Magnetic core–shell structures for magnetic fluid hyperthermia therapy application

Abstract

Nanocrystals of magnetite (Fe₃O₄) were prepared by alkaline precipitation. The precursor used for synthesis was ferrous chloride alone and the reaction was carried out in the absence of any oxidant. The synthesized pure phase magnetic nanoparticles (MNPs) were coated with a biocompatible polymer, acrypol (AP). Fourier transform infrared and thermogravimetric studies confirmed coating of AP on MNPs. Bare and coated MNPs (Fe₃O₄ and AP–Fe₃O₄) showed particle sizes of 21.8 ± 5.3 and 14.2 ± 5.0 nm respectively. The magnetization values of the MNPs were 37.77 and 32.71 emu g⁻¹ at room temperature respectively. Negligible coercivity and remanence values at room temperature implied superparamagnetic behavior of the MNPs. The induction heating abilities of MNPs at 167.6, 251.4 and 335.2 Oe (equivalent to 13.3, 20.0 and 26.7 kA m⁻¹ respectively) were studied, in order to use them in magnetic fluid hyperthermia therapy. At 335.2 Oe, AP coated NPs showed a maximum specific absorption rate (SAR) of 95.8 W g⁻¹, while bare NPs showed a SAR of 74.4 W g⁻¹. Zeta potential values of bare and coated MNPs were measured at a pH range from 2 to 10 in water. Both the colloidal suspensions were found to be very stable at extreme pH values. However, higher zeta potential values of coated MNPs were assigned to their higher colloidal stability. Low cytotoxic effects of both the MNPs on the L929 cell line proved their suitability for in vivo applications.