| Although Ti and its alloys are widely used in biomedical applications due to their excellent biocompatibility,artificial bone substitutes are still limited by inadequate osseointegration. As such,new types of implant material are needed that have greater biocompatibility and osseointegration through advanced surface design and modification. Micro-/nanostructurization of Ti surfaces can promote osteointegration, and strontium (Sr) is able to decrease osteoresorption and enhance osseointegration. The anti-osteoporosis drug strontium ranelate (SR) which exhibits significant effects has aroused extensive clinical focus by oral. However, oral administration exists the potential deleterious effects. The reseach of constant in situ Sr release on implant-tissue interface is important but shortage. Sr loaded micro/-nanotubular structures that allow controlled and long-term Sr release are expected to yield favorable osteogenic effects in this paper. This study describes the fabrication of SrTiO3/TiO2 nanoparticle-nanotube heterostructures on a microporous titanium (Ti) surface. Ti plates were etched with acid to create a micro-rough surface and then anodized to generate a surface layer of TiO2 nanotubes(MN). Strontium (Sr) was loaded onto MN by hydrothermal treatment in Sr(OH)2 solution(MN-Sr) to obtain SrTiO3/TiO2 composites with different Sr contents. In addition, as a control, TiO2 nanotubes on flat Ti plateswere fabricated by anodization (N). Herein, protein adsorption was used to compare the bioactivities of five samples with different morphology and components, and the osteoblast and osteoclast cultures were conducted to evaluate and compare the osteogenic ability.The diameter of micropores on the Ti surface ranged from 10-20 ?m and the pores were interconnected by acid etching . MN retained the original micropores of M but also had new nanotubes with 100 nm tube diameter in the walls and at the bottom of the micropores after anodization, which formed a micro/nanoporous TiO2 layer. After 450? heating treatment, the crystal structure of TiO2 transformed from amorphous to anatase. MN was used as reactant and template to react with Sr(OH)2 by hydrothermal treatment to obtain micro-nanostructured SrTiO3/TiO2 layer. After 65 days of immersion in PBS, the cumulative percentage of Sr2+ released from MN-Sr1h and MN-Sr3h was 10% and 17%, respectively.The release rate decreased with longer culture times. We predict that Sr release from MN-Sr can last for longer than 1 year. The five samples, including M, N, MN, MN-Sr1h and MN-Srlh samples were respectively immersed in minimum essential medium alphacontaining 10%fetal calf serumto investigate the ability of protein adsorption. MN, MN-Sr1h, and MN-Sr3h had similar micro-/nanostructure morphology and adsorbed near-equivalent amounts of protein. Sr loaded on MN had no effect on protein adsorption capacity despite alterations in surface chemistry.After the test of cell culture, The ability of cells (osteoblast and osteoclast) proliferation and differentiation on MN surfaces is better than that of N and M, because the surface morphology of the samples has a certain influence on the proliferation and differentiation of osteoblasts, related to the specific surface area and surface energy. MN-Srlh and MN-Sr3h had the same morphological structure. The effect on osteoblast proliferation and differentiation of MN-Srlh was better than that of MN-Sr3h. The inhibitory effect of MN-Srlh on osteoclast proliferation and differentiation was worse than that of MN-Sr3h, but MN-Sr3h could inhibit osteoblast proliferation and differentiation. In summary, an appropriate amount amount of SrTiO3 in the micro-nanotube heterostructures can promote the induction of bone formation. |
PDF Full Text Request