Iron Nanoparticles for Magnetic Imaging Applications

Extensive research on iron oxide nanoparticles for various applications including nanomedicine, energy applications, environmental remediation, and magnetic imaging have previously been performed. Many are currently FDA approved as magnetic resonance imaging contrast agents and tracers for magnetic particle imaging applications. Magnetic properties of such materials are crucial to obtain good contrast and resolution. However, studies have shown the magnetic properties of iron oxide nanoparticles are less in comparison to those found in pure iron nanoparticle.

This research involves the synthesis and characterization of iron nanoparticles for applications in magnetic resonance imaging contrast agents, magnetic particle imaging tracers, and therapeutic agents for magnetic hyperthermia. Synthetic procedures include a thermal decomposition of iron pentacarbonyl and co-precipitation of iron salts to produce iron nanoparticles. Characterization methods include transmission electron microscopy (TEM), superconducting quantum interference magnetometry (SQUID), Mössbauer spectroscopy, X-ray diffraction (XRD), inductively coupled plasma optical emission spectroscopy (ICP-OES), zeta potential measurements, and cytotoxicity tests.

Monodispersed particles with an average size of 14 nm consisting of an iron core and iron oxide shell were obtained using thermal decomposition of iron pentacarbonyl. The particles were successfully coated in a DSPE-mPEG polymer, which were stable for up to 3 months when refrigerated. The particles exhibited superparamagnetic properties with high magnetic saturation and displayed low cytotoxicity. Iron particles synthesized in this method display good potential for magnetic resonance imaging applications or usage in magnetic hyperthermia treatment. However, larger particles between 18 to 20 nm in size are needed to obtain optimal resolution signals for MPI applications.

From a co-precipitation synthesis of iron salts, particles displayed high magnetic saturation, and pure iron samples were obtained after further solid-gas reduction under H₂ gas was performed. However, particles were large and sintered together, making them unfavorable for further MPI or cell viability tests. Coating particles with silica before solid-gas reactions at high temperatures showed promise in decreasing aggregation of particles. Further work is needed in order to determine the proper coating thickness to allow for optimal reduction under H₂ gas.