Construction Of Copper-strontium Hydroxyapatite Coatings On The Surface Of Metal 3D Printed Porous Structures And Study Of Bone Ingrowth Properties

The porous Ti6Al4 V scaffolds formed through 3D printing at the artificial replacement joint fixation interface can adjust its elastic modulus to match the host bone,and solve the stress shielding problem.At the same time,the porous scaffolds is conducive to cell adhesion and provides sufficient space for the growth of new bone tissue.However,there are still problems such as mismatch between hardness and bone tissue,early infection,and slow bone growth.Therefore,porous Ti6Al4 V scaffolds were prepared using laser melting technology(SLM),and hydroxyapatite coatings containing copper and strontium metal ions were prepared using hydrothermal methods to obtain mechanical properties that meet human body requirements,and the scaffolds were endowed with stronger biological activity,antibacterial activity,and bone growth promoting properties.Firstly,porous Ti6Al4 V scaffolds with bone trabeculae,X-shaped,tetrahedral,rhombic dodecahedral,uniform Gyroid structure,and gradient Gyroid structure were designed and fabricated.The surface of porous Ti6Al4 V scaffolds is relatively rough,providing more adhesion sites for cell adhesion,have good biocompatibility and the ability to interact with cells.The porous Ti6Al4 V scaffolds with X-shaped structure has the best mechanical properties,P=290.3MPa,E=4.41 GPa.The results of biological experiments in vitro showed that the porous Ti6Al4 V scaffolds had no cytotoxicity,and had good proliferation and osteogenic abilities.The expression levels of ALP,OCN,and RUNX-2 osteogenesis related genes on the porous Ti6Al4 V scaffolds with an Xshaped structure are higher than those of the rhombohedral dodecahedron and trabecular bone,but lower than those of the tetrahedron.Combined with mechanical properties,the X-shaped structure is the most suitable porous Ti6Al4 V scaffold structure.Secondly,HA bio-coatings doped with 2%,4%,and 6% metallic copper ions were applied on porous Ti6Al4 V scaffolds by hydrothermal method.In vitro biological experiments showed that HA coating doped with 2% metallic copper ions facilitated cell adhesion,growth,ALP expression and osteogenic differentiation on porous Ti6Al4 V scaffolds.Q-PCR illustrated higher expression levels of ALP,OCN,and RUNX-2 osteogenic genes on HA coatings doped with 2% metallic copper ions.Antibacterial experiments have demonstrated that the antibacterial property increases as the amount of doped metal copper ions in HA coating increases.The HA coating doped with 2% metallic copper ions has the dual function of resisting early infection and promoting bone growth.Then,porous Ti6Al4 V scaffolds were coated with HA biocoatings doped with 5%,10%,and 15% metal strontium ions,respectively.In vitro biological experiments showed that all three HA coatings with strontium content had good biocompatibility,and the HA coating doped with 5% metal strontium ions had significant ability to promote ALP expression and osteogenic differentiation of cells.After 14 days of osteogenesis-induced differentiation,the results showed that HA coating doped with 5% metal strontium ions was more favorable for the expression of ALP,OCN,and RINX-2 osteogenic genes.Finally,HA bio-coatings co-doped with 2% metallic copper ions and 5% metallic strontium ions were constructed on X-type porous Ti6Al4 V scaffolds.The proliferation of cells on this coating and the osteogenic differentiation ability were better than those of HA coating doped with 2% metallic copper ions and doped with 5% metallic strontium ions.The results of antibacterial experiments and osteogenic gene expression showed that co-doped copper and strontium ions could make the X-type porous Ti6Al4 V scaffold possess both better antibacterial and bone growth promoting effects.