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Sample records for magnetic bead microarray

  1. On-chip magnetic bead microarray using hydrodynamic focusing in a passive magnetic separator.

    PubMed

    Smistrup, K; Kjeldsen, B G; Reimers, J L; Dufva, M; Petersen, J; Hansen, M F

    2005-11-01

    Implementing DNA and protein microarrays into lab-on-a-chip systems can be problematic since these are sensitive to heat and strong chemicals. Here, we describe the functionalization of a microchannel with two types of magnetic beads using hydrodynamic focusing combined with a passive magnetic separator with arrays of soft magnetic elements. The soft magnetic elements placed on both sides of the channel are magnetized by a relatively weak applied external magnetic field (21 mT) and provide magnetic field gradients attracting magnetic beads. Flows with two differently functionalized magnetic beads and a separating barrier flow are introduced simultaneously at the two channel sides and the centre of the microfluidic channel, respectively. On-chip experiments with fluorescence labeled beads demonstrate that the two types of beads are captured at each of the channel sidewalls. On-chip hybridization experiments show that the microfluidic systems can be functionalized with two sets of beads carrying different probes that selectively recognize a single base pair mismatch in target DNA. By switching the places of the two types of beads it is shown that the microsystem can be cleaned and functionalized repeatedly with different beads with no cross-talk between experiments. PMID:16234958

  2. An automated microfluidic system for single-stranded DNA preparation and magnetic bead-based microarray analysis.

    PubMed

    Wang, Shuaiqin; Sun, Yujia; Gan, Wupeng; Liu, Yan; Xiang, Guangxin; Wang, Dong; Wang, Lei; Cheng, Jing; Liu, Peng

    2015-03-01

    We present an integrated microfluidic device capable of performing single-stranded DNA (ssDNA) preparation and magnetic bead-based microarray analysis with a white-light detection for detecting mutations that account for hereditary hearing loss. The entire operation process, which includes loading of streptavidin-coated magnetic beads (MBs) and biotin-labeled polymerase chain reaction products, active dispersion of the MBs with DNA for binding, alkaline denaturation of DNA, dynamic hybridization of the bead-labeled ssDNA to a tag array, and white-light detection, can all be automatically accomplished in a single chamber of the microchip, which was operated on a self-contained instrument with all the necessary components for thermal control, fluidic control, and detection. Two novel mixing valves with embedded polydimethylsiloxane membranes, which can alternately generate a 3-μl pulse flow at a peak rate of around 160 mm/s, were integrated into the chip for thoroughly dispersing magnetic beads in 2 min. The binding efficiency of biotinylated oligonucleotides to beads was measured to be 80.6% of that obtained in a tube with the conventional method. To critically test the performance of this automated microsystem, we employed a commercial microarray-based detection kit for detecting nine mutation loci that account for hereditary hearing loss. The limit of detection of the microsystem was determined as 2.5 ng of input K562 standard genomic DNA using this kit. In addition, four blood samples obtained from persons with mutations were all correctly typed by our system in less than 45 min per run. The fully automated, "amplicon-in-answer-out" operation, together with the white-light detection, makes our system an excellent platform for low-cost, rapid genotyping in clinical diagnosis. PMID:25825617

  3. An automated microfluidic system for single-stranded DNA preparation and magnetic bead-based microarray analysis

    PubMed Central

    Wang, Shuaiqin; Sun, Yujia; Liu, Yan; Xiang, Guangxin; Wang, Lei; Cheng, Jing; Liu, Peng

