Figure 4.

(A,B) Cell viability and (C,D) epithelial barrier integrity in air–liquid interface (ALI) cultures of A549 cells exposed to TiO₂ NP (µg/mL) by solution inoculation or aerosol: (A,C) NM-100; (B,D) NM-101. Cell viability and epithelial barrier integrity of ALI culture were assessed by resazurin assay and LY permeability assay, respectively. Doxorubicin (20 µM, 24 h of treatment) was used as positive control for the viability assay. LPS (100 ng/mL, 24 h of treatment) was used as positive control for monolayer integrity. Untreated cultures were included as negative control (CTRL). Data are reported as mean ± standard deviation (n_tests = 3). The symbols (**) and (***) indicate p values < 0.01 and < 0.001 vs. the untreated (negative) control (CTRL), respectively. Abbreviations: ALI, air–liquid interface; LPS, lipopolysaccharide; NM, nanomaterials.