The influence of magnetic nanoparticle concentration with dextran polymers in agar gel on heating efficiency in magnetic hyperthermia

The article presents the results of research on the effect of magnetic hyperthermia performed on agar gel samples containing magnetite nanoparticles coated with dextran polymers for different molar weight M (150 kDa, 70 kDa, and 40 kDa). Regardless of the difference in molar dextran weights, these samples differed in a mass concentration of nanoparticles in the ferrogel C 0 (1.602 mg/cm 3, 2.506 mg/cm 3, 3.311 mg/cm 3, and 4.218 mg/cm 3). In the case of the highest magnetic field value H (20 kA·m −1), the specific loss power SPL reaches 70 W·g −1 for nanoparticles with 150 kDa dextran at a concentration of nanoparticles C 0 = 1.602 mg/cm 3. An oscillating magnetic field with an amplitude up to 20 kA·m −1 and a frequency of 357 kHz was used in the study

Influence of high frequency rotating magnetic field on the effect of heating magnetic fluid

The article describes the necessary conditions for the phenomenon of thermal energy release in a magnetic fluid placed in a high-frequency rotating magnetic field. The minimum amplitude of the magnetic field was calculated and the thermal power released (by the rotating spherical nanoparticles in the viscous medium) was estimated. The estimations were based on the assumption that the magnetic relaxation times (τN and τB) and the magnetic field rotation period (τrot) meet the condition: τN>>τrot>>τB. The principle of operation and construction of the device generating a high-frequency rotating magnetic field is described. Preliminary experimental studies were carried out using a magnetic fluid with magnetite nanoparticles that indicated magnetic relaxation as the cause of the released heat. The value of the absorption rate in the experiment and its dependence on the strength of the magnetic field were determined

Two-Phase System for Generating a Higher-Frequency Rotating Magnetic Field Excited Causing Hyperthermic Effect in Magnetic Fluids

This article presents a new method of excitation for a fast-changing rotating magnetic field (RMF) of higher frequencies (HF) causing the hyperthermic effect in magnetic fluids. The method proposed here uses a magnetic field exciter (inductor) consisting of a ferrite magnetic circuit and a system of coils connected in a two-phase arrangement. The proposed system is powered by two higher-frequency rectangular signals, with a 90-degree phase shift between each other, through HF transformers with ferrite cores. This paper presents the outcomes of the operation of RMFs in the frequency range of 38 kHz to 190 kHz, with a value of amplitude of magnetic field intensity H equal to 20 kA/m and increasing temperature, in a sample of APG513 magnetic liquid. The obtained results show that, in the range of the magnetic field intensities of moderate values, at a constant frequency f, the values of the time derivative of temperature are proportional to the square of the magnetic field intensity dT/dt~H2. Moreover, the values of the temperature rate, which are measured with the constant value of the magnetic field intensity, are proportional to the square of the frequency dT/dt~f2. At higher amplitudes of the RMF, the relationship dT/dt~H2 is no longer fulfilled, and an inflexion point of this function appears. In the case of the highest values of the achieved intensity amplitudes (H = 20 kA/m), the parameter of the Langevin function achieves a value equal to ξ = 6

Two-Phase System for Generating a Higher-Frequency Rotating Magnetic Field Excited Causing Hyperthermic Effect in Magnetic Fluids

This article presents a new method of excitation for a fast-changing rotating magnetic field (RMF) of higher frequencies (HF) causing the hyperthermic effect in magnetic fluids. The method proposed here uses a magnetic field exciter (inductor) consisting of a ferrite magnetic circuit and a system of coils connected in a two-phase arrangement. The proposed system is powered by two higher-frequency rectangular signals, with a 90-degree phase shift between each other, through HF transformers with ferrite cores. This paper presents the outcomes of the operation of RMFs in the frequency range of 38 kHz to 190 kHz, with a value of amplitude of magnetic field intensity H equal to 20 kA/m and increasing temperature, in a sample of APG513 magnetic liquid. The obtained results show that, in the range of the magnetic field intensities of moderate values, at a constant frequency f, the values of the time derivative of temperature are proportional to the square of the magnetic field intensity dT/dt~H2. Moreover, the values of the temperature rate, which are measured with the constant value of the magnetic field intensity, are proportional to the square of the frequency dT/dt~f2. At higher amplitudes of the RMF, the relationship dT/dt~H2 is no longer fulfilled, and an inflexion point of this function appears. In the case of the highest values of the achieved intensity amplitudes (H = 20 kA/m), the parameter of the Langevin function achieves a value equal to ξ = 6

Tuning of Magnetic Hyperthermia Response in the Systems Containing Magnetosomes

A number of materials are studied in the field of magnetic hyperthermia. In general, the most promising ones appear to be iron oxide particle nanosystems. This is also indicated in some clinical trial studies where iron-based oxides were used. On the other hand, the type of material itself provides a number of variations on how to tune hyperthermia indicators. In this paper, magnetite nanoparticles in various forms were analyzed. The nanoparticles differed in the core size as well as in the form of their arrangement. The arrangement was determined by the nature of the surfactant. The individual particles were covered chemically by dextran; in the case of chain-like particles, they were encapsulated naturally in a lipid bilayer. It was shown that in the case of chain-like nanoparticles, except for relaxation, a contribution from magnetic hysteresis to the heating process also appears. The influence of the chosen methodology of magnetic field generation was also analyzed. In addition, the influence of the chosen methodology of magnetic field generation was analyzed. The application of a rotating magnetic field was shown to be more efficient in generating heat than the application of an alternating magnetic field. However, the degree of efficiency depended on the arrangement of the magnetite nanoparticles. The difference in the efficiency of the rotating magnetic field versus the alternating magnetic field was much more pronounced for individual nanoparticles (in the form of a magnetic fluid) than for systems containing chain nanoparticles (magnetosomes and a mix of magnetic fluid with magnetosomes in a ratio 1:1)