity of the simple MT-biosensor would be potentially useful in monitoring of areas of concern with a known contamination problem. This paper describes the ability of the metal binding protein metallothionein to enhance the effectiveness of a simple, low-cost electrochemical sensor.
      PubDate: 2017-03-13
      DOI: 10.3390/bios7010014
      Issue No: Vol. 7, No. 1 (2017)
       
  • Biosensors, Vol. 7, Pages 1: Versatile Flexible Graphene Multielectrode
           Arrays

    • Authors: Dmitry Kireev, Silke Seyock, Mathis Ernst, Vanessa Maybeck, Bernhard Wolfrum, Andreas Offenhäusser
      First page: 1
      Abstract: Graphene is a promising material possessing features relevant to bioelectronics applications. Graphene microelectrodes (GMEAs), which are fabricated in a dense array on a flexible polyimide substrate, were investigated in this work for their performance via electrical impedance spectroscopy. Biocompatibility and suitability of the GMEAs for extracellular recordings were tested by measuring electrical activities from acute heart tissue and cardiac muscle cells. The recordings show encouraging signal-to-noise ratios of 65 ± 15 for heart tissue recordings and 20 ± 10 for HL-1 cells. Considering the low noise and excellent robustness of the devices, the sensor arrays are suitable for diverse and biologically relevant applications.
      PubDate: 2016-12-23
      DOI: 10.3390/bios7010001
      Issue No: Vol. 7, No. 1 (2016)
       
  • Biosensors, Vol. 6, Pages 49: Rapid, Portable, Multiplexed Detection of
           Bacterial Pathogens Directly from Clinical Sample Matrices

    • Authors: Christopher Phaneuf, Betty Mangadu, Matthew Piccini, Anup Singh, Chung-Yan Koh
      First page: 49
      Abstract: Enteric and diarrheal diseases are a major cause of childhood illness and death in countries with developing economies. Each year, more than half of a million children under the age of five die from these diseases. We have developed a portable, microfluidic platform capable of simultaneous, multiplexed detection of several of the bacterial pathogens that cause these diseases. This platform can perform fast, sensitive immunoassays directly from relevant, complex clinical matrices such as stool without extensive sample cleanup or preparation. Using only 1 µL of sample per assay, we demonstrate simultaneous multiplexed detection of four bacterial pathogens implicated in diarrheal and enteric diseases in less than 20 min.
      PubDate: 2016-09-23
      DOI: 10.3390/bios6040049
      Issue No: Vol. 6, No. 4 (2016)
       
  • Biosensors, Vol. 6, Pages 50: Recent Advances in the Fabrication and
           Application of Screen-Printed Electrochemical (Bio)Sensors Based on Carbon
           Materials for Biomedical, Agri-Food and Environmental Analyses

    • Authors: Gareth Hughes, Kelly Westmacott, Kevin Honeychurch, Adrian Crew, Roy Pemberton, John Hart
      First page: 50
      Abstract: This review describes recent advances in the fabrication of electrochemical (bio)sensors based on screen-printing technology involving carbon materials and their application in biomedical, agri-food and environmental analyses. It will focus on the various strategies employed in the fabrication of screen-printed (bio)sensors, together with their performance characteristics; the application of these devices for the measurement of selected naturally occurring biomolecules, environmental pollutants and toxins will be discussed.
      PubDate: 2016-09-28
      DOI: 10.3390/bios6040050
      Issue No: Vol. 6, No. 4 (2016)
       
  • Biosensors, Vol. 6, Pages 51: Biosensing with Paper-Based Miniaturized
           Printed Electrodes–A Modern Trend

    • Authors: Célia Silveira, Tiago Monteiro, Maria Almeida
      First page: 51
      Abstract: From the bench-mark work on microfluidics from the Whitesides’s group in 2007, paper technology has experienced significant growth, particularly regarding applications in biomedical research and clinical diagnostics. Besides the structural properties supporting microfluidics, other advantageous features of paper materials, including their versatility, disposability and low cost, show off the great potential for the development of advanced and eco-friendly analytical tools. Consequently, paper was quickly employed in the field of electrochemical sensors, being an ideal material for producing custom, tailored and miniaturized devices. Stencil-, inkjet-, or screen-printing are the preferential techniques for electrode manufacturing. Not surprisingly, we witnessed a rapid increase in the number of publications on paper based screen-printed sensors at the turn of the past decade. Among the sensing strategies, various biosensors, coupling electrochemical detectors with biomolecules, have been proposed. This work provides a critical review and a discussion on the future progress of paper technology in the context of miniaturized printed electrochemical biosensors.
      PubDate: 2016-09-28
      DOI: 10.3390/bios6040051
      Issue No: Vol. 6, No. 4 (2016)
       
  • Biosensors, Vol. 6, Pages 52: Kinetics of Antibody Binding to Membranes of
           Living Bacteria Measured by a Photonic Crystal-Based Biosensor

    • Authors: Ekaterina Rostova, Carine Ben Adiba, Giovanni Dietler, Sergey Sekatskii
      First page: 52
      Abstract: Optical biosensors based on photonic crystal surface waves (PC SWs) offer a possibility to study binding interactions with living cells, overcoming the limitation of rather small evanescent field penetration depth into a sample medium that is characteristic for typical optical biosensors. Besides this, simultaneous excitation of s- and p-polarized surface waves with different penetration depths is realized here, permitting unambiguous separation of surface and volume contributions to the measured signal. PC-based biosensors do not require a bulk signal correction, compared to widely used surface plasmon resonance-based devices. We developed a chitosan-based protocol of PC chip functionalization for bacterial attachment and performed experiments on antibody binding to living bacteria measured in real time by the PCSW-based biosensor. Data analysis reveals specific binding and gives the value of the dissociation constant for monoclonal antibodies (IgG2b) against bacterial lipopolysaccharides equal to KD = 6.2 ± 3.4 nM. To our knowledge, this is a first demonstration of antibody-binding kinetics to living bacteria by a label-free optical biosensor.
      PubDate: 2016-10-11
      DOI: 10.3390/bios6040052
      Issue No: Vol. 6, No. 4 (2016)
       
  • Biosensors, Vol. 6, Pages 53: Biofouling-Resistant Impedimetric Sensor for
           Array High-Resolution Extracellular Potassium Monitoring in the Brain

    • Authors: Ruben Machado, Nima Soltani, Suzie Dufour, Muhammad Salam, Peter Carlen, Roman Genov, Michael Thompson
      First page: 53
      Abstract: Extracellular potassium concentration, [K+]o, plays a fundamental role in the physiological functions of the brain. Studies investigating changes in [K+]o have predominantly relied upon glass capillary electrodes with K+-sensitive solution gradients for their measurements. However, such electrodes are unsuitable for taking spatio-temporal measurements and are limited by the surface area of their tips. We illustrate seizures invoked chemically and in optogenetically modified mice using blue light exposure while impedimetrically measuring the response. A sharp decrease of 1–2 mM in [K+]o before each spike has shown new physiological events not witnessed previously when measuring extracellular potassium concentrations during seizures in mice. We propose a novel approach that uses multichannel monolayer coated gold microelectrodes for in vivo spatio-temporal measurements of [K+]o in a mouse brain as an improvement to the conventional glass capillary electrode.
      PubDate: 2016-10-13
      DOI: 10.3390/bios6040053
      Issue No: Vol. 6, No. 4 (2016)
       
  • Biosensors, Vol. 6, Pages 54: Wrist Pulse Rate Monitor Using
           Self-Injection-Locked Radar Technology

    • Authors: Fu-Kang Wang, Mu-Cyun Tang, Sheng-Chao Su, Tzyy-Sheng Horng
      First page: 54
      Abstract: To achieve sensitivity, comfort, and durability in vital sign monitoring, this study explores the use of radar technologies in wearable devices. The study first detected the respiratory rates and heart rates of a subject at a one-meter distance using a self-injection-locked (SIL) radar and a conventional continuous-wave (CW) radar to compare the sensitivity versus power consumption between the two radars. Then, a pulse rate monitor was constructed based on a bistatic SIL radar architecture. This monitor uses an active antenna that is composed of a SIL oscillator (SILO) and a patch antenna. When attached to a band worn on the subject’s wrist, the active antenna can monitor the pulse on the subject’s wrist by modulating the SILO with the associated Doppler signal. Subsequently, the SILO’s output signal is received and demodulated by a remote frequency discriminator to obtain the pulse rate information.
      PubDate: 2016-10-26
      DOI: 10.3390/bios6040054
      Issue No: Vol. 6, No. 4 (2016)
       
  • Biosensors, Vol. 6, Pages 55: TERMA Framework for Biomedical Signal
           Analysis: An Economic-Inspired Approach

    • Authors: Mohamed Elgendi
      First page: 55
      Abstract: Biomedical signals contain features that represent physiological events, and each of these events has peaks. The analysis of biomedical signals for monitoring or diagnosing diseases requires the detection of these peaks, making event detection a crucial step in biomedical signal processing. Many researchers have difficulty detecting these peaks to investigate, interpret and analyze their corresponding events. To date, there is no generic framework that captures these events in a robust, efficient and consistent manner. A new method referred to for the first time as two event-related moving averages (“TERMA”) involves event-related moving averages and detects events in biomedical signals. The TERMA framework is flexible and universal and consists of six independent LEGO building bricks to achieve high accuracy detection of biomedical events. Results recommend that the window sizes for the two moving averages ( W 1 and W 2 ) have to follow the inequality ( 8 × W 1 ) ≥ W 2 ≥ ( 2 × W 1 ) . Moreover, TERMA is a simple yet efficient event detector that is suitable for wearable devices, point-of-care devices, fitness trackers and smart watches, compared to more complex machine learning solutions.
      PubDate: 2016-11-02
      DOI: 10.3390/bios6040055
      Issue No: Vol. 6, No. 4 (2016)
       
  • Biosensors, Vol. 6, Pages 56: Disposable Amperometric Immunosensor for the
           Determination of Human P53 Protein in Cell Lysates Using Magnetic
           Micro-Carriers

    • Authors: María Pedrero, F. Manuel de Villena, Cristina Muñoz-San Martín, Susana Campuzano, María Garranzo-Asensio, Rodrigo Barderas, José Pingarrón
      First page: 56
      Abstract: An amperometric magnetoimmunosensor for the determination of human p53 protein is described in this work using a sandwich configuration involving the covalent immobilization of a specific capture antibody onto activated carboxylic-modified magnetic beads (HOOC-MBs) and incubation of the modified MBs with a mixture of the target protein and horseradish peroxidase-labeled antibody (HRP-anti-p53). The resulting modified MBs are captured by a magnet placed under the surface of a disposable carbon screen-printed electrode (SPCE) and the amperometric responses are measured at −0.20 V (vs. an Ag pseudo-reference electrode), upon addition of hydroquinone (HQ) as a redox mediator and H2O2 as the enzyme substrate. The magnetoimmunosensing platform was successfully applied for the detection of p53 protein in different cell lysates without any matrix effect after a simple sample dilution. The results correlated accurately with those provided by a commercial ELISA kit, thus confirming the immunosensor as an attractive alternative for rapid and simple determination of this protein using portable and affordable instrumentation.
      PubDate: 2016-11-21
      DOI: 10.3390/bios6040056
      Issue No: Vol. 6, No. 4 (2016)
       
