Superparamagnetic Particles Research Articles

Mathematical modeling of impulse response of viscous remanent magnetization

TEM survey under objects that containing superparamagnetic particles, the effects of magnetic viscosity can have a significant impact on the received signal. At present, such effects of magnetic viscosity are considered a nuisance, while some researchers point out that they contain useful information.The article presents a mathematical modeling of impulse response of viscous remanent magnetization. Using the lognormal particle distribution model, various impulse responses of the magnetization were modeled. The results of attempts to restore the distribution parameters and of model impulse responses are presented. An estimate of the effectiveness of the inversion of synthetic impulse responses is given.

The role of starch in nano-magnetite formation: A spectrometric and structural investigation

In the framework of pollutant sequestration by magnetic nano materials, this work focuses on the synthesis and the physico-chemical properties of starch functionalized nano magnetites. Nanoparticles were prepared by the Fe2+/Fe3+ coprecipitation method with increasing amount of starch in the synthesis medium (starch to iron mass ratio (R) in the range 0–10). Obtained materials were characterized by Transmission Electron Microscopy (TEM), Powder X-Ray Diffraction (PXRD), Raman, Fourier Transform Infrared (FTIR) and 57Fe Mössbauer spectroscopies, as well as by vibrating sample magnetometry. The presence of starch into the synthesis medium lowers magnetite crystallinity and increases the dispersion of the oxide particles. Both effects lead to fast relaxing superparamagnetic particles at RT for high R. The role of starch on nano-magnetite growth and stabilization is evidenced.

Three-dimensional MR Neurography of the Brachial Plexus: Vascular Suppression with Low-dose Ferumoxytol.

Background The efficacy of ferumoxytol, an ultrasmall superparamagnetic iron oxide particle for three-dimensional (3D) MR neurography, has yet to be evaluated. Purpose To evaluate the effects of low-dose ferumoxytol for vascular suppression and nerve visualization in 3D brachial plexus MR neurography as a pilot study. Materials and Methods Volunteers without anemia were prospectively enrolled in July 2021. Brachial plexus MR neurography was performed 30 minutes following infusion of 25% of the standard (510 mg of iron) therapeutic ferumoxytol dose with use of a 3D short-tau inversion recovery T2-weighted fast spin-echo sequence. The 3D fast spin-echo was acquired with and without the use of additional flow suppression techniques. Two musculoskeletal radiologists qualitatively evaluated examinations for the degree of vascular suppression (0-3, none to complete), nerve visualization (0-2, none to full), and motion artifact (0-4, none to severe). Nerve-to-fat, muscle, or vessel contrast ratios were calculated with use of manually drawn regions of interests. Comparisons of the proportion of scans with adequate image quality (vascular suppression, 3; nerve visualization, 1, 2; motion artifacts, 0, 1) were made with use of the McNemar test. Comparisons of quantitative contrast ratios were performed with use of Wilcoxon signed rank tests. P < .05 was deemed statistically significant. Results There were 12 volunteers (mean age, 25 years ± 3; six women) evaluated. The scans with adequate vascular suppression increased from 0% to 98% with and without ferumoxytol, respectively (P < .001). All individual nerve assessments of adequate nerve visualization increased from 4%-63% to 36%-100% without and with ferumoxytol, respectively (P < .001-.010), while motion artifacts were unchanged (from 33% to 52%, P = .212). Quantitatively, nerve-to-vessel contrast ratios increased from 0.6 without to 7.6 with ferumoxytol (P < .001). The addition of flow suppression did not change nerve-to-vessel contrast ratio quantitatively (from 7.5 to 8.4, P > .99) following ferumoxytol. Conclusion Low-dose ferumoxytol improved vascular suppression and nerve visualization in three-dimensional MR neurography of the brachial plexus compared to imaging without ferumoxytol. © RSNA, 2022.

