Cells involved in the capture of nanoparticles in hematopoietic organs.

The affinity of nanoparticles for hematopoietic organs could be valuable for the targeting of certain stimulating factors to those tissues, but this affinity should also be taken into account in the toxicological evaluation of those carriers, especially when they are loaded with antimitotic compounds such as doxorubicin. However, the cells responsible for the capture of the nanoparticles and their localization in these organs is an important point to know before trying to modulate the nanoparticle's tissue distribution. Thus, we have studied, in this paper, the capture, the localization, and the retention in the bone marrow and in the spleen of biodegradable poly(isohexyl cyanoacrylate) nanoparticles as well as of nonbiodegradable polystyrene nanoparticles. The histological localization of these nanoparticles has been completed by cytological localization with a method used in cytochemistry for the evaluation of intracellular accumulation of various substances, such as iron deposits in bone marrow sideroblasts. These data indicate that, in the bone marrow, after a quick passage through the endothelium, nanoparticles were dispersed throughout in the tissue and captured by all types of phagocytizing cells. In the spleen, nanoparticles were mainly localized in large angular capturing cells in the marginal zone of the lymphoid follicles.