AMPEROMETRIC THIN-FILM BIOSENSORS BASED ON GLUCOSE-DEHYDROGENASE AND TOLUIDINE-BLUE-O AS CATALYST FOR NADH ELECTROOXIDATION

Amperometric glucose sensors were constructed based on solid graphite electrodes, surface-modified with NAD(+) dependent glucose dehydrogena se (GDH), Toluidine Blue O (TBO), and protective ionic polymers. The e lectrocatalytic oxidation of NADH was evaluated from cyclic voltammetr y with TBO dissolved, adsorbed, and electrostatically or covalently bo und to polymers. The NADH and glucose sensors constructed were investi gated and operated at 0 mV vs. Ag/AgCl using single potential step chr onoamperometry. The operational stability of the glucose sensors was l imited by leakage of NAD(+). A glucose sensitivity much higher than ca rbon paste electrode was found. A sensitivity as high as 25 mu A cm(-2 ) mM(-1) was achieved.