- Selective Imaging of Late Endosomes with a pH-Sensitive Diazaoxatriangulene Fluorescent Probe
Antoine Wallabregue, Dimitri Moreau, Peter Sherin, Pau Moneva Lorente, Zdeňka Jarolímová, Eric Bakker, Eric Vauthey, Jean Gruenberg, Jérôme Lacour
J. Am. Chem. Soc. 2016, 138, 1752-1755
Late endosomes are a major trafficking hub in the cell at the crossroad between endocytosis, autophagy and degradation in lysosomes. Herein is disclosed the first small molecule allowing their selective imaging and monitoring in the form of a diazaoxatriangulene fluorophore 1a (hexadecyl side chain). The compound is prepared in 3 steps from a simple carbenium precursor. In nanospheres, this pH-sensitive (pKa 7.3) photochemically-stable dye fluoresces in the red part of visible light (601 and 578 nm, acid and basic forms respectively) with a quantum yield between 14-16 % and an excited state lifetime of 7.7-7.8 ns. Importantly, the protonated form 1a•H+ provokes a specific staining of late endosome compartments (pH 5.0–5.5) after 5h incubation with HeLa cells. Not surprisingly, this late endosome marking depends on the intraorganelle pH and changing the nature of the lipophilic chain provokes a loss of selectivity. Interestingly, fixation of the fluorophore is readily achieved with paraformaldehyde giving the possibility to image both live and fixed cells.
open archive unige:80718