Ceramic carbon/polypyrrole materials for the construction of bienzymatic amperometric biosensor for glucose

A novel amperometric glucose biosensor was constructed by electrochemical formation of a polypyrrole (PPy) membrane in the presence of glucose oxidase (GOD) on the surface of a horseradish peroxidase (HRP) modified ferrocenecarboxylic acid (FCA) mediated sol-gel derived ceramic carbon electrode. The amperometric detection of glucose was carried out at +0.16 V (vs. SCE) in 0.1 mol/L phosphate buffer solution (pH 6.9) with a linear response range between 8.0x10(-5) and 1.3x10(-3) mol/L of glucose. The biosensor showed a good suppression of interference and a negligible deviation in the amperometric detection.

Capacitive detection of glucose using molecularly imprinted polymers

A novel glucose biosensor based on capacitive detection has been developed using molecularly imprinted polymers. The sensitive layer was prepared by electropolymerization of o-phenylenediamine on a gold electrode in the presence of the template (glucose). Cyclic voltammetry and capacitive measurements monitored the process of electropolymerization. Surface uncovered areas were plugged with 1-dodecanethiol to make the layer dense, and the insulating properties of the layer were studied in the presence of redox couples. The template molecules and the nonbound thiol were removed from the modified electrode surface by washing with distilled water. A capacitance decrease could be obtained after injection of glucose. The electrode constructed similarly but with ascorbic acid or fructose only showed a small response compared with glucose. The stability and reproducibility of the biosensor were also investigated. (C) 2001 Elsevier Science B.V. All rights reserved.

Cobalt(II)hexacyanoferrate film modified glassy carbon electrode for construction of a glucose biosensor

An amperometric glucose biosensor was constructed based on a glassy carbon electrode modified with a Cobalt(II)hexacyanoferrate film which catalyzes electroreduction of hydrogen peroxide. Gelatin was used as immobilization matrix. Interference could be effectively eliminated by the combination of low detection potential with a Nafion coating. A low applied potential can avoid oxidation of interferences such as ascorbic acid, uric acid, p-acetyl-aminophenol, etc.. Nafion coating prevents interferences from access to the electrode surface by electrostatic repulsion. A wide linear range of detection was obtained. Analytical performance parameters are given and kinetic analysis discussed.

Chemiluminescent determination of glucose with a modified carbon paste electrode

A flow injection analysis detection method for glucose is presented which is based on the oxidation of glucose by glucose oxidase followed by chemiluminescent detection of hydrogen peroxide. Both glucose oxidase and hematin, a chemiluminescent reaction catalyst, were bulk-immobilized conveniently by direct mixing with carbon paste, which allows renewal of the electrode surface by simply polishing or cutting to expose a new and fully active surface in the case of fouling. Luminol in reagent solution passed through the flow cell and reacted with hydrogen peroxide produced by the enzyme reactor in the presence of the catalyst to yield light. An applied potential of -0.4 V avoided the electrode fouling effectively. The log-log plot of the emitted light intensity vs glucose concentration was linear over the range of 1-100 mmol L-1 with a correlation coefficient of 0.992. Application of this method to other chemiluminescent and bioluminescent systems is suggested. (C) 1999 Academic Press.

Evaluation of luminol-H2O2-KIO4 chemiluminescence system and its application to hydrogen peroxide, glucose and ascorbic acid assays

(A) novel chemiluminescence (CL) system was evaluated for the determination of hydrogen peroxide, glucose and ascorbic acid based on hydrogen peroxide, which has a catalytic-cooxidative effect on the oxidation of luminol by KIO4. Hydrogen peroxide can be directly determined by luminol-KIO4 -H2O2 CL system. The detection limit was 3.0 x 10(-8) mol l(-1) and the calibration graph was linear over the range of 2.0 x 10(-7)-6.0 x 10(-4) mol l(-1). The relative standard deviation of H2O2 was 1.1% for 2.0 x 10(-6) mol l(-1) (N = 11). Glucose was indirectly determined through measuring the H2O2 generated by the oxidation of glucose in the presence of glucose oxidase at pH 7.6. The present method provides a source for H2O2, which, in turn, coupled with the luminol-KIO4-H2O2 CL reaction system. The CL was linearly correlated with glucose concentration of 0.6-110 mu g ml(-1). The relative standard deviation was 2.1% for 10 mu g ml(-1) (N = 11). Detection limit of glucose was 0.08 mu g ml(-1). Ascorbic acid was also indirectly determined by the suppression of luminol-KIO4-H2O2 CL system. The calibration curve was linear over the range of 1.0 x 10(-7)-1.0 x 10(-5) mol l(-1) of ascorbic acid. The relative standard deviation was 1.0% for 8.0 x 10(-7) mol l(-1) (N = 11). Detection limit of ascorbic acid was 6.0 x 10(=8) mol l(-1). These proposed methods have been applied to determine glucose, ascorbic acid in tablets and injection. (C) 1999 Elsevier Science B.V. All rights reserved.