  • Biosensors, Vol. 6, Pages 57: Different Phases of Breast Cancer Cells:
           Raman Study of Immortalized, Transformed, and Invasive Cells

    • Authors: Deepika Chaturvedi, Sai Balaji, Vinay Bn, Freek Ariese, Siva Umapathy, Annapoorni Rangarajan
      First page: 57
      Abstract: Breast cancer is the most prevalent cause of cancer-associated death in women the world over, but if detected early it can be treated successfully. Therefore, it is important to diagnose this disease at an early stage and to understand the biochemical changes associated with cellular transformation and cancer progression. Deregulated lipid metabolism has been shown to contribute to cell transformation as well as cancer progression. In this study, we monitored the biomolecular changes associated with the transformation of a normal cell into an invasive cell associated with breast cancer using Raman microspectroscopy. We have utilized primary normal breast cells, and immortalized, transformed, non-invasive, and invasive breast cancer cells. The Raman spectra were acquired from all these cell lines under physiological conditions. The higher wavenumber (2800–3000 cm−1) and lower wavenumber (700–1800 cm−1) range of the Raman spectrum were analyzed and we observed increased lipid levels for invasive cells. The Raman spectral data were analyzed by principal component–linear discriminant analysis (PC-LDA), which resulted in the formation of distinct clusters for different cell types with a high degree of sensitivity. The subsequent testing of the PC-LDA analysis via the leave-one-out cross validation approach (LOOCV) yielded relatively high identification sensitivity. Additionally, the Raman spectroscopic results were confirmed through fluorescence staining tests with BODIPY and Nile Red biochemical assays. Furthermore, Raman maps from the above mentioned cells under fixed conditions were also acquired to visualize the distribution of biomolecules throughout the cell. The present study shows the suitability of Raman spectroscopy as a non-invasive, label-free, microspectroscopic technique, having the potential of probing changes in the biomolecular composition of living cells as well as fixed cells.
      PubDate: 2016-11-28
      DOI: 10.3390/bios6040057
      Issue No: Vol. 6, No. 4 (2016)
       
  • Biosensors, Vol. 6, Pages 58: Real-Time Classification of Patients with
           Balance Disorders vs. Normal Subjects Using a Low-Cost Small Wireless
           Wearable Gait Sensor

    • Authors: Bhargava Nukala, Taro Nakano, Amanda Rodriguez, Jerry Tsay, Jerry Lopez, Tam Nguyen, Steven Zupancic, Donald Lie
      First page: 58
      Abstract: Gait analysis using wearable wireless sensors can be an economical, convenient and effective way to provide diagnostic and clinical information for various health-related issues. In this work, our custom designed low-cost wireless gait analysis sensor that contains a basic inertial measurement unit (IMU) was used to collect the gait data for four patients diagnosed with balance disorders and additionally three normal subjects, each performing the Dynamic Gait Index (DGI) tests while wearing the custom wireless gait analysis sensor (WGAS). The small WGAS includes a tri-axial accelerometer integrated circuit (IC), two gyroscopes ICs and a Texas Instruments (TI) MSP430 microcontroller and is worn by each subject at the T4 position during the DGI tests. The raw gait data are wirelessly transmitted from the WGAS to a near-by PC for real-time gait data collection and analysis. In order to perform successful classification of patients vs. normal subjects, we used several different classification algorithms, such as the back propagation artificial neural network (BP-ANN), support vector machine (SVM), k-nearest neighbors (KNN) and binary decision trees (BDT), based on features extracted from the raw gait data of the gyroscopes and accelerometers. When the range was used as the input feature, the overall classification accuracy obtained is 100% with BP-ANN, 98% with SVM, 96% with KNN and 94% using BDT. Similar high classification accuracy results were also achieved when the standard deviation or other values were used as input features to these classifiers. These results show that gait data collected from our very low-cost wearable wireless gait sensor can effectively differentiate patients with balance disorders from normal subjects in real time using various classifiers, the success of which may eventually lead to accurate and objective diagnosis of abnormal human gaits and their underlying etiologies in the future, as more patient data are being collected.
      PubDate: 2016-11-29
      DOI: 10.3390/bios6040058
      Issue No: Vol. 6, No. 4 (2016)
       
  • Biosensors, Vol. 6, Pages 59: A Theoretical Study of Love Wave Sensors
           Based on ZnO–Glass Layered Structures for Application to Liquid
           Environments

    • Authors: Cinzia Caliendo, Muhammad Hamidullah
      First page: 59
      Abstract: The propagation of surface acoustic Love modes along ZnO/glass-based structures was modeled and analysed with the goal of designing a sensor able to detect changes in the environmental parameters, such as liquid viscosity changes and minute amounts of mass supported in the viscous liquid medium. Love mode propagation was modeled by numerically solving the system of coupled electro-mechanical field equations and Navier–Stokes equations. The phase and group velocities and the attenuation of the acoustic wave propagating along the 30° tilted c-axis ZnO/glass structure contacting a viscous non-conductive liquid were calculated for different ZnO guiding layer thicknesses, added mass thicknesses, and liquid viscosity and density. The three sensor responses, i.e., the wave phase and group velocity, and attenuation changes are calculated for different environmental parameters and related to the sensor velocity and attenuation sensitivities. The resulted sensitivities to liquid viscosity and added mass were optimized by adjusting the ZnO guiding layer thickness corresponding to a sensitivity peak. The present analysis is valuable for the manufacture and application of the ZnO-glass structure Love wave sensors for the detection of liquid properties, such as viscosity, density and mass anchored to the sensor surface.
      PubDate: 2016-12-02
      DOI: 10.3390/bios6040059
      Issue No: Vol. 6, No. 4 (2016)
       
  • Biosensors, Vol. 6, Pages 60: A Novel MOS Nanowire Gas Sensor Device (S3)
           and GC-MS-Based Approach for the Characterization of Grated Parmigiano
           Reggiano Cheese

    • Authors: Veronica Sberveglieri, Manohar Bhandari, Estefanía Núñez Carmona, Giulia Betto, Giorgio Sberveglieri
      First page: 60
      Abstract: To determine the originality of a typical Italian Parmigiano Reggiano cheese, it is crucial to define and characterize its quality, ripening period, and geographical origin. Different analytical techniques have been applied aimed at studying the organoleptic and characteristic volatile organic compounds (VOCs) profile of this cheese. However, most of the classical methods are time consuming and costly. The aim of this work was to illustrate a new simple, portable, fast, reliable, non-destructive, and economic sensor device S3 based on an array of six metal oxide semiconductor nanowire gas sensors to assess and discriminate the quality ranking of grated Parmigiano Reggiano cheese samples and to identify the VOC biomarkers using a headspace SPME-GC-MS. The device could clearly differentiate cheese samples varying in quality and ripening time when the results were analyzed by multivariate statistical analysis involving principal component analysis (PCA). Similarly, the volatile constituents of Parmigiano Reggiano identified were consistent with the compounds intimated in the literature. The obtained results show the applicability of an S3 device combined with SPME-GC-MS and sensory evaluation for a fast and high-sensitivity analysis of VOCs in Parmigiano Reggiano cheese and for the quality control of this class of cheese.
      PubDate: 2016-12-16
      DOI: 10.3390/bios6040060
      Issue No: Vol. 6, No. 4 (2016)
       
  • Biosensors, Vol. 6, Pages 61: Rapid Detection of Bacillus anthracis Spores
           Using Immunomagnetic Separation and Amperometry

    • Authors: David Waller, Brian Hew, Charlie Holdaway, Michael Jen, Gabriel Peckham
      First page: 61
      Abstract: Portable detection and quantitation methods for Bacillus anthracis (anthrax) spores in pure culture or in environmental samples are lacking. Here, an amperometric immunoassay has been developed utilizing immunomagnetic separation to capture the spores and remove potential interferents from test samples followed by amperometric measurement on a field-portable instrument. Antibody-conjugated magnetic beads and antibody-conjugated glucose oxidase were used in a sandwich format for the capture and detection of target spores. Glucose oxidase activity of spore pellets was measured indirectly via amperometry by applying a bias voltage after incubation with glucose, horseradish peroxidase, and the electron mediator 2,2′-azino-bis (3-ethylbenzthiazoline-6-sulphonic acid). Target capture was mediated by polyclonal antisera, whereas monoclonal antibodies were used for signal generation. This strategy maximized sensitivity (500 target spores, 5000 cfu/mL), while also providing a good specificity for Bacillus anthracis spores. Minimal signal deviation occurs in the presence of environmental interferents including soil and modified pH conditions, demonstrating the strengths of immunomagnetic separation. The simultaneous incubation of capture and detection antibodies and rapid substrate development (5 min) result in short sample-to-signal times (less than an hour). With attributes comparable or exceeding that of ELISA and LFDs, amperometry is a low-cost, low-weight, and practical method for detecting anthrax spores in the field.
      PubDate: 2016-12-20
      DOI: 10.3390/bios6040061
      Issue No: Vol. 6, No. 4 (2016)
       
  • Biosensors, Vol. 6, Pages 61: Rapid Detection of Bacillus anthracis Spores
           Using Immunomagnetic Separation and Amperometry

    • Authors: David Waller, Brian Hew, Charlie Holdaway, Michael Jen, Gabriel Peckham
      First page: 61
      Abstract: Portable detection and quantitation methods for Bacillus anthracis (anthrax) spores in pure culture or in environmental samples are lacking. Here, an amperometric immunoassay has been developed utilizing immunomagnetic separation to capture the spores and remove potential interferents from test samples followed by amperometric measurement on a field-portable instrument. Antibody-conjugated magnetic beads and antibody-conjugated glucose oxidase were used in a sandwich format for the capture and detection of target spores. Glucose oxidase activity of spore pellets was measured indirectly via amperometry by applying a bias voltage after incubation with glucose, horseradish peroxidase, and the electron mediator 2,2′-azino-bis (3-ethylbenzthiazoline-6-sulphonic acid). Target capture was mediated by polyclonal antisera, whereas monoclonal antibodies were used for signal generation. This strategy maximized sensitivity (500 target spores, 5000 cfu/mL), while also providing a good specificity for Bacillus anthracis spores. Minimal signal deviation occurs in the presence of environmental interferents including soil and modified pH conditions, demonstrating the strengths of immunomagnetic separation. The simultaneous incubation of capture and detection antibodies and rapid substrate development (5 min) result in short sample-to-signal times (less than an hour). With attributes comparable or exceeding that of ELISA and LFDs, amperometry is a low-cost, low-weight, and practical method for detecting anthrax spores in the field.
      PubDate: 2016-12-20
      DOI: 10.3390/bios6040061
      Issue No: Vol. 6, No. 4 (2016)
       
