Figure 3.

Illustration of cell–nanotopography interactions. Different combinations of feature sizes and depths might reduce the surface available for the cell membrane to establish adhesions. Looking at the pattern from the cell side, five integrins are necessary to connect the cytoskeleton to the extracellular environment [69], which requires integrin clusters of approximately 40 nm. Therefore, topographic features exceeding this dimension can be recognized by cells as ‘adhesive’. From the material side, ligand spacings below 60 nm proved to be sufficient to ensure cell-substrate binding [37]. In this case, inter-feature size exceeding this dimension might impair the formation of adhesive complexes. Moreover, surfaces are generally coated with serum proteins, which account for a macromolecular layer of 20–30 nm. Therefore, in order to make a surface not available for the establishment of cell adhesions, this has to be at least 40 nm away from the cell membrane, which comprises the distance of the protein layer and the extracellular domain of the integrins (H, height; FS, feature size; IF, inter-feature dimension). (Online version in colour.)