HYDROGEN-PEROXIDE AND BETA-NICOTINAMIDE ADENINE-DINUCLEOTIDE SENSING AMPEROMETRIC ELECTRODES BASED ON ELECTRICAL CONNECTION OF HORSERADISH-PEROXIDASE REDOX CENTERS TO ELECTRODES THROUGH A 3-DIMENSIONAL ELECTRON RELAYING POLYMER NETWORK

Hydrogen peroxide is efficiently electroreduced at an electrode modified with a hydrophilic, permeable film of horseradish peroxidase (HRP) covalently bound to a 3-dimensional epoxy network having polyvinyl pyridine (PVP)-complexed [Os(bpy)2Cl]3+/2+ redox centers. The sensitivity of the resulting H2O2 cathode at 0.0 V (SCE) is 1 A cm-2 M-1. Its current increases linearly with H2O2 concentration in the 1 X 10(-7)-2 X 10(-4) M range. Related NAD(P)H cathodes are based on stoichlometric homogeneous reduction of O2 to H2O2 by NADH or NAD(P)H. The reduction Involves two known steps. In the first step, NAD(P)H transfers two electrons and a proton to a dissolved quinoid. The quinoids are typically derived of phenazines; however phenothiazine and phenoxazine derivatives are also useful. In the second step, two electrons and a proton are transferred from the reduced quinold to O2. This reaction produces H2O2 and the original quinoid. Because the two reactions are quantitative, the sensitivity and the linear range of the resulting NADH and NADPH electrodes are identical with those of the H2O2 electrode, 1 A cm-2 M-1 and 1 X 10(-7)-2 X 10(-4) M, respectively.