The Characterization a nd Osteogenic Activity of Nanostructured Strontium-Containing Oxide Layers on Titanium Surfaces

Purpose: The aim of this study was to compare strontium-containing implant (Sr-Ti) surfaces with modified pure Ti (Mod Ti) on the promotion of osteogenesis in vitro and in vivo. Materials and Methods: The Sr-Ti surfaces were fabricated by hydrothermal treatment. The Mod Ti surfaces were used as a control. These surfaces were characterized with scanning electron microscopy, x-ray diffractometer, and x-ray photoelectron spectroscopy. The biologic activity was analyzed by initial adhesion, proliferation, alkaline phosphatase (ALP), osteocalcin, and osteogenesis-related genes in vitro. Hematoxylin and eosin (H&E) staining and immunohistochemistry analysis of tissue adjacent to this implant were used to evaluate osteogenic activity in vivo. Results: The results confirmed multiple nanogranules on the Sr-Ti surface composed of well-crystallized TiO2 and SrTiO3 phases. Long-term release of Sr enhanced mesenchymal stem cell (MSC) initial adhesion, the production of ALP, osteocalcin, and upregulated osteogenesis-related genes. For in vivo osteogenic evaluation, mesenchymal-like cells were adhered on these two surfaces under the electron microscope and transitory hematoma in adjacent bone tissue by H&E staining. The Stro-1-labeled MSCs were noted around the Sr-Ti surface in immunohistochemistry analysis. Conclusion: This study suggests that Sr-Ti surfaces with nanostructures could promote the response of MSCs in vitro, and recruit Stro-1 labeled MSCs in vivo. Keywords: hydrothermal treatment, mesenchymal stem cells, nanostructure, osseointegration, strontium, titanium