High Specific Absorption Rate Research Articles

Magnetohyperthermia-synergistic glioma cancer therapy enabled by magnetic graphene oxide nanoheaters: promising nanostructure for in vitro and in vivo applications

In the present study, a magnetohyperthermia (MH)-based therapy is introduced as an effective treatment for deep-seated tumors especially glioma, which combines the magnetothermal effect and the reactive oxygen species (ROS) induced with magnetic graphene oxide (GOMNPs) nanoheaters to overcome the issue of limited therapeutic efficacy in the current magnetothermal therapeutic strategy. Magnetic graphene oxide nanoheaters with a size of 34 nm and a surface charge of − 35 mV showed very little toxicity under in vitro and ex vivo circumstances based on MTT and hemolysis assay, respectively. The application of GOMNPs under an alternating magnetic coil (AMC) showed that they had high specific absorption rate (SAR, P < 0.01), with enhanced level of ROS production within the tumor microenvironment. The results confirmed a significant increase in the SAR in blood compared to culture media (P < 0.01), which indicates the improvement of magnetohyperthermia performance in in vivo conditions compared to in vitro. A significant therapeutic efficacy was achieved with a dosage of 30 mg/kg of GOMNPs following 3 therapeutic courses under alternating magnetic field (AMF) compared to AMF alone (P < 0.05). GOMNPs exhibited a strong anti-glioma effect by inhibiting tumor growth, and increasing the survival ratio by inducing apoptotic cell death (P < 0.05). The Bax/Bcl2 protein and gene ratio confirmed a higher rate of apoptotic death in the MH-treated group (P < 0.05). Combination of magnetohyperthermia with conventional modalities may offer tremendous clinical advantages compared to the currently available methods.Graphical

A miniaturized uniplanar MIMO antenna for n79/n46/millimeter‐wave applications

SummaryThis research suggests a compact uniplanar multiple‐input multiple‐output (MIMO) with four ports for n79/n46/millimeter‐wave (mm‐wave) applications. The size of the quad MIMO is only 30 × 30 × 0.8 mm3. MIMO system consists of four identical Z‐shaped radiators and common ground on the same plane and no decoupling structures are used for isolation. The system covers the bandwidth of 1.9 GHz (4.4–6.3 GHz) with a mid‐frequency of 5.6 GHz and also covers the high‐band frequencies ranging from 18 to 30 GHz with a bandwidth of 12 GHz. The suggested quad MIMO is fabricated on an FR‐4 board, and the measured outcomes are well in line with the simulated results. An isolation value of −11 dB has been achieved for mid‐band frequency and −24 dB has been attained for mm‐wave bands. Through the value of DG = 10 dB, ECC &lt; 0.07, TARC &lt; −3 dB, MEG &lt; −5 dB, and the ratio of MEG = 1 dB, uniplanar quad MIMO shows acceptable MIMO diversity performance. The entire system was evaluated for the users' hand specific absorption rate (SAR) impacts and is within the limits. After the complete analysis of the miniature quad MIMO antenna, an 8‐port, and a 16‐port uniplanar MIMO are simulated for smartphone‐sized dielectric substrates and the performances were examined. The suggested MIMO system provides an efficient single‐layer MIMO antenna to 5G smartphones with high bandwidth and low SAR. The proposed quad MIMO systems are suitable for both the sub‐6 GHz band and the mm‐wave band.

