Extended–gate field effect transistor (EGFET) for carbaryl pesticide detection based on enzyme inhibition assay

Abstract

An extended – gate filed effect transistor (EGFET) is a device which can be applied to chemical sensing devices. In this study, EGFET was constructed by using an indium tin oxide (ITO) glass substrate. The small piece ITO with sensing area around 3x3 mm2 was used as carbaryl pesticide sensor based on enzyme inhibition assay. The prepared ITO-EGFET sensors were test with pH solutions to obtain sensitivity compared with commercial ion sensitive field effect transistor (ISFET). Preparation of ITO substrate for enzyme inhibition assay by dropped acetylcolinesterase enzyme at 0.5 Unit which were trapped in an agarose gel matrix onto substrates. This prepared ITO acts as extended gate sensing membrane for EGFET. The amounts of drop volume of enzyme were varied to obtain the highest signal for reaction with acetylcholine substrate. Cabaryl can inhibit enzyme function resulting in the decreasing signal of interaction between enzyme and acetylcholine substrate. This ITO-EGFET can be used to detect carbaryl in concentration rage 0.001 – 1 mM by using the ITO-EGFET without enzyme as control condition. This work shows possibility of ITO-EGFET for application in pesticide detection with an easy substrate preparation, low cost and can be applied in field used with others pesticides.