scholarly journals An adapted Coffey model for studying susceptibility losses in interacting magnetic nanoparticles

2015 ◽  
Vol 6 ◽  
pp. 2173-2182 ◽  
Author(s):  
Mihaela Osaci ◽  
Matteo Cacciola
Keyword(s):  
Relaxation Time ◽  
Magnetic Fields ◽  
Biomedical Applications ◽  
Tumor Therapy ◽  
Linear Response Theory ◽  
Orientation Model ◽  
Specific Loss Power ◽  
Acceptable Range ◽  
Nanoparticle System ◽  
Néel Relaxation

Background: Nanoparticles can be used in biomedical applications, such as contrast agents for magnetic resonance imaging, in tumor therapy or against cardiovascular diseases. Single-domain nanoparticles dissipate heat through susceptibility losses in two modes: Néel relaxation and Brownian relaxation. Results: Since a consistent theory for the Néel relaxation time that is applicable to systems of interacting nanoparticles has not yet been developed, we adapted the Coffey theoretical model for the Néel relaxation time in external magnetic fields in order to consider local dipolar magnetic fields. Then, we obtained the effective relaxation time. The effective relaxation time is further used for obtaining values of specific loss power (SLP) through linear response theory (LRT). A comparative analysis between our model and the discrete orientation model, more often used in literature, and a comparison with experimental data from literature have been carried out, in order to choose the optimal magnetic parameters of a nanoparticle system. Conclusion: In this way, we can study effects of the nanoparticle concentration on SLP in an acceptable range of frequencies and amplitudes of external magnetic fields for biomedical applications, especially for tumor therapy by magnetic hyperthermia.

Regarding the Néel relaxation time constant in magnetorelaxometry

2014 ◽  
Vol 116 (16) ◽  
pp. 163914 ◽  
Author(s):  
J. Leliaert ◽  
A. Coene ◽  
G. Crevecoeur ◽  
A. Vansteenkiste ◽  
D. Eberbeck ◽  
...  
Keyword(s):  
Relaxation Time ◽  
Time Constant ◽  
Relaxation Time Constant ◽  
Néel Relaxation

scholarly journals Difference between Brownian and Néel relaxation mechanisms in a magnetizing field

2021 ◽  
pp. 14-20
Author(s):  
Alexander V. Lebedev ◽  
Keyword(s):  
Relaxation Time ◽  
Oleic Acid ◽  
High Frequency ◽  
Cobalt Ferrite ◽  
Magnetic Moments ◽  
Relaxation Mechanism ◽  
Dynamic Susceptibility ◽  
Magnetite Particles ◽  
Magnetizing Field ◽  
Néel Relaxation

Measurements of the dynamic susceptibility of a magnetic fluid based on cobalt ferrite particles stabilized in water by a double surfactant layer have been carried out. Cobalt ferrite, in comparison with magnetite, has a significantly higher energy of magnetic anisotropy. Therefore, for particles of cobalt ferrite, the Brownian mechanism of relaxation of magnetic moments is characteristic. The Debye (with a finite relaxation time) contribution to the dynamic susceptibility and the high-frequency (dispersionless) contribution are distinguished by constructing Cole-Cole diagrams. It was found that with an increase in the magnetizing field, the Debye contribution to the dynamic susceptibility decreases, while the high-frequency one (having a zero relaxation time) remains unchanged. The indicated property of the dynamic susceptibility of a fluid with a Brownian relaxation mechanism is radically different from the properties of the susceptibility of a fluid with Néel particles. Previously, measurements were made of the susceptibility of a fluid based on magnetite particles stabilized with oleic acid in kerosene. The magnetite particles have significantly lower anisotropy energy and are characterized by the predominance of the Néel relaxation mechanism. Turning on the magnetizing field caused a decrease in both the Debye part of the susceptibility and the high-frequency part of the susceptibility of magnetite particles.

