GLUCOSE SENSOR WITH AN ENZYME-ENTRAPPED S ILICA-GEL FILM PREPARED BY A SOL-GEL METHOD

A sol-gel silicate-based biosensor for glucose was made up by dip coat ing the end surface of a platinum-disk electrode in a sol solution com prising 50 mu l of tetramethyl orthosilicate (TMOS) and 100 mu l of 10 mM phosphate buffer (pH 5.5) containing 1.5 mg glucose oxidase (GOD), followed by drying for two days under ambient conditions. Although th e prepared sensor responded rapidly (ca. 15 s) at 0.6 V (vs. Ag/AgCl), the presence of an electroactive species, such as ascorbate, interfer ed with the measurement of glucose. Subsequently, another sol-gel bios ensor was constructed from a gel solution comprising TMOS, GOD, and pe roxidase by a similar sol-gel procedure, to improve the selectivity of the sensor. This sensor responded rapidly (ca. 20 similar to 30 s) to glucose at 0 V in the presence of a mediator, such as hexacyanoferrat e(II) or ferrocenecarbonate, without any interference from ascorbate b elow 0.2 mM. A plot of the current response vs. the glucose concentrat ion gave a straight line over the 1 X 10(-5)similar to 2 X 10(-3) M ra nge. In addition, this sensor was well suited as a detector of a flow- injection system. Reliable results were obtained in the assays of gluc ose in controlled human sera.