Figure 4.

Cytotoxicity of the tested engineered nanoparticles (ENP) (SnO₂, ATO, CeO₂ and ZrO₂) in human alveolar epithelial cells under submerged conditions being exposed for 24 h. Lactate dehydrogenase release (LDH) release (A) and WST-1 reduction (B) assays were carried out after 24 h exposure to the NP suspensions prepared in serum-free cell culture medium. Data are expressed as mean ± standard deviation (n = 3–4). LDH release values were normalised considering the positive control (total LDH release; cells lysed with 2% Triton X-100), while WST-1 reduction values were normalised considering the negative control. Data was analysed by the one-way analysis of variance (ANOVA) test followed by the Dunnett’s post hoc test for multiple comparisons. * p ≤ 0.05, ** p ≤ 0.01 and *** p ≤ 0.001 vs. negative control. PC: Positive control.