Relevance of Brownian relaxation as power absorption mechanism in Magnetic Hyperthermia

MARIA PILAR CALATAYUD; FERNANDEZ-PACHECO, RODRIGO; M RICARDO IBARRA; TORRES, TEOBALDO E.; SANZ, BEATRIZ; MAYORAL, ALVARO; GERARDO F GOYA; ENIO LIMA JR; ALFONSO IBARRA; CLARA MARQUINA

Gijon

Conferencia; International Conference on Fine Particle Magnetism; 2019

The Linear Response Theory (LRT) is a widely accepted framework to analyse the power absorption of magnetic nanoparticles for magnetic fluid hyperthermia. Its validity is restricted to low applied fields and/or to highly anisotropic magnetic nanoparticles. Here, we present a systematic experimental analysis and numerical calculations of the specific power absorption(SPA) by highly anisotropic cobalt ferrite magnetic nanoparticles with different average sizes and in different viscous media. The predominance of Brownian relaxation as the origin of the magnetic losses in these particles is established,and the changes of the SPA with the viscosity of the carrier liquid are consistent with the LRT approximation. The impact of viscosity on the SPA is relevant for the design of MNPs intended forheatingthe intracellular medium in in vitro and in vivo hyperthermia experiments. The combined numerical and experimental analyses presented here shed light on the underlying mechanisms that make highly anisotropic MNPs unsuitable for magnetic hyperthermia. Our workincludes also in vitro hyperthermia experiments on a culture of Co-ferrite NP-loaded cells. A detailed characterization of the intracellular distribution of the MNP has been also undertaken, by advanced microscopy tools.BesidesTransmission Electron microscopy (TEM), a study by Focused Ion Beam-Scanning Electron Microscopy (FIB-SEM)has been carried out, which has allowed the 3D reconstructionof the cellsand the precise visualization of the MNP.