The Preparation Of Photothermal Nano-composite Hydrogel And Investigation Of Its Application In Wound Repair

Skin wound healing is a complex and continuous process,which is affected by many factors.The wound infection caused by bacteria contamination will lead to prolonged healing,wound pain,suppuration and so on.A serious infection or improper treatment will lead to tissue damage,and even threaten the health of patients.Although traditional dry dressings,such as gauze and bandage,can temporarily protect the wound and absorb part of the exudate,they are difficult to be widely used in bacterial infectious wounds due to their dry,easy adhesion and lack of antibacterial properties.In recent years,antibacterial hydrogels have shown great application prospects in the field of infectious wound repair due to their good biocompatibility,the ability to mimic the three-dimensional microenvironment of extracellular matrix（ECM）and the ability to keep the wound moist.However,the conventional antibiotic loaded hydrogels are prone to cause bacterial resistance and have a low drug utilization efficiency.With the increasing clinical requirements for wound repair,in addition to combat bacteria,the ideal skin wound repair materials also need multiple functions such as anti-inflammation,anti-oxidation,angiogenesis,promoting tissue repair and even inhibiting tumor recurrence.Therefore,the development of new multifunctional antibacterial hydrogel dressings has the important significance and clinical value to meet the diversified needs in the field of wound repair,such as wound infection treatment and tumor postsurgical tissue repair.Photothermal therapy（PTT）is a technology that converts specific wavelength of light into local high temperature.PTT has been paid more and more attention in the field of antibacterial therapy,due to its advantages of,minimally invasive,non-surgical,deep tissue penetration and avoiding the production of drug-resistant bacteria.Herein,nanomaterials with excellent photothermal properties and good biocompatibility were introduced into the thermosensitive injectable Pluronic F127 based hydrogel system.At the same time,other active components like antibacterial,antioxidant,angiogenic,anti-tumor and tissue repair promoting functions were integrated to construct a new multifunctional photothermal composite hydrogel system.Furthermore,its effectiveness was evaluated by in vitro bacterial/cell experiments and in vivo studies to explore its application potential in the treatment of skin wound infection,melanoma postoperative repair and other fields.This research includes the following contents:（1）The application of the nanocomposite hydrogel with photothermal activity and nitric oxide（NO）controlled release function in infected wound repairPolydopamine nanosheets（PDA NS）were synthesized using a one-pot method by DNA templates-mediated PDA polymerization.NO donor（N,N’-di-sec-butyl-N,N’-dinitroso-1,4-phenylenediamine,BNN6）was loaded onto the surface of PDA nanosheets viaπ-πstacking interactions.Thus,the nanocomposites（PDA-BNN6 NS）with good photothermal effects and NO release function were obtained.Furthermore,adipic acid dihydrazide modified-Polyglutamic acid（-PGA-ADH）and aldehyde modified Pluronic F127（F127-CHO）were prepared,and physically mixed with PDA-BNN6 NS to construct composite injectable hydrogel GFPB（G:-PGA-ADH;F:F127-CHO;P:PDA NS;B:BNN6）.The GPPB hydrogel with a stable three-dimensional network structure was formed by the dynamic acylhydrazone bond between hydrazide and aldehyde,as well as the hydrophobic interaction of F127-CHO micelles.The results of rheological experiments showed that the composite hydrogel had good temperature sensitivity and self-healing properties.In addition,under the irradiation of 808 nm near-infrared（NIR）laser,the PDA NS exhibited excellent photothermal conversion performance（the photothermal conversion efficiency 56.1%）and realized the controllable release of NO gas in GFPB hydrogel.The combination of photothermal and NO gas therapy with a synergistic antibacterial effect works on both Staphylococcus and Escherichia coli aureus in vitro and the antibacterial rates were 99.7%and 98.9%respectively.The results of cytotoxicity test showed that the composite hydrogel had a good cytocompatibility.The results of mouse full-thickness skin infection experiment in vivo showed that near-infrared light responsive GFPB hydrogel could effectively kill bacteria,reduce inflammation,promote skin regeneration and significantly accelerate the process of wound healing.（2）The application of the photothermal nanocomposite hydrogel with antibacterial,antioxidant and angiogenic multifunctions in infected wound repairFirstly,sulfonated chitosan（SCS）was prepared by modifying natural high polymer chitosan（CS）.Then,a new injectable multifunctional composite hydrogel FSCP（F:F127-CHO;S:SCS;C:Copper,Cu;P:PDA NS）was prepared by blending SCS with Cu²⁺,PDA nanosheets and F127-CHO via a"one pot"method.The FSCP hydrogel was prepared by the coordination between SCS and copper ions,and the dynamic imine base bond formed by amino group on SCS and aldehyde group on F127-CHO,as well as micellization cross-linking.Muti-crosslinking strategy gave the hydrogel suitable gelation time（about 41 s）and low swelling rate（11.8）,good self-healing performance and excellent mechanical properties.Due to the introduction of PDA nanosheets,FSCP hydrogel showed excellent photothermal conversion ability and free radical scavenging performance.The results of antibacterial experiments in vitro showed that the combination of PTT and Cu ions could effectively kill Staphylococcus aureus and Escherichia coli.At the same time,cell experiments demonstrated that SCS and Cu ions could promote the neovascularization.In addition,FSCP hydrogel could effectively protect fibroblasts around the wounds from ROS damage via ROS scavenging.The results of animal experiment in vivo also confirmed that FSCP composite hydrogel achieved high-efficiency antibacterial and antioxidant properties,alleviated inflammation,promoted angiogenesis and accelerated skin wound repair.（3）The application of the self-assembled photothermal nanocomposite hydrogel for postoperative tumor repair and infected wound repairIn order to solve the problem of postoperative infection and tumor recurrence after skin tumor resection,a self-assembled photothermal nanocomposite hydrogel was developed through a local PTT/chemotherapy.Firstly,F127 was modified by low molecular weight polyethyleneimine（PEI）for preparing F127-PEI,and then aldehyde modified F127（F127-CHO）and F127-PEI were formed into the main network of the hydrogel according to Schiff base reaction and F127 micellization.At the same time,the near-infrared dye IR820 and curcumin（Cur）were used to prepare a novel nanoparticles by ultrasound triggered small molecule self-assembly strategy（Cur@IR820）.The negatively charged Cur@IR820 nanoparticles were introduced into the positively charged hydrogel to obtain the photothermal nanocomposite hydrogel（hydrogel/Cur@IR820）.The studies of surface topography,photothermal and anti-oxidation properties confirmed that Cur@IR820 nanoparticles were successfully loaded into the composite hydrogel,which had a typical porous structure,excellent photothermal conversion performance and concentration dependent oxidation resistance.The results of rheological tests showed that the mechanical properties of the composite hydrogel at 37°C are much higher than that at 25°C,indicating its good temperature sensitivity.The reversible dynamic imine base bond crosslinking gave the hydrogel good self-healing performance.The results of in vitro antibacterial and cell experiments in vitro demonstrated that under the irradiation of 808 nm near-infrared laser,the composite hydrogel achieved a high antibacterial/antitumor activity through PTT and the controlled release of Cur.The studies of mouse melanoma skin defect model and wound infection model further proved that hydrogel had excellent antibacterial,anti-tumor recurrence and wound healing effects.