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

Purpose. To investigate the influence of animal species and nanoparticle su rface characteristics on the intrasplenic distribution of polystyrene nanop articles. Methods, Two types of fluorescent polystyrene nanoparticles (Estapor(R) and Fluoresbrite(R)), plain or coated, were used in mice and rats. First, a fl uorimetric method was developed for nanoparticle tissue quantification. The n, intrasplenic distribution of plain or coated nanoparticles was studied u sing histological examination and image analysis. Finally, the role of dire ct interactions between nanoparticles and spleen capturing cells was assess ed 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 b y 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 rat s, the predominant capture occured in the red pulp. In mice, coated nanopar ticles were localized both in the marginal zone and in the red pulp, wherea s the coating did not seem to change the intrasplenic distribution of the n anoparticles in rats. Conclusions. These complementary approaches showed different uptake pathway s of nanoparticles, according to their surface characteristics and the rode nt species used.