Fig. 5. WT NR6 cell adhesion strength on fibronectin-coated substrates was measured after a 12 hour incubation in serum-free medium to avoid non-specific adsorption of serum-derived adhesion proteins. Cell adhesion depends on ligand density, and monotonically decreases with increasing detachment force. Adhesion is not reinforced on fibronectin surfaces in the absence of serum.