Preparation And Biocompatibility Of Nano Structured Strontium-oxide Layer On Titanium Surface Made By Hydrothermal Treatment

Last century, the "osseointegration" investigated by professor Branemark inducted the surface modification of implant for researchers all over the world in the field of oral implant. Improving the osteoconduction and osseointegration of biomedical titanium has been the main purpose to pursue. Strontium, a potential ion, was proved to increase bone formation and decrease resorption. Our group optimized the production of nano-structured strontium permeated into titanium oxide surface using hydrothermal technique and evaluated the biological characterization properties and response of bone mesenchymal stem cells (BMSCs) in vivo in early stage.Objective:1. Detect the characterization of Sr containing titanium oxide surface prepared by hydrothermal treatment in the series of parameters and confirme the nanostructure evolution.2. Investigate the proliferation, differentiation and osteogenesis of MC3T3-E1and BMSCs cultured on Sr containing surface and Mod Ti.3. In vivo experiments were used to evaluate the response of peri-implant tissues and BMSCs. Methods:1. A series concentration of Sr(OH)2solution was used for hydrothermal treatment at different temperature and time. Optimization of the solution, temperature, heating time and subsequent characterization of the hydrothermal derived oxide titanium layers were carried out using FESEM, TFXRD, XPS, contact angle measurement and TEM.2. We evaluated the MC3T3-E1and BMSCs response by initial adhesion, proliferation, alkaline phosphatase (ALP), osteocalcin (OC), osteogenesis related genes and calcium mineralization in vitro.3. Implants were implanted into proximal tibia of SD rats. After6days, the implants were unscrewed for SEM observation. H&E staining and immunohistochemistry analysis with Stro-1antibody on tissue adjacent to implants were used to evaluate the ability of bone healing and BMSCs recruiting in vivo.Results1. The concentration, heating temperature and time affected the surface morphology significantly and varied the composition and phase of surfaces.2. The Sr containing surface could release Sr for more than one week, which promoted the differentiation of cells, up regulated osteogenesis related genes, increased extracellular matrix mineralization(P<0.05) and eventually enhanced the osteogenesis in vitro.3. The unscrewed implants were covered with quite organized mesh formed by discrete and small bundles of collagen and transitory hematoma in adjacent bone tissue by H&E staining. The Stro-1labeled MSCs were observed noticeably around Sr containing implants in immunohistochemistry analysis (P=0.0125).Conclusions:1. The hydrophilic micro/nano-structured strontium-containing oxide surface could be obtained under the best parameter (0.02M Sr(OH)2,220℃,12h) and this surface showed improvement on cell differentiation and osteogenesis in vitro.2. This Sr containing surface had a potential ability to enhance early osseointegration as it could also recruit rat Stro-1positive MSCs to peri-implant tissue in vivo.