Electropolymerized Flavin Adenine Dinucleotide as an Advanced NADH Transducer

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Abstract
Electropolymerizing the prosthetic group (flavin adenine dinucleotide, FAD) responsible in the active sites of dehydrogenases for NAD+|NADH regeneration, we succeeded in mimicking enzyme activity. Poly(FAD) characterized by an additional polymer-type redox reaction has been discovered as a highly effective electrocatalyst for NADH oxidation: operating at the lowest potentials reported for NADH transducers (0.00 V, pH 7.4), poly(FAD) is characterized by the electrochemical rate constant of 1.8 ± 0.6 × 10-3 cm s-1, which is at the level of the NADH mass-transfer constant. Flow injection analysis of NADH with the poly(FAD)-modified wall-jet electrode as a detector has been characterized by a linear calibration range prolonged down to 5 × 10-7 M and a sensitivity of 0.08 A M-1 cm-2, which taking into account the dispersion coefficient (∼3), is at the diffusion-limiting value. In contrast to the low molecular weight mediators able to exhibit similar electrocatalytic properties, poly(FAD)-modified electrodes are characterized by the dramatically improved stability and, thus, can be considered as the most advantageous NADH transducers for analytical chemistry.