Blood compatibility of PEO grafted polyurethane and HEMA/styrene block copolymer surfaces.
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 A) after 3 weeks to 1 month implantation. In contrast, HEMA/STY only showed a monolayer protein thickness (less than 200 A), even after 3 months. Visualization of adsorbed plasma proteins (albumin, IgG, and fibrinogen) was performed with scanning electron microscopy (SEM)/TEM using an immunogold double antibody technique. The pattern of protein distribution showed high concentrations of fibrinogen and IgG, and less albumin adsorbed onto Biomer and B-PEO4K. In contrast, HEMA/STY showed a patchy protein distribution pattern with high concentrations of albumin and IgG, and relatively less fibrinogen. Adsorbed monolayer patterns showed improved compatibility over multilayered proteins. The Biomer and B-PEO4K grafts occluded within 1 month, while HEMA/STY grafts were patent for over 3 months. The thin and stable adsorbed protein layer on HEMA/STY surfaces may be associated with the microdomain structures of the surface, and will play an important role in long-term 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.
Nojiri
C
C
Department of Pharmaceutics/Center for Controlled Chemical Delivery, University of Utah, Salt Lake City 84108.
Okano
T
T
Jacobs
H A
HA
Park
K D
KD
Mohammad
S F
SF
Olsen
D B
DB
Kim
S W
SW
D000327:Adsorption; D000818:Animals; D001672:Biocompatible Materials; D001777:Blood Coagulation; D001798:Blood Proteins / Q000378:metabolism; D001807:Blood Vessel Prosthesis; D004285:Dogs; D008422:Materials Testing; D008689:Methacrylates; D008854:Microscopy, Electron; D011140:Polyurethanes; D013499:Surface Properties
D001672:Biocompatible Materials; D001798:Blood Proteins; D008689:Methacrylates; D011140:Polyurethanes; C005044:hydroxyethyl methacrylate