Experimental determination of the frequency and field dependence of Specific Loss Power in Magnetic Fluid Hyperthermia

Abstract

Magnetic nanoparticles are promising systems for biomedical applications and in particular for Magnetic Fluid Hyperthermia, a promising therapy that utilizes the heat released by such systems to damage tumor cells. We present an experimental study of the physical properties that influences the capability of heat release, i.e. the Specific Loss Power, SLP, of three biocompatible ferrofluid samples having a magnetic core of maghemite with different core diameter d = 10.2, 14.6 and 19.7 nm. The SLP was measured as a function of frequency f and intensity of the applied alternating magnetic field H, and it turned out to depend on the core diameter, as expected. The results allowed us to highlight experimentally that the physical mechanism responsible for the heating is size-dependent and to establish, at applied constant frequency, the phenomenological functional relationship SLP=c·H x , with 2≤x<3 for all samples. The x-value depends on sample size and field frequency/ intensity, here chosen in the typical range of operating magnetic hyperthermia devices. For the smallest sample, the effective relaxation time τ eff  19.5 ns obtained from SLP data is in agreement with the value estimated from magnetization data, thus confirming the validity of the Linear Response Theory model for this system at properly chosen field intensity and frequency. I. INTRODUCTIONMagnetic nanoparticles are promising tools in biomedical applications against cancer, and suitable systems for diagnostics by e.g. Magnetic Resonance Imaging and innovative therapies, like drug delivery and Magnetic Fluid Hyperthermia (MFH) [1][2][3][4][5][6][7][8][9][10][11]. The MFH is a recently developed anti-cancer locally acting technique which aims to reduce the side effects of the traditional techniques as chemo-or radio-therapies [12]. This technique makes use of the capability of magnetic nanoparticles (MNPs) to release heat when exposed to an alternating magnetic field (AMF), as a therapeutic treatment to selectively destroy tumor cells within the human body. In MFH treatments, the AMF application is strictly limited to a safety range of frequency f and intensity H due to medical and technical restrictions, as established by the Brezovich criterion which requires H·f < 4.85·10 8 Am -1 s -1 [13]. The amount of magnetic field energy converted into heat (and subsequently absorbed by tissues) is given by the energy losses occurring during the MNP magnetization reversal, according to the dynamic regime determined by the MNPs physico-chemical properties (size, shape,

Application and comparison of thermistors and fiber optic temperature sensor reference for ILP measurement of magnetic fluids in double cell magnetic hyperthermia

“…In the definition of the ILP it is assumed that the linear response theory can be applied [7] , [18] in the appropriate particle size range. As a consequence, the SLP of fluids containing small ( ) MNPs should be proportional with the frequency and would have a quadratic dependence on the amplitude of the magnetic field, as it was shown by Cobianchi and his coworkers [19] . Commonly the SLP is measured at larger field strengths up to .…”

“…On the other hand, outside the superparamagnetic domain, such as in case of ferromagnetic particles, the field strength dependence deviates from the quadratic relation, as . In this region instead of the LRT the Stoner-Wohlfarth model can be used to evaluate the field strength dependence of the SLP [19] .

Figure 9 Curves of the frequency (a) and magnetic field (b) dependence of the SLP .

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

“…The influence of the particles shape on the MH effect has been studied, for example, in [11,12]. Experimental investigations of MH in liposomes, cell membranes and in the intracellular space, containing ferromagnetic nanoparticles united in various clusters and aggregates, can be found, for example, in [13][14][15][16]. Experiments [17] demonstrate that closed ring-like aggregates very often appear in ferrofluids with strongly magnetically interacting particles.…”

Effect of different molecular coatings on the heating properties of maghemite nanoparticles

“…34 In addition, the modification of the nanoparticles' surface is fundamental to ensure good colloidal stability and modulate the interparticle distance through the formation of the clusters. Therefore, several stabilizers have been proposed in the literature, among them: hydrophilic molecules bonded to the NPs' surface, such as dimercaptosuccinic acid (DMSA), [35][36][37][38][39] functionalized silanes, [40][41][42] carboxylic acids; 37,[43][44][45][46] polymers for NPs' encapsulations as dextran, [47][48][49] polyethylene glycol (PEG), [50][51][52] polyacrylic acid, [53][54][55][56] biopolymers, [57][58][59][60] , etc. (Table 1S).…”