Abstract 1341: Magnetic isolation and identification of exosomes using Fe/Au nanowires
Authors: Nemati Zohreh , Gage Thomas , Kouhpanji Mohammad Reza Zamani , Um Joseph , Donnelly Alicia , Shore Daniel , Makielski Kelly , Zhang Yali , Franklin Rhonda , Modiano Jaime F. , Stadler Bethanie J. 
Published: August 2019

We are developing segmented magnetic nanowires (MNWs) as a new platform for highly specific biolabels. We found that cancer cells internalize MNWs and package them into exosomes, which are then secreted for several days. These MNWs thus enable magnetic isolation of exosomes, which could prove useful in future diagnosis. Our immediate goals are to study how cells internalize MNWs, to determine the timing and reproducibility of exosome secretion, and to improve the magnetic isolation of exosomes. Following this work, we aim to use ferromagnetic resonance (FMR) to identify specific MNW biolabels, similar to radio frequency identification (RFID).

In this study, we incubated osteosarcoma (OSCA-8) cells with Fe/Au segmented MNWs with and without PEG coating for 48 hours. Internalization of MNWs as a function of concentration (5-40 µg/ml) was followed by fluorescence and transmission electron microscopy (TEM). We obtained quantitative estimates of MNW internalization by magnetic measurements. Our experiments indicated better internalization of the MNWs using PEG as a capping agent. As we increased the concentration of MNWs, both the number of cells with MNWs and the number of MNWs per cell increased. TEM images show that after uptake by cancer cells, MNWs were predominantly located within lysosomes, and they appeared to be fragmented into small segments of similar size as exosomes. These segments were mostly composed of either Fe or Au, suggesting that fragmentation occurred at or near the boundary of segments.

We used two different methods for exosome isolation: non-magnetic isolation (centrifuge and ExoQuick TC) as a control and magnetic isolation. We incubated OSCA-8 cells with different concentrations of MNWs (0 to 35 µg/ml), and exosomes were isolated for up to 11 days. We analyzed the exosome size distribution using a nanoparticle tracking analyzer (NanoSight) and found that exosomes isolated magnetically had similar size distributions as those isolated non-magnetically. A minimum concentration of 25 µg/ml MNWs in 3×105 cells was required for appreciable magnetic isolation. Increasing the concentration of MNWs progressively; however, isolated microvesicles that had wider and more heterogeneous size distributions.

Next, we successfully identified two different types of MNW biolabels by FMR. MNWs were fixed in a polymer that was placed onto an RFID chip. Each type of MNW exhibited a unique RF signature as the sample was exposed to an external magnetic field.

Our preliminary data show that MNWs appear to allow fast, inexpensive magnetic exosome isolation and is our future goal is MNW identification of exosomes. The methodology developed in this study should be transferable to develop comparable approaches to isolate and identify exosomes from virtually any type of cell.

Citation Format: Zohreh Nemati, Thomas Gage, Mohammad Reza Zamani Kouhpanji, Joseph Um, Alicia Donnelly, Daniel Shore, Kelly Makielski, Yali Zhang, Rhonda Franklin, Jaime F. Modiano, Bethanie J. Stadler. Magnetic isolation and identification of exosomes using Fe/Au nanowires [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 1341.