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Joseph Wang - One of the best experts on this subject based on the ideXlab platform.
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v type nerve agent detection using a carbon nanotube based amperometric Enzyme Electrode
Analytical Chemistry, 2006Co-Authors: Kanchan A Joshi, Joseph Wang, Wilfred Chen, Marek Prouza, Jason M Tang, Robert C Haddon, Ashok MulchandaniAbstract:An Enzyme Electrode for the detection of V-type nerve agents, VX (O-ethyl-S-2-diisopropylaminoethyl methylphosphonothioate) and R-VX (O-isobutyl-S-2-diethylaminoethyl methylphosphonothioate), is proposed. The principle of the new biosensor is based on the Enzyme-catalyzed hydrolysis of the nerve agents and amperometric detection of the thiol-containing hydrolysis products at carbon nanotube-modified screen-printed Electrodes. Demeton-S was used as a nerve agent mimic. 2-(Diethylamino)ethanethiol (DEAET) and 2-(dimethylamino)ethanethiol (DMAET), the thiol-containing hydrolysis product and hydrolysis product mimic of R-VX and VX, respectively, were monitored by exploiting the electrocatalytic activity of carbon nanotubes (CNT). As low as 2 μM DMAET and 0.8 μM DEAET were detected selectively at a low applied potential of 0.5 V vs Ag/AgCl at a CNT-modified mediator-free amperometric Electrode. Further, the large surface area and the hydrophobicity of CNT was used to immobilize organophosphorus hydrolase mutan...
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Graphite-teflon Enzyme Electrode
Electroanalysis, 1993Co-Authors: Joseph Wang, A. Julio Reviejo, Lúcio AngnesAbstract:The fabrication and performance of graphite-Teflon-Enzyme Electrodes are described. The new bulk-modified composite Enzyme Electrodes couple the advantages of renewable (polishable) surfaces, mechanical rigidity, fast response, and favorable signal-to-noise characteristics. The new fabrication strategy is illustrated for the immobilization of horseradish peroxidase and glucose oxidase, in connection with measurements of peroxide species and glucose, respectively. The incorporation of a ferrocene mediator to yield a reagentless device is also illustrated. Flow injection measurements of hydrogen peroxide with the graphite-Teflon-peroxidase detector are carried out at 120 samples/hour, to yield a detection limit of 2.5 × 10−6 M and a relative standard deviation of 2%. Applicability to organic-phase biosensing is illustrated.
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Graphite???teflon Enzyme Electrode
Electroanalysis, 1993Co-Authors: Joseph Wang, A. Julio Reviejo, Lúcio AngnesAbstract:The fabrication and performance of graphite‐Teflon‐Enzyme Electrodes are described. The new bulk‐modified composite Enzyme Electrodes couple the advantages of renewable (polishable) surfaces, mechanical rigidity, fast response, and favorable signal‐to‐noise characteristics. The new fabrication strategy is illustrated for the immobilization of horseradish peroxidase and glucose oxidase, in connection with measurements of peroxide species and glucose, respectively. The incorporation of a ferrocene mediator to yield a reagentless device is also illustrated. Flow injection measurements of hydrogen peroxide with the graphite‐Teflon‐peroxidase detector are carried out at 120 samples/hour, to yield a detection limit of 2.5 × 10 −6 M and a relative standard deviation of 2%. Applicability to organic‐phase biosensing is illustrated. Copyright © 1993 VCH Publishers, Inc.
Lúcio Angnes - One of the best experts on this subject based on the ideXlab platform.
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Graphite-teflon Enzyme Electrode
Electroanalysis, 1993Co-Authors: Joseph Wang, A. Julio Reviejo, Lúcio AngnesAbstract:The fabrication and performance of graphite-Teflon-Enzyme Electrodes are described. The new bulk-modified composite Enzyme Electrodes couple the advantages of renewable (polishable) surfaces, mechanical rigidity, fast response, and favorable signal-to-noise characteristics. The new fabrication strategy is illustrated for the immobilization of horseradish peroxidase and glucose oxidase, in connection with measurements of peroxide species and glucose, respectively. The incorporation of a ferrocene mediator to yield a reagentless device is also illustrated. Flow injection measurements of hydrogen peroxide with the graphite-Teflon-peroxidase detector are carried out at 120 samples/hour, to yield a detection limit of 2.5 × 10−6 M and a relative standard deviation of 2%. Applicability to organic-phase biosensing is illustrated.
