Electron-transfer pathways in amperometric biosensors. Ferrocene-modified enzymes entrapped in conducting-polymer layers

Abstract

The development of non-leaking amperometric enzyme electrodes is a fundamental prerequisite for the application of biosensors. However, a contradiction between the accessibility of the enzyme's active site and the mobility of immobilized redox mediators has to be overcome. Entrapment of glucose oxidase with ferrocene derivatives attached to its outer surface via long and flexible spacer chains within conducting polymer films ( e.g. polypyrrole) is used to evaluate electron-transfer pathways between enzymes and electrode surfaces. It can be demonstrated that electron transfer occurs from the enzyme's active site via electron hopping between the enzyme-linked ferrocene derivatives and/or directly using the conducting polymer backbone as a molecular wire, presuming that the redox properties of the polypyrrole layer have not been destroyed by enzymatically produced H 2O 2.