Concentration Of Magnetic Nanoparticles Research Articles

PEROXIDASE-LIKE ACTIVITY OF MAGNETIC NANOPARTICLES IN THE PRESENCE OF BLOOD PROTEINS

The generation of hydroxyl radicals from hydrogen peroxide in aqueous solutions containing magnetic nanoparticles (MNPs), hemoglobin (Hb), immunoglobulin G (IgG), and human serum albumin (HSA) has been determined. The dependence of the rate of formation of the oxidized product of o-phenylenediamine (o-PDA) on the concentration of MNPs in solution, as well as on the concentration of proteins, was obtained. The peroxidase-like activity of MNPs was shown to decrease in the presence of HSA and IgG, while the addition of Hb to the reaction mixture was leading to its decrease and increase depending on protein concentration. The obtained effects can be used in the development of systems based on MNPs for theranostics, in particular, for suppression of tumor growth, and in predicting the ability of particles to catalyze the generation of reactive oxygen species (ROS) in vivo.

Preparation of graphene oxide enhanced magnetic composite hydrogels by one‐pot method for selective adsorption

AbstractMagnetic composite hydrogels exhibit promising prospects for diverse applications, but their mechanical properties impose limitations on their further advancement. In this study, a novel approach is proposed to directly prepare magnetic composite hydrogels utilizing nanoferroferric oxide, aiming to replace the existing preparation method. Meanwhile, graphene oxide (GO) is introduced into magnetic composite hydrogels to enhance their mechanical characteristics. By employing ammonium citrate (AC) as a dispersant, the dispersion of ferroferric oxide magnetic nanoparticles at a concentration of 40 mg/mL is achieved, enabling their coexistence with GO for the preparation of magnetic composite hydrogels. Notably, the incorporation of 3 mg/mL GO and 40 mg/mL magnetic nanoparticles in polyacrylamide (PAM) hydrogel yields remarkable improvements in maximum stress and strain, reaching 148 kPa and 496%, respectively. In contrast, magnetic composite hydrogels without GO exhibit lower values of 46.5 kPa and 351%. The presence of magnetic nanoparticles imparts magnetism to the hydrogel, with higher concentrations of magnetic nanoparticles leading to increased magnetism. Moreover, the presence of AC and GO renders the hydrogels electronegative, thereby endowing them with selective adsorption capabilities. In summary, the magnetic composite hydrogels prepared by one‐pot method have good mechanical properties and selective adsorption capacity, and have good application potential.

A threefold increase in SAR performance for magnetic hyperthermia by compositional tuning in zinc-substituted iron oxide superparamagnetic nanoparticles with superior biocompatibility

In this work, we report a ultrahigh specific absorption rate (SAR) performance in Zn-substituted magnetite superparamagnetic (SPM) nanoparticles (NPs) for potential application in magnetic hyperthermia (MHT)-based cancer treatment. Although MHT shows promise in cancer therapy, challenges such as low heating performance, agglomeration of magnetic nanoparticles (MNPs) in blood veins, cytotoxicity, and hemocompatibility have hindered clinical uses. To overcome these challenges, we adopted a reverse-micelles based coprecipitation synthesis approach to prevent MNPs agglomeration and optimized the substitution of Zn ions in magnetite to enhance heating performance. Calorimetric measurements showed SAR values of 118 W/g and 181 W/g for magnetite NPs using the initial slope method (ISM) and Box Lucas method (BLM), respectively. Through our compositional optimizations, we achieved a significant increase in SAR value by consciously substituting Zn2+ ions in the magnetite lattice. Specifically, we obtained SAR values of 325 W/g and 579 W/g (>300% increase) for Zn0.3Fe2.7O4 MNPs using ISM and BLM, respectively. This enhancement can be attributed to improved saturation magnetization (174–257 kA/m) and magneto-crystalline anisotropy (12–24 kJ/m3). The increase in saturation magnetization in the magnetite MNPs can be explained by the higher magnetic moment resulting from increased Zn concentration up to ZnxFe3-xO4(x = 0.3), strengthening the JAB interaction. However, further increases in Zn concentration lead to a decrease in saturation magnetization due to non-collinearity, as described by the Yafet-Kittle model. Our optimized MNPs exhibit improved heating performance, enabling the use of lower MNPs concentrations for cancer treatment, reducing potential toxicity effects. Biocompatibility investigations demonstrated a low hemolysis rate (<5%) in a hemolysis assay with red blood cells and high cytocompatibility (>92% cell viability) in MTT assays for all compositions, confirming their potential suitability for clinical applications. This study offers a promising approach to enhance SAR performance, addressing MHT-based cancer treatment challenges, and improving clinical suitability.