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Graphite???teflon Enzyme Electrode
Electroanalysis, 1993Co-Authors: Joseph Wang, A. Julio Reviejo, Lúcio AngnesAbstract:The fabrication and performance of graphite‐Teflon‐Enzyme Electrodes are described. The new bulk‐modified composite Enzyme Electrodes couple the advantages of renewable (polishable) surfaces, mechanical rigidity, fast response, and favorable signal‐to‐noise characteristics. The new fabrication strategy is illustrated for the immobilization of horseradish peroxidase and glucose oxidase, in connection with measurements of peroxide species and glucose, respectively. The incorporation of a ferrocene mediator to yield a reagentless device is also illustrated. Flow injection measurements of hydrogen peroxide with the graphite‐Teflon‐peroxidase detector are carried out at 120 samples/hour, to yield a detection limit of 2.5 × 10 −6 M and a relative standard deviation of 2%. Applicability to organic‐phase biosensing is illustrated. Copyright © 1993 VCH Publishers, Inc.
Won Jun Sung - One of the best experts on this subject based on the ideXlab platform.
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a glucose oxidase Electrode based on polypyrrole with polyanion peg Enzyme conjugate dopant
Biosensors and Bioelectronics, 2003Co-Authors: Won Jun SungAbstract:Abstract This study investigated a new glucose sensor prepared by electrochemical polymerization of pyrrole with polyanion/poly(ethylene glycol) (PEG)/glucose oxidase (GOD) conjugate dopants. GOD was coupled to a strong polyanion, poly(2-acrylamido-2-methylpropane sulfonic acid) (AMPS) via PEG spacer to effectively and reproducibly immobilize GOD within a polypyrrole matrix onto a Pt Electrode surface. PEGs with four different chain lengths (1000, 2000, 3000, and 4000) were used as spacers to study the spacer length effect on Enzyme immobilization and Electrode function. After conjugation, more than 90% of the GOD bioactivity was preserved and the bioactivity of the conjugated GOD increased with longer PEG spacers. The resulting polyanion/PEG/GOD conjugate was used as a dopant for electropolymerizing pyrrole. The activity of the immobilized Enzyme on the Electrode ranged from 119 to 209 mU cm −2 and the bioactivity increased with the use of longer PEG spacers. The amperometric response of the Enzyme Electrode was linear up to 20 mM glucose concentration with a sensitivity ranging from 180 to 270 nA mM −1 cm −2 . The kinetic parameters Michaelis–Menten constant (K M app ) and maximum current density ( j max ) depended on the amount of active Enzyme, level of substrate diffusion, and PEG spacer length. An increase in the electrical charge passed during polymerization (thus, increasing polypyrrole thickness) to 255 mC cm −2 increased the sensitivity of the Enzyme Electrode because of the greater amount of incorporated Enzyme. However, although the amount of incorporated GOD continued to increase when the charge increased above 255 mC cm −2 , the sensitivity began to decline gradually. The condition for preparing the Enzyme Electrode was optimized at 800 mV potential with a dopant concentration of 1 mg ml −1 .
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a glucose oxidase Electrode based on electropolymerized conducting polymer with polyanion Enzyme conjugated dopant
Analytical Chemistry, 2000Co-Authors: Won Jun SungAbstract:An Enzyme immobilization method has been developed by electropolymerization chemistry of conducting polymer which results in a more effective and reproducible Enzyme Electrode. As a model system, in this study, glucose oxidase (GOD) was conjugated with a polyanion, poly(2-acrylamido-2-methylpropane sulfonic acid), via a poly(ethylene oxide) spacer to improve the efficiency of Enzyme immobilization into a conducting polymer. GOD was successfully conjugated with a high conjugation yield of more than 90%, and its bioactivity was preserved. The resulting polyanion−GOD conjugate was used as a dopant for the electrochemical polymerization of pyrrole. Polypyrrole was effectively deposited on a Pt wire working Electrode with the polyanion−GOD conjugate. The Enzyme Electrode responded to glucose concentrations of up to 20 mM with a sensitivity of 40 nA/mM at an applied potential of 0.4 V within a response time of 30 s. Although the response signal decreased at the low applied potential of 0.3 V, the Enzyme electro...
Esma Kılıç - One of the best experts on this subject based on the ideXlab platform.
