Magnetic Hyperthermia in the 400–1,100 kHz Frequency Range Using MIONs of Condensed Colloidal Nanocrystal Clusters

Dimitris Kouzoudis,Konstantinos Spiliotopoulos,Giorgio Zoppellaro,Georgios Samourgkanidis,Argiris Kolokithas-Ntoukas

doi:10.3389/fmats.2021.638019

Abstract

In the current study, we explored the magnetic hyperthermia performance of condensed–clustered magnetic iron oxide nanoparticles (MIONs) in the range of 400 kHz to 1.1 MHz at low field amplitudes. The strong interparticle interactions, present in such systems, can influence the hyperthermia power produced by MIONs. Herein, the heat dependence, as an increasing function of frequency, with a fixed magnetic field strength of 3 mT is recorded, revealing a direct relationship between the two physical quantities and a high heating efficiency for the condensed–clustered MIONs. In particular, the specific loss power (SLP) (or specific absorption rate [SAR]) parameter, which is the ratio of the heat power in watts produced per nanoparticle mass in grams, is linear to a good degree to the oscillating frequency with a step of roughly 30 W/g per 100 kHz increase. In addition, all the measurements were within the safety limits proposed by Hergt and Dutz criterion of H f ≤ 5 × 109A/ms for clinical application of magnetic fluid hyperthermia (MFH). Finally, the measured data of temperature vs. time at each frequency were interpreted in terms of simple thermodynamic arguments, thus extracting useful thermodynamic parameters for the heat power generated by the condensed–clustered MIONs.

Highlights

The application of nanotechnology in the field of medicine promises to revolutionize the treatment of malignant diseases such as cancer
The high-resolution transmission electron microscopy (TEM) images (HR-TEM) of MagAlg (Figures 2c,e) show the appearance of crystalline fringes in the condensed cluster nanoparticles (Figure 2c, the arrows indicate the spacing corresponding to the [311] plane, d = 2.52 Å)
We evaluated the hyperthermia efficiency of condensed–clustered magnetic iron oxide nanoparticles (MIONs) in a wide frequency range

Summary

Introduction

The application of nanotechnology in the field of medicine promises to revolutionize the treatment of malignant diseases such as cancer. Hybrid magnetic nanostructures (in particular, iron oxides) are among the most interesting classes of nano-theranostics and have been the topic of extensive research interest over the past decade (Yoo et al, 2011; Revia and Zhang, 2016; Lorkowski et al, 2021) Their excellent biocompatibility and inherent multifunctional nature of their magnetic core mark them suitable for a diverse set of biomedical applications, mainly including MRI (Zhou et al, 2014), physical tumor targeting through magnetic manipulation (Feng et al, 2017), and magnetic fluid hyperthermia (MHF) (Kozissnik et al, 2013; Deatsch and Evans, 2014; Das et al, 2019). Under the application of an external magnetic field, the magnetic moments of the nanoparticles align along the direction of the field and the saturation magnetization can be achieved at relatively low fields Another important physical parameter in work related to MNPs is the relaxation time τ which is an inherent characteristic time of the MNPs as a response to the alternating magnetic field (AMF), describing different rotational modes. The MNPs are suspended in aqueous solutions (ferrofluids) and this important property is determined experimentally by the simple formula (Sudame et al, 2020): cT

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