Adherent platelet morphology on adsorbed fibrinogen: effects of protein incubation time and albumin addition.

The composition of the protein layer adsorbed to a polymer has been thought to be important for the adhesion of platelets. The state of activation of adherent platelets is an additional factor that may be a predictor of biocompatibility. Activation refers to the degree of change from discoid shape to any of several spread shapes. The conformation and orientation of adsorbed adhesive proteins, which interact with receptors on the membrane of platelets, such as fibrinogen, fibronectin, and von Willebrand factor, may also be important for platelet adhesion and activation. This work deals with the behavior of fibrinogen adsorbed to PMMA alone, where the experimental variable was incubation time with the substrate, and with adsorbed fibrinogen mixed with albumin, where the experimental variable was the molar percent of fibrinogen in the adsorption solution. Shorter protein incubation times and increased albumin levels in the initial fibrinogen adsorption solution enhanced the percentages of activated platelet morphologies and increased adsorbed fibrinogen redistribution by the platelet. Lower concentrations of albumin in the initial adsorption solution enhanced platelet adhesion numbers; fibrinogen incubation time had no effect. Together, these factors can contribute to the biocompatibility of a biomaterial through their effect on platelet adhesion and activation.