OVERALL CHARACTERIZATION OF ISFET-BASED GLUCOSE BIOSENSOR

Two types of glucose-sensitive enzyme field-effect transistor (ENFET) with glucose oxidase immobilized in polyacrylamide gel (PAAG) and by crosslinking with bovine serum albumin (BSA) have been investigated. These ENFETs with biomembranes demonstrate remarkable versatility in their properties and it is possible to fabricate sensors with the required characteristics. The highest sensitivity to glucose is obtained for an ENFET with a PAAG membrane; it reaches 150 mV/decade in 0.2 mM phosphate buffer, pH 7.3. Enzyme layers of different thicknesses have been produced and the sensor response time greatly depends on this thickness, ranging from about 5 min for thick (greater-than-or-equal-to 30 mum) to less than 10 s for thin (greater-than-or-equal-to 5 mum) BSA membranes. Conditions for ENFET-based glucose determination in blood have been examined and a procedure for a related glucose test proposed and verified. The effect of such sample characteristics as pH and concentration of working buffer, ionic strength, proteins and oxygen contents have been examined and taken into account.