Antibacterial Mechanism Of Fe₃C/N-C Synthesized By Electrochemical Method Against Salmonella And Staphylococcus Aureus

Food pollution caused by pathogenic bacteria has brought serious safety risks.For example,chestnuts are susceptible to Salmonella contamination during their collection,transportation and storage.While meats and milk products are usually found contaminated by Staphylococcus aureus.Therefore,it is important to find new materials both effective and cheap to control foodborne pathogens.Nanomaterials are special materials with large molecular weight and widely used in the field of bioengineering at present.In this paper,Fe3C/N-C nanomaterials with good water solubility were synthesized by electrochemical method at room temperature using the mixed solution of ferrous sulfate and histidine as electrolyte,platinum plate and carbon rod as electrodes.The characters of Fe₃C/N-C in supernatant of electrolyte were studied by means of corresponding characterization methods,including high resolution transmission electron microscopy?HRTEM?,X-ray photoelectron spectroscopy?XPS?,X-ray diffraction?XRD?and Fourier transform infrared spectroscopy?FTIR?.In addition,the inhibitory effects of Fe₃C/N-C solution on the growth of Salmonella and Staphylococcus aureus were investigated by the methods of paper diffusion and plate culture.The survival status of Salmonella and S.aureus cells after Fe3C/N-C solution treatment was identified by blue-fluorescent dye staining.The damage degree of Fe₃C/N-C to salmonella and S.aureus cells was observed by transmission and scanning electron microscope.Agarose gel electrophoresis was used to determine the effect of Fe₃C/N-C on genome DNA structure of Salmonella and S.aureus.The toxicity of Fe3C/N-C solution to L929 cells was evaluated by CCK-8toxicity test.Finally,Fe₃C/N-C solution was used to control Salmonella simulatedly contaminated on chestnuts.Results showed that Fe3C/N-C had inhibition effect on both Salmonella and S.aureus,When the original Fe₃C/N-C solution was diluted 10times,it was the minimum inhibitory concentration to inhibit the growth of Salmonella,The minimum inhibitory concentration of Staphylococcus aureus was found when the original solution of Fe₃C/N-C was diluted by 9 times.Based on the fluorescence change after fluorescent dye staining,cells of Salmonella and S.aureus treated by Fe₃C/N-C showed red fluorescence compared with green fluorescence of cells in the control,which indicated that the cell membrane of bacteria was damaged.Observation by transmission and scanning electron microscopy showed that Fe₃C/N-C treatment could cause bacterial cell surface collapse and deformation,damage cell wall and cell membrane,which resulted in cytoplasm leakage.The results of agarose gel electrophoresis showed that Fe₃C/N-C had almost no effect on the integrity of genomic DNA of Salmonella and S.aureus,but decreased the DNA content due to its inhibition on propagation of bacteria.CCK-8 toxicity test showed that the concentration of Fe₃C/N-C original solution diluted 5 times was not significantly toxic to L929 cells.By treating Chinese chestnuts simulatedly contaminated with Salmonella,it was found that Fe₃C/N-C solution could inhibit growth of Salmonella on the chestnuts.This study provides a new material for controlling foodborne pathogens and reference for utilization of Fe₃C/N-C nanomaterial.