Sol–gel synthesis of magnetic TiO2 microspheres and characterization of their in vitro heating ability for hyperthermia treatment of cancer

Abstract

Common cancer treatments are invasive and lack specificity, leading to unwanted side effects. Because hyperthermia can kill cancer cells and damage proteins and structures within cells, it has been considered a novel, minimally invasive cancer treatment. However, many hyperthermia treatments cannot heat deep-seated tumors effectively and locally. Heat-generating magnetic microspheres can help address this challenge. However, current research has not produced microspheres that can be sufficiently heated. We prepared magnetic titania (TiO2) microspheres by introducing magnetite nanoparticles (MNPs) into the sol–gel process during water-in-oil emulsion for in situ hyperthermia treatment of cancers. Two types of MNPs were used in this study: One type was synthesized by a chemical coprecipitation method, and the other type was commercially available MNPs. The obtained microspheres contained up to 46.7 wt% MNPs, and their saturation magnetization and coercive force were 34.2 emu/g and 103 Oe, respectively. The particles’ in vitro heating efficiency in an agar phantom was measured in an alternating magnetic field of 300 Oe and 100 kHz. The temperature increase in the agar phantom within 300 s was 4.5 °C for microspheres with MNPs that were synthesized by chemical coprecipitation and 53 °C for microspheres with commercially available MNPs. The excellent heating efficiency of the microspheres may be attributed to the hysteresis losses of the magnetic particles. These microspheres are believed to be promising thermoseeds for hyperthermic treatment of cancer. Magnetic TiO2 microspheres with a diameter of 7–15 μm were obtained by directly introducing preformed magnetic MNPs into a sol–gel process from TTIP in water-in-oil emulsion. The magnetic TiO2 microspheres containing Fe3O4 at a content higher than 46 wt% increased the temperature of the agar phantom to above 43 °C in 3 min. They are expected to be useful for arterial embolization hyperthermic treatment of cancer, but control of their diameter is essential.