Magnetite Microparticles Research Articles

Enhancing Magnetic Micro- and Nanoparticle Separation with a Cost-Effective Microfluidic Device Fabricated by Laser Ablation of PMMA.

Superparamagnetic iron oxide micro- and nanoparticles have significant applications in biomedical and chemical engineering. This study presents the development and evaluation of a novel low-cost microfluidic device for the purification and hyperconcentration of these magnetic particles. The device, fabricated using laser ablation of polymethyl methacrylate (PMMA), leverages precise control over fluid dynamics to efficiently separate magnetic particles from non-magnetic ones. We assessed the device's performance through Multiphysics simulations and empirical tests, focusing on the separation of magnetite nanoparticles from blue carbon dots and magnetite microparticles from polystyrene microparticles at various total flow rates (TFRs). For nanoparticle separation, the device achieved a recall of up to 93.3 ± 4% and a precision of 95.9 ± 1.2% at an optimal TFR of 2 mL/h, significantly outperforming previous models, which only achieved a 50% recall. Microparticle separation demonstrated an accuracy of 98.1 ± 1% at a TFR of 2 mL/h in both simulations and experimental conditions. The Lagrangian model effectively captured the dynamics of magnetite microparticle separation from polystyrene microparticles, with close agreement between simulated and experimental results. Our findings underscore the device's robust capability in distinguishing between magnetic and non-magnetic particles at both micro- and nanoscales. This study highlights the potential of low-cost, non-cleanroom manufacturing techniques to produce high-performance microfluidic devices, thereby expanding their accessibility and applicability in various industrial and research settings. The integration of a continuous magnet, as opposed to segmented magnets in previous designs, was identified as a key factor in enhancing magnetic separation efficiency.

Improving the Anaerobic Digestion Process of Wine Lees by the Addition of Microparticles

Wine lee generation, a by-product of the wine industry, implies economic challenges for producers in terms of management due to its high organic load and low pH value. Biological treatment based on controlled anaerobic digestion may emerge as a viable management alternative given its promising potential for biogas production thanks to the organic content of the substrate. However, the complex properties of wine lees may lead to microbial activity inhibition and process kinetics failure. Various solutions have already been explored, including co-digestion with other substrates, or the application of different pretreatments, to mitigate the effects of the accumulation of phenolic compounds, volatile fatty acids, antioxidants, or the acidic pH value of the medium. In this study, laboratory-scale batch reactors were established, adding iron- (magnetite) or carbon (graphite)-based microparticles to assess their impact on the kinetics of the process. The results demonstrate a significant improvement of 35% in the potential production of biomethane after four days of operation with graphite particles and 42% after five days using magnetite particles. Methane production rates, as determined by the Gompertz model, were 45.38 and 46.54 mL CH4∙gVS−1∙d−1 for the application of graphite and magnetite microparticles to the medium, respectively, compared to the value of 33.46 mL CH4∙gVS−1∙d−1 for the control trial, confirming kinetic process improvements of 36% and 39%, respectively. Evidences of the acceleration of the methanogenesis phase were detected along the essays; however, the strong inhibition mediated by the carboxylate accumulation was not avoided in any of the tested conditions.

Analysis of Polycyclic Aromatic Hydrocarbons Using Magnetic Three-Dimensional Graphene Solid-Phase Extraction Coupled with Gas Chromatography–Mass Spectrometry

