Study On Preparation And Antibacterial Properties Of Montmorillonite-based Organic/Inorganic Composite Antibacterial Materials

The abuse of antibiotics have caused environmental pollution and increased the number of resistant strains.The drug resistance of bacteria has become an urgent problem to be solved.Therefore,the development and application of new antibacterial materials have become a hot issue to prevent microbial contamination.In this paper,organic/inorganic composite antibacterial materials were prepared,and the antibacterial properties and mechanism of tested materials were studied.(1)ZnO/Cu2+-CS/MMT was prepared by loading inorganic antimicrobial agents including zinc oxide and copper ions on the organic modification of montmorillonite with chitosan.The characterization results showed that chitosan adsorbed on inner and outer sufaces of montmorillonite.Zinc oxide and copper ions were successfully loaded on it.After chitosan modification and inorganic antibacterial agent loading,montmorillonite layered structure underwent slight local deformation,such as an increase in specific surface area.(2)The minimum bactericidal concentrations of ZnO/Cu2+-CS/MMT against Escherichia coli,Salmonella typhimurium and Staphylococcus aureus were 2.0,2.0 and 1.0 mg/mL,respectively.It indicated that ZnO/Cu2+-CS/MMT had excellent antibacterial activity.The inhibition mechanism was that ZnO/Cu2+-CS/MMT destroyed the morphology of bacterial cells,and bacterial cells were shrunken,rough,wrinkled,and sticky.The cell membrane permeability increased,and intracellular proteins and nucleic acids leaked.Oxidative damage of cells was caused by active oxygen.(3)Car-CTAB/MMT and Thy-CTAB/MMT were prepared by loading natural antimicrobial agents including carvone and thymol on the organic modification of montmorillonite with CTAB.The characterization results showed that the spacing of montmorillonite layer became larger after cetyltrimethylammonium bromide,carvacrol and thymol entered to its layer.And the specific surface area of montmorillonite decreased while pore diameter increased after it was modified.(4)The minimum bactericidal concentrations of Car-CTAB/MMT against Staphylococcus aureus and Escherichia coli were 233 and 931 ?g/mL,respectively;the minimum bactericidal concentrations of Thy-CTAB/MMT against Saphylococcus aureus and Escherichia coli were 311 and 1244 ?g/mL,both showed that Car-CTAB/MMT and Thy-CTAB/MMT had great antibacterial activity.The bacteriostatic properties of carvacrol and thymol were improved after loaded.Car-CTAB/MMT and Thy-CTAB/MMT had adsorption to bacteria.The inhibition mechanisms of Car-CTAB/MMT and Thy-CTAB/MMT were that they destroyed bacterial cells morphology during sterilization.Cell wall structure was damaged and cell membrane permeability increased,which led to leakage of intracellular proteins and nucleic acids.In summary,ZnO/Cu2+-CS/MMT,Car-CTAB/MMT and Thy-CTAB/MMT were prepared.The prepared composite materials showed excellent antibacterial effect on tested strains.And their bactericidal mechanisms were explored,which provided an important reference for the development of such antibacterial materials.