Biological and Magnetic Contrast Evaluation of Shape-Selective Mn–Fe Nanowires

One-dimensional composite Mn-Fe oxide nanostructures of different sizes (nanoneedles, nanorods, and nanowires) were prepared by a linker-induced organization of manganese-doped iron oxide nanoparticles. The nanostructures were obtained by the treatment of MnFe₂O₄ nanoparticles in the presence of cystamine. The average lengths of nanoneedle, nanorod, and nanowire are approximately 400, 800, and 1000 nm, respectively. High-resolution transmission electron microscopy (HR-TEM), energy-dispersive X-ray (EDX) spectroscopy, and inductively coupled plasma-optical emission spectroscopy (ICP-OES) were employed to characterize the morphologies and the elemental contents of the nanostructures. As an example of their potential applications, these nanostructures were explored as the cell-labeling agents for magnetic resonance imaging (MRI). The magnetic contrast properties of the nanostructures were characterized by a 1.5 T (Tesla) whole body MR system. 10 mug/mL of the nanostructures caused substantial negative contrast. After in vitro incubation, the nanostructures could be effectively incorporated into the cells of a monocyte/macrophage cell line (RAW264.7). These cellspsila viability and proliferation potential were not affected when the labeling concentration was less than 50 mug/mL.