Enhancement in hyperthermia efficiency under in situ orientation of superparamagnetic iron oxide nanoparticles in dispersions

Abstract

To minimize the exposure time in magnetic fluid hyperthermia based cancer therapy, it is important to improve the heating efficiency. We demonstrate a 62% enhancement in heating efficiency through in situ orientation of magnetic nanoparticles (MNP) along the direction of the radio frequency alternating magnetic field using a static external magnetic field of 80 G in phosphate coated superparamagnetic Fe3O4 MNP dispersions. The heating efficiency increase in oriented samples is due to the enhanced effective anisotropy energy density along the linear chainlike structures of the MNPs, as confirmed from atomic force microscopy and the larger dynamic hysteresis loop area.

Heating ability of elongated magnetic nanoparticles

“…It follows from the results obtained in the previous section that the use of assemblies of magnetite nanoparticles with large aspect ratios in magnetic hyperthermia, generally speaking, is unfavorable, since an increase in the particle aspect ratio leads not only to a decrease in the SAR of the assembly, but also to a corresponding decrease in the width of the window of optimal particle diameters. However, it was shown experimentally [37,38] that the SAR of an assembly can be significantly increased if the assembly is oriented in a strong magnetic field and ac magnetic field is applied along the assembly orientation axis. Recent study shows [17] that, under certain conditions, the orientation of the assembly is possible both in vitro and in vivo.…”

“…It is well known that elongated magnetic nanoparticles can be easily oriented in applied external magnetic field. Furthermore, the oriented assembly of nanoparticles showed increased SAR [37,38] when ac magnetic field is applied parallel to the orientation axis. It is worth mentioning that in nature, some strains of magnetotactic bacteria can synthesize elongated magnetic nanoparticles [39][40][41].…”

Influence of size polydispersity on magnetic field tunable structures in magnetic nanofluids containing superparamagnetic nanoparticles

“…The self-assembly of magnetic nanoparticles under an external magnetic field gives rise to interesting optical properties that are exploited in applications such as light controllable magnetic fluid based devices [18,19], optical limiters [20], biomedicine [21] etc. Besides that, such magnetic nanofluids are also used in field-induced heating [22], hyperthermia therapies [23], magnetic resonance imaging [24], thermal transport [25][26][27][28] and as a model system to probe interaction forces at nanoscale. [29] The behavior of magnetic fluids under various experimental conditions depends on the equilibrium and nonequilibrium field-induced structures formed in a magnetic field.…”

Improvement of Magnetic Particle Hyperthermia: Healthy Tissues Sparing by Reduction in Eddy Currents

“…Until now, much of the literature regarding increasing the efficacy of MNP hyperthermia therapy has focused on increasing MNPs’ specific absorption rate (SAR) [ 20 , 21 , 22 ] or increasing the concentration of MNPs in the tumor [ 23 , 24 , 25 ]. There are only a few studies focused on decreasing the maximum temperature resulting from ECH in order to increase therapeutic ratio.…”