In Vivo Tracking of Multiple Tumor Exosomes Labeled by Phospholipid-Based Bioorthogonal Conjugation

Abstract

Exosomes are cell-secreted nanoscale membrane vesicles that play critical roles in many pathophysiological processes. The clinical value of exosomes is under intense investigation, yet current knowledge regarding their in vivo properties is very limited because of the lack of efficient labeling techniques. Here, we report a phospholipid-based bioorthogonal labeling strategy to endow exosomes with optical probes without influencing their native biological functions. We investigated the dynamic in vivo biodistribution and organotropic uptake of multiple tumor exosomes in a single mouse. The results indicate that the exosomes derived from different cell lines show specific organotropic uptake. This phospholipid-based labeling strategy opens a new window to directly visualize and monitor exosome trafficking in living systems and holds great promise for exploring exosome-involved biological events such as cancer metastasis.

Biodistribution of extracellular vesicles following administration into animals: A systematic review

“…15 studies investigated the presence of small‐EVs in the circulation following IV administration, but of these only six studies reported comparable parameters (Imai et al., 2015; Lai et al., 2014; Matsumoto et al., 2017; Morishita et al., 2015; Takahashi et al., 2013; Zhang et al., 2018). To enable comparison, we combined the data into three time‐periods; ‘2 min’, ‘5 to 30 min’, and ‘1 h and above’ post injection.…”

Exploiting the Natural Properties of Extracellular Vesicles in Targeted Delivery towards Specific Cells and Tissues

“…Therefore, novel approaches have been developed to improve EV imaging. As an alternative to the commonly used fluorescence probes, Zhang et al 2018 proposed indirectly labelling EVs by covalently conjugating membrane phospholipids with fluorescent markers, which permits reducing the non-specific extracellular labelling [129]. By taking advantage of the sulfhydryl groups on the EV surface, maleimide-conjugated Alexa-fluor dyes were covalently added to the EV surface by simple incubation [130].…”

Systematic characterization of extracellular vesicle sorting domains and quantification at the single molecule – single vesicle level by fluorescence correlation spectroscopy and single particle imaging

“…Additionally, in salt‐containing buffers or media, most of these lipid stains readily form micelles or aggregates with partially overlapping physicochemical properties to EVs, thereby providing difficulties to be removed and thus a risk for additional artefacts [29]. To overcome these limitations, the field is turning towards more specific and less invasive strategies such as expression of reporter protein‐tagged EV surface markers [17,31,33–36] or metabolic biorthogonal conjugation [37] within EV‐producing cells. These approaches have been successfully used for visualizing EVs in vivo and in vitro to shed light on the vesicular biogenesis and biodistribution processes.…”