Nanosize and Vitality: TiO2 Nanotube Diameter Directs Cell Fate

Abstract

We generated, on titanium surfaces, self-assembled layers of vertically oriented TiO₂ nanotubes with defined diameters between 15 and 100 nm and show that adhesion, spreading, growth, and differentiation of mesenchymal stem cells are critically dependent on the tube diameter. A spacing less than 30 nm with a maximum at 15 nm provided an effective length scale for accelerated integrin clustering/focal contact formation and strongly enhances cellular activities compared to smooth TiO₂ surfaces. Cell adhesion and spreading were severely impaired on nanotube layers with a tube diameter larger than 50 nm, resulting in dramatically reduced cellular activity and a high extent of programmed cell death. Thus, on a TiO₂ nanotube surface, a lateral spacing geometry with openings of 30−50 nm represents a critical borderline for cell fate.