No abstract

A novel glucose biosensor has been prepared by deposition of a mixture containing glucose oxidase dissolved in water and Nafion dissolved in methanol at the surface of a platinum disk electrode. Glucuse concentration is evaluated by measuring the amperometric current corresponding to hydrogen peroxide electrooxidation at 0.7 iJ vs. SCE. The addition of glucose oxidase to Nafion resulted in a Nafion-glucose oxidase film that was more permeable to anionic species than Nafion alone. The calibration curve for glucose is linear from 5 p M u p to about 10 mM. Tn oxygen-saturated solution, the linear range extended to 15 mM. The optimum pH for the assay was found to be 5.5. The enzyme is not stabilized against temperature deactivation when it is immobilized in Nafion. The Pt/Nafion-glucose oxidase electrodes showed good stability when stored dry at room temperature with 80% of the initial response retained after 250 days.

No abstract

No abstract

This article reports the characterization of the biochemical behavior of glucose oxidase entrapped in polypyrrole. The immobilization of glucose oxidase in a polypyrrole film was performed by entrapment during the electropolymerization of pyrrole at a platinum electrode poised at 0.65 V vs. SCE in aqueous solution in a one-compartment electrochemical cell. Thin films of polypyrrole (0.11 microm) were obtained and the entrapped enzyme obeyed Michaelis kinetics, indicating no diffusional constraints of the substrate. Our results indicate that the entrapped glucose oxidase is more resistant to denaturation conditions such as alkaline pH and temperature (50 and 60 degrees C) than the soluble form of the enzyme. The autoinactivation constant for the entrapped enzyme was also determined in presence of 0.25M of glucose and was 6.19 x 10(-4) min(-1), i.e., corresponding to a half-life value of 20 h. The results reported here show clearly that polypyrrole matrix has a strong stabilizing effect on the stucture and on the activity of glucose oxidase.