  • Biosensors, Vol. 6, Pages 28: Aptasensors Based on Whispering Gallery Mode
           Resonators

    • Authors: Gualtiero Nunzi Conti, Simome Berneschi, Silvia Soria
      First page: 28
      Abstract: In this paper, we review the literature on optical evanescent field sensing in resonant cavities where aptamers are used as biochemical receptors. The combined advantages of highly sensitive whispering gallery mode resonator (WGMR)-based transducers, and of the unique properties of aptamers make this approach extremely interesting in the medical field, where there is a particularly high need for devices able to provide real time diagnosis for cancer, infectious diseases, or strokes. However, despite the superior performances of aptamers compared to antibodies and WGMR to other evanescent sensors, there is not much literature combining both types of receptors and transducers. Up to now, the WGMR that have been used are silica microspheres and silicon oxynitride (SiON) ring resonators.
      PubDate: 2016-07-16
      DOI: 10.3390/bios6030028
      Issue No: Vol. 6, No. 3 (2016)
       
  • Biosensors, Vol. 6, Pages 29: Single Molecule Bioelectronics and Their
           Application to Amplification-Free Measurement of DNA Lengths

    • Authors: O. Gül, Kaitlin Pugliese, Yongki Choi, Patrick Sims, Deng Pan, Arith Rajapakse, Gregory Weiss, Philip Collins
      First page: 29
      Abstract: As biosensing devices shrink smaller and smaller, they approach a scale in which single molecule electronic sensing becomes possible. Here, we review the operation of single-enzyme transistors made using single-walled carbon nanotubes. These novel hybrid devices transduce the motions and catalytic activity of a single protein into an electronic signal for real-time monitoring of the protein’s activity. Analysis of these electronic signals reveals new insights into enzyme function and proves the electronic technique to be complementary to other single-molecule methods based on fluorescence. As one example of the nanocircuit technique, we have studied the Klenow Fragment (KF) of DNA polymerase I as it catalytically processes single-stranded DNA templates. The fidelity of DNA polymerases makes them a key component in many DNA sequencing techniques, and here we demonstrate that KF nanocircuits readily resolve DNA polymerization with single-base sensitivity. Consequently, template lengths can be directly counted from electronic recordings of KF’s base-by-base activity. After measuring as few as 20 copies, the template length can be determined with <1 base pair resolution, and different template lengths can be identified and enumerated in solutions containing template mixtures.
      PubDate: 2016-06-24
      DOI: 10.3390/bios6030029
      Issue No: Vol. 6, No. 3 (2016)
       
  • Biosensors, Vol. 6, Pages 30: Improved Manufacturing Performance of Screen
           Printed Carbon Electrodes through Material Formulation

    • Authors: Eifion Jewell, Bruce Philip, Peter Greenwood
      First page: 30
      Abstract: Printed carbon graphite materials are the primary common component in the majority of screen printed sensors. Screen printing allows a scalable manufacturing solution, accelerating the means by which novel sensing materials can make the transition from laboratory material to commercial product. A common bottleneck in any thick film printing process is the controlled drying of the carbon paste material. A study has been undertaken which examines the interaction between material solvent, printed film conductivity and process consistency. The study illustrates that it is possible to reduce the solvent boiling point to significantly increase process productivity while maintaining process consistency. The lower boiling point solvent also has a beneficial effect on the conductivity of the film, reducing the sheet resistance. It is proposed that this is a result of greater film stressing increasing charge percolation through greater inter particle contact. Simulations of material performance and drying illustrate that a multi layered printing provides a more time efficient manufacturing method. The findings have implications for the volume manufacturing of the carbon sensor electrodes but also have implications for other applications where conductive carbon is used, such as electrical circuits and photovoltaic devices.
      PubDate: 2016-06-27
      DOI: 10.3390/bios6030030
      Issue No: Vol. 6, No. 3 (2016)
       
  • Biosensors, Vol. 6, Pages 31: Amperometric Biosensor Based on Zirconium
           Oxide/Polyethylene Glycol/Tyrosinase Composite Film for the Detection of
           Phenolic Compounds

    • Authors: Nor Ahmad, Jaafar Abdullah, Nor Yusof, Ahmad Ab Rashid, Samsulida Abd Rahman, Md. Hasan
      First page: 31
      Abstract: A phenolic biosensor based on a zirconium oxide/polyethylene glycol/tyrosinase composite film for the detection of phenolic compounds has been explored. The formation of the composite film was expected via electrostatic interaction between hexacetyltrimethylammonium bromide (CTAB), polyethylene glycol (PEG), and zirconium oxide nanoparticles casted on screen printed carbon electrode (SPCE). Herein, the electrode was treated by casting hexacetyltrimethylammonium bromide on SPCE to promote a positively charged surface. Later, zirconium oxide was mixed with polyethylene glycol and the mixture was dropped cast onto the positively charged SPCE/CTAB. Tyrosinase was further immobilized onto the modified SPCE. Characterization of the prepared nanocomposite film and the modified SPCE surface was investigated by scanning electron microscopy (SEM), Electrochemical Impedance Spectroscopy (EIS), and Cyclic voltamogram (CV). The developed biosensor exhibits rapid response for less than 10 s. Two linear calibration curves towards phenol in the concentrations ranges of 0.075–10 µM and 10–55 µM with the detection limit of 0.034 µM were obtained. The biosensor shows high sensitivity and good storage stability for at least 30 days.
      PubDate: 2016-06-29
      DOI: 10.3390/bios6030031
      Issue No: Vol. 6, No. 3 (2016)
       
  • Biosensors, Vol. 6, Pages 32: Development of Formaldehyde Biosensor for
           Determination of Formalin in Fish Samples; Malabar Red Snapper (Lutjanus
           malabaricus) and Longtail Tuna (Thunnus tonggol)

    • Authors: Bohari Noor Aini, Shafiquzzaman Siddiquee, Kamaruzaman Ampon
      First page: 32
      Abstract: Electrochemical biosensors are widely recognized in biosensing devices due to the fact that gives a direct, reliable, and reproducible measurement within a short period. During bio-interaction process and the generation of electrons, it produces electrochemical signals which can be measured using an electrochemical detector. A formaldehyde biosensor was successfully developed by depositing an ionic liquid (IL) (e.g., 1-ethyl-3-methylimidazolium trifluoromethanesulfonate ([EMIM][Otf])), gold nanoparticles (AuNPs), and chitosan (CHIT), onto a glassy carbon electrode (GCE). The developed formaldehyde biosensor was analyzed for sensitivity, reproducibility, storage stability, and detection limits. Methylene blue was used as a redox indicator for increasing the electron transfer in the electrochemical cell. The developed biosensor measured the NADH electron from the NAD+ reduction at a potential of 0.4 V. Under optimal conditions, the differential pulse voltammetry (DPV) method detected a wider linear range of formaldehyde concentrations from 0.01 to 10 ppm within 5 s, with a detection limit of 0.1 ppm. The proposed method was successfully detected with the presence of formalin in fish samples, Lutjanus malabaricus and Thunnus Tonggol. The proposed method is a simple, rapid, and highly accurate, compared to the existing technique.
      PubDate: 2016-06-30
      DOI: 10.3390/bios6030032
      Issue No: Vol. 6, No. 3 (2016)
       
  • Biosensors, Vol. 6, Pages 33: Impedimetric Label-Free Immunosensor on
           Disposable Modified Screen-Printed Electrodes for Ochratoxin A

    • Authors: Francesca Malvano, Donatella Albanese, Alessio Crescitelli, Roberto Pilloton, Emanuela Esposito
      First page: 33
      Abstract: An impedimetric label-free immunosensor on disposable screen-printed carbon electrodes (SPCE) for quantitative determination of Ochratoxin A (OTA) has been developed. After modification of the SPCE surface with gold nanoparticles (AuNPs), the anti-OTA was immobilized on the working electrode through a cysteamine layer. After each coating step, the modified surfaces were characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The capacitance was chosen as the best parameter that describes the reproducible change in electrical properties of the electrode surface at different OTA concentrations and it was used to investigate the analytical parameters of the developed immunosensor. Under optimized conditions, the immunosensor showed a linear relationship between 0.3 and 20 ng/mL with a low detection limit of 0.25 ng/mL, making it suitable to control OTA content in many common food products. Lastly, the immunosensor was used to measure OTA in red wine samples and the results were compared with those registered with a competitive ELISA kit. The immunosensor was sensitive to OTA lower than 2 μg/kg, which represents the lower acceptable limit of OTA established by European legislation for common food products.
      PubDate: 2016-06-30
      DOI: 10.3390/bios6030033
      Issue No: Vol. 6, No. 3 (2016)
       
  • Biosensors, Vol. 6, Pages 34: Enhanced Biosensor Platforms for Detecting
           the Atherosclerotic Biomarker VCAM1 Based on Bioconjugation with Uniformly
           Oriented VCAM1-Targeting Nanobodies

    • Authors: Duy Ta, Wanda Guedens, Tom Vranken, Katrijn Vanschoenbeek, Erik Steen Redeker, Luc Michiels, Peter Adriaensens
      First page: 34
      Abstract: Surface bioconjugation of biomolecules has gained enormous attention for developing advanced biomaterials including biosensors. While conventional immobilization (by physisorption or covalent couplings using the functional groups of the endogenous amino acids) usually results in surfaces with low activity, reproducibility and reusability, the application of methods that allow for a covalent and uniformly oriented coupling can circumvent these limitations. In this study, the nanobody targeting Vascular Cell Adhesion Molecule-1 (NbVCAM1), an atherosclerotic biomarker, is engineered with a C-terminal alkyne function via Expressed Protein Ligation (EPL). Conjugation of this nanobody to azidified silicon wafers and Biacore™ C1 sensor chips is achieved via Copper(I)-catalyzed azide-alkyne cycloaddition (CuAAC) “click” chemistry to detect VCAM1 binding via ellipsometry and surface plasmon resonance (SPR), respectively. The resulting surfaces, covered with uniformly oriented nanobodies, clearly show an increased antigen binding affinity, sensitivity, detection limit, quantitation limit and reusability as compared to surfaces prepared by random conjugation. These findings demonstrate the added value of a combined EPL and CuAAC approach as it results in strong control over the surface orientation of the nanobodies and an improved detecting power of their targets—a must for the development of advanced miniaturized, multi-biomarker biosensor platforms.
      PubDate: 2016-07-05
      DOI: 10.3390/bios6030034
      Issue No: Vol. 6, No. 3 (2016)
       
  • Biosensors, Vol. 6, Pages 35: MIPs and Aptamers for Recognition of
           Proteins in Biomimetic Sensing

