Human plasma fibrinogen adsorption and platelet adhesion to polystyrene

The purpose of this study was to further investigate the role of fibrinogen adsorbed from plasma in mediating platelet adhesion to polymeric biomateri als. Polystyrene was used as a model hydrophobic polymer; i.e., we expected that the role of fibrinogen in platelet adhesion to polystyrene would be r epresentative of other hydrophobic polymers. Platelet adhesion was compared to both the amount and conformation of adsorbed fibrinogen. The strategy w as to compare platelet adhesion to surfaces preadsorbed with normal, afibri nogenemic, and fibrinogen-replenished afibrinogenemic plasmas. Platelet adh esion was determined by the lactate dehydrogenase (LDH) method, which was f ound to be closely correlated with adhesion of In-111-labeled platelets. Fi brinogen adsorption from afibrinogenemic plasma to polystyrene (Immulon I(R )) was low and <10 ng/cm(2). Platelet adhesion was absent on surfaces pread sorbed with afibrinogenemic plasma when the residual fibrinogen was low eno ugh (<60 mu g/mL). Platelet adhesion was restored on polystyrene preadsorbe d with fibrinogen-replenished afibrinogenemic plasma. Addition of even smal l, subnormal concentrations of fibrinogen to afibrinogenemic plasma greatly increased platelet adhesion. In addition, surface-bound fibrinogen's abili ty to mediate platelet adhesion was different, depending on the plasma conc entration from which fibrinogen was adsorbed. These differences correlated with changes in the binding of a monoclonal antibody that binds to the A al pha chain RGDS (572-575), suggesting alteration in the conformation or orie ntation of the adsorbed fibrinogen. Platelet adhesion to polystyrene preads orbed with blood plasma thus appears to be a strongly bivariate function of adsorbed fibrinogen, responsive to both low amounts and altered states of the adsorbed molecule. (C) 1999 John Wiley & Sons, Inc.