Enhanced magnetic hyperthermia efficiency in poly vinyl alcohol-coated zinc-substituted cobalt ferrite nanoparticles: Correlated effects of zinc content and applied magnetic field strength

Abstract

Finding the interrelation among the magnetic response of the heat mediators to an alternating magnetic field (AMF) and other relevant parameters in magnetic hyperthermia therapy (MHT) can give the possibility to accurately design high-performance nanostructured magnetic nanoparticles (MNPs). In this context, the present work investigates the effect of the zinc substitution on magnetic properties and heat-generating ability of poly vinyl alcohol-coated Zn-substituted cobalt ferrite nanoparticles (PZC NPs) with different zinc contents (ZnxCo1−xFe2O4; x = 0, 0.15, 0.3, 0.4, 0.5, 0.7), synthesized using hydrothermal-assisted co-precipitation method. The obtained results showed that the PZC NPs with an average particle size ∼ 15 nm exhibit ferrimagnetic features and their coercivity (Hc) values decrease as the zinc content (x) increases. Moreover, as Zn2+ replaces Co2+ in the structure, saturation magnetization (Ms) increases up to about 52 emu/g for PZC-30 NPs (x =0.3) and then decreases for higher Zn contents. The hyperthermia measurements were performed at a fixed filed frequency (f=120kHz) and different magnetic field strengths (Happl=17,20,24.5kA/m). The results revealed that, as x increases, specific absorption rate (SAR) at each Happl first shows an increasing trend and then reaching a maximum value (at x=0.4) follows a decreasing trend. Moreover, the highest SAR (25.25 W/g) belongs to the magnetic fluid containing PZC-40 NPs at Happl=24.5kA/m. Furthermore, the Happl-dependency of the SAR values were obtained as a power law (SAR∼Happln) in which the exponent n rises as x decreases, suggesting that the optimal composition tends to shift to ones with the lower x at higher Happl. The obtained results, revealing the high impact of the interrelation between the chemical composition and the Happl on the MNPs heating efficiency, can shed more light on the way to design heat mediators with optimal performance through simultaneous control of the chemical composition and the Happl.