Untangling the Influence of Particle-Intrinsic Parameters and Experimental Conditions in Magnetic Fluid Hyperthermia

DANIELA P. VALDÉS; ENIO LIMA JR.; ROBERTO D. ZYSLER; GERARDO F. GOYA; EMILIO DE BIASI

Londres

Conferencia; 13th International Conference on the Scientific and Clinical Applications of Magnetic Carriers; 2022

Magnetic Carrier Society

Optimization of the specific power absorption (SPA) of magnetic nanoparticles (MPs) for magnetic fluid hyperthermia (MH) applications is currently focused on designing MNPs with certain properties and findingfavourable experimental conditions for each system. However,the role of relevant parameters in the relaxation is still under discussion. Moreover, in vitro and in vivoexperiments generally lead to interacting M Nsystems due to agglomeration in the cellular environment. In the particularcase of linear aggregates, the impact of dipolar interactions on the SPA of the system is still an open discussion: there are reports of both beneficial [1] and detrimental [2] effects on the SPA.Through a nonlinear model [3-5] for the magnetic relaxation of single-domain M N s with uniaxial effective anisotropy, we simulated systems with different particle-intrinsic parameters (size, anisotropy) and experimental conditions (frequency, interactions). We determined four regions (I-IV) of magnetic behaviour as a function of relative anisotropy (anisotropy field with respect to the amplitude of the ac field), that dictate the SPA in M H experiments through the area enclosed by hysteresis loops (see Figure) [4].The boundaries between regions changewith all of these parameters. We analyzed linear M N arrangements and found out that, for the low relative anisotropy range, dipolar interactions increase the SPA while they are detrimental for the range of high relative anisotropy. Thisresolves the seemingly contradictory results of interaction effects in this kind of aggregates reported in the literature [1,2]. For low relative anisotropy regions, we also explained how the enhancement ofthe SPA by dipolar interactions (reflected by an increase in coercivity) is actually caused by the shiftbetween the local and the applied magnetic field [5].We also provide a simple, analytical tool aimed at the design of M N s and the choice of the experimental conditions for optimal heating. Through the thermal interpretation ofits validity range, we conclude that systems with low-thermal-fluctuation influence are the best candidates forMFH due to theirhigh SPA values.