Enzyme sensors based on an ion-sensitive field effect transistor coated with Langmuir-Blodgett membranes. Use of polyethyleneimine as a spacer for immobilizing .ALPHA.-chymotrypsin.

Abstract

A highly branched polyethyleneimine (PEI) was used as a spacer for immobilizing .alpha.-chymotrypsin on the surface of Langmuir-Blodgett (LB) membranes which were deposited on the gate of an ion-sensitive field effect transistor (ISFET). .alpha.-Chymotrypsin could be covalently immobilized through the glutaraldehyde-activated PEI on the LB membrane-coated ISFET. The .alpha.-chymotrypsin-modified ISFET showed a potentiometric response to the substrate at concentrations of more than 0.1 mM. Some performance characteristics of the sensor, such as pH response, response time, and long-term stability were examined.