Oxygen insensitive glucose biosensor based on PQQ-dependent glucose dehydrogenase

Oxygen insensitive glucose biosensors based on PQQ-dependent glucose dehydrogenase 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 consisting of water insoluble organic mediator, chemically modified carbon powder, fumed silica and binding material. Chemical modification of carbon with quinonic water insoluble mediators and application of fumed silica in the paste considerably improves the reproducibility, stability and sensitivity of the biosensors. The anodic response current of the biosensor on glucose was recorded at 0-200 mV vs Ag/AgCl reference electrode. Sensitivity can be increased more than 100 times in the presence of soluble mediators, such as phenazine methosulphate. Linearity of the biosensor can be extended by coating 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 linearity at low glucose concentrations due to the elimination of oxygen influence.