    2015-01-01

    We present an integrated microfluidic device capable of performing single-stranded DNA (ssDNA) preparation and magnetic bead-based microarray analysis with a white-light detection for detecting mutations that account for hereditary hearing loss. The entire operation process, which includes loading of streptavidin-coated magnetic beads (MBs) and biotin-labeled polymerase chain reaction products, active dispersion of the MBs with DNA for binding, alkaline denaturation of DNA, dynamic hybridization of the bead-labeled ssDNA to a tag array, and white-light detection, can all be automatically accomplished in a single chamber of the microchip, which was operated on a self-contained instrument with all the necessary components for thermal control, fluidic control, and detection. Two novel mixing valves with embedded polydimethylsiloxane membranes, which can alternately generate a 3-μl pulse flow at a peak rate of around 160 mm/s, were integrated into the chip for thoroughly dispersing magnetic beads in 2 min. The binding efficiency of biotinylated oligonucleotides to beads was measured to be 80.6% of that obtained in a tube with the conventional method. To critically test the performance of this automated microsystem, we employed a commercial microarray-based detection kit for detecting nine mutation loci that account for hereditary hearing loss. The limit of detection of the microsystem was determined as 2.5 ng of input K562 standard genomic DNA using this kit. In addition, four blood samples obtained from persons with mutations were all correctly typed by our system in less than 45 min per run. The fully automated, “amplicon-in-answer-out” operation, together with the white-light detection, makes our system an excellent platform for low-cost, rapid genotyping in clinical diagnosis. PMID:25825617

  4. Single nucleotide polymorphism genotyping using BeadChip microarrays.

    PubMed

    Lambert, Gilliam; Tsinajinnie, Darwin; Duggan, David

    2013-07-01

    The genotyping of single nucleotide polymorphisms (SNPs) has successfully contributed to the study of complex diseases more than any other technology to date. Genome-wide association studies (GWAS) using 10,000s to >1,000,000 SNPs have identified 1000s of statistically significant SNPs pertaining to 17 different human disease and trait categories. Post-GWAS fine-mapping studies using 10,000s to 100,000s SNPs on a microarray have narrowed the region of interest for many of these GWAS findings; in addition, independent signals within the original GWAS region have been identified. Focused content, SNP-based microarrays such as the human exome, for example, have too been used successfully to identify novel disease associations. Success has come to studies where 100s to 10,000s (mostly) to >100,000 samples were genotyped. For the time being, SNP-based microarrays remain cost-effective especially when studying large numbers of samples compared to other "genotyping" technologies including next generation sequencing. In this unit, protocols for manual (LIMS-free), semi-manual, and automated processing of BeadChip microarrays are presented. Lower throughput studies will find value in the manual and semi-manual protocols, while all types of studies--low-, medium-, and high-throughput--will find value in the semi-manual and automated protocols. PMID:23853082

  5. Magnetic bead detection using nano-transformers.

    PubMed

    Kim, Hyung Kwon; Hwang, Jong Seung; Hwang, Sung Woo; Ahn, Doyeol

    2010-11-19

    A novel scheme to detect magnetic beads using a nano-scale transformer with a femtoweber resolution is reported. We have performed a Faraday's induction experiment with the nano-transformer at room temperature. The transformer shows the linear output voltage responses to the sinusoidal input current. When magnetic beads are placed on the transformer, the output responses are increased by an amount corresponding to the added magnetic flux from the beads when compared with the case of no beads on the transformer. In this way, we could determine whether magnetic beads are on top of the transformer in a single particle level. PMID:20972313

  6. A dynamic bead-based microarray for parallel DNA detection

    NASA Astrophysics Data System (ADS)

    Sochol, R. D.; Casavant, B. P.; Dueck, M. E.; Lee, L. P.; Lin, L.

    2011-05-01

    A microfluidic system has been designed and constructed by means of micromachining processes to integrate both microfluidic mixing of mobile microbeads and hydrodynamic microbead arraying capabilities on a single chip to simultaneously detect multiple bio-molecules. The prototype system has four parallel reaction chambers, which include microchannels of 18 × 50 µm2 cross-sectional area and a microfluidic mixing section of 22 cm length. Parallel detection of multiple DNA oligonucleotide sequences was achieved via molecular beacon probes immobilized on polystyrene microbeads of 16 µm diameter. Experimental results show quantitative detection of three distinct DNA oligonucleotide sequences from the Hepatitis C viral (HCV) genome with single base-pair mismatch specificity. Our dynamic bead-based microarray offers an effective microfluidic platform to increase parallelization of reactions and improve microbead handling for various biological applications, including bio-molecule detection, medical diagnostics and drug screening.

