Enzymatic preparation of hollow magnetite microspheres for hyperthermic treatment of cancer

Ferrimagnetic materials can be expected to be useful as thermal seeds for hyperthermic treatment of cancer, especially where the cancer is located in deep parts of body, as they can generate heat by magnetic hysteretic loss when they are placed in an alternating magnetic field. In this study, hollow magnetite (Fe₃O₄) particles were prepared using an enzymatic reaction of urease. A hollow particle was obtained by using a Pasteur pipette. The particle was 500 μm in size and was composed of Fe₃O ₄. Its saturation magnetization and coercive force were 57 emu·g^-1 and 183 Oe, respectively. Its heat generation under an alternating magnetic field of 300 Oe at 100 kHz was estimated to be 45 W·g^-1. Microspheres 30 μm in diameter were also successfully obtained by using a spray gun.