Surface Modification Of Additive Manufacturing Titanium Alloys Implant And Their Biological Properties

Titanium(Ti)and its alloys have been widely used as hard tissue materials because of their good mechanical properties,low elastic modulus and excellent biocompatibility.Additive manufacturing(AM)technology of metal materials has been continuously improved,showing obvious advantages in the rapid production of customized products and the realization of complex modeling.It has a wide range of applications in the field of biomedical.However,Ti is a bioinert material and does not have the ability of immune regulation,which could lead to long-term inflammatory response,poor osteointegration effect after implanted in human body.Ti powders on the surface of implants prepared by AM technology are eassy to fall off,which lead to osteolysis.Therefore,surface modification on Ti implant surface manufactured by AM technology is needed to improve the surface quality,enhance the biocompatibility and osteointegration ability,and regulate the inflammatory response.In this paper,the micro/nano-structure coating bioactive ions were prepared on Ti implants surface to enhance their biological properties.Firstly,the effect of anodic oxidation parameters on Ti implant surface manufactured by AM was studied.Acid etching was used to remove the unmelted Ti powders on the surface of laser selective melting(SLM)Ti implant,exposing the micrometer structure.Through the anodic oxidation in different electrolyte and voltage conditions,the surface morphology and nanotube size were studied.The results showed that in the NH4F-glycerol electrolytic system,the diameter of nanotubes formed on the surface of AM Ti implant was better.The diameter of nanotubes was positively correlated with the voltage.Secondly,the construction of micro/nano-structure coating Ca ions on SLM fabricated Ti implant and its effect on bone marrow mesenchymal stem cells(BMSCs)were studied.The micro/nano-structured surface,amufactured by SLM was prepared by acid etching and anodix oxidation.After the second step of anodic oxidation,Ca ions were successfully added.The results showed that the micro/nano-structure coating Ca ions could enhance the hydrophilicity and biological activity of AM implants,and promoted the adhesion,proliferation and differentiation of BMSCs.Then,the surface construction and biological properties of the micro/nano-structured surface coating Ca and Zn ions on SLM Ti implant were studied.Ca and Zn ions were added on the surface of micro/nano-struceture by alkali heat treatment.The results showed that the diameter of nanotubes decreases slightly and the surface roughness changes little after alkali heat treatment.Cell experiments showed that Ca and Zn ions had a more obvious enhancing effect on BMSCs,and Zn ions could regulate the polarization behavior of macrophages.Finally,the osteogenic properties of AM implants in vivo were studied.The Ti rod implants manufactured by SLMwas treated with acid etching,anodic oxidation and alkali heat treatment,and implanted into the femur of SD rats.The amount of new bone around the titanium rod was observed by micro-CT.The results show that the titanium rods with bioactive ions have good osteogenic properties.