Effects of micropitted/nanotubular titania topographies on bone mesenchymal stem cell osteogenic differentiation

Micro/nanotopographical modification of biomaterials constitutes a promising approach to direct stem cell osteogenic differentiation to promote osseointegration. In this work, titania nanotubes (NTs) 25 and 80 nm in size with the acid-etched Ti topography (AcidTi) and hierarchical hybrid micropitted/nanotubular topographies (Micro/5VNT and Micro/20VNT) are produced to mimic the structure of the natural bone extracellular matrix (ECM). The effects on bone mesenchymal stem cell (MSC) osteogenic differentiation are studied systematically by various microscopic and biological characterization techniques. Cell adhesion is assayed by nucleus fluorescence staining and cell proliferation is studied by CCK-8 assay and flow cytometry. Osteogenic differentiation is assayed by alkaline phosphatase (ALP) expression, collagen secretion, matrix mineralization, and quantitative reverse transcription polymerase chain reaction (qRT-PCR) analysis on the osteogenesis related gene expression. All the topographies are observed to induce MSC osteogenic differentiation in the absence of osteogenic supplements. The nanotube surfaces significantly promote cell attachment and spread, collagen secretion and ECM mineralization, as well as osteogenesis-related gene expression. Among them, Micro/20VNT shows the best ability to simultaneously promote MSC proliferation and osteogenic differentiation. Our results unambiguously demonstrate their excellent ability to support MSC proliferation and induce MSC osteogenic differentiation, especially those with the micropitted topography.