High Specific Absorption Rate Research Articles

Engineering Gold Shelled Nanomagnets for Pre-Setting the Operating Temperature for Magnetic Hyperthermia.

This study investigated the fabrication of spherical gold shelled maghemite nanoparticles for use in magnetic hyperthermia (MHT) assays. A maghemite core (14 ± 3 nm) was used to fabricate two samples with different gold thicknesses, which presented gold (g)/maghemite (m) content ratios of 0.0376 and 0.0752. The samples were tested in MHT assays (temperature versus time) with varying frequencies (100–650 kHz) and field amplitudes (9–25 mT). The asymptotic temperatures () of the aqueous suspensions (40 mg Fe/mL) were found to be in the range of 59–77 °C (naked maghemite), 44–58 °C () and 33–51 °C (). The MHT data revealed that could be successful controlled using the gold thickness and cover the range for cell apoptosis, thereby providing a new strategy for the safe use of MHT in practice. The highest SAR (specific absorption rate) value was achieved (75 kW/kg) using the thinner gold shell layer (334 kHz, 17 mT) and was roughly twenty times bigger than the best SAR value that has been reported for similar structures. Moreover, the time that was required to achieve could be modeled by changing the thermal conductivity of the shell layer and/or the shape/size of the structure. The MHT assays were pioneeringly modeled using a derived equation that was analytically identical to the Box–Lucas method (which was reported as phenomenological).

Tetrahydroxyquinone: A Suitable Coating for Ferrofluids Used in Magnetic Hyperthermia

In this work, tetrahydroxyquinone (THQ) was used for the first time to coat iron oxide nanoparticles (IONPs) and to carry out in vitro experiments in magnetic hyperthermia. Synthesis by co-precipitation resulted in spherical IONPs with a core diameter of 13 ± 3 nm and covered by a 0.5 nm thick coat of THQ, which provided them with a reasonably good zeta potential of ζ = −28 ± 2 mV at pH = 7.3, and thus colloidal stability. The magnetic properties of the THQ-coated IONPs are promising: the low coercive field of Hc = 7 Oe, the high magnetic saturation of Ms = 70.5 emu/g and the low blocking temperature of Tb = 273 K indicate superparamagnetic characteristics at room temperature. Additionally, a high specific absorption rate SAR = 135 W/g (at 300 Oe and 530 kHz) was determined. Cell biological experiments using the human cell line HT-29 evidenced negligible cytotoxicity up to 2 mg/mL. Magnetic hyperthermia (MHT) assays demonstrated fast and reliable heating and reduced the metabolic activity of the cells to 42% upon reaching 42 °C within 15 min. The production of ROS by THQ-coated IONPs could not be detected, which may indicate a reduction in the undesired side effects caused by oxidative stress. Considering these good physicochemical and cell biological properties, this ferrofluid is a promising candidate for the initiation of in vivo experiments for cancer treatment by MHT in murine models.

A workflow for predicting temperature increase at the electrical contacts of deep brain stimulation electrodes undergoing MRI.

PurposeThe purpose of this study is to present a workflow for predicting the radiofrequency (RF) heating around the contacts of a deep brain stimulation (DBS) lead during an MRI scan.MethodsThe induced RF current on the DBS lead accumulates electric charge on the metallic contacts, which may cause a high local specific absorption rate (SAR), and therefore, heating. The accumulated charge was modeled by imposing a voltage boundary condition on the contacts in a quasi‐static electromagnetic (EM) simulation allowing thermal simulations to be performed with the resulting SAR distributions. Estimating SAR and temperature increases from a lead in vivo through EM simulation is not practical given anatomic differences and variations in lead geometry. To overcome this limitation, a new parameter, transimpedance, was defined to characterize a given lead. By combining the transimpedance, which can be measured in a single calibration scan, along with MR‐based current measurements of the lead in a unique orientation and anatomy, local heating can be estimated. Heating determined with this approach was compared with results from heating studies of a commercial DBS electrode in a gel phantom with different lead configurations to validate the proposed method.ResultsUsing data from a single calibration experiment, the transimpedance of a commercial DBS electrode (directional lead, Infinity DBS system, Abbott Laboratories, Chicago, IL) was determined to be 88 Ω. Heating predictions using the DBS transimpedance and rapidly acquired MR‐based current measurements in 26 different lead configurations resulted in a <23% (on average 11.3%) normalized root‐mean‐square error compared to experimental heating measurements during RF scans.ConclusionIn this study, a workflow consisting of an MR‐based current measurement on the DBS lead and simple quasi‐static EM/thermal simulations to predict the temperature increase around a DBS electrode undergoing an MRI scan is proposed and validated using a commercial DBS electrode.

