Enzyme containing redox polymer networks for biosensors or biofuel cells: a photochemical approach

Abstract

A photochemical approach to the generation of (microstructured) redox hydrogels with incorporated enzymes is presented and evaluated with respect to its potential in biosensor and biofuel cell applications. For this, poly(dimethylacrylamide) polymers containing both electroactive ferrocene moieties and photoreactive benzophenone groups are synthesized and deposited as thin films on electrode surfaces. Upon short irradiation with UV light, the polymer layer cross links and becomes firmly adhered to the glassy carbon electrodes. If glucose oxidase is mixed into the polymer solution prior to coating, then glucose-oxidizing electrodes with very high catalytic current responses are obtained. The influence of multivalent ions and proteins on the performance of the electrocatalytic films is studied. It is found that the interaction between bivalent HPO(4)(2-) and the oxidized redox moieties can shorten the lifetime of the redox electrodes significantly whereas the same electrodes are quite stable in the presence of monovalent ions and the reduced form of the mediator. Coating a thin, covalently attached poly(dimethylacrylamide) protective layer onto the redox polymer networks can greatly reduce the adsorption of proteins onto the surfaces and improve the long-term stability of the electrodes in physiological environments. Because the adsorption of proteins onto unprotected surfaces is one of the major causes of bioelectrode failure, this aspect is expected to contribute to the design of more biostable sensors and fuel cells.