AN ORIGINAL ELECTROENZYMATIC SYSTEM - FLAVIN REDUCTASE-RIBOFLAVIN FORTHE IMPROVEMENT OF DEHYDROGENASE-BASED BIOSENSORS - APPLICATION TO THE AMPEROMETRIC DETECTION OF LACTATE

The electropolymerization of a flavin reductase (Fre) - amphiphilic py rrole ammonium mixture previously adsorbed on the electrode surface pr ovides an efficient bioelectrode for the amperometric detection of NAD H and NADPH. The bioelectrode response was based on the oxidation at - 0.1 V vs. SCE of the enzymically generated dihydroriboflavin. The sens itivity and detection limit of the bioelectrode were 29 m AM(-1) cm(-2 ) and 0.2 mu M for NADH and 15.8 m AM(-1) cm(-2) and 0.4 mu M for NADP H. The coimmobilization of Fre and a lactate dehydrogenase leads to a dehydrogenase-based bioelectrode for the determination of lactate in t he presence of riboflavin and NAD(+). With laponite additives into the polypyrrole host matrix, the sensitivity and the detection limit of t he bioelectrode for lactate are 11.7 m AM(-1) cm(-2) and 1 mu M respec tively. Owing to the negative value of the applied potential for the o xidation of riboflavin, the response of the bienzyme electrode remains insensitive to interferents like ascorbate, urate and acetaminophen.