Magnetic Holder Research Articles

Detection of plasma MMP-9 within minutes. Unveiling some of the clues to develop fast and simple electrochemical magneto-immunosensors

Magnetic beads (MB) have been extensively used to produce sensitive and efficient electrochemical magneto-immunosensors. However, MB effective handling requires training, and MB washing after each incubation step is time consuming and contributes to raise result variability. Consequently, most of the electrochemical magneto-immunosensors reported to date, which entailed relatively long and complex multi-step procedures, would be difficult to carry out at point-of-care (POC) settings or by laypersons. For this reason, here we targeted the development of a simplified detection path, which is fast and simple enough to be operated at a POC setting, sufficiently efficient to provide analyte quantitation comparable to classical diagnostic methods, and dependent on minimal technical requirements to facilitate method global exploitation. As a proof-of-concept, we optimized an extremely simple, fast and efficient electrochemical magneto-immunosensor for detection of matrix metalloproteinase 9 (MMP-9). To accomplish this, we optimized MB immunomodification, produced an immunomodified Poly-HRP signal amplifier, developed a single-step magneto-immunoassay, and optimized electrochemical detection using a multiplexed magnetic holder and a ready-to-use commercial substrate solution. The sensor was finally calibrated by detecting MMP-9 in clinical samples. This electrochemical magneto-immunosensor detected MMP-9 in just 12–15 min, displaying linear response between 0.03 and 2 ng mL−1 of MMP-9, limits of detection (LOD) and quantification (LOQ) of 13 pg mL−1 and 70 pg mL−1, respectively, %CV< 6%, and accurate quantification of MMP-9 in patient plasma samples. These results were comparable to those afforded by a 5-h reference ELISA that used the same antibodies, confirming the applicability of our simplified method.

An improved design to capture magnetic microparticles for capillary electrophoresis based immobilized microenzyme reactors.

In this paper, we demonstrate the effectiveness of a new 3D printed magnet holder that enables capture of magnetic microparticles in commercially available capillary electrophoresis equipment with a liquid or air based coolant system. The design as well as the method to capture magnetic microparticles inside the capillary are discussed. This setup was tested at temperature and pH values suitable for performing enzymatic reactions. To demonstrate its applicability in CE- immobilized microenzyme reactors (IMER) development, human flavin-containing monooxygenase 3 and bovine serum albumin were immobilized on amino functionalized magnetic microparticles using glutaraldehyde. These microparticles were subsequently used to perform in-line capillary electrophoresis with clozapine as a model substrate. This setup could be used further to establish CE-IMERs of other drug metabolic enzymes in a commercially available liquid based capillary coolant system. The CE-IMER setup was successful, although a subsequent decrease in enzyme activity was observed on repeated runs.

Stimulation map for control of functional grasp based on multi-channel EMG recordings

Transcutaneous activation of muscles with electrical stimulation has limited selectivity in recruiting paralyzed muscles in stroke patients. However, the selectivity could be increased by the application of smaller electrodes and their appropriate positioning on the skin. We developed a method for selecting the appropriate positions of the stimulating electrodes based on electromyography (EMG). The EMG activity maps were estimated from signals recorded with two electrode arrays and two 24-channel wearable amplifiers positioned on the nonparetic and paretic forearms. The areas where the difference between the EMG maps obtained from the nonparetic and paretic arms was significant were identified as the stimulation sites. The stimulation was applied through array electrodes with magnetic holders and two wearable stimulators with four output channels each. The measures of functionality included joint angles measured with goniometers (hand opening) and grasp force measured with a multi-contact dynamometer (grasping). The stimulation protocol comprised co-activation of flexors and extensors to stabilize the wrist joint and prevent pronation/supination.

