Types Of Magnetic Particles Research Articles

Probability of Defects Detection in Welded Joints using the Magnetic Particle Method

The probability of defects detection (POD) is developed as an efficient tool to evaluate the detection capacity of non-destructive testing methods. An experimental study has been carried out applying the magnetic particle test method with an electromagnetic yoke on welded steel joints, which contained surface defects previously characterized in shape, size and location. The test conditions were varied, such as the type of magnetization current, and the type of magnetic particle. The probability of detecting defects in welded joints evaluated by the Hit/miss method increased with the size of the defect, independent of its shape factor. Smaller defects were likely to be detected with dry magnetic particles compared to wet fluorescent ones, a50 (2,118 mm ˂ 2,469 mm), a90 (6,395 mm ˂ 6,77 mm) and a90/95 (12,12 mm ˂ 12,19 mm).

Versatile and Accessible Magnetic Diagnosis Platform with Different Types of Magnetic Particles for Liquid and Solid Biopsies.

The diagnosis of liquid and solid biopsies by different instruments makes the clinic loading difficult in many aspects. Given the compositions of magnetic particles (MPs) with diverse characterizations and the innovative acoustic type of vibration sample magnetometer (VSM), the versatile, accessible magnetic diagnosis platform was proposed to meet clinical demands, such as low loading for multiple biopsies. In liquid biopsies of alpha-fetoprotein (AFP) standard solutions and subject serums, molecular concentration was analyzed from saturation magnetization by the soft type of Fe3O4 MPs with AFP bioprobe coating. In the phantom mixture simulated as bounded MPs in tissue, the bounded MPs was evaluated from the area of the hysteresis loop by hard type of cobalt MPs without bio-probes coating. Not only a calibration curve was founded for many hepatic cell carcinoma stages, but also microscale images verified the Ms increase due to magnetic protein clusters, etc. Hence, its wide populations in clinics could be expected.

Degeneracy and hysteresis in a bidisperse colloidal ice

We use numerical simulations to investigate the low-energy states of a bidisperse colloidal ice, realized by confining two types of magnetic particles into double wells of different lengths. For this system, theoretical calculations predict a highly degenerate ground state where all the vertices with zero topological charge have equal energy. When raising the applied field, we find a re-entrant transition where the system passes from the initial disordered state to a low-energy one and then back to disorder for large interaction strengths. The transition is due to the particle localization on top of the central hill of the double wells, as revealed from the position distributions. When we decrease the applied field, the system displays hysteresis in the fraction of low-energy vertices, and a small return point memory by cycling the applied field.

Magnetic water treatment in a wastewater treatment plant: Part II - Processing waters and kinetic study

Magnetic sorption process is applied to real wastewater effluents from a Wastewater Treatment Plant. The complex media sorption is done by using different types of magnetic particles (resin and polymeric covered magnetite) giving good results for removing detergents, phosphates and COD and moderate results for the sorption of nitrogen and several heavy metals. Important kinetic parameters were obtained by data fitting for the pseudo first and second order, and for simplified Elovich models. Regeneration and reuse of the magnetic particles using a chemical-free method was also tested, as well as the effect of the concentration of the particles in the removal efficiency (which proved to be relevant).

Shape anisotropic magnetic thrombolytic actuators: synthesis and systematic behavior study.

Thrombosis-related diseases are undoubtedly the deadliest disorders. During the last decades, numerous attempts were made to reduce the overall death rate and severe complications caused by treatment delays. Significant progress has been made in the development of nanostructured thrombolytics, especially magnetically controlled. The emergence of thrombolytic magnetic actuators, which can deliver tPA to the occlusion zone and perform mechanical disruption of the fibrin network under the application of a rotating magnetic field (RMF), can be considered for the next generation of thrombolytic drugs. Thus, we propose a systematic study of magnetic-field mediated mechanically-assisted thrombolysis (MFMMAT) for the first time. Four types of magnetic particles with different morphology and dimensionality were utilized to assess their impact on model clot lysis under different RMF parameters. Chain-like 1D and sea urchins-like 3D structures were found to be the most effective, increasing thrombolysis efficacy to nearly 200%. The drastic difference was also observed during the dissolution of 3 days old blood clots. Pure plasminogen activator had almost no effect on clot structure during 30 minutes of treatment while applying MFMMAT led to the significant decrease of clot area, thus uncovering the possibility of deep venous thrombosis therapy.

