Surface-modified titanium (Ti) and titanium alloys with physical topography and bioactive components mimicking those of bone tissues have attracted increasing interest as biomaterials for accelerating osseointegration. In this study, an enzyme-mediated mineralization system containing an organic phosphate is used to form a coating of calcium phosphate on titanium dioxide (TiO2) nanotubes heat-Treated at different temperatures (350, 450, and 550 °C). Surface characterization using analytical techniques shows that this system can lead to the deposition of an amorphous calcium phosphate layer on the TiO2 nanotube (TNT) surface while preserving the original nanotopography. In this respect, the heat treatment of TNT plays an essential role in the formation of the calcium phosphate layer, with TNT annealed at 450 °C having the best mineralization results. The synergistic effect of the TNT topography and chemical cues of the calcium phosphate layer improves adhesion, proliferation, and differentiation of pre-osteoblasts in vitro when compared with surfaces with only one of these features. This hybrid coating can thus potentially enhance the osseointegration of titanium-based implants.
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In this study, we fabricated TNT with different heat treatments (350, 450, and 550 °C). A coating of calcium phosphate was successfully introduced onto the TNT, while preserving their original nanomorphology by using enzyme-mediated mineralization. Among the TNT annealed with different temperatures, those heated at 450 °C were more conducive to the formation of a calcium phosphate coating. In vitro cell experiments showed that the TNT provided desirable nanoscale topography for cell adhesion and spreading. In addition, the amorphous calcium phosphate coating afforded biochemical stimulus for the proliferation and differentiation of pre-osteoblasts. Therefore, the combination of the nanostructures of TNT with a bioactive calcium phosphate coating provided a favorable extracellular microenvironment for the necessary cell responses when compared with surfaces containing one of these features only. This study provided a platform for the fabrication of new biomaterials that can improve osteointegration. J.Y.’s participation in this project was supported by the National Natural Science Foundation of China (NCFC 81628005) and Medical Scientific Research Foundation of Guangdong Province of China (200001). J.Y. also received a 3Mgives Key-Opinion-Leaders Scholarship to support her visit to the Minnesota Dental Research Center for Biomaterials and Biomechanics (MDRCBB). The authors declare no competing financial interest.