Oxygen insensitive glucose biosensor based on PQQ-dependent glucose dehydrogenase

Oxygen insensitive glucose biosensors based on PQQ-dependent glucose dehydr ogenase from Erwinia sp. 34-1 and carbon paste have been designed. Without special precautions the sensitivity of the biosensors with the immobilized enzyme was low. Several methods of enzyme immobilization were compared. The enzyme was immobilized in the polylysine-albumin gel and in a paste consis ting of water insoluble organic mediator, chemically modified carbon powder , fumed silica and binding material. Chemical modification of carbon with q uinonic water insoluble mediators and application of fumed silica in the pa ste considerably improves the reproducibility, stability and sensitivity of the biosensors. The anodic response current of the biosensor on glucose wa s recorded at 0-200 mV vs Ag/AgCl reference electrode. Sensitivity can be i ncreased more than 100 times in the presence of soluble mediators, such as phenazine methosulphate. Linearity of the biosensor can be extended by coat ing the enzymatic layer of the biosensor with a layer of the PVA emulsion. An advantage of the biosensor based on PQQ-glucose dehydrogenase is good li nearity at low glucose concentrations due to the elimination of oxygen infl uence.