Functionalized SPION immobilized on graphene-oxide: Anticancer and antiviral study

The progressive and fatal outbreak of some diseases such as cancer and coronavirus necessitates using advanced materials to bring such devastating illnesses under control. In this study, graphene oxide (GO) is decorated by superparamagnetic iron oxide nanoparticles (SPION) (GO/SPION) as well as polyethylene glycol functionalized SPION (GO/SPION@PEG), and chitosan functionalized SPION (GO/SPION@CS). Field emission scanning electron microscopic (FESEM) images show the formation of high density uniformly distributed SPION nanoparticles on the surface of GO sheets. The structural and chemical composition of nanostructures is confirmed by X-ray diffraction and Fourier transform infrared spectroscopy. The saturation magnetization of GO/SPION, GO/SPION@PEG and GO- SPION@CS are found to be 20, 19 and 8 emu/g using vibrating sample magnetometer. Specific absorption rate (SAR) values of 305, 283, and 199 W/g and corresponding intrinsic loss power (ILP) values of 9.4, 8.7, and 6.2 nHm2kg−1 are achieved for GO/SPION, GO/SPION@PEG and GO/SPION@CS, respectively. The In vitro cytotoxicity assay indicates higher than 70% cell viability for all nanostructures at 100, 300, and 500 ppm after 24 and 72 h. Additionally, cancerous cell (EJ138 human bladder carcinoma) ablation is observed using functionalized GO/SPION under applied magnetic field. More than 50% cancerous cell death has been achieved for GO/SPION@PEG at 300 ppm concentration. Furthermore, Surrogate virus neutralization test is applied to investigate neutralizing property of the synthesized nanostructures through analysis of SARS-CoV-2 receptor-binding domain and human angiotensin-converting enzyme 2 binding. The highest level of SARS-CoV-2 virus inhibition is related to GO/SPION@CS (86%) due to the synergistic exploitation of GO and chitosan. Thus, GO/SPION and GO/SPION@PEG with higher SAR and ILP values could be beneficial for cancer treatment, while GO/SPION@CS with higher virus suppression has potential to use against coronaviruses. Thus, the developed nanocomposites have a potential in the efficient treatment of cancer and coronavirus.

Design of a wideband patch antenna and performance enhancement using an AMC reflector surface for on-body communication at 2.45 GHz

ABSTRACT Wireless biotelemetry enables the formation of communication link from living body to an external monitoring device. Isolation of near field electromagnetic (EM) waves from body tissue, and wide bandwidth to avoid frequency detuning in different biological environments are the important parameters of on-body antennas. In this paper, a conformal defected ground patch antenna with artificial magnetic conductor (AMC) is introduced for on-body communication. Initially, a quarter wave wide band antenna with a shorting pin is designed to operate at 2.45 GHz. It resonates effectively on body tissue but most of the near field EM radiations are absorbed by tissue. Poor radiation efficiency of 10% and high specific absorption rate (SAR) value of 7.73 W/Kg were obtained. Thus, to reduce the effect of tissue loading on antenna performance an AMC-based structure is added. Better impedance matching, high efficiency (65%) and directivity (7.3 dBi) is achieved with AMC structure. Furthermore, unidirectional radiation pattern with SAR value of 1.43W/Kg is attained. Wide bandwidth of 600 MHz on phantom enables the antenna to withstand frequency detuning effect due to body postures and movements. Antenna robustness is analysed by bending the structure at different radii along X-axis and Y-axis.

SLOW: A novel spectral editing method for whole-brain MRSI at ultra high magnetic field.

