Construction Of Functional Composite Scaffolds For Wound Healing

Injury and damage to organs and tissues can seriously affect people’s health and quality of life.Conventional treatment methods,such as autologous tissue grafting,allogenic organ transplantation,drug therapies,and surgical operations have achieved satisfactory outcomes but still carry risks.Issues include exacerbated immune response and rejection,donor shortages,adverse drug effects,etc.At present,tissue engineering technologies have been developed using functional scaffold preparations and bioactive substance modification to regulate cell activity.These approaches have proven effective in the promotion of wound healing in vivo.In this thesis,various tissue engineering techniques were applied to cater to different wound healing situations,which included scar-free skin wound healing,spatially guided tissue regeneration,and bone tissue reconstruction.The repair process of full-thickness dermal injuries is often accompanied by scar formation(fibrosis),which can result in a great burden on patient health,mobility,and psychology.There are many difficulties faced when exploring the pathogenesis and treatment of dermal fibrosis.Recently,an engineered synthetic anti-fibrotic38-amino-acid polypeptide(AF38pep)– designed to mimic the binding functionality of the integrin receptor binding cleft and block pro-fibrotic extra domain A fibronectin(EDA-FN)interactions with fibroblasts – was developed.In the first part of this study,carboxymethyl chitosan(CMCS)was crosslinked with genipin andγ-poly(glutamic acid)(γ-PGA)to form hydrogels loaded with AF38 pep.The natural composite hydrogels for scar prevention(HSP)had continuous porous structures,were biocompatible,had effective hemostatic abilities,and possessed antimicrobial properties.HSP effectively inhibited the proliferation and migration of activated fibroblasts,and downregulated genes and proteins associated with fibrosis.Rapid release of AF38 pep was conducive to inhibiting fibrosis formation in a timely and effective manner during the early stages of wound healing.In addition,HSP regulated dermal wound healing by promoting organized and normal regeneration of epidermis and dermis layers,whilst controlling ordered distribution and maturity of collagen fibers.In addition,HSP accelerated the regression of the acute inflammatory response,prevented chronic inflammation,and facilitated the formation of skin accessory structures and neovascularization.RNA-Seq analysis revealed that scar-free skin regeneration of HSP was mainly related to extracellular matrix(ECM)-cell interactions and focal adhesion(FA)signaling.In conclusion,HSP effectively inhibited scar formation and promoted the regeneration of normal skin.The incidence of periodontal disease continues to increase across the world.Guided tissue regeneration(GTR)membranes have been effective in treating periodontal diseases,but have shortcomings such as singular function,unsuitable degradation rates,poor mechanical properties,etc.The biological functions of chitosan(CS)include biocompatibility,antibacterial activity and antihemorrhagic activity,making CS a suitable and widely used polymer component in tissue engineering.In the second part of this thesis,"sandwich-like" poly(ε-caprolactone)(PCL)/gelatin composite nanofibers were combined with CS by electrospinning and freeze-drying to generate composite nanofiber membranes with uniform morphology,a stable three-layer structure,and suitable mechanical properties.Membrane degradation rates could be controlled by adjusting the PCL/gelatin ratio.Composite nanofiber membranes were cyto-compatible,improved cell growth activity and promoted blood coagulation in vitro.Furthermore,the dense and stable structure of the membranes effectively prevented external cell infiltration after subcutaneous implantation in rats for 4 weeks.The sandwich-like composite nanofiber membranes combined with CS were deemed advantageous for use as GTR membranes and have strong potential for application in the field of tissue regeneration and dentistry.With increasing global population and mean lifespan,the repair and treatment of bone defects has become one of modern medicine’s great clinical challenges.Bone tissue engineering scaffolds have brought new hope for bone repair,but current developments have associated problems,such as low biological activity,poor mechanical stability,and weak bone induction effects.Platelet-rich fibrin(PRF)can be harvested following blood extraction and is rich in various growth factors conducive to tissue regeneration.In the third part of this thesis,composite hydrogels(CPH)were fabricated from CS,γ-PGA,and nanohydroxyapatite(n HA)using electrostatic crosslinking.CPH were used to fill the site of bone defect and promoted osteoconduction.Another biomaterial,PCL/gelatin nanofibers(P2G3)effectively prevented soft tissue migration to sites of bone defects by attachment to the junction between hard and soft tissues.Thus,a multilayered biomaterial consisting of an osteoconductive CPH layer,an osteoinductive PRF middle layer,and a soft tissue inhibiting P2G3 layer was used to assess benefits in bone tissue regeneration.The multilayered composite scaffolds provided mechanical stability and high mineralization activity in vitro.The stable layered structure could realize personalized preparation for repair of various sized and shaped bone defects.In addition,multilayered scaffolds revealed biocompatibility,osteogenic differentiation potential,and the effective promotion of calvarial repair in rats and alveolar bone regeneration in rabbits.In short,the multifunctional and multilayered composite scaffolds combined with PRF effectively promoted bone repair by combining the advantages of osteoinduction,osteoconduction,and osseointegration,which could provide new and pragmatic concepts for bone tissue regeneration in clinical applications.In conclusion,different types of multifunctional composite scaffolds were prepared and combined with a variety of bioactive substances for diverse wound healing application.The biomaterials designed and evaluated in this thesis offer wide application in tissue engineering strategies and provide new research strategies for the repair of tissue/organ injury and damage,and promising prospects toward future clinical application.