Development of a Novel Air–Liquid Interface Culture System to Investigate the Effects of Nanoplastics on Alveolar Epithelium

The presence of micro- and nano-plastics in the atmosphere has become evident, necessitating risk assessments for humans. Although submerged culture systems are often used to evaluate the safety of fine particles, some plastics float in culture media owing to their low density. Therefore, developing an air–liquid interface (ALI) system capable of assessing plastic exposure is essential. In this study, we developed a chamber for exposing nanoplastic aerosols to ALI cultures and evaluated their toxicological effects. A glass exposure chamber integrated with a donut-shaped culture plate was constructed. The aerosols were introduced through four upper inlets and discharged through five lower outlets. The culture temperature was controlled by circulating water through the inside space of the plate. A nano-polystyrene (PS) suspension was nebulized and introduced into the chamber. Exposure of co-culture of Calu-3 and U937 cells to nano-PS aerosols resulted in a spatial mass concentration-dependent increase in hydrogen peroxide concentration in the culture medium, elevated expression of inflammatory cytokines and chemokines (including IL-6 and IL-8) in Calu-3 cells and decreased trans-epithelial electrical resistance. These findings indicate that nano-PS aerosol exposure induces oxidative stress and inflammatory responses, leading to alveolar barrier dysfunction. Overall, the developed ALI exposure system provides a useful in vitro culture system for evaluating the safety of nanomaterials, including nanoplastics, and highlights the importance of aerosol-based approaches in assessing the toxicity of respirable particles.