Surface Modification of Segmented Polyurethanes by Grafting Methacrylates and Phosphatidylcholine Polar Headgroups To Improve Hemocompatibility

A new type of phosphatidylcholine-containing segmented polyurethane (SPU) surface was produced by grafting various methacrylates and phosphatidylcholine polar headgroups to a vinyl-group-containing segmented polyurethane (V-SPU) using α,α‘-azobisisobutyronitrile (AIBN) as a radical initiator. 1,4-Butanediol (BD) as chain extender was used to synthesize the V-SPU, which is based on diphenylmethane diisocyanate (MDI) and vinyl-group-containing poly(butadiene) diol (PBD). Several methacrylates, such as methyl methacrylate (MMA), butyl methacrylate (BMA), stearyl methacrylate (SMA), and a phosphatidylcholine polar-headgroup-containing vinyl monomer, 2-(methacrylorloxy)ethyl-2-(trimethylammonium)ethyl phosphate (MTP), were grafted to the V-SPU. The bulk characteristics of the grafted V-SPUs were investigated by infrared (IR) spectroscopy, viscosity, and gel permeation chromatography (GPC) measurements. Mechanical properties of the typical SPU containing MMA were measured by dynamic viscoelasticity and tensile measurements. The phosphatidylcholine polar headgroups were oriented on the surface of these materials, as revealed by attenuated total reflectance-Fourier transform infrared spectroscopy (ATR−FTIR), electron spectroscopy for chemical analysis (ESCA), and contact angle measurements. The phosphatidylcholine polar-headgroup-grafted SPU surfaces showed slightly decreased water contact angles, also indicating that hydrophilic phosphatidylcholine polar headgroups are present at the surface. The hemocompatibility in vitro was evaluated with platelet-rich plasma (PRP) contact tests and viewed by scanning electron microscopy (SEM) using the ingrafted V-SPU as a reference. It was found that fewer platelets adhered to the modified surfaces and showed less shape variation than to the unmodified V-SPU. Platelet adhesion to phosphatidylcholine polar-headgroup-grafted polymers was inhibited 88−95% compared with unmodified V-SPU.