In this study, a composite material consisting of three-dimensional graphene aerogel and iron oxide nanoparticles (3DG/Fe3O4) was created and utilized for the purpose of magnetic solid-phase extraction (MSPE) of thirteen polycyclic aromatic hydrocarbon (PAH) compounds via gas chromatography–mass spectrometry/selected ion monitoring (GC-MS/SIM) analysis. The synthesized adsorbent underwent a range of characterization techniques, including scanning electron microscopy, vibrating sample magnetometry, Raman spectroscopy, X-ray diffraction, Brunauer–Emmett–Teller, Fourier transform-infrared spectroscopy, and Barrett–Joyner–Halenda techniques, to examine its properties and morphology. The synthesized adsorbent integrates the benefits of superior adsorption capacity from modified graphene oxide (GO) with the magnetic separability of magnetite microparticles, resulting in a high adsorption capacity with easy separation from sample solutions. The efficiency of the proposed method was optimized and modeled using a central composite design (CCD), which considered the primary factors influencing it. The optimal conditions were obtained as the adsorbent dosage of 10 mg, the extraction time of 4 min, and the salt concentration of 3% w/v. The limit of detection for the target PAHs was established to range from 0.016 to 0.2 ng mL−1 in optimal conditions, exhibiting a signal-to-noise ratio of 3. The linear dynamic range spanned from 5 to 100 ng mL−1, with determination coefficients (R2) ranging from 0.9913 to 0.9997. The intra- and inter-day precisions were calculated as relative standard deviations (RSDs) equal to 3.9% and 4.7%, respectively. The proposed method was successfully applied to the determination of PAHs in water samples (tap, river, and rainwater), and recoveries in the range of 71–110% (RSDs < 5.2%, n = 3) were obtained.

Synergies of pH-induced calcium phosphate precipitation and magnetic separation for energy-efficient harvesting of freshwater microalgae

Energy- and time-consuming concentration steps currently limit the industrial application of microalgae. Compared to state-of-the-art technologies, magnetic separation shows a high potential for efficient harvesting of microalgae. This study presents a novel approach to combine pH-induced calcium phosphate precipitation with cheap natural magnetite microparticles for magnetic separation of the freshwater microalgae Chlorella vulgaris. Harvesting efficiencies up to 98% were achieved at moderate pH and low particle and calcium phosphate concentrations in a model medium. However, cultivation-dependent high loads of algogenic organic matter can severely inhibit flocculation and particle/algae interactions, requiring higher salt concentrations or pH. Harvesting efficiencies above 90% were still attainable at moderate pH with increased calcium phosphate concentrations of 10mM. Acidification of the suspension to pH 5 allows for simple and reversible particle recycling. The presented process provides a promising path to universal and cost-effective harvesting, advancing the utilization of microalgae as a sustainable bioresource.

Field experiment pitting magnetite nanoparticles against microparticles: Effect of size in the rehabilitation of metalcontaminated soil

ABSTRACT A significant portion of the current knowledge regarding the use of iron nanoparticles for remediating metal-contaminated soils is derived from laboratory experiments, leaving several unanswered questions. This article presents a field experiment comparing the efficacy of magnetite nanoparticles and microparticles for the immobilization of metals and the growth of plants in metal-contaminated soils. This study aimed to investigate the effects of magnetite particle size on metal immobilization and plant growth in soils exposed to airborne pollution from the Middle-Urals Copper Smelter in the southern taiga subzone near Revda, Russia, 50 km from Ekaterinburg. Magnetite nano- and microparticles were added to forest litter at a 4 % w/w dose. The total metal contents in litter from the study plots were 1-2 orders of magnitude higher than background metal concentrations. The magnetite nanoparticle treatment was found to decrease the concentration of exchangeable copper in soil and improve the growth of red fescue (Festuca rubra L.) on polluted soil compared to the control. In contrast, magnetite microparticles did not show any statistically significant effects. These findings are in line with laboratory results that demonstrated the superior metal adsorption properties of magnetite nanoparticles compared to microparticles. However, this study was limited in duration (2 months), and longer field studies would be necessary to confirm the role of iron particle size in the rehabilitation of metal-contaminated soils.

Modelling of the deformation behaviour of a magnetic hydrogel in a magnetic field gradient

