Titania-hydroxyapatite nanocomposite coatings support human mesenchymal stem cells osteogenic differentiation

In addition to mechanical and chemical stability, the third design goal of the ideal bone-implant coating is the ability to support osteogenic differentiation of mesenchymal stem cells (MSCs). Plasma-sprayed TiO2-based bone-implant coatings exhibit excellent long-term mechanical properties, but their applications in bone implants are limited by their bioinertness. We have successfully produced a TiO2 nanostructured (grain size < 50 nm) based coating charged with 10% wt hydroxyapatite (TiO2-HA) sprayed by high-velocity oxy-fuel. On Ti64 substrates, the novel TiO2-HA coating bond 153x stronger and has a cohesive strength 4x higher than HA coatings. The HA micro- and nano-sized particles covering the TiO2-HA coating surface are chemically bound to the TiO2 coating matrix, producing chemically stable coatings under high mechanical solicitations. In this study, we elucidated the TiO2-HA nanocomposite coating surface chemistry, and in vitro osteoinductive potential by culturing human MSCs (hMSCs) in basal and in osteogenic medium (hMSC-ob). We assessed the following hMSCs and hMSC-ob parameters over a 3-week period: (i) proliferation; (ii) cytoskeleton organization and cell-substrate adhesion; (iii) coating-cellular interaction morphology and growth; and (iv) cellular mineralization. The TiO2-HA nanocomposite coatings demonstrated 3x higher hydrophilicity than HA coatings, a TiO2-nanostructured surface in addition to the chemically bound HA micron-and nano-sized rod to the surface. hMSCs and hMSC-ob demonstrated increased proliferation and osteoblastic differentiation on the nanostructured TiO2-HA coatings, suggesting the TiO2-HA coatings nanostructure surface properties induce osteogenic differentiation of hMSC and support hMSC-ob osteogenic potential better than our current golden standard HA coating. Published 2011 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 98A: 576-588, 2011.