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Amperometric carbon paste Enzyme Electrodes for uric acid determination with different mediators
Collection of Czechoslovak Chemical Communications, 2020Co-Authors: Pınar Esra Erden, Şule Pekyardımcı, Esma KılıçAbstract:In this study, two new amperometric carbon paste Enzyme Electrodes for determination of uric acid were developed. The carbon paste was prepared by mixing uricase Enzyme, 1,4-benzoquinone or poly(vinylferrocene) (PVF) as a mediator, graphite powder, paraffin oil and then the paste was placed into cavity of a teflon Electrode body. Determination of uric acid was performed by oxidation of enzymatically generated H 2 O 2 . The effects of Enzyme loading, mediator amount, buffer type, pH, buffer concentration, working potential and temperature were investigated for both Electrodes. The working range of the 1,4-benzoquinone modified Enzyme Electrode was 1.9 × 10 –8 –2.7 × 10 –3 M, detection limit 1.9 × 10 –8 M and response time 150 s. Optimum buffer type, pH, buffer concentration, working potential, temperature and amounts of Enzyme and mediator for 1,4-benzoquinone modified Enzyme Electrode were found to be Tris, 8.0, 0.20 M, +0.25 V, 30 °C, 2.0 Unit and 13%, respectively. The working range of the PVF modified Enzyme Electrode was 7.4 × 10 –8 –7.0 × 10 –3 M, detection limit 7.4 × 10 –8 M and response time 120 s. Optimum buffer type, pH, buffer concentration, working potential, temperature and amounts of Enzyme and mediator for PVF modified Enzyme Electrode were found to be phosphate, 8.0, 0.05 M, +0.70 and +0.30 V, 40 °C, 2.0 Unit and 10.9%, respectively. The repeatability, storage stability of the Enzyme Electrodes and interference effects were also investigated. Enzyme Electrodes were used for determination of uric acid in serum samples and the results were in a good agreement with those obtained by commercial enzymatic kits.
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Amperometric Enzyme Electrodes for xanthine determination with different mediators.
Acta Chimica Slovenica, 2012Co-Authors: Pınar Esra Erden, Şule Pekyardımcı, Esma KılıçAbstract:Two new amperometric carbon paste Enzyme Electrodes were developed for xanthine determination. 1,4-benzoquinone and poly(vinylferrocene) (PVF) were investigated as mediators. The parameters affecting the analytical performance of the Enzyme Electrode have been investigated in detail and optimized for modified Enzyme Electrodes. 1,4-benzoquinone modified Enzyme Electrode (BQ-CPEE) exhibited linear response from 1.9 × 10-7 M to 5.5 × 10-6 M and from 5.2 × 10-5 M to 8.2 × 10-4 M with a good detection limit of 1.0 × 10-7 M. The linear working range of the PVF modified Enzyme Electrode was between 1.9 × 10-7-2.1 × 10-6 M, 1.9 × 10-6-1.0 × 10-5 M and 1.1 × 10-4-8.8 × 10-4 M with a detection limit of 1.0 × 10-7 M. Hypoxanthine response of the Electrodes was also determined. Modified Enzyme Electrodes were used for xanthine determination in real samples and good recoveries were obtained.
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A new amperometric carbon paste Enzyme Electrode for ethanol determination
Analytical Letters, 2007Co-Authors: Derya Koyuncu, Pınar Esra Erden, Şule Pekyardımcı, Esma KılıçAbstract:Abstract In this study, a new amperometric carbon paste Enzyme Electrode for determination of ethanol was developed. The carbon paste was prepared by mixing alcohol dehydrogenase, its coEnzyme nicotinamide adenine dinucleotide (oxidized form, NAD+), poly(vinylferrocene) (PVF) that was used as a mediator, graphite powder and paraffin oil, then the paste was placed into cavity of a glass Electrode body. Determination of ethanol was performed by oxidation of nicotinamide adenine dinucleotide (reduced form, NADH) generated enzymatically at +0.7 V. The effects of Enzyme, coEnzyme and PVF amounts; pH; buffer concentration and temperature were investigated. The linear working range of the Enzyme Electrode was 4.0×10−4–4.5×10−3 M, determination limit was 3.9×10−4 M and response time was 50 s. The optimum pH, buffer concentration, temperature, and amounts of Enzyme, NAD+ and PVF for Enzyme Electrode were found to be 8.5, 0.10 M, 37°C, 2.0, 6.0, and 12.0 mg, respectively. The storage stability of Enzyme Electrode a...
Xinjian Feng - One of the best experts on this subject based on the ideXlab platform.
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a high performance three phase Enzyme Electrode based on superhydrophobic mesoporous silicon nanowire arrays for glucose detection
Nanoscale, 2016Co-Authors: Chenlong Xu, Zhiqian Song, Qun Xiang, Xinjian FengAbstract:We describe here a high performance oxygen-rich three-phase Enzyme Electrode based on superhydrophobic mesoporous silicon nanowire arrays for glucose detection. We demonstrate that its linear detection upper limit is 30 mM, more than 15 times higher than that can be obtained on the normal Enzyme-Electrode. Notably, the three-phase Enzyme Electrode output is insensitive to the significant oxygen level fluctuation in analyte solution.