A POLY(AMPHIPHILIC PYRROLE)-FLAVIN REDUCTASE ELECTRODE FOR AMPEROMETRIC DETERMINATION OF FLAVINS

The electropolymerization of a flavin reductase-amphiphilic pyrrole am monium mixture previously adsorbed on the electrode surface provides t he efficient entrapment of the enzyme in a functionalized polypyrrole film, The enzyme film was characterized and applied to the detection o f several flavins and pyridine nucleotides, The response of the bioele ctrode was based on the amperometric oxidation, at -0.1 V vs SCE, of t he enzymically generated dihydroflavins in the presence of reduced pyr idine nucleotides. The highest sensitivities and detection limits were 668 mA M-1 cm(-2) and 4 nM for riboflavin, 179 mA M-1 cm(-2) and 20 n M for flavin mononucleotide, and 107 mA M-1 cm(-2) and 40 nM for flavi n adenine dinucleotide. Direct electrochemical measurements at -0.65 V and electroenzymatic measurements at -0.1 V of riboflavin, carried ou t with these bioelectrodes, show that an amplification phenomenon occu rs, due to an electrochemical recycling reaction of enzyme substrate, A nonamplified response to reduced pyridine nucleotides was also obtai ned in the presence of 0.1 mM riboflavin. The sensitivity and detectio n limit of the bioelectrode are 19.6 mA M-1 cm(-2) and 0.2 mu M for NA DH and 11.2 mA M-1 cm(-2) and 0.5 mu M for NADPH.