PurposeAt ultra‐high field (UHF), B1 +‐inhomogeneities and high specific absorption rate (SAR) of adiabatic slice‐selective RF‐pulses make spatial resolved spectral‐editing extremely challenging with the conventional MEGA‐approach. The purpose of the study was to develop a whole‐brain resolved spectral‐editing MRSI at UHF (UHF, B 0 ≥ 7T) within clinical acceptable measurement‐time and minimal chemical‐shift‐displacement‐artifacts (CSDA) allowing for simultaneous GABA/Glx‐, 2HG‐, and PE‐editing on a clinical approved 7T‐scanner.MethodsSlice‐selective adiabatic refocusing RF‐pulses (2π‐SSAP) dominate the SAR to the patient in (semi)LASER based MEGA‐editing sequences, causing large CSDA and long measurement times to fulfill SAR requirements, even using SAR‐minimized GOIA‐pulses. Therefore, a novel type of spectral‐editing, called SLOW‐editing, using two different pairs of phase‐compensated chemical‐shift selective adiabatic refocusing‐pulses (2π‐CSAP) with different refocusing bandwidths were investigated to overcome these problems.ResultsCompared to conventional echo‐planar spectroscopic imaging (EPSI) and MEGA‐editing, SLOW‐editing shows robust refocusing and editing performance despite to B 1 + ‐inhomogeneity, and robustness to B 0‐inhomogeneities (0.2 ppm ≥ ΔB 0 ≥ −0.2 ppm). The narrow bandwidth (∼0.6–0.8 kHz) CSAP reduces the SAR by 92%, RF peak power by 84%, in‐excitation slab CSDA by 77%, and has no in‐plane CSDA. Furthermore, the CSAP implicitly dephases water, lipid and all the other signals outside of range (≥ 4.6 ppm and ≤1.4 ppm), resulting in additional water and lipid suppression (factors ≥ 1000s) at zero SAR‐cost, and no spectral aliasing artifacts.ConclusionA new spectral‐editing has been developed that is especially suitable for UHF, and was successfully applied for 2HG, GABA+, PE, and Glx‐editing within 10 min clinical acceptable measurement time.

CTAB assisted synthesis of MnFe2O4@ SiO2 nanoparticles for magnetic hyperthermia and MRI application

Magnetic fluid hyperthermia (MFH) has been proven as a promising cancer therapeutic approach in conjunction with chemotherapy or physiotherapy in patients. The research to find innovative materials with a higher specific absorption rate (SAR) to reduce the dose of magnetic nanoparticles in tumor treatment through MFH while being also adequate for Magnetic Resonance Imaging (MRI) is important. Herein, MnFe2O4 NPs were synthesized with different sizes, using NaOH or NH4OH as a reducing agent, via a green-assisted hydrothermal route. A tetraethyl orthosilicate with the assist of cetrimonium bromide was used to fabricate SiO2 @MnFe2O4 NPs. Based on the Mössbauer and XRD results an undesired amount of α-Fe2O3 was found in the samples synthesized with NH4OH. Concentration-dependent cellular toxicity values were evaluated by invitro 3-(4,5 dimethylthiazol-2-yl)−2,5-diphenyltetrazolium bromide (MTT) assay on A549 cells, where bare and silica coated nanoparticles exhibited non-toxicity below 691 µg/mL and 566 µg/mL, respectively. The ability of bare MnFe2O4 as the MRI contrast agent was higher compared to the silica-coated sample. The heating efficiency of the ferrofluids was recorded at 128 kHz and 10 kA/m and the highest SAR value was 39 W/g for the pristine MnFe2O4 NPs, making them promising potential materials in MRI and cancer treatment.

Towards optimal thermal distribution in magnetic hyperthermia

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 spherical magnetic nanocapsules consisting of metallic iron nanoparticles covered with non magnetic shells of sufficient thickness in magnetic hyperthermia. Based on numerical simulation we optimize the size and geometric structure of biocompatible spherical capsules in order to minimize the influence of strong magneto-dipole interaction between closely spaced nanoparticles. It is shown that assembly of capsules can provide sufficiently high SAR values of the order of 250–400 W/g at moderate amplitudes H0 = 50–100 Oe and frequencies f = 100–200 kHz of alternating magnetic field, being appropriate for application in clinics.

A Ferrofluid with High Specific Absorption Rate Prepared in a Single Step Using a Biopolymer.

