Size and shape characterization of hydrated and desiccated exosomes
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Exosomes are stable nanovesicles secreted by cells into the circulation. Their reported sizes differ substantially, which likely reflects the difference in the isolation techniques used, the cells that secreted them, and the methods used in their characterization. We analyzed the influence of the last factor on the measured sizes and shapes of hydrated and desiccated exosomes isolated from the serum of a pancreatic cancer patient and a healthy control. We found that hydrated exosomes are close-to-spherical nanoparticles with a hydrodynamic radius that is substantially larger than the geometric size. For desiccated exosomes, we found that the desiccated shape and sizing are influenced by the manner in which drying occurred. Isotropic desiccation in aerosol preserves the near-spherical shape of the exosomes, whereas drying on a surface likely distorts their shapes and influences the sizing results obtained by techniques that require surface fixation prior to analysis.
KeywordsHydrated and desiccated exosomes Size and shape characterization
The authors are indebted to Brian F. Woodfield of Brigham Young University (Department of Chemistry) for providing access to the NTA instrument. The authors acknowledge financial support from the National Science Foundation (award number IGERT-0903715) and the University of Utah (Department of Chemical Engineering Seed Grant and the Graduate Research Fellowship award).
M.S. and P.S.B. conceived the study, R.R. isolated exosomes, V.S.C. and R.R. performed NTA measurements, DLS measurements were performed by V.S.C. and M.S, D.M.B performed cryo-TEM imaging, SEM imaging was performed by Y.J. and V.S.C., electrospray DMA measurements were performed by Y.H.T., V.S.C., L.F.P., and M.S., V.S.C. and M.S. analyzed the experimental results; A.E.B. wrote the MATLAB code to analyze the imaged exosomes, M.S. performed statistical analysis, and V.S.C. and K.J.B. performed manual sizing of the imaged exosomes. The manuscript was written by V.S.C. and M.S., and was edited by all authors.
Conflict of interest
The authors declare that they have no competing financial interests.
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