Search

Novel strategies utilizing magnetic nanoparticles (MNPs) and magnetic fields are being developed to enhance bone tissue engineering efficacy. This article first reviewed cutting-edge research on the osteogenic enhancements via magnetic fields and MNPs. Then the current developments in magnetic strategies to improve the cells, scaffolds and growth factor deliveries were described. The magnetic-cell strategies included cell labeling, targeting, patterning, and gene modifications. MNPs were incorporated to fabricate magnetic composite scaffolds, as well as to construct delivery systems for growth factors, drugs and gene transfections. The novel methods using magnetic nanoparticles and scaffolds with magnetic fields and stem cells increased the osteogenic differentiation, angiogenesis and bone regeneration by 2-3 folds over those of the controls. The mechanisms of magnetic nanoparticles and scaffolds with magnetic fields and stem cells to enhance bone regeneration were identified as involving the activation of signaling pathways including MAPK, integrin, BMP and NF-κB. Potential clinical applications of magnetic nanoparticles and scaffolds with magnetic fields and stem cells include dental, craniofacial and orthopedic treatments with substantially increased bone repair and regeneration efficacy., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

A novel magnetic hydrogel is formed via the field-directed assembly of magnetic nanomaterials during the gelation process. The novel magnetic hydrogel exhibits direction-dependent thermogenesis in an alternating magnetic field. The specific absorption rate value in the direction along the assemblies can be 2.1-fold as much as that in the direction normal to the assemblies while the heating rate is 6-8-fold. Due to the anisotropic thermogenesis, the novel magnetic hydrogel also shows a direction-dependent release of drugs that has a 3.4-fold difference between the two directions., (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Magnetic skyrmions offer promising prospects for constructing future energy-efficient and high-density information technology, leading to extensive explorations of new skyrmionic materials recently. The topological Hall effect has been widely adopted as a distinctive marker of skyrmion emergence. Alternately, here we propose a novel signature of skyrmion state by quantitatively investigating the magnetoresistance (MR) induced by skyrmionic bubbles in CeMn2Ge2. An intriguing finding was revealed: the anomalous MR measured at different temperatures can be normalized into a single curve, regardless of sample thickness. This behavior can be accurately reproduced by the recent chiral spin textures MR model. Further analysis of the MR anomaly allowed us to quantitatively examine the effective magnetic fields of various scattering channels. Remarkably, the analyses, combined with the Lorentz transmission electron microscopy results, indicate that the in-plane scattering channel with triplet exchange interactions predominantly governs the magnetotransport in the Bloch-type skyrmionic bubble state. Our results not only provide insights into the quantum correction on MR induced by skyrmionic bubble phase, but also present an electrical probing method for studying chiral spin texture formation, evolution, and their topological properties, which opens up exciting possibilities for identifying new skyrmionic materials and advancing the methodology for studying chiral spin textures. [ABSTRACT FROM AUTHOR]

The highly regarded Fe2P-based magnetocaloric materials are usually fabricated by ball milling, and require an additional extended annealing treatment at high temperatures (at temperatures up to 1423 K for several hours to days). In this work, we show that fabricating Mn1.3Fe0.6P0.5Si0.5 into the form of microwires attained 82.1 wt.% of the desired Fe2P phase in the as-cast state. The microwires show a variable solidification structure along the radial direction; close to the copper wheel contact, Fe2P phase is in fine grains, followed by dendritic Fe2P grains and finally secondary (Mn,Fe)5Si3 phase in addition to the dendritic Fe2P grains. The as-cast microwires undergo a ferro- to para-magnetic transition with a Curie temperature of 138 K, showing a maximum isothermal magnetic entropy change of 4.6 J kg−1 K−1 for a magnetic field change of 5 T. With further annealing, a two-fold increase in the maximum isothermal magnetic entropy change is found in the annealed microwires, which reveal 88.1 wt.% of Fe2P phase. [ABSTRACT FROM AUTHOR]

'Magic-angled' structure currently attracts increasing attention from condensed matter physics due to its amazing performance in superconductivity of graphene. The similar pattern formation of nanoparticles will bring about novel physics in nanoscale that causes the next generation nanodevices. However, it remains a challenging task to acquire such patterns by self-assembly process. In this article, we reported a Moiré interference pattern formation of magnetic nanoparticles regulated by a rotational magnetic field. The colloidal concentration, the strength, and the frequency of magnetic field were found to affect the pattern formation. The mechanism lied in a two-step process. First, the magnetic nanoparticles formed bilayers of superlattice driven by hydrophobic interaction of interfacial self-assembly. Then, the bilayers of superlattice yielded asynchronous rotational displacement resulting from the magnetic force so that the Moiré interference pattern of nanoparticles formed. This fabrication methodology based on the field-controlled self-assembly provided a novel and simple means to get 'magic angled' structures in nanoscale that will enrich the physical understanding of nanotechnology. [ABSTRACT FROM AUTHOR]

