The adhesion of cells to vertically aligned TiO2 nanotubes is reviewed. The attraction between a negatively charged nanotube surface and a negatively charged osteoblast is facilitated by charged protein-mediators like proteins with a quadrupolar internal charge distribution, fibronectin and vitronectin. It is shown that adhesion and spreading of osteoblasts on vertically aligned TiO2 nanotube surfaces depend on the diameter of the nanotubes. Apparently, a small diameter nanotube surface has on average more sharp convex edges per unit area than a large one, leading to stronger binding affinity on its surface.