Electromagnetic energy harvester for harvesting acoustic energy

This paper reports a suspended coil, electromagnetic acoustic energy harvester (AEH) for extracting acoustical energy. The developed AEH comprises Helmholtz resonator (HR), a wound coil bonded to a flexible membrane and a permanent magnet placed in a magnet holder. The harvester’s performance is analyzed under different sound pressure levels (SPLs) both in laboratory and in real environment. In laboratory, when connected to 50 Ω load resistance and subjected to an SPL of 100 dB, the AEH generated a peak load voltage of 198.7 mV at the resonant frequency of 319 Hz. When working under the optimum load resistance, the AEH generated an optimum load power of 789.65 µW. In real environment, the developed AEH produced a maximum voltage of 25 mV when exposed to the acoustic noise of a motorcycle and generated an optimum voltage of 60 mV when it is placed in the surroundings of a domestic electrical generator.

Passive radiative cooling of a HTS coil for attitude orbit control in micro-spacecraft

This paper proposes a novel radiative cooling system for a high temperature superconducting (HTS) coil for an attitude orbit control system in nano- and micro-spacecraft missions. These days, nano-spacecraft (1–10kg) and micro-spacecraft (10–100kg) provide space access to a broader range of spacecraft developers and attract interest as space development applications. In planetary and high earth orbits, most previous standard-size spacecraft used thrusters for their attitude and orbit control, which are not available for nano- and micro-spacecraft missions because of the strict power consumption, space, and weight constraints. This paper considers orbit and attitude control methods that use a superconducting coil, which interacts with on-orbit space plasmas and creates a propulsion force. Because these spacecraft cannot use an active cooling system for the superconducting coil because of their mass and power consumption constraints, this paper proposes the utilization of a passive radiative cooling system, in which the superconducting coil is thermally connected to the 3K cosmic background radiation of deep space, insulated from the heat generation using magnetic holders, and shielded from the sun. With this proposed cooling system, the HTS coil is cooled to 60K in interplanetary orbits. Because the system does not use refrigerators for its cooling system, the spacecraft can achieve an HTS coil with low power consumption, small mass, and low cost.

Uniaxial Wireless Tissue Palpation Device for Minimally Invasive Surgery

Nowadays surgery tends to be performed with minimally invasive techniques that result in less post-operative pain, recovery time and smaller incisions. However, unlike open surgery, during minimally invasive surgery (MIS) the surgeon has few chances to rely on tactile and kinesthetic feedback [1]. Tissue palpation aids in preventing traumas or in leveraging tactile information to identify tumors, vessels and organic structures buried underneath the tissue surface. Therefore, in the last two decades, research on palpation devices strived to restore tactile and kinesthetic sensations in MIS. This was pursued by performing tissue palpation with different techniques, such as indenting [2], grasping [3] or rolling [1]. Despite this research effort, a translation into clinical practice is still far to come. Even further, surgeons are resistant to the option of devoting a surgical port to a palpation device, because of the available ports are needed for the MIS instruments. As an alternative to this approach, intraoperative ultrasonography devices (IOUS) may be used to detect buried structures [4]. Also this technology, however, requires a dedicated surgical port during the entire procedure.

Separation of &lt;em&gt;Plasmodium falciparum&lt;/em&gt; Late Stage-infected Erythrocytes by Magnetic Means

Unlike other Plasmodium species, P. falciparum can be cultured in the lab, which facilitates its study (1). While the parasitemia achieved can reach the ≈40% limit, the investigator usually keeps the percentage at around 10%. In many cases it is necessary to isolate the parasite-containing red blood cells (RBCs) from the uninfected ones, to enrich the culture and proceed with a given experiment. When P. falciparum infects the erythrocyte, the parasite degrades and feeds from haemoglobin (2, 3). However, the parasite must deal with a very toxic iron-containing haem moiety (4, 5). The parasite eludes its toxicity by transforming the haem into an inert crystal polymer called haemozoin (6, 7). This iron-containing molecule is stored in its food vacuole and the metal in it has an oxidative state which differs from the one in haem (8). The ferric state of iron in the haemozoin confers on it a paramagnetic property absent in uninfected erythrocytes. As the invading parasite reaches maturity, the content of haemozoin also increases (9), which bestows even more paramagnetism on the latest stages of P. falciparum inside the erythrocyte. Based on this paramagnetic property, the latest stages of P. falciparum infected-red blood cells can be separated by passing the culture through a column containing magnetic beads. These beads become magnetic when the columns containing them are placed on a magnet holder. Infected RBCs, due to their paramagnetism, will then be trapped inside the column, while the flow-through will contain, for the most part, uninfected erythrocytes and those containing early stages of the parasite. Here, we describe the methodology to enrich the population of late stage parasites with magnetic columns, which maintains good parasite viability (10). After performing this procedure, the unattached culture can be returned to an incubator to allow the remaining parasites to continue growing.

