Temperature-dependent heating efficiency of magnetic nanoparticles for applications in precision nanomedicine

Abstract

The power released by magnetic nanoparticles submitted to an alternating driving field is temperature dependent owing to the variation of the fundamental magnetic properties.

Fine tuning and optimization of magnetic hyperthermia treatments using versatile trapezoidal driving-field waveforms

“…[54][55][56] However, in the application of magnetite nanoparticles to magnetic hyperthermia, the temperature dependence of both magnetization and magnetic anisotropy cannot be neglected. 35 In this paper, the temperature behaviour of M s and the Curie temperature (T C ¼ 856 K) are taken from published data. 35,57 Uniaxial anisotropy is assumed to vary according to the third power of magnetization: 35,58…”

“…15,38 In magnetic hyperthermia, the problem of correctly predicting the steadystate temperature is complicated by the fact that the heating power P in is itself temperature-dependent. 35 Power dissipation by a system of non-interacting nanoparticles is oen described in the linear response regime; 64 however, for the driving eld values most commonly used in practical applications 38 (100-250 Oe, i.e. 9-20 kA m À1 ) the limits of validity of the linear theory are overcome, and the magnetic response of the system is no longer linear, as clearly shown by the rate equation approach.…”

“…69 Another important factor is the difference between healthy and malignant tissues when physiological properties important for heat dissipation, such as the tissue-blood perfusion rate, are considered; possible thermal consequences and related dangers have been discussed elsewhere from a physicist's viewpoint. 35 As a matter of fact, all the mentioned approaches take origin from the classical Fourier equation, with suitable adaptations introduced to account for specic heat sources, heat transfer mechanisms and heat sinks typical of living tissues. 65 It should be stressed that the emphasis of all the bioheat equations is more on the processes governing the way the heat is transported and dissipated in a living body rather than on the physical properties of the internal heat source, i.e., the processes determining the energy deposition rate.…”

“…On the contrary, the present paper is specially aimed to provide a proof of principle of the tapered waveform technique, describing how and how much can the power released by magnetic nanoparticles be enhanced and controlled. As a consequence, we have taken the simplest possible thermal model, i.e., the standard Fourier equation in radial symmetry 35,70,71 with a distributed heat source and with boundary conditions simulating heat loss dominated by forced convection, a common situation in living bodies where the excess heat generated in a small region is basically taken away by blood ow. 65 Therefore, our results can be of interest not only for in vitro experiments, but also for in vivo healing treatments.…”

“…The loss of heat in the medium is taken into account by introducing an appropriate boundary condition, i.e., by assuming that the heat exchange at the sphere/uid boundary occurs by convection at local blood's temperature and is determined by the process of tissue-blood perfusion, an effect which greatly varies from tissue to tissue. 35,78 The boundary condition is:…”