Influence of particles size and concentration of carbonyl iron powder on magnetorheological properties of silicone rubber-based magnetorheological elastomer

In this study, the anisotropic magnetorheological elastomer(MRE) was prepared by mixing two-component room temperature vulcanized(RTV) silicone rubber, carbonyl iron powder particles and dimethyl silicone oil uniformly, then heated and solidified under 500 mT magnetic field intensity. Five types of magnetic particles with different concentrations of 20%, 30%, 40%, 50%, 60% and five different sizes of 1.7, 2.8, 3.9, 4.6, 7.2 μm, were used to investigate the effects of the concentrations and sizes of the magnetic particles on the microstructure, mechanical properties and the magnetorheological effect (MR-effect) of anisotropic MREs. The results obtained from this study showed that the MR-effect has a significant dependence on the concentrations and particle sizes of the magnetic particles. It increased with the increase of the particle concentrations, and the high particle concentration makes the MRE have a high magnetostrictive modulus and MR-effect. Nevertheless, with the increase of the particle sizes, the MR-effect showed a trend of strengthening firstly and then weakening, there is an optimal particle size of 4.6 μm, at this size, the MR-effect is the most significant.

Magnetic Shape Memory Polymers with Integrated Multifunctional Shape Manipulation.

Shape-programmable soft materials that exhibit integrated multifunctional shape manipulations, including reprogrammable, untethered, fast, and reversible shape transformation and locking, are highly desirable for a plethora of applications, including soft robotics, morphing structures, and biomedical devices. Despite recent progress, it remains challenging to achieve multiple shape manipulations in one material system. Here, a novel magnetic shape memory polymer composite is reported to achieve this. The composite consists of two types of magnetic particles in an amorphous shape memory polymer matrix. The matrix softens via magnetic inductive heating of low-coercivity particles, and high-remanence particles with reprogrammable magnetization profiles drive the rapid and reversible shape change under actuation magnetic fields. Once cooled, the actuated shape can be locked. Additionally, varying the particle loadings for heating enables sequential actuation. The integrated multifunctional shape manipulations are further exploited for applications including soft magnetic grippers with large grabbing force, reconfigurable antennas, and sequential logic for computing.

3D printing of polymer-bonded magnets from highly concentrated, plate-like particle suspensions

This paper reports the 3D printing of polymer-bonded magnets using highly concentrated suspensions of non-spherical magnetic particles. In a previous study, magnets of arbitrary shapes have been successfully fabricated using the UV-Assisted Direct Write (UADW) method. The magnetic remanence (Br) of the UADW magnets was limited by the type of magnetic particles used and the highest printable particle loading. Magnetic particles produced from melt spinning have better intrinsic magnetic properties, but their plate-like shape has resulted in a higher working viscosity, posing a major challenge in 3D printing with UADW. Inspired by the “Farris effect” in rheology, we mixed the plate-like particles of two different sizes to increase the polydispersity and reduce the overall viscosity of the mixture as the smaller particles can now fill the interstitial space between the larger ones. Using this rheological technique, a particle loading of as high as 65% by volume, or 93% by weight, was 3D printed. The resulting magnet has a density of 5.2 g/cm3, an intrinsic coercivity (Hci) of 9.39 kOe, a remanence (Br) of 5.88 kG, and an energy product ((BH)max) of 7.26 MGOe, marking the highest values reported for 3D printed polymer-bonded magnets.

Fe-Cr-Nb-B ferromagnetic particles with shape anisotropy for cancer cell destruction by magneto-mechanical actuation

We introduce a new type of magnetic particles (MPs) prepared by wet milling of superferromagnetic Fe-Cr-Nb-B precursor glassy ribbons for cancer treatment by magneto-mechanical actuation in low magnetic fields (1 ÷ 20 Oe). The rectangular shapes of MPs and the superferromagnetism of the glassy alloys of which are made the MPs induce important magnetic shape anisotropies which, in association with a large saturation magnetization, generate an improved torque in a rotating magnetic field, producing important damages on the cellular viability of MG-63 human osteosarcoma (HOS) cells. The specific parameters such as MPs concentration, frequency and intensity of the applied magnetic field, or the time of exposure have a strong influence on the cancer cells viability. The specific behavior of the Fe-Cr-Nb-B MPs offers them destructive effect even in low magnetic fields such as 10 Oe, and this characteristic allows the use of coils systems which provide large experimental spaces. The novel MPs are used for the magneto-mechanical actuation alone or in association with hyperthermia, but also can be transported to the tumor sites by means of stem cells carriers.

