Fabrication And Antibacterial Application Of Photo-responsive Of AuAg Graphitic Nanocapsules

Current traditional bacterial treatment methods mainly rely on antibiotics,and the abuse of antibiotics has led to the emergence of a large number of drug-resistant bacteria,posing a great threat to human beings.Photothermal therapy（PTT）is a new type of bacterial treatment method,which can achieve high-efficiency photothermal antibacterial while avoiding the generation of bacterial resistance.Due to the advantages of near-infrared（NIR）laser with strong tissue penetration,less absorption by water and body fluids,and less scattering loss,NIR laser-mediated PTT is very suitable for application in the biomedical field.Noble metal nanomaterials are commonly used photothermal reagents because they generate localized surface plasmon resonance（LSPR）under laser irradiation and convert excited-state photon energy into thermal energy.More importantly,noble metal nanomaterials can control the LSPR bandwidth by changing the size,shape,or structure,thereby improving their photothermal effects in the near-infrared band.However,bare noble metal nanomaterials have low thermal stability and are prone to deformation and agglomeration under prolonged laser irradiation,which affects their photothermal properties and further photothermal applications.In response to this problem,metal graphitic nanocapsules with inert graphite shell were prepared,which exhibited excellent photothermal stability and photothermal treatment effects.As a three-dimensional network structure,hydrogel has the advantages of absorbing wound tissue exudate,isolating the external environment,reducing wound temperature,etc.,so it is considered as one of the best choices for wound dressings.To further broaden the antibacterial application range of metal graphitic nanocapsules,we combined them with hydrogels to construct novel photothermal antibacterial materials.The hydrogel loaded with metal graphitic nanocapsules integrates anti-infection and antioxidant advantages,and it can be used as a photothermal antibacterial wound dressing to treat infected wounds and promote wound healing.The details are as follows:（1）In Chapter 2,in order to obtain noble metal nanomaterials with certain photothermal conversion ability and high photothermal stability in the near-infrared band,we prepared graphene-isolated-Au Ag nanocapsules（GIAAN）with absorption in the NIR-I region（700 nm-900 nm）by chemical vapor deposition（CVD）,and the successful synthesis of GIAAN was proved by various characterization results.Further,we explored the photothermal stability,photothermal heating ability and photothermal antibacterial effect of GIAAN under 808 nm laser irradiation.The results showed that GIAAN had good photothermal stability,GIAAN concentration and laser power affected the photothermal heating ability of GIAAN,and under the same laser power,the higher the GIAAN concentration,the higher the photothermal antibacterial efficiency.Therefore,GIAAN is a novel nanomaterial with facile synthesis and excellent photothermal antibacterial properties,which has great potential in the field of biomedical applications.（2）In Chapter 3,NIR-I laser-mediated photothermal therapy is difficult to achieve clinical conversion,while NIR-II（1000 nm-1350 nm）laser-mediated photothermal therapy has a higher maximum allowable exposure,deeper tissue penetration depth and lower scattering loss,which is more likely to be converted into clinical treatment.We obtained cavity Graphene-Isolated-Au Ag Nanocapsules（cGIAAN）with certain photothermal conversion ability under NIR-II laser irradiation by changing the CH₄ pass time.Due to the changes in structure and size,cGIAAN has a wider LSPR band than GIAAN and has stronger absorption in the near-infrared II region.Next,we demonstrated the excellent photothermal capability and high photothermal conversion efficiency of cGIAAN under 1064 nm laser irradiation.To further broaden the biomedical applications of cGIAAN,we loaded cGIAAN into an oligoaniline-grafted oxidized hyaluronic acid/O-carboxymethyl chitosan hydrogel（cGIAAN-OT/OCS hydrogel）.The results showed that cGIAAN did not affect the performance of the hydrogel itself,and under 1064 nm laser irradiation,the photothermal heating ability of cGIAAN-OT/OCS hydrogel depended on the concentration of cGIAAN and the laser power.cGIAAN-OT/OCS hydrogel is expected to be a multifunctional wound dressing as a photothermal hydrogel responsive to NIR-II laser.（3）In Chapter 4,based on the excellent photothermal conversion ability of cGIAAN-OT/OCS hydrogel under NIR-II laser irradiation and its advantages as wound dressing,we explored its applications in bacterial treatment.First,we demonstrated the good biocompatibility and excellent in vitro photothermal antibacterial ability of the cGIAAN-OT/OCS hydrogel.Next,we used cGIAAN-OT/OCS hydrogel to perform photothermal antibacterial treatment on mouse wounds infected with MRSA,and the killing rate of MRSA could reach more than 95%.Finally,we demonstrated the good biosafety of the cGIAAN-OT/OCS hydrogel.Therefore,the composite hydrogel is a novel photothermal antibacterial wound dressing that is expected to achieve clinical translation,providing a new option for the treatment of infected wounds.