Michael D. Lelah

Polyether-urethane ionomers: surface property/ex vivo blood compatibility relationships

Abstract The effect of incorporation of ions into polyurethanes on their interfacial interaction with blood is of interest because of the relative blood compatibility of polyurethanes, and the effect of ionic domains on surface properties and thus blood response. A series of uncharged, anionic, cationic, and zwitterionic polyetherurethanes was coated on tubing surfaces, and their blood response determined using an ex-vivo canine series shunt experiment. The results showed the polyurethane zwitterionomer and anionomer to be more thromboresistant than the uncharged polyurethane. The polyurethane cationomer was the most thrombogenic material studied. A comparison between two uncharged polyurethanes of different hard segment content showed that surface soft segment concentration correlated with thromboresistance. Multiprobe surface characterization using contact angle measurements, ESCA, ATR-IR, and SEM were used to obtain surface property information on the materials studied. The thromboresistance of the zwitterionomer and the anionomer was related to a high concentration of the mobile side chain ionic sulfonate group at the surface. Ionic mobility at the interface appears to strongly influence the blood response of these materials. Ionization of polyurethanes is thus a useful technique to both improve blood compatibility and study the role of surface chemistry in artificial surface-induced thrombosis.

Blood Compatibility of Polyethylene and Oxidized Polyethylene in a Canine A-V Series Shunt:Relationship to Surface Properties

The contact of blood with a polymer surface results in the initial deposition of proteins, platelets, and other formed elements. Proteins deposit during the first moments of blood contact1, while platelets start to adhere after about one minute of blood contact, when the protein layer is about 200 A thick2. The polymerization of fibrinogen to fibrin, and the activation and aggregation of platelets, lead to thrombus formation and growth on the artificial surface.

Characterization of Polyurethanes for Blood-Contacting Applications

Segmented polyurethanes are widely used in commercial and experimental blood-contacting applications which include vascular prostheses, blood filters, catheters, insulation for pacemaker leads, heart valves, cardiac assist devices, and chambers for artificial hearts. The use of this family of polymers for such applications is due to the physiological acceptability, relatively good blood tolerability, relative stability over extended implant periods, and excellent physical and mechanical properties that are exhibited by these materials1.