Electrocatalytic oxidation of NADH at polyadenylic acid modified graphite electrodes

The electrochemical oxidation of 5'-polyadenylic acid (poly-A) on graphite electrodes has been studied by cyclic voltammetry. ne oxidation of poly-A in neutral and alkaline solutions gives rise to redox-active products strongly adsorbed on the electrode surface, which exhibit catalytic activity toward NADH oxidation. The amount and properties of the catalyst are remarkably influenced by the pH of the oxidation medium. Depending on the conditions of catalyst formation, it is possible to reduce the overpotential for NADH oxidation by 300 mV Amperometric detection of NADH using electrodes modified from different media were evaluated and compared. Electrodes modified from 0.1 M NaOH solutions containing the polynucleotide allow carrying out the amperometric detection of NADH at 50 mV (vs. Ag/AgCl), at pH 9, within a wide concentration range, 2.5 x 10(-8) - 1 X 10(-4) M, and with a detection limit of 1.1 x 10(-8) M. These electrodes also exhibit very good stability and reproducibility.