Magnetite fine particles highly loaded PMMA microspheres for hyperthermia of deep-seated cancer

Poly(methyl methacrylate) (PMMA) microspheres several tens micrometers in diameter, containing highly dispersed sub-micron sized magnetite (Fe ₃O₄) particles, were successfully prepared via an emulsion polymerization process. Both oleic acid and sodium olate acted as suitable agents for high dispersion of the Fe₃O₄ particles in the starting monomer solution (MMA). Spherical PMMA particles encapsulating 65-72 mass% (30-38 vol%) of the Fe₃O₄ were obtained. The magnetic properties of the Fe₃O₄ loaded PMMA microspheres depended on the amount of Fe₃O₄ present in the resultant microspheres. The saturation magnetization and coercive force of the microspheres were 49-63 emu·g^-1 and 162-170 Oe, respectively. The rate of an increase in temperature by heat generated from an agar phantom dispersed with a microsphere sample was 1K·min^-1 under an alternating magnetic field (100 kH, 300 Oe). This material is expected to be utilized as a thermal seed for hyperthermic treatment of deep-seated cancers in our bodies using a gap-type alternating current field apparatus in combination with a prospective drug delivery system.