An ink made of alginate and methylcellulose with embedded magnetite microparticles was developed for extrusion printing. Constructs, so-called scaffolds, are colonised with cells which can be activated by mechanical stimulation. In this work, a defined magnetic field gradient is applied to achieve non-contact deformation. However, the deformation behaviour or relevant material parameters of the hybrid material are unknown. While the properties were determined with experiments adapted to hydrogels, a separate experimental set-up for micro-computed tomography, adapting the Maxwell configuration, was developed to investigate the deformation behaviour. These analyses were performed depending on ageing and particle concentration. For these tests, strands were used as bending beams, since these are simple and well known systems. Firstly, a model for the bending curve was erected, which defines a range in which the real bending curve would be expected. It was compared with the measured bending curves. There was very good agreement for the first days. On day 14, the measured bending curves were still within the calculated range, but at the lower limit due to the shortcomings of the model as the violation of the small deformations condition at this point. Secondly, the bending as a function of incubation duration was observed by a series of radiograms when a magnetic field gradient was applied. From this, a functional approach was formulated to describe the system response. Some parameters have already been identified, for others a proposal is given. Thirdly, microscopic analyses were carried out to observe the effects of the field gradient on particle distribution and structure. It was revealed that a homogeneous particle distribution was found even after 2.5 h. Also, in the direction of the field gradient, no chains were formed and no damage of the network could be detected. The obtained results show, that the material is suitable for mechanical stimulation.

Fluid-Assisted Aggregation and Assembly of Magnetite Microparticles in the Giant El Laco Iron Oxide Deposit, Central Andes

The El Laco iron oxide mineral deposit in the Central Andes of Chile has attracted significant attention because of its uniquely preserved massive magnetite orebodies, which bear a remarkable similarity to volcanic products. To date, the outcropping highly vesicular and porous massive magnetite orebodies have received little attention from a microtextural point of view, limiting our understanding about the role of volcanogenic processes on iron mineralization. Here, we report the chemical composition of vesicular magnetite at El Laco using EPMA and LA-ICP-MS methods and provide detailed 2D and 3D imaging of the internal structure of these texturally complex magnetite ores by combining SEM observations, synchrotron radiation micro-X-ray fluorescence chemical mapping, and high-resolution X-ray computed microtomography. Our observations reveal the presence of abundant magnetite microspheres with diameters ranging from ∼100 to ∼900 μm, as well as dendritic microstructures forming interconnected networks up to a few millimeters in size. Two-dimensional microtextural and geochemical imaging of the microspheres show that these features are formed by multiple euhedral magnetite crystals growing in all directions and occur immersed within a porous matrix conformed by smaller-sized (∼2–20 μm) and irregularly shaped magnetite microparticles. These types of morphologies have been reported in hydrothermal vents associated with hydrovolcanic processes and commonly described in hydrothermal synthesis experiments of magnetite microspheres, suggesting precipitation from iron-rich fluids. A hydrothermal origin for the magnetite microparticles reported here is further supported by their geochemical signature, which shows a strong depletion in most minor and trace elements typical from magnetite precipitated from hydrothermal fluids in ore-forming environments. We propose that decompression, cooling, and boiling of fluids triggered massive iron supersaturation, resulting in the nucleation of magnetite microparticles or colloids, followed by self-assembly into larger and more complex microstructures. Our data from El Laco deposit agree with models invoking magmatic-hydrothermal fluids to explain the origin of the deposit and provide new insights on the potential role of iron colloids as agents of mineralization in volcanic systems.

Mechanism for the Magnetorheological Effect of Nanocomposite Hydrogels with Magnetite Microparticles.

In a previous study, we presented an empirical law for the magnetorheological effect of nanocomposite hydrogels with magnetite microparticles derived from rheological data. In order to understand the underlying processes, we employ computed tomography for structure analysis. This allows the evaluation of the translational and rotational movement of the magnetic particles. Gels with 10% and 3.0% magnetic particle mass content are investigated at three degrees of swelling and at different magnetic flux densities in steady states by means of computed tomography. Since a temperature-controlled sample-chamber is difficult to implement in a tomographic setup, salt is used to deswell the gels instead. Based on the findings of the particle movement, we propose a mechanism using an energy-based approach. This leads to a theoretical law that shows the same scaling behavior as the previously found empirical law.

Empirical Law for the Magnetorheological Effect of Nanocomposite Hydrogels with Magnetite Microparticles.

