Magnetic and thermal characterization of core-shell Fe-Oxide@SiO ₂ nanoparticles for hyperthermia applications

Nanoparticles for magnetic hyperthermia pose significant constraints in their size and composition to ensure cellular uptake and biocompatibility, while still requiring significant hysteresis losses exploitable at electromagnetic field values and intensities not exceeding safety limits for the human body. In this paper, core-shell Fe-oxide@SiO ₂ nanoparticles have been synthesized, and their size has been controlled so that the blocked-to-superparamagnetic transition is close to room temperature. Their size remains, therefore, as small as possible, while still displaying significant hysteresis losses in dynamic conditions (electromagnetic fields up to 48 kA/m at 100 kHz). Static loops measured by vibrating sample magnetometry and dynamic loops measured by a custom B-H tracer are used to characterize the paticles' magnetic properties, as well as a custom-built, fully modeled, hyperthermia setup. The specific absorption rate is obtained either from static and dynamic loop areas or from direct hyperthermia measurements. Dynamic loops are shown to be a good estimator of specific absorption rate values.