REAGENTLESS AMPEROMETRIC GLUCOSE-DEHYDROGENASE BIOSENSOR BASED ON ELECTROCATALYTIC OXIDATION OF NADH BY OSMIUM PHENANTHROLINEDIONE MEDIATOR

The mediator Os(4,4'-dimethyl, 2,2'-bipyridine)(2)(1,10-phenanthroline -5,6-dione) was used for the catalytic oxidation and recycling of NADH , The mediator, with a redox potential of almost 0 V versus Ag/AgCl, s hows clear electrocatalysis of NADH at 0.1 V versus Ag/AgCl at pH 6.0, Carbon paste electrodes modified with the mediator show a clear elect rocatalytic wave reaching limiting current densities at 0.15 V versus Ag/AgCl of the order of 140 mu A cm(-2) l mmol(-1) NADH, Reagentless d ehydrogenase carbon paste amperometric electrodes for glucose were dev eloped, mixing the mediator, glucose dehydrogenase and NAD(+) in the p aste, These electrodes were optimized with respect to amounts of enzym e, mediator and NAD(+) and were studied with a variety of electrochemi cal techniques, The results suggest that the response is limited by th e enzymic step of the reduction of NAD(+) or the oxidation of the subs trate, The glucose electrodes show maximum current densities of > 0.5 mA cm(-2) and very good operational stability in continuous operation; under dry storage conditions their lifetime exceeded 1 month.