Non-ionic block copolymer surfactants such as Pluronics (PEO-PPO-PEO) have been shown to inhibit platelet aggregation and thrombosis. The mechanisms regulating this inhibition are yet unknown. In this study, we examined how the physico-chemicalproperties of pluronics may contribute to their inhibitory role. Platelet rich plasma from human volunteers was stimulated with adenosine 5'-diphosphate (ADP) and sheared at a constant rate of 200/s using cone-plate viscometry. Cell aggregation kineticswas monitored using flow cytometry. The inhibition efficacy of four Pluronics (F-68, P-105, L-64 and F-108) which have varying polymer segment lengths and critical micelle concentrations (CMC) was examined. 2mM F-68, which has a high CMC of 8.33mM wasfound to inhibit platelet aggregation by ～50%, while P-105 with a low CMC of 0.11mM did not have a statistically significant inhibitory role. Overall, molecules with longer PEO side chains like F-68 and F-108 were better inhibitors than L-64 and P-105respectively. Together, these results suggest a model where the aggregation inhibitory efficacy of pluronics is dependent on their relative binding rates either to the platelet surface, or their tendency to self-assemble into micelles. Current studiesthat test this model by examining the nature of platelet-polymer interactions using fluorescein labeled Pluronics are also be presented.
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