Leukocyte activation and leukocyte procoagulant activities after blood contact with polystyrene and polyethylene glycol-immobilized polystyrene beads

Beads (45 mum) of polystyrene (PS) and polyethylene glycol modified PS (Ten taGel) with an amino or hydroxyl terminal group were incubated with blood t o assess the effect of surface area and material chemistry on leukocyte act ivation. After a 2-hour incubation, blood contact with beads activated leuk ocytes in the bulk (tissue factor expression, CD11b up-regulation, and asso ciation with platelets) independently of material surface chemistry. On the other hand, activation of adherent leukocytes was material dependent. Afte r blood contact with PS, polyethylene glycol-immobilized PS (PS-PEG) and PS -PEG-NH2 beads, CD11b up-regulation In the bulk, platelet-leukocyte aggrega tes, and leukocyte adhesion were all dependent on surface area, whereas tis sue factor (TF) expression was not. Material-induced leukocyte activation i n the bulk was also independent of the beads' capacity to activate platelet s. However, monocyte adhesion and TF expression on beads appeared to be rel ated to the presence of platelets on the surface. Material-induced TF expre ssion was able to initiate the extrinsic pathway of coagulation, resulting in significant fibrin formation. Although not all of our markers of leukocy te activation varied with material area or chemistry, it was clear that the se materials activated leukocytes in a way that resulted in increased proco agulant activity. During blood-material interactions. material-induced leuk ocyte activation may then contribute to thrombogenesis.