Methodological considerations when conducting in vitro, air–liquid interface exposures to engineered nanoparticle aerosols

Abstract

Little consistency exists in the methodology for toxicological testing of aerosolized nanoparticles used in in vitro, air-interfaced culture (AIC) exposure systems for engineered nanoparticles (ENPs) risk-assessment, preventing inter-laboratory comparisons to identify dose thresholds for adverse effects. These inconsistencies result from heterogeneity in particle types, exposure durations, exposure systems, and dose metrics reported. We screened 10,241 studies in the literature for toxicological assessment of ENPs, resulting in 110 publications included after meeting eligibility criteria. In this review, we critically analyzed methodology within these studies to answer whether: (1) the administered dose or the deposited dose correlated better with biological response, (2) a difference existed between various AIC exposure systems when depositing the same dose, (3) consistent results were generated for nanomaterials with similar physico-chemical properties, (4) the deposited dose in vitro correlated to the deposited dose in vivo, and (5) AIC studies reliably modeled acute toxicity in vivo. Methods used in delivering, measuring, and reporting ENP aerosol doses in vitro are summarized. Dosimetry and biological response comparisons of AIC, conventional suspensions, and in vivo exposures are discussed through case studies on silver, zinc oxide, titanium dioxide, and multi-walled carbon nanotube exposures. Finally, based on these findings, recommendations are offered for design of future AIC experiments to aid standardization and comparisons of results.

Keywords:

• Nanomaterials
• inhalation
• dosimetry
• exposure systems
• nanotoxicology
• in vivo
• air-interfaced culture

Acknowledgements

The authors would like to thank the five anonymous peer reviewers for their insights and expertise, which helped to enhance the content of this literature review.

Declaration of interest

The affiliation of the authors is as shown on the cover page. The authors were financially supported by Wagoner Foreign Study Scholarship (N. J. L.), Virginia Commonwealth University (L. E. S. and N. A. L.), 10.13039/100009238, and Whitaker International Program (N. A. L.)., 10.13039/100007852. This work was initiated at the Institute for Work and Health in Lausanne, Switzerland, and completed at Virginia Commonwealth University in Richmond, VA. The authors have sole responsibility for the writing and content of the paper. The authors declare that they have no competing interests.