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Multispectral Optical Tweezers for Biochemical Fingerprinting of CD9-Positive Exosome Subpopulations
journal contribution
posted on 2017-03-27, 00:00 authored by Randy P. Carney, Sidhartha Hazari, Macalistair Colquhoun, Di Tran, Billanna Hwang, Michael S. Mulligan, James D. Bryers, Eugenia Girda, Gary S. Leiserowitz, Zachary J. Smith, Kit S. LamExtracellular
vesicles (EVs), including exosomes, are circulating
nanoscale particles heavily implicated in cell signaling and can be
isolated in vast numbers from human biofluids. Study of their molecular
profiling and materials properties is currently underway for purposes
of describing a variety of biological functions and diseases. However,
the large, and as yet largely unquantified, variety of EV subpopulations
differing in composition, size, and likely function necessitates characterization
schemes capable of measuring single vesicles. Here we describe the
first application of multispectral optical tweezers (MS-OTs) to single
vesicles for molecular fingerprinting of EV subpopulations. This versatile
imaging platform allows for sensitive measurement of Raman chemical
composition (e.g., variation in protein, lipid, cholesterol, nucleic
acids), coupled with discrimination by fluorescence markers. For exosomes
isolated by ultracentrifugation, we use MS-OTs to interrogate the
CD9-positive subpopulations via antibody fluorescence labeling and
Raman spectra measurement. We report that the CD9-positive exosome
subset exhibits reduced component concentration per vesicle and reduced
chemical heterogeneity compared to the total purified EV population.
We observed that specific vesicle subpopulations are present across
exosomes isolated from cell culture supernatant of several clonal
varieties of mesenchymal stromal cells and also from plasma and ascites
isolated from human ovarian cancer patients.