Platinum group metals represent a class of anthropogenic pollutants generated as a byproduct of their use in
automobile catalytic converters. We prepared palladium nanoparticles (Pd-NPs, about 6 nm) similar to those emitted in
auto exhaust, and examined their behavior in different liquids using dynamic light scattering and transmission electron
microscopy (TEM). We found that serum-containing DMEM medium or conditioned DMEM provides good dispersion
and stability for Pd-NPs at pH 7.2–7.4. We then incubated primary mouse macrophages and epithelial MDCK cells with
Pd-NPs for 10 and 30 min, 3, 5 and 24 h, and sampled for TEM. Pd-NPs penetrated into MDCK cells by crossing the
plasma membrane and were located in the cytoplasm, organelles and preferentially in the nucleus. The macrophages actively
phagocytosed clusters of Pd-NPs, which were observed inside the membrane-bound structures but were not found
in the cytoplasm and nucleus. Macrophage phagocytosis could be efficient in the lungs of living organisms, where they
move across the surface of the respiratory epithelium and collect inhaled pollutants. Our study showed harmful effect of
Pd-NPs on epithelial cells and the possibility of this effect being ameliorated by macrophages, which are resistant to penetration
by Pd-NPs and sequestered them in phagolysosomes.
Keywords: Cellular uptake, cytotoxicity, macrophage, MDCK cells, palladium nanoparticles.
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