Magnetic Separation of Cell-Secreted Vesicles with Tailored Magnetic Particles and Downstream Applications

The analysis of the receptors on the surface of the cell-secreted vesicles provides valuable information of the cell signature and may also offer diagnosis and/or prognosis of a wide range of diseases, including cancer. Due to their low concentration, conventional procedures for extracellular vesicle (EV) detection usually require relatively large sample volumes, involving preliminary purification or preconcentration steps from complex specimens. Here, we describe the separation and preconcentration in magnetic particles of extracellular vesicles obtained from cell culture supernatants from MCF7, MDA-MB-231, and SKBR3 breast cancer cell lines, human fetal osteoblastic cell line (hFOB), and human neuroblastoma SH-SY5Y cell line, as well as exosomes from human serum. The first approach involves the covalent immobilization for the exosomes directly on micro (4.5 μm)-sized magnetic particles. The second approach is based on tailored magnetic particles modified with antibodies for further immunomagnetic separation of the exosomes. In these instances, micro (4.5 μm)-sized magnetic particles are modified with different commercial antibodies against selected receptors, including the general tetraspanins CD9, CD63, and CD81 and the specific receptors (CD24, CD44, CD54, CD326, CD340, and CD171). The magnetic separation can be easily coupled with downstream characterization and quantification methods, including molecular biology techniques such as immunoassays, confocal microscopy, or flow cytometry.