Size selective behavior of mesenchymal stem cells on ZrO2 and TiO2 nanotube arrays

This work reports on the behavior of mesenchymal stem cells on anodic ZrO2 nanotube layers grown by a self-ordering process on zirconium with defined diameters between 10 and 50 nm. It is demonstrated that mesenchymal stem cells show a size-specific reaction to these nanoscale patterned surfaces. We compare the behavior on these ZrO2 nanotubes to findings on TiO2 nanotubes of different diameters. For both nanotube materials, TiO2 and ZrO2, cell adhesion and spreading are enhanced for nanotube diameters of similar to 15-30 nm, while a strong decay in cell activity is observed for diameters > 50 nm. Focal complex formation on adherent cells is selectively modulated by the specific nanoscale. Moreover, even if the surface chemistry of the nanotubes is completely modified with a dense AuPd coating onto the formed nanotube layers, or the length of the nanotubes is varied, the observed nano size effects still prevail. This demonstrates how strong the pure geometric diameter dependence in the range between 15 and 100 nm dominates over other possible effects on cell activity.