Herein, fluid oil joule annealing modulation (FOJA) for improving the giant magnetoimpedance (GMI) property of CoFe‐based microwires with the microstructure is adopted, and magnetic domain structure is systematically investigated. Compared with general joule annealing (JA) method, a much larger DC current can be used. The maximum GMI value is 440.8% in the 250 mA FOJA‐treated sample and the maximum monotonically increasing magnetic field is 12 Oe in 400 mA FOJA‐treated sample. In the 100–400 mA FOJA‐treated samples, there is a nearly linear increase and decrease relationship between GMI and the magnetic field. In addition, the FOJA method can control the radial stress release and helical magnetic domains of the microwire by changing the Joule heat transfer and the circumferential magnetic field and then tune the GMI performance of the microwires. The remarkable features, including a continuous and clear linear‐sensitive response field Hex of 0–95 Oe, quick response sensitivity, large GMI ratio, and excellent tunability, make the FOJA‐tailored microwires promising candidate material for miniaturized GMI sensors. [ABSTRACT FROM AUTHOR]

Objective: Targeting in vivo has been a spotlight for precise medicine. Multiple strategies have been proposed for this issue. However, the efficiency of solely biochemical strategies currently remains to be improved. It has been thought that external field-guided targeting will be a beneficial supplement for the passive and the active targeting. Methods: Here, we focused on the magnetic field-guided targeting of magnetized erythrocytes, discovering that a focused magnetic field can direct aggregation of magnetic erythrocytes into a specific region in vivo. Results: The systematic investigation about the aggregates in cerebral vessels showed that the aggregates were isotropic and able to stably exist for six hours. The formation of cellular aggregates can alter echoing characteristic of the blood vessels meaning the vascular wall became more rigid. If the erythrocytes were repeatedly directed into aggregation in an identical region, a stable plaque of erythrocytes can form, which can mimic the process of thrombosis. Significance: We believe these results will be beneficial to the development of novel engineered strategy for targeted delivery of drugs and modeling of vascular diseases. [ABSTRACT FROM AUTHOR]

Ni50Mn25Ga20Fe5 ferromagnetic shape memory alloy microwires with diameters of ∼ 30–50 μm and grain sizes of ∼ 2–5 μm were prepared by melt-extraction technique. A step-wise chemical ordering annealing was carried out to improve the superelasticity strain and recovery ratio which were hampered by the internal stress, compositional inhomogeneity, and high-density defects in the as-extracted Ni50Mn25Ga20Fe5 microwires. The annealed microwires exhibited enhanced atomic ordering degree, narrow thermal hysteresis, and high saturation magnetization under a low magnetic field. As a result, the annealed microwire showed decreased superelastic critical stress, improved reversibility, and a high superelastic strain (1.9%) with a large recovery ratio (> 96%). This kind of filamentous material with superior superelastic effects may be promising materials for minor-devices. [ABSTRACT FROM AUTHOR]

Objective: The interaction between superparamagnetic iron oxide (SPIO) nanoparticles and mesenchymal stem cells (MSCs) in the presence of pulsed magnetic field (PMF) has become an important area of research in recent years. Methods: A parameter-adjustable pulsed magnetic field was developed based on the principle of insulated gate bipolar translator transistor-controlled discharge of large capacitances. The internalizations of SPIO nanoparticles by MSCs were investigated under the treatment of PMF in both intermittent stimulation mode and continuous stimulation mode. Results: The intensities and frequencies of pulsed magnetic field can be adjustable in the range of 1.9–4.6 mT and 3–5 kHz, respectively. This PMF was safe to the MSCs. However, the uptake of SPIO nanoparticles by MSCs was significantly prohibited under the treatment of kHz-ranged PMF while the 10 Hz PMF enhanced the cellular uptake of nanoparticles. This phenomenon was relative with the magnetic effect of the PMF with different frequency. Conclusion: The PMF can be used to effectively regulate the cellular uptake of SPIO nanoparticles and the mechanism lies in the magnetic effect. Significance: The interaction between SPIO nanoparticles and the MSCs is a fundamental and important issue for nanomedicine and stem cell research. Our results demonstrate that the external magnetic field can be used to regulate their interaction. We believe that this safe, facile, and flexible method will greatly promote the development and clinical translation of regenerative medicine and nanomedicine. [ABSTRACT FROM AUTHOR]

