Preparation And Performance Study Of Polydopamine Composite Antibacterial Material

Bacterial infections have many serious adverse effects on human society,causing millions of casesand high mortality rate each year.Antibiotics were the earliest drugs to be used for bacterial infection,but overuse of antibiotics has led to bacterial resistance.It is dangerous that we only rely on antibiotics and related methods to control bacterial infections in the future.Therefore,it is urgent to synthesize alternatives to antibiotics and find new ways to fight bacteria and replying the challenge of superbugs to human health.PDA is a potential antibacterial material.On the one hand,due to its excellent photothermal conversion ability,it can generate a lot of heat in a short period of time under the irradiation of near-infrared light,denaturating the protein on the bacterial membrane,destroying the structure of bacterial cell membrane.Therefore,the bacteria will be killed.On the other hand,due to its abundant reaction sites,it can be combined with other substances through metal chelation and electrostatic adsorption to form composite antibacterial materials.Thus,PDA has great potential in the application of antibacterial materials.The development of biological antibacterial dressings has received extensive attention.However,the antibacterial hydrogels prepared at present have some disadvantages,such as limited antibacterial ability,short service life and poor biocompatibility,so difficulties still exist in practical application.In the first chapter,we utilize the reducing and electronegativity of PDANPs to reduce[Ag（NH₃）₂]⁺to Ag NPs on the surface of PDANPs.Then,by taking advantage of the cross-link between the o-diol from sodium alginate and borate ions produced by borax dissolved in water,the near infrared responsive SABA/Borax/PDA-Ag NPs hydrogel was developed from mixed SABA,Borax and PDA-Ag NPs.The hydrogel has good self-healing,swelling,photothermal conversion ability,as well as biocompatibility and antibacterial activity.Results of vitro and in vivo test showed that hydrogel has good bactericidal ability with antibacterial rate up to 100%.The results of wound healing experiments showed that the hydrogel has the ability to promote wound healing,indicating that SABA/Borax/PDA-Ag NPs hydrogel have great potential in the application of biological dressings.Although single-mode antimicrobial technology has received a lot of attention,it has limitations in completely eradicating bacteria.In the second chapter,proposed a multimodal antibacterial strategy based on calcium peroxide loaded polydopamine nanoparticles（PDA@Ca O₂）.First,calcium ions are adsorbed on the surface of PDANPs by chelation between phenolic hydroxyl and Ca²⁺.Second,Ca²⁺is converted to Ca O₂by H₂O₂,thus PDA@Ca O₂ nanoparticles are successfully prepared.In this system,calcium peroxide dissolved in water can slowly and continuously release H₂O₂ and calcium hydroxide,resulting in the destruction of bacteria in the water environment.Under near-infrared laser irradiation,light energy is converted into heat energy due to the presence of PDANPs,realizing the combination of ROS and PTT antibacterial treatment,and the antibacterial effect is significantly enhanced.In vitro antibacterial experiments show that PDA@Ca O₂ nanoparticles have excellent antibacterial effects on S.aureus and E.coli,and all bacteria can be killed under NIR irradiation.Vivo experiment of wound healing has confirmed that PDA@Ca O₂ nanoparticles can enhance bacterial clearance and promote wound healing,with high biocompatibility.This study can provide a promising direction for the rational design of multimodal antibacterial system.