Modulating Nanoparticle Size to Understand Factors Affecting Hemostatic Efficacy and Maximize Survival

Polymeric particle-based hemostats have been demonstrated to be an attractive technology to halt bleeding through extensive testing in animal models, ranging from arterial injury to blast trauma. While the results of these in vivo experiments have been well documented and utilized to develop subsequent generations of hemostats, the effect of particle-target interactions and their predictive capabilities for in vivo performance has yet to be fully explored. In this work, the size of GRGDS-conjugated PEG-b-PLGA nanoparticles was tuned and its effect on platelet binding, particle adherence to wound-mimetic surfaces, aggregation capability, biodistribution, and circulation lifetime were systematically assessed using various in vitro and in vivo experiments. Smaller and intermediate-sized nanoparticles were all found to specifically bind a larger number of activated platelets when compared to larger (>300 nm) particles, while incubation of these larger particles on collagen and activated platelet-coated surfaces led to a higher total mass of polymer bound. Intermediate particle diameters led to the greatest number of platelets aggregated on a surface relative to agonist-only positive controls. Finally, larger particles experienced faster clearance and higher pulmonary accumulation per organ mass in an uninjured murine model, whereas smaller particles exhibited longer circulation and retention times and increased accumulation in the liver. These results indicate that tuning particle size provides a key handle for engineering the performance of particle-based hemostat systems, with specific size offering optimal performance depending on the desired outcome.