Hydrogels are functional smart materials which can be tailored by modifying their chemical composition. Further functionalization can be achieved by incorporating magnetic particles into the gel matrix. In this study, a hydrogel with magnetite micro-particles is synthesized and characterized by rheological measurements. Inorganic clay is used as the crosslinking agent, which additionally prevents the sedimentation of the micro-particles during the synthesis of the gel. The mass fractions for the magnetite particles in the synthesized gels range from 10% to 60% in the initial state. Rheological measurements are performed in different degrees of swelling using temperature as a stimulus. The influence of a homogeneous magnetic field is analyzed by a step-wise activation and deactivation during dynamic mechanical analysis. For the evaluation of the magnetorheological effect in the steady states a procedure is developed, which takes occurring drift effects into account. Using the magnetic flux density, the particle volume fraction and the storage modulus as independent parameters, a general product approach is deployed for a regression analysis of the dataset. In the end, an empirical law for the magnetorheological effect in nanocomposite hydrogels can be found.

Structural investigation of Ayurveda Lauha (Iron) Bhasma

In Ayurveda, ‘Lauha’ (Iron) Bhasma is primarily used to cure diseases related to iron deficiency in humans. It is produced from purified raw metallic iron using a combination of multi-step traditional preparation processes described in the Ayurveda literature. Here, we present the results of structural investigation performed on the medicinal grade ‘Lauha’ Bhasma using various X-ray based techniques. Our results indicate that after several rounds of heating and cooling in specific conditions following the Ayurvedic preparation procedure, metallic iron eventually converts to a natural iron-oxide mineral belonging to the magnetite group. Scanning electron microscopy (SEM) and X-ray standing wave assisted fluorescence measurements carried out on powdered Bhasma specimen reveal that the magnetite micro-particles in the Bhasma specimen are usually present in the form of agglomerates of nano-particles. We anticipate that the Ayurvedic Lauha Bhasma has great potential for noninvasive localized target killing of cancer cells, particularly in sensitive parts of the human body such as the brain, spinal cord, and lungs, via necrosis by application of an alternating external magnetic field or photo electron generation through X-rays.

Nature inspired synthesis of magnetite nanoparticle aggregates from natural berthierine.

We investigate the origin of the magnetite nanoparticle aggregates (MNAs) from the Peña Colorada iron-ore mining district (Mexico) to devise a nature inspired synthesis process. Three types of samples were used: natural MNAs recovered from the mine, concentrated magnetite microparticles as reference material, and thin berthierine films used to synthesize MNAs. The chemical, mineralogical, crystallographic and rock magnetic properties were determined by polarized microscopy, high-resolution transmission electron microscopy, electron microprobe, X-ray diffraction, Mössbauer spectroscopy, and thermomagnetic and hysteresis measurements. MNAs were synthesized in the lab with the following steps. We start with berthierine thin films, which are heated to temperatures between 495 and 510 °C leading to formation of numerous stable magnetite nanocrystals. They grow at a temperature above 650 °C. Space restrictions lead to the formation of dense MNAs. Smaller MNAs, <200 nm, with a Curie temperature of 650 °C, shows superparamagnetic behavior. While larger MNAs, >7 μm, show Curie temperature of 578 °C and ferromagnetic behavior. Based on present observations, we suggest that MNAs in the Peña Colorada iron-ore formed in a marine environment, where berthierine formation was accelerated by Fe-rich hydrothermal springs that supplied iron and increased the temperature. Most notably, our laboratory experiments mimicked natural conditions and were able to successfully nucleate and grow magnetite nanoparticles which developed into MNAs. These MNAs were similar to those recovered from the Peña Colorada iron-ore deposit. This study, thus, provides a nature inspired method for synthesis of magnetite nanoparticles and its aggregates.

