Synthesis And Characterization Of Plasmonic Nanocomposites And The Study On Their Antibacterial Properties

Due to the continuous emergence of bacterial resistance and the protection of stubborn biofilm,traditional antibiotic therapy is difficult to achieve satisfactory antibacterial effect.In recent years,photothermal therapy（PTT）has attracted more attentions of researchers and been widely applied in the antibacterial field due to its advantages of spatio-temporal controllability,non-invasiveness,broad spectrum,and its ability to effectively kill non-resistant and drug-resistant bacteria without causing drug resistance.Due to their good surface enhanced Raman scattering（SERS）,photocatalytic and near-infrared photothermal activity,plasmonic nanomaterials can be used as multifunctional photothermal agents in antibacterial studies.In general,in order to obtain the desired antibacterial effect,the use of laser with high power density and high concentration of photothermal agents in photothermal therapy will inevitably cause damage to normal tissues.Therefore,it is of great significance to develop photothermal agents with high photothermal conversion ability in order to obtain the photothermal therapeutic effect while minimizing side effects.In addition,according to different application scenarios,the composition and structure of plasmonic nanocomposites should be rationally configurated to prepare multimode PTT-derived antibacterial agents,which is expected to reduce the side effects of single photothermal therapy and further improve the efficacy.In addition to the above photothermal properties,SERS effect of plasmonic nanomaterials can also be used for microbial sensing detection.Based on the above backgrounds,the following studies were carried out in this paper:1.Integrated research on the Au-Azo@Ag-CTAB nanocomposites for bacterial detection and inactivation:This chapter took the detection of the total amount of microorganisms in tap water as the starting point,and prepared a universal SERS nanoprobe based on the reasonable configuration of the recognition unit,Raman tag and SERS substrate.Subsequently,the synthesis process of the probe was optimized,and the final product was obtained by combining SERS signal intensity and probe stability.Positively-charged Au-Azo@Ag-CTAB nanoparticles were adsorbed on the surface of bacteria through electrostatic action so as to realize SERS sensor detection of bacteria.The results of quantitative detection showed that SERS signal intensity had a good linear correlation with bacterial concentration.Finally,the probe was used to detect the spiked bacteria in tap water,and the results proved that the method was reliable and could completely inactivate the remaining bacteria in the detection system,avoiding environment pollution.2.Multifunctional Au@Cu_2-xS nanocomposites for root canal therapy:In this chapter,Au@Cu_2-xS nanoparticles with photothermal and peroxidase-like catalytic activities were prepared and characterized to address the the challenge about inactivation of bacteria in root canal biofilms.Due to the plasmon resonance coupling effect between the core and shell,the nanoparticles not only have significantly enhanced photothermal activity,but also can catalyze hydrogen peroxide at biosafety concentration into hydroxyl radical,realizing efficient degradation of biofilms.The results of the in vitro study showed that the photothermal/Chemodynamic combined therapy based on Au@Cu_2-xS nanoparticles had better antibacterial effect,and the nanoparticles had good biocompatibility.We further applied the combined therapy to antibacterial studies of isolated tooth slices,root canals and Beagle dogs,and the results proved that this method can effectively inactivate bacteria in the root canal biofilm.3.Functional CuS@Au@ZnPBA nanocomposites for promoting infected wounds healing:In this chapter,a non-pharmaceutical photothermal antibacterial agent consisting of CuS,Au and Zn²⁺doped Prussian blue analogue was prepared and characterized to address the problem of bacterial resistance caused by traditional antibiotic therapy in wound infection treatment.The results of in vitro study showed that the photothermal agent had significantly enhanced antibacterial ability.Under the irradiation of 808 nm laser,the local heat generated by nanocomposites can effectively inactivate bacteria in infected mouse wounds,and the slowly-released Zn²⁺can accelerate wound healing by promoting collagen formation.4.Multifunctional GO@PDA/Ag-PF127 composite hydrogel for promoting infected wounds healing:In this chapter,an antibacterial hydrogel dressing with on-demand removal characteristics was prepared to improve the convenience of changing hydrogel dressings.Two-dimensional graphene oxide nanomaterials were introduced into the thermosensitive hydrogel matrix by dynamically reversible borate ester bonds,which not only accelerated the sol-gel transition,but also improved the rheological properties of the hydrogel.The introduction of polydopamine endows hydrogels with good oxidation resistance and adhesion properties,and the controlled removal of hydrogels can be realized through temperature-sensitive phase transition.The results of in vitro antibacterial study showed that the hydrogel has good photothermal antibacterial effect,and the controllably-released silver ion also has good antibacterial ability,so it can continue to manage the infected wound.The in vivo study showed that the hydrogel had good biosafety,and could alleviate inflammation and promote wound healing in infected mice.