Specific absorption rate (SAR) simulations for low-field (< 0.1 T) MRI systems

ObjectiveTo simulate the magnetic and electric fields produced by RF coil geometries commonly used at low field. Based on these simulations, the specific absorption rate (SAR) efficiency can be derived to ensure safe operation even when using short RF pulses and high duty cycles.MethodsElectromagnetic simulations were performed at four different field strengths between 0.05 and 0.1 T, corresponding to the lower and upper limits of current point-of-care (POC) neuroimaging systems. Transmit magnetic and electric fields, as well as transmit efficiency and SAR efficiency were simulated. The effects of a close-fitting shield on the EM fields were also assessed. SAR calculations were performed as a function of RF pulse length in turbo-spin echo (TSE) sequences.ResultsSimulations of RF coil characteristics and B1+ transmit efficiencies agreed well with corresponding experimentally determined parameters. Overall, the SAR efficiency was, as expected, higher at the lower frequencies studied, and many orders of magnitude greater than at conventional clinical field strengths. The tight-fitting transmit coil results in the highest SAR in the nose and skull, which are not thermally sensitive tissues. The calculated SAR efficiencies showed that only when 180° refocusing pulses of duration ~ 10 ms are used for TSE sequences does SAR need to be carefully considered.ConclusionThis work presents a comprehensive overview of the transmit and SAR efficiencies for RF coils used for POC MRI neuroimaging. While SAR is not a problem for conventional sequences, the values derived here should be useful for RF intensive sequences such as T1ρ, and also demonstrate that if very short RF pulses are required then SAR calculations should be performed.

Magnetic hyperthermia of AFe2O4 (A = Fe, Mn, Co) nanoparticles prepared by Co-precipitation method

With 10 million deaths in 2020 cancer remains one of the most challenging diseases in contemporary medicine. Chemotherapy, surgery, and radiation therapy are commonly used to treat tumors. These treatments harm healthy tissues and succeed rarely in advance stages of cancer. Recent studies indicate that magnetic hyperthermia, which involves targeted delivery of magnetic nanoparticles to tumor cells followed by localized remote heating of cancer tissues could revolutionize clinical practice in the treatment of cancer, either as standalone intervention or adjunct to radiotherapy and chemotherapy. Water dispersible magnetic nanoparticles (MNPs) of ferrites (AFe2O4; A = Fe, Mn, Co) are the promising candidates for magnetic hyperthermia due to their high chemical stability, biocompatibility, moderate magnetization and high specific absorption rates (SAR). In this article, we have evaluated magnetic hyperthermia efficiency of water based magnetic fluids of AFe2O4. AFe2O4 NPs were synthesized by chemical co-precipitation method. Nanoparticles were coated with a bilayer of oleic acid and dispersed in water. Structural and magnetic properties of MNPs were investigated by X-Ray diffraction (XRD) and vibrating sample magnetometer (VSM). XRD study revealed that AFe2O4 NPs exhibits cubic inverse spinel structure. Fe3O4 (Ms = 48 emu/g, Mr = 2.60 emu/g, Hc = 49 Oe), MnFe2O4 (Ms = 40 emu/g, Mr = 2.60 emu/g, Hc = 35 Oe) and CoFe2O4 (44 emu/g, Mr = 10.10 emu/g, Hc =440 Oe) NPs exhibits soft ferromagnetic behaviour. Magnetic hyperthermia measurements were performed as a function of magnetic field strength (2–10 mT), field frequency (162–935.6 kHz) for 10 minutes. MNPs exhibits highest SAR values for 10 mT field strength at 935.6 kHz. Amongst the tested MNPs, Fe3O4 possess the highest SAR value (27.35 W/g), followed by MnFe2O4 (1.91 W/g) and CoFe2O4 (0.94 W/g). Considering this, it is concluded that amongst the inverse spinel ferrites AFe2O4, Fe3O4 NPs and most suitable for magnetic hyperthermia applications.

Comparative analysis of cobalt ferrite and iron oxide nanoparticles using bimodal hyperthermia, along with physical and in silico interaction with human hemoglobin.

Magnetic nanoparticles (MNPs) have captivated the scientific community towards biomedical applications owing to their numerous distinctive physio-chemical properties. In this work, cobalt ferrite (CFNPs) and iron oxide nanoparticles (IONPs) were synthesized using the thermal decomposition method and then functionalized with polyacrylic acid (PAA) for aqueous dispersion. Associated techniques, namely TEM, FESEM, DLS, XRD, and VSM, were used to characterize the synthesized nanoparticles. We also investigated the light-induced and magnetic-field-induced hyperthermia properties of the PAA-functionalized MNPs. It was found that the PAA-CFNPs show a high specific absorption rate (SAR) compared with the PAA-IONPs. Since blood plasma is essential for the delivery and targeting of drugs, studying biological interactions is crucial for effective therapeutic use. Therefore, we performed physical and in silico studies to probe into the mechanistic interaction of CFNPs and IONPs with human hemoglobin. From these studies, we inferred the successful binding between the nanoparticles and protein. Preliminary in vitro cytocompatibility and photothermal toxicity studies in breast cancer (MCF-7) cells treated with the nanoparticles revealed a low dark toxicity and significant laser-induced photothermal toxicity.

