Design And Preparation Of Multi-functional Hydrogels For Skin Wound Healing

Hydrogels,which can provide the moist microenvironment for skin wound healing,have attracted great interest and attention of researchers as dressings for skin wound repair,due to soft texture,good biocompatibility,and variable designability.Skin wounds are susceptible to bacterial infection in the healing process,and lots of hydrogel dressings with antibacterial properties have been reported in the literature.Meanwhile,the report about hydrogel with antibacterial and antibacterial adhesive function simultaneously is insufficient.Furthermore,for wounds induced by surgical removal of skin tumors,it is vital for tumor excision to simultaneously take into account antibacterial,antitumor,and wound healing.And it is challenging to develop such multifunctional dressings for skin tumor wounds.Besides,the hydrogel dressings with non-adhesive are convenient for replacement during the usage process,but other adhesive medical material stuff is needed for the fixation of these dressings.Self-adhesive hydrogel dressings can stick on the skin wound indirectly,but injuring young growing tissue may occur during dressing replacement.Currently,there is still no satisfactory strategy for how to solve the dilemma of"adhesive but not adhesive"for the hydrogel dressings of skin wound healing.Regarding the above issues,and based on fully summarizing the previous researches,multifunctional hydrogel dressings with applicability and practicality for skin wound healing were designed and prepared in this doctoral thesis.The main research contents and conclusions are as follows.（1）Random copolymers P（GMA-co-MPC）were synthesized by atom transfer radical polymerization（ATRP）,and then the Gel-Mm Gn hydrogels were prepared by a ring-opening reaction of the epoxy group with CTM.The gelling mechanism,basic physical and chemical properties of hydrogels were investigated in detail.And the antibacterial property,antibacterial adhesion behavior,biocompatibility,and therapeutic effect on the full-thickness defect of Gel-GmMn were evaluated systematically.The experimental results show that gelling time and swelling ratio（SR）of Gel-GmMn inversely proportional to polymer concentration.The hydrogels present a typical loose and porous three-dimensional network structure,and their maximum compression ratio is higher than 70%,displaying sufficient mechanical properties for usage as a wound dressing.Cytotoxicity assay shows that the hydrogels exhibit excellent cell compatibility for RBCs and L929.In the antibacterial experiment,the inhibitory ratio of Gel-GmMn against S.aureus and E.coli is exceeded 95%.After contacting with the hydrogels for 24 h,almost no bacteria is observed on the surface of the hydrogels.Results of the wound repair experiment in vivo demonstrate that the wounds in the hydrogel and Cur-loaded hydrogel exhibit almost close,while the residual wound area for the control group is still 9%after 14days of treatment.The staining results show that skin tissues display more mature morphology in the hydrogel treatment groups.Therefore,Gel-GmMn may be used as hydrogel dressings of skin wound healing with simultaneous antibacterial and antibacterial adhesive function.（2）Amino-functionalized copper sulfide nanoparticles（CuS NPs）were synthesized through the metal coordination between Cu²⁺and sulfhydryl group.Meantime,oxidized dextran（ODex）was obtained by the sodium periodate oxidation method.CuS NPs and ODex were mixed with polyethylene glycol（NH₂-PEG-NH₂）to prepare polysaccharide-nano copper sulfide composite hydrogel（CuS NC）.The gelling mechanism,basic physical and chemical properties of hydrogels were investigated and the biocompatibility in vitro and in vivo was evaluated.Finally,the photothermal/dynamics properties and the Cu²⁺release behavior of CuS NC hydrogels under the irradiation of 808 nm near-infrared light were explored.The experimental results show that CuS NC hydrogel is fabricated by dynamic imine bond and hemiacetal interaction,and exhibits injectability and good self-healing behavior.The introduction of CuS NPs does not cause significant changes in the rheological properties and microstructure of the polysaccharide hydrogel.Under NIR irradiation,the temperature of CuS NC hydrogel show adjustability,which is positively correlated with the laser power,CuS NPs content,and illumination time.Meanwhile,the reactive oxygen species generated from CuS NC hydrogel is increased with the prolongation of irradiation time and the increase of CuS NPs content.Finally,it is found that CuS NC hydrogel with Cu²⁺release behavior and the release of Cu²⁺is slightly promoted by NIR light irradiation.（3）In this part,the antibacterial properties,therapeutic effect in antitumor,and skin wound healing of CuS NC hydrogel were evaluated systemically.The results of antibacterial experiments show that the inhibitory effect on S.aureus and E.coli is weak by reactive oxygen species produced from CuS NC hydrogel under NIR light,while the inhibition ratio against bacteria is up to 100%with the addition of photothermal therapy of G-CuS0.5 hydrogel.Besides,the results of the anti-tumor experiment show that the cell viability of F10B16 treated with G-CuS1 under 808 nm laster is about 50%.After being treated for 14 days,the volume of the B16F10 tumor decreases to 20%in Gel-CuS1 with NIR groups,while the tumor volume in control groups increases to 500%.After co-culturing with hydrogel leach solution for 6 days,L929 and HUVEC viability increases to 215%and 195%,respectively.And the HUVEC cell scratch demonstrates almost complete healing for 48 h co-culturing with hydrogel leach solution.Rat full-thickness shin defects treated with CuS NC hydrogel display a shorter healing period,and richer capillaries,and more mature tissue structure than those of the control group.This work proves that CuS NC hydrogel under NIR light can be used as the dressings of wound healing after skin tumor excision with antibacterial and antitumor functions.（4）The solution of chitosan（CS）oxidized（ODex）containing acrylamide and poly[2-（methacryloyloxy）ethyl 2-（trimethylammonio）ethyl phosphate]（MPC）or acrylate adenine（Aa）was used to obtain non-adhesive（Nad）or adhesive hydrogel（Ad）by Schiff base and free radical polymerization,respectively.The preparation process of adhesive-non-adhesive integrative hydrogel is first casting the gelling solution of non-adhesive hydrogel and waiting for the formation of polysaccharide single network,then,casting the gelling solution of adhesive hydrogel and waiting for self-healing of two parts into one,finally,free radical polymerization at 60°C was performed to prepare the integrated Ad-Nad hydrogel.The basic physical and chemical properties such as swelling,water retention,and rheology behavior of the hydrogels were measured.The mechanical properties and adhesive strength of the hydrogels were evaluated in detail.Meanwhile,the interface combine ability of two-part hydrogel was investigated.Finally,the biological safety,hemostasis,and antibacterial properties of hydrogels were evaluated systematically.The results show that Nad hydrogels present non-adhesive,meanwhile,their swelling ratio and water retention ratio are increased with the usage amount of MPC and the maximum value is up to 800%and 90%,respectively.In contrast,Ad hydrogels have outstanding adhesion to various substrates,and the maximum adhesive strength to the skin is 20k Pa.Furthermore,results of the tension test and SEM demonstrate that two-part hydrogels with opposite properties can be completely combined.Besides,the surface of rat skin maintains normal morphology after adhered with Ad hydrogel for 24 h.Nad hydrogel displays good cytocompatibility for RBCs and L929,and excellent hemostatic and antibacterial properties.In a word,this investigation prepares a multifunctional hydrogel dressing for skin wound healing and provides a new approach to solve the dilemma of"adhesive but not adhesive"for wound healing dressings.