Magnetic amino-sulfonic dual sorbent for uranyl sorption from aqueous solutions – Influence of light irradiation on sorption properties

The association of magnetite microparticles with bi-functional amino-sulfonate polymer (obtained by condensation of guanidine and amino hydroxynaphthalene sulfonic acid, mediated by formaldehyde) allows synthesizing a magnetic composite sorbent (M−GANS). The sorbent bearing both amine and sulfonate groups is efficient for uranyl sorption at pH 4–5. The sorption isotherms are successfully fitted by the Temkin equation, while kinetics is controlled by the pseudo-first order rate equation. The sorption properties are increased by UV irradiation in terms of both sorption capacity (by 25 %, up to 1.25 mmol U g−1) and kinetics. The sorption occurs on both amine and sulfonate groups; the improvement in sorption properties under UV irradiation is tentatively assigned to the photo-reduction of uranyl species (mediated by magnetite particles and amine groups from polymer layer). The UV irradiation improves the selectivity of M−GANS for uranium against other metal ions, tested on both synthetic and real solutions. This improvement can be correlated to the higher propensity of uranyl to be photo-reduced compared with investigated competitor ions. The recycling of the sorbent was successfully tested for five successive cycles of sorption and desorption (stably complete): the loss in sorption performances is slightly reduced (less than 1.5 % at the fifth cycle) under UV irradiation compared with experiments performed under dark conditions (loss close to 4.2 %). The uranium peroxide precipitate obtained at the end of the treatment of acid leachate of ore shows higher purity when UV irradiation was applied.

A Simple Portable Magnetometer Based on Magnets and Hall-Effect Sensors Capable of Measuring Magnetic Properties

A magnetometer based on Hall effect sensors was developed using a 1020 steel base, two magnets (K&amp;J Magnetics, Pipersville, PA, USA), and two Hall effect sensors: MLX-90215 (Melexis Inc., San Jose, CA, USA) and AD-AD22151 (Analog Devices, Inc., Wilmington, MA, USA). Both sensors were assembled on an acrylic support and powered with a 5-volt battery. The readings can be taken using bench multimeters (HP 34401A or Iminipa ET-2042D). The magnetometer records magnetic hysteresis loop and saturation by applying a field of up to 0.33 T at room temperature. The device was tested using magnetic hysteresis data from samples of 99% pure nickel sphere and magnetite microparticles. A dipole magnetic model was used to obtain the moment of the samples. The sensor used for reading the induced magnetic field of the sample AD-AD22151 has a sensitivity can be adjusted from to 110 mV/mT. This device is cheap, versatile, and easy to build, and despite its low accuracy, when compared to commercial equipment, it can be useful in low-budget teaching and research laboratories.

Enhancement of Cerium Sorption onto Urea-Functionalized Magnetite Chitosan Microparticles by Sorbent Sulfonation-Application to Ore Leachate.

The recovery of strategic metals such as rare earth elements (REEs) requires the development of new sorbents with high sorption capacities and selectivity. The bi-functionality of sorbents showed a remarkable capacity for the enhancement of binding properties. This work compares the sorption properties of magnetic chitosan (MC, prepared by dispersion of hydrothermally precipitated magnetite microparticles (synthesized through Fe(II)/Fe(III) precursors) into chitosan solution and crosslinking with glutaraldehyde) with those of the urea derivative (MC-UR) and its sulfonated derivative (MC-UR/S) for cerium (as an example of REEs). The sorbents were characterized by FTIR, TGA, elemental analysis, SEM-EDX, TEM, VSM, and titration. In a second step, the effect of pH (optimum at pH 5), the uptake kinetics (fitted by the pseudo-first-order rate equation), the sorption isotherms (modeled by the Langmuir equation) are investigated. The successive modifications of magnetic chitosan increases the maximum sorption capacity from 0.28 to 0.845 and 1.25 mmol Ce g-1 (MC, MC-UR, and MC-UR/S, respectively). The bi-functionalization strongly increases the selectivity of the sorbent for Ce(III) through multi-component equimolar solutions (especially at pH 4). The functionalization notably increases the stability at recycling (for at least 5 cycles), using 0.2 M HCl for the complete desorption of cerium from the loaded sorbent. The bi-functionalized sorbent was successfully tested for the recovery of cerium from pre-treated acidic leachates, recovered from low-grade cerium-bearing Egyptian ore.

