ExoTracker – a low-pH-activatable fluorescent probe for labeling exosomes and monitoring endocytosis and trafficking

Exosomes (a type of nanoscale extracellular vesicle with size range 30 ~ 100 nm) mediate the cell-cell communication by transferring functional biomolecules, and play an important role in various physiological and pathological processes, including tumor development and progression. New, more effective techniques for visualization and tracking of exosomes in cell-cell communication are highly desirable. However, the application of commonly used exosome-labeling probes is limited by the need for specificity and strict pH tolerance. Researchers from Jiangnan University describe here the construction and testing of a novel exosome labeling fluorescent probe termed “ExoTracker”, which displayed low cytotoxicity, and high fluorescence intensity in acidic environments. ExoTracker was applied for effective tracking of exosomes in cell endocytosis.

Confocal 3D reconstruction of CFDA-SE/ ExoTracker dual-labeled exosomes
in HCV29 cells in pH 7.4 PBS solution


a) 3D reconstruction (by ImageJ program) of confocal image. b) Z-axis segmentation of 3D reconstruction image. Scale bar: 10 μm.

Zhou X, Zhang J, Song Z, Lu S, Yu Y, Tian J, Xiang Li X, and Feng Guan F. (2020) ExoTracker: A Low-pH-activatable Fluorescent Probe for Labeling Exosomes and Monitoring Endocytosis and Trafficking. Chem Comm [Epub ahead of print]. [abstract]

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