A novel acetylcholinesterase biosensor based on carboxylic graphene coated with silver nanoparticles for pesticide detection.

A novel acetylcholinesterase (AChE) biosensor based on Ag NPs, carboxylic graphene (CGR) and Nafion (NF) hybrid modified glass carbon electrode (GCE) has been successfully developed. Ag NPs-CGR-NF possessed predominant conductivity, catalysis and biocompatibility and provided a hydrophilic surface for AChE adhesion. Chitosan (CS) was used to immobilize AChE on the surface of Ag NPs-CGR-NF/GCE to keep the AChE activities. 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 133 μM, which was then oxidized to produce a detectable and fast response. Under optimum conditions, the biosensor detected chlorpyrifos and carbaryl at concentrations ranging from 1.0×10(-13) to 1×10(-8) M and from 1.0×10(-12) to 1×10(-8) M. The detection limits for chlorpyrifos and carbaryl were 5.3×10(-14) M and 5.45×10(-13) M, respectively. The developed biosensor exhibited good sensitivity, stability, reproducibility and low cost, thus providing a promising tool for analysis of enzyme inhibitors. This study could provide a simple and effective immobilization platform for meeting the demand of the effective immobilization enzyme on the electrode surface.