Self-gelatinizable copolymer immobilized glucose biosensor based on Prussian Blue modified graphite electrode

A novel poly(vinyl alcohol) grafting 4-vinylpyridine self-gelatinizable copolymer was adapted to immobilize glucose oxidase. The reduction of hydrogen peroxide (H2O2) was detected at a Prussian Blue (PB) modified graphite electrode. A stable and sensitive glucose amperometric biosensor is described. The copolymer is a good biocompatible polymer in which the glucose oxidase retains high activity. Moreover, the copolymer can adhere firmly to the inorganic PB membrane. The sensor showed an apparent Michaelis-Menten constant of 18 +/- 0.2 mM and a maximum current density of 1.14 mu A cm(-2) mM(-1). The linear range is from 5 mu M to 4.5 mM glucose and the detection limit is 0.5. mu M glucose. The catalytic efficiency of PB for the reduction of H2O2 is higher than that for the oxidation of H2O2. Glucose concentrations in serum samples from healthy persons and diabetic patients were determined using the sensor. The results compared well with those provided by the hospital using a spectroscopy method.

Amperometric glucose biosensor based on sol-gel organic-inorganic hybrid material

A new type of sol-gel organic-inorganic hybrid material was developed and used for the production of biosensors. This material is composed of silica sol and a grafting copolymer of poly(vinyl alcohol) with 4-vinylpyridine. It prevents the cracking of conventional sol-gel-derived glasses and eliminates the swelling of the hydrogel. The optimum composition of the hybrid material was first examined, and then glucose oxidase was immobilized in this matrix to demonstrate its application. The characteristics of the biosensor were studied by cyclic voltammetry and chronoamperometry. The biosensor exhibited a series of good properties: high sensitivity (600 nA mmol(-1)L(-1)), short response time (11 s) and remarkable long-term stability in storage (at least 5 months). In addition, the characteristics of the second-generation biosensor with the use of tetrathiafulvalene as a mediator mere discussed.

Direct electron communication between glucose oxidase and carbon electrode covered with polypyrrole

Glucose oxidase can be effectively adsorbed onto the polypyrrole(PPy) thin film electrochemically formed on an anodized galssy carbon electrode(GCEa). Direct electron communication between the redox of GOD and the modified electrode was successfully achieved, which was detected using cyclic voltammetry. GOD entrapped in PPy film still remained its biological activity and could catalyze the oxidation of glucose. As a third generation biosensor, GOD-PPy/GCEa responded linearly up to 20 mM glucose with a wider linear concentration range.

DIRECT ELECTROCHEMISTRY AND SURFACE CHARACTERIZATION OF GLUCOSE-OXIDASE ADSORBED ON ANODIZED CARBON ELECTRODES

The glassy carbon electrode (gce) and highly oriented pyrolytic graphite (hopg) were electrochemically anodized at a potential of +2.0 V (vs. Ag/AgCl) to create active sites and to improve the adsorption of glucose oxidase (GOD) and flavin adenine dinucle

DIRECT OBSERVATION OF NATIVE AND UNFOLDED GLUCOSE-OXIDASE STRUCTURES BY SCANNING-TUNNELING-MICROSCOPY

Native and unfolded glucose oxidase (GOD) structures have been directly observed with scanning tunnelling microscopy (STM) for the first time. STM images show an opening butterfly-shaped pattern for the native GOD. When GOD molecules are extended on anodi

FLOW-INJECTION ANALYSIS OF GLUCOSE AT AN AMPEROMETRIC GLUCOSE SENSOR-BASED ON ELECTROCHEMICAL CODEPOSITION OF PALLADIUM AND GLUCOSE-OXIDASE ON A GLASSY-CARBON ELECTRODE

