Abstract
Manganese and zinc ferrite magnetic nanoparticles (MNPs) were successfully synthesized using the polyol method in ethylene glycol and were found to have high saturation magnetization values (90–95 emu/g at 4 K) when formed by ~30-nm crystallites assembled in an ~80-nm multicore structure. Hyperthermia data revealed a sigmoidal dependence of the specific absorption rate (SAR) on the alternating magnetic field (AMF) amplitude, with remarkable saturation SAR values in water of ~1200 W/gFe+Mn and ~800 W/gFe+Zn for the Mn and Zn ferrites, respectively. The immobilization of the MNPs in a solid matrix reduced the maximum SAR values by ~300 W/gFe+Mn, Zn for both ferrites. The alignment of the MNPs in a uniform static magnetic field, before their immobilization in a solid matrix, significantly increased their heating performance. Toxicity assays performed in four cell lines revealed a lower toxicity for the Mn ferrites, while in the case of the Zn ferrites, only ~50% of cells were viable upon their incubation for 24 h with 0.2 mg/mL of MNPs. Cellular uptake experiments revealed that both MNPs entered the cells in a time-dependent manner, as they were found initially in endosomes and later in the cytosol. All of the studied cell lines were more sensitive to the ZnFe2O4 MNPs.
Highlights
The last decades have shown an exponentially increased interest in the applications of magnetic nanoparticles (MNPs) in various fields [1]
The transmission electron microscopy (TEM) and X-ray diffraction (XRD) data suggested a multicore polycrystalline structure approximately 80 nm in diameter composed of several individual crystallites of ~30 nm
Both the Mn and Zn ferrite MNPs synthesized in ethylene glycol (EG) displayed a high Ms of 90 emu/g and 95 emu/g for Mn and Zn, respectively, values which were significantly higher than the Ms of Fe3O4 MNPs synthesized in EG (75 emu/g) in the same conditions
Summary
The last decades have shown an exponentially increased interest in the applications of magnetic nanoparticles (MNPs) in various fields [1]. Biomedical applications of magnetic nanoparticles include targeted drug delivery, magnetic hyperthermia (MH), contrast agents for magnetic resonance imaging (MRI), biological separation, neural stimulation, biosensing, and gene transcription [2]. Iron oxide MNPs have had limited value in magnetic moments (saturation magnetization) and relaxivity, resulting in limited heating capabilities and lower sensitivity in MRI diagnostics [5,6]. To overcome these limitations, new types of MNPs have been actively pursued, aimed at achieving improved magnetic properties such as magnetic anisotropy and saturation magnetization (Ms), which are of paramount importance for increasing effectiveness, especially in MH applications [7]
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