Membrane Potential-Independent Mitochondria-Specific Near-Infrared Fluorescent Probe via Nanoaggregate Formation

Near-infrared (NIR) fluorescent nanoaggregates are extremely beneficial for visualizing organelle structure and dynamics due to their minimal autofluorescence, cell damage, low phototoxicity, and excellent photostability. There are dozens of probes available to image mitochondria, one of the most important organelles in mammalian cells. However, most of the available probes are mitochondrial membrane potential (MMP)-dependent, which impairs mitochondrial protein function and induces cellular cytotoxicity. Herein, we report a cyanine-based self-assembled NIR fluorescent nanoaggregate (Cy-D) bearing a long hydrophobic C 10 alkyl chain for MMP-independent, efficient mitochondrial staining. These nanoaggregates exhibit good quantum yield, low toxicity, and excellent photostability inside the cellular environment. Our findings demonstrate that these nanoaggregates serve as effective fluorescent probe for monitoring mitophagy in plant cells. Furthermore, their efficient mitochondrial staining in both plant and mammalian cells highlights their potential as MMP-independent mitochondrial probe. Importantly, this nanoprobe remains effective under mitochondrial depolarization, making it a valuable tool for investigating mitochondrial dysfunction in numerous pathologies, including neurodegenerative and cancer diseases.