Study On Photothermal And Photodynamic Antibacterial Composite Based On Two-dimensional Graphite Carbon Nitride

During the medicine field,the process of wound healing is usually accompanied by the occurrence of a certain degree of bacterial infection and the subsequent inflammatory response,the most common treatment currently is antibiotics and sterile dressings.However,excessive use of antibiotics has led to the emergence of many resistant bacteria or superbacteria.They are highly resistant to common antibiotics and can not be killed effectly.Therefore,studies of rapid,effective and safe antibacterial means while also promoting wound repair has become particularly urgent.With the advancement of medical means,nano-biomaterials are gradually being used in disease treatment and medical rehabilitation.Among of them,photodynamic therapy（PDT）and photothermal therapy（PTT）are new bactericidal treatment strategies based on near-infrared（NIR）light for nanomaterials.PDT is using photosensitizers to generate reactive oxygen radicals（including ¹O₂、·OH、·O₂^-）.But single PDT treatment can also cause damage to the surrounding normal tissue.The two-dimensional g-C₃N₄ is a kind of common photocatalyst with a 2.7 e V band gap,which can be used for photolysis of hydrogen under visible light,but the penetration of visible light in the wavelength range is weak towards the skin or tissue of the human body.Therefore,we can modify g-C₃N₄ for the employment of near-infrared light.PTT is based on localized heating of one or two dimensional semiconductor materials with strong light absorption in the near-infrared to kill bacteria.The research content of this paper is specifically divided into the following three parts:1:The design and preparation of different proportions of composite semiconductor nanomaterial structure（zinc-doped g-C₃N₄ and GO composite structure）were successfully designed,and zinc ions were doped into g-C₃N₄ by chemical vapor deposition.The zinc-doped g-C₃N₄ and GO structure are combined by electrostatic action with ultrasonic dispersion synthesis.The composite structure with optimal photothermal photodynamic effects is optimized by comparison of photothermal performance and photodynamic performance.The results show that GO possesses well photothermal effect under near-infrared light of 808 nm.Pure SCN and SCN-Zn²⁺have no obvious photothermal properties.With the increase of GO content,SCN-Zn²⁺@GO shows better photothermal performance.Meanwhile,SCN-Zn²⁺@GO also has well photothermal stability.In addition,the photocatalytic performance of SCN-Zn²⁺@GO is enhanced compared with SCN-Zn²⁺and GO,while excess GO does not further reduce the energy gap.2:The two-dimensional semiconductor g-C₃N₄ doped with single metal zinc and GO byπ-πconjugation and electrostatic interaction were selected as the research system with 660 nm and near-infrared 808 nm mixed light excitation.The synergistic effect of reactive oxygen radicals and photothermal effects can quickly kill bacteria within 10 min,and the sterilization efficiency exceeds 99.1%towards S.aureus and E.coli.The released zinc ions can also promote the proliferation and differentiation of fibroblasts,thereby promoting wound healing process.Bacterial activity and cell membrane integrity under the irradiation of 660 nm red light and 808nm light are affected,and then can be easily killed.3:The photothermal property and photodynamic performance of the composite are controlled by adjusting the combination ratio of the Bi₂S₃ nanorods and the zinc-doped graphite carbon nitride,and a reasonable ratio is selected for the antibacterial and wound repair.The mechanism of photocatalytic performance improvement was studied by first principle theoretical analysis.We investigated the mechanism of this synergistic antibacterial method through bacterial membrane permeability studies,bacterial membrane potential,F-type ATP synthase and characterization of bacterial reactive oxygen species.Then,the ability to promote wound repair was studied by wound healing experiments in vivo,and the bactericidal ability was studied by the observation of inflammatory reaction and pathological analysis.