Enzyme-octadecylamine Langmuir-Blodgett membranes for ENFET biosensors

Langmuir-Blodgett (LB) films containing butyrylcholinesterase (BuChE) are f abricated to realise an enzymatic field effect transistor (ENFET) for the d etection of organophosphorus pesticides in water. Trichlorfon as a common p esticide is examined in our work. The BuChE-immobilised LB films are formed by adsorbing the enzyme molecules onto a stearylamine monolayer using the electrostatic force. Enzyme/stearylamine mixed LB films are immobilized ont o a pH-ISFET surface and treated by glutaraldehyde vapour to improve the LB film's stability. The ENFET thus obtained worked as a potentiometric biose nsor for trichlorfon detection on the basis of enzyme inhibition. The detec tion limit for trichlorfon can reach 10(-7) M (26 ppb). The surface charact eristics of BuChE/stearylamine LB films obtained under various conditions o f the dipping surface pressures are analysed qualitatively by atomic force microscopy (AFM) and analysed quantitatively by FTIR spectroscopy. (C) 2000 Elsevier Science B.V. All rights reserved.