Development of a Microfluidic Chip System with Giant Magnetoresistance Sensor for High-Sensitivity Detection of Magnetic Nanoparticles in Biomedical Applications.

Magnetic nanoparticles (MNPs) have been widely utilized in the biomedical field for numerous years, offering several advantages such as exceptional biocompatibility and diverse applications in biology. However, the existing methods for quantifying magnetic labeled sample assays are scarce. This research presents a novel approach by developing a microfluidic chip system embedded with a giant magnetoresistance (GMR) sensor. The system successfully detects low concentrations of MNPs with magnetic particle velocities of 20 mm/s. The stray field generated by the magnetic subject flowing through the microchannel above the GMR sensor causes variations in the signals. The sensor's output signals are appropriately amplified, filtered, and processed to provide valuable indications. The integration of the GMR microfluidic chip system demonstrates notable attributes, including affordability, speed, and user-friendly operation. Moreover, it exhibits a high detection sensitivity of 10 μg/μL for MNPs, achieved through optimizing the vertical magnetic field to 100 Oe and the horizontal magnetic field to 2 Oe. Additionally, the study examines magnetic labeled RAW264.7 cells. This quantitative detection of magnetic nanoparticles can have applications in DNA concentration detection, protein concentration detection, and other promising areas of research.

Fabrication of peristaltic electromagnetic micropumps using the SLA 3D printing method from a novel magnetic nano-composite material

Micropumps are one of the main components of microfluidic systems that play an essential role in the development of these systems. They are responsible for the fluid movement inside the microfluidic systems. In this paper, three electromagnetic micropumps with single, double, and triple chambers fabricated using the stereolithography (SLA) 3D printing method from a novel UV-curable magnetic nanocomposite material are presented. The components of this micropump include nozzle-diffuser microchannels, a chamber, a flexible magnetic membrane, and a micro-coil. To determine the characteristics of the proposed micropumps, the effect of the electric current signal and its patterns and magnetic field strength on the temperature changes, magnetic nanoparticle concentration on the membrane displacement, and flow rate of the micropump have been investigated. The micropump membrane with 5 wt% nanoparticles concentration can achieve a displacement of 65 µm for an electric current of 1000 mA in 12 s. The highest fluid flow rate of single, double, and triple chamber micropumps are 78, 316, and 600 nL/s, respectively, at an electric signal with a period of 8 s and a duty cycle of 60%.

Steerable artificial magnetic bacteria with target delivery ability of calcium carbonate for soil improvement.

The microbial-induced carbonate precipitation (MICP) has acquired significant attention due to its immense potential in sustainable engineering applications, particularly in soil improvement. However, the precise control of microbial-induced calcium carbonate precipitation remains a formidable challenge in engineering practices, owing to the uncertain movement paths of bacteria and the nonuniform distribution of soil pores. Taking inspiration from targeted therapy in medicine, this paper presents novel research on the development and validation of magnetically responsive bacteria. These bacteria demonstrate the ability to target calcium carbonate precipitation in a microfluidic chip, thereby promoting an environmentally friendly and ecologically sustainable biomineralization paradigm. The study focuses on investigating the migration of magnetite nanoparticles (MNPs) in aqueous solutions and enhancing the stability of MNP culture liquids. A specially designed microfluidic chip is utilized to simulate natural sand particles and their pores, while an external magnetic field is applied to precisely control the movement path of the artificial magnetic bacteria, enabling targeted precipitation of calcium carbonate at the micron-scale. Verification of the engineered artificial magnetic bacteria and their ability to induce calcium carbonate precipitation is conducted through SEM-EDS analysis, microfluidic chip observations, and the application of the K-means algorithm and ImageJ software to analyze calcium carbonate formation. The influence of the concentration of magnetic nanoparticles on the calcium carbonate production rate was also studied. The results confirm the potential of the artificial magnetic bacteria for future engineering applications. KEY POINTS: • Sporosarcina pasteurii is first time successfully engineered into artificial magnetic bacteria. • The artificial magnetic bacteria show excellent performance of targeted transportation and directional deposition of CaCO3 in microfluidic chip. • The emergence of artificial magnetic bacteria promotes paradigm shift of next generation environmentally friendly biomineralization.

