Grafting 2-(Methacrylorloxy)ethyl-2-(trimethylammonium)ethyl Phosphate onto Segmented Polyurethane Surfaces To Improve Hemocompatibilities

We reported herein that 2-(methacrylorloxy)ethyl-2-(trimethylammonium)ethyl phosphate (MTP) was successfully grafted onto a segmented polyurethane (SPU) cast film surface. We found MTP orientated onto a film surface had excellent hemocompatibility, and the addition of the cross-linking agent N,N ‘ -methylenebisacrylamide (MBAA) further increased MTP orientation on the surface and lead to better hemocompatibility. 1,4-Butanediol (BD) as a chain extender was used to synthesize the SPU which was based on diphenylmethane diisocyanate (MDI), vinyl group-containing poly(butadiene) diol (PBD), and hydrogenated poly(butadiene) diol (HPBD). To obtain an alcohol-orientated surface of SPU, glycidyl methacrylate (GMA) was copolymerized with the SPU using α,α‘-azobis(isobutyronitrile) (AIBN) as a radical initiator, and diethanolamine (DEA) was used to open the epoxy group leading to hydroxylated SPU. Furthermore, MTP and the cross-linking agent MBAA were grafted onto the cast film surface of hydroxylated SPU by using diammonium cerium(IV) nitrate as a catalyst. The bulk characteristics of the resulting polymers were investigated by infrared spectroscopy (IR) measurements. We found that both polymerization time and MBAA concentration accelerated grafting. The phosphatidylcholine groups of MTP orientated on the surface and the addition of MBAA accelerated MTP grafting as revealed by attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) and electron spectroscopy for chemical analysis (ESCA) measurements. The hemocompatibility in vitro was evaluated with rabbit platelet-rich plasma (PRP) contact tests and viewed by scanning electron microscopy (SEM) using commercially available BioSpan and nongrafted SPU (NG-SPU) as references. We found that fewer platelets adhered to the MTP grafted surfaces and that they showed less shape variation than the references. Platelet adhesion to MTP-grafted polymers was inhibited 50−84% compared with NG-SPU. The relative clotting time of the cast films in contact with cow PRP was 2.74, 2.28, 1.79, and 1.00 for MTP grafted-SPU, NG-SPU, BioSpan, and glass, respectively.