A Synergistic Antibacterial Platform Combining Mechanical And Photothermal Effects

In the past,people had a fierce fight against bacteria.In the face of diseases caused by bacterial infection,people fought against bacteria by means of developing vaccines,improving sanitation and using antibiotics.People used to call antibiotics"magic bullets"optimistically,but the overuse and misuse of antibiotics has led to the production of bacterial resistance,so it is urgent to find and develop new ways to fight bacterial infections.Near-infrared（NIR）photothermal method is a new method for the treatment of bacterial infection,which has the advantages of broad-spectrum antibacterial,no harm to human tissues.Molybdenum disulfide（MoS₂）is widely used in the field of biomedicine due to its advantages of good dispersion,strong stability,good biocompatibility and favourable photothermal effect.In addition,mechanical sterilization has a physical sterilization effect through the design of different material morphology.These materials can contact with the bacterial cell wall directly,resulting in the leakage of bacterial contents,and finally cell death.Therefore,combined with the advantages of photothermal and mechanical sterilization,we synthesized a synergistic antibacterial platform combining the physical bactericidal structure（Au nanostars）and the photothermal material MoS₂.Meanwhile,the targeted molecule vancomycin（Van）was modified in the Van-MoS₂-Au nanocomposites to improve the antibacterial ability.This work mainly includes the following aspects:1.Synthesis of Van-MoS₂-Au.Firstly,a monolayer MoS₂nanosheet was synthesized by solvothermal method,and the target molecules vancomycin were connected to the surface（Van-MoS₂）.Due to the targeting advantage of vancomycin,it can interact strongly with D-Ala-D-Ala that is the terminal of bacterial membrane peptide unit,through hydrogen bond and obtains high antibacterial efficiency.Then,the Au nanostars were prepared by redox method to make them have mechanical sterilization.Van-MoS₂-Au nanocomposites was prepared by combining the advantages of Au nanostars and Van-MoS₂,which not only had strong antibacterial properties,but also had good biocompatibility and stability.2.Characterization of Van-MoS₂-Aunanocomposite.At first,the characteristics of Van-MoS₂-Au nanocomposites was measured by transmission electron microscopy and atomic force microscopy,respectively.The size of Van-MoS₂-Au nanocomposites was150-200 nm,the height was 35-40 nm,and the size was uniform on the Van-MoS₂nanosheets.The size of Au nanostars is 50 nm and the height of Au nanostars is 35-40 nm.Au nanostars are uniformly distributed on the Van-MoS₂surface.The element distribution of Van-MoS₂-Au nanocomposites was measured by TEM mapping.The results show that Mo,S and Au are evenly distributed.Finally,the photothermal performance of Van-MoS₂-Au was tested by 808 nm NIR.The results showed that Van-MoS₂-Au had good photothermal absorption effect,and the temperature can reach about 60°C in 20 s when the concentration is up to 160 ppm.3.Antibacterial effect of Van-MoS₂-Au nanocomposites.Van-MoS₂-Au nanocomposites were treated with gram-positive bacteria（Bacillus subtilis）and gram-negative bacteria（Escherichia coli）.Through scanning electron microscope observation,plate test and bacterial fluorescent live/dead stainings,it was proved that Van-MoS₂-Au nanocomposites had strong and broad-spectrum bactericidal properties.4.Destruction of bacterial biofilm.Van-MoS₂-Au nanocomposite was applied to the destruction of Staphylococcus aureus biofilm,and the results showed that the Van-MoS₂-Au nanocomposites could disperse the Staphylococcus aureus biofilm,and it was observed that Van-MoS₂-Au nanocomposites could kill the residual bacteria in the biofilm through the live/dead fluorescence staining experiment.In conclusion,we developed a novel antibacterial platform in this work,and it has good biocompatibility and strong antibacterial ability.It initiates a new way for antibacterial materials,and provides a new technology,which has a broad prospect of biomedical application.