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.

Optical transmission of blood: effect of erythrocyte aggregation.

The influence of red blood cell (RBC) aggregation on transparency of blood in the red-near infrared spectral range is investigated. We argue that for relatively thin blood layers the light diffraction on aggregates becomes the dominant phenomenon. The nature of pulsatile changes of blood transparency is explained by pulsations of RBC aggregate size. For another case of over-systolic vessel occlusion the following time evolution of blood transparency strongly depends on light wavelength. This dependence may serve as a basis for an alternative approach to noninvasive blood tests: occlusion spectroscopy. Theoretical results well correspond to both in vivo and in vitro measurements reproducing pulsatile blood flow and long occlusion as well.