REDOX POLYMERS FOR ELECTROCATALYTIC OXIDATION OF NADH - CATIONIC STYRENE AND ETHYLENIMINE POLYMERS

The electrocatalytic oxidation of nicotinamide adenine dinucleotide (N ADH) by two redox polymers was evaluated from steady-state measurement s at drop-coated solid graphite electrodes in 0.25 M phosphate buffer, pH 7.0, at 0 mV (vs. SCE). The redox polymers studied comprised a sty rene polymer incorporating positive charges through quaternary amines and Toluidine Blue O (TBO) moieties (ST) and a branched polyethylenimi ne with part of its primary amine groups loaded with TBO (PE). The cat alytic efficiency judged from the maximum NADH sensitivity for the PE polymer was estimated to be 230 mu A cm(-2) mM(-1) at a coverage of 40 mu g cm(-2) and for the ST polymer 300 mu A cm(-2) mM(-1) at about 10 0 mu g cm(-2). Reagentless biosensors sensing D-glucose and L-malate w ere constructed from bulk modified carbon paste containing the PE redo x polymer, NAD(+), polyethylenimine (PEI) and D-glucose dehydrogenase or L-malate dehydrogenase. The D-glucose and L-malate sensors were cha racterized in a flow injection system by apparent j'(max) and K'(M)-va lues of 230 mu A cm(-2) and 62 mM and 3.3 mu A cm(-2) and 1.7 mM, resp ectively. It was shown for glucose dehydrogenase that the presence of PEI in the paste in addition to the PE polymer, drastically improved t he enzymatic conversion of glucose to gluconic acid.