Amperometric Acetylcholinesterase Biosensor Based on O-Carboxymethyl Chitosan-Gold Nanoparticle Nanocomposite by In-Situ Synthesis Method

The nanocomposite comprised of O-carboxymethyl chitosan (CMCS) and gold nanoparticles (AuNPs) is successfully prepared by in-situ synthesis method. The synthesized nanocomposite has been characterized by scanning electron microscopy images. The CMCS-AuNPs nanocomposite is first modified onto the glassy carbon electrode (GCE), then the surface carboxyl group is activated by N-hydroxysuccinimide and 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride. Finally, the acetylcholinesterase (AChE) is immobilized onto the GCE to construct a novel AChE biosensor for the detection of pesticides. Because the nanocomposite was able to inherit the properties of the AuNPs and CMCS, the resulting surface provided a favorable microenvironment for AChE biosensor fabrication and maintained the bioactivity of AChE for screening of pesticide exposure. Based on the inhibition of pesticides on AChE activity using chlorpyrifos as the model compound, the results showed that the inhibition of chlorpyrifos is proportional to its concentration ranging from 0.1 to 20 μg/L and 20 to 100 μg/L, with a detection limit of 0.07 μg/L (S/N=3). The developed biosensor exhibited good reproducibility, acceptable stability, fast response, and low detection limit, thus providing a new promising tool for the rapid detection of pesticides.