Preparation And Properties Of 3D Printed Strontium-doped Mineralized Collagen Composite Polylactic Acid Scaffold For Bone Repair

Bone tissue engineering repair materials generally need to have good biocompatibility,appropriate physical and mechanical properties to provide support,appropriate porosity pore size for material exchange and cell climbing growth,degradability and bone healing effect,and other excellent properties.It is difficult for a single material to meet all the requirements of bone repair materials,and composites can often improve their overall performance by complementing the advantages of each component material.In this thesis,poly（L-lactic acid）（PLLA）and mineralized collagen（MC）were prepared by electrostatic adsorption,and their physicochemical properties and cytocompatibility were investigated.The low dose of strontium can promote the proliferation and differentiation of osteoblasts,reduce cellular bone resorption by attenuating osteoclast production,and stimulate angiogenesis,which have good effects on bone defect repair.In this thesis,strontium-doped mineralized collagen was prepared by an in vitro bionic approach.In order to meet the higher requirements of bone repair materials,the two materials were co-blended to print bone repair scaffolds by combining the advantages of regular and accurate fiber arrangement,controlled porosity pore size and interoperable pores of the prepared scaffolds by 3D printing manufacturing technology.The physicochemical properties and cytocompatibility of the materials were subsequently investigated.（1）FTIR characterization and SEM surface morphology were performed for the membrane materials,and the results showed that type I collagen was adsorbed onto the PLLA membrane more uniformly,and the longer the adsorption time,the more uniformly the collagen was distributed on the PLLA membrane.The results of CCK-8 cytotoxicity evaluation showed that the composite membranes could be considered non-cytotoxic.The composite membrane showed a significant promotion of cell proliferation by BCA protein concentration assay,which was also verified by alkaline cell protease staining observation.（2）For the scaffold material,XRD characterization,EDS elemental analysis and surface morphology observation of mineralized collagen powder showed that the material possessed inorganic phase and nanostructure similar to human bone;thermal analysis showed that the composite material was suitable for the 3D printing method used in this thesis.SEM showed that the pore size of the scaffold was in the range of 400 μm～500μm,which was consistent with the model design,with uniform fibers and basically no collapse and after cross-sectional observation,the homogeneity of the co-blended material is good,and all pores of the scaffold are connected,with a high with a continuous and stable three-dimensional mesh structure,which is conducive to material exchange and waste exclusion,and cell adhesion and growth.The results of the mechanical property tests showed that the composite scaffold had suitable compressive properties and could provide good support performance during bone repair without stress masking.The composite scaffold is non-cytotoxic and has good biocompatibility.The results of induced differentiation co-culture of RAW264.7 cells showed that the strontium-doped composite scaffold had a certain inhibitory effect on the generation and activity of osteoclasts,and the comprehensive performance indicated that the Sr MC/PLA composite scaffold prepared in this thesis has good application value in bone tissue engineering repair materials.