Effect of adsorbed von Willebrand factor and fibrinogen on platelet interactions with synthetic materials under flow conditions.

The effect of adsorbed fibrinogen (Fg) and von Willebrand factor (vWf) on platelet adhesion at low or high shear rate to several materials was studied. The materials studied were polyethylene terephthalate (PET), polystyrene (PS), glass, and tetraglyme-coated PET. The materials were preadsorbed with normal plasma, serum, and Fg-deficient plasma replenished with various amounts of Fg, and vWf-deficient plasma with or without added vWf. Platelet adhesion to PET preadsorbed with Fg-deficient plasma or serum was low at either low or high shear rate, but increased as Fg was added to the preadsorption media. However, the effect of added Fg on adhesion at the higher shear rate was much greater on surfaces preadsorbed with plasma than for serum, probably due to the much lower vWf concentration in serum in comparison to plasma. Platelet adhesion to either polystyrene or glass preadsorbed with normal plasma was much higher at high shear than low shear, but when vWf-deficient plasma was used to preadsorb these surfaces, adhesion was much less at the higher shear rate than at low shear rate. Platelet adhesion to polystyrene preadsorbed with vWf-deficient plasma to which vWf was added was higher at high shear rate than low shear rate. These results show that under high shear rate, both Fg and vWf are required for platelet adhesion on synthetic biomaterials. The results suggest that developing surfaces that adsorb low amounts of vWf is a good approach to improving the blood compatibility of biomaterials.