Thrombus formation on artificial surfaces can be viewed as the sequential and concomitant involvement of protein adsorption, platelet reactions, activation of the coagulation system, participation of complement, fibrinolytic and kallikrein-kinin systems, and the interaction of cellular elements. This study examines the activation of leucocytes on a series of well-characterized polyurethanes with different ionic groups [sulphonate groups (negatively charged); quaterinary amine groups (positively charged)], in terms of adhesion, degranulation and cell surface integrin receptor expression. Leucocyte adhesion was monitored with radiolabelled neutrophils and scanning electron microscopy (SEM), degranulation by measurement of human neutrophil elastase: using an indirect enzyme-linked immunosorbent assay and cell surface expression of the integrin receptor Mac-1, using fluorescent-activated cell sorting (FAGS). Our results indicate a trend towards enhanced adhesion and degranulation with respect to the negatively charged polyurethane. Similar results were observed with respect to the integrin Mac-1 from recovered adherent cells. The findings of enhanced adhesion and spreading, Mac-1 up-regulation and granulocyte elastase release from the negatively charged sulphonated polyurethane indicate the potential of leucocytes to contribute towards thrombus formation on such surfaces.
