Reconstitution of apo-glucose oxidase on nitrospiropyran and FAD mixed monolayers on gold electrodes: Photostimulation of bioelectrocatalytic features of the biocatalyst

N⁶-(2-Aminoethyl)-FAD is covalently linked to a thioctic acid monolayer associated with an Au-electrode. The surface coverage of the FAD units is 2.2 x 10^-11 mol cm^-2. Apo-glucose oxidase (apo-GOx) reconstituted onto the FAD monolayer, yields a bioelectrocatalytically active enzyme layer, GOx, at a surface coverage of 2 x 10^-12 mol cm^-2. In the presence of N-dimethyl- 2-aminoethyl ferrocene (I) as diffusional electron mediator, the enzyme electrode stimulates the bioelectrocatalyzed oxidation of glucose. A photoisomerizable nitrospiropyran-FAD mixed monolayer is assembled on an Au- electrode. The surface coverage of the FAD units is 2 x 10^-11 tool cm^{- 2}, and the molar ratio of the nitrospiropyran and FAD units is 3:4. Reconstitution of apo-GOx onto the FAD sites of the photoisomerizable nitrospiropyran-FAD mixed monolayer yields a photoswitchable enzyme electrode for the light-stimulated oxidation of glucose in the presence of I as electron mediator. The photoswitchable properties of the enzyme electrode originate from the electrostatic repulsion of the positively charged electron mediator from the electrode interface. The GOx-reconstituted-monolayer electrode represents an optobioelectronic assembly for the amplified amperometric transduction of photonic signals recorded by the photoisomerizable monolayer.