Magneto-Responsive Textiles for Non-Invasive Heating.

Magneto-responsive textiles have emerged lately as an important carrier in various fields, including biomedical engineering. To date, most research has been performed on single magnetic fibers and focused mainly on the physical characterization of magnetic textiles. Herein, from simple woven and non-woven textiles we engineered materials with magnetic properties that can become potential candidates for a smart magnetic platform for heating treatments. Experiments were performed on tissue-mimicking materials to test the textiles' heating efficiency in the site of interest. When the heat was induced with magneto-responsive textiles, the temperature increase in tissue-mimicking phantoms depended on several factors, such as the type of basic textile material, the concentration of magnetic nanoparticles deposited on the textile's surface, and the number of layers covering the phantom. The values of temperature elevation, achieved with the use of magnetic textiles, are sufficient for potential application in magnetic hyperthermia therapies and as heating patches or bandages.

Hydrogel platform with tunable stiffness based on magnetic nanoparticles cross-linked GelMA for cartilage regeneration and its intrinsic biomechanism.

Cartilage injury affects numerous individuals, but the efficient repair of damaged cartilage is still a problem in clinic. Hydrogel is a potent scaffold candidate for tissue regeneration, but it remains a big challenge to improve its mechanical property and figure out the interaction of chondrocytes and stiffness. Herein, a novel hybrid hydrogel with tunable stiffness was fabricated based on methacrylated gelatin (GelMA) and iron oxide nanoparticles (Fe2O3) through chemical bonding. The stiffness of Fe2O3/GelMA hybrid hydrogel was controlled by adjusting the concentration of magnetic nanoparticles. The hydrogel platform with tunable stiffness modulated its cellular properties including cell morphology, microfilaments and Young's modulus of chondrocytes. Interestingly, Fe2O3/GelMA hybrid hydrogel promoted oxidative phosphorylation of mitochondria and facilitated catabolism of lipids in chondrocytes. As a result, more ATP and metabolic materials generated for cellular physiological activities and organelle component replacements in hybrid hydrogel group compared to pure GelMA hydrogel. Furthermore, implantation of Fe2O3/GelMA hybrid hydrogel in the cartilage defect rat model verified its remodeling potential. This study provides a deep understanding of the bio-mechanism of Fe2O3/GelMA hybrid hydrogel interaction with chondrocytes and indicates the hydrogel platform for further application in tissue engineering.

Effects of agro-waste resources on characteristics of Fe/nanocellulose hybrids and their applications as novel Fenton-like catalysts in dye removal from wastewater

Herein, a novel, effective and bio-based Fenton-like catalyst by in situ incorporation of Fe2O3 nanoparticles on the surface of nanocellulose (NCs) was synthesized from sugar beet pulp (SBP) and utilized for efficient removal of three different dyes. Firstly, different NC samples were synthesized by acid hydrolysis of two different biomass (SBP and Q-quinoa husk) at various concentrations of H2SO4. The characterization analyses of samples showed that SBP-based NCs prepared using 60% concentration of H2SO4 (1 h string at 50 °C) showed the highest crystallinity (56.7%), lowest aggregation, highest surface negative charge (−38.5 mV), and largest surface area (13.9 m2/g) compared to the Q-based NCs. Both SBP and Q-based nanocatalyst utilized for degradation of dyes (methylene blue (MB), crystal violet (CV), and congo red (CR)), and SBP-based sample (Fe/NC-S3) displayed the best results in dye removal due to its larger specific surface area (39.8 vs. 9.2 m2/g), and higher content of magnetic nanoparticles (6.7 vs. 3.7 at% of Fe) than Q-based catalyst. At optimum conditions, Fe/NC-S3 nano-catalyst (2 g/L), in the presence of H2O2 (30 mM) removed MB, CV, and CR dyes (30 mg/L), in 30 min, at neutral pH, with 98%, 96%, and 62% removal efficiencies, respectively. Kinetic studies revealed that pseudo-first-order model was appropriate model to explain the decolorization of dyes at these conditions, and the rate constants were 0.0217, 0.018, and 0.0113 min−1 for the degradation of MB, CV, and CR, respectively. Moreover, raising the temperature from 15 ºC to 35 ºC resulted in enhancement of removal performance of nano-catalyst for all dyes. Fe/NC-S3 nano-catalyst showed proper reusability (just around 20% decrease for removal of all three dyes after ten consecutive reuse runs). Treatment of real water effluent (collected from a textile factory) containing mixture of all three dyes by Fe/NC-S3 and H2O2 approved the practical application of nano-catalyst in dye removal from complex matrixes even after nine reusing cycles. The results confirmed that SBP biomass could effectively turn to valuable NC nanocarriers for synthesis of advanced and innovative catalysts with proficient catalytic activity, stability, and recyclability.