Three-dimensional close-to-substrate trajectories of magnetic microparticles in dynamically changing magnetic field landscapes

The transport of magnetic particles (MPs) by dynamic magnetic field landscapes (MFLs) using magnetically patterned substrates is promising for the development of Lab-on-a-chip (LOC) systems. The inherent close-to-substrate MP motion is sensitive to changing particle–substrate interactions. Thus, the detection of a modified particle–substrate separation distance caused by surface binding of an analyte is expected to be a promising probe in analytics and diagnostics. Here, we present an essential prerequisite for such an application, namely the label-free quantitative experimental determination of the three-dimensional trajectories of superparamagnetic particles (SPPs) transported by a dynamically changing MFL. The evaluation of defocused SPP images from optical bright-field microscopy revealed a “hopping”-like motion of the magnetic particles, previously predicted by theory, additionally allowing a quantification of maximum jump heights. As our findings pave the way towards precise determination of particle–substrate separations, they bear deep implications for future LOC detection schemes using only optical microscopy.

Dynamic Magnetic Excitation Detection Method for Low-Concentration Superparamagnetic Particles via Quartz Crystal Microbalance

Magnetic biomarker detection and monitoring at low concentrations are critical for the early diagnosis of many diseases and for accurately identifying specific biomolecules. Previously reported highly sensitive detection methods rely on magnetic sensors to detect the stray fields of magnetic labels (usually magnetic beads). The random noise generated by the Brownian motion of magnetic beads in solution makes it difficult to reduce further the limit of detection (LOD) of this measurement. Therefore, we propose a low-concentration magnetic beads sensor and a dynamic magnetic excitation detection method. The intensity of magnetization motion under the ac excitation magnetic field detected by the quartz crystal microbalance (QCM) realizes the measurement of the magnetic bead concentration in the solution. The experimental results show that the LOD of the proposed sensor in <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2.8~\mu \text{m}$ </tex-math></inline-formula> magnetic bead solution is 10 ng/mL and displays an approximate linear detection characteristic in the range of 20–100 ng/mL. The intensity of magnetization detected by QCM has an approximately linear relationship with the magnetic bead concentration. Given the wide application of magnetic-labeled biomolecule detection and its huge application prospects in early disease detection and precision medicine, this method provides an inexpensive, fast, and flexible detection technology for the general labeling analysis of magnetic labels in biomolecule detection.

42 (PB-042) Poster - Comparison of Technetium (Tc)- and SPIO-guided Sentinel Lymph Node Biopsy (SLNB) in Patients with Neoadjuvant Chemotherapy in Early Breast Cancer – first retrospective data

Background: Super-paramagnetic iron oxide particle (SPIO)-techniques are reasonable alternatives to Technetium-(Tc)-localization of SLNB/TAD in early breast cancer with a similar detection rate but superiority in logistics. These results have to be confirmed in a neoadjuvant setting (PST).

Biomimetic Magnetic Particles for the Removal of Gram-Positive Bacteria and Lipoteichoic Acid.

Gram+ bacteria are very common in clinical medicine and responsible for a large number of infectious diseases. For example, Gram+ bacteria play a major role in causing bloodstream infections and sepsis. Therefore, the detection of Gram+ bacteria is of great importance for the diagnosis and treatment of infectious diseases. Furthermore, these bacteria are often present in biofilms that cover implants. Recent research work has mainly focused on the biologic activity and removal of Gram-negative bacteria or bacterial components such as lipopolysaccharides (LPS). In contrast, the effects of lipoteichoic acid (LTA) have been less well studied so the relevance of their removal from body fluids is possibly underestimated. To address this topic, we evaluated superparamagnetic iron oxide particles (SPION) carrying different peptides derived from the innate immune receptor (GP-340) for their ability to bind and remove Gram+ bacteria and LTA from different media. Our results show that, beyond S. aureus, effective agglutinating and removing of S. pneumoniae was possible. Furthermore, we were able to show for the first time that this was possible with LTA alone and that the magnetic removal of bacteria was also efficient under flow conditions. We also found that this method was able to capture Stapyhylococcus aureus from platelet concentrates, which can help to enhance the sensitivity of microbiological diagnostics, quality control measures, and blood product safety.

