BIOELECTROCATALYZED AMPEROMETRIC TRANSDUCTION OF RECORDED OPTICAL SIGNALS USING MONOLAYER-MODIFIED AU-ELECTRODES

Three different methods to control by Light electron-transfer communic ation between redox-proteins and electrodes are discussed. The systems provide a means for the amperometric transduction and amplification o f recorded optical signals. A mixed monolayer of thiol pyridine/nitros piropyran immobilized onto a Au-electrode provides an active interface for controlling electrical communication between cytochrome c, cyt c, and the electrode by means of electrostatic interactions. The mixed m onolayer exhibits reversible photoisomerizable properties across the n itrospiropyran state, SP, and protonated nitromerocyanine, MRH(+). In the pyridine-SP monolayer state cyt c exhibits effective electrical co mmunication with the electrode due-to association of the redox-protein to the monolayer interface. Electron-transfer communication between c yt c and the electrode is blocked in the pyridine-MRH(+) monolayer sta te due to electrostatic repulsion of the redox-protein. The reversible ''ON-OFF'' light-regulated electrical communication of cyt c with the monolayer-electrode was coupled to cyt c electron-transfer mediated r eduction of O-2, in the presence of cytochrome c oxidase, COX, and oxi dation of lactate, in the presence of lactate dehydrogenase, LDH. Ligh t controlled electrical communication between electrodes and redox-enz yme monolayers associated with the electrodes was established by the a pplication of photoisomerizable diffusional electron mediators. The en zymes glucose oxidase, GOD, and glutathione reductase, GR, were photor egulated in the presence of photoisomerizable ferrocene-nitrospiropyra n, Fc-SP (3), and N,N'-bipyridiniumnitrospiropyran, V2+-SP, (6). Elect rical communication between the enzymes GOD and GR and the electrodes was effective in the presence of Fc-SP (3a) and V2+-SP (6a), respectiv ely, and electron-transfer was blocked in the presence of the electron mediators, Fc-MR (3b) and V2+-MR (6b), respectively. GOD modified by nitrospiropyran and assembled as monolayer on a Au-electrode provides an active interface for the photoregulated bioelectrocatalyzed oxidati on of glucose. The SP-GOD acts as an effective biocatalyst for oxidati on of the substrate and for the stimulation of an electrocatalytic ano dic current. Biocatalyzed oxidation of glucose is inhibited in the pre sence of MR-GOD. The photoregulated electrical interactions between th e various redox proteins and the electrode interfaces provide a means for the amperometric transduction and amperometric amplification of re corded optical signals. This is an essential fundamental feature for t he future development of bioelectronic devices.