An exhaustive characterization of the physicochemical properties of gum arabic (GA)-coated Fe3O4 magnetic nanoparticles was conducted in this work. These nanoparticles were obtained via the in-situ coprecipitation method (a fast single-step method) in two GA:Fe ratios, 10:1 and 20:1, respectively. Several experimental techniques were applied in the characterization process, all of them described below. Using Transmission Electron Microcopy images, they were shown to have spherical-like morphology with 11 nm diameter. The Fourier Transform Infrared spectra confirmed the attachment of the GA on the surface of the magnetic nanoparticles (MNPs), providing good colloidal stability from pH 7 to 8. The thickness of the coatings (1.7 nm and 1.1 nm) was determined using thermogravimetric measurements. A high specific absorption rate and superparamagnetic properties were determined using alternant and static magnetic fields, respectively. The GA-coated MNPs were non-cytotoxic, according to tests on HT-29 human intestine cells. Additionally, HT-29 cells were exposed to magnetic fluid hyperthermia at 530 kHz, and the induction of cell death by the magnetic field, due to the heating of GA-coated MNP, was observed.

Smart Magnetic Nanocarriers for Multi-Stimuli On-Demand Drug Delivery

In this study, we report the realization of drug-loaded smart magnetic nanocarriers constituted by superparamagnetic iron oxide nanoparticles encapsulated in a dual pH- and temperature-responsive poly (N-vinylcaprolactam-co-acrylic acid) copolymer to achieve highly controlled drug release and localized magnetic hyperthermia. The magnetic core was constituted by flower-like magnetite nanoparticles with a size of 16.4 nm prepared by the polyol approach, with good saturation magnetization and a high specific absorption rate. The core was encapsulated in poly (N-vinylcaprolactam-co-acrylic acid) obtaining magnetic nanocarriers that revealed reversible hydration/dehydration transition at the acidic condition and/or at temperatures above physiological body temperature, which can be triggered by magnetic hyperthermia. The efficacy of the system was proved by loading doxorubicin with very high encapsulation efficiency (>96.0%) at neutral pH. The double pH- and temperature-responsive nature of the magnetic nanocarriers facilitated a burst, almost complete release of the drug at acidic pH under hyperthermia conditions, while a negligible amount of doxorubicin was released at physiological body temperature at neutral pH, confirming that in addition to pH variation, drug release can be improved by hyperthermia treatment. These results suggest this multi-stimuli-sensitive nanoplatform is a promising candidate for remote-controlled drug release in combination with magnetic hyperthermia for cancer treatment.

Eco-friendly synthesis of cobalt-zinc ferrites using quince extract for adsorption and catalytic applications: An approach towards environmental remediation

Cobalt-zinc ferrite nanoparticles were synthesized using environmentally friendly approach with quince extract as a reducing agent. Crystal structure and morphology of the obtained materials were studied by XRD, SEM-EDS, Mössbauer and IR spectroscopy. The synthesized nanoparticles have a cubic spinel structure and crystallite size ranging from 5 to 9 nm. The infrared spectra contain characteristic absorption bands for the MA-O (∼560 cm−1) and MB-O bonds (∼420 cm−1). Force constants were calculated for both tetrahedral and octahedral bonds. As the Co content increases, the force constant for the tetrahedral bond increases and the force constant for the octahedral bond decreases. The obtained ferrite nanoparticles have good magnetization as shown by VSM (in the range from 36 to 67 emu/g). Magnetic nanoparticles CoxZn1-xFe2O4 were also tested for induction heating with electromagnetic field. The sample with x (Co) = 0.4 has the highest specific absorption rate. The synthesized samples were tested as adsorbents using the Congo Red dye as model pollutant. The best adsorbent was pure zinc ferrite with the adsorption capacity of 24.7 mg/g. The catalytic activity of the obtained ferrites for the decomposition of H2O2 was studied as well. The most active catalyst was pure cobalt ferrite. Probably, the active centers are octahedral cobalt ions. Thus, the obtained magnetic nanoparticles can be used for the adsorptive removal of pollutants, catalytic decomposition of the H2O2 and low-frequency hyperthermia.

Comparison of the influence of superparamagnetic nanoparticles concentration and coverage on the alternating magnetic field thermal effect

Magnetic nanoparticles (MNP)s of Fe3O4 were synthesized in the co-precipitation reaction of iron chlorides dissolved in water and ammonia water. To produce polyethylene glycol (PEG) coatings of the NMPs, we added PEG to the ammonia water during the fabrication process. Magnetic fluids, ferrofluids, for research were prepared as oleic acid suspension of bare and PEG-coated nanoparticles at four concentrations. The results of the conducted calorimetric experiments confirmed that the efficiency of heating ferrofluids strongly depends on the concentration of nanoparticles in fluids. The results also indicate that the ferrofluids containing PEG-coated NPs heat up more than ferrofluids with bare nanoparticles. They are characterized by a higher specific absorption rate (SAR) value calculated from the initial slope of temperature versus time curve during heating.