Drops deformation influence on the microwaves interaction with a magnetodielectric emulsion

Experimental and theoretical studies of the interaction of microwave radiation with a frequency of 8.2 GHz with magnetodielectric emulsions under the influence of an external magnetic field causing deformation of the emulsion dispersed phase droplets have been carried out. The values of the external magnetic field strength are such that no ferromagnetic resonance is observed in the system at a given radiation frequency. The studies were carried out when a rectangular waveguide was partially filled with a sample cell in the form of a thin plate. It is established that the deformation of magnetic droplets of the emulsion significantly affects the absorption of electromagnetic energy. The value of the droplet concentration at which the maximum response of the system is observed is determined. The features of the phenomenon of nonreciprocal phase shift, which have no analogue in solid-state magnetic materials, are found. To interpret the results obtained, a model of an ensemble of non-interacting isotropic superparamagnetic particles was used.

Development and assessment of magnetic Fe2O3@MOF-74 composite sorbents for ethylene/ethane separation

Development of smart sorbents that can be regenerated when triggered by external stimuli such as magnetic field can overcome the poor energy utilization of the current sorbents investigated for light olefins/paraffins separation. In this work, we report the development of novel magnetic sorbents comprising of MOF-74 crystals and superparamagnetic Fe2O3 particles in a core–shell structure, and assessment of their C2H4/C2H6 separation performance. The electromagnetic properties of the materials were tuned by varying the Fe2O3 (Fex) loading (x = 1–20 wt%), and their effects on adsorption capacity, selectivity, and desorption rates were systematically investigated. The surface area, microporosity, and the C2H4/C2H6 selectivity of composites were reduced as the Fex content increased, while the specific heat absorption rate (SAR) was increased from 60 to 80 % upon varying the magnetic field intensity from 12.6 to 31.4 mT. On the basis of the SAR enhancement upon increasing the Fex loading, the C2H4 desorption rates were gradually increased with Fex up to 10 wt%, however beyond this composition a decline in the desorption rates was noted. Moreover, the cooling rate was found to be ∼76 % higher in induction heating compared to the conventional thermal heating method, which is expected to significantly shorten the cycle time, thereby reducing the column size and improving the throughput of the system. Our results highlight the importance of assessing the trade-offs between capture capacity and extent of responsiveness to magnetic field (i.e., temperature rise during regeneration) when developing smart sorbents. This work builds on previous studies that demonstrate the suitability of novel stimuli-responsive sorbents for next generation of olefin/paraffin separation systems.

Tracking of Stem Cells from Human Exfoliated Deciduous Teeth Labeled with Molday ION Rhodamine-B during Periodontal Bone Regeneration in Rats.

Chronic periodontitis can lead to alveolar bone resorption and eventually tooth loss. Stem cells from exfoliated deciduous teeth (SHED) are appropriate bone regeneration seed cells. To track the survival, migration, and differentiation of the transplanted SHED, we used super paramagnetic iron oxide particles (SPIO) Molday ION Rhodamine-B (MIRB) to label and monitor the transplanted cells while repairing periodontal bone defects. We determined an appropriate dose of MIRB for labeling SHED by examining the growth and osteogenic differentiation of labeled SHED. Finally, SHED was labeled with 25 μg Fe/ml MIRB before being transplanted into rats. Magnetic resonance imaging was used to track SHED survival and migration in vivo due to a low-intensity signal artifact caused by MIRB. HE and immunohistochemical analyses revealed that both MIRB-labeled and unlabeled SHED could promote periodontal bone regeneration. The colocalization of hNUC and MIRB demonstrated that SHED transplanted into rats could survive in vivo. Furthermore, some MIRB-positive cells expressed the osteoblast and osteocyte markers OCN and DMP1, respectively. Enzyme-linked immunosorbent assay revealed that SHED could secrete protein factors, such as IGF-1, OCN, ALP, IL-4, VEGF, and bFGF, which promote bone regeneration. Immunofluorescence staining revealed that the transplanted SHED was surrounded by a large number of host-derived Runx2- and Col II-positive cells that played important roles in the bone healing process. SHED could promote periodontal bone regeneration in rats, and the survival of SHED could be tracked in vivo by labeling them with MIRB. SHED are likely to promote bone healing through both direct differentiation and paracrine mechanisms.