  7. Comparison of non-magnetic and magnetic beads in bead-based assays.

    PubMed

    Hansenová Maňásková, Silvie; van Belkum, Alex; Endtz, Hubert P; Bikker, Floris J; Veerman, Enno C I; van Wamel, Willem J B

    2016-09-01

    Multiplex bead-based flow cytometry is an attractive way for simultaneous, rapid and cost-effective analysis of multiple analytes in a single sample. Previously, we developed various bead-based assays using non-magnetic beads coated with Staphylococcus aureus and Streptococcus pneumoniae antigens for the detection of antibodies. Here, we compared the performance of the assay using non-magnetic beads with one based on the newly developed magnetic beads. We optimized the magnetic beads' coupling procedure and antibody detection assays for S. aureus and S. pneumoniae antigens and we measured IgG in human pooled serum against a series of S. aureus and S. pneumoniae-derived antigens in a singleplex and in a multiplex assay, respectively. For the multiplex assay, the comparison between magnetic and non-magnetic beads showed: i) in the majority of the cases (13 of the 17 tested S. pneumoniae antigens) significantly higher Median Fluorescence Intensity (MFI) values, ii) lower detection limits, iii) lower coefficient of variation (CV: 12% vs. 7% for non-magnetic vs. magnetic beads), so lower inter-assay variation and hence higher reproducibility. Magnetic bead coupling is cost effective, as we used 25% of the normal amount of antigen and only 50% of the beads in comparison to the non-magnetic beads. This optimized magnetic-based assay, which combines ease of use with an improved assay performance, allows detection of antibodies with a low titer that are potentially missed with the non-magnetic-based assay. PMID:27296810

  8. A large-area hemispherical perforated bead microarray for monitoring bead based aptamer and target protein interaction

    PubMed Central

    Choi, Jong Seob; Bae, Sunwoong; Kim, Kyung Hoon; Seo, Tae Seok

    2014-01-01

    Herein, we present a large-area 3D hemispherical perforated microwell structure for a bead based bioassay. Such a unique microstructure enables us to perform the rapid and stable localization of the beads at the single bead level and the facile manipulation of the bead capture and retrieval with high speed and efficiency. The fabrication process mainly consisted of three steps: the convex micropatterned nickel (Ni) mold production from the concave micropatterned silicon (Si) wafer, hot embossing on the polymer matrix to generate the concave micropattened acrylate sheet, and reactive ion etching to make the bottom holes. The large-area hemispherical perforated micropatterned acrylate sheet was sandwiched between two polydimethylsiloxane (PDMS) microchannel layers. The bead solution was injected and recovered in the top PDMS microchannel, while the bottom PDMS microchannel was connected with control lines to exert the hydrodynamic force in order to alter the flow direction of the bead solution for the bead capture and release operation. The streptavidin-coated microbead capture was achieved with almost 100% yield within 1 min, and all the beads were retrieved in 10 s. Lysozyme or thrombin binding aptamer labelled microbeads were trapped on the proposed bead microarray, and the in situ fluorescence signal of the bead array was monitored after aptamer-target protein interaction. The protein-aptamer conjugated microbeads were recovered, and the aptamer was isolated for matrix assisted laser desorption/ionization time-of-flight mass spectrometry analysis to confirm the identity of the aptamer. PMID:25587373

  9. Bead-based microarray immunoassay for lung cancer biomarkers using quantum dots as labels.

    PubMed

    Liu, Lifen; Wu, Simin; Jing, Fengxiang; Zhou, Hongbo; Jia, Chunping; Li, Gang; Cong, Hui; Jin, Qinghui; Zhao, Jianlong

