Next, we investigated whether NRB-AF12 and ER-Tr could label endosomes and lysosomes. For this purpose, we performed live cell imaging experiments in LX2 cells using a commercial fluorescent probe which has been previously demonstrated to highlight vesicles involved in endocytosis. As shown in Figure 7, we could not find any staining of endocytic vesicles when cells were loaded with ER-Tr (Pearson's coefficient: −0.33 ± 0.05 and −0.43 ± 0.04, respectively for endosomes and lysosomes; n ≥ 10). In contrast, NRB-AF12 showed an appreciable co-localization rate with both endosomal and lysosomal vesicles (Pearson's coefficient 0.25 ± 0.13 and 0.15 ± 0.15, respectively; n ≥ 10). Interestingly, the data revealed a high index of dispersion of the co-localization coefficients (CI 95%: −0.05 – 0.55 and −0.19 – 0.5, for endosomes and lysosomes respectively; n ≥ 10), indicating that not all endosomes/lysosomes vesicles were stained by the dye.