Modelling the effect of different core sizes and magnetic interactions inside magnetic nanoparticles on hyperthermia performance

Abstract

We present experimental intrinsic loss power (ILP) values, measured at an excitation frequency of 1 MHz and at relatively low field amplitudes of 3.4 to 9.9 kA/m, as a function of the mean core diameter, for selected magnetic nanoparticle (MNP) samples synthesized in the recent EU-funded NanoMag project. The mean core sizes ranged from ca. 8 nm to 31 nm. Transmission electron microscopy indicated that those with smaller core sizes (less than ca. 22 nm) were single-core MNPs, while those with larger core sizes (ca. 29 nm to 31 nm) were multi-core MNPs. The ILP data showed a peak at ca. 20 nm. We show here that this behaviour correlates well with the predicted ILP values obtained using either a non-interacting Debye model, or via dynamic Monte-Carlo simulations, the latter including core-core magnetic interactions for the multi-core particles. We show that this alignment of the models is a consequence of the low field amplitudes used.

Iron Oxide Mediated Photothermal Therapy in the Second Biological Window: A Comparative Study between Magnetite/Maghemite Nanospheres and Nanoflowers

“…Consequently, MNPs have made their way into different applications in the biomedical field including, among others, MRI contrast agents [2], drug delivery [3], tissue engineering [4,5], magnetic targeting [6][7][8][9], and as heat mediators in magnetic hyperthermia (MHT) cancer therapy [10,11]. Unlike other thermal nanotherapies, MHT can be used non-invasively at any depth in tissues, but it still suffers from major restrictions mainly due to the low yield of heat generated per mg. Consequently, several approaches have been suggested to overcome these limitations: among them, one is based on the synthesis of novel nanostructures having an optimized heating [12][13][14]; another consists of the association of MNPs with other heat-generating materials, such as plasmonic ones, specifically designed for photothermal (PT) therapy, resulting in a multifunctional magneto-plasmonic nanohybrid platform. Such plasmonic materials include metals, such as gold (Au), providing the hybrids with an absorption in the first near-infrared (NIR-I) optical window in biological tissues or semiconductors, such as copper sulfide (CuS), which possesses a strong absorption in the second (NIR-II) window [15][16][17][18].…”

Dynamics of interacting magnetic nanoparticles: effective behavior from competition between Brownian and Néel relaxation

“…17,18 In the physically relevant regime where Néel relaxation is a rare, thermally activated process, the LLG approach is computationally very inefficient. Therefore, kinetic Monte-Carlo schemes have been used 19,20 to simulate the magnetization response of frozen multi-core magnetic particles to oscillating fields. For ferrofluids, a Monte-Carlo scheme to equilibrate the magnetic moments alongside their translational diffusion was proposed.…”

Static magnetization of immobilized, weakly interacting, superparamagnetic nanoparticles

“…Note that R 2 (α, 0) = L(α)sinh(α)/α. Substituting these expressions into eqn (21) and (19), gives for the magnetization…”

“…Note that this function is dependent on ξ 1 in both the exponent of the numerator, and the normalization coefficient R 5 in the denominator. So, to calculate the z component of the effective dipole field (21), one has to average the ratio R 6 /R 5 over the angle ξ 1 , and the magnetization becomes…”

“…So-called magnetic soft matter includes ferrofluids, 1 magnetorheological fluids, magnetic elastomers [2][3][4][5] and ferrogels, [6][7][8] ferronematic liquid crystals, [9][10][11] and various biocompatible magnetic suspensions, [12][13][14][15][16] which are applied in targeted drug delivery and magnetic hyperthermia. [17][18][19][20][21][22] In addition to technical and biomedical applications, magnetic nanoparticle ensembles are also useful in colloid technology, because of interesting self-assembly processes. 23 The fundamental magnetic properties of single superparamagnetic and ferromagnetic nanoparticles have been studied in detail, including the composition and architecture of the particles, and the effects on the static and dynamic responses to applied magnetic fields.…”