    2016-06-15

    In this study, we developed a multiplex immunoassay system that combines the suspension and planar microarray formats within a single layer of polydimethylsiloxane (PDMS) using soft lithography technology. The suspension format was based on the target proteins forming a sandwich structure between the magnetic beads and the quantum dot (QD) probes through specific antibody-antigen interactions. The planar microarray format was produced by fabricating an array of micro-wells in PDMS. Each micro-well was designed to trap a single microbead and eventually generated a microbead array within the PDMS chamber. The resultant bead-based on-chip assay could be used for simultaneously detecting three lung cancer biomarkers-carcinoembryonic antigen (CEA), fragments of cytokeratin 19 (CYFRA21-1) and neuron-specific enolase (NSE)-in 10 μl of human serum, with a wide linear dynamic range (1.03-111 ng/mL for CEA and CYFRA21-1; 9.26-1000 ng/ml for NSE) and a low detection limit (CEA: 0.19 ng/ml; CYFRA21-1: 0.97 ng/ml; NSE: 0.37 ng/ml; S/N=3). Our micro-well chip does not require complex e-beam lithography or the reactive ion etching process as with existing micro-well systems, which rely on expensive focused ion beam (FIB) milling or optical fiber bundles. Furthermore, the current approach is easy to operate without extra driving equipment such as pumps, and can make parallel detection for multiplexing with rapid binding kinetics, small reagent consumption and low cost. This work has demonstrated the importance of the successful application of on-chip multiplexing sandwich assays for the detection of biomarker proteins. PMID:26852198

  10. Microfluidic Magnetic Bead Assay for Cell Detection.

    PubMed

    Liu, Fan; KC, Pawan; Zhang, Ge; Zhe, Jiang

    2016-01-01

    We present a novel cell detection device based on a magnetic bead cell assay and microfluidic Coulter counting technology. The device cannot only accurately measure cells size distribution and concentration but also detect specific target cells. The device consists of two identical micro Coulter counters separated by a fluid chamber where an external magnetic field is applied. Antibody-functionalized magnetic beads were bound to specific antigens expressed on the target cells. A high-gradient magnetic field was applied to the chamber closer to the second counter via an external cylindrical magnet. Because of the magnetic interaction between the magnetic beads and the magnetic field, target cells were retarded by the magnetic field; transit time of a target cell (bound with magnetic beads) passing through the second counter was longer than that through the first counter. In comparison, transit times of a nontarget cell remained nearly the same when it passed through both counters. Thus, from the transit time delay we can identify target cells and quantify their concentration in a cell suspension. The transit time and the size of each cell were accurately measured in terms of the width and amplitude of the resistive pulses generated from the two Coulter counters. Experiments demonstrated that for mixed cells with various target cell ratios, the transit time delay increased approximately linearly with the increasing target cell ratio. The limit of detection (LOD) of the assay was estimated to be 5.6% in terms of target cell ratio. Cell viability tests further demonstrated that most cells were viable after the detection. With the simple device configuration and easy sample preparation, this rapid and reliable method is expected to accurately detect target cells and could be applied to facilitate stem cell isolation and characterization. PMID:26636715

  11. A Fully Automatic Method for Gridding Bright Field Images of Bead-Based Microarrays.

    PubMed

    Datta, Abhik; Wai-Kin Kong, Adams; Yow, Kin-Choong

    2016-07-01

    In this paper, a fully automatic method for gridding bright field images of bead-based microarrays is proposed. There have been numerous techniques developed for gridding fluorescence images of traditional spotted microarrays but to our best knowledge, no algorithm has yet been developed for gridding bright field images of bead-based microarrays. The proposed gridding method is designed for automatic quality control during fabrication and assembly of bead-based microarrays. The method begins by estimating the grid parameters using an evolutionary algorithm. This is followed by a grid-fitting step that rigidly aligns an ideal grid with the image. Finally, a grid refinement step deforms the ideal grid to better fit the image. The grid fitting and refinement are performed locally and the final grid is a nonlinear (piecewise affine) grid. To deal with extreme corruptions in the image, the initial grid parameter estimation and grid-fitting steps employ robust search techniques. The proposed method does not have any free parameters that need tuning. The method is capable of identifying the grid structure even in the presence of extreme amounts of artifacts and distortions. Evaluation results on a variety of images are presented. PMID:26011899

