Magnetic nanoparticle based hyperthermia emerged as a potential tool for treating malignant tumours. The efficiency of the method relies on the knowledge of magnetic properties of the samples; in particular, knowledge of the frequency dependent complex magnetic susceptibility is vital to optimize the irradiation conditions and to provide feedback for material science developments. We study the frequency-dependent magnetic susceptibility of an aqueous ferrite suspension for the first time using non-resonant and resonant radiofrequency reflectometry. We identify the optimal measurement conditions using a standard solenoid coil, which is capable of providing the complex magnetic susceptibility up to 150 MHz. The result matches those obtained from a radiofrequency resonator for a few discrete frequencies. The agreement between the two different methods validates our approach. Surprisingly, the dynamic magnetic susceptibility cannot be explained by an exponential magnetic relaxation behavior even when we consider a particle size-dependent distribution of the relaxation parameter.
The use of gold nanoparticles for hyperthermia therapy in near infrared (NIR) spectral regions has catalysed substantial research efforts due to the potential impact in clinical therapy applications. However, the photoscattering effect scaling with the square of the nanoparticle volume leads to a low absorption efficiency, which has hindered the utility of gold nanoparticles in NIR II regions above 1000 nm. Here, we conquer this limit by introducing hyperbolic metamaterial nanoparticles that are made of multi-layered gold/dielectric nanodisks and exhibit >70% absorption efficiency in the NIR I…
Magnetic nanoparticles (MNPs) have been extensively used in drug/gene delivery, hyperthermia therapy, magnetic particle imaging (MPI), magnetic resonance imaging (MRI), magnetic bioassays, etc. With proper surface chemical modifications, physicochemically stable and non-toxic MNPs are emerging contrast agents and tracers for in vivo MRI and MPI applications. Herein, we report the high magnetic moment, irregularly shaped γ'-Fe4N nanoparticles for enhanced hyperthermia therapy and T2 contrast agent for MRI application. The static and dynamic magnetic properties of γ'-Fe4N nanoparticles are chara…
Hyperthermia has been in use for many years; as a potential alternative modality for cancer treatment. In this paper, an experimental investigation of microwave assisted thermal heating (MWATH) of tissue phantom using a domestic microwave oven has been reported. Computer simulations using finite element method based tools was also carried out to support the experimental observations and probe insight on the thermal transport aspects deep within the tissue phantom. A good agreement between predicted and measured temperature were achieved. Furthermore, experiments were conducted to investigate t…
A linear combination of spherically symmetric heat sources is shown to provide optimal stationary thermal distribution in magnetic hyperthermia. Furthermore, such spatial location of heat sources produces suitable temperature distribution in biological medium even for assemblies of magnetic nanoparticles with a moderate value of specific absorption rate (SAR), of the order of 100 - 150 W/g. We also demonstrate the advantage of using assemblies of magnetic nanocapsules consisting of metallic iron nanoparticles covered with non magnetic shells of sufficient thickness in magnetic hyperthermia. Ba…
We focus on an in-depth study of the forced dynamics of a ferromagnetic single-domain uniaxial nanoparticle placed in a viscous fluid and driven by an external rotating magnetic field. The process of conversion of magnetic and mechanical energies into heat is a physical basis for magnetic fluid hyperthermia that is very promising for cancer treatment. The dynamical approximation allows us to establish the limits of the heating rate and understand the logic of selection of the system parameters to optimize the therapy. Based on the developed analytical and numerical tools, we analyze from a sin…
Magnetosomes, i.e. nanoparticles synthesized in nature by magnetotactic bacteria, are very promising for use in magnetic hyperthermia for the cancer treatment. Using the solution of the stochastic Landau-Lifshitz equation we calculate the specific absorption rate in an alternating magnetic field of assemblies of magnetosome chains depending on the particle size, the distance between particles in a chain, and the angle of the applied magnetic field with respect to the chain axis. The dependence of specific absorption rate on the distance between the chain particles is shown to have a bell-shape…
Nanomagnetic hyperthermia (NMH) is intensively studied with the prospect of cancer therapy. A major challenge is to determine the dissipated power during in vivo conditions and conventional methods are either invasive or inaccurate. We present a non-calorimetric method which yields the heat absorbed during hyperthermia: it is based on accurately measuring the quality factor change of a resonant radio frequency circuit which is employed for the irradiation. The approach provides the absorbed power in real-time, without the need to monitor the sample temperature as a function of time. As such, i…