    • Authors: Marcus Menger, Aysu Yarman, Júlia Erdőssy, Huseyin Yildiz, Róbert Gyurcsányi, Frieder Scheller
      First page: 35
      Abstract: Biomimetic binders and catalysts have been generated in order to substitute the biological pendants in separation techniques and bioanalysis. The two major approaches use either “evolution in the test tube” of nucleotides for the preparation of aptamers or total chemical synthesis for molecularly imprinted polymers (MIPs). The reproducible production of aptamers is a clear advantage, whilst the preparation of MIPs typically leads to a population of polymers with different binding sites. The realization of binding sites in the total bulk of the MIPs results in a higher binding capacity, however, on the expense of the accessibility and exchange rate. Furthermore, the readout of the bound analyte is easier for aptamers since the integration of signal generating labels is well established. On the other hand, the overall negative charge of the nucleotides makes aptamers prone to non-specific adsorption of positively charged constituents of the sample and the “biological” degradation of non-modified aptamers and ionic strength-dependent changes of conformation may be challenging in some application.
      PubDate: 2016-07-18
      DOI: 10.3390/bios6030035
      Issue No: Vol. 6, No. 3 (2016)
       
  • Biosensors, Vol. 6, Pages 36: Flexible Molybdenum Electrodes towards
           Designing Affinity Based Protein Biosensors

    • Authors: Vikramshankar Kamakoti, Anjan Panneer Selvam, Nandhinee Radha Shanmugam, Sriram Muthukumar, Shalini Prasad
      First page: 36
      Abstract: Molybdenum electrode based flexible biosensor on porous polyamide substrates has been fabricated and tested for its functionality as a protein affinity based biosensor. The biosensor performance was evaluated using a key cardiac biomarker; cardiac Troponin-I (cTnI). Molybdenum is a transition metal and demonstrates electrochemical behavior upon interaction with an electrolyte. We have leveraged this property of molybdenum for designing an affinity based biosensor using electrochemical impedance spectroscopy. We have evaluated the feasibility of detection of cTnI in phosphate-buffered saline (PBS) and human serum (HS) by measuring impedance changes over a frequency window from 100 mHz to 1 MHz. Increasing changes to the measured impedance was correlated to the increased dose of cTnI molecules binding to the cTnI antibody functionalized molybdenum surface. We achieved cTnI detection limit of 10 pg/mL in PBS and 1 ng/mL in HS medium. The use of flexible substrates for designing the biosensor demonstrates promise for integration with a large-scale batch manufacturing process.
      PubDate: 2016-07-18
      DOI: 10.3390/bios6030036
      Issue No: Vol. 6, No. 3 (2016)
       
  • Biosensors, Vol. 6, Pages 37: PCR-Independent Detection of Bacterial
           Species-Specific 16S rRNA at 10 fM by a Pore-Blockage Sensor

    • Authors: Leyla Esfandiari, Siqing Wang, Siqi Wang, Anisha Banda, Michael Lorenzini, Gayane Kocharyan, Harold Monbouquette, Jacob Schmidt
      First page: 37
      Abstract: A PCR-free, optics-free device is used for the detection of Escherichia coli (E. coli) 16S rRNA at 10 fM, which corresponds to ~100–1000 colony forming units/mL (CFU/mL) depending on cellular rRNA levels. The development of a rapid, sensitive, and cost-effective nucleic acid detection platform is sought for the detection of pathogenic microbes in food, water and body fluids. Since 16S rRNA sequences are species specific and are present at high copy number in viable cells, these nucleic acids offer an attractive target for microbial pathogen detection schemes. Here, target 16S rRNA of E. coli at 10 fM concentration was detected against a total RNA background using a conceptually simple approach based on electromechanical signal transduction, whereby a step change reduction in ionic current through a pore indicates blockage by an electrophoretically mobilized bead-peptide nucleic acid probe conjugate hybridized to target nucleic acid. We investigated the concentration detection limit for bacterial species-specific 16S rRNA at 1 pM to 1 fM and found a limit of detection of 10 fM for our device, which is consistent with our previous finding with single-stranded DNA of similar length. In addition, no false positive responses were obtained with control RNA and no false negatives with target 16S rRNA present down to the limit of detection (LOD) of 10 fM. Thus, this detection scheme shows promise for integration into portable, low-cost systems for rapid detection of pathogenic microbes in food, water and body fluids.
      PubDate: 2016-07-22
      DOI: 10.3390/bios6030037
      Issue No: Vol. 6, No. 3 (2016)
       
  • Biosensors, Vol. 6, Pages 38: Exploiting Chemistry to Improve Performance
           of Screen-Printed, Bismuth Film Electrodes (SP-BiFE)

    • Authors: Carlo Dossi, Damiano Monticelli, Andrea Pozzi, Sandro Recchia
      First page: 38
      Abstract: Mercury substitution is a big issue in electroanalysis, and the search for a suitable, and less toxic, replacement is still under development. Of all the proposed alternatives, bismuth films appear to be the most viable solution, although they are still suffering some drawbacks, particularly the influence of deposition conditions and linearity at low concentrations. In this paper, the most promising strategies for bismuth film deposition on screen-printed electrodes (surface modifications, polymeric film deposition, insoluble salt precursors) will be evaluated for trace metal analysis. Particular attention will be devoted to bismuth chemistry, aiming to rationalize their electroanalytic performance.
      PubDate: 2016-07-22
      DOI: 10.3390/bios6030038
      Issue No: Vol. 6, No. 3 (2016)
       
  • Biosensors, Vol. 6, Pages 39: Electrochemical, Electrochemiluminescence,
           and Photoelectrochemical Aptamer-Based Nanostructured Sensors for
           Biomarker Analysis

    • Authors: Andrea Ravalli, Diego Voccia, Ilaria Palchetti, Giovanna Marrazza
      First page: 39
      Abstract: Aptamer-based sensors have been intensively investigated as potential analytical tools in clinical analysis providing the desired portability, fast response, sensitivity, and specificity, in addition to lower cost and simplicity versus conventional methods. The aim of this review, without pretending to be exhaustive, is to give the readers an overview of recent important achievements about electrochemical, electrochemiluminescence, and photoelectrochemical aptasensors for the protein biomarker determination, mainly cancer related biomarkers, by selected recent publications. Special emphasis is placed on nanostructured-based aptasensors, which show a substantial improvement of the analytical performances.
      PubDate: 2016-08-02
      DOI: 10.3390/bios6030039
      Issue No: Vol. 6, No. 3 (2016)
       
  • Biosensors, Vol. 6, Pages 40: Monitoring Intact Viruses Using Aptamers

    • Authors: Penmetcha Kumar
      First page: 40
      Abstract: Viral diagnosis and surveillance are necessary steps in containing the spread of viral diseases, and they help in the deployment of appropriate therapeutic interventions. In the past, the commonly employed viral detection methods were either cell-culture or molecule-level assays. Most of these assays are laborious and expensive, require special facilities, and provide a slow diagnosis. To circumvent these limitations, biosensor-based approaches are becoming attractive, especially after the successful commercialization of glucose and other biosensors. In the present article, I have reviewed the current progress using the biosensor approach for detecting intact viruses. At the time of writing this review, three types of bioreceptor surfaces (antibody-, glycan-, and aptamer-based) have been explored on different sensing platforms for detecting intact viruses. Among these bioreceptors, aptamer-based sensors have been increasingly explored for detecting intact viruses using surface plasmon resonance (SPR) and other platforms. Special emphasis is placed on the aptamer-based SPR platform in the present review.
      PubDate: 2016-08-04
      DOI: 10.3390/bios6030040
      Issue No: Vol. 6, No. 3 (2016)
       
  • Biosensors, Vol. 6, Pages 41: Microfluidic Devices for Forensic DNA
           Analysis: A Review

    • Authors: Brigitte Bruijns, Arian van Asten, Roald Tiggelaar, Han Gardeniers
      First page: 41
      Abstract: Microfluidic devices may offer various advantages for forensic DNA analysis, such as reduced risk of contamination, shorter analysis time and direct application at the crime scene. Microfluidic chip technology has already proven to be functional and effective within medical applications, such as for point-of-care use. In the forensic field, one may expect microfluidic technology to become particularly relevant for the analysis of biological traces containing human DNA. This would require a number of consecutive steps, including sample work up, DNA amplification and detection, as well as secure storage of the sample. This article provides an extensive overview of microfluidic devices for cell lysis, DNA extraction and purification, DNA amplification and detection and analysis techniques for DNA. Topics to be discussed are polymerase chain reaction (PCR) on-chip, digital PCR (dPCR), isothermal amplification on-chip, chip materials, integrated devices and commercially available techniques. A critical overview of the opportunities and challenges of the use of chips is discussed, and developments made in forensic DNA analysis over the past 10–20 years with microfluidic systems are described. Areas in which further research is needed are indicated in a future outlook.
      PubDate: 2016-08-05
      DOI: 10.3390/bios6030041
      Issue No: Vol. 6, No. 3 (2016)
       
  • Biosensors, Vol. 6, Pages 42: Nanopore-CMOS Interfaces for DNA Sequencing

    • Authors: Sebastian Magierowski, Yiyun Huang, Chengjie Wang, Ebrahim Ghafar-Zadeh
      First page: 42
      Abstract: DNA sequencers based on nanopore sensors present an opportunity for a significant break from the template-based incumbents of the last forty years. Key advantages ushered by nanopore technology include a simplified chemistry and the ability to interface to CMOS technology. The latter opportunity offers substantial promise for improvement in sequencing speed, size and cost. This paper reviews existing and emerging means of interfacing nanopores to CMOS technology with an emphasis on massively-arrayed structures. It presents this in the context of incumbent DNA sequencing techniques, reviews and quantifies nanopore characteristics and models and presents CMOS circuit methods for the amplification of low-current nanopore signals in such interfaces.
      PubDate: 2016-08-06
      DOI: 10.3390/bios6030042
      Issue No: Vol. 6, No. 3 (2016)
       
  • Biosensors, Vol. 6, Pages 43: Effects of Surface Epitope Coverage on the
           Sensitivity of Displacement Assays that Employ Modified Nanoparticles:
           Using Bisphenol A as a Model Analyte

    • Authors: Yang Lu, Joshua Peterson, Erwann Luais, John Gooding, Nanju Lee
      First page: 43
      Abstract: With the ever-increasing use of nanoparticles in immunosensors, a fundamental study on the effect of epitope density is presented herein, with a small molecule epitope, on the performance of the displacement assay format in an enzyme-linked immunosorbent assay (ELISA). Thiolated bisphenol A (BPA) functionalized gold nanoparticles (cysBPAv-AuNPs) and specific anti-BPA antibodies are employed for this purpose. It is shown that the displacement of cysBPAv-AuNPs bound to the immobilized antibodies was influenced by both the avidity of bound cysBPAv-AuNPs and the concentration of free BPA to displace it. The importance of surface epitope density was that it changed the number of epitopes in close proximity to the antibody-binding site. This then influenced the avidity of cysBPAv-AuNPs bound to the immobilized antibody. Furthermore, the molar epitope concentration in an assay appears to affect the degree of antibody binding site saturation. Controlling surface epitope density of the functionalized nanoparticles and molar epitope concentration in an assay leads to a decrease of the concentration of free BPA required to displace the bound cysBPAv-AuNP, and hence better assay performance with regards to the D50 value and dynamic range in the displacement assay.
      PubDate: 2016-08-08
      DOI: 10.3390/bios6030043
      Issue No: Vol. 6, No. 3 (2016)
       