scholarly journals Role of zinc substitution in magnetic hyperthermia properties of magnetite nanoparticles: interplay between intrinsic properties and dipolar interactions

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Yaser Hadadian ◽  
Ana Paula Ramos ◽  
Theo Z. Pavan
Keyword(s):  
Magnetic Nanoparticles ◽  
Magnetite Nanoparticles ◽  
Linear Response Theory ◽  
Magnetic Hyperthermia ◽  
Superior Performance ◽  
Dipolar Interactions ◽  
Intrinsic Properties ◽  
Specific Loss ◽  
Heating Efficiency ◽  
Specific Loss Power

AbstractOptimizing the intrinsic properties of magnetic nanoparticles for magnetic hyperthermia is of considerable concern. In addition, the heating efficiency of the nanoparticles can be substantially influenced by dipolar interactions. Since adequate control of the intrinsic properties of magnetic nanoparticles is not straightforward, experimentally studying the complex interplay between these properties and dipolar interactions affecting the specific loss power can be challenging. Substituting zinc in magnetite structure is considered as an elegant approach to tune its properties. Here, we present experimental and numerical simulation results of magnetic hyperthermia studies using a series of zinc-substituted magnetite nanoparticles (ZnxFe1-xFe2O4, x = 0.0, 0.1, 0.2, 0.3 and 0.4). All experiments were conducted in linear regime and the results were inferred based on the numerical simulations conducted in the framework of the linear response theory. The results showed that depending on the nanoparticles intrinsic properties, interparticle interactions can have different effects on the specific loss power. When dipolar interactions were strong enough to affect the heating efficiency, the parameter σ = KeffV/kBT (Keff is the effective anisotropy and V the volume of the particles) determined the type of the effect. Finally, the sample x = 0.1 showed a superior performance with a relatively high intrinsic loss power 5.4 nHm2kg−1.

scholarly journals Computational Study Regarding CoxFe3−xO4 Ferrite Nanoparticles with Tunable Magnetic Properties in Superparamagnetic Hyperthermia for Effective Alternative Cancer Therapy

Nanomaterials ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 3294
Author(s):  
Costica Caizer
Keyword(s):  
Cancer Therapy ◽  
Computational Study ◽  
Tumor Therapy ◽  
Computational Simulation ◽  
Ferrite Nanoparticles ◽  
Specific Loss ◽  
Nanoparticle Diameter ◽  
Specific Loss Power ◽  
Wide Range ◽  
Range Of Values

The efficacy in superparamagnetic hyperthermia (SPMHT) and its effectiveness in destroying tumors without affecting healthy tissues depend very much on the nanoparticles used. Considering the results previously obtained in SPMHT using magnetite and cobalt ferrite nanoparticles, in this paper we extend our study on CoxFe3−xO4 nanoparticles for x = 0–1 in order to be used in SPMHT due to the multiple benefits in alternative cancer therapy. Due to the possibility of tuning the basic observables/parameters in SPMHT in a wide range of values by changing the concentration of Co2+ ions in the range 0–1, the issue explored by us is a very good strategy for increasing the efficiency and effectiveness of magnetic hyperthermia of tumors and reducing the toxicity levels. In this paper we studied by computational simulation the influence of Co2+ ion concentration in a very wide range of values (x = 0–1) on the specific loss power (Ps) in SPMHT and the nanoparticle diameter (DM) which leads to the maximum specific loss power (PsM). We also determined the maximum specific loss power for the allowable biological limit (PsM)l which doesn’t affect healthy tissues, and how it influences the change in the concentration of Co2+ ions. Based on the results obtained, we established the values for concentrations (x), nanoparticle diameter (DM), amplitude (H) and frequency (f) of the magnetic field for which SPMHT with CoxFe3−xO4 nanoparticles can be applied under optimal conditions within the allowable biological range. The obtained results allow the obtaining a maximum efficacy in alternative and non-invasive tumor therapy for the practical implementation of SPMHT with CoxFe3−xO4 nanoparticles.

