Biological Properties Of Micro-arc Oxidized Titanium Implanted With Gas Ions

Titanium and its alloys have become the material of choice for medical implants due to their excellent comprehensive mechanical properties and biocompatibility.However,traditional titanium implants still have many problems,such as longer healing time,the lower binding rate between implants and bones.In order to obtain better osseointegration activity,micro-arc oxidation（MAO）technology is often used to modify the surface of implants to improve their biological activities.However,TiO₂ is a bio-inert material and the porous structure makes it inevitable for TiO₂ coatings to be contaminated by hydrocarbon pollutants in the air,which leads to a decrease of the hydrophilicity and biological activity.Furthermore,the implants are susceptible to bacterial infection due to the lack of antibacterial properties.In order to improve the osteogenic and antibacterial properties,hydrogen（H₂）and nitrogen（N₂）were separately implanted into the micro-arc oxidized titanium surface by plasma immersion ion implantation（PIII）technology.The influences of implantation parameters on the osteogenic and antibacterial properties of micro-arc oxidized titanium samples were investigated.Moreover,the effects of surface compositions and band change on osteogenic and antibacterial properties were discussed.Hydrogen was implanted into TiO₂ coatings by PIII.The surface structures and crystal phase compositions of the samples implanted with H₂ had not been altered,but the contact angle of the samples was significantly reduced after H-PIII.The band structure of TiO₂ was also changed.The enhanced cell viability,osteogenic differentiation and collagen secretion of rat bone mesenchymal stem cells（r BMSCs）could be observed on the surfaces of H-PIII samples.Besides,the surface of H-PIII samples exhibited bacteriostatic effects on both Escherichia coli（E.coli）and Staphylococcus aureus（S.aureus）.Nitrogen was implanted into TiO₂ coatings by PIII.After N-PIII,the surface topographies and crystal phase compositions of MAO samples had not been altered.However,the hydrophilicity of the surfaces was improved,and the optical gap of TiO₂was narrowed.The cell experiments in vitro showed that N-PIII samples had good biocompatibility and early osteogenic differentiation properties.The bacterial experiment in vitro demonstrated that nitrogen-incorporated TiO₂ could effectively reduce the viability of E.coli and S.aureus in visible light.In summary,the osteogenic and antibacterial properties of TiO₂ coatings fabricated by MAO were improved after H-PIII and N-PIII.H-PIII could significantly enhance the osteogenic and bacteriostatic properties of TiO₂ coatings.Nitrogen-incorporated TiO₂ showed good biocompatibility and early osteogenic differentiation properties,and could effectively reduce the bacterial viability in visible light.The materials and method in this study may provide new insights for the surface design of orthopedic implants.