A glassy carbon electrode (GCE) modified with palladium provides excellent electrocatalytic oxidation of hydrogen peroxide. When the electrolyte contains palladium chloride and glucose oxidase, the GCE can be modified by electrochemical codeposition at a given potential. The resulting modified surface was coated with a thin film of Nation to form a glucose sensor. Such a glucose sensor was successfully used in the flow-injection analysis of glucose with high stability and anti-poisoning ability. It gave a detection limit of 1 X 10(-7) M injected glucose, with a linear concentration range of 0.001-8 mM. There is no obvious interference from substances such as ascorbate and saccharides.

THERMODYNAMICS OF AMINO-ACID DISSOCIATION IN MIXED-SOLVENTS .3. GLYCINE IN AQUEOUS GLUCOSE SOLUTIONS FROM 5-DEGREES-C TO 45-DEGREES-C

The first thermodynamic dissociation constants of glycine in 5, 15 mass % glucose + water mixed solvents at five temperatures from 5 to 45-degrees-C have been determined from precise emf measurements of a cell without liquid junction using hydrogen and Ag-AgCl electrodes and a new method of polynomial approximation proposed on the basis of Pitzer's electrolytic solution theory in our previous paper. The results obtained from both methods agree within experimental error. The standard free energy of transfer for HCl from water to aqueous mixed solvent have been calculated and the results are discussed.

SENSITIVE AMPEROMETRIC DETECTION OF GLUCOSE BY REVERSED PHASE LIQUID-CHROMATOGRAPHY AT A PRUSSIAN BLUE CHEMICALLY MODIFIED ELECTRODE OF NOVEL CONSTRUCTION

A new liquid chromatography electrochemical (LCEC) scheme for glucose sensing has been developed on the basis of a Prussian Blue chemically modified electrode (CME) of novel construction and characterized in terms of various experimental parameters by the flow injection analysis (FIA) technique. Unique hydrodynamic voltammograms were obtained for the first time at the CME in the flow-through amperometric detection of glucose, and subsequently both anodic and cathodic peaks could be expected on monitoring the operating potential in the modest positive or negative region. The unique pH dependence on the CME response towards glucose makes it perfectly compatible with conventional reversed phase liquid chromatography systems. On the basis of these features, practical application in glucose LCEC detection has been effectively performed; a linear response range over three orders of magnitude and a detection limit of subpicomole level were readily obtained. The capability of the established LCEC mode in the direct sensing of urinary glucose has been demonstrated.

AMPEROMETRIC GLUCOSE SENSOR WITH FERROCENE AS AN ELECTRON-TRANSFER MEDIATOR

A glucose oxidase (GOD) electrode with ferrocene (Fc) used as an electron transfer mediator has been described. Using Nafion, Fc was modified on a glassy carbon (GC) electrode surface, and glucose oxidase was then immobilized on the Fc-Nafion film, forming a GOD-Fc-Nafion enzyme electrode. The preparation method was quite simple and rapid. The enzyme electrode showed a reversible reaction of the redox couple (Fc+/Fc), used in a biosensor system, displayed a sensitive catalytic current response (response time was less than 20 s) on variation of the glucose concentration, with a wide linear range up to 16 mM and with good repeatability. The enzyme electrode showed almost no deterioration over the course of three weeks. There was little or no interference from electro-active anions, such as ascorbic acid, to the determination of glucose based on Nafion film and lower oxidizing potentials of the enzyme electrode.

COBALT PORPHYRIN NAFION FILM ON CARBON MICROARRAY ELECTRODE TO MONITOR OXYGEN FOR ENZYME ANALYSIS OF GLUCOSE

A microcarbon array electrode was modified by the placement of a Nafion film containing cobalt tetramethylpyridyl phorphyrin on its surface. This electrode was applied to the analysis of solution glucose when it was further modified by the immobilization of glucose oxidase on the outermost surface of the Nafion by the cross-linking of serum albumin with glutaraldehyde. The concomitant decrease in the concentration of oxygen, as it was consumed in the enzymatic reaction of glucose with glucose oxidase, was determined by either cyclic voltammetry or a double potential step method at the porphyrin-Nafion catalytic electrode. Glucose could be determined in the range of 0.01-4 mM rapidly, without interference from substances such as ascorbate or other saccharides.