ECM spreading behaviour on micropatterned TiO2 nanotube surfaces.

By electrochemical anodization, highly ordered nanotubular TiO(2) structures were formed on titanium surfaces with diameters of 15 and 100 nm. In previous work we showed that 15 nm tubes strongly enhanced adhesion and vitality of many cell types, whereas on 100 nm diameter tubes the induction of apoptosis was observed. In the present work we produce mixed (15 nm contrasted with 100 nm) nanotube microstructures that combine highly defined micro- and nanostructures using a photolithographic approach to achieve a direct comparison of adhesion and spreading of mesenchymal stem cells on different diameter nanotubes present on a single surface. On these coupled different nanoscale surfaces mesenchymal stem cell adhesion is initially favoured on 15 nm tube areas but, with time, a gradient in cell number and shape to the "unfavourable" regions of the substrate (100 nm tubes) can be observed. This can be explained by cells on the "favourable" 15 nm regions that strongly produce and shed extracellular matrix onto the "unfavourable" locations. These findings contribute to the design of cell guiding surfaces, but also demonstrate the need for a long-range defined homogeneous order when studying cell behaviour on nanostructured surfaces.