Study On Acetylcholinesterase Biosensor And Pesticide Detection Of Nanomaterials Modified Electrode

Organophosphorus pesticides are a group of highly toxic chemicals which have been widely used to protect crops from insects and improve the agricultural productivity.The presence of organophosphorus pesticides in our food,water supplies and environment,resulting from their extensive use,have raised severe public concerns regarding food safety,environment and human health.Therefore,the establishment of a method for sensitive and reliable detection of pesticides is of great significance for the protection of the environment and human health.Conventional detection methods including chromatography,high performance liquid chromatography,gas chromatography/mass spectrometry,liquid chromatography/mass spectrometry and spectroscopy.Although these methods possess adequate sensitivity and high selectivity for organophosphorus pesticides determination,most of them require high cost experimental instruments,tedious sample pretreatment and long analysis time,making them not suitable for on-site detection.As a result,it is very essential to develop a rapid,sensitive,simple and low-cost method for the detection of pesticides.Accordingly,electrochemical biosensors based on the inhibition of acetylcholinesterase have attracted more interests due to their rapid response,low cost,high sensitivity,simplicity and in situ detection.Recently,with the rapid development of nanotechnology,more and more nanomaterials have been used for fabricating electrochemical biosensors.The sensitivities and other properties of biosensors can be improved by the use of nanomaterials due to their unique physical and chemical properties.In this paper,we aims to develop sensitive and efficient electrochemical acetylcholinesterase biosensors for the detection of pesticides.The details and results are summarized as follows:(1)One-dimensional bimetallic Pd@Au core-shell nanorods(NRs)with uniform Au shell were synthesized and applied to construct a highly sensitive acetylcholinesterase(AChE)biosensor for the detection of organophosphate pesticides(OPs).The Pd@Au core-shell nanorods with excellent conductivity,pure contact surface and good biocompatibility can provide an extremely suitable area for the adhesion of AChE.Due to these characteristics,the constructed biosensor exhibits a superior performance.The biosensor was prepared via a simple procedure and its optimization studies were discussed.Under optimal conditions,the Michaelis-Menten constant of the fabricated enzyme electrode was calculated to be 0.207 mM.And the inhibition of paraoxon(as a model compound for OPs)is linearly proportional to its concentration in the range of 3.6 pM-100 nM,with the detection limit of 3.6 pM(calculated for 10% inhibition).The biosensor also possessed good reproducibility,stability and selectivity,and can be used in real samples analysis.(2)A kind of network structure composed of bimetallic Pd@Au nanowires with high aspect ratio has been developed and used to construct an AChE electrochemical biosensor to detect OPs.The networks not only can provide abundant sites to hold more enzyme,but also can fasten the loadings firmly by crisscrossed nanowires.In addition,the assembled networks could further supply multiple electron pathways then facilitate the transmission of electrons between the electrode and enzyme.The enzyme electrode based on the Pd@Au nanowires network exhibits an excellent current response to the substrate,and the Michaelis-Menten constant was calculated to be 190 ?M.Under optimal conditions,the developed biosensor could detect malathion in the range of 0.1 pM to 100 nM with a detection limit of 0.037 pM(S/N=3).The developed biosensor also has excellent reproducibility(RSD=1.78%)and stability.Besides,the biosensor could achieve a high accuracy in real samples analysis.(3)A series of nickel-cobalt metal borides have been prepared and the amorphous properties and elemental compositions of the samples were investigated by TEM,XRD and XPS.The effects of different composition and crystallinity on the electrochemical performance of the samples were investigated and the amorphous Co-2Ni-B was proved to have the best conductivity.In addition,the abundant defects in amorphous Co-2Ni-B may also provide more active sites for the immobilization of AChE,and also promotes the electrochemical oxidation of substrate.Under optimal conditions,the biosensor based on amorphous Co-2Ni-B showed good analytical performance for the determination of chlorpyrifos with a low limit of detection(3 pM)(calculated for 10% inhibition)and a wide linear range(3 pM-300 nM).The proposed biosensor also demonstrated high reproducibility and stability and can be used in real samples analysis.These results introduce a new class of promising materials as a robust platform for biosensor applications.