During billions of years of evolution, some species develop fantastic magneto‐perception, offering a biomimetic route to develop the next generation of magneto‐sensors. Recently, a novel principle was proposed to explain the navigation of pigeons in the presence of geomagnetic fields and sunlight. The key link is thought to lie in the magneto‐optically involved conformational variation of magnetoreceptor protein (MagR)/cryptochrome (Cry4) complex. The MagR/Cry4 complex is fabricated and purified in vitro, creating a magneto‐sensing device by immobilization of this protein on a graphene‐modified electrochemical electrode. By using electrochemical impedance spectroscopy, magneto‐sensing with a current detectability of 10 mT is realized with MagR/Cry4 complex. It is proved that this process requires the involvement of both magnetic fields and light, partly confirming in vitro the magneto‐perceptive mechanism of MagR/Cry4 complex. It is also shows that this device can be used to reflect the anisotropic responses of nanomaterials to the external magnetic field. It is believed this protein‐based magneto‐sensing will greatly boost development of bioelectronics and deepen understanding of the phenomena of magneto‐perception for organisms. [ABSTRACT FROM AUTHOR]

Ni45.6Fe3.6Mn38.4Sn12.4 microwires, with nanoscale γ-phase precipitates that enhance the magnetocaloric effects (MCEs) and mechanical properties, were prepared by a melt-extraction technique and subsequent high temperature annealing. The atomic ordering degree significantly increased after annealing, leading to a considerable increment in the structural entropy change (ΔStr) from 4.5 J/kg·K in the as-extracted microwire to 26.6 J/kg·K in the annealed one, and the magnetization difference (ΔM) from 35 A·m2/kg to 51 A·m2/kg under a magnetic field of 5.0 T. Consequently, a positive magnetic entropy change (ΔSM) peak of 15.2 J/kg·K with working temperature span (ΔTFWHM) of 12 K for the first-order martensite transformation followed by a negative ΔSM peak of −4.3 J/kg·K with ΔTFWHM = 50 K for the second-order magnetic transition under μ0ΔH = 5.0 T was achieved. By employing both magnetizing and demagnetizing processes for magnetic cooling, the two successive inverse and conventional MCEs in Ni–Fe–Mn–Sn microwires may show potential applications for micro-devices and systems. [ABSTRACT FROM AUTHOR]

Based on sharp geometry of Ni nanowires, we developed a novel high-gradient magnetic separator that was composed of a nanowires array and a uniform magnetic field. When suspension of magnetic nanoparticles (MNPs) flowed through it, the relatively large nanoparticles or clusters were removed from the suspension so that the size distribution can be improved. The separation resulted from magnetic force so that extra molecules or solvents were unnecessary to add. The performance was proved by scanned electron microscopy characterization and dynamic light scattering measurement. The improvement in magnetic colloidal dispersivity is important for the biomedical application of MNPs. Our results may also play a role in microfluidic application and nanoparticle-based detection. [ABSTRACT FROM AUTHOR]

Gold nanoshells currently attract increasing researchinterestsdue to the important role in many subjects. For practical applications,random arrangement of the nanoparticles is often unfavored so thatthe assembly of gold nanoshells is becoming a central issue. We hereproposed to utilize time-variant magnetic field to direct the assemblyof gold nanoshells. It was discovered that the alternating magneticfield can mediate the vortex-like assembly of gold nanoshells. Themechanism was explored and thought to be relative with the electricfield of induction which caused the thermal gradient on the substrateand the electric force. The vortexlike structure as well as the assemblymechanism will play an important role in research and applicationof gold nanomaterials. [ABSTRACT FROM AUTHOR]

Abstract: Here we reported the assembly of horseradish peroxidase molecules mediated by the alternating magnetic field. The field can make quasi-one-dimensional assembly conformations. We proved the phenomenon was relative to the magnetic property of HRP molecules. Importantly, the electromagnetic field had little influence on the biological activity of HRP molecules. [Copyright &y& Elsevier]