  12. Scanning probe measurements on a magnetic bead biosensor

    NASA Astrophysics Data System (ADS)

    Megens, Mischa; de Theije, Femke; de Boer, Bart; van Gaal, Frans

    2007-07-01

    We experimentally demonstrate the sensitivity of an integrated detection scheme for small superparamagnetic beads, intended for medical diagnostic applications. Detection is based on the giant magnetoresistance effect of a 100×3μm2 magnetic multilayer strip. A conductive wire to magnetize the superparamagnetic beads is integrated on the same substrate. By scanning a single bead over the wires and sensor strip using an atomic force microscope, we simultaneously measure topography and sensor resistivity in a three-dimensional volume above the sensor. The observations can be explained well by means of the macroscopically measured sensor resistivity curve and the magnetization of the beads, combined with the Biot-Savart law for the magnetic field of the wire. From these encouraging results, we project that it is possible to detect even a single 300nm superparamagnetic bead on our sensor.

  13. Guided self-assembly of magnetic beads for biomedical applications

    NASA Astrophysics Data System (ADS)

    Gusenbauer, Markus; Nguyen, Ha; Reichel, Franz; Exl, Lukas; Bance, Simon; Fischbacher, Johann; Özelt, Harald; Kovacs, Alexander; Brandl, Martin; Schrefl, Thomas

    2014-02-01

    Micromagnetic beads are widely used in biomedical applications for cell separation, drug delivery, and hyperthermia cancer treatment. Here we propose to use self-organized magnetic bead structures which accumulate on fixed magnetic seeding points to isolate circulating tumor cells. The analysis of circulating tumor cells is an emerging tool for cancer biology research and clinical cancer management including the detection, diagnosis and monitoring of cancer. Microfluidic chips for isolating circulating tumor cells use either affinity, size or density capturing methods. We combine multiphysics simulation techniques to understand the microscopic behavior of magnetic beads interacting with soft magnetic accumulation points used in lab-on-chip technologies. Our proposed chip technology offers the possibility to combine affinity and size capturing with special antibody-coated bead arrangements using a magnetic gradient field created by Neodymium Iron Boron permanent magnets. The multiscale simulation environment combines magnetic field computation, fluid dynamics and discrete particle dynamics.

  14. Multiplexed Analysis of Serum Breast and Ovarian Cancer Markers by Means of Suspension Bead-quantum Dot Microarrays

    NASA Astrophysics Data System (ADS)

    Brazhnik, Kristina; Sokolova, Zinaida; Baryshnikova, Maria; Bilan, Regina; Nabiev, Igor; Sukhanova, Alyona

    Multiplexed analysis of cancer markers is crucial for early tumor diagnosis and screening. We have designed lab-on-a-bead microarray for quantitative detection of three breast cancer markers in human serum. Quantum dots were used as bead-bound fluorescent tags for identifying each marker by means of flow cytometry. Antigen-specific beads reliably detected CA 15-3, CEA, and CA 125 in serum samples, providing clear discrimination between the samples with respect to the antigen levels. The novel microarray is advantageous over the routine single-analyte ones due to the simultaneous detection of various markers. Therefore the developed microarray is a promising tool for serum tumor marker profiling.