Numerical Modeling and Computer Simulation of a Meander Line Antenna for Alzheimer's Disease Treatment, a Feasibility Study.

Alzheimer's disease (AD) is a brain disorder that eventually causes memory loss and the ability to perform simple cognitive functions; research efforts within pharmaceuticals and other medical treatments have minimal impact on the disease. Our preliminary biological studies showed that Repeated Electromagnetic Field Stimulation (REFMS) applying an EM frequency of 64 MHz and a specific absorption rate (SAR) of 0.4 - 0.9 W/kg decrease the level of amyloid-β peptides (Aβ), which is the most likely etiology of AD. This study emphasizes uniform E/H field and SAR distribution with adequate penetration depth penetration through multiple human head layers driven with low input power for safety treatments. In this work, we performed numerical modeling and computer simulations of a portable Meander Line antenna (MLA) to achieve the required EMF parameters to treat AD. The MLA device features a low cost, small size, wide bandwidth, and the ability to integrate into a portable system. This study utilized a High-Frequency Simulation System (HFSS) in the design of the MLA with the desired characteristics suited for AD treatment in humans. The team designed a 24-turn antenna with a 60 cm length and 25 cm width and achieved the required resonant frequency of 64 MHz. Here we used two numerical human head phantoms to test the antenna, the MIDA and spherical head phantom with six and seven tissue layers, respectively. The antenna was fed from a 50-Watt input source to obtain the SAR of 0.6 W/kg requirement in the center of the simulated brain tissue layer. We found that the E/H field and SAR distribution produced was not homogeneous; there were areas of high SAR values close to the antenna transmitter, also areas of low SAR value far away from the antenna. This paper details the antenna parameters, the scattering parameters response, the efficiency response, and the E and H field distribution; we presented the computer simulation results and discussed future work for a practical model.

Heatable magnetic nanocomposites with Fe3O4 nanocubes

<h2>Abstract</h2> The development of magnetic self-heating polymers is an area of great interest for many applications. The intrinsic magnetic properties of the magnetic fillers play a key role in the final heating capability of these nanocomposites. Thus, it has been already reported the improvement of the heating efficiency on Fe₃O₄ magnetic nanocubes with respect to spherical nanoparticles with the similar mean size¹. This result is due to the contribution of the magnetic anisotropy giving rise to higher magnetic coercivity and as consequence, higher SAR (Specific Absorption Rate) values. In this work, well- defined Fe₃O₄ nanocubes were synthesized through thermal decomposition processes with a mean particle diameter around 70 nm (TEM) (Fig. 1). The SAR values were estimated through the measurement of the AC hysteresis loops, obtaining values of around 900 W/g for the dispersion of the nanocubes in water and values of 350 W/g for the nanocubes dispersed in agar (0.5% wt), with a frequency of 403 kHz and a field amplitude of 30kA/m . In this case, the decrease of the SAR values is due to the inmovilization of the particles in the medium and hence, the Brownian movement of the particles. The temperature increase was also characterized, where a clear enhancement of the heating properties was obtained for nanocubes comparing with spherical nanoparticles of similar mean diameter (Fig. 2). Finally, the heating capacity of the nanocomposites (30% weight of magnetic nanoparticles) was studied through the application of an external AC magnetic field with a Helmholtz coil (319 kHz, 400A, 200G approximately, induction equipment model EasyHeat Ambrell). The effect of the thickness of the polymeric discs on the final temperature achieved was studied (2 and 4 mm thickness and 30 mm diameter). Thus, temperatures of 100 °C or 250 °C were reached after 2 min for the nanocomposites with thicknesses of 2 and 4 mm respectively.

