Toxicity assessment of industrial engineered and airborne process-generated nanoparticles in a 3D human airway epithelial in vitro model

Abstract

The advanced ceramic technology has been pointed out as a potentially relevant case of occupational exposure to nanoparticles (NP). Not only when nanoscale powders are being used for production, but also in the high-temperature processing of ceramic materials there is also a high potential for NP release into the workplace environment. In vitro toxicity of engineered NP (ENP) [antimony tin oxide (Sb₂O₃•SnO₂; ATO); zirconium oxide (ZrO₂)], as well as process-generated NP (PGNP), and fine particles (PGFP), was assessed in MucilAir™ cultures at air–liquid interface (ALI). Cultures were exposed during three consecutive days to varying doses of the aerosolized NP. General cytotoxicity [lactate dehydrogenase (LDH) release, WST-1 metabolization], (oxidative) DNA damage, and the levels of pro-inflammatory mediators (IL-8 and MCP-1) were assessed. Data revealed that ENP (5.56 µg ATO/cm² and 10.98 µg ZrO₂/cm²) only caused mild cytotoxicity at early timepoints (24 h), whereas cells seemed to recover quickly since no significant changes in cytotoxicity were observed at late timepoints (72 h). No meaningful effects of the ENP were observed regarding DNA damage and cytokine levels. PGFP affected cell viability at dose levels as low as ∼9 µg/cm², which was not seen for PGNP. However, exposure to PGNP (∼4.5 µg/cm²) caused an increase in oxidative DNA damage. These results indicated that PGFP and PGNP exhibit higher toxicity potential than ENP in mass per area unit. However, the presence of a mucociliary apparatus, as it occurs in vivo as a defense mechanism, seems to considerably attenuate the observed toxic effects. Our findings highlight the potential hazard associated with exposure to incidental NP in industrial settings.

Keywords:

• Ceramic technology
• engineered nanoparticles
• process-generated nanoparticles
• MucilAir™
• thermal spraying

Acknowledgments

The authors would like to take this opportunity to thank all institutions involved for their support to this project. The authors kindly acknowledge TM COMAS (http://www.tmcomas.com) and Keeling & Walker (https://www.keelingwalker.co.uk) for their committed cooperation. Finally, the authors would also like to acknowledge Dr. Jüergen Schnekenburger (University of Müenster, Germany) for gamma-ray sterilization of the NP stock suspensions.

Disclosure statement

The authors declare that the original work described is approved by all co-authors, has not been previously published and is not under consideration for publication elsewhere. In addition, the authors also declare that they have no conflicts of interest concerning this article.

Additional information

Funding

The current work was carried out in the framework of the CERASAFE project (www.cerasafe.eu), with the support of ERA-NET SIINN (project id:16) and the Portuguese Foundation for Science and Technology (FCT; SIINN/0004/2014). This work was also supported by the NanoBioBarriers project (PTDC/MED‐TOX/31162/2017), co-financed by the Operational Program for Competitiveness and Internationalization (POCI) through European Regional Development Funds (FEDER/FNR) and FCT; Spanish Ministry of Science and Innovation (projects PCIN-2015-173-C02-01 and CEX2018-000794-S-Severo Ochoa) and by the Romanian National Authority for Scientific Research and Innovation (CCCDI-UEFISCDI, project number 29/2016 within PNCDI III). Thanks are also due to FCT/MCTES for the financial support to EPIUnit (UIDB/04750/2020). M.J. Bessa (SFRH/BD/120646/2016) and F. Brandão (SFRH/BD/101060/2014) are recipients of FCT PhD scholarships under the framework of Human Capital Operating Program (POCH) and European Union funding.