  15. On-bead antibody-small molecule conjugation using high-capacity magnetic beads.

    PubMed

    Nath, Nidhi; Godat, Becky; Benink, Hélène; Urh, Marjeta

    2015-11-01

    Antibodies labeled with small molecules such as fluorophore, biotin or drugs play an important role in various areas of biological research, drug discovery and diagnostics. However, the majority of current methods for labeling antibodies is solution-based and has several limitations including the need for purified antibodies at high concentrations and multiple buffer exchange steps. In this study, a method (on-bead conjugation) is described that addresses these limitations by combining antibody purification and conjugation in a single workflow. This method uses high capacity-magnetic Protein A or Protein G beads to capture antibodies directly from cell media followed by conjugation with small molecules and elution of conjugated antibodies from the beads. High-capacity magnetic antibody capture beads are key to this method and were developed by combining porous and hydrophilic cellulose beads with oriented immobilization of Protein A and Protein G using HaloTag technology. With a variety of fluorophores it is shown that the on-bead conjugation method is compatible with both thiol- and amine-based chemistry. This method enables simple and rapid processing of multiple samples in parallel with high-efficiency antibody recovery. It is further shown that recovered antibodies are functional and compatible with downstream applications. PMID:26316179

  16. Planar Hall effect bridge geometries optimized for magnetic bead detection

    NASA Astrophysics Data System (ADS)

    Østerberg, Frederik Westergaard; Rizzi, Giovanni; Henriksen, Anders Dahl; Hansen, Mikkel Fougt

    2014-05-01

    Novel designs of planar Hall effect bridge sensors optimized for magnetic bead detection are presented and characterized. By constructing the sensor geometries appropriately, the sensors can be tailored to be sensitive to an external magnetic field, the magnetic field due to beads being magnetized by the sensor self-field or a combination thereof. The sensors can be made nominally insensitive to small external magnetic fields, while being maximally sensitive to magnetic beads, magnetized by the sensor self-field. Thus, the sensor designs can be tailored towards specific applications with minimal influence of external variables. Three different sensor designs are analyzed theoretically. To experimentally validate the theoretical signals, two sets of measurements are performed. First, the sensor signals are characterized as function of an externally applied magnetic field. Then, measurements of the dynamic magnetic response of suspensions of magnetic beads with a nominal diameter of 80 nm are performed. Furthermore, a method to amplify the signal by appropriate combinations of multiple sensor segments is demonstrated.

  17. Phase Diagram Characterization Using Magnetic Beads as Liquid Carriers.

    PubMed

    Blumenschein, Nicholas; Han, Daewoo; Steckl, Andrew J

    2015-01-01

    Magnetic beads with ~1.9 µm average diameter were used to transport microliter volumes of liquids between contiguous liquid segments with a tube for the purpose of investigating phase change of those liquid segments. The magnetic beads were externally controlled using a magnet, allowing for the beads to bridge the air valve between the adjacent liquid segments. A hydrophobic coating was applied to the inner surface of the tube to enhance the separation between two liquid segments. The applied magnetic field formed an aggregate cluster of magnetic beads, capturing a certain liquid amount within the cluster that is referred to as carry-over volume. A fluorescent dye was added to one liquid segment, followed by a series of liquid transfers, which then changed the fluorescence intensity in the neighboring liquid segment. Based on the numerical analysis of the measured fluorescence intensity change, the carry-over volume per mass of magnetic beads has been found to be ~2 to 3 µl/mg. This small amount of liquid allowed for the use of comparatively small liquid segments of a couple hundred microliters, enhancing the feasibility of the device for a lab-in-tube approach. This technique of applying small compositional variation in a liquid volume was applied to analyzing the binary phase diagram between water and the surfactant C12E5 (pentaethylene glycol monododecyl ether), leading to quicker analysis with smaller sample volumes than conventional methods. PMID:26381055

