Immunosensor Based On Metal Nanomaterials Simulated Enzyme For Dectection Of Staphylococcus Aureus In Food

Staphylococcus aureus（S.aureus）is one of the common food-borne pathogens,which can easily cause food poisoning and pose a huge threat to human health.Therefore,convenient and rapid detection of S.aureus is essential for food safety.As a rapid and sensitive detection method,electrochemical immunosensor has been widely used in the detection of foodborne pathogens.In this paper,three different metal nanocomposites were prepared to construct electrochemical immunosensors to detect S.aureus in food with high sensitivity.The main research contents of this paper are as follows:1.Synthesis of gold-palladium-platinum trimetal functionalized multi-walled carbon nanotube nanocomposites mimic enzymes and its application in detection of S.aureusAn electrochemical immunosensor based on gold-palladium-platinum（AuPdPt）trimetallic nanoparticles functionalized multi-walled carbon nanotubes（MWCNTs）nanocomposites mimic enzymes was designed for the label-free detection of S.aureus in food.Firstly,the nanocomposite of MWCNTs-AuPdPt was prepared by an in situ growth method of loading AuPdPt trimetallic nanoparticles on the surface of MWCNTs.The nanocomposites featured good conductivity and superior catalytic performance for hydrogen peroxide.Then the anti-S.aureus antibody was functionalized on the surface of MWCNTs-AuPdPt modified electrode with good biocompatibility and high specific surface area to construct the immunosensing platform.After S.aureus was immobilized effectively captured by the immobilized antibody through immune reaction,the current-time curve was utilized to achieve rapid and sensitive detection of S.aureus.Under optimized conditions,the designed immunosensor could detect S.aureus in a linear range from 1.1×10²to 1.1×10⁷ CFU/m L with a low detection limit of 39 CFU/m L.The recoveries of S.aureus in dairy products were 91.2%～103.0%,and the relative standard deviations were 4.9%～7.5%.2.Electrochemical immunosensor based on octahedral Cu₂O-Au nanocomposites mimic enzyme for detection of S.aureusA label-free electrochemical immunosensor based on gold nanoparticles functionalized octahedral cuprous oxide（Cu₂O-Au）nanocomposites mimic enzymes was constructed for the detection of S.aureus.In this study,octahedral Cu₂O nanocrystals with uniform size were synthesized firstly,and then gold nanoparticles were assembled on the surface of Cu₂O nanocrystals by reduction reaction.The resulting octahedral Cu₂O-Au nanocomposites displayed large specific surface area,excellent electrocatalytic performance and good antibody loading capacity.Then the prepared Cu₂O-Au nanocomposites were employed to modify the electrode,and further functionalized by antibodies to achieve specific binding to S.aureus in samples.The immune complex formed on the surface of the electrode would hinder the substrate diffusion and electron transfer,resulting in changes of electrochemical signal,and finally realized the detection of S.aureus.Under the optimal conditions,the linear range of the prepared immunosensor was 2.4×10²～2.4×10⁷ CFU/m L,and the detection limit was 44 CFU/m L.Additionally,the electrochemical immunosensor had been successfully applied to the detection of S.aureus in actual samples.3.Synthesis of gold@platinum nanoparticles functionalized polystyrene acrylic spheres nanoprobe and its application in detection of S.aureusA sandwich electrochemical immunosensor based on gold@platinum nanoparticles functionalized polystyrene-acrylic sphere（PSA-Au@Pt）mimic enzyme nanoprobes was established for highly sensitive detection of S.aureus in food.Initially,the PSA-Au@Pt nanocomposites with high specific surface area were prepared by in-situ growth method.Then the nanospheres were functionalized with antibodies to construct mimic enzyme nanorecognition probes.The nanoprobes had excellent catalytic performance for the reduction of hydrogen peroxide,and can realize the amplification of the detection signal of the immunosensor.Meanwhile,gold nanoparticle functionalized graphene oxide（GO-Au NPs）was synthesized by self-assembly method.The GO-Au NPs modified electrode was utilized to construct the immunosensing platform,and the sandwich immunosensor was fabricated by combining with the PSA-Au@Pt-Ab mimic enzyme nanoprobes.The nanoprobes were used to catalyze hydrogen peroxide to generate electrical signals to realize highly sensitive detection of S.aureus.Under the optimized experimental conditions,the linear detection range of the designed electrochemical immunosensor for S.aureus was1.6×10²～1.6×10⁷ CFU/m L,and the detection limit was 25 CFU/m L.In addition,the constructed electrochemical immunosensor exhibited good repeatability,stability and specificity,and had been successfully used for the detection of S.aureus in actual samples.