Multi-enzyme electrode using hydrogen-ion-sensitive field-effect transistors

The feasibility of a multi-enzyme electrode for simultaneous determination of glucose and urea has been investigated. The multi-enzyme electrode consisted of three hydrogen-ion-sensitive field-effect transistors (
p
H-ISFET) with a platinum wire as a pseudoreference electrode. The first
p
H-ISFET had an immobilized glucose oxidase (GOD) membrane, the second one had an immobilized urease membrane, and the third one had no enzyme membrane. The enzymes were immobilized by a water-soluble photocrosslinkable polymer over the pH-ISFET's, and the enzyme-photocrosslinked polymer membranes thus obtained were further hardened by the reaction of bovine serum albumin (BSA) that has been added to the enzyme-polymer mixture with glutaraldehyde. The multi-enzyme electrode can be used for determining glucose and urea over the concentration range 50-1000 mg/l. The multi-enzyme electrode was shown to be potentially promising, although it requires some improvements for practical applications.