In silico simulation and in vitro validation of a continuous microfluidic device for separation of magnetic nanoparticles

Magnetic separation is introduced to separate paramagnetic or superparamagnetic particles and beads from a suspension by implementing an external magnetic field gradient. The strength of this magnetic field declines with rising distance. Batch containers commonly separate nanoparticles from a fluid by imposing an external magnetic field gradient using a permanent magnet. In this system, magnetic particles aggregate the container's wall or bottom, therefore creating a continuous process without any aggregation is desired. In this paper, COMSOL Multiphysics ver. 5.6 (FEM) has been utilized to simulate a continuous microfluidic device with two geometrical designs, linear design (LD) and curved design (CD). The variables are the velocity of the primary fluid and buffer and the channel's width. The optimal designs of both microfluidic devices have been achieved by changing the variables in a specific range without aggregating them to the device's wall. The optimal structures for both designs were built and tested in the laboratory. The optimal velocity was 0.1 mm/s, the optimal channel width was 200 µm for LD, and it was 0.1 mm/s and 400 µm for CD, respectively. The separation percentage in the simulation was 63 %, the spectrophotometry result was 64.08 for LD, and CD showed better results in simulation (85 %) and laboratory experiment (80.24 %). So, this method can be used to optimize nanoparticle separation in microfluidic.

Influence of Experimental Conditions during Synthesis on the Physicochemical Properties of the SPION/Hydroxyapatite Nanocomposite for Magnetic Hyperthermia Application

In this work, we report on the fabrication of nanocomposites based on superparamagnetic iron oxide nanoparticles (SPIONs) in combination with hydroxyapatite (HAp) as a platform for drug delivery and magnetic hyperthermia application. First, the influence of experimental conditions such as co-precipitant, bath temperature, and pH on the morphology and magnetic properties of SPIONs was investigated. Then, the superparamagnetic particles were coated with the hydroxyapatite layer for further loading of anticancer drugs, determining the optimal thickness of the HAp shell. The composite was fabricated by the wet chemical process and was characterized by optimizing the experimental conditions of the wiring synthesis to obtain the superparamagnetic spherical material with a high HAp loading as a platform for drug uptake. SEM and TEM studies confirmed the round shape of the magnetic core up to 15 nm in size with a well-defined HAp shell. After checking the material’s superparamagnetic properties, the temperature dependence on time and alternating magnetic field strength was tested and optimized in hyperthermia experiments.

Abundance and characteristics of sediment-bound magnetic minerals and trace elements in karst ditch wetland: A case study from Guizhou Province, China

This study investigated sediment-bound magnetic properties and selected trace elements level in the karst ditch wetland, Caohai National Nature Reserve, Guizhou Province, China. Sediment-bound magnetic signals were quantified using low-frequency mass magnetic susceptibility (χLF), anhysteretic remanent magnetization susceptibility (χARM), saturation isothermal remanent magnetization (SIRM), and percentage frequency-dependent susceptibility (χfd%). Concentrations of Cd, Cr, Sb and Zn were determined using inductively coupled plasma mass spectrometry. Sediment χLF, χARM, SIRM, and χfd% were higher than those of bedrocks and mainly altered by the pedogenic processes. The estimated χfd% ranged from 6.15 % to 14.62 % and reflected the magnetic grain sizes were largely concentrated in the range of superparamagnetic particles. The elevated concentrations of sediment-bound Cd, Cr, Sb, and Zn supported the significant contribution of the anthropogenic sources in the karst ditch wetlands. The weak relationship between magnetic signals and selected trace elements (p < 0.05) suggested the occurrence of few sediment-bound iron-containing minerals associated with selected trace elements. These results indicated that a minor contribution of anthropogenic sources of selected trace elements to the elevated sediment magnetic signals in the karst ditch wetlands.

Quantification and 3D Localization of Magnetically Navigated Superparamagnetic Particles Using MRI in Phantom and Swine Chemoembolization Models.

