CHARGE PROPAGATION THROUGH A REDOX POLYMER FILM CONTAINING ENZYMES - EFFECTS OF ENZYME LOADING, PH AND SUPPORTING ELECTROLYTE

Charge propagation through a redox polymer film (poly[(vinylpyridine)O s(bpy),Cl2+/3(+)]/polyamine) containing the enzymes glucose oxidase an d cellobiose oxidase was studied using potential-step chronocoulometry and cyclic voltammetry. The results were correlated with substrate re sponse measurements made using the electrodes as amperometric biosenso rs. To explore the effect of enzyme loading, a series of electrodes we re made with varying polymer-to-enzyme ratios but constant film thickn ess. The apparent charge-transport diffusion coefficient D-E drastical ly decreased with decreasing amount of polymer, i.e. increasing amount s of enzymes. Thus it is evident that values of D-E from pure redox po lymers cannot be used to describe charge propagation in enzyme electro des. The pH dependence of charge propagation is more pronounced for el ectrodes with the pure polymer than for electrodes with a mixture of e nzymes and polymer. For all electrodes D-E increased with decreasing p H below pH 5. A change of supporting electrolyte, giving a marked effe ct on the enzyme electrode response, does not alter charge propagation through the film. This shows that the effect is derived from the enzy me action only.