Blood compatibility of PEO grafted polyurethane and HEMA/styrene block copolymer surfaces

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Abstract
HEMA/styrene (HEMA/STY) block copolymers and poly(ethylene oxide) 4,000 M.W. (PEO4K) grafted Biomer (B‐PEO4K) surfaces have been synthesized, characterized, and evaluated as blood‐contacting materials. These surfaces have demonstrated improved blood compatibility, compared to Biomer, in in vitro and ex vivo experiments. Biomer vascular grafts (6 mm I.D. 7 cm in length) were fabricated by a dip coating process. The luminal surface was modified either with PEO grafting, HEMA/STY coating, or Biomer coating (control). These surface‐modified grafts were implanted in the abdominal aortas of dogs and evaluated for graft patency and protein adsorption. Surface protein layer thickness was measured by transmission electron microscopy (TEM). B‐PEO4K and Biomer showed thick multilayers of adsorbed proteins (1000–2000 Å) after 3 weeks to 1 month implantation. In contrast, HEMA/STY only showed a monolayer protein thickness (in vivo blood compatibility. This manuscript will evaluate the long‐term in vivo performance of these polymers, analyze the extent of protein adsorption onto the surfaces, and correlate protein layer thickness to the thrombogenicity of the polymer surfaces.