Abstract: This paper describes the use of functionalized multiwalled carbon nanotubes (FCNTs) based conductive polymer for designing acetylcholinesterase (AChE) biosensor. Transducers were obtained by directly dropping the sol-gel solution formed from FCNTs, chitosan (CHIT) and glutaraldehyde (GTA) on the surface of glassy carbon electrode (GCE). Acetylcholinesterase (AChE) as bio-recognizer was immobilized onto a CHIT membrane to recognize pesticides selectively. Before the detection, the CHIT enzyme membrane was quickly fixed on the surface of FCNTs-CHIT-GTA/GCE with O-ring, and thus a sensitive, fast and stable amperometric sensor for quantitative determination of organophosphates (OP) was developed. The electrochemical behavior of AChE-FCNTs-CHIT-GTA/GCE was studied and the results showed the FCNTs-CHIT-GTA promoted electron-transfer reactions at a low potential and catalyzed the electro-oxidation of thiocholine, thus increasing detection sensitivity. Based on the inhibition of OP on AChE activity, using dichlorvos as a model pesticide, the biosensor had good linearity in the concentration range 25－50 ng/L and 50－100 μg/L with a correlation coefficient of 0.9995 and 0.9991, respectively. The detection limit was 20 ng/L. The biosensor exhibited high sensitivity and good reproducibility and stability, and it was suitable for trace detection of OP pesticide residue.

Key words: biosensor, acetylcholinesterase, pesticide residue, functionalized multi-walled carbon nanotubes