Reagentless biosensors based on self-deposited redox polyelectrolyte-oxidoreductases architectures

Reagentless fructose and alcohol biosensors have been produced with a versa tile enzyme immobilisation technique which mimics natural interactions and flexibility of living systems. The electrode architecture is built up on el ectrostatic interactions by the sequential adsorption of redox polyelectrol ytes and redox enzymes giving rise to the efficient transformation of subst rate fluxes into electrocatalytic currents. All investigated multilayer str uctures were self-deposited on 3-mercapto-1-propanesulfonic acid monolayers self-assembled on gold electrodes. Fructose dehydrogenase, horseradish per oxidase (HRP) and the couple HRP-alcohol oxidase were electrochemically con nected with a cationic poly[(vinylpyridine)Os(bpy)(2)Cl] redox polymer (RP) interface in a layer-by-layer self-deposited architecture. The dependence of the distance on the electrochemical response of this interface was also studied showing a clear decrease in the Faradaic current when the distance to the electrode surface was increased. The sensitivities obtained for each biosensor were 19.3, 58.1 and 10.6 mA M-1 cm(-1) for fructose, H2O2 and me thanol, respectively. The sensitivity values can be easily controlled by a rational deposition and manipulation of the charge in the catalytic layers. The electrostatic assembly of the electrochemical interface and the cataly tic layers resulted in integrated biochemical systems in which mass transfe r diffusion and heterogeneous catalytic and electron transfer steps are eff iciently coupled and can be easily manipulated. (C) 2000 Elsevier Science S .A. All rights reserved.