Fig. 3
Cellular reactive oxygen species (ROS) production assessed by the fluorescent probe DCFDA in BEAS-2B cells after 3, 6 and 24-h exposure to coarse (A–J), medium (B–K) and fine (C–L) size fractions of U-CNF (A–C), T-CNF (D–F), C-CNF (G–I) and E-CNF (J–L). Data are expressed as relative fluorescence units (RFU) and presented as the mean ± se (N = 2 independent experiments). Asterisks designate statistically significant differences compared with the untreated cultures at *p < 0.05, **p < 0.01, ***p < 0.001 and ****p < 0.0001. Daggers designate statistically significant linear regression at †††p < 0.001 and ††††p < 0.0001. The positive control, H2O2 (2 mM), induced a statistically significant increase in ROS production over the negative control values in all the experiments performed (7.9 ± 0.4-fold increase; p < 0.003) confirming the validity of the experiments (data not shown)