Preparation And Characterization Of Medical Anticoagulant Polyurethane Material

Polyurethane (PU) has played a major role in medical devices ranging from catheters to total artificial heart. However, the thrombogenicity problem of polyurethane needs to be tackled. Two approaches have been employed recently to deal with this problem. The first one is the physical modification approach, the other one is the chemical modification approach. In general, the physical blending is useful for short-term or medium-term antithrombogenicity, while other modified approaches are focusing on the modification on the PU surface. Nevertheless, the influence of the polymer surface properties in the complex system of blood remains ambiguous. In this study, we immobilized heparin not only on the surface but also in the bulk of PU hoping the heparin-immobilized PU would be hemocompatible in long-term, and it can be applied to form devices in any shape or be used as the coating of other biomedical devices.Heparin (Hep)-immobilized poly(ether urethanes)(PU), hoping to be used as medical hemocompatible PU, was prepared by a unique procedure. First, the poly(ether urethanes) containing diester groups in the side chains were synthesized. The proportions of the diester groups carrier, diethyl bis(hydroxymethyl)-malonates (DBM), were set at12.5at%(PU-3DBM) and25at%(PU-6DBM) for comparison. Then, PU-3DBM and PU-6DBM were dispersed in aqueous solutions separately and immobilized with0.49wt%and0.93wt%of heparin respectively after the hydrolysis of diester groups and carboxylation. The hydrolysis time was fixed at30minutes to hydrolyze the diester groups in the side chain without significant decrease of the mechanical properties. The amounts of carboxylic groups in the hydrolyzed PU were determined by Rhodamine6G method and the results successfully explain the proportional behavior of DBM.Moreover, the Fourier transform infrared spectroscopy (FTIR) and proton nuclear magnetic resonance spectroscopy (’H-NMR) were used to confirm the immobilization of heparin. Elemental analyzer (EA) results show that the sulfur content in PU-6DBM-Hep was nearly twice as in PU-3DBM-Hep. The electrical spectroscopy chemical analysis (ESCA) demonstrates that the sulfur content is higher in the surface than in the bulk of PU-3DBM-Hep. The PU surface became more hydrophilic after heparin immobilization illustrated by water contact angle (WCA) results. The heparin-immobilized PU could release part of heparin in the first90hours when soaked in saline and they were examined to be hemocompatible by hemolysis ratio test and platelets adhesion experiment in vitro. However, in the evaluation of the modified PU as stent-coating in the animal vitro experiment, the injury and inflammation of the arteries implanted with PU-coated stents are more serious than the arteries implanted with bare stents. In a word, the antithrombogenic PU prepared in this study is hoping to be used as hemocompatible materials in vitro.