Uptake of some metallic nanoparticles by, and their impact on pulmonary macrophages in vivo as viewed by optical, atomic force, and transmission electron microscopy

Abstract

Optical microscopy (OM), semi-contact atomic force microscopy (sc-AFM), and transmission electron microscopy (TEM) were applied to examine cells in the broncho-alveolar lavage fluid (BALF) obtained from rats 24 hours after instillation of different metallic particles suspended in deionised water or of water without any particles. In a comparative experiment with iron oxide Fe3O4 (magnetite) particles having a mean diameter of 10 nm, 50 nm or 1 μm, it was demonstrated that, given equal mass doses, nanoparticles (NPs) induce much more intensive recruitment of phagocytes with a much more significant shift toward neutrophil leukocytes (NL) count in the BALF cell population than micrometric particles do, this shift being an indirect but informative index of particle cytotoxicity for alveolar macrophages (AM). Judging by NL/AM ratio, this cytotoxicity diminishes in the sequence: 10 nm > 50 nm> 1 μm, while judging by OM counts of visible aggregated particles within AMs and NLs and by sc-AFM count of micro-invaginations on the surfaces of these cells, their avidity for particles decreases in the same succession. The same dependence of cell recruitment and of phagocytic activity on NP cytotoxicity was found when the NP diameters were quite similar (ca. 3.5-4.0 nm) but the cytotoxicity of one metal (in our experiment, nanosilver) was higher than that of another (nanogold). TEM pictures of AMs from rats administered the 10 nm magnetite testify to the ability of AMs to actively engulf single NPs and their small aggregates which then form larger conglomerates within fused phagosomes. Some of these large phagosomes lost their membrane, and so freed NPs came into close contact with the nuclear membrane and with mitochondrial membranes and cristae causing their marked damage.& copy 2012 Katsnelson BA, et al.