Abstract
A well-established method for treating cancerous tumors is magnetic hyperthermia, which uses localized heat generated by the relaxation mechanism of magnetic nanoparticles (MNPs) in a high-frequency alternating magnetic field. In this work, we investigate the heating efficiency of cylindrical NiFe MNPs, fabricated by template-assisted pulsed electrodeposition combined with differential chemical etching. The cylindrical geometry of the MNP enables the formation of the triple vortex state, which increases the heat generation efficiency by four times. Using time-dependent calorimetric measurements, the specific absorption rate (SAR) of the MNPs was determined and compared with the numerical calculations from micromagnetic simulations and vibrating sample magnetometer measurements. The magnetization reversal of high aspect ratios MNPs showed higher remanent magnetization and low-field susceptibility leading to higher hysteresis losses, which was reflected in higher experimental and theoretical SAR values. The SAR dependence on magnetic field strength exhibited small SAR values at low magnetic fields and saturates at high magnetic fields, which is correlated to the coercive field of the MNPs and a characteristic feature of ferromagnetic MNPs. The optimization of cylindrical NiFe MNPs will play a pivotal role in producing high heating performance and biocompatible magnetic hyperthermia agents.
Highlights
The applications for magnetic nanoparticles (MNPs) have been extensively researched in biomedical fields, such as magneto-mechanical cell destruction [1–4], magnetic resonance imaging [5–7], drug delivery [8–10], and magnetic hyperthermia [11–14], to compensate for the drawbacks of current diagnosis and therapy methods
Characterization of Magnetic Nanoparticles The composition of the fabricated cylindrical NiFe MNPs is determined by High-potential electrodeposition pulse (VH) or the electrolyte composition
The trend of inplane Hc is higher than the out-of-plane Hc for Ni-rich MNPs (Ni88Fe12, Ni76Fe24, and Ni52Fe48), but reversed for Fe-rich MNPs (Ni36Fe64), which is in agreement with the previous studies on anomalous co-deposition of NiFe nanowires [37]
Summary
The applications for magnetic nanoparticles (MNPs) have been extensively researched in biomedical fields, such as magneto-mechanical cell destruction [1–4], magnetic resonance imaging [5–7], drug delivery [8–10], and magnetic hyperthermia [11–14], to compensate for the drawbacks of current diagnosis and therapy methods. The greatest advantage of MNPs is that they can be controlled remotely by an external magnetic field. Different biomedical applications require specific rotation mechanisms in diverse magnetic field configurations. Néel (tN) and Brownian (tB) relaxation time are given by: tN 1⁄4 t0ekKBVT and tB 1⁄4 3η V kBT where η is the viscosity coefficient, t0 is the inverse attempt frequency, K is the magnetic anisotropy constant, V is the volume of MNPs, kB is the Boltzmann constant, and T is the temperature. The faster mechanism dominates, but both Néel and Brownian
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