Theoretical Analysis of Immobilized Oxidase Enzyme Electrode in the Presence of Two Oxidants

In this paper, mathematical model of Martens and Hall (Analytical chemistry 66, 2763-2770 (1994)) for an immobilized oxidase enzyme electrode is discussed. The model involves the system of non-linear reaction diffusion equations under the steady state conditions. A simple and closed-form of approximate analytical expressions for the concentrations of the immobilization of three enzyme substrates has been derived by solving the system of non-linear reaction diffusion equations using new approach of homotopy perturbation method. Approximate polynomial expression of concentration of substrate, oxygen and oxidized mediator and current was obtained in terms of the Thiele moduli and the small values of parameters Bs, Bo and Bm (normalized surface concentration of substrate, oxygen and oxidized mediator). Furthermore, in this work the numerical simulation of the problem is also reported using Matlab program. An agreement between analytical expressions and numerical results is noted.

An Enzyme Electrode Based on the Covalently Binding of Horseradish Peroxidase to a Self-assembling Monolayer Modified Gold Electrode

A new procedure for developing high performance enzyme electrode is described. The procedure is based on the covalently binding of horseradish peroxidase to a self-assembling monolayer on a gold electrode. An enhanced catalytic current is observed with addition of hydrogen peroxide into phosphate buffer solution (PBS) in the presence of mediators. The electrode exhibits high sensitivity and a wide linear range to hydrogen peroxide.

The Amperometric Glucose Enzyme Electrode by Immobilized Glucose Oxidase in Glucose Oxidase/N-ethyl-Poly (4-vinyl)pyridine Multilayer

Multilayers of glucose oxidase(GOD)/N-ethyl-poly (4-vinyl) pyridine (EPVP) have been assembled on thiol self-assembled monolayers on gold electrode.This electrode can be used as an amperometric enzyme elcctrode for glucose. Fe (CN)63-/4- incorporated in EPVP layer acts as the electron mediator, the linear range was 0.1 to 6 mmol/L when the number of GOD layers was 5.

Enzyme-electrolytic degradation of dichloromethane: Efficiency, kinetics and mechanism

Enzymatic electrolysis cell(EEC)has advantages over microbial electrolysis cell(MEC)due to the needless of microbe inoculation and high-efficiency of enzymatic reaction.In this study,an EEC was first applied to achieve the effective degradation of halogenated organic pollutants and dichloromethane(CH2Cl2)was utilized as a model pollutant.The results indicate that the degradation efficiency of CH2Cl2 after 2 hr reaction in the EEC was almost100%,which was significantly higher than that with enzyme(51.1%)or current(19.0%).The current induced the continuous regeneration of reduced glutathione(GSH),thus CH2Cl2 was degraded under the catalysis of GSH-dependent dehalogenase through stepwise dechlorination,and successively formed monochloromethane(CH3Cl)and methane(CH4).The kinetic result shows that with a current of 15 mA,the maximum specific degradation rate of CH2Cl2(3.77×10-3 hr-1)was increased by 5.7 times.The optimum condition for CH2Cl2 dechlorination was also obtained with pH,current and temperature of 7.0,15 mA and 35°C,respectively.Importantly,this study helps to understand the behavior of enzymes and the fate of halogenated organic pollutants with EEC,providing a possible treatment technology for halogenated organic pollutants.

Cholesterol oxidase biosensor based on a glassy carbon electrode modified with Nafion and methyl viologen

Cholesterol oxidase biosensor has been constructed by using bovine serum albumin and glutaraldehyde as cross linker to immobilize cholesterol oxidase and cholesterol esterase on a glassy carbon electrode modified with Nafion and methyl viologen. The biosensor has been used to determine total cholesterol in blood. The linear range of the determination is 2.5×10to 1.0×10-4 mol/L. The detection limit is about 5.0×10mol/L. The response time is 12 s. This biosensor has the advantage of high selectivity, sensitivity and short response time.

Bioelectrochemical Response and Kinetics of Choline Oxidase Entrapped in Polyaniline-Polyacrylonitrile Composite Film

A novel choline oxidase electrode was constructed by entrapping choline oxidase into polyaniline polyacrylonitrile composite film. The enzyme film was prepared by in situ electropolyme rization of aniline into porous polyacrylonitrile coated platinum electrode in the presence of choline oxidase. The enzyme electrode exhibited sensitive and stable electrochemical response to choline. The kinetics analysis showed that the mass transport is partially rate limiting. The influences of pH, applied potential and temperature on the response of the enzyme electrode were also described.

A screen-printed, amperometric biosensor for the determination of organophosphorus pesticides in water samples

An amperometric biosensor based on screen-printed electrodes （SPEs） was developed for the determination of organophosphorus pesticides in water samples. The extent of acetylcholinesterase （AChE） deactivation was determined and quantified for pesticide concentrations in water samples. An enzyme immobilization adsorption procedure and polyacrylamide gel matrix polymerization were used for fabrication of the biosensor, with minimal losses in enzyme activity. The optimal conditions for enzyme catalytic reaction on the SPEs surfaces were acetylthiocholine chloride （ATChCl） concentration of 5 mmol/L, pH 7 and reaction time of 4 min. The detection limits for three organophosphorus pesticides （dichlorvos, monocrotophs and parathion） were in the range of 4 to 7 μg/L when an AChE amount of 0.1 U was used for immobilization.