Preparation of Magnetic Iron Oxide Nanoparticles for Hyperthermia of Cancer in a FeCl2-NaNO3-NaOH Aqueous System

Magnetic iron oxide nanoparticles (MIONPs) were synthesized in a FeCl 2—NaNO3—NaOH aqueous system under various initial Fe2+/NO- 3 molar ratios (α) and Fe 2+/OH- molar ratios (β) in order to clarify the effects of the initial molar ratio of reactants on the reaction mechanism. The Fe 2+/NO- 3 /OH- molar ratio of 3 : 1 : 5 led to the formation of magnetic nanoparticles mainly composed of magnetite (Fe3O4) and maghemite (γ-Fe2O3). The 36 nm sized γ-Fe2O3 and 413 nm sized Fe 3O4 were obtained by changing the order in which NaNO 3 was added to a NaOH solution. The in vitro heat generations of the resulting MIONPs in an agar phantom were measured under an alternating magnetic field (100 kHz, 23.9 kA/m). The temperature rise (ΔT) of the agar phantom for the 36 nm sized γFe2O3 was 55°C in the first 140 s, with a concentration of 58 mg Fe/mL. Our results showed that it is possible to prepare MIONPs with high heating efficiencies under optimal conditions using the present method.