Size-Controllable Synthesis of Monodisperse Magnetite Microparticles Leading to Magnetically Tunable Colloidal Crystals

Colloidal crystals (CCs) are periodic arrays of monodisperse microparticles. Such CCs are very attractive as they can be potentially applicable as versatile photonic devices such as reflective displays, sensors, lasers, and so forth. In this article, we describe a promising methodology for synthesizing monodisperse magnetite microparticles whose diameters are controllable in the range of 100–200 nm only by adjusting the base concentration of the reaction solution. Moreover, monodisperse magnetite microparticles in aqueous suspensions spontaneously form the CC structures under an external magnetic field, leading to the appearance of Bragg reflection colors. The reflection peak can be blue-shifted from 730 nm to 570 nm by the increase in the external magnetic field from 28 mT to 220 mT. Moreover, the reflection properties of CCs in suspension depend on the microparticle concentration in suspension and the diameter of the magnetite microparticles. Both fine-control of microparticle diameter and investigation of magneto-optical properties of CCs would contribute to the technological developments in full-color reflective displays and sensors by utilizing these monodisperse magnetite microparticles.

CyMAD bioreactor: A cyclic magnetic actuation device for magnetically mediated mechanical stimulation of 3D bioprinted hydrogel scaffolds

Mechanical stimulation of bioprinted constructs can enhance the differentiation of cells within these scaffolds, such as driving chondrocytes towards cartilage tissue substitutes. In this study, a holistic approach is presented for designing and engineering a material-specific device based on a magnetic field setup using the Maxwell configuration for a touchless cyclic magnetic stimulation of (bioprinted) hydrogel scaffolds containing magnetic microparticles. We describe the entire development process, from the design of the magnetic field to the construction of the bioreactor and provide an evaluation of the calculation. Finally, an analysis of the distribution and orientation of the particles within the hydrogels and a cytocompatibility test after applying the intended stimulation regime were conducted. As a proof-of-principle, a model system in the shape of a cylindrical bending beam consisting of the established magnetisable bioink based on alginate, methylcellulose and magnetite microparticles (algMC + mag), was used instead of 3D printed, macroporous scaffolds of this material. Requirements for the dimensioning of the force, such as the Young's modulus, were determined experimentally. The magnetic field was calculated using the software Finite Element Method Magnetics (FEMM). The cyclic stimulation of the samples was performed over 14 days with a duration of 3 h per day. The aim was to achieve an elongation of up to 10%. The homogeneous particle distribution in stimulated and non-stimulated samples was proven via μCT and digital image processing (DIP). Even after applying a static magnetic field over 30 min, no structure formation such as chains or agglomeration of the magnetic particles were observed. The deformation behaviour defined as a shifted position of the neutral fibre (centre line of an object) during stimulation was measured via μCT and analysed using DIP. From these data, an elongation of approx. 9% was calculated for day 14. This elongation was achieved for both the stimulated samples and the control group without stimulation, which corresponds to the theoretically calculated value. The cytocompatibility of the bioink, scaffold environment and stimulation approach was demonstrated for bioprinted scaffolds with embedded human mesenchymal stem cells and chondrocytes. These findings proved the suitability and versatility of the bioreactor and the presented approach for stimulation experiments.

Synthesis and characterization of poly(styrene-co-divinylbenzene) and nanomagnetite structures

The use of iron oxide nanoparticles for the synthesis of adsorbents materials with application in contaminated water remediation is based on both their magnetic and adsorption properties. Poly(styrene-co-divinylbenzene) - Poly(Sty-co-DVB)microparticles are widely known for this use and the addition of magnetite comes to add magnetic properties, however it should not limit the functionalization processes for formation of cationic and/or anionic resins. Thus, there is a concern about the stability of magnetite in acidic environments, as required by the sulfonation process, for example. Furthermore, the synthesis of composites with magnetic nanoparticles is a challenge due to the strong magnetic dipole interactions between particles resulting from the high specific surface area, making them susceptible to aggregation. As well as oxidation during the synthesis process can compromise the structure of the initial magnetic material. In this sense, the present work validated processes for the synthesis of Poly(Sty-co-DVB)/magnetite microparticles that sought, as a final result, the incorporation of magnetite aiming to preserve its initial structural conformation. Thus, started from original synthesis method aimed at the production of Poly(Sty-co-DVB) microparticles without magnetite, to methods in which magnetite nanoparticles is added through two distinct processes, different regarding the use or not of oleic acid in its preparation.In this method article we show:•Combination of methods to preserve the structure of magnetite in the Poly(Sty-co-DVB)/magnetite composite.•Simple method of adding magnetite to the Poly(Sty-co-DVB)/magnetite composite synthesis process.•Magnetite treatment method with oleic acid in Poly(Sty-co-DVB)/magnetite composite synthesis.The samples were characterized using Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and Mössbauer spectroscopy to evaluate the chemical modifications that were introduced in the original synthesis method.