  • Biosensors, Vol. 6, Pages 44: A Cytochrome P450 3A4 Biosensor Based on
           Generation 4.0 PAMAM Dendrimers for the Detection of Caffeine

    • Authors: Michael Müller, Neha Agarwal, Jungtae Kim
      First page: 44
      Abstract: Cytochromes P450 (CYP, P450) are a large family of heme-active-site proteins involved in many catalytic processes, including steroidogenesis. In humans, four primary enzymes are involved in the metabolism of almost all xenobiotics. Among these enzymes, CYP3A4 is responsible for the inactivation of the majority of used drugs which makes this enzyme an interesting target for many fields of research, especially pharmaceutical research. Since the late 1970s, attempts have been made to construct and develop electrochemical sensors for the determination of substrates. This paper is concerned with the establishment of such a CYP3A4-containing biosensor. The sensor was constructed by adsorption of alternating layers of sub-nanometer gold particle-modified PAMAM (poly-amido-amine) dendrimers of generation 4.0, along with the enzyme by a layer-by-layer assembly technique. Atomic force microscopy (AFM), quartz crystal microbalance (QCM), and Fourier-transformed infrared spectroscopy (FTIR) were employed to elucidate the sensor assembly. Additionally, the biosensor was tested by cyclic voltammetry using caffeine as a substrate.
      PubDate: 2016-08-18
      DOI: 10.3390/bios6030044
      Issue No: Vol. 6, No. 3 (2016)
       
  • Biosensors, Vol. 6, Pages 45: Pencil It in: Exploring the Feasibility of
           Hand-Drawn Pencil Electrochemical Sensors and Their Direct Comparison to
           Screen-Printed Electrodes

    • Authors: Elena Bernalte, Christopher Foster, Dale Brownson, Morgane Mosna, Graham Smith, Craig Banks
      First page: 45
      Abstract: We explore the fabrication, physicochemical characterisation (SEM, Raman, EDX and XPS) and electrochemical application of hand-drawn pencil electrodes (PDEs) upon an ultra-flexible polyester substrate; investigating the number of draws (used for their fabrication), the pencil grade utilised (HB to 9B) and the electrochemical properties of an array of batches (i.e, pencil boxes). Electrochemical characterisation of the PDEs, using different batches of HB grade pencils, is undertaken using several inner- and outer-sphere redox probes and is critically compared to screen-printed electrodes (SPEs). Proof-of-concept is demonstrated for the electrochemical sensing of dopamine and acetaminophen using PDEs, which are found to exhibit competitive limits of detection (3σ) upon comparison to SPEs. Nonetheless, it is important to note that a clear lack of reproducibility was demonstrated when utilising these PDEs fabricated using the HB pencils from different batches. We also explore the suitability and feasibility of a pencil-drawn reference electrode compared to screen-printed alternatives, to see if one can draw the entire sensing platform. This article reports a critical assessment of these PDEs against that of its screen-printed competitors, questioning the overall feasibility of PDEs’ implementation as a sensing platform.
      PubDate: 2016-08-29
      DOI: 10.3390/bios6030045
      Issue No: Vol. 6, No. 3 (2016)
       
  • Biosensors, Vol. 6, Pages 46: Electrochemical Sensors Based on
           Screen-Printed Electrodes: The Use of Phthalocyanine Derivatives for
           Application in VFA Detection

    • Authors: Amadou Ndiaye, Sébastien Delile, Jérôme Brunet, Christelle Varenne, Alain Pauly
      First page: 46
      Abstract: Here, we report on the use of electrochemical methods for the detection of volatiles fatty acids (VFAs), namely acetic acid. We used tetra-tert-butyl phthalocyanine (PcH2-tBu) as the sensing material and investigated its electroanalytical properties by means of cyclic voltammetry (CV) and square wave voltammetry (SWV). To realize the electrochemical sensing system, the PcH2-tBu has been dropcast-deposited on carbon (C) orgold (Au)screen-printed electrodes (SPEs) and characterized by cyclic voltammetry and scanning electron microscopy (SEM). The SEM analysis reveals that the PcH2-tBu forms mainly aggregates on the SPEs. The modified electrodes are used for the detection of acetic acid and present a linear current increase when the acetic acid concentration increases. The Cmodified electrode presents a limit of detection (LOD) of 25.77 mM in the range of 100 mM–400 mM, while the Aumodified electrode presents an LOD averaging 40.89 mM in the range of 50 mM–300 mM. When the experiment is realized in a buffered condition, theCmodified electrode presents a lower LOD, which averagesthe 7.76 mM. A pronounced signal decay attributed to an electrode alteration is observed in the case of the gold electrode. This electrode alteration severely affects the coating stability. This alteration is less perceptible in the case of the carbon electrode.
      PubDate: 2016-09-01
      DOI: 10.3390/bios6030046
      Issue No: Vol. 6, No. 3 (2016)
       
  • Biosensors, Vol. 6, Pages 47: Potential of Surface Enhanced Raman
           Spectroscopy (SERS) in Therapeutic Drug Monitoring (TDM). A Critical
           Review

    • Authors: Aleksandra Jaworska, Stefano Fornasaro, Valter Sergo, Alois Bonifacio
      First page: 47
      Abstract: Surface-Enhanced Raman Spectroscopy (SERS) is a label-free technique that enables quick monitoring of substances at low concentrations in biological matrices. These advantages make it an attractive tool for the development of point-of-care tests suitable for Therapeutic Drug Monitoring (TDM) of drugs with a narrow therapeutic window, such as chemotherapeutic drugs, immunosuppressants, and various anticonvulsants. In this article, the current applications of SERS in the field of TDM for cancer therapy are discussed in detail and illustrated according to the different strategies and substrates. In particular, future perspectives are provided and special concerns regarding the standardization of self-assembly methods and nanofabrication procedures, quality assurance, and technology readiness are critically evaluated.
      PubDate: 2016-09-19
      DOI: 10.3390/bios6030047
      Issue No: Vol. 6, No. 3 (2016)
       
  • Biosensors, Vol. 6, Pages 48: Lactate Sensors on Flexible Substrates

    • Authors: Xuesong Yang, Timothy Fu, Pavan Kota, Maggie Tjia, Cuong Nguyen, Jung-Chih Chiao
      First page: 48
      Abstract: Lactate detection by an in situ sensor is of great need in clinical medicine, food processing, and athletic performance monitoring. In this paper, a flexible, easy to fabricate, and low-cost biosensor base on lactate oxidase is presented. The fabrication processes, including metal deposition, sol-gel IrOx deposition, and drop-dry enzyme loading method, are described in detail. The loaded enzyme was examined by scanning electron microscopy. Cyclic voltammetry was used to characterize the sensors. Durability, sensibility, and selectivity of the biosensors were examined. The comparison for different electrode sizes and different sensing film materials was conducted. The sensor could last for four weeks with an average surface area normalized sensitivity of 950 nA/(cm2 mM) and 9250 nA/(cm2 mM) for Au-based electrodes, and IrOx-modified electrodes respectively, both with an electrode size of 100 × 50 μm. The self-referencing method to record noises simultaneously with the working electrode greatly improved sensor sensitivity and selectivity. The sensor showed little response to interference chemicals, such as glutamate and dopamine.
      PubDate: 2016-09-21
      DOI: 10.3390/bios6030048
      Issue No: Vol. 6, No. 3 (2016)
       
  • Biosensors, Vol. 6, Pages 11: Measurement of Rapid Amiloride-Dependent pH
           Changes at the Cell Surface Using a Proton-Sensitive Field-Effect
           Transistor

    • Authors: Daniel Schaffhauser, Michael Fine, Miyuki Tabata, Tatsuro Goda, Yuji Miyahara
      First page: 11
      Abstract: We present a novel method for the rapid measurement of pH fluxes at close proximity to the surface of the plasma membrane in mammalian cells using an ion-sensitive field-effect transistor (ISFET). In conjuction with an efficient continuous superfusion system, the ISFET sensor was capable of recording rapid changes in pH at the cells’ surface induced by intervals of ammonia loading and unloading, even when using highly buffered solutions. Furthermore, the system was able to isolate physiologically relevant signals by not only detecting the transients caused by ammonia loading and unloading, but display steady-state signals as would be expected by a proton transport-mediated influence on the extracellular proton-gradient. Proof of concept was demonstrated through the use of 5-(N-ethyl-N-isopropyl)amiloride (EIPA), a small molecule inhibitor of sodium/hydrogen exchangers (NHE). As the primary transporter responsible for proton balance during cellular regulation of pH, non-electrogenic NHE transport is notoriously difficult to detect with traditional methods. Using the NHE positive cell lines, Chinese hamster ovary (CHO) cells and NHE3-reconstituted mouse skin fibroblasts (MSF), the sensor exhibited a significant response to EIPA inhibition, whereas NHE-deficient MSF cells were unaffected by application of the inhibitor.
      PubDate: 2016-03-30
      DOI: 10.3390/bios6020011
      Issue No: Vol. 6, No. 2 (2016)
       
  • Biosensors, Vol. 6, Pages 12: Epigenome: A Biomarker or Screening Tool to
           Evaluate Health Impact of Cumulative Exposure to Chemical and Non-Chemical
           Stressors

    • Authors: Kenneth Olden, Yu-Sheng Lin, David Bussard
      First page: 12
      Abstract: Current risk assessment practices and toxicity information are hard to utilize for assessing the health impact of combined or cumulative exposure to multiple chemical and non-chemical stressors encountered in the “real world” environment. Non-chemical stressors such as heat, radiation, noise, humidity, bacterial and viral agents, and social factors, like stress related to violence and socioeconomic position generally cannot be currently incorporated into the risk assessment paradigm. The Science and Decisions report released by the National Research Council (NRC) in 2009 emphasized the need to characterize the effects of multiple stressors, both chemical and non-chemical exposures. One impediment to developing information relating such non-chemical stressors to health effects and incorporating them into cumulative assessment has been the lack of analytical tools to easily and quantitatively monitor the cumulative exposure to combined effects of stressors over the life course.
      PubDate: 2016-04-01
      DOI: 10.3390/bios6020012
      Issue No: Vol. 6, No. 2 (2016)
       
  • Biosensors, Vol. 6, Pages 13: Infrared Spectroscopy of Bilberry Extract
           Water-in-Oil Emulsions: Sensing the Water-Oil Interface

    • Authors: Johannes Kiefer, Kerstin Frank, Florian Zehentbauer, Heike Schuchmann
      First page: 13
      Abstract: Water-in-oil (w/o) emulsions are of great interest in many areas of the life sciences, including food technology, bioprocess engineering, and pharmaceuticals. Such emulsions are complex multi-component systems and the molecular mechanisms which lead to a stable emulsion are yet to be fully understood. In this work, attenuated total reflection (ATR) infrared (IR) spectroscopy is applied to a series of w/o emulsions of an aqueous anthocyanin-rich bilberry extract dispersed in a medium chain triglyceride (MCT) oil phase. The content of the emulsifier polyglycerin-polyricinoleat (PGPR) has been varied systematically in order to investigate whether or not its concentration has an impact on the molecular stabilization mechanisms. The molecular stabilization is accessed by a careful analysis of the IR spectrum, where changes in the vibrational frequencies and signal strengths indicate alterations of the molecular environment at the water/oil interface. The results suggest that adding emulsifier in excess of 1% by weight does not lead to an enhanced stabilization of the emulsion.
      PubDate: 2016-04-14
      DOI: 10.3390/bios6020013
      Issue No: Vol. 6, No. 2 (2016)
       
