Study On The Germicidal Activity Of New Copper-based Metal Oxide Nano-antimicrobial Agents Against Food-borne Pathogenic Bacterial

In recent years,China's food industry has developed rapidly,and the output value of the food industry has maintained a trend of sustained growth.However,food safety problems occur frequently.Among all kinds of food safety incidents,food poisoning caused by foodborne pathogens accounts for the highest proportion.Therefore,strictly take effective measures to guard against the contamination of food-borne pathogenic bacteria is particularly urgent.At present,the traditional sterilization technology mainly includes ultra-high voltage sterilization technology,irradiation sterilization technology,ozone sterilization technology,pulsed electric field sterilization,ultrasonic sterilization technology and so on.However,these traditional sterilization methods have their inherent defects.For example,the domestic food ultra-high pressure treatment technology is not yet mature and has not been put into food industry production on a large scale;irradiation sterilization costs are high,very inconvenient,and affect production efficiency and processing costs;the cost of high voltage pulsed electric field sterilization system is very expensive and ultrasonic sterilization technology is faced with the problems of narrow scope of application,incomplete disinfection and many influencing factors.Therefore,the research and development of new and efficient sterilization technology is of great significance to ensure food safety.The primary research achievements of this paper are as follows:1.Preparation of copper manganate nano-antibacterial agent and its bactericidal activity against pathogenic bacteria.Copper manganate nanoflakes(Cu Mn O₂ NFs)were prepared by hydrothermal and ultrasound-assisted stripping methods.The successful preparation of Cu Mn O₂ NFs was confirmed by TEM,EDS,XRD,XPS,AFM and other characterization methods.TMB catalytic oxidation and fluorescence test showed that the nano-antibacterial agent had excellent peroxidase catalytic activity.After the introduction of near-infrared light,the solution temperature increases rapidly,which proves that the nano-antibacterial agent can be used as a good photothermal agent.Through the plate coating experiment,it was confirmed that the nano-antimicrobial agent had good efficacy in killing both Gram-negative Escherichia coli(E.coli)and Gram-positive Staphylococcus aureus(S.aureus).The results of staining of living dead bacteria and observation of cell morphology reveal that the antibacterial mechanism is that the nano-antibacterial agent catalyzes low concentration of H₂O₂ to produce cytotoxic hydroxyl radical(·OH),which causes oxidative stress on the cell membrane,and then destroys the cell membrane.After the introduction of near-infrared light,the heat generated by near-infrared light is synergistic to·OH,causing bacterial cell membrane to rupture,and cell content is released,resulting in bacterial death.The research and development of Cu Mn O₂NFs nano-antimicrobial agents can not only effectively kill foodborne pathogens,but also replace the use of antibiotics to a certain extent,which is of great significance for the development of new sterilization technology of food instruments and the protection of food safety.2.Preparation of hemoglobin-functionalized copper ferrite nano-antimicrobial agents and their bactericidal activity against pathogenic bacteria.A multifunctional copper ferrite(Hb-CFNPs)nano-antibacterial agent based on hemoglobin was prepared by a simple hydrothermal synthesis route.The successful preparation of Hb-CFNPs was confirmed by SEM,TEM,FTIR,XRD,TGA,XPS and UV-vis.The magnetic hysteresis loop diagram of Hb-CFNPs confirmed that the nanoparticle had strong magnetic properties.The excellent peroxidase catalytic activity of the nanoparticle was proved by MB degradation and TMB color test.Hb-CFNPs can catalyze low concentration of H₂O₂ to produce a large amount of·OH.Compared with unmodified CFNPs and BSA-CFNPs,the introduction of Hb improved its biocompatibility and the overall catalytic activity.At the same time,the nanoparticle has excellent near-infrared photothermal conversion properties.In addition,due to the excellent magnetic properties of Hb-CFNPs,the photothermal efficiency can be increased by about 20 times through magnetic enrichment,which is beneficial to achieve excellent germicidal efficacy at a very low experimental dose(20?g/m L).The antibacterial tests of E.coli and S.aureus showed that Hb-CFNPs showed excellent efficacy in killing both bacteria under the synergistic action of photothermal and Fenton catalysis.The results of live and dead bacteria staining,SEM technique and GSH assay revealed that the antibacterial mechanism of the nanoparticle was that the cell membrane was broken,the cell content was discharged,and the GSH in the bacterial cell was consumed,which led to the destruction of the defense mechanism and the death of the bacteria under the irradiation of near infrared light and low concentration of H₂O₂.After being used in food sterilization,Hb-CFNPs antimicrobial agent can be separated from the food system in time by magnetic enrichment,and will not cause food matrix pollution,so it has a good application prospect.