Electrodeposited Fe and Fe-Au nanowires were studied for potential as MRI contrast agents, especially for T-weighted imaging. Transverse relaxivities up to r = 77.1 mM Fe s (at 1.5 T) were achieved when Fe-Au nanowires were coated with thiol and carboxylic acid functionalized poly(ethyleneglycol). T-Weighted images (9 T) verified successful contrast.

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.

We present non-cytotoxic, magnetic, Arg-Gly-Asp (RGD)-functionalized nickel nanowires (RGD-nanowires) that trigger specific cellular responses via integrin transmembrane receptors, resulting in dispersal of the nanowires. Time-lapse fluorescence and phase contrast microscopy showed that dispersal of 3 μm long nanowire increased by a factor of 1.54 with functionalization by RGD, compared to polyethylene glycol (PEG), through integrin-specific binding, internalization and proliferation in osteosarcoma cells. Further, a 35.5% increase in cell density was observed in the presence of RGD-nanowires, compared to an increase of only 15.6% with PEG-nanowires. These results promise to advance applications of magnetic nanoparticles in drug delivery, hyperthermia, and cell separation where uniformity and high efficiency in cell targeting is desirable.

Among all transition metals magnetic alloys, Co 35 Fe 65 possesses the highest saturation magnetization B S = 2.45 T at room temperature given by the so-called "Slater-Pauling limit". For controlled electrodeposition of Co 35 Fe 65 nanowire arrays the following parameters were found to be optimal: electrolyte solution with 1-2 mM malonic acid (MA), ionic ratio Fe +2 /Co +2 = 2.0, growth rate, and pulsed potential deposition with time-on (2.5 s) at the potential of −1.15 V/SCE and time-off (1.0 s) at −0.70 V/SCE. These arrays were deposited inside anodic aluminum oxide (AAO) templates that contained columnar nanopores with diameters either 35 or 200 nm. Cyclic voltammetry was used in solution with and without MA and reaction mechanism was proposed to explain the critical role of MA in electrodeposition of CoFe alloys. In addition to uniform deposition of stechiometric Co 35 Fe 65 alloys, a selectivity ratio, (SR) ∼1.0, were achieved, which means that the atomic ratio of Fe/Co in the nanowire matched the molar ratio of Fe +2 /Co +2 in the electrolyte. The magnetic behavior of the subsequent 2.45 T Co 35 Fe 65 nanowire arrays showed that the shape and magnetostatic anisotropies dominated the effective anisotropy, and the impact of magnetocrystalline and magnetelastic anisotropies field was very small. 1 The highest saturation magnetization of all transition-metal (TM) alloys at room temperature shows Co 36 Fe 65 alloy with respective saturation magnetization of B s = 2.45 T, which is commonly referred to us as the "Slater-Pauling limit".2 Thin films of these alloys, obtained either by electrochemical deposition (ED) or called sputter deposition, are currently used in high areal recording density (HRD) heads including longitudinal (LMR), perpendicular (PMR), and heat assisted (HAMR) magnetic recording. In fact, about 15 years ago Seagate Technologies was first in the recording head industry to introduce 2.4 T CoFe as the longitudinal writer pole material-which was fabricated by electrodeposition. 3 The advantages of electrochemical vs. sputtering deposition include reduced process content, reduced variance and reduced cost. Importantly, controlled electrodeposition is possible even into high aspect ratio of templates including anodized aluminum oxide-AAO, diblock copolymers-DBC, carbonate membranes, and porous silicone. Porous AAO templates are particularly attractive since the pore diameters can be 10-300 nm with pore densities in the range of 10 9 to 10 11 cm −2 . 4 Ferromagnetic nanowire arrays have been used as a miniaturized devices in electronics and optics. 5 In addition, such nanowires have a promising biomagnetic applications like biosensing, cell separation, MRI contrast agents and magnetic hyperthermia. [6][7][8][9][10] Most biomagnetic studies have been limited to nanometer iron-oxide based nanoparticles for MRI imaging and magnetic hyperthermia.6 However, the low saturation magnetization of the bulk iron-oxides (e.g. B s ∼0.5 T for Fe 2 O 3 11 ) prevents them from becoming highly efficient in hypertherm...

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.