Preparation And Antibacterial Properties Of Mesoporous Polydopamine-based Nanocomposites

Food poisoning incidents caused by foodborne pathogens account for the highest proportion of all types of food safety incidents and have become the primary problem facing food safety in China.Due to the broad-spectrum resistance of foodborne pathogenic bacteria,many traditional antibiotics do not provide good treatment for the infections they cause,highlighting the urgent need for new alternative antimicrobial agents.The rise of nanotechnology has brought new ideas for inactivating foodborne pathogenic bacteria,so the development of antibacterial nanomaterials that are less susceptible to drug resistance is of great importance to ensure food safety.In recent years,photothermal sterilization technology with nanomaterials as the core has shown a broad application prospect in the field of microbial control as an ideal new sterilization method.Therefore,in this paper,Staphylococcus aureus and Escherichia coli were used as research objects,two photothermal composite nanobacterial systems were designed based on mesoporous polydopamine-based nanomaterials,and the synergistic bactericidal activity and bactericidal mechanism were investigated.The main research is summarized as follows:1.MPDA@Ag study on bacteriostatic properties of foodborne pathogenic bacteriaIn this part,a MPDA@Ag nanobacterial system for photothermal sterilization and Ag~+synergistic sterilization was prepared by in-situ reduction of mesoporous polydopamine as the basic material,and the antibacterial activity and antibacterial mechanism of MPDA@Ag against Staphylococcus aureus and Escherichia coli were studied.The successful preparation of the nanomicrobial system was confirmed by SEM,TEM,UV-VIS,Mapping and ICP-MS.The bactericidal activity of the nano-antimicrobial system was explored by growth kinetics and plate coating.Observation of bacterial morphology,cell membrane permeation experiments,membrane potential experiments and contents leakage experiments showed that MPDA@Ag destroyed the integrity of cell membranes,interfered with their normal functions,and eventually led to bacterial death.The inhibition experiment,elimination experiment and three-dimensional structure scanning image of the biocoating showed that the MPDA@Ag showed good inhibition and elimination effect on the biofilm of Staphylococcus aureus.Finally,cytotoxicity experiments proved that it has good biocompatibility.The design of this nano-antimicrobial system provides an idea for the development of new nano-antimicrobial agents.2.SNP@MPDA study on bacteriostatic properties of foodborne pathogenic bacteriaIn this part,a synergistic antibacterial SNP@MPDA system integrating photothermal sterilization and gas sterilization was prepared by using mesoporous polydopamine as the base material and loaded with nitric oxide precursor sodium nitroprusside with heat release properties.The successful preparation of this nano-antimicrobial material was confirmed by characterization methods such as SEM,TEM and Mapping.Experiments have shown that SNP@MPDA can not only increase the temperature but also release nitric oxide under near-infrared irradiation.Growth kinetics and plate coating experiments showed that the SNP@MPDA had good antibacterial activity against Staphylococcus aureus and Escherichia coli,showing broad-spectrum bactericidal performance.The observation of bacterial morphology,cell membrane permeability experiment,membrane potential experiment and content leakage experiment showed that the SNP@MPDA seriously destroyed the cell membrane integrity of the bacteria,interfered with the growth and metabolism of bacteria,and led to bacterial death.The inhibition and elimination experiments of biocoating show that SNP@MPDA has the ability to inhibit the formation of biofilm and eliminate the mature biofilm.The research and development of this nano-antibacterial system provides certain theoretical guidance for its application in the field of inactivating foodborne pathogenic bacteria.