This paper reports in vivo
protein adsorption onto
polymers, including
Biomer, PEO grafted
Biomer (B-PEO-4K),
heparin immobilized
Biomer with PEO spacers (B-PEO-4K-HEP), and
HEMA-
Styrene block copolymer (H-S). Vascular grafts (6 mm ID, 7 cm in length) were fabricated with
Biomer, coated on their
luminal surfaces with test
polymers, and implanted into the abdominal aorta of dogs. After 3 weeks-1 month, the grafts were retrieved and processed for TEM and SEM. TEM measured the thickness of adsorbed
protein layers stained with a OsO4
solution, and the distribution pattern of adsorbed
proteins (
albumin,
IgG and
fibrinogen) using the immunoperoxidase technique. Retrieved grafts of
Biomer and B-PEO-4K showed mural thrombi along the graft length, while
thrombus formation on B-PEO-4K-HEP and H-S grafts was limited to the anastomotic sites. SEM pictures of B-PEO-4-HEP and H-S surfaces demonstrated clear morphology, with minimal platelet adhesion and activation, and microthrombi.
Biomer and B-PEO-4K demonstrated a thick proteinaceous layer (1000-2000 A), whereas B-PEO-4K-HEP and H-S showed what can be described as a monolayer
protein thickness (200-300 A). B-PEO-4K-HEP and H-S showed a monolayer-like adsorbed
protein pattern, with high concentrations of
albumin and
IgG, and less
fibrinogen, while
Biomer and B-PEO-4K showed multilayered patterns with relatively high concentrations of
fibrinogen, and less
albumin. These results suggest that the surface properties of
polymer may control
protein adsorption pattern, and the composition of adsorbed
protein is essential to in vivo long-term blood compatibility.