The hot-to-cold spot quotient for SAR-based treatment planning in deep microwave hyperthermia

Background A necessary precondition for a successful microwave hyperthermia (HT) treatment delivered by phased arrays is the ability of the HT applicator to selectively raise the temperature of the entire tumor volume. SAR-based treatment plan (HTP) optimization methods exploit the correlation between specific absorption rate (SAR) and temperature increase in order to determine the set of steering parameters for optimal focusing, while allowing for lower model complexity. Several cost functions have been suggested in the past for this optimization problem. However, their correlation with high and homogeneous tumor temperatures remains sub-optimal in many cases. Previously, we proposed the hot-to-cold spot quotient (HCQ) as a novel cost function for SAR-based HTP optimization and showed its potential to address these issues. Materials and methods In this work, we validate the HCQ on a standard ESHO patient repository within single and multi-frequency contexts. We verify its correlation with clinical SAR and temperature indexes, and compare it to HTPs obtained using a commonly accepted cost-function for SAR-based HTP (hot-spot to target quotient, HTQ). Results and discussion The results show that low HCQ values produce better SAR (TC50, TC75) and temperature metrics (T50, T90) than HTQ in most patient models and frequency settings. For the deep-seated tumors, the correlation between the clinical indicators and 1/HCQ is more favorable than the correlation exhibited by 1/HTQ. Conclusion The validation confirms the ability of HCQ to promote target coverage and hot-spot suppression in SAR-based HTP optimization, resulting in higher SAR and temperature indexes for deep-seated tumors.

Interfacial engineered iron oxide nanoring for T2-weighted magnetic resonance imaging-guided magnetothermal-chemotherapy.

Due to no penetration depth limitation, low cost, and easy control, magnetic nanoparticles mediated magnetic hyperthermia therapy (MHT) has shown great potential in experimental and clinal treatments of various diseases. However, the low heating conversion efficiencies and short circulation times are major drawback for most existing magnetic-thermal materials. Additionally, single MHT treatment always leads to resistance and recurrence. Herein, a highly efficient magnetic-thermal conversion, ferrimagnetic vortex nanoring Fe3O4 coated with hyaluronic acid (HA) nanoparticles (Fe3O4@HA, FVNH NPs) was firstly constructed. Additionally, the doxorubicin (DOX) was successfully enclosed inside the FVNH and released remotely for synergetic magnetic–thermal/chemo cancer therapy. Due to the ferrimagnetic vortex-domain state, the ring shape Fe3O4 displays a high specific absorption rate (SAR) under an external alternating magnetic field (AMF). Additionally, antitumor drug (DOX) can be encapsulated inside the single large hole of FVNH by the hyaluronic acid (HA) shell and quickly released in response the tumor acidic microenvironments and AMF. What’s more, the non-loaded FVNH NPs show good biocompatibility but high cytotoxicity after loading DOX under AMF. Furthermore, the synthesized FVNH can efficiently reduce the transverse relaxation time and enhance negative magnetic resonance imaging (MRI). The impressive in vivo systemic therapeutic efficacy of FVNH was also proved in this work. Taken together, the results of this study demonstrate that the synthesized FVNH NPs offer the promise of serving as multifunctional theranostic nanoplatforms for medical imaging-guided tumor therapies.

Clinical application of ultra-high resolution compressed sensing time-of-flight MR angiography at 7T to detect small vessel pathology.

3D time-of-flight (TOF) MR angiography (MRA) benefits from ultra-high-field MRI (≥7T) due to improved contrast and increased signal-to-noise ratio. However, high-resolution TOF MRA at 7T usually requires longer acquisition times. In addition, relatively higher specific absorption rate (SAR) at 7T limits the choice of optimal pulse sequence parameters, especially if venous saturation is employed. Here, we illustrate the clinical application of ultra-high resolution cerebral 7T TOF MRA using compressed sensing in cases of artery of Percheron and lacunar infarcts, which showed superior resolution and exquisite details pertinent to the clinical diagnosis. The technical challenges associated with high-resolution 7T imaging were alleviated by optimization of sequence parameters and utilization of compressed sensing acceleration.

