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Modified layers with multiscale structures have been extensively explored and rationally designed on Ti-based orthopedic implants recently, since the remarkable improvement of biomedical properties. In consideration of the inefficiency, costliness and waste products of existing technologies, herein, we proposed the ultrasonic shot peening and induction heating protocol to construct the micro-nano complex oxide structures on Ti6Al4V in term of its advantages of environmental friend, rapid heating, low-cost and easy to process. With the USP pretreatment and induction heating, the nonuniform oxide crystallites firstly appeared on smooth surface and successfully grow up into the well-distributed TiO 2 nanocrystallites, and transformed to netlike structures with submicro-sized worms when subjected to high-power of shot peening, which was significantly influenced by the microstructural evolution of alloy matrix. The submicro/nano-structured oxide layers mainly contained rutile/anatase TiO 2 and little Al 2 O 3 between grain boundaries, successively enhanced the surface roughness and wettability, and tended to form the hydrophilic surfaces. The adhesion strength of the oxide layers to substrates and hardness were also distinctly increased with increasing the IHT period from 20 to 35 s. In vitro BMSCs culturing proved that the prepared submicro/nano-scale oxide layers possessed favorable cell adhesion and proliferation, and further improved the osteogenic differentiation. The novelty of this work was to explored the evolution law of submicro-and nano-scale structures in osteogenic differentiation, and further better clinical application of Ti-based biomaterials. Image 1 • Ultrasonic shot peening and induction heating treatment were jointly proposed. • Microstructure evolution of alloy matrices promoted structure transformation of oxide layers. • Surface roughness, wettability and hardness were markedly improved. • Nano/submicro-structured oxide layers possessed good stem cell compatibility. • Oxide layers with multi-structures further promoted osteogenic differentiation of BMSCs. [ABSTRACT FROM AUTHOR]

Current development of nano/microscale modification technology of Ti-based implants was focused on the acceleration of ossification and consequent reduction of immunological rejection after implantation. Here, we rationally designed and produced the multistructures with microscale etched pits and nanodot-like oxide crystallites using, a two-step method, HF/HCl etching and induction heating treatment (IHT). IHT oxidation achieved the initially generating of nanocrystallites on the microscale surface and continually growing into dense spherical particles. The dual-scale oxide structures mostly contained rutile-TiO 2 with mixture thickness of 402 nm, and remarkably improved the surface wettability with surface roughing. The oxide multistructures showed favorable osteogenic differentiation of human bone marrow-derived mesenchymal stem cells with promoting expressions of osteogenesis-related genes (ALP, Runx2, OCN and COL-1) and proteins. Otherwise, it practically confirmed that the stem cells owned relatively weak 24 h cell adhesion and proliferation on the special oxide structures via comparation with histiocytic types (ST2 cells), and the samples acquired better cell fates when oxidized for 30 s than 20 s due to the larger surface roughness and better hydrophilicity. This study provided theoretical and experimental foundations for construction and further clinical application of high-performance bone implants with multistructures. Unlabelled Image • Oxide layers with microscale etched-structures and nanodot-like oxide crystallites were rapidly prepared by A + IHT protocol. • A + IHT approach increased the roughness value, and improved the hydrophilicity and adherence strength of oxide layers. • The micro/nanoscale oxide structures advanced proliferation and osteogenic differentiation of BMSCs without cytotoxicity. • Stem cells had different osteogenic behaviors with weak cell attachment and growth patterns compared to the histiocytic types. [ABSTRACT FROM AUTHOR]