Evaluation of lysosomal activation in SWCNT-exposed cells. Panel a: Epi-fluorescence images of macrophages unexposed (upper line) or exposed (lower line) to 50 μg/ml SWCNT for 24 hours stained with Acridine Orange (for lysosomes, in red) and DAPI (RNA/DNA, in green). Merge: combination of Acridine Orange and DAPI staining (overlapping appeared yellow). Panel b: Cathepsin activity in macrophages exposed to SWCNT for 3 hours. *: p < 0.001 between groups. Panel c: Western Blot images of LAMP-1 (120 kDa) and Cathepsin B (37 kDa) expression in macrophages exposed for 24 hours to SWCNT. ß-Actin is given as internal standard. Panel d: quantification of LAMP-1 and Cathepsin B expression, normalized to ß-Actin expression. *: p < 0.05 between groups.