Structure and properties of Co-=SUB=-x-=/SUB=-Mn-=SUB=-1-x-=/SUB=-Fe-=SUB=-2-=/SUB=-O-=SUB=-4-=/SUB=- nanoparticles depending on the amount of Co ions (0≤ x≤ 1.0)

The properties of magnetic nanoparticles (MNPs) of spinel ferrites CoxMn1-xFe2O4 (at x=0.0; 0.2; 0.3; 0.4; 0.5; 0.6; 0.8; 1.0) synthesized by chemical co-precipitation method have been studied. The studies of the synthesized CoxMn1-xFe2O4 MNPs were carried out using X-ray diffraction (XRD), Raman scattering and Mossbauer spectroscopy. The results of XRD, Raman and Mossbaur studies indicate that the obtained CoxMn1-xFe2O4 MNPs are single-phase. It was established from XRD measurements that the average size of CoxMn1-xFe2O4 crystallites is 34.86 nm for MnFe2O4 (x=0) and decreases to 14.99 nm for CoFe2O4 (x=1.0) with increasing Co ions concentration. An analysis of the Mossbaur spectra showed that the average crystallite size varies from 25 nm for MnFe2O4 (x=0) to 12 nm for CoFe2O4 (x=1.0). On the Raman spectra of CoxMn1-xFe2O4 MNPs, in the region of ~620 cm-1, splitting of the A1g line is observed, which means that the studied MNPs have a reverse spinel structure. The intensity ratio of the A1g (1) and A1g (2) peaks indicates a significant redistribution of the Co2+ and Fe3+ cations between tetra- and octahedralpositions in MNPs of the CoxMn1-xFe2O4 ferrite, which is confirmed by Mossbauer data. Mossbaur spectroscopy data indicate that the synthesized CoxMn1-xFe2O4 MNPs consist of large particles with magnetic ordering and small particles in the paramagnetic phase. With an increase in the concentration of Mn ions, the proportion of fine particles increases, which leads to a decrease in the magnetic blocking temperature. The saturation magnetization of MNPs at x=0.2 (Co0.2Mn0.8Fe2O4) is 57.41 emu/g and this sample, as was found in [V. Narayanaswamy, I.A. Al-Omari, A.S. Kamzin, B. Issa, H.O. Tekin, H. Khourshid, H. Kumar, A. Mallya, S. Sambasivam, I.M. Obaidat. Nanomaterials 11, 1231 (2021)] has the highest specific absorption rate. As shown by Mossbauer studies, this is due to the fact that these particles are in a superparamagnetic state and the magnetic blocking temperature of these MNPs is in the region of ~315 K, which is most suitable for the treatment of malignant tumors by magnetic hyperthermia. Thus, the synthesized CoxMn1-xFe2O4 MNPs are promising for biomedical applications. Keywords: spinel ferrites CoxMn1-xFe2O4, magnetic structure, superparamagnetism, Mossbauer spectroscopy, materials for biomedicine.

Analysis of a Flexible Dual-Channel Octagonal Coil System for UHF MRI

Nowadays, MRI is focused on using ultra-high static magnetic fields (> 7 T) to increase the signal-to-noise ratio. The use of high fields, on the other hand, requires novel technical solutions as well as more stringent design criteria for specific absorption rate levels, reducing radiative effect and coil resistance. In this paper, two flexible RF coils for 7 T human magnetic resonance, and 298 MHz ultra-high frequency operations were analyzed and characterized. Imaging of lower human limbs is regarded as a case study. The lumped element theory and subsequent numerical simulations were used to fine-tune the single-coil element and the dual-coil array design, respectively. Here, we demonstrate how the shape, size, configuration, and presence of the sample influence the coil performance. The penetration depth of the B <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> -field and the specific absorption rate values have been determined numerically using two numerical surface phantoms: saline and a multilayer human tissue. A preliminary study in the presence of a saline solution phantom has been carried out to develop and validate the dual-coil system. The frequency response of the dual-coil array was measured to assess its robustness when coupled to twelve human volunteers. We found that our design is robust to variations in the anatomical properties of the human thighs, and hence to coil bending. The presented approach can be useful for the implementation of flexible devices with high sensitivity levels and low specific absorption rate.

