Titanium (Ti) and its alloys have been widely used in clinics as preferred materials for bone tissue repair and replacement. However, the lack of biological activity of Ti limits its clinical applications. Surface modification of Ti with bioactive elements has always been a research hotspot. In this study, to promote the osseointegration of Ti6Al4V (Ti64) implants, calcium (Ca), oxygen (O), and phosphorus (P) codoped multifunctional micro−nanohybrid coatings were prepared on a three-dimensional (3D) printed porous Ti64 surface by microarc oxidation (MAO) and a hydrothermal method (HT). The surface morphologies, chemical compositions, and surface/cell interactions of the obtained coatings were studied. In vitro experiments indicated that all hybrid coating-modified Ti64 implants could enhance protein adsorption and MC3T3 osteoblasts' activity, adhesion, and differentiation ability. In vivo experiments showed that the hybrid coating promoted early osseointegration. By comparison, microarc oxidation-treated Ti64 (M-Ti) has the best biological activity and the strongest ability of osseointegration. It provides important theoretical significance and potential application prospects for improving the biological activity of Ti implants.

Bioinspired by the morphology of osteoclast-resorbed bone surfaces, we prepared a calcium-doped titanium phosphate (Ca-TiP) coating, which consists of a nanofibrous network, on titanium (Ti) substrate via a simple two-step hydrothermal method, trying to mimic natural bone compositionally and microstructurally. The in vitro studies show that the Ca-TiP coating with synergistic features of nanofibrous biomimetic topography and surface chemistry could elicit intensively osteogenic behavior and responses including enhanced cell adhesion, spreading, and proliferation as well as alkaline phosphatase (ALP) activity and up-regulated expression of bone-related genes, which inevitably benefit the formation of new bone and the quality of osseointegration. When the two control groups are compared in vivo, the significantly improved new bone formation in the early stage and the much stronger interfacial bonding with the surrounding bone for Ca-TiP coating suggest that Ca-TiP coating modified Ti implants hold great potential for orthopedic and dental applications.

In this study, a series of hierarchical micro/nanoscaled titanium phosphate (TiP) coatings possessing various surface morphologies were successfully fabricated on titanium (Ti) discs. The hydrothermal reactions of Ti discs in hydrogen peroxide (H 2 O 2 ) and phosphoric acid (H 3 PO 4 ) mixed solution yield diverse topographies such as hemispheric clump, cylindrical rod, spherical walnut, micro/nano grass, micro/nano sheet, and fibrous network. And their crystal structures were mainly composed of Ti(HPO 4 ) 2 $0.5H 2 O, (TiO) 2 P 2 O 7 , H 2 TiP 2 O 8 , Ti(HPO 4 ) 2 and TiO 2 . The morphology and crystal shape of the TiP coatings depend strongly on the mass ratio of H 2 O 2 /H 3 PO 4 , reaction temperature and water content. Besides, the formation mechanism of TiP coatings with diverse morphologies was explored from the perspective of energetics and crystallography. The mechanism exploration paved the way for custom-making TiP coatings with desirable micro/nanoscaled morphologies to meet specific application purposes. The in vitro cytological performances of TiP coatings were also evaluated by co-culturing with rat bone marrow stromal cells (BMSCs), demonstrating a positive prospect for their use in bone tissue engineering.