Polystyrene Nanoparticles Activate Erythrocyte Aggregation and Adhesion to Endothelial Cells

Nanoparticles (NPs) are drawing an increasing clinical interest because of their potential use as drug carriers. Recently, a new strategy for elevation of NPs in vivo circulation time has been proposed, specifically, utilizing red blood cells (RBCs) as a carrier for NPs, that are loaded with a drug, by interaction (in vitro) of human RBCs with NPs (RBCNP). This class of delivery set-up, combines advantages of natural RBCs and synthetic biomaterials. Previous studies demonstrated that NPs initiated hemolysis of RBC and activated cells aggregation. In the present study, we examined the effect of RBCNP on the aggregation of RBC and their adhesion to endothelial cells (EC). Red cells were treated with polystyrene NPs (PS-NP), and following their washing, were added to suspension of untreated cells at various concentrations. We observed that the PS-NP and RBCNP initiated the formation of red cells aggregates and markedly elevated RBC adhesion to EC. These effects were augmented with (a) increasing concentration of NPs or RBCNP, and (b) with decreasing NP size. This implies that RBCNP are cells with a stronger intercellular interaction, and may thereby induce the formation of large and strong aggregates with untreated RBC, as well as strong RBC/EC interaction.