Superparamagnetic nanoparticles (SPIONs) can be combined with tumor chemoembolization agents to form magnetic drug-eluting beads (MDEBs), which are navigated magnetically in the MRI scanner through the vascular system. We aim to develop a method to accurately quantify and localize these particles and to validate the method in phantoms and swine models. MDEBs were made of Fe3O4 SPIONs. After injected known numbers of MDEBs, susceptibility artifacts in three-dimensional (3D) volumetric interpolated breath-hold examination (VIBE) sequences were acquired in glass and Polyvinyl alcohol (PVA) phantoms, and two living swine. Image processing of VIBE images provided the volume relationship between MDEBs and their artifact at different VIBE acquisitions and post-processing parameters. Simulated hepatic-artery embolization was performed in vivo with an MRI-conditional magnetic-injection system, using the volume relationship to locate and quantify MDEB distribution. Individual MDEBs were spatially identified, and their artifacts quantified, showing no correlation with magnetic-field orientation or sequence bandwidth, but exhibiting a relationship with echo time and providing a linear volume relationship. Two MDEB aggregates were magnetically steered into desired liver regions while the other 19 had no steering, and 25 aggregates were injected into another swine without steering. The MDEBs were spatially identified and the volume relationship showed accuracy in assessing the number of the MDEBs, with small errors (≤ 8.8%). MDEBs were able to be steered into desired body regions and then localized using 3D VIBE sequences. The resulting volume relationship was linear, robust, and allowed for quantitative analysis of the MDEB distribution.

Visualization of Inflammation in Experimental Colitis by Magnetic Resonance Imaging Using Very Small Superparamagnetic Iron Oxide Particles.

Inflammatory bowel diseases (IBD) comprise mainly ulcerative colitis (UC) and Crohn´s disease (CD). Both forms present with a chronic inflammation of the (gastro) intestinal tract, which induces excessive changes in the composition of the associated extracellular matrix (ECM). In UC, the inflammation is limited to the colon, whereas it can occur throughout the entire gastrointestinal tract in CD. Tools for early diagnosis of IBD are still very limited and highly invasive and measures for standardized evaluation of structural changes are scarce. To investigate an efficient non-invasive way of diagnosing intestinal inflammation and early changes of the ECM, very small superparamagnetic iron oxide nanoparticles (VSOPs) in magnetic resonance imaging (MRI) were applied in two mouse models of experimental colitis: the dextran sulfate sodium (DSS)-induced colitis and the transfer model of colitis. For further validation of ECM changes and inflammation, tissue sections were analyzed by immunohistochemistry. For in depth ex-vivo investigation of VSOPs localization within the tissue, Europium-doped VSOPs served to visualize the contrast agent by imaging mass cytometry (IMC). VSOPs accumulation in the inflamed colon wall of DSS-induced colitis mice was visualized in T2* weighted MRI scans. Components of the ECM, especially the hyaluronic acid content, were found to influence VSOPs binding. Using IMC, co-localization of VSOPs with macrophages and endothelial cells in colon tissue was shown. In contrast to the DSS model, colonic inflammation could not be visualized with VSOP-enhanced MRI in transfer colitis. VSOPs present a potential contrast agent for contrast-enhanced MRI to detect intestinal inflammation in mice at an early stage and in a less invasive manner depending on hyaluronic acid content.

Ultrasmall Superparamagnetic Particles of Iron Oxide and Cardiac Magnetic Resonance: Novel Imaging in Everyday Conditions

Myocardial inflammation has been hypothesised to be the common underlying mechanism through which several cardiovascular diseases develop and progress. Cardiac magnetic resonance (CMR) has become a powerful non-invasive tool that enables the direct visualisation of the myocardium. The emerging use of ultrasmall superparamagnetic particles of iron oxide (USPIO) and their magnetic properties is gaining a lot of research interest. USPIO-enhanced CMR can provide valuable information, as it allows for the identification of active inflammation in the myocardium, a process that has been hypothesised to be the substrate for adverse remodelling and, eventually, heart failure. In this review, we summarise the properties of USPIO and their role in cardiac magnetic resonance imaging as well as their clinical applications.