scholarly journals Experimental Evaluation on the Heating Efficiency of Magnetoferritin Nanoparticles in an Alternating Magnetic Field

Nanomaterials ◽  
2019 ◽  
Vol 9 (10) ◽  
pp. 1457 ◽  
Author(s):  
Huangtao Xu ◽  
Yongxin Pan
Keyword(s):  
Magnetic Field ◽  
Relaxation Time ◽  
Magnetic Hyperthermia ◽  
Alternating Magnetic Field ◽  
Core Size ◽  
Hyperthermia Treatment ◽  
Field Frequency ◽  
Glycerol Water ◽  
Heating Efficiency ◽  
Néel Relaxation

The superparamagnetic substance magnetoferritin is a potential bio-nanomaterial for tumor magnetic hyperthermia because of its active tumor-targeting outer protein shell, uniform and tunable nanosized inner mineral core, monodispersity and good biocompatibility. Here, we evaluated the heating efficiency of magnetoferritin nanoparticles in an alternating magnetic field (AMF). The effects of core-size, Fe concentration, viscosity, and field frequency and amplitude were investigated. Under 805.5 kHz and 19.5 kA/m, temperature rise (ΔT) and specific loss power (SLP) measured on magnetoferritin nanoparticles with core size of 4.8 nm at 5 mg/mL were 14.2 °C (at 6 min) and 68.6 W/g, respectively. The SLP increased with core-size, Fe concentration, AMF frequency, and amplitude. Given that: (1) the SLP was insensitive to viscosity of glycerol-water solutions and (2) both the calculated effective relaxation time and the fitted relaxation time were closer to Néel relaxation time, we propose that the heating generation mechanism of magnetoferritin nanoparticles is dominated by the Néel relaxation. This work provides new insights into the heating efficiency of magnetoferritin and potential future applications for tumor magnetic hyperthermia treatment and heat-triggered drug release.

scholarly journals Quantitative Analysis of the Specific Absorption Rate Dependence on the Magnetic Field Strength in ZnxFe3−xO4 Nanoparticles

2020 ◽  
Vol 21 (20) ◽  
pp. 7775
Author(s):  
Mohamed Alae Ait Kerroum ◽  
Cristian Iacovita ◽  
Walid Baaziz ◽  
Dris Ihiawakrim ◽  
Guillaume Rogez ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Relaxation Time ◽  
Absorption Rate ◽  
Specific Absorption Rate ◽  
Large Diameter ◽  
Precipitation Method ◽  
Magnetization Relaxation ◽  
Specific Absorption ◽  
The Magnetic Field ◽  
Néel Relaxation

Superparamagnetic ZnxFe3−xO4 magnetic nanoparticles (0 ≤ x < 0.5) with spherical shapes of 16 nm average diameter and different zinc doping level have been successfully synthesized by co-precipitation method. The homogeneous zinc substitution of iron cations into the magnetite crystalline structure has led to an increase in the saturation magnetization of nanoparticles up to 120 Am2/kg for x ~ 0.3. The specific absorption rate (SAR) values increased considerably when x is varied between 0 and 0.3 and then decreased for x ~ 0.5. The SAR values are reduced upon the immobilization of the nanoparticles in a solid matrix being significantly increased by a pre-alignment step in a uniform static magnetic field before immobilization. The SAR values displayed a quadratic dependence on the alternating magnetic field amplitude (H) up to 35 kA/m. Above this value, a clear saturation effect of SAR was observed that was successfully described qualitatively and quantitatively by considering the non-linear field’s effects and the magnetic field dependence of both Brown and Neel relaxation times. The Neel relaxation time depends more steeply on H as compared with the Brown relaxation time, and the magnetization relaxation might be dominated by the Neel mechanism, even for nanoparticles with large diameter.

Sign in / Sign up

Export Citation Format

Share Document