Repetitive exposure to zinc oxide nanoparticles induces dna damage in human nasal mucosa mini organ cultures

Abstract

Data on the toxicological properties of zinc oxide nanoparticles (ZnO-NPs) is incomplete. ZnO-NPs may enter humans via inhalation or ingestion. The aim of the current study was to evaluate ZnO-NP-induced genotoxicity in three-dimensional (3D) mini organ cultures (MOCs) of human nasal mucosa following repeated exposure to ZnO-NP and regeneration. Nasal MOCs of 10 patients and ZnO-NPs were cultivated for one week and then characterized by electron microscopy. Nasal MOCs were partially covered by ciliated epithelium after one week of cultivation. ZnO-NPs were distributed to the cytoplasm and the nucleus. MOCs were exposed once, twice, or three times to 0.1 or 5 μg/ml of ZnO-NPs for 1 hr per exposure and were then evaluated for cytotoxicity and genotoxicity. MOCs were cultivated for 24 hr after the triple ZnO-NP exposure to allow for regeneration. ZnO-NP exposure did not result in significant cytotoxicity or apoptosis, as determined by trypan blue exclusion and caspase-3 activity, respectively. A significant increase in DNA damage was detected following repetitive exposure compared to single exposure to ZnO-NPs at 5 μg/ml, but not 0.1 μg/ml ZnO-NPs. At both concentrations of ZnO-NP, DNA fragmentation increased after 24 hr of regeneration. In contrast, DNA damage which was induced by the positive control, methyl methanesulfonate, was significantly reduced after 24-hr regeneration. Thus, our results suggest that repetitive exposure to low concentrations of ZnO-NPs results in persistent or ongoing DNA damage.

Assessing nanoparticle toxicity in cell-based assays: influence of cell culture parameters and optimized models for bridging the in vitro–in vivo gap

“…exposed 3D mini-organ cultures of human nasal mucosa on three subsequent days to ZnONP for 1h and did not find any acute toxicity or apoptosis but did observe DNA damage 218 . Thus, 3D models can be applied to assess cumulative effects while this is hampered in 2D cultures as cells do not survive longer cultivation periods, dedifferentiate or rapidly divide causing dilution of the NP and an associated dilution of any possible effects.…”

A review of mammalian toxicity of ZnO nanoparticles

“…64 Repetitive exposure to 76 × 53 nm ZnO NPs (5 µg/mL) of human nasal mucosa mini-organ cultures induced DNA damage, established using the comet assay. 65 This damage was further increased after a 24-hour regeneration period. The NPs were distributed in the cytoplasm and the nucleus.…”

ZnO nanoparticle tracking from uptake to genotoxic damage in human colon carcinoma cells

“…Recent studies have shown that ZnO nanoparticles induced DNA damage in different cell lines, e.g. epidermal, nasal mucosa, lymphoblastoid, liver, kidney and neuronal cells (Bhattacharya et al, 2014;Guan et al, 2012;Hackenberg et al, 2011;Sharma et al, 2011Sharma et al, , 2012Valdiglesias et al, 2013). Yet, a complete understanding of the cell toxicity mechanism is still to be achieved.…”