Extraction method of nanoparticles concentration distribution from magnetic particle image and its application in thermal damage of magnetic hyperthermia

Magnetic particle imaging (MPI) technology can generate a real-time magnetic nanoparticle (MNP) distribution image for biological tissues, and its use can overcome the limitations imposed in magnetic hyperthermia treatments by the unpredictable MNP distribution after the intratumoral injection of nanofluid. However, the MNP concentration distribution is generally difficult to be extracted from MPI images. This study proposes an approach to extract the corresponding concentration value of each pixel from an MPI image by a least squares method (LSM), which is then translated as MNP concentration distribution by an interpolation function. The resulting MPI-based concentration distribution is used to evaluate the treatment effect and the results are compared with the ones of two baseline cases under the same dose: uniform distribution and MPI-based distribution considering diffusion. Additionally, the treatment effect for all these cases is affected by the blood perfusion rate, which is also investigated deeply in this study. The results demonstrate that the proposed method can be used to effectively reconstruct the concentration distribution from MPI images, and that the weighted LSM considering a quartic polynomial for interpolation provides the best results with respect to other cases considered. Furthermore, the results show that the uniformity of MNP distribution has a positive correlation with both therapeutic temperature distribution and thermal damage degree for the same dose and a critical power dissipation value in the MNPs. The MNPs uniformity inside biological tissue can be improved by the diffusion behavior after the nanofluid injection, which can ultimately reflect as an improvement of treatment effect. In addition, the blood perfusion rate considering local temperature can have a positive effect on the treatment compared to the case which considers a constant value during magnetic hyperthermia.

Magnetic heating of water dispersible and size-controlled superparamagnetic cobalt iron oxide nanoparticles

Magnetic nanoparticles have been of great interest for various biomedical applications due to their controllability in the distance. Monodisperse superparamagnetic CoFe2O4 (CFO) nanoparticles were synthesized by solvothermal method with oleic acid. The oleic acid ligands are exchanged with citric acid to obtain water-dispersible citric acid-coated CA (CFO–CA) nanoparticles. The M–H curve recorded at room temperature shows the superparamagnetic nature of CFO nanoparticles for both oleic- and citric-coated samples. The magnetic heating performance of CFO–CA shows an exciting dependence on the particle size and surface functionality. The hyperthermia efficiency of CFO–CA nanoparticles increases with increasing magnetic field strength and nanoparticle concentration. A specific absorption ratio value of 152.7 W/g obtained in this study is comparable to other investigations, demonstrating a great potential of CFO–CA nanoparticles for hyperthermia-based treatments. This controlled synthesis process can be applied to various functional biomedical nanoparticles to prepare nanoparticles with designed surface moieties for further potential applications.

Surface acoustic wave investigation of magnetic nanoparticle size and concentration effect on liquid crystal behavior.

The effect of spherical magnetic nanoparticles with different size (5, 10, 15, and 20 nm) and volume concentration (10-3, 5 × 10-4, and 10-4) on liquid crystal 4-cyano-4'-hexylbiphenyl (6CB) behavior was investigated using surface acoustic wave (SAW). The attenuation response of SAW propagating along with the substrate/liquid crystal interface was used to study the structural changes induced by an applied magnetic field. The obtained results showed the shift of the threshold magnetic field with an increase in the volume concentration of nanoparticles toward lower fields and also the decrease in the isotropic-nematic phase transition temperature depending on the nanoparticle size and the nanoparticle volume fraction. Results confirmed again that the bulk viscosity coefficients should dominate the SAW attenuation and that the SAW investigation in the presented configuration is applicable to monitoring of the role of magnetic dopants in structural changes under external fields. Some theoretical background of the presented SAW investigation is introduced as well. Obtained results are discussed within the context of previous ones.

