Spleen capture of nanoparticles: Influence of animal species and surface characteristics

Purpose. To investigate the influence of animal species and nanoparticle surface characteristics on the intrasplenic distribution of polystyrene nanoparticles. Methods, Two types of fluorescent polystyrene nanoparticles (Estapor(R) and Fluoresbrite(R)), plain or coated, were used in mice and rats. First, a fluorimetric method was developed for nanoparticle tissue quantification. Then, intrasplenic distribution of plain or coated nanoparticles was studied using histological examination and image analysis. Finally, the role of direct interactions between nanoparticles and spleen capturing cells was assessed by in vitro binding assays, using incubation of thick spleen slices with polystyrene nanoparticles. Results, The two types of polystyrene nanoparticles showed different levels of trapping: Fluoresbrite(R) nanoparticles were more efficiently trapped by the spleen than Estapor(R) nanoparticles, both in mice and rats. In mice, most of the injected nanoparticles were localized in the marginal zone of the spleen, involving a special population of capturing cells, while in rats, the predominant capture occured in the red pulp. In mice, coated nanoparticles were localized both in the marginal zone and in the red pulp, whereas the coating did not seem to change the intrasplenic distribution of the nanoparticles in rats. Conclusions. These complementary approaches showed different uptake pathways of nanoparticles, according to their surface characteristics and the rodent species used.