Construction Of Electrochemical Immunosensor For Salmonella And Its Application In Milk Detection

There are frequent cases of food poisoning caused by pathogenic bacteria,most of which are caused by Salmonella infection.Salmonella not only poses a serious threat to public health,but also causes untold losses to the global food production and processing industries.Rapid and efficient pathogen detection technology is an effective strategy to prevent and alleviate these problems.However,the existing detection technologies,such as plate counting method,fluorescence immunoassay,etc.,cannot meet the current detection needs.Therefore,in order to solve the problems faced,the establishment of a rapid and sensitive method for detecting Salmonella in food is particularly important for the development of food industry in China.Electrochemical immunosensors have attracted the attention of many researchers in the field of food safety in recent years due to their fast response,high sensitivity,and easy operation.In this paper,two label-free electrochemical immunosensors for Salmonella detection were constructed based on graphene composites.The main work is as follows:（1）Ferric oxide-graphene（Fe₃O₄-graphene）composite was synthesized and used as a material for modified glassy carbon electrode（GCE）.Then,gold nanoparticles（Au NPs）were polymerized on the composite material by potentiostatic method,and the antibody was modified on the electrode by using Au-NH₂ bond to prepare an electrochemical immunosensor for detecting Salmonella.The electrode modification steps were characterized by scanning electron microscopy（SEM）and cyclic voltammetry（CV）,and the key parameters for sensor fabrication were optimized.Under the optimal experimental parameters,the performance of the constructed Salmonella immunesensor was analyzed by using the differential pulse method（DPV）,and verified in the actual milk samples.The results showed that the linear detection range of the sensor for Salmonella was 2.4×10²～2.4×10⁷ CFU m L^-1,the detection limit was 2.4×10² CFU m L^-1,and it exhibited good specificity,repeatability and stability.（2）The cobalt-iron-based metal-organic framework-graphene（Co Fe-MOFs-graphene）composite was synthesized and used as a material for modified GCE.Then,Au NPs were polymerized on the composite material by potentiostatic method,and the antibody was immobilized on the electrode using the Au-NH₂ bond formed between the Au NPs and the antibody to prepare an electrochemical immunosensor for rapid detection of Salmonella.The morphology of the composite and the construction steps of the sensor were characterized by SEM and CV,respectively,and the key parameters for sensor fabrication were optimized.The performance of the constructed Salmonella immunosensor was analyzed by DPV,and verified in actual milk samples.The results showed that under the optimal experimental parameters,the linear detection range of the sensor for Salmonella was 2.4×10²～2.4×10⁸ CFU m L^-1,and the detection limit was1.2×10² CFU m L^-1,and it exhibited good specificity,repeatability and stability.