Road User Exposure from ITS-5.9 GHz Vehicular Connectivity.

This study addressed an important but not yet thoroughly investigated topic regarding human exposure to radio-frequency electromagnetic fields (RF-EMF) generated by vehicular connectivity. In particular, the study assessed, by means of computational dosimetry, the RF-EMF exposure in road users near a car equipped with vehicle-to-vehicle (V2V) communication antennas. The exposure scenario consisted of a 3D numerical model of a car with two V2V antennas, each fed with 1 W, operating at 5.9 GHz and an adult human model to simulate the road user near the car. The RF-EMF dose absorbed by the human model was calculated as the specific absorption rate (SAR), that is, the RF-EMF power absorbed per unit of mass. The highest SAR was observed in the skin of the head (34.7 mW/kg) and in the eyes (15 mW/kg); the SAR at the torso (including the genitals) and limbs was negligible or much lower than in the head and eyes. The SAR over the whole body was 0.19 mW/kg. The SAR was always well below the limits of human exposure in the 100 kHz–6 GHz band established by the International Commission on Non-Ionizing Radiation Protection (ICNIRP). The proposed approach can be generalized to assess RF-EMF exposure in different conditions by varying the montage/number of V2V antennas and considering human models of different ages.

Analysis of mobile phone radiation effect on human body using specific absorption rate

The use of mobile phones is rising everyday both in civic and rustic areas in Bangladesh. Every mobile phone disperses electromagnetic energy. This radiation or electromagnetic wave can penetrate into the human body. Specific absorption rate and change in temperature are the vital parameter to find the dominant effects assess on the human body. This paper explores the radiation impact of mobile phones. A mathematical equation is used to evaluate the local specific absorption rate and change in temperature at Skin, Fat, Bone, Brain, Eye, Muscle tissues at the frequency of 800MHz, 900 MHz, 1800 MHz, 2100 MHz, 2.5GHz, 2.6GHz, 3.4GHz, 3.5GHz, and 3.6GHz. The calculations are performed at different distances and exposure times of mobile phone. A simple radio frequency detection circuit has been designed to find the radiated power of different frequency. The highest specific absorption rate is calculated for skin, brain, eye tissue. Child tissue absorption rate is higher than the adult. When the radiated power of mobile phone is high the specific absorption rate for different tissue cross the safety limit. This paper also recommends the ways to diminish the effects of SAR. It is suggested that these methods will decrease the health risks. This work will be very helpful to understand the bad effect of using mobile phones and the way of reducing this effect.

Cytotoxic effect of functionalized superparamagnetic samarium doped iron oxide nanoparticles for hyperthermia application

Magnetic Fluid Hyperthermia (MFH) is an emerging and safe technique for cancer treatment. Radiotherapy and Chemotherapy are widely adopted techniques for treating cancer but cause damage to the nearby healthy tissue. This paves the way for hyperthermia treatment for cancer. Since healthy cells are more heat-tolerant than malignant cells, magnetic nanoparticles with superparamagnetic properties were used in hyperthermia treatment. Surface modified magnetite (Fe3O4) iron oxide nanoparticles with enhanced stability, solubility, bio-compatibility and magnetic property were employed in hyperthermia treatment. In the present study, Superparamagnetic Samarium doped magnetite (Fe3O4:Sm) nanoparticles were functionalized with Oleylamine (OAm) and polyvinyl alcohol (PVA) by the sol-gel process. The obtained nanoparticles were characterized by X-ray powder diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), Transmission Electron Microscopy (TEM), and UV–Visible diffuse reflectance spectroscopy (UV-DRS), Thermogravimetric analysis (TGA) and Vibrating Sample Magnetometer (VSM). From XRD data, the crystallite size of oleylamine coated samarium doped magnetite (OAm–Fe3O4:Sm) and PVA-coated samarium doped Fe3O4 (PVA- Fe3O4:Sm) were found to be 9.5 nm and 10.9 nm, respectively. TEM images of the functionalized nanoparticles were visualized as a spherical structure with reduced agglomeration. UV-DRS gives the bandgap value of OAm–Fe3O4:Sm and PVA- Fe3O4:Sm coated samarium doped magnetite to be 2.3 eV and 2 eV respectively. VSM measurement of OAm-Fe3O4:Sm and PVA- Fe3O4:Sm coated, showed superparamagnetic behaviour. The cytotoxicity study on the L929 cell line shows that both oleylamine and PVA-coated samarium doped magnetite were less toxic and biocompatible compared to the uncoated Fe3O4:Sm. The hyperthermia study reveals a rise in temperature within a few seconds with a high Specific Absorption Rate (SAR) value, confirming that the functionalized Samarium doped Fe3O4 was an effective nanomaterial for hyperthermia application.

