A noninvasive, remote and precise method for temperature and concentration estimation using magnetic nanoparticles

Abstract

This study describes an approach for remote measuring of on-site temperature and particle concentration using magnetic nanoparticles (MNPs) via simulation and also experimentally. The sensor model indicates that under different applied magnetic fields, the magnetization equation of the MNPs can be discretized to give a higher-order nonlinear equation in two variables that consequently separates information regarding temperature and particle concentration. As a result, on-site tissue temperature or nanoparticle concentration can be determined using remote detection of the magnetization. In order to address key issues in the higher-order equation we propose a new solution method of the first-order model from the perspective of the generalized inverse matrix. Simulations for solving the equation, as well as to optimize the solution of higher equations, were carried out. In the final section we describe a prototype experiment used to investigate the measurement of the temperature in which we used a superconducting magnetometer and commercial MNPs. The overall error after nine repeated measurements was found to be less than 0.57 K within 310-350 K, with a corresponding root mean square of less than 0.55 K. A linear relationship was also found between the estimated concentration of MNPs and the sample's mass.

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

“…At this point it is interesting to emphasize that both magnetic and metallic nanoparticles can be used not only to produce heat but also to provide the thermometric property, optical or magnetic, to build a remote and suitable nanothermometer. Nanosized cubic ferrites can be used as remotely-driven heaters [41] while providing remote temperature sensing using temperaturedependent magnetic properties [32][33][34][35]. Likewise, the metallic nanoparticle-based platform can be used for remote heating [44][45][46] as well as for remote temperature sensing [47,48].…”

“…Terbium (III) encapsulated as a complex within a polymeric nanoparticle has been used as a nanothermometer in the temperature range of 15 to 65°C [27]. Actually, the usual thermometric properties assessed from rare-earth doped materials, such as the temperature dependence of the emission intensity [24,25] and lifetime [32], particularly in the case of thermally-coupled optical transitions, are not easily described.…”

“…The thermometric property of magnetic-based nanothermometers proposed up to date is either based on magnetization [33][34][35] or susceptibility [32] measurements. Similarly to the optical approaches magnetic-based nanothermometry relies on remote excitation as well as on remote detection of the thermometric magnetic property.…”

“…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.…”