Development of an in vitro model of human bronchial epithelial barrier to study nanoparticle translocation

Inhalation is the most frequent route of unintentional exposure to nanoparticles (NPs). Our aim was to compare different in vitro models of human lung epithelial monolayers for their suitability to assess the translocation of 50 nm fluorescently labelled silica NPs (50 nm-SiO2-FITC-NPs). Human bronchial epithelial cell lines NCI-H292 and Calu-3 as well as human alveolar cell line A549 were seeded onto Transwell filters (TF) separating the well into an apical and a basal compartment. Measurements of the transepithelial electric resistance and monitoring the paracellular transport of a fluorescent marker (Lucifer Yellow) have shown that only Calu-3 cells formed a tight epithelium. In the absence of cells 4% of the initially applied NP concentration was found to cross the TF but the majority remained trapped inside the filter. After 24 h of treatment, 50 nm-SiO2-FITC-NPs were taken up by all cell types but their translocation was inversely correlated to the efficiency to prevent LY passage: translocation represented 3% of the initially apically applied NP concentration for Calu-3 cells, 9% for NCI-H292 cells and 35% for A549 cells. In conclusion, 50 nm-SiO2-FITC-NPs can cross different bronchial epithelial barriers, but the Calu-3 cell line appears to be the most relevant model for studying NP translocation.