In Specific Power Absorption (SPA) models for Magnetic Fluid Hyperthermia (MFH) experiments, the magnetic relaxation time of the nanoparticles (NPs) is known to be a fundamental descriptor of the heating mechanisms. The relaxation time is mainly determined by the interplay between the magnetic properties of the NPs and the rheological properties of NPs environment. Although the role of magnetism in MFH has been extensively studied, the thermal properties of the NPs medium and their changes during of MFH experiments have been so far underrated. Here, we show that ZnxFe3-xO4 NPs dispersed throug…
Absorbed power of nanoparticles during magnetic hyperthermia can be well determined from changes in the quality factor ($Q$ factor) of a resonator, in which the radiofrequency (RF) absorbent is placed. We present an order of magnitude improvement in the $Q$ factor measurement accuracy over conventional methods by studying the switch-on and off transient signals of the resonators. A nuclear magnetic resonance (NMR) console is ideally suited to acquire the transient signals and it also allows to employ the so-called pulse phase-cycling to remove transient artifacts. The improved determination of…
We address the issue of inter-particle dipolar interactions in the context of magnetic hyperthermia. More precisely, the main question dealt with here is concerned with the conditions under which the specific absorption rate is enhanced or reduced by dipolar interactions. For this purpose, we propose a theory for the calculation of the AC susceptibility, and thereby the specific absorption rate, for a monodisperse two-dimensional assembly of nanoparticles with oriented anisotropy, in the presence of a DC magnetic field, in addition to the AC magnetic field. We also study the competition betwee…
Magnetic nanoparticles (MNPs) have been extensively used as tiny heating sources in magnetic hyperthermia therapy, contrast agents in magnetic resonance imaging (MRI), tracers in magnetic particle imaging (MPI), carriers for drug/gene delivery, etc. There have emerged many magnetic nanoparticle/microbeads suppliers since the last decade, such as Ocean NanoTech, Nanoprobes, US Research Nanomaterials, Miltenyi Biotec, micromod Partikeltechnologie GmbH, and nanoComposix, etc. In this paper, we report the physical and magnetic characterizations on iron oxide nanoparticle products from Ocean NanoTe…
Nanomaterials, in addition to their small size, possess unique physicochemical properties that differ from the bulk materials, making them ideal for a host of novel applications. Magnetic nanoparticle (MNP) is one important class of nanomaterials that have been widely studied for their potential applications in nanomedicine. Due to the fact that MNPs can be detected and manipulated by remote magnetic fields, it opens a wide opportunity for them to be used in vivo. Nowadays, MNPs have been used for diverse applications including magnetic biosensing (diagnostics), magnetic imaging, magnetic sepa…
The deterministic rotation of a ferromagnetic nanoparticle in a fluid is considered. The heating arising from viscous friction of a nanoparticle driven by circularly and linearly polarized alternating magnetic fields is investigated. Since the power loss of such fields depends on the character of the induced motion of a nanoparticle, all types of particle trajectories are described in detail. The dependencies of the power loss on the alternating field parameters are determined. The optimal conditions for obtaining the maximum heating efficiency are discussed. The effect of heating enhancement …
National Institute of Standards and Technology（美国国家标准与技术研究院）；University of Colorado（科罗拉多大学）；Institute for Bioscience and Biotechnology Research (IBBR)（生物科学与生物技术研究所）；University of Maryland, College Park（马里兰大学帕克分校）
Magnetic nanoparticles (MNPs) have been extensively used as contrasts and tracers for bioimaging, heating sources for tumor therapy, carriers for controlled drug delivery, and labels for magnetic immunoassays. Here, we describe a MNP relaxation dynamics-based magnetic particle spectroscopy (MPS) method for the quantitative detection of molecular biomarkers. In MPS measurements, the harmonics of oscillating MNPs are recorded and used as a metric for the freedom of rotational motion, which indicates the bound states of the MNPs. These harmonics can be collected from microgram quantities of iron …
The role of thermal relaxation in nanoparticle melting is studied using a mathematical model based on the Maxwell--Cattaneo equation for heat conduction. The model is formulated in terms of a two-phase Stefan problem. We consider the cases of the temperature profile being continuous or having a jump across the solid-liquid interface. The jump conditions are derived from the sharp-interface limit of a phase-field model that accounts for variations in the thermal properties between the solid and liquid. The Stefan problem is solved using asymptotic and numerical methods. The analysis reveals tha…