  • Biosensors, Vol. 6, Pages 14: Droplet-based Biosensing for Lab-on-a-Chip,
           Open Microfluidics Platforms

    • Authors: Piyush Dak, Aida Ebrahimi, Vikhram Swaminathan, Carlos Duarte-Guevara, Rashid Bashir, Muhammad Alam
      First page: 14
      Abstract: Low cost, portable sensors can transform health care by bringing easily available diagnostic devices to low and middle income population, particularly in developing countries. Sample preparation, analyte handling and labeling are primary cost concerns for traditional lab-based diagnostic systems. Lab-on-a-chip (LoC) platforms based on droplet-based microfluidics promise to integrate and automate these complex and expensive laboratory procedures onto a single chip; the cost will be further reduced if label-free biosensors could be integrated onto the LoC platforms. Here, we review some recent developments of label-free, droplet-based biosensors, compatible with “open” digital microfluidic systems. These low-cost droplet-based biosensors overcome some of the fundamental limitations of the classical sensors, enabling timely diagnosis. We identify the key challenges that must be addressed to make these sensors commercially viable and summarize a number of promising research directions.
      PubDate: 2016-04-14
      DOI: 10.3390/bios6020014
      Issue No: Vol. 6, No. 2 (2016)
       
  • Biosensors, Vol. 6, Pages 15: AC and Phase Sensing of Nanowires for
           Biosensing

    • Authors: Marco Crescentini, Michele Rossi, Peter Ashburn, Marta Lombardini, Enrico Sangiorgi, Hywel Morgan, Marco Tartagni
      First page: 15
      Abstract: Silicon nanowires are label-free sensors that allow real-time measurements. They are economical and pave the road for point-of-care applications but require complex readout and skilled personnel. We propose a new model and technique for sensing nanowire sensors using alternating currents (AC) to capture both magnitude and phase information from the sensor. This approach combines the advantages of complex impedance spectroscopy with the noise reduction performances of lock-in techniques. Experimental results show how modifications of the sensors with different surface chemistries lead to the same direct-current (DC) response but can be discerned using the AC approach.
      PubDate: 2016-04-19
      DOI: 10.3390/bios6020015
      Issue No: Vol. 6, No. 2 (2016)
       
  • Biosensors, Vol. 6, Pages 16: Harnessing Aptamers to Overcome Challenges
           in Gluten Detection

    • Authors: Rebeca Miranda-Castro, Noemí de-los-Santos-Álvarez, Arturo Miranda-Ordieres, María Lobo-Castañón
      First page: 16
      Abstract: Celiac disease is a lifelong autoimmune disorder triggered by foods containing gluten, the storage protein in wheat, rye, and barley. The rapidly escalating number of patients diagnosed with this disease poses a great challenge to both food industry and authorities to guarantee food safety for all. Therefore, intensive efforts are being made to establish minimal disease-eliciting doses of gluten and consequently to improve gluten-free labeling. These efforts depend to a high degree on the availability of methods capable of detecting the protein in food samples at levels as low as possible. Current analytical approaches rely on the use of antibodies as selective recognition elements. With limited sensitivity, these methods exhibit some deficiencies that compromise the accuracy of the obtained results. Aptamers provide an ideal alternative for designing biosensors for fast and selective measurement of gluten in foods. This article highlights the challenges in gluten detection, the current status of the use of aptamers for solving this problem, and what remains to be done to move these systems into commercial applications.
      PubDate: 2016-04-20
      DOI: 10.3390/bios6020016
      Issue No: Vol. 6, No. 2 (2016)
       
  • Biosensors, Vol. 6, Pages 17: Electronic Biosensing with Functionalized
           rGO FETs

    • Authors: Ciril Reiner-Rozman, Caroline Kotlowski, Wolfgang Knoll
      First page: 17
      Abstract: In the following we give a short summary of examples for biosensor concepts in areas in which reduced graphene oxide-based electronic devices can be developed into new classes of biosensors, which are highly sensitive, label-free, disposable and cheap, with electronic signals that are easy to analyze and interpret, suitable for multiplexed operation and for remote control, compatible with NFC technology, etc., and in many cases a clear and promising alternative to optical sensors. The presented areas concern sensing challenges in medical diagnostics with an example for detecting general antibody-antigen interactions, for the monitoring of toxins and pathogens in food and feed stuff, exemplified by the detection of aflatoxins, and the area of smell sensors, which are certainly the most exciting development as there are very few existing examples in which the typically small and hydrophobic odorant molecules can be detected by other means. The example given here concerns the recording of a honey flavor (and a cancer marker for neuroblastoma), homovanillic acid, by the odorant binding protein OBP 14 from the honey bee, immobilized on the reduced graphene oxide gate of an FET sensor.
      PubDate: 2016-04-22
      DOI: 10.3390/bios6020017
      Issue No: Vol. 6, No. 2 (2016)
       
  • Biosensors, Vol. 6, Pages 18: Current-Induced Transistor Sensorics with
           Electrogenic Cells

    • Authors: Peter Fromherz
      First page: 18
      Abstract: The concepts of transistor recording of electroactive cells are considered, when the response is determined by a current-induced voltage in the electrolyte due to cellular activity. The relationship to traditional transistor recording, with an interface-induced response due to interactions with the open gate oxide, is addressed. For the geometry of a cell-substrate junction, the theory of a planar core-coat conductor is described with a one-compartment approximation. The fast electrical relaxation of the junction and the slow change of ion concentrations are pointed out. On that basis, various recording situations are considered and documented by experiments. For voltage-gated ion channels under voltage clamp, the effects of a changing extracellular ion concentration and the enhancement/depletion of ion conductances in the adherent membrane are addressed. Inhomogeneous ion conductances are crucial for transistor recording of neuronal action potentials. For a propagating action potential, the effects of an axon-substrate junction and the surrounding volume conductor are distinguished. Finally, a receptor-transistor-sensor is described, where the inhomogeneity of a ligand–activated ion conductance is achieved by diffusion of the agonist and inactivation of the conductance. Problems with regard to a development of reliable biosensors are mentioned.
      PubDate: 2016-04-25
      DOI: 10.3390/bios6020018
      Issue No: Vol. 6, No. 2 (2016)
       
  • Biosensors, Vol. 6, Pages 19: Semi-Quantitative Method for Streptococci
           Magnetic Detection in Raw Milk

    • Authors: Carla Duarte, Tiago Costa, Carla Carneiro, Rita Soares, Andrei Jitariu, Susana Cardoso, Moisés Piedade, Ricardo Bexiga, Paulo Freitas
      First page: 19
      Abstract: Bovine mastitis is the most costly disease for dairy farmers and the most frequent reason for the use of antibiotics in dairy cattle; thus, control measures to detect and prevent mastitis are crucial for dairy farm sustainability. The aim of this study was to develop and validate a sensitive method to magnetically detect Streptococcus agalactiae (a Group B streptococci) and Streptococcus uberis in raw milk samples. Mastitic milk samples were collected aseptically from 44 cows with subclinical mastitis, from 11 Portuguese dairy farms. Forty-six quarter milk samples were selected based on bacterial identification by conventional microbiology. All samples were submitted to PCR analysis. In parallel, these milk samples were mixed with a solution combining specific antibodies and magnetic nanoparticles, to be analyzed using a lab-on-a-chip magnetoresistive cytometer, with microfluidic sample handling. This paper describes a point of care methodology used for detection of bacteria, including analysis of false positive/negative results. This immunological recognition was able to detect bacterial presence in samples spiked above 100 cfu/mL, independently of antibody and targeted bacteria used in this work. Using PCR as a reference, this method correctly identified 73% of positive samples for streptococci species with an anti-S. agalactiae antibody, and 41% of positive samples for an anti-GB streptococci antibody.
      PubDate: 2016-04-27
      DOI: 10.3390/bios6020019
      Issue No: Vol. 6, No. 2 (2016)
       
  • Biosensors, Vol. 6, Pages 20: Real-Time Detection of Staphylococcus Aureus
           Using Whispering Gallery Mode Optical Microdisks

    • Authors: Hala Ghali, Hicham Chibli, Jay Nadeau, Pablo Bianucci, Yves-Alain Peter
      First page: 20
      Abstract: Whispering Gallery Mode (WGM) microresonators have recently been studied as a means to achieve real-time label-free detection of biological targets such as virus particles, specific DNA sequences, or proteins. Due to their high quality (Q) factors, WGM resonators can be highly sensitive. A biosensor also needs to be selective, requiring proper functionalization of its surface with the appropriate ligand that will attach the biomolecule of interest. In this paper, WGM microdisks are used as biosensors for detection of Staphylococcus aureus. The microdisks are functionalized with LysK, a phage protein specific for staphylococci at the genus level. A binding event on the surface shifts the resonance peak of the microdisk resonator towards longer wavelengths. This reactive shift can be used to estimate the surface density of bacteria that bind to the surface of the resonator. The limit of detection of a microdisk with a Q-factor around 104 is on the order of 5 pg/mL, corresponding to 20 cells. No binding of Escherichia coli to the resonators is seen, supporting the specificity of the functionalization scheme.
      PubDate: 2016-05-03
      DOI: 10.3390/bios6020020
      Issue No: Vol. 6, No. 2 (2016)
       
  • Biosensors, Vol. 6, Pages 21: Implementing Silicon Nanoribbon Field-Effect
           Transistors as Arrays for Multiple Ion Detection

    • Authors: Ralph Stoop, Mathias Wipf, Steffen Müller, Kristine Bedner, Iain Wright, Colin Martin, Edwin Constable, Axel Fanget, Christian Schönenberger, Michel Calame
      First page: 21
      Abstract: Ionic gradients play a crucial role in the physiology of the human body, ranging from metabolism in cells to muscle contractions or brain activities. To monitor these ions, inexpensive, label-free chemical sensing devices are needed. Field-effect transistors (FETs) based on silicon (Si) nanowires or nanoribbons (NRs) have a great potential as future biochemical sensors as they allow for the integration in microscopic devices at low production costs. Integrating NRs in dense arrays on a single chip expands the field of applications to implantable electrodes or multifunctional chemical sensing platforms. Ideally, such a platform is capable of detecting numerous species in a complex analyte. Here, we demonstrate the basis for simultaneous sodium and fluoride ion detection with a single sensor chip consisting of arrays of gold-coated SiNR FETs. A microfluidic system with individual channels allows modifying the NR surfaces with self-assembled monolayers of two types of ion receptors sensitive to sodium and fluoride ions. The functionalization procedure results in a differential setup having active fluoride- and sodium-sensitive NRs together with bare gold control NRs on the same chip. Comparing functionalized NRs with control NRs allows the compensation of non-specific contributions from changes in the background electrolyte concentration and reveals the response to the targeted species.
      PubDate: 2016-05-06
      DOI: 10.3390/bios6020021
      Issue No: Vol. 6, No. 2 (2016)
       