Application of Functionalized Fe3O4 Magnetic Nanoparticles Using CTAB and SDS for Oil Separation from Oil-in-Water Nanoemulsions.

Using magnetic nanoparticles (MNPs) for emulsified oil separation from wastewater is becoming increasingly widespread. This study aims to synthesize MNPs using amphiphilic coatings to stabilize the MNPs and prevent their agglomeration for efficiently breaking oil-in-water nanoemulsions. We coat two different sizes of Fe3O4 nanoparticles (15-20 and 50-100 nm) using cetyltrimethylammonium bromide (CTAB) and sodium dodecyl sulfate (SDS) with surfactant-to-MNP mass ratios of 0.4 and 0.8. We study the effect of various variables on the demulsification performance, including the MNP size and concentration, coating materials, and MNP loading. Based on the oil-water separation analysis, the smaller size MNPs (MNP-S) show a better demulsification performance than the larger ones (MNP-L ) for a 1000 ppm dodecane-in-water emulsion containing nanosized oil droplets (250-300 nm). For smaller MNPs (MNP-S) and at low dosage level of 0.5 g/L, functionalizing with surfactant-to-MNP mass ratio of 0.4, the functionalization increases the separation efficiency (SE) from 57.5% for bare MNP-S to 86.1% and 99.8 for the SDS and CTAB coatings, respectively. The highest SE for MNP-S@CTAB and the zeta potential measurements imply that electrostatic attraction between negatively charged oil droplets (-55.9 ± 2.44 mV) and positively charged MNP-S@CTAB (+35.8 ± 0.34 mV) is the major contributor to a high SE. Furthermore, the reusability tests for MNP-S@CTAB reveal that after 10 cycles, the amount of oil adsorption capacity decreases slightly, from 20 to 19 mg/g, indicating an excellent stability of synthesized nanoparticles. In conclusion, functionalized MNPs with tailored functional groups feature a high oil SE that could be effectively used for oil separation from emulsified oily wastewater streams.

Design of Spherical Gel-Based Magnetic Composites: Synthesis and Characterization

The purpose of the study was the synthesis and the physicochemical characterization of spherical beads of magnetically active composite ferrogels (FGs) with diameters of 2–3 mm for further application to the needs of targeted drug delivery and/or replacement therapy. Spherical FGs based on a physical network of calcium alginate (CaAlg), a chemical network of polyacrylamide (PAAm), and a combined network of calcium alginate and polyacrylamide (PAAm/CaAlg) were analyzed. FGs were filled with γ-Fe2O3 magnetic nanoparticles (MNPs) obtained by using the electrical explosion of wire method. A comparative study of the swelling behavior and of the structural features of the polymeric network in CaAlg, PAAm/CaAlg, and PAAm spherical beads was performed. It was shown that the densest network was provided by a combination of chemical and physical networking in PAAm/CaAlg FGs. If the physical network were removed from FGs it resulted in a substantial increase in the average diameter and the swelling ratio of spherical beads and a decrease in the MNPs concentration in the swollen FGs by approximately two times. It was shown that irrespective of the gel composition, the embedding of maghemite nanoparticles led to an increase in the swelling ratio of the polymeric network. This indicated the absence of strong intermolecular interactions between the polymer and the filler. The results obtained might be useful for the design of magnetically active spherical FG beads of a given size and controlled physicochemical properties.

