Iron Nanoparticles-Encapsulating Silica Microspheres for Arterial Embolization Hyperthermia

We attempted to prepare α-Fe-encapsulating silica (αFeSi) microspheres by a sol-gel process using tetramethoxysilane (TMOS) in water-in-oil emulsion. The effect of preparation conditions on the structure, magnetic and heating properties of resultant products were investigated. Oil phase consisted of kerosene with 32 wt% of surfactants (sorbitan monooleate / sorbitan monostearate in 3:1 weight ratio). Water phase consisted of TMOS, ethanol (CH2CH3OH), water and iron nitrate (Fe(NO3)3·9H2O) with TMOS / CH2CH3OH/H2O/Fe3+ in 1:7.4:16.2:0.4∼1.2 molar ratio. Fe3+-containing silica gel (FeSiG) microspheres 5 to 30 μm in size were successfully obtained by adding the water phase into the oil phase at 60 deg. C under stirring of 1500 rpm for 100 min. αFeSi microspheres was obtained by heating the FeSiG microspheres at 850deg. C in argon atmosphere. The obtained αFeSi microspheres have a saturation magnetization (Ms) up to 21 emu g-1 and a coercive force (Hc) of 133 Oe. The in vitro heating generation was evaluated under an alternating current (AC) magnetic field of 300 Oe and 100 kHz.