Disentangling local heat contributions in interacting magnetic nanoparticles

Abstract

Recent experiments on magnetic nanoparticle hyperthermia show that the heat dissipated by particles must be considered locally, instead of characterizing it as a global quantity. Here we show theoretically that the complex energy transfer between nanoparticles interacting via magnetic dipolar fields can lead to negative local hysteresis loops and does not allow the use of these local hysteresis loops as a temperature measure. Our model shows that interacting nanoparticles release heat not only when the nanoparticle magnetization switches between different energy wells, but also in the intrawell motion, when the effective magnetic field is changed because the magnetization of another particle has switched. The temperature dynamics has a highly nontrivial dependence on the amount of precession, which is controlled by the magnetic damping. Our results constitute a step forward in modelling of magnetic nanoparticles for hyperthermia and other heating applications.

How size, shape and assembly of magnetic nanoparticles give rise to different hyperthermia scenarios

“…Another key aspect defining the heating performance is the particle assembling, as it is often observed that particles tend to aggregate after cell internalisation, 41 which may completely define their heat release in comparison with the randomly dispersed case. [42][43][44][45] The assembling process is defined by a complex interplay between a broad range of parameters, including the media properties (viscosity, pH), the nanoparticle characteristics (size, shape, anisotropy), the field parameters (frequency and amplitude) and, obviously, the sample concentration see e.g. Bakuzis et al and references therein.…”

Simulating the Self-Assembly and Hysteresis Loops of Ferromagnetic Nanoparticles with Sticking of Ligands

“…This has implications on magnetic hyperthermia. The area enclosed by global hysteresis loops-but not local ones [45]-is correlated with the amount of heat that can be generated. One sees that this heat can be increased or decreased by large amounts when ligand friction/stickiness is increased, depending on whether particle agglomerates have sufficient time to follow the oscillating applied field.…”

Effect of ring-shaped clusters on magnetic hyperthermia: modelling approach

“…The practical applications of MH therapy require accurate predictions of intensity of the heat generation and temperature of the heated region. There are many factors which influence the heating efficiency, including frequency and amplitude of the field, shape, size, concentration and magnetic properties of the particles (see [8][9][10]).…”