Synthesis and Characterization of Iron Oxide Particles for Medical Applications

Two kinds of iron oxide particles—spherical cobalt-containing iron oxide particles with spinel structure and platelet γ-Fe₂O₃ particles—were synthesized for medical applications. The particle size of the spherical cobalt-containing iron oxide particles was about 20 nm regardless of the coercive force that was varied in the range of about 4.0 to 39.0 kA/m by varying the Co content. The size and coercive forces of the platelet γ-Fe₂O₃ particles were in the range of about 30 to 100 nm and about 7.6 to 13.5 kA/m, respectively. The temperature-raising properties were evaluated for water dispersion of these particles under different AC magnetic fields and frequencies to apply hyperthermia or thermoablation using hysteresis-loss heating of ferrimagnetic particles. Heat generation in spherical cobalt-containing iron oxide particles was based on both hysteresis-loss and Brownian relaxation. Platelet γ-Fe₂O₃ particles showed heat generation completely based on hysteresis-loss.