Regulation by sulphonate groups of complement activation induced by hydroxymethyl groups on polystyrene surfaces

Reducing the complement-activating capacity of a polymer surface is important in improving its blood compatibility. Polystyrene surfaces bearing hydroxymethyl (CH2OH) groups activate the alternative pathway of complement. This activation depends strongly on the density of the groups. Polystyrene surfaces bearing sulphonate (SO3-) groups adsorb proteins, resulting in an apparent activation. Polystyrene surfaces bearing both types of groups in close proportions are not activators in human serum, due to the adsorption of a protein of the alternative pathway, which has a protecting effect, not found when a polymer surface bearing hydroxyl groups is mixed in serum with another polymer surface bearing SO3- groups. In the presence of purified proteins of alternative pathway, C3 convertase activity can be created on each of these surfaces by deposition of C3b, but their susceptibility to inactivation by regulatory proteins H and I depends on the types of chemical groups present on the surface and whether the surfaces were passivated or not before C3b deposition.