Nanoparticle analysis of circulating cell-derived vesicles in ovarian cancer patients.

Cell-derived vesicles are recognized as essential components of intercellular communication, and many disease processes are associated with their aberrant composition and release. Circulating tumor-derived vesicles have major potential as biomarkers; however, the diagnostic use of exosomes is limited by the technology available for their objective characterization and measurement. In this study, we compare nanoparticle tracking analysis (NTA) with submicron particle analysis (SPA), dynamic light scattering (DLS), and electron microscopy (EM) to objectively define size distribution, number, and phenotype of circulating cell-derived vesicles from ovarian cancer patients. Using the NanoSight LM10 instrument, cell-derived vesicles were visualized by laser light scattering and analyzing Brownian motion of these vesicles captured by video. The NTA software calculates the size and total concentration of the vesicles in solution. Using vesicles isolated from ovarian cancer patients, we demonstrate that NTA can measure the size distributions of cell-derived vesicles comparable to other analysis instrumentation. Size determinations by NTA, SPA, and DLS were more objective and complete than that obtained with the commonly used EM approach. NTA can also define the total vesicle concentration. Furthermore, the use of fluorescent-labeled antibodies against specific markers with NTA allows the determination of the "phenotype" of the cell-derived vesicles.