Lyophilized Synthetic Platelets: In Vitro Characterization and in Vivo Evaluation in Mouse Thrombocytopenia Model

Platelet transfusions to treat bleeding complications use donor-derived platelets stored at room-temperature, that have a shelf-life of only 5-7 days due to bacterial contamination risks. Cold-stored and freeze-dried platelets are being investigated for extending shelf-life, but these still have the inherent challenge of donor-dependency. To address this, we developed a liposome-based synthetic platelet (SP) nanoconstruct that mimics the primary hemostatic mechanisms of platelets, and have previously reported its efficacy. However, a logistical limitation of SP is its susceptibility to environment-induced physico-chemical instabilities that reduces shelf-life when stored as aqueous suspension, impacting its availability and bioactivity. Lyophilization of liposomal nanotherapeutics utilizing anhydrobiosis-inspired lyoprotectants can enhance shelf-life, but this has not been explored for synthetic platelets. With these considerations, we report advancing SP into a lyophilized product (Lyo-SP) that can be rapidly aqueous-reconstituted for on-demand use. Lyo-SP retained morphology, size, and charge in long-term storage at various temperatures, and conserved platelet-mimetic functions in multiparametric assays with human plasma and blood. Lyo-SP demonstrated biosafety in its effect analysis on endothelial cells, neutrophils, RBCs and complement C3. Lyo-SP significantly reduced bleeding in a tail-clip model in thrombocytopenic mice. These studies establish the potential of Lyo-SP as a shelf-stable platelet surrogate for treating bleeding complications.