Reconstitution of Apo-Glucose Oxidase on Nitrospiropyran and FAD Mixed Monolayers on Gold Electrodes:  Photostimulation of Bioelectrocatalytic Features of the Biocatalyst

Abstract

N 6 -(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 × 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 × 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 × 10 - 11 mol 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.