Magnetic chitosan hydrogel induces neuronal differentiation of neural stem cells by activating RAS-dependent signal cascade

Our aim was to modulate magnetic cues to influence the differentiation of neural stem cell (NSC) into neuron during nerve repair and to explore corresponding mechanisms. Here, a magnetic hydrogel composed of chitosan matrices and magnetic nanoparticles (MNPs) with different content was prepared as the magnetic-stimulation platform to apply intrinsically-present magnetic cue and externally-applied magnetic field to NSC grown on the hydrogel. The MNP content had regulatory effects on neuronal differentiation and the MNPs-50 samples exhibited the best neuronal potential and appropriate biocompatibility in vitro, as well as accelerated the subsequent neuronal regeneration in vivo. Remarkably, the use of proteomics analysis parsed the underlying mechanism of magnetic cue-mediated neuronal differentiation form the perspective of protein corona and intracellular signal transduction. The intrinsically-present magnetic cues in hydrogel contributed to the activation of intracellular RAS-dependent signal cascades, thus facilitating neuronal differentiation. Magnetic cue-dependent changes in NSCs benefited from the upregulation of adsorbed proteins related to “neuronal differentiation”, “cell-cell interaction”, “receptor”, “protein activation cascade”, and “protein kinase activity” in the protein corona. Additionally, magnetic hydrogel acted cooperatively with the exterior magnetic field, showing further improving neurogenesis. The findings clarified the mechanism for magnetic cue-mediated neuronal differentiation, coupling protein corona and intracellular signal transduction.

High Efficacy on the Death of Breast Cancer Cells Using SPMHT with Magnetite Cyclodextrins Nanobioconjugates.

In this study, we present the experimental results obtained in vitro on the human breast adenocarcinoma cell line (MCF-7) by applying superparamagnetic hyperthermia (SPMHT) using novel Fe3O4-PAA-(HP-γ-CDs) (PAA is polyacrylic acid and HP-γ-CDs is hydroxypropyl gamma-cyclodextrins) nanobioconjugates previously obtained by us. In the in vitro SPMHT experiments, we used concentrations of 1, 5 and 10 mg/mL of Fe3O4 ferrimagnetic nanoparticles from Fe3O4-PAA-(HP-γ-CDs) nanobioconjugates suspended in culture media containing 1 × 105 MCF-7 human breast adenocarcinoma cells. The harmonic alternating magnetic field used in the in vitro experiments that did not affect cell viability was found to be optimal in the range of 160-378 Gs and at a frequency of 312.2 kHz. The appropriate duration of the therapy was 30 min. After applying SPMHT with these nanobioconjugates under the above conditions, MCF-7 cancer cells died out in a very high percentage, of until 95.11%. Moreover, we studied the field up to which magnetic hyperthermia can be safely applied without cellular toxicity, and found a new upper biological limit H × f ~9.5 × 109 A/m⋅Hz (H is the amplitude and f is the frequency of the alternating magnetic field) to safely apply the magnetic field in vitro in the case of MCF-7 cells; the value was twice as high compared to the currently known value. This is a major advantage for magnetic hyperthermia in vitro and in vivo, because it allows one to achieve a therapy temperature of 43 °C safely in a much shorter time without affecting healthy cells. At the same time, using the new biological limit for a magnetic field, the concentration of magnetic nanoparticles in magnetic hyperthermia can be greatly reduced, obtaining the same hyperthermic effect, while at the same time, reducing cellular toxicity. This new limit of the magnetic field was tested by us in vitro with very good results, without the cell viability decreasing below ~90%.

Toward the Separation of Different Heating Mechanisms in Magnetic Particle Hyperthermia.

Magnetic particle hyperthermia (MPH) is a promising method for cancer treatment using magnetic nanoparticles (MNPs), which are subjected to an alternating magnetic field for local heating to the therapeutic range of 41-45 °C. In this window, the malignant regions (i.e., cancer cells) undergo a severe thermal shock while healthy tissues sustain this thermal regime with significantly milder side effects. Since the heating efficiency is directly associated with nanoparticle size, MNPs should acquire the appropriate size to maximize heating together with minimum toxicity. Herein, we report on facile synthetic controls to synthesize MNPs by an aqueous precipitation method, whereby tuning the pH values of the solution (9.0-13.5) results in a wide range of average MNP diameters from 16 to 76 nm. With respect to their size, the structural and magnetic properties of the MNPs are evaluated by adjusting the most important parameters, i.e. the MNP surrounding medium (water/agarose), the MNP concentration (1-4 mg mL-1), and the field amplitude (20-50 mT) and frequency (103, 375, 765 kHz). Consequently, the maximum heating efficiency is determined for each MNP size and set of parameters, outlining the optimum MNPs for MPH treatment. In this way, we can address the different heat generation mechanisms (Brownian, Néel, and hysteresis losses) to different sizes and separate Brownian and hysteresis losses for optimized sizes by studying the heat generation as a function of the medium viscosity. Finally, MNPs immobilized into agarose solution are studied under low-field MPH treatment to find the optimum conditions for clinical applications.

