Polycarbonate urethane films modified by heparin to enhance hemocompatibility and endothelialization

Polyurethane with pendant carboxyl groups was synthesized by a two‐step reaction using methylene diphenyl diisocyanate as hard segments, polycarbonate diols as soft segments and 2,2‐bis(hydroxymethyl) propionic acid as chain extenders. The surfaces of the casting polymer films were further covalently conjugated with heparin as confirmed by Fourier transform infrared spectroscopy. The associated surface‐exposed heparin content was measured to be 1.92 µg cm^?2 and was shown to be active. Meanwhile, surface hydrophobicity decreased after heparin modification. Heparin immobilization greatly improved the hemocompatibility of polyurethane films both in vitro and in vivo. The in vitro cell responses revealed that the expression of proinflammatory markers CD106 and CD62E of human vein endothelial cells was significantly suppressed on the surfaces of the heparinized polyurethane films, while the affinity and proliferation of the cells were improved. The in vivo performance of this material before and after heparin modification was evaluated as a stent coating material in a porcine coronary artery injury model. Histological analysis indicated that heparinized polyurethane induced mild foreign body reactions and inflammation, which were much lower than those induced by unmodified polyurethane. Heparin immobilization also accelerated the endothelialization process on the surface of the polymer‐coated stents when implanted in porcine coronary arteries. More detailed long‐term studies are needed to confirm the biostability of the heparin and the endothelialized surfaces. Copyright © 2012 Society of Chemical Industry