EFFECT OF POLYOL HYDROPHILICITY ON THE STRUCTURE AND ANTICOAGULANT ACTIVITY OF WATER-SOLUBLE SULFONATED POLYURETHANES

The effect of polyol hydrophilicity on the hemocompatibility of sulfon ated polyurethanes has previously been investigated. Polyurethanes bas ed on polytetramethylene oxide (PTMO), a relatively hydrophobic polyol , have strong antithrombogenic properties, showing little platelet dep osition or activation, yet high fibrinogen deposition in a canine ex v ivo blood-contacting model. However, sulfonated polyurethanes based on polyethylene oxide (PEG), a more hydrophilic polyol, do not show the same antithrombogenic effects, By increasing the level of ionization, both of these polyurethanes are soluble in aqueous solutions, The anti thrombotic effect seen for the insoluble polymers is reflected in stro ng anticoagulant activity for the soluble polyurethanes. Anticoagulant effects are tested in thrombin time, activated partial thromboplastin time, prothrombin time, and reptilase time tests. The anticoagulant e ffect is shown to be about an order of magnitude stronger for soluble polyurethane based on PTMO than for that based on PEG. This is hypothe sized to be due to differences in the solution-phase structure between the two types of polyurethanes. This structure is probed using an 8-a nilinonaphthalene sulfonic acid, an amphiphilic fluorescent probe, to determine if hydrophobic regions exist. Capillary viscometry and stati c light scattering are also used to investigate the structure of these materials in solution, The more hydrophobic polyurethane is shown to form micellar structures, whose molecular weight and radius of gyratio n are affected only slightly by increasing concentrations of polymer o r added salt, For the more hydrophilic polyurethane, however, the appa rent molecular weight and radius of gyration appear to be sensitive to both polymer and salt concentrations, a behavior that is strongly dom inated by the ionic interactions. (C) 1996 Academic Press, Inc.