Dynamic cell behavior on synthetic hydrogels with different charge densities

A series of polyNaSS-co-DMAAm) hydrogels with zeta potentials (zeta) in the range -8.8--20.5 mV and a constant Young's modulus E) of ca. 200 kPa were designed for studying the effect of the charge density of hydrogels on dynamic cell behavior. The zeta was adjusted by tuning the molar friction of negatively charged sodium p-styrene sulfonate NaSS) contained in the monomer mixture [ NaSS and N, N-dimethyl acrylamide DMAAm)] for gelation. A critical zeta potential, which controls cell behavior, zeta(crit) = -14.0 mV, was observed. When zeta > zeta(crit), the cells exhibited a small spreading area, fast migration velocity, and a large migration distance, with concurrent deficiency in actin fibers and less prominent focal adhesions. Conversely, when zeta <= zeta(crit), the cells exhibited a large spreading area, slow migration velocity, and a short migration distance, with concurrent well-developed actin fibers and prominent focal adhesions. Furthermore, cells repeatedly oscillated in a stick-slip mode from a spreading shape to a round shape on the hydrogels with zeta > zeta(crit), although were unable to proliferate. The cell behavior is well correlated with the adsorbed fibronectin on the hydrogel surfaces.