Nanoparticle temperature estimation in combined ac and dc magnetic fields

Abstract

The harmonics produced by the nonlinear magnetization of superparamagnetic nanoparticles have been utilized in a number of budding medical devices. Here we expand on an earlier technique for quantitatively measuring nanoparticle temperature in a purely ac field by including the presence of a static field. The ability to quantify nanoparticle temperature by tracking changes in the 4th/2nd harmonic ratio is presented and shown to achieve an accuracy of 0.79 K. The advantage of even harmonics, issues with odd harmonics in the presence of a static field and the potential for future incorporation into an imaging system are discussed.

Harmonic phase angle as a concentration‐independent measure of nanoparticle dynamics

“…4,5 Cellular uptake can also have an impact on treatments such as magnetic particle hyperthermia and an ability to monitor such uptake could prove beneficial. Harmonics have already been used to quantify temperature; 16,17 the ability to remotely quantify viscosity or stiffness on the nanoscale would be beneficial in the study of diseases and for improved understanding of the underlying physics.…”

“…Monitoring temperature's effect on the harmonic spectrum, through a ratio of harmonic amplitudes, has been proposed as a means of remotely quantifying nanoparticle temperature. 16,17 This technique relied on a theory-driven relation between nanoparticle temperature and the strength of the applied magnetic field. Dynamic effects such as changes in viscosity or molecular binding have also been shown to influence a ratio of harmonics using a technique termed magnetic spectroscopy of nanoparticle Brownian motion ͑MSB͒.…”

Remote Hyperthermia, Drug Delivery and Thermometry: The Multifunctional Platform Provided by Nanoparticles

“…As far as the clinical use is concerned the drawbacks of the actual optical-based nanothermometers rely on biocompatibility (usual semiconductor-based core nanoprobes or dye-based shell moieties are toxic), robustness (typical bleaching of organic-based shell moieties) or temperature accuracy (no better than 0.3°C nowadays), or even combination of these factors. Moreover, due to limitations imposed by living tissues on the optical penetration of light (optical therapeutic window in the 700-1100 nm wavelength range), noninvasive clinical use of optical excitation and signal pickup is a huge challenge, not yet solved, except for very special therapeutic applications, as for instance the photodynamic therapy for treatment (heating monitoring) ofof magnetic nanoprobes for remote assessing site-targeted temperatures [32][33][34][35]. Typical magnetic nanoprobes are surface-functionalized cubic ferrites, such as magnetite and maghemite nanoparticles [32][33][34][35][36].…”

“…Moreover, due to limitations imposed by living tissues on the optical penetration of light (optical therapeutic window in the 700-1100 nm wavelength range), noninvasive clinical use of optical excitation and signal pickup is a huge challenge, not yet solved, except for very special therapeutic applications, as for instance the photodynamic therapy for treatment (heating monitoring) ofof magnetic nanoprobes for remote assessing site-targeted temperatures [32][33][34][35]. Typical magnetic nanoprobes are surface-functionalized cubic ferrites, such as magnetite and maghemite nanoparticles [32][33][34][35][36]. Actually, up to date, for noninvasively clinical use the available data favour magnetic nanothermometry as compared to optical nanothermometry.…”

High Homogeneous Saddle Drive Field Coil for Magnetic Particle Spectroscopy

“…In contrast to an MPI scanning device, the spectrometry has no selection field, but may have an homogeneous offset field [3]. To conclude from the magnetization of a particle to its performance in a scanning device, spectrometers lack of a multi-dimensional drive and offset field.…”