Characterization and osteogenic activity of SrTiO3/TiO2 nanotube heterostructures on microporous titanium

Abstract

Surface properties such as physicochemical characteristics and topographical parameters are important considerations in the design of implant materials, as they determine interactions with living cells and tissues. Micro-/nanostructurization of Ti surfaces can enhance osteointegration, and strontium (Sr) is able to decrease osteoresorption. Sr loaded micro/-nanotubular structures that allow controlled and long-term Sr release are expected to yield favorable osteogenic effects. In this work, we constructed SrTiO3/TiO2 nanoparticle-nanotube heterostructures on a microporous titanium (Ti) surface and characterized their properties. Ti plates were etched with acid to create a micro-rough surface (M) 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) for 1 or 3h to obtain SrTiO3/TiO2 nanotube heterostructures with different Sr contents. The in vitro biocompatibility of MN-Sr was investigated by evaluating protein adsorption, using osteoblast and osteoclast (RAW 264.7 cell) cultures. The micro-/nanostructured porous samples (MN and MN-Sr) promoted protein adsorption owing to their large specific surface area and high reactivity; the amount of protein adsorbed onto MN-Sr was independent of Sr content. Sr in SrTiO3/TiO2 heterostructures exhibited controllable and sustained Sr2+ ion release in phosphate-buffered saline. Moreover, heterostructures with an appropriate SrTiO3 content promoted osteoblast adhesion, proliferation and differentiation, and inhibited osteoclast proliferation and differentiation. These results indicate that the micro-/nano heterostructure with an appropriate content of Sr has excellent osteogenic activity and anti-bone resorption ability.