Abstract 4585: Development of multi-marker capture and analysis of circulating tumor cells in renal cell carcinoma

Abstract Purpose: Circulating biomarkers are an emerging tool to monitor treatment response and the emergence of resistant phenotypes. However, studies of circulating biomarkers, including circulating tumor cells (CTCs), in patients with clear cell renal cell carcinoma (ccRCC) have been limited due to difficulty in biomarker identification. Platforms relying on EpCAM and cytokeratin to identify CTCs have been limited due to significant phenotypic and intrapatient heterogeneity in renal cancer. Carbonic anhydrase IX (CAIX) and XII (CAXII) are more broadly expressed in ccRCC and recently been shown to capture CTCs from patients with ccRCC. However, downregulation of these targets can also occur; EpCAM is also expressed on a subset of cells that could go undetected if only CAIX was used to capture these cells. The aim of this study is to optimize multi-marker capture and analysis of ccRCC CTCs using EpCAM, CAIX and CAXII for further molecular analysis. Methods: We utilized the VERSA platform, an integrated CTC capture and analysis technology, to optimize capture of multiple ccRCC cell lines using antibodies to CAIX and/or EpCAM. To maximize the capture efficiency of ccRCC CTCs, we altered the magnetic particle type, antibody concentration, and tested both direct and indirect capture methods. Once an optimal method of capture was determined, we captured CTCs in an initial cohort of ten patients with ccRCC. CTCs were identified as cells that were captured by either CAIX or EpCAM, had an intact nucleus, were negative for CD45/CD34/CD66b, and positive for cytokeratin. Results: Capture of cell lines show that a combined CAIX + EpCAM capture was more efficient than single antibody capture using either EpCAM or CAIX alone. The type of magnetic particle used in the assay also affected capture efficiency. Sera-Mag beads (GE Healthcare) captured significantly more cells than FlowComp Dynabeads (Life Technologies) (94% vs 76%). Further increases in efficiency were made by incubating with antibody prior to bead conjugation (indirect binding, 94%) when compared to incubating the cells with antibody-conjugated beads (direct binding, 98%). This may result from increased accessibility of free antibody to partially obstructed antigens that is unique to renal cell carcinoma. This optimized assay has now been applied to ccRCC patients and has identified CTCs in up to 90% of patients with metastatic disease. Conclusions: We have increased the capture efficiency and identification of ccRCC cells by capturing with a combination of CAIX and EpCAM antibodies and optimizing bead and binding conditions. In doing so, we are able to identify and interrogate populations of CTCs that would be lost in capture methods that rely on EpCAM alone. These assays are now being utilized in multiple biomarker and therapeutic trials for patients with clear cell renal cell carcinoma. Citation Format: Rory M. Bade, Benjamin K. Gibbs, Jamie M. Sperger, Christos Kyriakopolous, Hamid Emamekhoo, Rana R. McKay, Toni K. Choueiri, Joshua M. Lang. Development of multi-marker capture and analysis of circulating tumor cells in renal cell carcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 4585.

Sensitivity Enhancement in Capillary Electrophoresis Using Magnetic Particles as Solid-Phase Extraction Sorbents for the Determination of Drugs of Abuse in Urine.

Over the last few years, different types of magnetic particles have been investigated and successfully used in sample preparation, of which iron oxides are the most popular, due to their low price and low toxicity. For analytical purposes, these particles have always been modified and functionalized with different materials to improve their stability and introduce new surface properties. Here we describe the preparation of silica-coated iron oxide particles functionalized with C18 and their application as solid-phase extraction sorbents coupled in-line with capillary electrophoresis for determining drugs of abuse in human urine.

