Toxicological effects of zinc oxide nanoparticle exposure: an in vitro comparison between dry aerosol air-liquid interface and submerged exposure systems

Abstract

Engineered nanomaterials (ENMs) are increasingly produced and used today, but health risks due to their occupational airborne exposure are incompletely understood. Traditionally, nanoparticle (NP) toxicity is tested by introducing NPs to cells through suspension in the growth media, but this does not mimic respiratory exposures. Different methods to introduce aerosolized NPs to cells cultured at the air-liquid-interface (ALI) have been developed, but require specialized equipment and are associated with higher cost and time. Therefore, it is important to determine whether aerosolized setups induce different cellular responses to NPs than traditional ones, which could provide new insights into toxicological responses of NP exposure. This study evaluates the response of human alveolar epithelial cells (A549) to zinc oxide (ZnO) NPs after dry aerosol exposure in the Nano Aerosol Chamber for In Vitro Toxicity (NACIVT) system as compared to conventional, suspension-based exposure: cells at ALI or submerged. Similar to other studies using nebulization of ZnO NPs, we found that dry aerosol exposure of ZnO NPs via the NACIVT system induced different cellular responses as compared to conventional methods. ZnO NPs delivered at 1.0 µg/cm² in the NACIVT system, mimicking occupational exposure, induced significant increases in metabolic activity and release of the cytokines IL-8 and MCP-1, but no differences were observed using traditional exposures. While factors associated with the method of exposure, such as differing NP aggregation, may contribute toward the different cellular responses observed, our results further encourage the use of more physiologically realistic exposure systems for evaluating airborne ENM toxicity.

Keywords:

• Air-liquid interface
• NACIVT
• aerosol
• cell response
• toxicity

Acknowledgments

The authors would like to acknowledge Louise Gren for conducting the SEM analyses of the Si wafers from the NACIVT exposures. Tommy Cedervall is also acknowledged for the support provided for the DLS analysis and Wyatt Technologies for access to the DYNAMIC 7 Software. The authors also thank the Lund University Bioimaging Center (LBIC) for providing infrastructure support for the SEM analysis of the ZnO NP suspension and the cells from the submerged exposures, and Sebastian Wasserstrom for technical assistance.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was funded by AFA Insurance under Grant 160226. The EMPIR 18HLT02 AeroTox project is acknowledged for generous support (JR and MK). The EMPIR programme is co-financed by the Participating States and from the European Union's Horizon 2020 research and innovation programme. The Knut and Alice Wallenberg foundation is acknowledged for generous support (DEW).