Sulphonated polystyrene as an optimal substratum for the adhesion and spreading of mesenchymal cells in monovalent...

Cell adhesion and spreading were studied on sulphonated polystyrene dishes in serum-free saline (Mn, Na, Cl, buffer) i.e., without an intervening protein layer. Spreading as a function of surface charge density, SCD, peaked around 2-10 negative charges per square nanometer, corresponding to a monomolecular layer of sulphonate ions. At optimal SCD, macrophages, BHK-C13 and whole mouse embryo secondary cells all showed considerable spreading, even in monovalent saline-more so than on a conventional tissue-culture surface. But outside this narrow range of SCD, or on protein-coated surfaces, the divalent cation was indispensable. The biphasic effect of sulphonation on cell adhesion is consistent with the theory that a substratum need not be biochemically specific, provided it is physiochemically polar, rigid and dense. According to this theory, polystyrene of sub-optimal SCD would not be sufficiently polar, while supra-optimal sulphonation would produce a hydrogel surface, lacking in local rigidity and density, due to osmotic swelling. The principle of polymer exclusion, by a surface hydrogel layer, is also consistent with observations on the inhibitory effects of adsorbed proteins-viz., albumin, collagen, serum and cellular exudate, respectively-contrasted with the ready attachment of cells to a bare, optimally charged substratum, in this minimal in vitro system.