A reagentless glucose biosensor based on glucose oxidase entrapped into osmium-complex modified polypyrrole films

A reagentless glucose biosensor based on glucose oxidase entrapped within an osmium-complex (Os-complex) modified conducting polymer has been developed. Optimisation of the electrochemical-induced deposition of the conducting-polymer film has been achieved by variation of key parameters, such as the concentration of glucose oxidase and the concentration of pyrrole. In order to unequivocally reveal the electron-transfer from the enzyme via the polymer-bound Os-complexes to the electrode surface, glassy-carbon electrodes have been used to prevent co-oxidation of enzymatically generated H2O2 in the presence of molecular oxygen. In addition, a significant enhancement of the glucose-dependent current could be obtained by increasing the hydrophilicity of the polymer film which was attained by changing the counter anion of the Os-complexes and introduction of carboxylic acid side chains at the polypyrrole backbone. The improved swelling of the polymer in aqueous solution leads to an improved substrate transport within the polymer film and faster electron-transfer kinetics due to a higher flexibility of the polymer backbone.