Temporal Differentiation of Extracellular Vesicles by Metabolic Glycan Labeling-Assisted Microfluidics

Extracellular vesicle (EV)/exosome secretion is a dynamic process that tunes the cellular communication for response to internal and external cues. The selective enrichment of a newly synthesized EV/exosome has been hindered by the basic fact that all EVs/exosomes, new and old, share the similar inherent parameters and thus are indistinguishable. Here, we developed a method by cotranslational introduction of azide groups into EV/exosome proteins as a timestamp and label them with biotin tag by click chemistry, to separate the newly synthesized EVs/exosomes from preexisting populations by streptavidin-modified herringbone microfluidic chip. For mouse model of anti-PD-L1 immunotherapy, the level of newly synthesized PD-L1+ EVs detected by the developed approach was superior to the total PD-L1+ EVs from mixed time sources (quantified by classical method) for tumor progression. This method makes it possible to address the temporal characteristics of newly synthesized EVs/exosomes in cell and in vivo, for studying EV/exosome secretion to respond to specific stimuli.