Magnet configurations for improved separations of magnetic and non-magnetic materials

Magnet configuration. The configuration includes a magnet holder and at least one elongate magnet extending from the magnet holder so that less than one half of the magnet length extends from the holder, whereby a magnetic fluid adjacent the elongate magnet is attracted toward a top edge of the elongate magnet for subsequent removal.

Imaging magnetic responses of nanomagnets by XPEEM

The Spin-resolved Photoelectron Emission Microscope (SPEEM) is a permanently installed set-up at Helmholtz-Zentrum Berlin (HZB). Due to its specific contrast it is mainly used for magnetic imaging and micro-spectroscopy with quantitative analysis. A crucial point in magnetic imaging is the application of magnetic fields. Many experiments require observation of magnetic responses or the preparation of a certain magnetic state during the measurement. We present a dedicated magnetic sample holder combining magnetic field during imaging with additional temperature control. This set-up enables SPEEM to measure magnetization curves of individual Fe nanocubes (18nm)3 in size. If additionally alternating magnetic fields are applied we can image the local magnetic AC susceptibility (χAC) as a function of temperature. The latter is ideally suited to visualize local variations of the Curie temperature (TC) in nano- and microstructures.

Magnetic pulser and sample holder for time- and spin-resolved photoemission spectroscopy on magnetic materials

A compact coil setup, in conjunction with a high power current pulser, is presented; developed especially for time- and spin-resolved photoemission spectroscopy measuring the sample in magnetic remanence at room temperature. A novel approach is presented where the sample is switched in the stray field of a coil pair. This enables the electrical biasing of the sample without altering the electron trajectories due to field gradients introduced by the coils. The pulser driving the coils reaches a peak power of 1 MW at 1 kA with a switching frequency up to 10 kHz suitable for experiments, for example, with state of the art repetition rates of femtosecond laser systems.

Specific Soluble Oligomers of Amyloid-β Peptide Undergo Replication and Form Non-fibrillar Aggregates in Interfacial Environments

Aggregates of amyloid-β (Aβ) peptides have been implicated in the etiology of Alzheimer disease. Among the different forms of Aβ aggregates, low molecular weight species ranging between ~2- and 50-mers, also called "soluble oligomers," have emerged as the species responsible for early synaptic dysfunction and neuronal loss. Emerging evidence suggests that the neurotoxic oligomers need not be formed along the obligatory nucleation-dependant fibril formation pathway. In our earlier work, we reported the isolation of one such "off-pathway" 12-18-mer species of Aβ42 generated from fatty acids called large fatty acid-derived oligomers (LFAOs) (Kumar, A., Bullard, R. L., Patel, P., Paslay, L. C., Singh, D., Bienkiewicz, E. A., Morgan, S. E., and Rangachari, V. (2011) PLoS One 6, e18759). Here, we report the physiochemical aspects of LFAO-monomer interactions as well as LFAO-LFAO associations in the presence of interfaces. We discovered that LFAOs are a replicating strain of oligomers that recruit Aβ42 monomers and quantitatively convert them into LFAO assemblies at the expense of fibrils, a mechanism similar to prion propagation. We also found that in the presence of hexane-buffer or chloroform-buffer interfaces LFAOs are able to associate with themselves to form larger but non-fibrillar aggregates. These results further support the hypothesis that low molecular weight oligomers can be generated via non-fibril formation pathways. Furthermore, the unique replicating property of off-pathway oligomers may hold profound significance for Alzheimer disease pathology.