Dual solutions on MHD radiative three-dimensional bidirectional nanofluid flow over a non-linearly permeable shrinking sheet

The bidirectional flow and thermal transfer of magnetohydrodynamics (MHD) and radiative nanofluid (magnetite-vacuum pump oil) due to a nonlinear shrinking surface in a three dimensional system is studied. The boundary layer model is first transformed into a set of ordinary differential equations using the similarity transformations, and then solved using the bvp4c solver. The accuracy of the present model is justified by comparing present data with the numerical values from the published findings. The effect of factors (magnetic parameter, radiation parameter and nanoparticles volumetric concentration) on the development of responses (skin friction coefficient and thermal rate) and critical value (separation value from laminar to turbulent flow) is observed through the graphical presentation. In addition, two solutions are attained where the first solution is affirmed as the reliable solution through stability analysis. Conclusively, the suction effect is necessary in generating the solutions under the phenomenon of opposing shrinking flow. The addition of magnetic parameter and nanoparticles concentration can enhance both responses as well as the critical value while the radiation parameter tends to reduce the heat transfer coefficient. The types of stretching/shrinking velocity (linear/nonlinear) also affect the heat transfer rate. The critical value can be extended by using the linear velocity, but, for thermal enhancement, the nonlinear form of velocity can significantly develop the thermal rate better than the linear shrinking surface.

Magnetic Nanocomposites for the Remote Activation of Sulfate Radicals for the Removal of Rhodamine B.

The widespread presence of numerous organic contaminants in water poses a threat to the ecological environment and human health. Magnetic nanocomposites exposed to an alternating magnetic field (AMF) have a unique ability for magnetically mediated energy delivery (MagMED) resulting from the embedded magnetic nanoparticles; this localized energy delivery and associated chemical and thermal effects are a potential method for removing contaminants from water. This work developed a novel magnetic nanocomposite-a polyacrylamide-based hydrogel loaded with iron oxide nanoparticles. For this magnetic nanocomposite, persulfate activation and the contamination removal in water were investigated. Magnetic nanocomposites were exposed to AMF with a model organic contaminant, rhodamine B (RhB) dye, with or without sodium persulfate (SPS). The removal of RhB by the nanocomposite without SPS as a sorbent was found to be proportional to the concentration of magnetic nanoparticles (MNPs) in the nanocomposite. With the addition of SPS, approximately 100% of RhB was removed within 20 min. This removal was attributed primarily to the activation of sulfate radicals, triggered by MNPs, and the localized heating resulted from the MNPs when exposed to AMF. This suggests that this magnetic nanocomposite and an AMF could be a unique environmental remediation technique for hazardous contaminants.

A comprehensive approach combining gradient porous metal foam and the magnetic field to regulate latent heat storage performance

This study proposes a comprehensive regulation method of gradient porous metal structure combined with the magnetic field to improve the controllability of heat utilization of latent heat thermal energy storage (LHTES) unit. Melting and solidification are considered. The enthalpy porosity method and magnetic force model describe the phase change of phase change material (PCM) and the movement of Fe3O4 nanoparticles under the magnetic field and assume the local thermal non-equilibrium model of metal foam. The numerical model is consistent with the visual experimental results of melting front evolution. The effects of magnetic nanoparticle concentration and gradient porosity on heat transfer and thermal energy change during melting and solidification are numerically studied. The results show that the phase change rate increases with the concentration of nanoparticles. The positive magnetic field further accelerates the phase change and heat energy change. The addition of copper foam considerably shortened the phase change time. The positive magnetic field accelerated the melting and heat energy change rate of PCM in copper foam by 18.2% and 23.1%, but the improvement of solidification was weak. Based on magnetic field promotion, the setting of porosity spacing with different gradients can regulate the phase interface uniformity, total heat energy, and heat energy change rate. Finally, according to different heat utilization scenarios of the LHTES system, this study gives recommended cases to optimize the performance of melting, solidification, and the phase change cycle.