Abstract
Bioelectrochemical devices are expected to function as biosensors and biocatalytic electrode in biomedical field including artificial organs and cells. In order to design those devices, we have studied electron transfer between the electrode and redox protein such as cytochrome c. Horse heart cytochrome c was immobilized on In2O3/SnO2electrode whose surface was coated with poly-glutamic acid derivatives. That polymer forms a gelated polyanion membrane in the aqueous solution. Thereby the redox reaction of cytochrome c could be successfully controlled.
Since several electrochemical properties of cytochrome c-immobilized electrode were closely dependent on ionic strength, it was suggested that the interaction of cytochrome c molecules with polyanion gel was supported by electrostatically attractive force. In this study, the coupling reaction of the cytochrome c-immobilized electrode with oxidoreductase, e. g. cytochrome oxidase and diaphorase were also examined.
Reduction current of cytochrome oxidase on cytochrome c-immobilized ITO electrode was measured in-0.2Vvs.SCE. The current corresponds to continuous reduction of oxygen in solution and cytochrome c molecules are rapidly reduced at that potential. It was indicated that apparent cathodic currents of cytochrome c decreased with ionic strength, however that cathodic current per molecule increased with ionic strength. Moreover the electron transfer activity of an immobilized cytochrome c molecule closely correlated to apparent diffusion constant of the electron (Dapp). On the other hand immobilized cytochrome c could also react with diaphorase which is classified to NADH dehydrogenase. As the redox reaction of immobilized cytochrome c could be regulated by the electrode potential, it is thought that electrochemical NADH oxidation result from mediation of immobilized cytochrome c.
