Influence of a transverse static magnetic field on the magnetic hyperthermia properties and high-frequency hysteresis loops of ferromagnetic FeCo nanoparticles

Abstract

Abstract:The influence of a transverse static magnetic field on the magnetic hyperthermia properties is studied on a system of large-losses ferromagnetic FeCo nanoparticles. The simultaneous measurement of the high-frequency hysteresis loops and of the temperature rise provides an interesting insight into the losses and heating mechanisms. A static magnetic field of only 40 mT is enough to cancel the heating properties of the nanoparticles, a result reproduced using numerical simulations of hysteresis loops. These results cast doubt on the possibility to perform someday magnetic hyperthermia inside a magnetic resonance imaging setup. Main Text:Magnetic hyperthermia (MH) is a promising cancer treatment technique based on the fact that magnetic nanoparticles (MNPs) placed in an alternating magnetic field release locally heat [1,2,3]. Its efficiency in combination with radiotherapy has been recently demonstrated in the treatment of glioblastome multiforme [4].On the long term, performing magnetic hyperthermia in a magnetic resonance imaging (MRI) setup could have several advantages: i) The production of the magnetic field for MH could be produced by the same hardware as for the MRI. ii) The measurement of the local temperature during hyperthermia treatment using MRI thermometry could allow for a better control of the treatment, by avoiding overheating effect in the safe zones. iii) MRI can quantify of the local concentration of nanoparticles trapped inside the tumor, which is essential to define the treatment parameters.However, the presence of a static magnetic field in MRI set-ups should decrease the specific absorption rate (SAR) of the MNPs, as pointed out by a few theoretical works [5,6,7,8]. This explains why the development of a combined system should probably be based on a lowfield MRI setup working a static field of 0.1 or 0.2 T only [5]. So far, no experimental study of the influence of a static magnetic field on the MH properties of MNPs has been reported. In the present article, we report such an investigation for a model system of ferromagnetic FeCo nanoparticles. In a first study, we demonstrated that these NPs display large losses and a behavior typical of the Stoner-Wohlfarth regime [9]. To go deeply into the mechanisms involved, the influence of the static magnetic field on MH properties is studied by combining temperature measurements and high-frequency hysteresis loop measurements. Our results, which are consistent with numerical calculations of the hysteresis loops, show that a small magnetic field is sufficient to cancel the heating properties of the MNPs.

Increase of magnetic hyperthermia efficiency due to dipolar interactions in low-anisotropy magnetic nanoparticles: Theoretical and experimental results

“…SAR measurements were p erformed on a home-mad e electromagn et sp ecially designed for hyp erthermia exp eriments [17]. High-frequency hysteresis loop s were performed using a setup described elsewhere [18]. Hysteresis loop s measured on this setup have p reviously shown to be consistent with SAR measurements [18].…”

Large scale production of biocompatible magnetite nanocrystals with high saturation magnetization values through green aqueous synthesis

“…indicating that these MNCs are closer to the superparamagnetic regime than the ferromagnetic one 31 and display a low anisotropy, a very good point for their hyperthermia properties, even in the presence of magnetic interactions. 46 Further works are in progress to optimize the heating efficiency under appropriate field conditions that will require higher magnetic fields.…”

Field dependent transition to the non-linear regime in magnetic hyperthermia experiments: Comparison between maghemite, copper, zinc, nickel and cobalt ferrite nanoparticles of similar sizes

“…It was proved that: (i) SAR measurements are intimately related to the dynamic hysteresis area, as expected from theory (although some references in the literature seem, wrongly, to believe that "superparamagnetic" nanoparticles can heat); and that (ii) dynamic hysteresis simulations can reproduce, fairly well, real frequency dependent magnetic measurements. 46 Therefore, as our main objective was to make a qualitative comparison between our experimental results and dynamic hysteresis simulations, in order to give support to the important role of magnetic anisotropy and damping factor into the magneto thermal properties of the nanoparticles. From our point of view, the approach used here might be highly useful to the development of more efficient magnetic nanoparticles for biomedical applications, since it is able to represent several real magnetic hyperthermia features from the magnetic nanoparticles.…”