Modeling and measurement of curing properties of photocurable polymer containing magnetic particles and microcapsules

In microstereolithography, three-dimensional microstructures are created by scanning an ultraviolet laser on a photocurable resin and stacking several such layers to form the desired structure. By mixing different types of particles in the resin, the formed microstructures exhibit various physical properties. For example, the magnetism and density of the microstructure can be controlled by adding magnetic particles and microcapsules to the resin. This method has been used to fabricate magnetic micromachines. Although such functional resins are useful, the incorporated magnetic particles and microcapsules can affect the fabrication resolution, making it difficult to fabricate microstructures with high precision. Thus, it is necessary to understand the effects of such microparticles and microcapsules on the fabrication process. In this study, we propose a simple model of curing resins containing magnetic particles and microcapsules to explain the effects of the magnetic particles and microcapsules. The proposed model can explain the observed curing characteristics of a resin that contains particles for all concentrations as well as for different types of magnetic particles and microcapsules. Finally, using the proposed model, we discuss how to improve the characteristics of resins containing microparticles to realize the high-resolution fabrication of three-dimensional microstructures with desirable material properties.

Quantification of antibody coupled to magnetic particles by targeted mass spectrometry

Quantifying the amount of antibody on magnetic particles is a fundamental, but often overlooked step in the development of magnetic separation-based immunoaffinity enrichment procedures. In this work, a targeted mass spectrometry (MS)-based method was developed to directly measure the amount of antibody covalently bound to magnetic particles. Isotope-dilution liquid chromatography-tandem MS (ID-LC-MS/MS) has been extensively employed as a gold-standard method for protein quantification. Here, we demonstrate the utility of this methodology for evaluating different antibody coupling processes to magnetic particles of different dimensions. Synthesized magnetic nanoparticles and pre-functionalized microparticles activated with glutaraldehyde or epoxy surface groups were used as solid supports for antibody conjugation. The key steps in this quantitative approach involved an antibody-magnetic particle coupling process, a wash step to remove unreacted antibody, followed by an enzymatic digestion step (in situ with the magnetic particles) to release tryptic antibody peptides. Our results demonstrate that nanoparticles more efficiently bind antibody when compared to microparticles, which was expected due to the larger surface area per unit mass of the nanoparticles compared to the same mass of microparticles. This quantitative method is shown to be capable of accurately and directly measuring antibody bound to magnetic particles and is independent of the conjugation method or type of magnetic particle. Graphical Abstract Schematic illustration of the isotope-dilution mass spectrometry-based workflow to directly measure antibody bound to magnetic particles (MP).

Model FORC diagrams for hybrid magnetic elastomers

We propose a model of hybrid magnetic elastomers filled with a mixture of magnetically soft and magnetically hard microparticles. The magnetically hard particles are described by the Stoner–Wohlfarth model, the magnetically soft phase obeys the Fröhlich–Kennelly equation. The interaction between the two types of particles is described by the mean-field approach. First-order reversal curve (FORC) diagrams were calculated for different values of the elastomer matrix elasticity. We demonstrate that the diagrams display specific new features, which identify the presence of both a deformable matrix and the two types of magnetic particles.

Tunable Properties of Magnetoactive Elastomers for Biomedical Applications

The remote controllable magneto-mechanical devices based on MAEs (magnetoactive elastomers) can be obtained through variation of magnetic parameters of MAEs. Such devices can be used as the elements of peristaltic systems, artificial muscles, hyperthermia or drug delivery. MAEs with different matrix rigidity and filler particles type were investigated with VSM Lakeshore 7400 series and immittance meter Aktakom AM-3016 model. The dependencies of magnetostatic and magnetodynamic properties of MAEs with different types of magnetic particles on concentration of the magnetic filler and DC magnetic field strength were studied. There is a possibility to control the “magnetic hardness”, energy absorption and heating, relaxation properties of MAEs which allow to use MAEs as the main element of the tunable devices for biomedical applications.

