AbstractThe electrocatalytic oxidation of nicotinamide adenine dinucleotide (NADH) by two redox polymers was evaluated from steady‐state measurements 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 styrene polymer incorporating positive charges through quaternary amines and Toluidine Blue 0 (TBO) moieties (ST) and a branched polyethylenimine with part of its primary amine groups loaded with TBO (PE). The catalytic efficiencyjudged from the maximum NADH sensitivity for the PE polymer was estimated to be 230 μa cm.−2mM−1at a coverage of 40 μgcm−2and for the ST polymer 300 μAcm−2cmM−1at about 100 μg cm−2. Reagentless biosensors sensingD‐glucose andL‐malate were constructed from bulk modified carbon paste containing the PE redox polymer, NAD+, polyethylenimine (PEI) andD‐glucose dehydrogenase orL‐malate dehydrogenase. TheD‐glucose andL‐malate sensors were characterized in a flow injection system by apparentj′max−andK′M‐values of 230 μA cm−2and 62mM and 3.3 μAcm−2and 1.7mM, respectively. It was shown for glucose dehydrogenase that the presence of PEI in the paste in addition to the PE polymer, drastically improved the enz
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