A dynamic hysteresis meter for studying ferrofluids designed for magnetic hyperthermia

Abstract

An AC magnetometer system is developed to determine the specific absorption rate (SAR) of ferrofluids designed to work in the range of interest for magnetic hyperthermia. The experimental setup contains a set of configurable RL coil sensors (resistance plus inductance) to obtain the inner area of the dynamic hysteresis loops of colloidal dispersions, which are stimulated using a multi-range alternating magnetic field generator. This magnetometer is suitable for covering the frequency band of 100-450 kHz, and special considerations concerning sample size and placement inside the magnetic field region are taken into account. The performance of the system is tested using a ferrofluid of water-dispersed iron oxide nanoparticles. The SAR determined with the developed system is compared with that obtained using the typical calorimetric procedure. The observations are consistent with both kinds of measurement, and also coincide with the results for other previously reported experimental systems.

A Ferrofluid with Surface Modified Nanoparticles for Magnetic Hyperthermia and High ROS Production

“…In MHT, the absorbed power density P from an alternant magnetic field, which is transmitted to a volume V using a ferrofluid, can be modeled through the linear response theory Equation (1) [19,20]. This approximation involves a set of ideal physical conditions because it takes into account perfectly suspended MNPs (colloidal suspension) identical in diameter σ or volume (Vp), plus other magnetic properties of superparamagnetic monodomains.…”

Development of an automated theranostic platform combining magnetomotive ultrasound and magnetic hyperthermia

“…In this case, the magnetization in response to an external magnetic field follows the Langevin function, which is an analytical approximation applicable in situations where the magnetic field H is either static or low-frequency, typically below 10 Hz [79,80]. However, in the case of alternating magnetic fields with higher frequencies, where the timescale aligns with the characteristic relaxation time of the system, a dynamic delay arises between the magnetization and the magnetic field, originating the so-called dynamic hysteresis [78,80,81]. This delay is associated with the effective relaxation time According to the linear response theory [37], when the amplitude of the magnetic field is sufficiently low, the susceptibility can be represented as a complex constant ' i "…”

“…However, the technology of resonant inverters in MH has not yet been extended beyond the characterization of MNPs, small animal in vivo studies, and some limited clinical cases [8,32,81,89,90]. This is due to the inherent challenges associated with implementing complex control and safety systems required for their broader application.…”