Preparation And Properties Of Injectable Nanofibers/hydrogel Multifunctional Hybrid Dressing

The skin is the largest organ in the human body and it provides an important barrier against the external environment.A wound is usually defined as an injury that occurs within the skin,connective tissue,or mucous membranes and may result in a defect in the structure or function of an organ.Wounds are generally classified into two main types,acute and chronic.Among them,chronic wounds have attracted great attention of the whole society due to their high morbidity and mortality.Chronic wounds include infected wounds,pressure ulcers,burns,and diabetic feet.Designing and preparing wound dressings that can effectively deal with chronic wound repair is an important trend in the development of new biomaterials.An ideal wound dressing requires the following properties:(1)retain moisture in the wound environment while absorbing excess fluid and exudate;(2)allow gas transmission;(3)provide a barrier to protect the wound from external trauma,at the same time,it prevents microbial invasion;(4)be easy to remove or it is biodegradable,so that it can avoid damage to the new tissue during the removal process.Based on the above requirements,this research selected hydrogel as the main body of the dressing and prepared a series of multifunctional hybrid dressings.The hydrogel hybrid dressing designed in this project has various functions such as biocompatibility,biodegradability,adhesion,electrical conductivity,and hemostatic,antibacterial and pro-angiogenesis properties,and showing great potential in chronic wound repair.The research work of this paper mainly includes the following aspects:The formation of most chronic wounds is associated with infection of bacterial biofilms.It is difficult for common antimicrobial agents to completely eradicate mature bacterial biofilms due to the hindrance of bacterial resistance.Based on the above situation,this subject researched and synthesized a polysaccharide-based injectable hydrogel dressing modified by recognizable bacterial biofilm-type polypeptides for bacterial biofilms removal and repair of infected chronic wounds.Firstly,this project successfully grafted the polypeptide fragments(alanine-glutamic acid-lysinealanine)in peptidoglycan into quaternized carboxymethyl chitosan(HTCC).Subsequently,an injectable hydrogel dressing(HTCC-P/OD)was prepared by cross-linking polypeptide-modified quaternized carboxymethyl chitosan(HTCC-P)and oxidized dextran(OD).The quaternary ammonium salt group in the hydrogel dressing can effectively penetrate the bacterial cell wall and cell membrane under the action of the recognition peptide to achieve the purpose of killing bacteria.Studies have shown that the cationic quaternary ammonium salt group significantly enhances the permeability of bacterial biofilms under the recognition of polypeptides,and effectively enhances the antibacterial and antibacterial biofilm properties of hydrogel dressings.At the same time,the antibacterial properties of HTCC-P/OD hydrogel dressings against Staphylococcus aureus,Escherichia coli,Bacillus subtilis and Pseudomonas aeruginosa were evaluated respectively.The results proved that the HTCC-P/OD hydrogel has broad-spectrum antibacterial properties,and the antibacterial rate against four strains is greater than 99%.In addition,the HTCC-P/OD injectable hydrogel prepared by dynamic cross-linking of Schiff bases exhibits excellent self-healing properties and can fully cover irregular wound shapes.Cytotoxicity and in vivo wound healing research confirmed the good biocompatibility and ability of the HTCC-P/OD hydrogel dressing to accelerate tissue reconstruction and promote wound repair.In conclusion,the polypeptide-modified hydrogel dressings exhibit excellent antibacterial properties in the repair of chronic infection wounds,and are expected to become competitive antibacterial dressings in the biomedical field.Injectable hydrogels seriously hinder their application in tissue engineering and other fields due to their poor mechanical properties.In this project,the nanofiber-reinforced injectable hydrogel hybrid dressing(NFRH)was constructed by compounding nanofibers and hydrogels,which effectively improved the mechanical properties of injectable hydrogel dressings.The study have shown that by loading the nanofibers into the hydrogel,the stability and mechanical strength of the hydrogels could be improved.After the peptide-modified nanofibers are loaded into the hydrogel,the hybrid dressing not only retains the antibacterial and hemostatic properties of the peptide,but also can induce the aggregation of blood cells and platelets for rapid hemostasis,and effectively inhibits bacterial infection at the wound,ultimately accelerating the healing of chronic wounds.In addition,the NFRH hydrogel is prepared by dynamic cross-linking of Schiff base,and the injectable and self-healing properties can make the hydrogel dressing adapt to the deep irregular wound shape and effectively prolong its service life.Taken together,NFRH hydrogel dressings have potential as a multifunctional novel dressing for chronic wound repair.Pressure ulcers,as high-incidence chronic wounds,pose a serious economic burden to patients,especially the elderly.Preventing the occurrence of pressure ulcers and treating chronic wounds are urgent problems to be solved at this stage.Based on the continuation of the nanofiber/hydrogel hybrid dressing in the previous study,this topic changed the disorderly dispersed nanofibers in the hydrogel into oriented nanofiber yarns(NFY)to prepare the 3D hybrid dressings with adhesion,antibacterial and L929 fibroblast orientation-inducing properties for monitoring and repairing chronic wounds.Among them,the aligned NFY network is constructed by weaving nanofiber yarns prepared by blending polyacrylonitrile(PAN)and reduced graphene oxide(r GO).Studies have shown that oriented NFYs show the ability to effectively induce the elongation and orientation of L929 fibroblasts,and the spreading direction of L929 fibroblasts on their surfaces can be effectively controlled by regulating the orientation of NFYs.3D composite dressings were prepared by preloading nanofiber yarn(NFY)networks into injectable hydrogels cross-linked by Schiff bases.The injectable hydrogel outside the NFY network not only provides protection for the L929 fibroblasts on the NFY surface,but also mimics the natural extracellular matrix(ECM),providing a suitable 3D microenvironment for cell proliferation and arrangement.In addition,by adding metal ions into the hydrogel hybrid dressing,the hydrogel hybrid dressing was endowed with excellent electrical conductivity,which made the hydrogel composite dressing have the potential to be a flexible strain sensor to accurately monitor the pressure changes in the wound.The nanofiber yarn(NFY)network/injectable hydrogel 3D hybrid dressings prepared in this resesrch display good biocompatibility,self-healing properties and antibacterial properties,which show a wide range of application prospects in biomedical fields,especially in tissue engineering and wearable electronic products.