Oligosaccharide dehydrogenase-modified graphite electrodes for the amperometric determination of sugars in a flow injection system

Enzyme electrodes for the determination of sugars based on solid graphite electrodes modified with oligosaccharide dehydrogenase ''wired'' with an osmium-based one-electron (no proton) acceptor redox hydrogel were studied as sensors in a now injection system. The enzyme and a poly(1-vinylimidazole) (PVI) where every tenth mer is complexed with osmium (4,4'-dimethylbpy)(2)Cl, (denoted PVI(10)dmeOs) were cross-linked with poly(ethylene glycol) (diglycidyl) ether. The electrodes were active for L-arabinose, D-xylose, D-galactose, D-fructose, D-glucose, D-mannose, cellobiose, lactose, maltose, and maltooligosaccharides up to a degree of polymerization of 7. The highest relative response found was for glucose (100%) followed by maltose (40.6%) and lactose (40.6%). Fructose and isomaltotriose gave the lowest responses (<1%). Calibration curves for glucose were strictly linear in the range between 30 and 500 mu M with sensitivity and apparent Michaelis-Menten constant (K-m(app)) Of 23.0 +/- 1.4 mu A mM(-1)cm(-2) and 4.26 +/- 0.95 mM, respectively.