Liposomes bearing fibrinogen could potentially interfere with platelet interaction and procoagulant activity

The contribution of fibrinogen (FBN) to hemostasis acting on platelet aggregation and clot formation is well established. It has been suggested that FBN-coated liposomes could be useful in restoring hemostasis. In the present study, we evaluated the modifications induced by multilamellar raw liposomes (MLV) or fibrinogen-coated liposomes (MLV-FBN) on hemostatic parameters.

Different experimental settings using whole blood or thrombocytopenic blood were used. Thromboelastometry, aggregation studies, platelet function analyzer (PFA-100(®)) tests and studies under flow conditions were applied to detect the effect of MLV-FBN on hemostatic parameters.

The presence of MLV-FBN in whole blood modified its viscoelastic properties, prolonging clot formation time (CFT) (226.5 ± 26.1 mm versus 124.1 ± 9.4 mm; P < 0.01) but reducing clot firmness (45.4 ± 1.8 mm versus 35.5 ± 2.3 mm; P < 0.05). Under thrombocytopenic conditions, FIBTEM analysis revealed that MLV-FBN shortened clotting time (CT) compared to MLV (153.3 ± 2.8 s versus 128.0 ± 4.6 s; P < 0.05). Addition of either liposome decreased fibrin formation on the subendothelium (MLV 8.1% ± 4.7% and MLV-FBN 0.8% ± 0.5% versus control 36.4% ± 6.7%; P < 0.01), whereas only MLV-FBN significantly reduced fibrin deposition in thrombocytopenic blood (14.4% ± 6.3% versus control 34.5% ± 5.2%; P < 0.05). MLV-FBN inhibited aggregation induced by arachidonic acid (52.1% ± 8.1% versus 88.0% ± 2.1% in control; P < 0.01) and ristocetin (40.3% ± 8.8% versus 94.3% ± 1.1%; P < 0.005), but it did not modify closure times in PFA-100(®) studies. In perfusion experiments using whole blood, MLV and MLV-FBN decreased the covered surface (13.25% ± 2.4% and 9.85% ± 2.41%, respectively, versus control 22.0% ± 2.0%; P < 0.01) and the percentage of large aggregates (8.4% ± 2.3% and 3.3% ± 1.01%, respectively, versus control 14.6% ± 1.8%; P < 0.01).

Our results reveal that, in addition to the main contribution of fibrinogen to hemostasis, MLV-FBN inhibits platelet-mediated hemostasis and coagulation mechanisms.