PLATELET BINDING AND PROTEIN ADSORPTION TO TITANIUM AND GOLD AFTER SHORT-TIME EXPOSURE TO HEPARINIZED PLASMA AND WHOLE-BLOOD

Protein adsorption from human plasma and platelet binding and activati on were studied at short blood-titanium/gold contact times. The protei n adsorption was studied by ellipsometry-antibody techniques in situ, and adhering platelets were visualized with fluorescein isothiocyanate -labelled anti-CD 61 antibodies. Adhering platelets were quantified by counting labelled cells in microscopic image fields. The spreading of platelets was studied by scanning electron microscopy. The results sh ow that after 1 min of plasma exposure, fibrinogen, IgG and albumin we re detectable with antibodies on both surfaces. The amount of deposite d fibrinogen and complement decreased with time on titanium, and the a mount of adsorbed anti-high molecular weight kininogen increased. No c omplement was detected on gold surfaces after plasma incubation, and t he antibody binding pattern also remained unchanged after prolonged pl asma exposure. The surface-bound platelets were found to spread on the gold but not on titanium surfaces. C1q has been shown to induce the e xpression of P-selectin, i.e. cause secretion reactions in platelets. In this study secreted platelet-microvesicles were found on gold, but not on the titanium surfaces that bound significant amounts of C1q. Th us, the results of the present study indicate that the mixture of fibr inogen, C1q and kininogens, whilst causing adhesion and aggregation, d oes not result in the activation and microvesicle secretion of platele ts. Platelet activation on biomaterial surfaces thus seems to be gover ned by the mixture of proteins present on that surface, and no one par ticular protein need cause a known reaction in platelets as obtained w hen platelets are exposed only to that particular protein. (C) 1996 El sevier Science Limited.