ENZYME ELECTRODES BASED ON IONOMER FILMS COATED ON ELECTRODES

Experiments are described showing the feasibility of electrical communication between the enzyme glucose oxidase and a ferrocene redox mediator when both are incorporated into a (Nafion(R)) perfluorosulfonic acid cation-exchange polymer film coated on an electrode. It was shown that Nafion(R) films can serve as a stable immobilization matrix that is compatible with the conditions required for an enzyme catalyst to function. An experimental strategy for the incorporation of a redox mediator and the enzyme into the ion-exchange polymer film is described. This involved casting mixed solutions of enzyme + mediator and Nafion(R) onto an electrode surface. The ferrocene mediator was chemically modified so that it was strongly retained inside Nafion(R) through hydrophobic interactions. In the presence of glucose, the mediator was able to transfer electrons from the redox center of the film-entrapped glucose oxidase to the electrode. Slow rates of charge transfer between the enzyme and the electrode, because of the high affinity of the modified mediator for the polymer, is a difficulty with this method at present. An extension of the concepts demonstrated in this paper could lead to practical enzyme electrodes for analytical purposes.