Bioelectrocatalytical glucose oxidation with phenoxazine modified glucose oxidase

Abstract

Phenoxazine mediator bearing a carboxylate group was covalently attached to glucose oxidase by a carbodiimide coupling procedure. Spectral measurements showed that about 20 molecules of the mediator were covalently bonded to enzyme. The modified enzyme saved initial activity. Quenching of tryptophan fluorescence confirmed that mediator was covalently attached to glucose oxidase. The attached mediator mediated efficiently the electron transfer during reoxidation of the modified glucose oxidase in the presence of glucose. It was suggested that mediated electron transfer proceeded by intra- and intermolecular mechanism. Biosensor based on the modified glucose oxidase with phenoxazine was developed and bioelectrocatalytical properties determined. The electrode was poised at 0.4 V vs. SCE and linear response was obtained over the range of 3–8 mM glucose.