Amplification of amperometric biosensor responses by electrochemical substrate recycling Part I. Theoretical treatment of the catechol-polyphenol oxidase system

The sensitivity of enzyme electrodes can be increased substantially by inco rporation of a substrate recycling scheme. One possible strategy to achieve this goal is based on amperometric enzyme electrodes involving during the transduction step an electrochemical recycling of enzyme substrate. In this kind of device, the shuttle analyte is not only measured once but is recon verted to be measured again leading to an amplification of the transduction signal. In this paper we present a theoretical analysis of this kind of de vice using the catechol-polyphenol oxidase model system immobilized as an e nzyme layer at the surface of a rotating-disk electrode. For low concentrat ions of substrate, which correspond to practical conditions, we derive anal ytical expressions for the response of such a sensor. On the basis of the m odel, we;are able to quantify the respective influence of mass transport, p artition coefficient, enzyme and electron transfer kinetics on the metrolog ical characteristics of the bioelectrode. This is especially relevant when optimizing biosensor construction. (C) 1999 Elsevier Science S.A. All right s reserved.