Field-assisted synthesis has been one of the common strategies of nanoparticles preparation with enhanced properties. However, most researches focused on exploring the effects of monofunctional static field on the structure and properties of synthetic nanomaterials, few researchers have applied fields with period variation as assistance. Combining medium alternating current magnetic field with most widely used method traditional chemical co-precipitation held potential in preparation high quality Fe 3 O 4 nanoparticle. In this study, Fe 3 O 4 nanoparticle clusters were prepared in alternating-current magnetic field (ACMF) by co-precipitation principle, structural and magnetic properties were also characterized. Results demonstrated that Fe 3 O 4 nanoparticle clusters prepared by co-precipitation heated in ACMF indicated a better heat production under ACMF, comparing with Fe 3 O 4 nanoparticle clusters with similar size and distribution prepared by classic co-precipitation. It might be due to the magnetic effects induced by ACMF that Fe 3 O 4 nanoparticles tend to grow along the magnetization direction. This technology might hold promise in preparation high performance magnetic nanomaterial in the future. [ABSTRACT FROM AUTHOR]

Herein, we reported the influences of accumulated direct current annealing (ADA) on the GMI properties and microstructures of Zr-doped melt-extracted (Co 68.15 Fe 4.35 Si 12.25 B 12.25 Zr 3 ) amorphous microwires. There indicated that ADA-ed wires enhanced GMI properties and improved the microstructures remarkably in comparison with as-fabricated wires. The maximum GMI ratio [Δ Z / Z 0 ] max and equivalent magnetic circumferential anisotropy field (EMCAF) of ADA-ed microwires were increased to 256.01% and 4 Oe at 20 MHz, respectively, which are more than nearly 8 and 2 times of 33.62% and 1.6 Oe for as-fabricated wires, respectively. Moreover, the maximum magnetic field response sensitivity ( ξ max ) increased to 372.57%/Oe, which is much higher than the as-fabricated wires of 44.71%/Oe. The remarkable enhancement of GMI performance was considered as the microstructural evolution including structural relaxation, appearance of nano-crystallization, and circumferential arrangement of surface magnetic domains. Nano-crystallization degree and circumferential magnetic domains arrangement were effectively improved by actions of Joule thermal energy and circular magnetic field generated ADA as shown in HRTEM and magnetic force microscope (MFM) analysis. Based on above, both the excellent GMI performances and relatively large ξ max values indicate the ADA is an effective annealing technique for thermal treating the melt-extracted amorphous wires which applied for potentially magnetic sensor in detecting low-intensity magnetic fields. [ABSTRACT FROM AUTHOR]

Ferromagnetic shape memory Ni–Mn-Ga alloys exhibit magnetostructural coupling during the Curie points, which may alter their magnetocaloric effect (MCE). Here MCE of Ni–Mn-Ga alloy microwires are tuned by Fe-doping. The chemical ordering annealed Ni 49·6 Mn 25.5 Ga 22.6 Fe 2.3 (Fe2), Ni 49·6 Mn 25 Ga 21 Fe 4.4 (Fe4) and Ni 48 Mn 26 Ga 19.5 Fe 6.5 (Fe6) microwires have diameters of ~30–50 μm and grain sizes of ~2–5 μm. The magnetic entropy changes (Δ S m) of the microwires increase with external magnetic fields, then reach a positive peak and finally decrease to negative peak at a high field. The direct (negative Δ S m , DMCE) and inverse (positive Δ S m , IMCE) MCEs are attributed to microscopic and mesoscopic couplings in microwires. In addition, the specific features of MCEs are also controlled by the magnetization difference (Δ M) between martensite and austenite phases. Interestingly, the DMCE and IMCE are component dependent. At high Δ M , the linearly decreasing region is dominant and Fe4 and Fe6 microwires produce a negative Δ S m at high magnetic fields due to the microscopic coupling with free electron valence ratio e / a = 7.692 and 7.725. On the other hand, the Δ M is small in Fe2 microwire, which has a positive Δ S m because mesoscopic coupling is dominant with e / a = 7.607; the Δ S m is highest when a single variant martensite occurs, then decreases linearly with increasing magnetic fields. The transition from positive to negative values in Δ S m with the applied fields is related to the counterbalance of mesoscopic and microscopic couplings at e / a = 7.66. The study found that, the specific features of the MCE in the present Ni–Mn-Ga-Fe microwires have been found to be controlled by the magnetization difference between martensite/austenite phases (Δ M = M M - M A). At small Δ M , the ΔS m is first positive, reaches a maximum under a critical magnetic field (e.g. 7.6 kOe for Fe2 where a single variant martensite state occurs), and decreases linearly with H for higher fields. For high values of Δ M , the linearly decreasing region is dominant (e.g. Fe6). Image 1 • Ni–Mn-Ga-Fe microwires with fine grains were fabricated by melt-extraction. • The mixed direct and inverse MCEs caused by the magnetostructural coupling. • The MCE can be adjusted by changing the content of Fe. [ABSTRACT FROM AUTHOR]