An atomic-force-microscopy study of the structure of surface layers of intact fibroblasts

Intact embryonic fibroblasts on a collagen-treated substrate have been studied by atomic-force microscopy (AFM) using probes of two types: (i) standard probes with tip curvature radii of 2–10 nm and (ii) special probes with a calibrated 325-nm SiO$_2$ ball radius at the tip apex. It is established that, irrespective of probe type, the average maximum fibroblast height is on a level of $\sim$1.7 $\mu$m and the average stiffness of the probe–cell contact amounts to $\sim$16.5 mN/m. The obtained AFM data reveal a peculiarity of the fibroblast structure, whereby its external layers move as a rigid shell relative to the interior and can be pressed inside to a depth dependent on the load only.