Fig. 5

a–d SOD and MDA assays on Caco-2 and A549 cells. Cells were incubated with 15 μg/ml and 45 μg/ml of TiO₂NPs and SiO₂NPs for 24 h, 48 h, 72 h, 96 h. The SOD assay used a tetrazolium salt for detection of superoxide radicals generated by xanthine oxidase and hypoxanthine. The standard curve was used as a positive control (data not shown). The MDA levels was detected by the quantification of MDA-TBA adduct (OD = 532 nm). Data reported as mean ± SD from three independent experiments are considered statistically significant compared with control (n = 8) for p value < 0.05 (< 0.05*, < 0.01**, and < 0.005***)