Isolating tumor exosomes (TEX) secreted by cancer cells can provide valuable information about the state of a tumor. Here, we present a method to rapidly isolate TEX using magnetic nanowires (MNWs). Specifically, two sets of Fe/Au segmented MNWs were used to isolate TEX released by canine osteosarcoma cell lines (OSCA 8,32,and 40). These MNWs were prepared by electrodeposition showcasing similar length (2.2(1) μm) and diameter (36(3) nm) but different Fe/Au segment thickness: 120(20)/30( 6) nm (sample A) and 28(7)/3(1) nm (sample B).Magnetic measurements indicate that we can effectively tune the magnetic response of the MNWs by changing their segment thickness, obtaining a more anisotropic behavior for sample A. The internalization of these MNWs by OSCA cells as a function of their concentration has been followed by fluorescence microscopy, and a concentration around 25 μg of Fe/Au MNWs per 3 × 10 5 cells has been defined as optimal. Electron microscopy images have revealed that, once internalized, these MNWs end up residing within lysosomes inside the cancer cells, where they tend to be degraded (especially the Fe segments) and fragmented into smaller pieces. Lower degradation for sample B has been observed and related to differences in the synthesis/functionalization process of both samples. We have hypothesized that these fragments of Fe/ Au MNWs are packaged into TEX released to the medium which can then be isolated via a magnetic stand. This has been tested by carrying out TEX isolation experiments on the OSCA cell and comparing the magnetically isolated TEX with those isolated by using conventional methods based on centrifugation. Nanoparticle tracking analysis (NanoSight) has confirmed that the TEX isolated with MNWs have a comparable size distribution and yield to those obtained by using conventional methods, indicating that our magnetic isolation method can consistently provide relatively high TEX yields in a low-cost and fast way.

Isolating and analyzing tumor-derived exosomes (TEX) can provide important information about the state of a tumor, facilitating early diagnosis and prognosis. Since current isolation methods are mostly laborious and expensive, we propose herein a fast and cost-effective method based on a magnetic nanoplatform to isolate TEX. In this work, we have tested our 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 we 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 our magnetic isolation method and analyzed with a Nanoparticle tracking analyzer (NanoSight). We 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.

The drive to comprehend nanomedicine and biology with a reliable technique for multiplexed detection of biological entities, such as biocompatible membranes, regenerative tissues, and cells, demands much of the current state-of-the-art technologies. Angular-dependent coercivity (ADC) and first-order reversal curve (FORC) measurements are frequently used for the identification of magnetic nanowires (MNWs), but a robust framework for quantitative demultiplexing of signals is still lacking. In this paper, we first extracted quantitative characteristics from ADC and FORC measured on samples including a single type of MNW. We then analyzed the ability of these characteristics for quantitative demultiplexing combinations of MNWs. Backfield remanence magnetization was determined as the most reliable characteristic for quantitative multiplexing applications. Our approach envisions an insightful pathway for accurate quantitative identification of biocompatible membranes labeled with MNWs, even if their magnetic signatures overlap. Very small volume ratios of multiplexed labels were detected without requiring fluorophores, which opens a future for cellular multiplexing as well.

Ferromagnetic Co35Fe65, Fe, Co, and Ni nanowires have high saturation magnetizations (Ms) and magnetic anisotropies, making them ideal for magnetic heating in an alternating magnetic field (AMF). Here, Au-tipped nanowires were coated with polyethylene glycol (PEG) and specific absorption rates (SAR) were measured in glycerol. SAR increased when using metals with increasing Ms (Co35Fe65 > Fe > Co > Ni), reaching 1610 ± 20 W/g metal at 1 mg metal/ml glycerol for Co35Fe65 nanowires using 190 kHz and 20 kA/m. Aligning these nanowires parallel to the AMF increased SAR up to 2010 W/g Co35Fe65. Next, Co35Fe65 nanowires were used to nanowarm vitrified VS55, a common cryoprotective agent (CPA). Nanowarming rates up to 1000 °C/min (5 mg Co35Fe65/ml VS55) were achieved, which is 20x faster than the critical warming rate (50°C/min) for VS55 and other common CPAs. Human dermal fibroblast cells exposed to VS55, and Co35Fe65 nanowire concentrations of 0, 1 and 2.5 mg Fe/ml all showed similar cell viability, indicating that the nanowires had minimal cytotoxicity. With the ability to provide rapid and uniform heating, ferromagnetic nanowires have excellent potential for nanowarming cryopreserved tissues.