DESIGN OF COMPOSITE NANO INK BASED WEARABLE ANTENNA FOR E-TEXTILE APPLICATIONS

This paper presents a design of composite nano ink based wearable antenna for e-textile applications. Wearable antenna is designed to function while being worn. It is commonly used in wearable wireless communication and biomedical systems. For this study we are using HFSS (High Frequency Structure Simulator) software tool cotton is as substrate with permittivity and loss tangent 1.6mm and 0.02 respectively. For improvement of high gain and low SAR (Specific Absorption Rate) we are using EBG(Electromagnetic Bandgap) &amp; VIA techniques.

Analysis of specific absorption rate and heat transfer in human head due to mobile phones

The human body absorbs a particular proportion of radiation when introduced to an electromagnetic field. The proportion of radio repeat energy burned-through in a unit mass of a human body when introduced to a radio frequency electromagnetic field is known as the Specific Absorption Rate and is alluded to as SAR. The position and bearing of the human body concerning the wellspring of the radiation impact the SAR regard. The sort of wellspring of the RF energy moreover impacts the SAR regard. This paper-based on how Mobile phones and there are arranged while simultaneously using them contribute and impact the value of SAR. Moreover, it is seen that SAR contributed by mobile phones is higher than other RF sources like Bluetooth and Wi-Fi Devices. This is a result of the way that the yield power transmitted by cells is higher than Bluetooth and Wi-Fi contraptions. As SAR is the proportion of electromagnetic power held over a specific volume of tissue, it is directly comparative with the strength of the electromagnetic field. Consequently, cells have higher Specific Absorption Rates when diverged from Bluetooth and Wi-Fi devices. SAR spatially shows up at the midpoint of over 1 g or 10 g of human tissue. Maxwell's field conditions in time–space are used to register the SAR movement in the human head. Charged particles gain energy and falter when electromagnetic radiation is the event on the issue. The energy gained could either be immediately reradiated and appear as scattered, reflected, or sent radiation or it may get into minuscule developments inside the matter, accomplishing warm concordance and setting out a decent establishment for itself as atomic power in the material. Temperature assessed over 1 g of tissue is higher when appeared differently in relation to 10 g volume of tissue. Muscle and blood have the temperature rise lower than the skin on account of skin significance. It is seen that when the significance of invasion grows SAR reduction and thusly temperature lessens.

Using kinetic Monte Carlo simulations to design efficient magnetic nanoparticles for clinical hyperthermia.

The purpose of this study was to identify the properties of magnetite nanoparticles that deliver optimal heating efficiency, predict the geometrical characteristics to get these target properties, and determine the concentrations of nanoparticles required to optimize thermotherapy. Kinetic Monte Carlo simulations were employed to identify the properties of magnetic nanoparticles that deliver high Specific Absorption Rate (SAR) values. Optimal volumes were determined for anisotropies ranging between 11 and 40kJ/m3 under clinically relevant magnetic field conditions. Atomistic spin simulations were employed to determine the aspect ratios of ellipsoidal magnetite nanoparticles that deliver the target properties. A numerical model was developed using the extended cardiac-torso (XCAT) phantom to simulate low-field (4 kA/m) and high-field (18 kA/m) prostate cancer thermotherapy. A stationary optimization study exploiting the Method of Moving Asymptotes (MMA) was carried out to calculate the concentration fields that deliver homogenous temperature distributions within target thermotherapy range constrained by the optimization objective function. A time-dependent study was used to compute the thermal dose of a 30-min session. Prolate ellipsoidal magnetite nanoparticles with a volume of 3922 ± 35 nm3 and aspect ratio of 1.56, which yields an effective anisotropy of 20kJ/m3 , constituted the optimal design at current maximum clinical field properties (H0 =18 kA/m, f=100kHz), with SAR=342.0 ± 2.7 W/g, while nanoparticles with a volume of 4147 ± 36 nm3 , aspect ratio of 1.29, and effective anisotropy 11kJ/m3 were optimal for low-field applications (H0 =4 kA/m, f=100kHz), with SAR=50.2 ± 0.5 W/g. The average concentration of 3.86 ± 0.10 and 0.57 ± 0.01mg/cm3 at 4 and 18 kA/m, respectively, were sufficient to reach therapeutic temperatures of 42-44°C throughout the prostate volume. The thermal dose delivered during a 30-min session exceeded 5.8 Cumulative Equivalent Minutes at 43°C within 90% of the prostate volume (CEM43T90 ). The optimal properties and design specifications of magnetite nanoparticles vary with magnetic field properties. Application-specific magnetic nanoparticles or nanoparticles that are optimized at low fields are indicated for optimal thermal dose delivery at low concentrations.

