Construction And Application Of MXene-based Acetylcholinesterase Electrochemical Biosensor

The long-term unreasonable use of organophosphorus pesticides（OP）has caused serious harm to human beings,animals and plants and the environment.Therefore,it is particularly important to establish a convenient,rapid,efficient and sensitive method for the detection of organophosphorus pesticides.With the advantages of fast response,portability and low cost,enzyme biosensor is widely used in detection,and can be used for rapid and sensitive detection of organophosphorus pesticides.Acetylcholinesterase（ACh E）is a biometric element for the detection of organophosphorus pesticides,and the key to the construction of ACh E biosensor is to firmly immobilize the enzyme on the surface of the working electrode and maintain the natural activity of the enzyme.Therefore,finding an ideal carrier for immobilization of ACh E is a top priority in the preparation and use of enzyme biosensors.MXene（Ti₃C₂T_x）is such an ideal immobilized enzyme material,which has the advantages of 2D layered structure similar to graphene,large specific surface area,excellent metal conductivity,biocompatibility and reducibility.Therefore,a series of ACh E electrochemical biosensors based on MXene were constructed and used to detect methyl parathion.The main research contents include:（1）A MXene-based ACh E electrochemical biosensor for the detection of organophosphorus pesticides was developed based on transition metal carbide MXene（Ti₃C₂T_x）nanowires and an organic material polymeric ionic liquid（PILs）.The MXene nanosheets modified by polymeric ionic liquids not only can effectively improve the oxidation resistance,but also MXene-PILs composites have high electrical conductivity,large specific surface area and good biocompatibility,so they are excellent carriers for immobilization of ACh E.The electrochemical behavior of ACh E/MXene-PILs/GCE was studied by cyclic voltammetry（CV）,AC impedance spectroscopy（EIS）and differential pulse voltammetry（DPV）.The parameters affecting the performance of ACh E biosensor were optimized,including p H of buffer,amount of enzyme,mass ratio of MXene-PILs composite,dosage and incubation time of pesticide.Under the optimum conditions,the linear detection range of ACh E/MXene-PILs/GCE for methyl parathion is 5.0×10^-4～10.0 ng/m L and the detection limit is 2.0×10^-4 ng/m L.It is worth mentioning that the sensor has excellent repeatability,long-term stability and good anti-interference.In addition,the developed biosensor has been applied to the detection of methyl parathion in pears and cucumbers with good analytical performance and satisfactory recovery.（2）Based on transition metal carbide MXene nanoparticles and an inorganic material gold nanoparticles,a second MXene-based ACh E electrochemical biosensor for the detection of organophosphorus pesticides was constructed.Gold nanoparticles were introduced into MXene/Au by MXene self-reduction of chloroauric acid.Compared with single-component MXene,the prepared ACh E composite has better electrical conductivity,retains the two-dimensional layered structure of MXene,has large specific surface area and good biocompatibility,and is an excellent carrier for immobilized ACh E.The electrochemical behavior of ACh E/MXene/Au/GCE was studied by cyclic voltammetry,AC impedance and differential pulse voltammetry.The parameters affecting the performance of ACh E biosensor were optimized,including p H of buffer and incubation time of pesticides.Under the optimum conditions,the linear detection range of ACh E/MXene/Au/GCE for methyl parathion is 10^-3～5.0 ng/m L and the detection limit is 4.0×10^-4 ng/m L.At the same time,the sensor has good long-term stability,excellent repeatability and anti-interference.In addition,the developed biosensor has been applied to the detection of methyl parathion in apples and tomatoes with good analytical performance and satisfactory recovery.