Use of modern domestically produced equipment in glassmaking practice

Positive experience in using modern Russian equipment — series LMO magnetic separators for quartz sand and a specialized magnetic holder for glass-molds for the production of glass containers — at the “Smerdomskii steklozavod,” is described. It is shown that the use of magnetic enrichment of quartz sand from a local deposit has a positive effect on the technological processes of glassmaking, and the use of specialized magnetic holder for glass-molds increases the repair quality and decreases repair time for glass-molds. At Russian enterprises any improvements achieved by altering the production process are usually made by purchasing and mastering high-capacity imported equipment. However, modern domestically produced equipment also makes it possible not only to save money but also to obtain results equivalent in terms of effectiveness and in some cases not attainable with the use of imported equipment. We shall examine two examples from practice at the “Smerdomskii steklozavod” JSC. Example 1. Stabilization of the iron oxide content in glass batch at the “Smerdomskii steklozavod” JSC by means of magnetic enrichment of quartz sand. The negative effect of an elevated content of iron oxide and the fluctuations of the iron oxide content in glass batch on the overall yield and quality of the yearly production is well known. It is evident that sand from local deposits makes it possible to lower the final production costs of colored container glass. As a rule, to obtain high-quality products it is necessary to lower and stabilize the content of iron oxide in the main component of the glass batch — quartz sand from a local deposit. An accessible method of lowering and stabilizing iron oxide in glass sand is magnetic enrichment. Quart sand from the Sazonovskii deposit (Chagodoshchenskii rayon of Vologodskaya Oblast’) is used at the “Smerdomskii steklozavod” JSC for glass production. To improve the quality of the articles produced at the “Smerdomskii steklozavod” JSC it was necessary to lower and stabilize the content of iron oxide in the quartz sand used at the level 0.4 – 0.55% (with initial fluctuation 0.8 – 1.2%) by means of magnetic separation of hot sand (t 100 – 150°C) after it is dried. The operation of the magnetic separator must be stable in the presence of high dust contamination of the section where glass batch is prepared and the separator must provide stable results for magnetic enrichment with the expected high yield of tailings from magnetic separation (to 15%).

Small Batch Laser Welding Using Light Fasteners and Laser Tack Welding

Laser welding is known for its low heat input compared to arc welding methods. This could enable laser welding of sheet metals with lighter fastening solutions and less time-consuming tack welding alternatives. A feasibility study was carried out to study four different corner joint types for 2 mm thick cold rolledcold-rolled steel sheet by using filler-free laser welding. The aim of the research was to get more experimental knowledge about the laser welding of corner joints. Also possible benefits concerning faster manufacturing times and smaller costs by developing fastening applications for small batch laser welding was to be studied in practice. The 170 mm long joints were welded without air gap or pressing. All corner joint types proved to be weldable with a continuous wave Yb:YAG diode-pumped disk laser. It was also found during the With the experiment it was also found out that laser welding enables the use of light and inexpensive fasteners such as magnetic holders in steadinstead of traditional clamps and fixturing. With some joint types, the insufficient fastening power of magnetic fasteners against distortions was compensated by making a spot-like laser tack weld toat the end of the weld before welding the actual seam. This showed that it is possible to make precise and small tack welds with a laser and to use laser -tacking in sheet metal assembly.

