Abstract
Selective imaging of cellular organelles is a rapidly expanding field of research. Within this context we describe the development of two novel profluorescent probes, MitoP-2 and MitoP-3, for the precise staining of mitochondrial compartments. Herein, we demonstrate that caged, non-fluorescent styryl-benzothiazole probes harbouring a p-nitrobenzyl motif can be converted into their parent fluorophore under the action of the nitroreductase (NTR) enzyme. Two probes, MitoP-2 and MitoP-3, exhibited a turn-ON fluorescence signalling in NTR enzymatic assays. In addition, they also proved successful in the staining of the mitochondria in cellular experiments under normoxic conditions. Interestingly, while MitoP-2 and MitoP-3 structures only differ by the presence of a cationic mitochondrial-targeting unit, both were equally efficient in the staining of mitochondria. Hence, an activity-based approach (MitoP-2) is sufficient for the precise targeting of mitochondria and the use of cationic mitochondria-targeting units (phosphonium present on MitoP-3) can be considered superfluous in this case.