Research on annihilation of cancer cells by glass-ceramics for cancer treatment with external magnetic field. I. Preparation and cytotoxicity.

Ferrimagnetic glass-ceramics were prepared as a heating mediator for hyperthermia in cancer treatment. We prepared glasses in the system 40Fe2O3-30CaO-30SiO2 and precipitated ferrimagnetic crystallites through controlled two-step heat treatment. To improve the heating capability of ferrimagnetic crystallites, i.e., magnetite, generation of other crystalline phases should be prohibited. The addition of each 1% of P2O5 and B2O3 led to lowering the crystallization temperature of magnetite, which was useful to suppress the other crystalline formation. The maximum nucleating and crystal growth rates were 20.47 x 10(6)/mm2 x s at 690 degrees C and 8.125 nm/min(0.5) at 940 degrees C, respectively. After nucleation at 690 degrees C for 60 min prior to crystal growth at 940 degrees C for 2 h, samples exhibited the following properties: crystallite size of 90.5 nm, the maximum volumetric fraction of 31.1%, and saturation magnetization of 100 emu/cm2. The coercive forces were ranged between 382.0 and 388.2 Oe in all heat-treatment conditions. As a result of a preclinical evaluation of biocompatibility by agar diffusion test with L929 cells, both as-quenched and heat-treated glasses could be biocompatible.