Human regulatory T cell isolation in 55 minutes using EasySep™ Releasable RapidSpheres™ (TECH2P.912)

Abstract The preferred marker for identifying regulatory T cells (Tregs) is FOXP3 but its intracellular localization currently precludes it from being used for isolating viable cells. Human FOXP3+ Tregs are characterized as CD4+ T cells expressing high levels of CD25 and low levels of CD127. We have developed a novel immunomagnetic approach for the isolation of magnetic-particle-free human Tregs from PBMCs in as little as 55 minutes. This offers a vast improvement in speed over other immunomagnetic Treg isolation approaches, which typically require more than 2 hours. The standard approach for isolating Tregs combines CD4+ T cell negative enrichment followed by CD25 positive selection. By contrast, our novel approach is to first perform the CD25 positive selection step with EasySep™ Releasable RapidSpheres™, a new type of magnetic particle that can be rapidly released from the isolated cells with a no-incubation, no-wash protocol performed at room temperature. Subsequent depletion of CD127high and non-CD4+ T cells is achieved by negative enrichment with EasySep™ Dextran RapidSpheres™. Starting with 5x107 PBMCs, a purity of 87.6% ± 3.1% and recovery of 2.7x105 ± 8.2x104 Tregs (CD4+CD127lowCD25+FOXP3+) can be achieved (n=6). This is the first EasySep™ kit to incorporate the EasySep™ Releasable RapidSpheres™ and it exemplifies the potential of this technology for use in rapidly isolating magnetic particle-free cell populations possessing complex cell surface phenotypes.

Magnetic immunoassay based on frequency mixing magnetic detection and magnetic particles of different magnetic properties

A novel analytical system is presented that employs two different types of magnetic particles (MPs) with frequency mixing magnetic detection (FMMD).

A Rapid Assay to Measure the Shielding of Iron Oxide Cores by the Particle Shell

The conjugation of magnetic nano- and microparticles with biomolecules and its analysis very often require a dense coating of the iron oxide to prevent any reaction with redox-sensitive molecules or ions. The shielding of the iron oxide cores in different types of magnetic particles was compared by rapid assays that are based on the analysis of redox reactions. The oxidation of cysteine to the corresponding cysteine disulfide in the presence of incompletely covered iron oxide was analyzed with Ellman's reagent. Similar results were obtained by analysis of the reduction of copper (II) to copper(I) by the magnetite containing particles under the conditions of the Bicinchoninic Acid (BCA) assay. We show the assay results for different commercially available magnetic particles in the size range of 20 nm to 30 μm and conclude that an incomplete coverage of the iron oxide cores requires the comparison with reference particles in redox-sensitive assays, e.g., for the characterization of the protein coating or of the density of functional groups on the particle surface.

The effect of Fe3O4 nanoparticles on the thermal conductivities of various base fluids

Conventional heat transfer fluids have intrinsically poor heat transfer properties comparedto solids. Enhancing the efficiency of heat transfer is of great interest for various industrialapplications. Suspending solid particles in a fluid increases the thermal conductivity of theresulting suspension and enhances the heat transfer properties. In this work, changes in thermalconductivities of fluids upon the addition of magnetic nanoparticles have been investigated.Fe3O4 nanoparticles are synthesized using different synthesis methods and are suspended invarious oils. The effect of the base fluid and the type of magnetic particle on the thermalconductivity is investigated in detail. Up to 28% increase in the thermal conductivity isobtained with 2.5 wt% magnetic particles in hexane. The thermal conductivity enhancementis found to depend on the particle concentration, method of preparation and base fluid.The enhancements obtained are higher than those estimated using any theoretical modelpresent in the literature.

Positive contrast with therapeutic iron nanoparticles at 4.7 T

The purpose of the study was to show the feasibility of a positive contrast technique GRadient echo Acquisition for Superparamagnetic particles with Positive contrast (GRASP), for a specific type of magnetic particles, designed for tumor treatment under MRI monitoring. A simulation study was performed to estimate field inhomogeneity intensities induced by increasing concentrations of particles at different static fields. The GRASP sequence was setup on a 4.7 T Bruker system during an in vitro study. Six mice, included in the in vivo study received particles in the left calf muscle and contrast enhancement values, were measured over three time points, for both negative and positive contrast images. Comparing values obtained by simulation at 1.5, 3, and 4.7 T, the strongest susceptibility effect was obtained at 4.7 T. Based on simulation and in vitro data, gradient settings were chosen for in vivo imaging. GRASP resulted in bright regions at and around the injection site, and higher enhancement values, compared to standard GRE imaging. Both contrasts were useful for longitudinal follow-up, with a faster decay over time for GRASP. The magnetic nanoparticles for drug delivery can be detected using positive contrast. Combining imaging sequences, i.e., negative contrast and susceptibility methods, increased imaging specificity of large magnetic particles and enabled their follow-up for theranostic applications.