Magnetic and bioactivity evaluation of ferrimagnetic ZnFe2O4 containing glass ceramics for the hyperthermia treatment of cancer

Glass ceramics of the composition xZnO·25Fe2O3·(40−x)SiO2·25CaO·7P2O5·3Na2O were prepared by the melt-quench method using oxy-acetylene flame. Glass-powder compacts were sintered at 1100 °C for 3 h and then rapidly cooled at −10 °C. X-ray diffraction (XRD) revealed 3 prominent crystalline phases: ZnFe2O4, CaSiO3 and Ca10(PO4)6(OH)2. Vibrating sample magnetometer (VSM) data at 10 KOe and 500 Oe showed that saturation magnetization, coercivity and hence hysteresis area increased with the increase in ZnO content. Nano-sized ZnFe2O4 crystallites were of pseudo-single domain structure and thus coercivity increased with the increase in crystallite size. ZnFe2O4 exhibited ferrimagnetism due to the random distribution of Zn2+ and Fe3+ cations at tetrahedral A sites and octahedral B sites. This inversion/random distribution of cations was probably due to the surface effects of nano-ZnFe2O4 and rapid cooling of the material from 1100 °C (thus preserving the high temperature state of the random distribution of cations). Calorimetric measurements were carried out using magnetic induction furnace at 500 Oe magnetic field and 400 KHz frequency. The data showed that maximum specific power loss and temperature increase after 2 min were 26 W/g and 37 °C, respectively for the sample containing 10% ZnO. The samples were immersed in simulated body fluid (SBF) for 3 weeks. Scanning electron microscope (SEM), energy dispersive spectroscopy (EDX) and XRD results confirmed the growth of precipitated hydroxyapatite phase after immersion in SBF, suggesting that the ferrimagnetic glass ceramics were bioactive and could bond to the living tissues in physiological environment.