Preparation And Osteoinductive Efficacy Study Of Organic Strontium Coating

Titanium and titanium alloys which have excellent mechanical properties and biocompatibility have a wide range of applications in the field of bone repair materials.As a kind of micro/nanostructure on titanium surface,TiO₂ nanotubes have attracted much attention because of their unique structure,simple preparation and high corrosion resistance.But,they all have the problem of insufficient biological activity.In order to improve the osteogenic activity of pure titanium and TiO₂ nanotubes,the organic strontium coatings were fabricated on pure titanium surface and TiO₂nanotubes by the technique of the strong adhesion of dopamine and sodium alginate modification.Then,Sr²⁺release behavior and the biological activity of titanium and TiO₂ nanotubes were explored.（1）The grafting of sodium alginate onto the surface of titanium was carried out by strong adhesion of dopamine,and the organic strontium coating was prepared by chelating strontium with sodium alginate.The modified samples were characterized by SEM,ATR-IR and XPS.The results showed that the coating of organic strontium was successfully prepared.The contact angle test indicated that the hydrophilicity of the organic strontium coating was improved.ICP analysis showed that the content of Sr were 10.21μg and 15.90μg per unit area（cm²）after loading 1wt%and 5wt%SrCl₂.Strontium release experiment indicated that the total release time of Sr was as long as1 month,which promoted the long-term effective osteogenic activity of Sr in vivo.The MTT assay showed that the strontium-loaded samples exhibited good cell viability.SEM cell morphology and fluorescence microscopy images showed the strontium incorporation had promoted the adhesion and extension of MG63 cells.Cell proliferation assay and ALP activity assay also demonstrated that Sr-loading stimulated the proliferation,differentiation of MG63 cells and enhanced ALP activity.（2）TiO₂ nanotubes were fabricated on the surface of titanium by anodization.The organic strontium coating was prepared into the nanotubes by electrostatic adsorption and bond grafting,and chitosan coating was prepared on the surface of TiO₂nanotubes to control the release behaviour of Sr.SEM images showed that the diameter of the nanotubes was about 130nm and the length was about 16μm.A large amount of gelatinous strontium alginate with uniform distribution was formed in the NT tube and the tube gap,and TEM analysis showed that the strontium alginate gel was introduced into the NT tube.The FT-IR spectra also confirmed the successful preparation of the SA coating and the loading of the Sr did not alter the structure of the SA.ICP test showed that TiO₂ nanotubes had a good storage capacity of Sr,and the CS coating loaded on the surface could effectively slow down the release of Sr.MTT showed that the strontium-organic coating had lower cytotoxicity.Fluorescence microscopy images showed that Sr could effectively promote cell adhesion.Cell proliferation and ALP activity studies confirmed that Sr could promote cell proliferation,differentiation and improve the biological activity of TiO₂ nanotubes.In summary,the organic strontium coating on the surface of pure titanium and TiO₂ nanotubes not only slows down the release of strontium up to one month,but also can effectively improve the biological activity of pure titanium and TiO₂nanotubes.This method is expected to widely use in the field of bone repair.