Study Of PLGA Three-dimensional Scaffolds Co-modified By BMP-9 And P-15 Polypeptides In The Repair Of Rabbit Bone Defects

Purpose:Three-dimensional printed polylactic acid-glycolic acid(PLGA)scaffold was prepared,and then bone morphogenetic protein-9(BMP-9)and P-15 polypeptide hydrogel were used to modify the scaffold,analyze the structure and effect of the stent complex,and evaluate its application in the repair of rabbit bone defects.Method:1.Preparation of three-dimensional scaffolds of polylactic acid hydroxyacetic acid copolymer by melt deposition method,observation of the spatial structure of the scaffold using electron microscopy,and characterization of the scaffold using X-ray diffraction,in vitro degradation rate,and compressive strength.2.The hydrogel containing BMP-9 and P-15 was prepared.The apoptosis rate of cells in different peptide groups was detected by flow cytometry,and the adhesion between cells and scaffolds was observed by electron microscope.3.To analyze the efficacy of scaffold complexes,immunoblotting was used to detect the expression of Alkaline phosphatase(ALP),Collagen-I(Col-I),Osteocalcin(OCN),RUNT related transcription factor 2(RUNX2),and osteogenic related transcription factor(SP7).4.Construct a bone defect model,observe the formation of new bone in the experimental group and control group using Micro CT,and detect the expression of bone tissue related proteins in the rabbit bone defect model.Result:1.The 3D printing scaffold is a cylindrical porous structure,the inner diameter of the bracket is about 1 mm,the porosity is good,and the diffraction peak distribution is wide,indicating that 3D printing only involves physical changes and does not change the properties of the material,and the degradation rate of the scaffold is 9.38%,the water absorption rate is about 9.09%,and the compressive strength is15.83N/mm2,which met the performance requirements of the biological scaffold;2.In the experiment to determine the apoptosis rate,the co-culture of bone marrow mesenchymal stem cells with scaffolds showed that 2% of the polypeptide group had the most obvious effect on the induction differentiation of bone marrow mesenchymal stem cells.Flow cytometry showed that neither the 0% nor 2% groups caused significant apoptosis compared with the control group.Scaffolds containing2% and 4% peptides promoted the expression of ALP,Col-1,OCN,RUNX2,and SP7 in BMSCs;3.In vivo experiments showed that the expression of ALP,COL-1,OCN,RUNX2,and Sp7 protein in the 2% polypeptide scaffold group increased significantly compared with the model group;4.Micro-CT detection showed that compared with other experimental and control groups,2% peptide scaffolds had good bone repair ability in bone defect models;In conclusion:The three-dimensional PLGA scaffold materials modified with BMP-9 and P-15 peptide hydrogel has good biocompatibility,mechanical properties and osteogenesis,which can induce new bone formation,and is feasible for the repair and treatment of large-size bone defects.