Abstract
The ability of magnetic nanoparticles (MNPs) to transform electromagnetic energy into heat is widely exploited in well-known thermal cancer therapies, such as magnetic hyperthermia, which proves useful in enhancing the radio- and chemo-sensitivity of human tumor cells. Since the heat release is ruled by the complex magnetic behavior of MNPs, a careful investigation is needed to understand the role of their intrinsic (composition, size and shape) and collective (aggregation state) properties. Here, the influence of geometrical parameters and aggregation on the specific loss power (SLP) is analyzed through in-depth structural, morphological, magnetic and thermometric characterizations supported by micromagnetic and heat transfer simulations. To this aim, different samples of cubic Fe3O4 NPs with an average size between 15 nm and 160 nm are prepared via hydrothermal route. For the analyzed samples, the magnetic behavior and heating properties result to be basically determined by the magnetic single- or multi-domain configuration and by the competition between magnetocrystalline and shape anisotropies. This is clarified by micromagnetic simulations, which enable us to also elucidate the role of magnetostatic interactions associated with locally strong aggregation.
Highlights
In the last decade, the interest towards the application of magnetic nanoparticles (MNPs) in biomedicine has increased exponentially, being employed in diagnostics, as contrast agents in magnetic resonance imaging (MRI) or tracers in magnetic particle imaging (MPI), as well as in therapeutics, as heat mediators in heat-assisted drug release and magnetic hyperthermia [1–3]
Here we present a detailed characterization of Fe3 O4 NPs with cubic shape, produced via hydrothermal route by varying synthesis parameters
The size distribution reveals a large fraction of MNPs around the critical dimension for the transition from superparamagnetism to single-domain blocked state, while for the largest sample, the size range is typical of multi-domain configuration
Summary
The interest towards the application of magnetic nanoparticles (MNPs) in biomedicine has increased exponentially, being employed in diagnostics, as contrast agents in magnetic resonance imaging (MRI) or tracers in magnetic particle imaging (MPI), as well as in therapeutics, as heat mediators in heat-assisted drug release and magnetic hyperthermia [1–3]. Magnetic hyperthermia exploits the capability of MNPs to generate heat when exposed to an alternating current (AC) magnetic field with frequency in the range 50 kHz–1 MHz. As an example, Fe3 O4 (magnetite) NPs have been successfully tested in many clinical trials, using magnetic fields with frequency of 100 kHz and amplitude variable between 2.5 kA/m and 18 kA/m [4–6]. The hyperthermia efficacy of MNPs is usually measured by means of the specific loss power (SLP), known as specific absorption rate (SAR), which expresses the power dissipated per unit mass of magnetic material [7,8].
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