In vitro characterization of SynthoPlate™ (synthetic platelet) technology and its in vivo evaluation in severely thrombocytopenic mice

Abstract

Background Platelet transfusion applications face severe challenges, owing to the limited availability and portability, high risk of contamination and short shelf-life of platelets. Therefore, there is significant interest in synthetic platelet substitutes that can provide hemostasis while avoiding these issues. Platelets promote hemostasis by injury site-selective adhesion and aggregation, and propagation of coagulation reactions on their membranes. On the basis of these mechanisms, we have developed a synthetic platelet technology (SynthoPlate™) that integrates platelet-mimetic site-selective 'adhesion' and 'aggregation' functionalities via heteromultivalent surface decoration of lipid vesicles with von Willebrand factor-binding, collagen-binding and active platelet integrin glycoprotein (GP)IIb-IIIa-binding peptides. Objective To evaluate SynthoPlatefor its effects on platelets and plasma invitro, and for systemic safety and hemostatic efficacy in severely thrombocytopenic mice invivo. Methods Invitro, SynthoPlatewas evaluated with aggregometry, fluorescence microscopy, microfluidics, and thrombin and fibrin generation assays. Invivo, SynthoPlatewas evaluated for systemic safety with prothrombin and fibrin assays on plasma, and for hemostatic effects on tail-transection bleeding time in severely thrombocytopenic (TCP) mice. Results SynthoPlatedid not aggregate resting platelets or spontaneously promote coagulation in plasma, but could amplify the recruitment and aggregation of active platelets at the bleeding site, and thereby site-selectively enhance fibrin generation. SynthoPlatedose-dependently reduced bleeding time in TCP mice, to levels comparable to those in normal mice. SynthoPlatehas a reasonable circulation residence time, and is cleared mostly by the liver and spleen. Conclusion The results demonstrate the promise of SynthoPlateas a synthetic platelet substitute in transfusion treatment of platelet-related bleeding complications.