The link between delivered aerosol dose and inflammatory responses: Exposing a lung Cell Co-Culture system to selected Allergens and irritants

Traditional in vivo inhalation studies to inform hazard identification and risk assessment are time-intensive and financially expensive. Cell culture models combined with aerosol exposure systems have shown promise as surrogates in screening assays when multiple substances require preliminary information on hazard potential associated with aerosolized materials. This paper presents two different aerosol exposure apparatuses: a settling chamber and a gentle impactor. Both apparatuses have been demonstrated for aerosol delivery capable of exposing cells in culture at the air-liquid interface. The settling chamber was constructed with simple design specifications, but exhibited a low deposition efficiency. The gentle impactor required a more sophisticated design based on aerosol dynamics of target size for the droplet delivery, but ultimately produced 64.25-fold greater deposition efficiency than the settling chamber. This led to a shorter exposure duration for the same dosage. It also enabled consistent exposure to the same sized aerosols. From these results, the gentle impactor shows promise as a high-throughput exposure tool that could be used in conjunction with cell-based co-culture models. Using a triple cell co-culture model of epithelial, dendritic, and macrophage cell-types, the induced inflammatory markers produced a more definitive dose-response for known irritants and positive indication for sensitizers. The materials tested include toluene-2,4-diisocyanate and trimellitic anhydride as known respiratory sensitizers; silica as a known respiratory irritant; and d-limonene as a known dermal sensitizer. Conversely, when using single cell monolayers, no significant different responses in inflammatory biomarkers was observed, suggesting cellular cross-talk is important. Evaluation of the ability to deliver aerosolized substances consistently and measure cytotoxicity and inflammatory endpoints is possible and demonstrates a potential high throughput screening tool.