Fig. 4

Response of THP-1 macrophages to the first set of MWCNTs. Panel A WST-1 assay in THP-1 cells after 24 h of exposure to increasing applied doses of MWCNTs (mean ± SD; n = 4 experimental replicates). Samples with the same letter do not have a statistically different activity [two-ways ANOVA followed by Tukey’s multiple comparison test (mean effect)]. Panel B IL-1β secretion by THP-1 cells after 24 h of exposure to increasing applied doses of chemically purified MWCNTs (mean ± SD; n = 4 experimental replicates). Samples with the same letter do not have a statistically different activity [two-ways ANOVA followed by Tukey’s multiple comparison test (mean effect]). Panel C Turbidity kinetics of the different MWCNT samples suspended in serum-free RPMI at 50 μg/l (n = 2–6 experimental replicates). Symbols with the same letter are not statistically different (mixed effect model followed by Tukey’s test). Panel D Femtosecond pulsed laser signal of deposited MWCNTs after 24 h in the absence (w/o) of cells (a.u., arbitrary unit; mean ± SD; n = 3 experimental replicates). Panel E Femtosecond pulsed laser signal of deposited MWCNTs after 24 h in the presence of THP-1 cells (a.u., arbitrary unit; mean ± SD; n = 3 experimental replicates). Columns with the same letter are not statistically different (one-way ANOVA followed by Tukey’s multiple comparison test)