3D Forming And Performance Study Of PLA/HA/Mg Composite Scaffolds For Bone Tissue Engineerin

Currently,the number of patients with bone defects and their related diseases due to diseases and accidents is increasing,and tissue engineering research provides a solution to this problem by implanting a bone tissue engineering scaffold into the bone defect site to replace the bone tissue at the defect site,with osteoblasts proliferating and differentiating on the surface and inside the scaffold,while the scaffold degrades in vivo,and artificial porous scaffolds are receiving increasing attention as the best bone defect implants.An ideal bone tissue engineering scaffold should have a suitable pore structure for cell attachment,nutrient transport,and metabolite discharge,mechanical properties similar to those of human bone,and good biocompatibility and degradability.In this study,polylactic acid(PLA),hydroxyapatite(HA),and magnesium(Mg)were used as raw materials to prepare ortho tetrahedral self-locking porous scaffolds and spatial lattice structure scaffolds using 3D printing technology,and the physicochemical properties,biocompatible properties and degradability of the scaffolds were investigated.Firstly,the preparation and characterization of bone tissue engineering scaffolds.We prepared PLA/HA/Mg composites with different mass fractions of HA and Mg and prepared pure PLA ortho tetrahedral self-locking structural scaffolds and PLA/HA/Mg composite spatial lattice structural scaffolds using fused deposition molding(FDM)3D printing technology and then characterized and evaluated the surface morphology,porosity,hydrophilicity,water absorption and mechanical properties of the scaffolds.The results showed that the scaffolds made by FDM 3D printing had regular shape,clear boundary,through and regular pores,good reproducibility,and the porosity and dimensions were in accordance with the requirements of bone tissue engineering,indicating that the method of preparing porous tissue scaffolds by FDM 3D printing technology is feasible;HA and Mg can enhance the hydrophilicity of the scaffolds,which is conducive to cell adhesion,spreading and proliferation and differentiation on the scaffold surface,while can help the transport of nutrients and the discharge of metabolic waste;porous scaffolds have good load-bearing resistance and shock-absorbing effect,and the laminar structure can prevent monolithic damage;the mechanical properties of PLA positive tetrahedral self-locking scaffolds are negatively correlated with porosity,with compressive strength ranging from1.24 to 6.27 MPa and compressive modulus ranging from 11.99 to 33.25 MPa;PLA/HA/ Mg composite scaffolds had lower compressive strength and compressive modulus than pure PLA scaffolds,and their compressive modulus decreased significantly when 10wt% HA was added,and their mechanical properties improved when 2wt% Mg was added,but with the increase of Mg content,the agglomeration of Mg was obvious and the mechanical properties of the scaffolds started to decrease.the PLA/HA/Mg composite scaffolds with 10wt% HA,and 2wt% Mg compression strength was 9.48 MPa,which had the best mechanical properties and matched the mechanical properties of cancellous bone,and it was used for the subsequent tests.Then,the pure PLA scaffold and PLA/HA/Mg composite scaffold were co-cultured with mouse bone marrow mesenchymal stem cells(BMSCs)in vitro,respectively,to investigate the affinity and induced osteogenic differentiation ability of the scaffolds.The results showed that the number of live cells on all scaffolds gradually increased with the passage of culture time,the number of dead cells was minimal,the cells were vigorous and evenly distributed,the spreading area of cell membrane became larger and more uniform,the number of live cells on the PLA/HA/Mg composite scaffold was significantly higher than that on the pure PLA scaffold,the cell activity was better,the number of cells and spreading status were better,the cell morphology was good,and the introduction of HA and Mg The introduction of HA and Mg did not produce obvious toxic side effects on cells,and effectively improved the biocompatibility of PLA scaffolds,which was conducive to cell proliferation,adhesion and spreading on the scaffolds;both PLA scaffolds and PLA/HA/Mg composite scaffolds could effectively promote the expression of cellular alkaline phosphatase(ALP),and the ALP activity of cells on PLA/HA/Mg composite scaffolds was significantly higher than that of PLA scaffolds.A large amount of mineralized area appeared on both groups of scaffolds,while more calcium nodules and higher calcium salt quantification were observed on the PLA/HA/Mg composite scaffolds,and the presence of HA and Mg significantly improved the ability of the scaffolds to induce osteogenic differentiation of cells.Finally,the PLA/HA/Mg composite scaffolds were immersed in phosphate buffered solution(PBS)for in vitro degradation performance study.The results showed that with the immersion time,the corrosion of the scaffold surface became more and more significant,and the surface became rough,accompanied by pores,cracks,and corrosion products;the mass of the PLA/HA/Mg composite scaffold first increased slightly and then gradually decreased;the PBS buffer solution as a whole did not appear acidic environment,and the p H value generally showed an increasing trend and stabilized after a while;the mechanical properties of the PLA/HA/Mg composite scaffold decreased.The mechanical properties of the PLA/HA/Mg composite scaffold decreased,and the compressive strength and compressive modulus gradually decreased and maintained within the range of bone tissue engineering requirements.