Figure 4

ROS production measured using the DCFH-DA assay following a 4 h exposure of A549 cells (A, B, means ± SEM of n = 3), BEAS-2B cells (C, D, means ± SEM of n = 3) and NHBE cells (E, F means ± SEM of n = 4) to charged Ag and Au NPs. Spearman’s rank coefficients were calculated for each NP to assess possible charge dependent increases in ROS production. In addition, the coefficients of the highest concentrations of each NP surface charge were calculated to determine if ROS production was charge dependent. P-values * < 0.05, ** < 0.01.