Micro- and Nanohemispherical 3D Imprints Modulate the Osteogenic Differentiation and Mineralization Tendency of Bone Cells

Surface topography has been reported to play a key role in modulating cell behaviors, yet the mechanism through which it modulates these behaviors is not fully understood, especially in the case of three-dimensional (3D) topographies. In this study, a series of novel hemispherical 3D imprints ranging from the nanoscale to the microscale were prepared on titanium (Ti) surfaces using a customized interfacial lithography method. Mouse embryo osteoblast precursor cells (MC3T3-E1) were selected to investigate the solitary effect of specific hemispherical 3D imprints on cellular behaviors. The results indicated that varied hemispherical 3D imprints can affect the formation of filopodia and the arrangement of the cytoskeleton in different ways. Specifically, they can alter the spreading morphologies of cells and lead to deformation of the nucleus, which eventually affects cell proliferation and osteogenic differentiation. Cells cultured on different hemispherical 3D imprints exhibited promoted proliferation and osteogenic differentiation to different degrees; for example, cells cultured on 90 and 500 nm hemispherical imprints formed abundant filopodia and exhibited the highest alkaline phosphatase activity and osteogenic gene expression, respectively. Four-week tibia implantation also confirmed that 90 nm hemispherical imprints improved the osteogenic ability in vivo compared with an unpatterned Ti substrate. In addition to promoted proliferation, colonization of more cells on the surface of implants and induction of rapid osteogenic differentiation can occur. Our work provides a rational way to balance cell proliferation and differentiation, which can accelerate bone integration of an implant and host tissue.