Magnetoimpedance Thin Film Sensor for Detecting of Stray Fields of Magnetic Particles in Blood Vessel.

Multilayered [FeNi (100 nm)/Cu (3 nm)]5/Cu (500 nm)/[Cu (3 nm)/[FeNi (100 nm)]5 structures were used as sensitive elements of the magnetoimpedance (MI) sensor prototype for model experiments of the detection of magnetic particles in blood vessel. Non-ferromagnetic cylindrical polymer rod with a small magnetic inclusion was used as a sample mimicking thrombus in a blood vessel. The polymer rod was made of epoxy resin with an inclusion of an epoxy composite containing 30% weight fraction of commercial magnetite microparticles. The position of the magnetic inclusion mimicking thrombus in the blood vessel was detected by the measurements of the stray magnetic fields of microparticles using MI element. Changes of the MI ratio in the presence of composite can be characterized by the shift and the decrease of the maximum value of the MI. We were able to detect the position of the magnetic composite sample mimicking thrombus in blood vessels. Comsol modeling was successfully used for the analysis of the obtained experimental results and the understanding of the origin the MI sensitivity in proposed configuration. We describe possible applications of studied configuration of MI detection for biomedical applications in the field of thrombus state evaluation and therapy.

Bioprinting of Magnetically Deformable Scaffolds

Mechanical stimulation of cells embedded in scaffolds is known to increase the cellular performance toward osteogenic or chondrogenic differentiation and tissue development. Three-dimensional bioplotting of magnetically deformable scaffolds enables the spatially defined distribution of magnetically inducible scaffold regions. In this study, a magnetic bioink based on alginate (alg, 3%) and methylcellulose (MC, 9%) with incorporated magnetite microparticles (25% w/w) was developed and characterized. The size and shape of particles were monitored via scanning electron microscopy and X-ray micro-computed tomography. Shear-thinning properties of the algMC ink were maintained after the addition of different concentrations of magnetite microparticles to the ink. Its viscosity proportionally increased with the added amount of magnetite, and so did the level of saturation magnetization as determined via vibrating sample magnetometry. The printability and shape fidelity of various shapes were evaluated, so that the final composition of algMC + 25% w/w magnetite was chosen. With application of this ink, cytocompatibility was proven in indirect cell culture and bioplotting experiments using a human mesenchymal stem cell line. Toward the deformation of cell-laden scaffolds to support cell differentiation in the future, radiography allowed the real-time monitoring of magnetically induced deformation of scaffolds of different pore architectures and scaffold orientations inside the magnetic field. Varying the strand distance and scaffold design will allow fine-tuning the degree of deformation in stimulatory experiments.

High Purity Magnetite Microparticles Directly Derived from Mill Scale via Hydrogen-Reduction Method

This study develops a fast and simple way to produce high purity magnetite (Fe3O4) microparticles from mill scale by using hydrogen reduction with the addition of vapour as a retarding agent. By optimising the reduction temperature and gas flow rate, the characterisations by X-ray diffractometry technique shown that the Fe3O4 fraction of over 93 wt.-% is shown at the reduction temperature of 550 – 650 oC with the flow rate of the 4.5-5.5 mol%H2 + Ar gas + H2O gas mixture from 100 – 200 ml/min. The highest Fe3O4 fraction of over 99 wt.-% can be achieved from the reduction with the mixed gas at 650 oC and the flow rate of 200 ml/min for 4 hour.