Tailoring the nanostructured surfaces of hydroxyapatite bioceramics to promote protein adsorption, osteoblast growth, and osteogenic differentiation.

To promote and understand the biological responses of the implant via nanostructured surface design is essential for the development of bioactive bone implants. However, the control of the surface topography of the bioceramics in nanoscale is a big challenge because of their brittle property. Herein, the hydroxyapatite (HAp) bioceramics with distinct nanostructured topographies were fabricated via hydrothermal treatment using α-tricalcium phosphate ceramic as hard-template under different reaction conditions. HAp bioceramics with nanosheet, nanorod and micro-nanohybrid structured surface in macroscopical size were obtained by controlling the composition of the reaction media. Comparing with the traditional sample with flat and dense surface, the fabricated HAp bioceramics with hierarchical 3D micro-nanotextured surfaces possessed higher specific surface area, which selectively enhanced adsorption of specific proteins including Fn and Vn in plasma, and stimulated osteoblast adhesion, growth, and osoteogenic differentiation. In particular, the biomimetic features of the hierarchical micro-nanohybrid surface resulted in the best ability for simultaneous enhancement of protein adsorption, osteoblast proliferation, and differentiation. The results suggest that the hierarchical micro-nanohybrid topography might be one of the critical factors to be considered in the design of functional bone grafts.