Loading of metal isotope-containing intercalators for mass cytometry-based high-throughput quantitation of exosome uptake at the single-cell level.

Nanometer-sized exosomes are being widely studied as cell-to-cell communicators and versatile drug vehicles. Characterizations of the biodistribution of these exosomes are essential for the evaluation of their biological functions and drug delivery efficacy. However, current technologies for exosome tracking rely on fluorescence and have the disadvantages of being low throughput due to the limited number of available channels and spectral spillover. Here, we reported the development of an engineering approach that involves loading of metal isotope-containing intercalators into exosomes to quantify exosome uptake at the single-cell level. We demonstrate that mass cytometry in conjunction with highly multivariate cellular phenotyping enables high-throughput identification of the in vivo fate of exosomes. Inspired by these insights into cellular distribution, we optimized the administration methods for exosome-based drug delivery, verifying the anticancer efficacy of these exosomes in a mouse model of breast cancer. The evaluation of exosome's fate in vivo at the single-cell level provides valuable insights into the functions of exosomes in vivo and facilitates the improvement of exosome-based therapy.