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

Three different methods to control by Light electron-transfer communication between redox-proteins and electrodes are discussed. The systems provide a means for the amperometric transduction and amplification of recorded optical signals. A mixed monolayer of thiol pyridine/nitrospiropyran 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 monolayer exhibits reversible photoisomerizable properties across the nitrospiropyran state, SP, and protonated nitromerocyanine, MRH(+). In the pyridine-SP monolayer state cyt c exhibits effective electrical communication with the electrode due-to association of the redox-protein to the monolayer interface. Electron-transfer communication between cyt c and the electrode is blocked in the pyridine-MRH(+) monolayer state 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 reduction of O-2, in the presence of cytochrome c oxidase, COX, and oxidation of lactate, in the presence of lactate dehydrogenase, LDH. Light controlled electrical communication between electrodes and redox-enzyme monolayers associated with the electrodes was established by the application of photoisomerizable diffusional electron mediators. The enzymes glucose oxidase, GOD, and glutathione reductase, GR, were photoregulated in the presence of photoisomerizable ferrocene-nitrospiropyran, Fc-SP (3), and N,N'-bipyridiniumnitrospiropyran, V2+-SP, (6). Electrical communication between the enzymes GOD and GR and the electrodes was effective in the presence of Fc-SP (3a) and V2+-SP (6a), respectively, 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 oxidation of glucose. The SP-GOD acts as an effective biocatalyst for oxidation of the substrate and for the stimulation of an electrocatalytic anodic current. Biocatalyzed oxidation of glucose is inhibited in the presence of MR-GOD. The photoregulated electrical interactions between the various redox proteins and the electrode interfaces provide a means for the amperometric transduction and amperometric amplification of recorded optical signals. This is an essential fundamental feature for the future development of bioelectronic devices.