A new gravity‐driven microfluidic‐based electrochemical assay coupled to magnetic beads for nucleic acid detection

In this work, the characterisation and the optimisation of hybridisation assays based on a novel, rapid and sensitive micro-analytical, gravity-driven, flow device is reported. This device combines a special chip containing eight polymer microchannels, with a portable, computer-controlled instrument. The device is used as a platform for affinity experiments using oligonucleotide-modified paramagnetic particles. In our approach, both hybridisation and labelling events are performed on streptavidin-coated paramagnetic microparticles functionalized with a biotinylated capture probe. Modified particles, introduced in the microchannel inlet of the chip, accumulate near the electrode surface by virtue of a magnetic holder. After hybridisation with the complementary sequence, the hybrid is labelled with an alkaline phosphatase conjugate. The electrochemical substrate for alkaline phosphatase revelation is p-aminophenyl phosphate. Solutions and reagents are sequentially passed through the microchannels, until enzyme substrate is added for in situ signal detection. Upon readout, the magnet array is flipped away, beads are removed by addition of regeneration buffer, and the so-regenerated chip is ready for further analysis. This protocol has been applied to the analytical detection of specific DNA sequences of Legionella pneumophila, with an RSD=8.5% and a detection limit of 0.33 nM.

Flow-through immunomagnetic separation system for waterborne pathogen isolation and detection: Application to Giardia and Cryptosporidium cell isolation

Simultaneous sample washing and concentration of two waterborne pathogen samples were demonstrated using a rotational magnetic system under continuous flow conditions. The rotation of periodically arranged small permanent magnets close to a fluidic channel carrying magnetic particle suspension allows the trapping and release of particles along the fluidic channel in a periodic manner. Each trapping and release event resembles one washing cycle. The performance of the magnetic separation system (MSS) was evaluated in order to test its functionality to isolate magnetic-labelled protozoan cells from filtered, concentrated tap water, secondary effluent water, and purified water. Experimental protocols described in US Environmental Protection Agency method 1623 which rely on the use of a magnetic particle concentrator, were applied to test and compare our continuous flow cell separation system to the standard magnetic bead-based isolation instruments. The recovery efficiencies for Giardia cysts using the magnetic tube holder and our magnetic separation system were 90.5% and 90.1%, respectively, from a tap water matrix and about 31% and 18.5%, respectively, from a spiked secondary effluent matrix. The recovery efficiencies for Cryptosporidium cells using the magnetic tube holder and our magnetic separation system were 90% and 83.3%, respectively, from a tap water matrix and about 38% and 36%, respectively, from a spiked secondary effluent matrix. Recoveries from all matrices with the continuous flow system were typically higher in glass tubing conduits than in molded plastic conduits.

Magnetic Assisted Abrasion, a New Method for Nano Level Surface Finishing

A great deal of attention in manufacturing engineering has been focused on finishing operations of hard and brittle materials in recent years. This paper reports an experimental work on the analysis of surface roughness and material removal using design of experiment (DOE) method in magnetic abrasive finishing, (MAF) of flat surfaces. Change in surface roughness and material removal were found to increase with an increase in weight percentage of abrasive particles in magnetic abrasive brush, lubricant volume and decrease in working gap. Also, any decrease in the relative size of the abrasive particles vis-à-vis the iron particles would result into an increase of the surface roughness and decrease in material removal. It was observed that the work piece hardness had no considerable effect on the process results. The optimum parameter levels which lead into the best surface finish and highest material removal were also derived from these experimentations. Optimum levels included weight percentage of abrasive particles of 40%, Lubricant volume of 1 ml, working gap of 3 mm, relative size of abrasive particles vis-à-vis the iron particles of 0.22, and work piece hardness of 82-87 HBN. Disk type test pieces were selected from Al 7075 and their two side surfaces were under experiments. Experiments were made using a milling machine spindle as magnetic pole holder, and its table as fixture holder for work pieces.

