Acetylcholinesterase biosensor based on SnO2 nanoparticles-carboxylic graphene-nafion modified electrode for detection of pesticides.

A sensitive amperometric acetylcholinesterase (AChE) biosensor, based on SnO2 nanoparticles (SnO2 NPs), carboxylic graphene (CGR) and nafion (NF) modified glassy carbon electrode (GCE) for the detection of methyl parathion and carbofuran has been developed. The nanocomposites of SnO2 NPs and CGR was synthesized and characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR), respectively. Chitosan (CS) was used to immobilize AChE on SnO2 NPs-CGR-NF/GCE and to improve electronic transmission between AChE and SnO2 NPs-CGR-NF/GCE. NF was used as the protective membrane for the AChE biosensor. The SnO2 NPs-CGR-NF nanocomposites with excellent conductivity, catalysis and biocompatibility offered an extremely hydrophilic surface for AChE adhesion. The AChE biosensor showed favorable affinity to acetylthiocholine chloride (ATCl) and could catalyze the hydrolysis of ATCl with an apparent Michaelis-Menten constant value of 131 μM. The biosensor detected methyl parathion in the linear range from 10(-13) to 10(-10)M and from 10(-10) to 10(-8)M. The biosensor detected carbofuran in the linear range from 10(-12) to 10(-10)M and from 10(-10) to 10(-8)M. The detection limits of methyl parathion and carbofuran were 5 × 10(-14)M and 5 × 10(-13)M, respectively. The biosensor exhibited low applied potential, high sensitivity and acceptable stability, thus providing a promising tool for analysis of pesticides.