Physicochemical properties and platelet interactions of segmented polyurethanes containing sulfonate groups in the hard segment

The adhesion of platelets to a series of segmented polyurethanes having sulfonate groups in the hard segment is reported. The polyurethanes were synthesized using sulfonated chain extenders of different structure. Analogous control materials without sulfonate groups also were studied. Adhesion was measured in vitro using washed human platelets in a carrier fluid consisting of Tyrode's buffer with apyrase, albumin, and red cells at normal concentration. The polymers were characterized by gel permeation chromatography and elemental analysis. Water absorption and thermal transitions also were determined. It was found that the sulfonated materials absorb significant amounts of water while the nonsulfonated analogs do not. The surfaces of polymer films were characterized by water contact angle and XPS. The contact angles of the sulfonated surfaces were relatively low. Platelet adhesion to the sulfonated polymers was found to be very high compared to the nonsulfonate analogs. The local environment of the sulfonate groups (different chain extenders) also appears to have an effect on platelet interactions. Albumin adsorption was high on all the materials and was not correlated with platelet adhesion. It appears from this work that platelets may have a binding site that is specific for sulfonate groups.