Uptake, localization and dissolution of barium sulfate nanoparticles in human lung cells explored by the combination of ICP-MS, TEM and NanoSIMS

Abstract

Background: Barium sulfate nanoparticles (BaSO4-NPs) are considered to be poorly soluble, chemically inert, and therefore relatively non-toxic. For humans, inhalative exposure represents the most significant route of uptake. Objective and methods: Cellular effects after exposure to BaSO4-NPs for 24 and 72 have been investigated in this study on primary human lung cells. To track the fate of BaSO4-NPs in human lung cells, we used inductively coupled plasma mass spectrometry (ICP-MS) to quantify cellular uptake of NPs, as well as transmission electron microscopy (TEM) and nanoscale secondary ion mass spectrometry (NanoSIMS) to investigate subcellular distribution of NPs through high-resolution elemental imaging. Results and conclusions: We show that BaSO4 nanoparticles have been taken up by normal human bronchial epithelial cells (NHBEC) in a dose-dependent manner. However, no clear time-dependent uptake could be observed. The barium sulfate nanoparticles were visible in vesicles within the cytosol by TEM, which was confirmed by high-resolution NanoSIMS images. Nevertheless, no uptake of the particles into the nucleus was observed in this study. However, it was shown that BaSO4-NPs were partly dissolved, and barium ions were distributed throughout the entire cell. Toxicity of the particles was indicated by a dose- and time-dependent loss of viability in human lung cells.