Isolation of cancer-derived exosomes using a variety of magnetic nanostructures

Isolating and analyzing tumor-derived exosomes (TEX) can provide important information about the state of a tumor, facilitating early diagnosis and prognosis. Because current isolation methods are mostly laborious and expensive, University of Minnesota researchers propose a fast and cost-effective method based on a magnetic nanoplatform to isolate TEX. In this work, they have tested their method using three magnetic nanostructures: (i) Ni magnetic nanowires (MNWs) (1500 × 40 nm), (ii) Fe₃O₄ nanorods (NRs) (41 × 7 nm), and (iii) Fe₃O₄ cube-octahedral magnetosomes (MGs) (45 nm) obtained from magnetotactic bacteria. The magnetic response of these nanostructures has been characterized, and the researchers have followed their internalization inside canine osteosarcoma OSCA-8 cells. An overall depiction has been obtained using a combination of Fluorescence and Scanning Electron Microscopies. In addition, Transmission Electron Microscopy images have shown that the nanostructures, with different signs of degradation, ended up being incorporated in endosomal compartments inside the cells. Small intra-endosomal vesicles that could be precursors for TEX have also been identified. Finally, TEX have been isolated using this magnetic isolation method and analyzed with a Nanoparticle tracking analyzer (NanoSight). The researchers observed that the amount and purity of TEX isolated magnetically with MNWs was higher than with NRs and MGs, and they were close to the results obtained using conventional non-magnetic isolation methods.

Fluorescence images of (a) Ni MNWs and (b) Fe₃O₄ NRs inside OSCA-8 cells.