Metallic Iron Nanoparticles for MRI Contrast Enhancement and Local Hyperthermia

The synthesis and characterization of bis-carboxyl-terminated PEG-coated FeNPs with magnetization greater than that of iron oxide nanoparticles (IONP) with comparable particle size was reported. Using concentrated reagents and the reaction kinetics afforded by the simultaneous introduction of reagents in the junction, a highly uniform particle size distribution is obtained. The higher magnetization and soft ferromagnetic nature shown by the novel FeNPs is evident from the magnetization curves. Increased magnetization afforded by the FeNPs allows for heat dissipation at frequencies in the safe range, while for IONP much higher frequencies are required to facilitate the same thermal dose. It is also shown that local hyperthermia is achievable with the FeNPs while IONPs require a dose in excess of 20-fold or greater to achieve the same temperature range.