Heating ability modulation by clustering of magnetic particles for precision therapy and diagnosis

Abstract

Magnetic and thermal properties of clustered magnetite nanoparticles submitted to a high-frequency magnetic field is studied by means of rate equations. A simple model of large particle clusters (containing more than one hundred individual particles) is introduced. Dipolar interactions among clustered particles markedly modify shape and area of the hysteresis loops in a way critically dependent on particle size and cluster dimensions, thereby modulating the power released as heat to a host medium. For monodisperse and polydisperse systems, particle clustering can lead to either a significant enhancement or a definite reduction of the released power; in particular cases the same particles can produce opposite effects in dependence of the dimensions of the clusters. Modulation by clustering of the heating ability of magnetic nanoparticles has impact on applications requiring optimization and accurate control of temperature in the host medium, such as magnetic hyperthermia for precision therapy or fluid flow management, and advanced diagnostics involving magnetic tracers.

Improvement of Hyperthermia Properties of Iron Oxide Nanoparticles by Surface Coating

“…A simple model proved that the heating efficiency in samples containing clusters of NPs with a diameter lower than 15 nm decreases as the size of the aggregate increases (i.e., if the number of NPs in the aggregate increases). 74 In summary, the 50% increase in the SLP achieved with the citrate-based surface treatment after preparation is a very promising result, also in comparison with the data available in the literature for spherical Fe 3 O 4 NPs, summarized in Table 2. This table also reports the values of the intrinsic loss power (ILP), which is defined as the SLP normalized to H ̂a2 and f, assuming as a first approximation a linear dependence of SLP on (H ̂a2 •f).…”

“…The variations in the SLP values between the citrate-coated NPs and the other two samples can be attributable to the different sizes of the NP aggregates (95 nm against 130 and 150 nm for the uncoated and CMC-coated NPs, respectively). A simple model proved that the heating efficiency in samples containing clusters of NPs with a diameter lower than 15 nm decreases as the size of the aggregate increases (i.e., if the number of NPs in the aggregate increases) …”

“…A simple model proved that the heating efficiency in samples containing clusters of NPs with a diameter lower than 15 nm decreases as the size of the aggregate increases (i.e., if the number of NPs in the aggregate increases). 74 …”

Magnetic Nanoparticle Imaging: Insight on the Effects of Magnetic Interactions and Hysteresis of Tracers

“…This applies, for instance, to MPI-guided magnetic hyperthermia, where nanoparticles have to accumulate in correspondence of the target tissue in order to produce the desired heating effect. ,, Even in applications where the concentration of nanoparticles capable of providing therapeutic effects is low on the average, locally high concentrations can be found in tissues and/or organs by effect of a slow process of nanoparticle clearance and excretion, possibly resulting in dangerous side effects. − It should be noted that dipole–dipole interaction among particles exists even when the particles are well separated from each other, as recently checked in a suspension of commercial iron-oxide nanoparticles . Dipolar interaction can be simply modeled and is shown to be proportional to particle concentration; ,, at high frequencies, the interaction becomes non-negligible when the mean interparticle distance is less than three to four times the nanoparticle diameter. , …”

“…48−50 It should be noted that dipole−dipole interaction among particles exists even when the particles are well separated from each other, 51 as recently checked in a suspension of commercial iron-oxide nanoparticles. 52 Dipolar interaction can be simply modeled and is shown to be proportional to particle concentration; 31,53,54 at high frequencies, the interaction becomes non-negligible when the mean interparticle distance is less than three to four times the nanoparticle diameter. 31,54 This paper is aimed to closely inspect the factors affecting the magnetic response of realistic assemblies of magnetite nanotracers submitted to a sinusoidal driving field of magnitude and frequency appropriate to typical MPI operations.…”