Activity of free and immobilized glucose oxidase: an electrochemical study.

The activity of free and immobilized glucose oxidase was determined using a sandwich type thin-layer electrochemical cell. The thin-layer cell consisted of a gold electrode deposited on a glass microscope slide, 165 microns thick Teflon TFE spacers, and a glass cover. Enzyme activity was determined by using cyclic voltammetry to measure the amount of hydrogen peroxide produced in the glucose oxidase catalyzed redox reaction between glucose and oxygen in the thin-layer cell. The specific activity of 13.4 nM glucose oxidase in 0.2 M aqueous sodium phosphate, pH 5.2 at room temperature, was calculated to be 4.34 U/mg GOx. Under the same experimental conditions, qualitative detection of the activity of glucose oxidase covalently immobilized to a thin radiofrequency plasma modified poly(etherurethaneurea) film was demonstrated.