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One pot fabrication of graphene-bimetallic nanoparticles-based acetylcholinesterase electrochemical biosensor with ultralow detection limit toward methyl parathion

A one-step method was proposed to prepare graphene-bimetallic nanoparticles (NPs)-based acetylcholinesterase (AChE) biosensor for the detection of organophosphorus pesticides (OPs). Gold NPs (AuNPs) and silver NPs (AgNPs) were chosen as the bimetallic NPs, prepared by chemical reduction method and analyzed by transmission electron microscope. The graphene-polydopamine (RGO-PDA) was obtained by reducing graphene oxide (GO) with dopamine. The biosensor denoted as GCE/RGO-PDA-AuNPs-AgNPs-AChE-CS was fabricated by casting a mixture of RGO-PDA, AuNPs, AgNPs, AChE and chitason (CS) on the surface of glass carbon electrode (GCE). The response of the target electrode was significantly enhanced in the presence of nanostructured silver compared to that without AgNPs. The optimized amount of AChE in the electrode was 1.0 U. The optimized pH value of the buffer solution was 7.4. The proposed biosensor had a Michaelis–Menten constant ( K m ) of 479.659 μM. The optimized incubation time was determined to be 10 min. Under optimal conditions, the linear detection range of methyl parathion for the biosensor was 0.076–3040 nM, and the limit of detection (LOD) was as low as 9.1pM. The biosensor had strong anti-interference performance, acceptable stability and good reproducibility. Considering the simplicity of preparation method, the electrochemical enzyme biosensor demonstrated in this study has good potential applications for the detection of real organophosphorus pesticides and even nerve agents.