Surface Modification Of Polyurethane Film With Covalent Immobilization Of Heparin

In this paper, surface modification of polyurethane (PU) was studied to improveits hydrophilicity and hemocompatibility via three methods. The grafting density andstructural of heparin decided whether polyurethane had good blood compatibility.Firstly, isocyanate functional groups were introduced onto PU surface by treatment ofhexamethylene diisocyanate. Heparin was covalently coupled with PU-NH2surface.The grafting density of heparin (HEP) was not high enough to achieve the goal ofanticoagulant.Secondly, isocyanate functional groups were introduced onto PU surface.Polyethylenimine(PEI) was linked onto the PU surface to obtain the PEI conjunctedPU surface (PU-PEI). Heparin was covalently coupled with PU-PEI surface. Thegrafting density of heparin was improved. However, the solubility of PU surfacemorphology was destroyed by the solvent.HEP and phosphorylcholine groups (PC) were grafted onto PU surface in order toimprove biocompatibility and anticoagulant activity. After the surface grafting sites ofPU were amplified with the primary amine groups of PEI, HEP and PC werecovalently linked onto the surface. The surface density of primary amine groups wasdetermined by a ninhydrin assay. The amount of heparin covalently immobilized onthe PU-PEI surface was determined by the toluidine blue method. The HEP and PCmodified surfaces were characterized by water uptake, water contact angle, attenuatedtotal reflection Fourier transform infrared spectroscopy (ATR-FTIR), X-rayphotoelectron spectroscopy (XPS), atomic force microscopy (AFM), scanningelectron microscope (SEM). The results showed that the PU-PEI surface wassuccessfully grafted with HEP and PC. The hydrophilicity and hemocompatibility ofthese grafted surfaces was significantly improved. These results suggested that thePU-HEP and PU-PC composite films are promising candidates for blood contactingtissue engineering.