ENZYME ELECTRODES BASED ON IONOMER FILMS COATED ON ELECTRODES

Experiments are described showing the feasibility of electrical commun ication between the enzyme glucose oxidase and a ferrocene redox media tor when both are incorporated into a (Nafion(R)) perfluorosulfonic ac id cation-exchange polymer film coated on an electrode. It was shown t hat Nafion(R) films can serve as a stable immobilization matrix that i s compatible with the conditions required for an enzyme catalyst to fu nction. An experimental strategy for the incorporation of a redox medi ator and the enzyme into the ion-exchange polymer film is described. T his involved casting mixed solutions of enzyme + mediator and Nafion(R ) onto an electrode surface. The ferrocene mediator was chemically mod ified so that it was strongly retained inside Nafion(R) through hydrop hobic interactions. In the presence of glucose, the mediator was able to transfer electrons from the redox center of the film-entrapped gluc ose oxidase to the electrode. Slow rates of charge transfer between th e enzyme and the electrode, because of the high affinity of the modifi ed mediator for the polymer, is a difficulty with this method at prese nt. An extension of the concepts demonstrated in this paper could lead to practical enzyme electrodes for analytical purposes.