Preparation Of Polydopamine-based Composite Nanomaterials And Application In Wound Therapy

Infectious wounds have become one of the serious security threats in the world.Infectious wound mainly refers to the infection of bacteria and other pathogens on the damaged skin surface,which causes the inflammatory reaction in the body.Therefore,the main step in treating infectious wounds is to eliminate bacteria.In recent years,due to the abuse of antibiotics,drug-resistant bacteria have emerged.Instead of relying on antibiotics,researchers have chosen small,adjustable nanomaterials as the main antibacterial materials.Among many nano antibacterial materials,polydopamine（PDA）is favored by researchers because of its excellent biological safety and photothermal stability.However,the use of PDA alone can not achieve good antibacterial effect,which is due to the low photothermal conversion efficiency of PDA.In order to solve the above problems and improve its antibacterial ability.Herein,three different nanomaterials are designed and synthesized based on PDA materials,combined with different antibacterial materials or drugs.The specific research contents are as follows:（1）Ferric chloride hexahydrate（Fe Cl₃·6H₂O）,polyacrylic acid（PAA）and dopamine（DA）were used to synthesize Fe₃O₄@PDA NPs by the hydrothermal method and template method.The positively charged vancomycin（Van）was electrostatic adsorbed onto Fe₃O₄@PDA NPs to get Fe₃O₄@PDA-Van NPs.Fe₃O₄@PDA NPs have the ability to load and continuously release antibiotics at the wound.At the same time,the Fe₃O₄@PDA-Van NPs with NIR laser can kill the bacterial by transfer the photothermal ability to heat,due to the photothermal ability of both Fe₃O₄ NPs and PDA NPs.The combination of drug antibacterial and photothermal antibacterial reduces the use of antibiotics to resist the dependence on antibiotics.（2）In order to get rid of the dependence on antibiotics,we synthesize a multifunctional nanomaterial with photothermal and ion antibacterial ability.We used a simple method to synthesize ultra-small Cu S NPs,then loaded ultra-small Cu S NPs with ZIF-8,and finally obtained Cu S@ZIF-8@PDA NPs by dopamine（DA）self-polymerization.Due to p H responsiveness and degradation ability of ZIF-8,ZIF-8 can not only release encapsulated ultra-small Cu S NPs under acidic conditions,but also degrade to Zn²⁺with antibacterial ability.On the one hand,the outermost PDA of the Cu S@ZIF-8@PDA NPs can improve the biological safety of ZIF-8.On the other hand,they can be used as photothermal agents for antibacterial.Cu S@ZIF-8@PDA NPs can effectively resist bacteria in synergy with photo-thermal-ion combined therapy.（3）Traditional antibacterial nanomaterials are often unable to achieve the theoretical antibacterial effect.The main reason is that antibacterial nanomaterials cannot effectively contact with bacteria.In addition,there is the influence of the environment on the wound surface.Therefore,we successfully synthesized Zn（OH）₂-PDA JNPs with Janus structure using PAA,zinc nitrate hexahydrate（Zn（NO₃）₂·6H₂O）and DA as raw materials,and then encapsulated Zn（OH）₂-PDA JNPs using the sodium alginate（SA）with gel and water absorption properties to obtain SA-His/Zn（OH）₂-PDA hydrogel dressing.The hydrogel dressing has the following advantages:firstly,the hydrogel dressing can effectively adhere to the wound surface to provide an environment that satisfies the requirements of wound healing;secondly,the added L-histidine can accelerate wound healing;thirdly,Zn（OH）₂-PDA JNPs are packaged to prevent the aggregation of nanomaterials and improve the photothermal conversion efficiency of PDA.In addition,the unique Janus structure of Zn（OH）₂-PDA JNPs effectively combines photothermal antibacterial and dual ionic antibacterial properties to achieve synergistic antibacterial.It proved that the hydrogel had an excellent antibacterial effect in the antibacterial experiment in vitro.