Comparison of SAR distribution of hip and knee implantable devices in 1.5T conventional cylindrical-bore and 1.2T open-bore vertical MRI systems.

There is increasing use of open-bore vertical MR systems that consist of two planar RF coils. A recent study showed that the RF-induced heating of a neuromodulation device was much lower in the open-bore system at the brain and the chest imaging landmarks. This study focused on the hip and knee implants and compared the specific absorption rate (SAR) distribution in human models in a 1.2T open-bore coil with that of a 1.5T conventional birdcage coil. Computational modeling results were compared against the measurement values using a saline phantom. The differences in RF exposure were examined between a 1.2T open-bore coil and a 1.5T conventional birdcage coil using SAR in an anatomical human model. Modeling setups were validated. The body placed closed to the coil elements led to high SAR values in the birdcage system compared with the open-bore system. Our computational modeling showed that the 1.2T planar system demonstrated a lower intensity of SAR distribution adjacent to hip and knee implants compared with the 1.5T conventional birdcage system.

Synthesis, characterization and heating efficiency of Gd-doped maghemite (γ-Fe2O3) nanoparticles for hyperthermia application

In this paper, sol-gel technique was used to prepare Gd-doped γ-Fe2O3 nanoparticles and their heating efficiency for magnetic hyperthermia application was investigated. The obtained nanoparticles are characterized by several techniques. The structural properties are performed by X-ray diffraction (XRD), energy-dispersive X-ray spectrometer (EDAX) and X-ray Photoelectron Spectroscopy (XPS), while the morphology is investigated by Transmission electron microscopy (TEM). The magnetic properties and heating ability under an alternating magnetic field are performed by vibrating sample magnetometer (VSM) and magnetherm respectively. XRD, XPS and TEM results confirmed the maghemite (γ-Fe2O3) phase, the presence of Gd ions and crystallinity. VSM hysteresis loops showed a negligible coercive field and remanence suggesting superparamagnetic behavior, which was also confirmed by Langevin method. Heating efficiency under an AC alternating magnetic field measurements showed that doped and un-doped samples display high heating ability and reached magnetic hyperthermia (42 °C) in relatively short times with shorter time (∼2 min) observed for γ-Fe2O3 compared to 6 min for Gd (5%) doped γ-Fe2O3 nanoparticles. The specific absorption rate (SAR) values decreased with increased concentration of Gd but remain considerable for all doped samples (up to 40W/g for Gd (5%)). The high crystallinity, superparamagnetic behavior and good SARs values make these nanoparticles a promising candidate for hyperthermia application.

Magnetically triggered release of active TGF-B from spin vortex microdiscs

Transforming Growth Factor-β (TGF-β) has been implicated in a variety of cellular functions, including control of cell cycle, cell proliferation, extracellular matrix formation, and even stem cell differentiation. TGF-β is also a contributor for combinatorial cellular responses, including cellular senescence, cellular apoptosis, and tumor progression. As a result, spatial and temporal control of TGF-β delivery has the potential to lead to greater control over cell signaling while minimizing the potential for undesirable off-target effects. We recently reported magnetically triggered release of active TGF-β from TGF-β Latent Complex conjugated to high-specific absorption rate (SAR) magnetic nanoparticles via magnetic hyperthermia; here we redirected our approach to spin vortex discs. Planar, gold-coated Permalloy (Ni80Fe20) microdiscs (∼2.0 µm diameter, 70 nm thick) were fabricated via standard lithography techniques and thin-film deposition. The discs were then bioconjugated with latent TGF-β via gold-thiol conjugation chemistry, and shear stress on the attached latent TGF-β was induced via magnetic actuation of the discs. This magnetic actuation was achieved via application of a spatially uniform dual pulsating magnetic field (∼1 mT) using two perpendicular pairs of Helmholtz coils at a frequency of 20 Hz for 1 h. Preliminary results of the bioconjugated discs shown here indicate a significant increase in the release of active TGF-β compared to the baseline passive release. Further studies will focus on investigating non-invasive remote activation and direction of TGF-β by a magnetic field, as well as investigating the potential of expanding this work to other growth factors that exist in latent and active forms.