Saqlain Abbas Shah
Department of Physics Forman Christian College Lahore Lahore Pakistan

Abstract:

Ferrimagnetic bioactive glass ceramics are expected to be potential candidates for the hyperthermia treatment of cancer. When placed under an alternating magnetic field of high frequency, these materials generate heat energy by hysteresis losses. Tumor cells usually perish around 43 °C due to the poorly developed nervous and circulatory system whereas healthy body cells remain unaffected at this temperature. Such materials should have the adequate ability to bond with the tissues (bioactivity). Much work has been done on Fe3O4 containing glass ceramics for this purpose but present work is the first ever detailed study of its kind on ZnFe2O4 containing ferrimagnetic bioactive 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. Glass-powder compacts were sintered at 1100 ºC for 3h and then rapidly cooled at -10 ºC. Vibrating sample magnetometer (VSM) data at 10 kOe showed that saturation magnetization, coercivity and hence hysteresis area increased with the increase in ZnO content. 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 ºC (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 ºC, respectively for the sample containing 10% ZnO.  The glass ceramic samples were now heated to 600 °C and cooled in an aligning magnetic field of 1 Tesla to cause anisotropy. Magnetically aligned samples were compared with the non-aligned samples. VSM measurements at 10 kOe showed that the magnetic properties were enhanced by the aligning magnetic field and it led to enhance the magnetic heat generation under magnetic induction furnace operating at 500 Oe and 400 kHz for 2 min. Data showed that maximum specific power loss and temperature increase after 2 min were 31.5 W/g and 45 °C respectively for the aligned sample containing 10% ZnO. The samples were immersed in simulated body fluid (SBF) for 3 weeks. Scanning electron microscope (SEM), energy dispersive spectroscopy (EDX), Fourier transform infrared spectroscopy (FTIR) 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. Thus, following are the prime novel features of this research work:

1. Generally, Fe3O4 (magnetite) has been used in this research arena of biomaterials. Present work is the first ever detailed study of its kind on ferrimagnetic ZnFe2O4 containing bioactive glass ceramics.
2. ZnFe2O4 is a paramagnetic substance at room temperature. In this work it is made ferrimagnetic by special treatment of quenching the substance after sintering.
3. The magnetic and heat generating properties of the ferrimagnetic zinc-ferrite containing bioactive glass ceramics have been enhanced by cooling the substance in aligning magnetic field, without any compositional or micro-structural changes in the material.
4. The glass ceramics presented in this work possess not only sufficient magnetic and calorimetric properties but also adequate bioactivity, making it a potential candidate for the hyperthermia treatment of cancer.

Keywords: Hyperthermia, Magnetic heating, Bioactive, Hydroxyapatite