Magnetic granulometry, Mössbauer spectroscopy, and theoretical modeling of magnetic states of FemOn–Fem-xTixOn composites

FemOn–Fem–xTixOn composites, complex iron oxides doped with titanium, have been synthesized by coprecipitation (Cp series) or precipitation on preliminarily obtained magnetic particles (P series) followed by hydro- or solvothermal treatment. The results of magnetometry, scanning electron microscopy, X-ray diffraction, X-ray fluorescence, X-ray photoelectron and Mössbauer spectroscopy reveal the presence of three main fractions: chemically inhomogeneous strongly magnetic particles (maghemite/magnetite-titanomagnetite), weakly magnetic particles (hematite, goethite and possibly other iron hydroxides) and superparamagnetic particles belonging to the first two fractions. Samples of the Cp series where magnetically stable particles dominate are clearly distinct from the P series, which is dominated by superparamagnetic particles. Theoretical estimations of the hysteresis characteristics based on the model of magnetostatically interacting two-phase particles are in the best agreement with the experimental data at characteristic particle sizes of 60 nm for the Cp series and 13 nm for the P series.

Combined dynamics of magnetization and particle rotation of a suspended superparamagnetic particle in the presence of an orienting field: Semi-analytical and numerical solution

The magnetization dynamics of suspended superparamagnetic particles is governed by internal Néel relaxation as well as Brownian diffusion of the whole particle. We here present semi-analytical and numerical solutions of the kinetic equation, describing the combined rotation of particle orientation and magnetization. The solutions are based on an expansion of the joint probability density into a complete set of bipolar harmonics, leading to a coupled set of ordinary differential equations for the expansion coefficients. Extending previous works, we discuss the spectrum of relaxation times as well as convergence and limits of applicability of the method. Furthermore, we also provide the numerical scheme in electronic form, so that readers can readily implement and use the model.

Preparation of fluorescent bimodal probe coupled with ultra-small superparamagnetic iron oxide particles

To prepare USPIO-PEG-Cy5.5 targeted bimodal probe for noninvasive diagnosis of thyroid cancer. The characterization was verified, and the physical and chemical properties were discussed. Fe3O4 was used as the carrier. Fluorescent Cy5.5 was linked with polyethylene glycol (PEG). A small amount of Cy5.5-NHS fluorescent powder were dissolved in dimethyl sulfoxide solution. PEG-Fe3O4 nanoparticles were centrifuged and ultra-filtrated. The nanoparticles were resuspended with phosphate buffer to change the pH. The Cy5.5 fluorescence was added to the Fe3O4 particles and incubated at 37 °C for 2 h. Characterization test of Cy5.5-PEG-Fe3O4 and relaxation rate measurement were performed. Fro cells were used to perform cell imaging experiment. CCK-8 assay was carried out to detect the cytotoxicity. The bimodal molecular probe Cy5.5-PEG-Fe3O4 was synthesized successfully. Transmission electron microscopy showed that the particle size of the probe was 18.8 ± 3.5 nm, the water and particle size of the nanoparticles was 35.7 ± 18.6 nm, and the zeta potential was −18.0 mv. The relaxation rate was 0.044 and the slope was 0.97. The cytotoxicity test showed that the bimodal molecular probe had slight toxicity to fro cells with a concentration-dependent manner. The synthesized Cy5.5-PEG-Fe3O4 probe has low toxicity, good biocompatibility, stable particle size, which can be used for cell imaging for noninvasive diagnosis of thyroid cancer.

Locomotion of magnetoelastic membranes in viscous fluids

The development of multifunctional and biocompatible microrobots for biomedical applications relies on achieving controllable locomotion. Here we describe the conditions that allow homogeneous magnetoelastic membranes composed of superparamagnetic particles to swim through viscous fluids. By solving the equations of motion, we find the dynamical modes of circular membranes in precessing magnetic fields, which are found to actuate in or out of synchronization with a magnetic field precessing above or below a critical precession frequency ${\ensuremath{\omega}}_{c}$, respectively. For frequencies larger than ${\ensuremath{\omega}}_{c}$, synchronized transverse waves propagate on the membrane along the rotational (perimeter) and radial directions. Using the lattice Boltzmann approach, we show how these waves give rise to locomotion in an incompressible fluid at low Reynolds numbers. Nonreciprocal motion resulting in swimming is achieved by breaking the morphological symmetry of the membrane, attained via truncation of a circular segment. The membrane translation can be adapted to a predetermined path by programming the external magnetic field. Our results lay the foundation for achieving directed motion in thin, homogeneous magnetoelastic membranes with a diverse array of geometries.