Enhanced Osteointegration of Hierarchical Structured 3D-Printed Titanium Implants

Three-dimensional (3D) printing technology has been widely used to fabricate of various titanium and its alloy implants. However, engineering the 3D printing nanoscaled feature to realize a hierarchical micronano structured surface topography still remains a challenge. On one hand, enhanced bioactivity is always expected on micronano-hybrid biomimetic topography; on the other hand, a typical functional protein in extracellular matrix (ECM) is nanoscaled; therefore, nanoscaled features might affect its binding to specific receptor and subsequent cell response. Here, we engineered a novel hierarchical structure with microparticles and rutile TiO2 nanorods topography that fabricated by 3D printing of pure titanium followed by a hydrothermal process. Although there was no difference on the microscaled feature before/after nanonization, cellular behaviors including adhesion, proliferation, and osteogenic differentiation of mesenchymal stem cells (MSCs) were significantly upregulated on the hierarchical micronano structured topography. Moreover, we demonstrated that the distinct conformation of the initially fibronectin proteins adsorbed on nanorods was more beneficial to cellular adhesion. In vivo test in a rabbit femur model also demonstrated the favorable for new bone formation on the novel hierarchical micronano structured implant–bone interface. These results therefore suggest that the hierarchical micronano structured topography might be a promising surface feature for the new generation of bone implants.