Supramolecular multilayer structures of wired redox enzyme electrodes

Abstract

Supramolecular multilayer structures comprised of glucose oxidase (GOx), and Os complex derivatised poly(allylamine) (PAH-Os) have been built by alternate layer-by-layer (LBL) electrostatic adsorption in a self-assembly process. The resulting modified electrodes with integrated mediator were tested as reagentless glucose biosensors. The enzyme kinetic parameters and the surface concentration of “wired” enzyme Γ_E have been obtained by analysis of the catalytic current dependence on glucose concentrations for the ping-pong mechanism of glucose oxidation. An average osmium volume concentration was estimated by integration of the redox charge in the absence of glucose and the ellipsometric thickness. The total enzyme surface concentration was measured with a quartz crystal microbalance (QCM) during each adsoption step and the fraction of “wired” enzyme and the bimolecular rate constant for FADH₂ oxidation by the redox polymer for the different multilayers. The catalytic current increases with the number of LBL layers because the increase in the enzyme loading while the efficiency of enzyme FADH₂ oxidation by the Os redox polymer, except for the first dipping cycle remains almost constant at about 2 × 10⁴ M⁻¹ s⁻¹.