Título: Subtle variations in polymer chemistry modulates substrate stiffness and fibronectin activity
Autor: Brizuela Guerra, Nayrim; González-García, Cristina; Llopis, Virginia; Rodriguez-Hernandez, Jose Carlos; Moratal, David; Rico Tortosa, Patricia María; Salmerón Sánchez, Manuel
Resumen: [EN] A family of polymer substrates which consists of a vinyl backbone chain with the side groups
¿COO(CH2)xCH3, with x ¿ 0, 1, 3, 5 was prepared. Substrates with decreasing stiffness, characterised
by the elastic modulus at 37 C, and similar chemical groups were obtained. Firstly, we have
investigated whether these minute variations in polymer chemistry lead to differences in fibronectin
(FN) adsorption: the same FN density was obtained on every substrate (450 ng cm2
) but the
supramolecular organisation of the protein at the material interface, as obtained with AFM, was
different for x ¿ 0 and the other surfaces (x ¿ 1, 3, 5). Consequently, this allows one to use a set of
substrates (x ¿ 1, 3, 5) to investigate the effect of substrate stiffness on cell behavior as the unique
physical parameter, i.e. after ruling out any influence of the length of the side group on protein
conformation. Moreover, the importance of investigating the intermediate layer of proteins at the cellmaterial
interface is stressed: the effect of x ¿ 0 and x ¿ 1 on cell behavior cannot be ascribed to the
different stiffness of the substrate anymore, since the biological activity of the protein on the material
surface was also different. Afterwards, initial cellular interaction was investigated using MC3T3-E1
osteoblasts-like cells and focusing on actin cytoskeleton development, focal adhesion formation and the
ability of cells to reorganize the adsorbed FN layer on the different substrates. Image analysis was used
to quantify the frequency distribution of the focal plaques, which revealed broader distributions on the
stiffer substrates, with formation of larger focal plaques revealing that cells exert higher forces on stiffer
substrates.