  • Biosensors, Vol. 6, Pages 22: A Flow SPR Immunosensor Based on a Sandwich
           Direct Method

    • Authors: Mauro Tomassetti, Giorgia Conta, Luigi Campanella, Gabriele Favero, Gabriella Sanzò, Franco Mazzei, Riccarda Antiochia
      First page: 22
      Abstract: In this study, we report the development of an SPR (Surface Plasmon Resonance) immunosensor for the detection of ampicillin, operating under flow conditions. SPR sensors based on both direct (with the immobilization of the antibody) and competitive (with the immobilization of the antigen) methods did not allow the detection of ampicillin. Therefore, a sandwich-based sensor was developed which showed a good linear response towards ampicillin between 10−3 and 10−1 M, a measurement time of ≤20 min and a high selectivity both towards β-lactam antibiotics and antibiotics of different classes.
      PubDate: 2016-05-13
      DOI: 10.3390/bios6020022
      Issue No: Vol. 6, No. 2 (2016)
       
  • Biosensors, Vol. 6, Pages 23: Broadband 120 MHz Impedance Quartz Crystal
           Microbalance (QCM) with Calibrated Resistance and Quantitative Dissipation
           for Biosensing Measurements at Higher Harmonic Frequencies

    • Authors: Manuel Kasper, Lukas Traxler, Jasmina Salopek, Herwig Grabmayr, Andreas Ebner, Ferry Kienberger
      First page: 23
      Abstract: We developed an impedance quartz crystal microbalance (QCM) approach with the ability to simultaneously record mass changes and calibrated energy dissipation with high sensitivity using an impedance analyzer. This impedance QCM measures frequency shifts and resistance changes of sensing quartz crystals very stable, accurately, and calibrated, thus yielding quantitative information on mass changes and dissipation. Resistance changes below 0.3 Ω were measured with corresponding dissipation values of 0.01 µU (micro dissipation units). The broadband impedance capabilities allow measurements between 20 Hz and 120 MHz including higher harmonic modes of up to 11th order for a 10 MHz fundamental resonance frequency quartz crystal. We demonstrate the adsorbed mass, calibrated resistance, and quantitative dissipation measurements on two biological systems including the high affinity based avidin-biotin interaction and nano-assemblies of polyelectrolyte layers. The binding affinity of a protein-antibody interaction was determined. The impedance QCM is a versatile and simple method for accurate and calibrated resistance and dissipation measurements with broadband measurement capabilities for higher harmonics measurements.
      PubDate: 2016-05-25
      DOI: 10.3390/bios6020023
      Issue No: Vol. 6, No. 2 (2016)
       
  • Biosensors, Vol. 6, Pages 24: Rapid Detection of Food Allergens by
           Microfluidics ELISA-Based Optical Sensor

    • Authors: Xuan Weng, Gautam Gaur, Suresh Neethirajan
      First page: 24
      Abstract: The risks associated with the presence of hidden allergens in food have increased the need for rapid, sensitive, and reliable methods for tracing food allergens in commodities. Conventional enzyme immunosorbent assay (ELISA) has usually been performed in a centralized lab, requiring considerable time and sample/reagent consumption and expensive detection instruments. In this study, a microfluidic ELISA platform combined with a custom-designed optical sensor was developed for the quantitative analysis of the proteins wheat gluten and Ara h 1. The developed microfluidic ELISA biosensor reduced the total assay time from hours (up to 3.5 h) to 15–20 min and decreased sample/reagent consumption to 5–10 μL, compared to a few hundred microliters in commercial ELISA kits, with superior sensitivity. The quantitative capability of the presented biosensor is a distinctive advantage over the commercially available rapid methods such as lateral flow devices (LFD) and dipstick tests. The developed microfluidic biosensor demonstrates the potential for sensitive and less-expensive on-site determination for rapidly detecting food allergens in a complex sample system.
      PubDate: 2016-06-07
      DOI: 10.3390/bios6020024
      Issue No: Vol. 6, No. 2 (2016)
       
  • Biosensors, Vol. 6, Pages 25: Optimal Magnetic Field for Crossing
           Super-Para-Magnetic Nanoparticles through the Brain Blood Barrier: A
           Computational Approach

    • Authors: Maysam Pedram, Amir Shamloo, Aria Alasty, Ebrahim Ghafar-Zadeh
      First page: 25
      Abstract: This paper scrutinizes the magnetic field effect to deliver the superparamagnetic nanoparticles (SPMNs) through the Blood Brain Barrier (BBB). Herein we study the interaction between the nanoparticle (NP) and BBB membrane using Molecular Dynamic (MD) techniques. The MD model is used to enhance our understanding of the dynamic behavior of SPMNs crossing the endothelial cells in the presence of a gradient magnetic field. Actuation of NPs under weak magnetic field offers the great advantage of a non-invasive drug delivery without the risk of causing injury to the brain. Furthermore, a weak magnetic portable stimulator can be developed using low complexity prototyping techniques. Based on MD simulation results in this paper, SPMNs can cross the cell membrane while experiencing very weak mechanical forces in the range of pN. This study also derives guidelines for the design of the SPMNs dedicated to crossing the BBB using external magnetic fields.
      PubDate: 2016-06-14
      DOI: 10.3390/bios6020025
      Issue No: Vol. 6, No. 2 (2016)
       
  • Biosensors, Vol. 6, Pages 26: Integrating Nanostructured Artificial
           Receptors with Whispering Gallery Mode Optical Microresonators via
           Inorganic Molecular Imprinting Techniques

    • Authors: G. Hammond, Adam Vojta, Sheila Grant, Heather Hunt
      First page: 26
      Abstract: The creation of label-free biosensors capable of accurately detecting trace contaminants, particularly small organic molecules, is of significant interest for applications in environmental monitoring. This is achieved by pairing a high-sensitivity signal transducer with a biorecognition element that imparts selectivity towards the compound of interest. However, many environmental pollutants do not have corresponding biorecognition elements. Fortunately, biomimetic chemistries, such as molecular imprinting, allow for the design of artificial receptors with very high selectivity for the target. Here, we perform a proof-of-concept study to show how artificial receptors may be created from inorganic silanes using the molecular imprinting technique and paired with high-sensitivity transducers without loss of device performance. Silica microsphere Whispering Gallery Mode optical microresonators are coated with a silica thin film templated by a small fluorescent dye, fluorescein isothiocyanate, which serves as our model target. Oxygen plasma degradation and solvent extraction of the template are compared. Extracted optical devices are interacted with the template molecule to confirm successful sorption of the template. Surface characterization is accomplished via fluorescence and optical microscopy, ellipsometry, optical profilometry, and contact angle measurements. The quality factors of the devices are measured to evaluate the impact of the coating on device sensitivity. The resulting devices show uniform surface coating with no microstructural damage with Q factors above 106. This is the first report demonstrating the integration of these devices with molecular imprinting techniques, and could lead to new routes to biosensor creation for environmental monitoring.
      PubDate: 2016-06-15
      DOI: 10.3390/bios6020026
      Issue No: Vol. 6, No. 2 (2016)
       
  • Biosensors, Vol. 6, Pages 27: Computational Assessment of Neural Probe and
           Brain Tissue Interface under Transient Motion

    • Authors: Michael Polanco, Sebastian Bawab, Hargsoon Yoon
      First page: 27
      Abstract: The functional longevity of a neural probe is dependent upon its ability to minimize injury risk during the insertion and recording period in vivo, which could be related to motion-related strain between the probe and surrounding tissue. A series of finite element analyses was conducted to study the extent of the strain induced within the brain in an area around a neural probe. This study focuses on the transient behavior of neural probe and brain tissue interface with a viscoelastic model. Different stages of the interface from initial insertion of neural probe to full bonding of the probe by astro-glial sheath formation are simulated utilizing analytical tools to investigate the effects of relative motion between the neural probe and the brain while friction coefficients and kinematic frequencies are varied. The analyses can provide an in-depth look at the quantitative benefits behind using soft materials for neural probes.
      PubDate: 2016-06-16
      DOI: 10.3390/bios6020027
      Issue No: Vol. 6, No. 2 (2016)
       
  • Biosensors, Vol. 6, Pages 1: Asymmetric Mach–Zehnder Interferometer
           Based Biosensors for Aflatoxin M1 Detection

    • Authors: Tatevik Chalyan, Romain Guider, Laura Pasquardini, Manuela Zanetti, Floris Falke, Erik Schreuder, Rene Heideman, Cecilia Pederzolli, Lorenzo Pavesi
      First page: 1
      Abstract: In this work, we present a study of Aflatoxin M1 detection by photonic biosensors based on Si3N4 Asymmetric Mach–Zehnder Interferometer (aMZI) functionalized with antibodies fragments (Fab′). We measured a best volumetric sensitivity of 104 rad/RIU, leading to a Limit of Detection below 5 × 10−7 RIU. On sensors functionalized with Fab′, we performed specific and non-specific sensing measurements at various toxin concentrations. Reproducibility of the measurements and re-usability of the sensor were also investigated.
      PubDate: 2016-01-06
      DOI: 10.3390/bios6010001
      Issue No: Vol. 6, No. 1 (2016)
       
  • Biosensors, Vol. 6, Pages 2: Cancer-Cells on Chip for Label-Free Detection
           of Secreted Molecules

    • Authors: Ophélie Berthuy, Loïc Blum, Christophe Marquette
      First page: 2
      Abstract: In the present report, we are making the proof of concept of cell small populations (from 1 to 100 cells) spotting, culture and secretion detection on a gold surface. In order to keep the cells in a hydrated environment during the robotized micropipetting and to address different cell lines on a single chip, a biocompatible alginate polymer was used. This approach enables the encapsulation of the cell in a very small volume (30 nL), directly on the substrate and permits a precise control of the number of cells in each alginate bead. After 24 h of culture, the adherent cells are ready for surface plasmon resonance imaging (SPRi) experimentation. To enable the detection of secreted proteins, various antibodies are immobilized in an organized manner on a SPRi sensor and permitted the multiplex detection of different proteins secreted by the different cultured cell lines. Evidence of the real-time detection will be presented for Prostate Specific Antigen (PSA) and β-2-microglobulin (B2M) secreted by prostate cancer cells following induction by dihydrotestosterone (DHT). Different kinetics for the two secreted proteins were then demonstrated and precisely determined using the chip.
      PubDate: 2016-01-15
      DOI: 10.3390/bios6010002
      Issue No: Vol. 6, No. 1 (2016)
       
  • Biosensors, Vol. 6, Pages 3: Acknowledgement to Reviewers of Biosensors in
           2015

