Preparation of ferromagnetic microcapsules for hyperthermia using water/oil emulsion as a reaction field

Hyperthermia is a minimally invasive cancer treatment. As hyperthermia thermoseeds, ferromagnetic microcapsules of 20–30 μm in diameter have attracted much attention since their embolization effect cuts off the nutrition supply into cancer cells, ensuring that the microcapsules efficiently reach the tumor. In the present study, ferromagnetic microcapsules were prepared via iron hydroxide precipitation from a water/oil emulsion and subsequent hydrothermal treatment. The fundamental conditions for obtaining microcapsules of suitable size were investigated. The diameter of the obtained microcapsules tended to decrease as rotation speed increased during emulsion preparation or surfactant concentration in the oil phase. The sphericity of the microcapsules was improved at low surfactant concentration. A large amount of 20–30 μm-diameter magnetite microcapsules were obtained when the rotation speed and surfactant concentration were fixed at 1500 rpm and 0.35 mass%, respectively. The obtained microcapsules embedded in agar phantom exhibited heat generation under an alternating magnetic field.