Structural, Magnetic, and Magnetothermal Properties of Co100−xNix Nanoparticles for Self-Controlled Hyperthermia

In this study, the structural and magnetic properties of a series of functionalized Co100−xNix (x = 20, 30, 40, 50, 60, 80, 85) nanoparticles (NPs) were analyzed with the objective of attaining a high specific absorption rate (SAR). The magnetic nanoparticles (MNPs) obtained by ball milling at 1425 rpm lie in the range of 03–29 nm and are studied as potential candidates for magnetic fluid hyperthermia. Magnetic measurements show that all samples possess soft ferromagnetic properties with the reduction in the Curie temperature (TC) by Ni substitution in Co100−xNix alloys and by ball milling. The specific absorption rate (SAR) and specific loss power (SLP) obtained from magnetothermal measurements for powder and fluid samples lie in the range 4.4–83 W/g and 19–382 W/g, respectively, showing strong dependence on structural and magnetic properties. The SAR/SLP values as a function of the applied field at 425 kHz display a square dependence on the applied magnetic field below 165 Oe, which is expected for single domain ferromagnetic nanoparticles, but deviate from this at higher values of the applied field. We also obtained the effective anisotropy constant Keff for ball-milled nanoparticles at 1425 rpm for 200, 300, and 500 min. within the framework of linear response theory, showing strong dependence on average crystallite size. Additionally, the toxicity of the prepared nanoparticles in the form of percentage hemolysis was controlled with oleic acid.

Multifunctional nanocarriers of Fe3O4@PLA-PEG/curcumin for MRI, magnetic hyperthermia and drug delivery.

Background: Despite medicinal advances, cancer is still a big problem requiring better diagnostic and treatment tools. Magnetic nanoparticle (MNP)-based nanosystems for multiple-purpose applications were developed for these unmet needs. Methods: This study fabricated novel trifunctional MNPs of Fe3O4@PLA-PEG for drug release, MRI and magnetic fluid hyperthermia. Result: The MNPs provided a significant loading of curcumin (∼11%) with controllable release ability, a high specific absorption rate of 82.2W/g and significantly increased transverse relaxivity (r2=364.75mM-1 s-1). The in vivo study confirmed that the MNPs enhanced MRI contrast in tumor observation and low-field magnetic fluid hyperthermia could effectively reduce the tumor size in mice bearing sarcoma 180. Conclusion: The nanocarrier has potential for drug release, cancer treatment monitoring and therapy.

Albumin Stabilized Fe@C Core-Shell Nanoparticles as Candidates for Magnetic Hyperthermia Therapy.

Carbon-encapsulated iron nanoparticles (Fe@C) with a mean diameter of 15 nm have been synthesized using evaporation–condensation flow–levitation method by the direct iron-carbon gas-phase reaction at high temperatures. Further, Fe@C were stabilized with bovine serum albumin (BSA) coating, and their electromagnetic properties were evaluated to test their performance in magnetic hyperthermia therapy (MHT) through a specific absorption rate (SAR). Heat generation was observed at different Fe@C concentrations (1, 2.5, and 5 mg/mL) when applied 331 kHz and 60 kA/m of an alternating magnetic field, resulting in SAR values of 437.64, 129.36, and 50.4 W/g for each concentration, respectively. Having such high SAR values at low concentrations, obtained material is ideal for use in MHT.

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.