    • Authors: Biosensors Editorial Office
      First page: 3
      Abstract: The editors of Biosensors would like to express their sincere gratitude to the following reviewers for assessing manuscripts in 2015. [...]
      PubDate: 2016-01-22
      DOI: 10.3390/bios6010003
      Issue No: Vol. 6, No. 1 (2016)
       
  • Biosensors, Vol. 6, Pages 4: Variation in Gas and Volatile Compound
           Emissions from Human Urine as It Ages, Measured by an Electronic Nose

    • Authors: Siavash Esfahani, Nidhi Sagar, Ioannis Kyrou, Ella Mozdiak, Nicola O’Connell, Chuka Nwokolo, Karna Bardhan, Ramesh Arasaradnam, James Covington
      First page: 4
      Abstract: The medical profession is becoming ever more interested in the use of gas-phase biomarkers for disease identification and monitoring. This is due in part to its rapid analysis time and low test cost, which makes it attractive for many different clinical arenas. One technology that is showing promise for analyzing these gas-phase biomarkers is the electronic nose—an instrument designed to replicate the biological olfactory system. Of the possible biological media available to “sniff”, urine is becoming ever more important as it is easy to collect and to store for batch testing. However, this raises the question of sample storage shelf-life, even at −80 °C. Here we investigated the effect of storage time (years) on stability and reproducibility of total gas/vapour emissions from urine samples. Urine samples from 87 patients with Type 2 Diabetes Mellitus were collected over a four-year period and stored at −80 °C. These samples were then analyzed using FAIMS (field-asymmetric ion mobility spectrometry—a type of electronic nose). It was discovered that gas emissions (concentration and diversity) reduced over time. However, there was less variation in the initial nine months of storage with greater uniformity and stability of concentrations together with tighter clustering of the total number of chemicals released. This suggests that nine months could be considered a general guide to a sample shelf-life.
      PubDate: 2016-01-25
      DOI: 10.3390/bios6010004
      Issue No: Vol. 6, No. 1 (2016)
       
  • Biosensors, Vol. 6, Pages 5: Developing Biosensors in Developing
           Countries: South Africa as a Case Study

    • Authors: Ronen Fogel, Janice Limson
      First page: 5
      Abstract: A mini-review of the reported biosensor research occurring in South Africa evidences a strong emphasis on electrochemical sensor research, guided by the opportunities this transduction platform holds for low-cost and robust sensing of numerous targets. Many of the reported publications centre on fundamental research into the signal transduction method, using model biorecognition elements, in line with international trends. Other research in this field is spread across several areas including: the application of nanotechnology; the identification and validation of biomarkers; development and testing of biorecognition agents (antibodies and aptamers) and design of electro-catalysts, most notably metallophthalocyanine. Biosensor targets commonly featured were pesticides and metals. Areas  of regional import to sub-Saharan Africa, such as HIV/AIDs and tuberculosis diagnosis, are also apparent in a review of the available literature. Irrespective of the targets, the challenge to the effective deployment of such sensors remains shaped by social and economic realities such that the requirements thereof are for low-cost and universally easy to operate devices for field settings. While it is difficult to disentangle the intertwined roles of national policy, grant funding availability and, certainly, of global trends in shaping areas of emphasis in research, most notable is the strong role that nanotechnology, and to a certain extent biotechnology, plays in research regarding biosensor construction. Stronger emphasis on collaboration between scientists in theoretical modelling, nanomaterials application and or relevant stakeholders in the specific field (e.g., food or health monitoring) and researchers in biosensor design may help evolve focused research efforts towards development and deployment of low-cost biosensors.
      PubDate: 2016-02-02
      DOI: 10.3390/bios6010005
      Issue No: Vol. 6, No. 1 (2016)
       
  • Biosensors, Vol. 6, Pages 6: Protein-Flavonoid Interaction Studies by a
           Taylor Dispersion Surface Plasmon Resonance (SPR) Technique: A Novel
           Method to Assess Biomolecular Interactions

    • Authors: Preejith Vachali, Binxing Li, Brian Besch, Paul Bernstein
      First page: 6
      Abstract: Flavonoids are common polyphenolic compounds widely distributed in fruits and vegetables. These pigments have important pharmacological relevance because emerging research suggests possible anti-cancer and anti-inflammatory properties as well other beneficial health effects. These compounds are relatively hydrophobic molecules, suggesting the role of blood transport proteins in their delivery to tissues. In this study, we assess the binding interactions of four flavonoids (kaempferol, luteolin, quercetin, and resveratrol) with human serum albumin (HSA), the most abundant protein in the blood, and with glutathione S-transferase pi isoform-1 (GSTP1), an enzyme with well-characterized hydrophobic binding sites that plays an important role in detoxification of xenobiotics with reduced glutathione, using a novel Taylor dispersion surface plasmon resonance (SPR) technique. For the first time, HSA sites revealed a high-affinity binding site for flavonoid interactions. Out of the four flavonoids that we examined, quercetin and kaempferol showed the strongest equilibrium binding affinities (KD) of 63 ± 0.03 nM and 37 ± 0.07 nM, respectively. GSTP1 displayed lower affinities in the micromolar range towards all of the flavonoids tested. The interactions of flavonoids with HSA and GSTP1 were studied successfully using this novel SPR assay method. The new method is compatible with both kinetic and equilibrium analyses.
      PubDate: 2016-02-25
      DOI: 10.3390/bios6010006
      Issue No: Vol. 6, No. 1 (2016)
       
  • Biosensors, Vol. 6, Pages 7: Comparison of Electrochemical Immunosensors
           and Aptasensors for Detection of Small Organic Molecules in Environment,
           Food Safety, Clinical and Public Security

    • Authors: Benoit Piro, Shihui Shi, Steeve Reisberg, Vincent Noël, Guillaume Anquetin
      First page: 7
      Abstract: We review here the most frequently reported targets among the electrochemical immunosensors and aptasensors: antibiotics, bisphenol A, cocaine, ochratoxin A and estradiol. In each case, the immobilization procedures are described as well as the transduction schemes and the limits of detection. It is shown that limits of detections are generally two to three orders of magnitude lower for immunosensors than for aptasensors, due to the highest affinities of antibodies. No significant progresses have been made to improve these affinities, but transduction schemes were improved instead, which lead to a regular improvement of the limit of detections corresponding to ca. five orders of magnitude over these last 10 years. These progresses depend on the target, however.
      PubDate: 2016-02-29
      DOI: 10.3390/bios6010007
      Issue No: Vol. 6, No. 1 (2016)
       
  • Biosensors, Vol. 6, Pages 8: Aryl Diazonium Chemistry for the Surface
           Functionalization of Glassy Biosensors

    • Authors: Wei Zheng, Remko van den Hurk, Yong Cao, Rongbing Du, Xuejun Sun, Yiyu Wang, Mark McDermott, Stephane Evoy
      First page: 8
      Abstract: Nanostring resonator and fiber-optics-based biosensors are of interest as they offer high sensitivity, real-time measurements and the ability to integrate with electronics. However, these devices are somewhat impaired by issues related to surface modification. Both nanostring resonators and photonic sensors employ glassy materials, which are incompatible with electrochemistry. A surface chemistry approach providing strong and stable adhesion to glassy surfaces is thus required. In this work, a diazonium salt induced aryl film grafting process is employed to modify a novel SiCN glassy material. Sandwich rabbit IgG binding assays are performed on the diazonium treated SiCN surfaces. Fluorescently labelled anti-rabbit IgG and anti-rabbit IgG conjugated gold nanoparticles were used as markers to demonstrate the absorption of anti-rabbit IgG and therefore verify the successful grafting of the aryl film. The results of the experiments support the effectiveness of diazonium chemistry for the surface functionalization of SiCN surfaces. This method is applicable to other types of glassy materials and potentially can be expanded to various nanomechanical and optical biosensors.
      PubDate: 2016-03-14
      DOI: 10.3390/bios6010008
      Issue No: Vol. 6, No. 1 (2016)
       
  • Biosensors, Vol. 6, Pages 9: Multi-Wire Tri-Gate Silicon Nanowires
           Reaching Milli-pH Unit Resolution in One Micron Square Footprint

    • Authors: Enrico Accastelli, Paolo Scarbolo, Thomas Ernst, Pierpaolo Palestri, Luca Selmi, Carlotta Guiducci
      First page: 9
      Abstract: The signal-to-noise ratio of planar ISFET pH sensors deteriorates when reducing the area occupied by the device, thus hampering the scalability of on-chip analytical systems which detect the DNA polymerase through pH measurements. Top-down nano-sized tri-gate transistors, such as silicon nanowires, are designed for high performance solid-state circuits thanks to their superior properties of voltage-to-current transduction, which can be advantageously exploited for pH sensing. A systematic study is carried out on rectangular-shaped nanowires developed in a complementary metal-oxide-semiconductor (CMOS)-compatible technology, showing that reducing the width of the devices below a few hundreds of nanometers leads to higher charge sensitivity. Moreover, devices composed of several wires in parallel further increase the exposed surface per unit footprint area, thus maximizing the signal-to-noise ratio. This technology allows a sub milli-pH unit resolution with a sensor footprint of about 1 µm2, exceeding the performance of previously reported studies on silicon nanowires by two orders of magnitude.
      PubDate: 2016-03-15
      DOI: 10.3390/bios6010009
      Issue No: Vol. 6, No. 1 (2016)
       
  • Biosensors, Vol. 6, Pages 10: Sensing of Salivary Glucose Using
           Nano-Structured Biosensors

    • Authors: Yunqing Du, Wenjun Zhang, Ming Wang
      First page: 10
      Abstract: The anxiety and pain associated with frequent finger pricking has always been troublesome for diabetics measuring blood glucose (BG) in their daily lives. For this reason, a reliable glucose monitoring system that allows noninvasive measurements is highly desirable. Our main objective is to develop a biosensor that can detect low-level glucose in saliva (physiological range 0.5–20 mg/dL). Salivary glucose (SG) sensors were built using a layer-by-layer self-assembly of single-walled carbon nanotubes, chitosan, gold nanoparticles, and glucose oxidase onto a screen-printed platinum electrode. An electrochemical method was utilized for the quantitative detection of glucose in both buffer solution and saliva samples. A standard spectrophotometric technique was used as a reference method to validate the glucose content of each sample. The disposable glucose sensors have a detection limit of 0.41 mg/dL, a sensitivity of 0.24 μA·s·dL·mg−1, a linear range of 0.5–20 mg/dL in buffer solution, and a response time of 30 s. A study of 10 healthy subjects was conducted, and SG levels between 1.1 to 10.1 mg/dL were successfully detected. The results revealed that the noninvasive SG monitoring could be an alternative for diabetes self-management at home. This paper is not intended to replace regular BG tests, but to study SG itself as an indicator for the quality of diabetes care. It can potentially help patients control and monitor their health conditions, enabling them to comply with prescribed treatments for diabetes.
      PubDate: 2016-03-17
      DOI: 10.3390/bios6010010
      Issue No: Vol. 6, No. 1 (2016)
       
 
 
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