Magnetic nanoparticle heating efficiency reveals magneto-structural differences when characterized with wide ranging and high amplitude alternating magnetic fields

Abstract

Magnetic nanoparticles can create heat that can be exploited to treat cancer when they are exposed to alternating magnetic fields (AMF). At a fixed frequency, the particle heating efficiency or specific power loss (SPL) depends upon the magnitude of the AMF. We characterized the amplitude-dependent SPL of three commercial dextran-iron oxide nanoparticle suspensions through saturation to 94 kA/m with a calorimeter comprising a solenoid coil that generates a uniform field to 100 kA/m at ∼150 kHz. We also describe a novel method to empirically determine the appropriate range of the heating curve from which the SPL is then calculated. These results agree with SPL values calculated from the phenomenological Box-Lucas equation. We note that the amplitude-dependent SPL among the samples was markedly different, indicating significant magneto-structural variation not anticipated by current models.

Long‐Term Stability and Reproducibility of Magnetic Colloids Are Key Issues for Steady Values of Specific Power Absorption over Time

“…[35][36] The product A*B represents the initial heat rate and can be used to obtain the SPA from the derivative of Eq. 6…”

Field dependent transition to the non-linear regime in magnetic hyperthermia experiments: Comparison between maghemite, copper, zinc, nickel and cobalt ferrite nanoparticles of similar sizes

“…In fact, recently Bordelon et al pointed out that the previous procedure (initial or Box-Lucas) fails to yield the correct SAR at high-field amplitudes. 36 Moreover, the authors proposed to extract the heating rate from the analysis of the difference between subsequent recording temperatures at a given time range. Here we propose a similar approach but, instead of using the experimental data directly, we first fit the profile with a Bidose equation and then differentiate the fitted curve.…”

Characterization of intratumor magnetic nanoparticle distribution and heating in a rat model of metastatic spine disease

“…Detailed descriptions of the design, build, and characterization of the modified solenoid coil have been published previously. 6,7,33 Briefly, when combined the system is capable of producing a homogeneous flux density AC magnetic field (at 150 kHz) in a cylindrical volume having a 5-cm diameter with a > 6-cm length, for peak-topeak amplitudes between 4 kA/m and 95 kA/m. The field amplitude can be dynamically controlled by adjusting the power supply output voltage.…”

“…The AMF system has been previously described, 6,7 and it comprises 4 main components: a power supply, an external impedance matching network, a modified solenoid coil as the inductor, and a closed-circulating water cooling system. The power supply is an 80-kW induction heating system manufactured by PPECO that provides an alternating current to a resonant circuit with variable frequency between 135 kHz and 440 kHz.…”

“…The SLP was estimated from the slope (DT/Dt) of the time-temperature curve by using methods previously described. 6 Briefly, a 1-ml volume of nanoparticle suspension was placed in a standard 12-mm polystyrene test tube and inserted into the insulating sample holder. Equilibrium between the probe, sample, and the calorimeter was confirmed and the AMF power was applied.…”