Application Of SDF-1α Loaded Polydopamine-Collagen Composite Scaffolds For Skin And Bone Defect Repair

It is a great challenge for the clinical treatment of large area skin and bone defects.The clinical applications of autologous and allogeneic grafts for skin and bone repair are limited due to insufficient donors,immunogenicity,disease transmission and other reasons.In recent years,the application of biomaterials in skin and bone defect repair has achieved good results,which offset the deficiency of autologous and allogeneic skin and bone grafts.Research showed that regeneration speed of local angiogenesis determines the effect of defected tissue repairing.In view of this,we intend to develop a tissue engineered biological scaffold for the repair of skin and bone defects.Collagen(COL),which is commonly used for tissue engineered biological scaffolds,has good biocompatibility,bioactivity,biodegradability and low antigenicity,while has poor vascular effect,mechanical properties,drug loading and sustained release.Stromal cell derived factor-1α(SDF-1α),also known as CXCL12α,is a small molecule cytokine that has obvious advantages in angiogenesis and stem cell recruitment.It has shown that SDF-1α obtained good results in the application of tissue engineered biological scaffolds.Dopamine(DA)is a neurotransmitter enriched with catecholamine content in the brain.Polydopamine(PDA)is produced by oxidized and self-polymerized DA under the condition of aerobic,moist,and weak base.PDA has strong adhesion properties and has advantages in surface modification of biomaterials and sustained release loading drugs.At the same time,PDA has several properties such as good biocompatibility,promoting cell adhesion and proliferation.In view of this,we intend to prepare the COL porous scaffold,whose surface is modified by PDA.And then SDF-1α was loaded inside the scaffold.It was expected that SDF-1α have been released from PDA-COL@SDF-1α composite scaffold to promote angiogenesis and thus promote skin and bone defect repair.This study is divided into the following four parts:Part Ⅰ: COL,PDA-COL and PDA-COL porous scaffolds loaded with different concentrations of SDF-1α(0.5 μg/ml,1.0 μg/ml,2.0 μg/ml)were prepared by freeze drying,chemical crosslinking and physical blending.Subsequently,the material physical properties of each group of scaffolds were described.To explore the immobilization and release of SDF-1α by COL and PDA-COL scaffolds in vitro.The angiogenesis effect of each group of porous scaffolds implanted subcutaneously in nude mice was preliminarily explored.The results showed that the scaffolds in each group had a porous structure.With the modification of PDA,the mechanical strength of the scaffolds increased.The immobilized and sustained release amount of SDF-1α had significantly increased after the surface of the scaffolds modified with PDA in vitro.The vascularization and tissue ingrowth of PDA-COL@SDF-1α composite scaffold was superior to them of COL and PDA-COL scaffolds in vivo.Part Ⅱ: To explore the biocompatibility of COL,PDA-COL and PDA-COL@ SDF-1αcomposite scaffolds and their effects on BMSCs migration and HUVECs angiogenesis in vitro.The result of Live/Dead staining showed that the scaffolds in each group had good biocompatibility,and PDA could promote the proliferation of BMSCs.The results of Transwell and wound healing experiments indicated that the PDA-COL@ SDF-1αcomposite scaffolds could promote the migration of BMSCs better than the COL and PDA-COL scaffolds.Tube formation experiments showed that the PDA-COL@SDF-1αcomposite scaffold could promote the angiogenesis of HUVECs better than the COL and PDA-COL scaffolds.Part Ⅲ: To explore the wound repair effect of Control,COL,PDA-COL and PDA COL@SDF-1α composite scaffolds.General photos of wound healing showed that the PDA-COL@SDF-1α composite scaffold had better wound healing and shorter healing time.Histological analysis showed that the PDA-COL@SDF-1α composite scaffold had more neovascularization and collagen fiber formation than the Control,COL,and PDACOL groups,and had narrower unhealed wound width.PDA plays an important role in epidermal regeneration.In conclusion,the PDA-COL@SDF-1α composite scaffold has a good effect in wound repair.Part Ⅳ: To explore the bone defect repair effects of Control,COL,PDA-COL and PDA-COL@SDF-1α composite scaffolds.Micro-CT reconstruction and analysis showed that the PDA-COL@SDF-1α composite scaffold could promote the formation of new bone better.Compared with Control,COL,and PDA-COL groups,PDA-COL@SDF-1αcomposite scaffolds had larger new bone volume and bone volume fraction.Histological analysis showed that PDA-COL@SDF-1α composite scaffolds had more neovascularization,more collagen fibers,more osteocalcin and more bone tissue formation than Control,COL and PDA-COL groups.In conclusion,the PDACOL@SDF-1α composite scaffold has a good repair effect in bone defects.