Optimal Parameters for Hyperthermia Treatment Using Biomineralized Magnetite Nanoparticles: Theoretical and Experimental Approach

Abstract

We hereby present experimental and theoretical insights on the use of biomineralized magnetite nanoparticles, called magnetosomes, as heat nanoinductors in the magnetic hyperthermia technique. The heating efficiency or specific absorption rate of magnetosomes extracted from Magnetospirillum gryphiswaldense bacteria and immersed in water and agarose gel, was directly determined from the hysteresis loops obtained at different frequencies and magnetic field amplitudes. We demonstrate that heat production of magnetosomes can be predicted in the framework of the Stoner–Wohlfarth theory of uniaxial magnetic anisotropy subjected to significant dipolar interactions, which can be described in terms of an interaction anisotropy superimposed to that of each particle. Based on these findings, we propose optimal magnetic field amplitude and frequency values in order to maximize the heat production while keeping the undesired eddy current effects below safe and tolerable limits. The efficiency of magnetosomes as heat generators and their impact on cell viability has been checked in macrophage cells. Our results clearly indicate that the hyperthermia treatment causes both cell death and inhibition of cell proliferation. Specifically, only 36% of the treated macrophages remained alive 2 h after alternating magnetic field exposure, and 24 h later the percentage fell to 22%.

Unlocking the Potential of Magnetotactic Bacteria as Magnetic Hyperthermia Agents

“…We can obtain relevant information based on the experimental data. First of all, we see how the SAR values for both magnetotactic bacteria and magnetosomes increase linearly with the magnetic field frequency, since the normalized magnetic losses, SAR/ f , are almost independent of the applied frequency, as we had already observed in our previous work on isolated magnetosomes . Second, the SAR values for the magnetosomes dispersed in water are clearly lower than those obtained for magnetotactic bacteria.…”

“…SAR normalized by the frequency, SAR/ f , measurements at different frequencies, 149, 301, and 528 kHz, for bacteria and magnetosomes dispersed in water. Magnetosomes curve data has been taken from our previous work . In the inset, AC hysteresis loops are presented corresponding to the bacteria (continuous line) and magnetosomes (dashed line) as obtained from AC magnetometry measurements (300 kHz).…”

“…The evolution of the number of living cells over time shows the same pattern in both cell cultures with and without internalized bacteria, and no significant differences were found in the number of living cells after 48 h of the bacteria uptake. Different results were reported in previous experiments for the isolated magnetosomes from Magnetospirillum , which can show cytotoxicity affecting both viability and cell proliferation.…”

“…[13,33,34] The superior magnetic properties of magnetosomes in magnetic hyperthermia have already been reported. [35,36] However, the number of works on magnetic hyperthermia performance of the "whole" magnetotactic bacteria is very limited. Song et al [37] found that magnetotactic bacteria under an external alternating magnetic field (AMF) can be used to kill Staphylococcus aureus, a common hospital and household pathogen.…”

“…Magnetic hyperthermia is a process in which controlled heating of magnetic nanoparticles located in the tumor can kill or deactivate cancer cells . The superior magnetic properties of magnetosomes in magnetic hyperthermia have already been reported . However, the number of works on magnetic hyperthermia performance of the “whole” magnetotactic bacteria is very limited.…”