In this work it is shown a precise way to optimize the heat generation in high viscosity magnetic colloids, by adjusting the Néel relaxation time in core/shell bimagnetic nanoparticles, for Magnetic Fluid Hyperthermia applications. To pursue this goal, Fe3O4/ZnxCo1-xFe2O4 core/shell nanoparticles were synthesized with 8.5 nm mean core diameter, encapsulated in a shell of ~1.1 nm of thickness, where the Zn atomic ratio (Zn/(Zn+Co) at%) changes from 33 at% to 68 at%. The magnetic measurements are consistent with a rigid interface coupling between the core and shell phases, where the effective magnetic anisotropy systematically decreases when the Zn concentration increases, without a significant change of the saturation magnetization. Experiments of magnetic fluid hyperthermia of 0.1 wt% of these particles dispersed in water, DMEM (Dulbecco modified Eagles minimal essential medium) and a high viscosity butter oil, result in a large specific loss power (SLP), up to 150 W/g, when the experiments are performed at 571 kHz and 200 Oe. The SLP was optimized adjusting the shell composition, showing a maximum for intermediate Zn concentration. This study shows a way to maximize the heat generation in viscous media like cytosol, for those biomedical applications that requiere smaller particle sizes .
Adjusting the Néel relaxation time of Fe3O4/ZnxCo1-xFe2O4 core/shell nanoparticles for optimal heat generation in magnetic hyperthermia / Fabris, Fernando; Lohr, Javier Hernán; Lima, Enio; de Almeida, Adriele Aparecida; Troiani, Horacio; Rodríguez, Luis M; Vásquez Mansilla, Marcelo; Aguirre, Myriam; Goya, Gerardo Fabian; Rinaldi, Daniele; Ghirri, Alberto; Peddis, Davide; Fiorani, Dino; Zysler, Roberto D; De Biasi, Emilio; Winkler, Elin. - In: NANOTECHNOLOGY. - ISSN 0957-4484. - ELETTRONICO. - (2020). [10.1088/1361-6528/abc386]