Computer simulations for rf design of a Spallation Neutron Source external antenna H− ion source

Electromagnetic modeling of the multicusp external antenna H(-) ion source for the Spallation Neutron Source (SNS) has been performed in order to optimize high-power performance. During development of the SNS external antenna ion source, antenna failures due to high voltage and multicusp magnet holder rf heating concerns under stressful operating conditions led to rf characteristics analysis. In rf simulations, the plasma was modeled as an equivalent lossy metal by defining conductivity as sigma. Insulation designs along with material selections such as ferrite and Teflon could be included in the computer simulations to compare antenna gap potentials, surface power dissipations, and input impedance at the operating frequencies, 2 and 13.56 MHz. Further modeling and design improvements are outlined in the conclusion.

JCEJ Outstanding Paper Award of 2009

Outstanding Paper Awards Subcommittee of Journal of Chemical Engineering of Japan has assessed the 168 papers published in volume 42 into 2009, and the editorial board finally selected the three papers for JCEJ Paper Awards of 2009; those are the papers on “Promotional Effect of Titanium on the Catalytic Performance of Anodic Alumina Supported Silver Catalyst for the Selective Reduction of NO with Propene,” “Preparation of L929 Cell Array by Magnetic Pin Holder Device for Single Cell Function Analysis,” and “Modeling for PEFC MEAs Based on Reaction Rate on Pt Surface and Microstructures of Catalyst Layers.”

Preparation of L929 Cell Array by Magnetic Pin Holder Device for Single Cell Function Analysis

A cell array has been developed for single cell analysis with magnetic cell labeling method using the unmodified colloidal magnetic nanoparticles (magnetite particle with 10 nm diameter). When the magnetic nanoparticles were dispersed in the medium for cell labeling, these particles aggregate to micrometer order sizes. However, when these particles were dispersed in a sucrose solution, above 80% of these particles maintained their size below 100 nm and their dispersibility was kept for at least two weeks. When mouse pulmonic fibroblasts L929 were exposed to the magnetic nanoparticle suspension of a 0.3 M isotonic sucrose solution for 10 min, it was found that the magnetic nanoparticles were taken into the cells at approximately 1.1 pg-Fe/Cell This method was demonstrated without modifying the magnetic nanoparticles, and a variety of cells could be labeled magnetically. It was found that this magnetic labeling method did not influence the cell response to cytokine, TNF-α. The magnetic induction by means of a pin holder device, which is made from magnetic soft iron and contains more than 6000 pillars on its surface, enabled the arrangement of the magnetically labeled cells in arrays. In addition, the method was used to monitor the time course of the responses of L929 cells to TNF-α in a single cell array. The change in the stages of apoptosis such as phosphatidylserine externalization and propidium iodide uptake was detected using fluorescent microscopy.

AIP1 Is Critical in Transducing IRE1-mediated Endoplasmic Reticulum Stress Response

We have previously shown that ASK1-interacting protein 1 (AIP1) transduces tumor necrosis factor-induced ASK1-JNK signaling. Because endoplasmic reticulum (ER) stress activates ASK1-JNK signaling cascade, we investigated the role of AIP1 in ER stress-induced signaling. We created AIP1-deficient mice (AIP1-KO) from which mouse embryonic fibroblasts and vascular endothelial cells were isolated. AIP1-KO cells show dramatic reductions in ER stress-induced, but not oxidative stress-induced, ASK1-JNK activation and cell apoptosis. The ER stress-induced IRE1-JNK/XBP-1 axis, but not the PERK-CHOP1 axis, is blunted in AIP1-KO cells. ER stress induced formation of an AIP1-IRE1 complex, and the PH domain of AIP1 is critical for the IRE1 interaction. Furthermore, reconstitution of AIP1-KO cells with AIP1 wild type, not an AIP1 mutant with a deletion of the PH domain (AIP1-DeltaPH), restores ER stress-induced IRE1-JNK/XBP-1 signaling. AIP1-IRE1 association facilitates IRE1 dimerization, a critical step for activation of IRE1 signaling. More importantly, AIP1-KO mice show impaired ER stress-induced IRE1-dependent signaling in vivo. We conclude that AIP1 is essential for transducing the IRE1-mediated ER stress response.