  18. An integrated open-cavity system for magnetic bead manipulation.

    PubMed

    Abu-Nimeh, F T; Salem, F M

    2013-02-01

    Superparamagnetic beads are increasingly used in biomedical assays to manipulate, transport, and maneuver biomaterials. We present a low-cost integrated system designed in bulk CMOS to manipulate and separate biomedical magnetic beads. The system consists of 8 × 8 coil-arrays suitable for single bead manipulation, or collaborative multi-bead manipulation, using pseudo-parallel executions. We demonstrate the flexibility of the design in terms of different coil sizes, DC current levels, and layout techniques. In one array module example, the size of a single coil is 30 μm × 30 μm and the full array occupies an area of 248 μm × 248 μm in 0.5 μm CMOS technology. The programmable DC current source supports 8 discrete levels up to 1.5 mA. The total power consumption of the entire module is 9 mW when running at full power. PMID:23853277

  19. Using magnetic beads to reduce reanut allergens from peanut extracts.

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Ferric irons (Fe3+) and phenolic compounds have been shown to bind to peanut allergens. An easy way to isolate peanut allergens is by use of magnetic beads attached with or without phenolics to capture peanut allergens or allergen-Fe3+ complexes, thus, achieving the goal of producing peanut extracts...

  20. Complex susceptibility measurements of a suspension of magnetic beads

    NASA Astrophysics Data System (ADS)

    Fannin, P. C.; Mac Oireachtaigh, C.; Cohen-Tannoudji, L.; Bertrand, E.; Bibette, J.

    2006-05-01

    Measurements of the frequency and field dependence of the complex magnetic susceptibility, χ(ω,H)=χs'(ω,H)-iχs″(ω,H), of a suspension of magnetic beads in water over the frequency range 200 Hz to 1 MHz are presented. The magnetic polarizing field, H, is applied to the sample, first in a forward direction and then in a reverse direction and from a plot of the static susceptibility, χ, against polarizing field H, the existence of a hysteresis effect is demonstrated.

  1. Manipulation of superparamagnetic beads using on-chip current lines placed on a ferrite magnet

    NASA Astrophysics Data System (ADS)

    Wang, Z. H.; Lew, W. S.; Bland, J. A. C.

    2006-04-01

    Manipulation of superparamagnetic beads in a static solution is demonstrated using on-chip current striplines placed on a ferrite magnet. The ferrite magnet fits the requirement to enhance the bead's magnetic moment while still keeping beads randomly dispersed in the liquid, so allowing easy and selective manipulation of single beads. By applying currents up to hundreds of milliampere, the tapered stripline first attracts the beads to its edge, then the magnetic force along the edge drives the trapped beads moving continuously towards the chip center. On arriving into the chip central area (a square zone which acts as a site to collect the arriving beads), fine manipulation of selected single beads is further performed by switching on/off and/or tuning the current passing through the nearby quadruple striplines. We suggest that the present system may provide a simple but effective platform for handling magnetic tags for biological and biomedical applications.

  2. Aptamer-modified magnetic beads in affinity separation of proteins.

    PubMed

    Zhu, Guohong; Walter, Johanna-Gabriela

    2015-01-01

    Aptamers are valuable alternative ligands for affinity separations. Here, we describe the aptamer-based affinity separation of His-tagged proteins using an aptamer directed against the His-tag. The immobilization of the aptamer to magnetic beads is described as well as the aptamer-based purification and proper methods for the characterization of the process. Moreover, indications for the transfer of the process to other aptamers are given. PMID:25749947

  3. Influence of immobilized biomolecules on magnetic bead plug formation and retention in capillary electrophoresis.

    PubMed

    Henken, Rachel L; Chantiwas, Rattikan; Gilman, S Douglass

    2012-03-01

    Significant changes in the formation and retention of magnetic bead plugs in a capillary during electrophoresis were studied, and it was demonstrated that these effects were due to the type of biological molecule immobilized on the surface of these beads. Three biological molecules, an antibody, an oligonucleotide, and alkaline phosphatase (AP), were attached to otherwise identical streptavidin-coated magnetic beads through biotin-avidin binding in order to isolate differences in bead immobilization in a magnetic field resulting from the type of biological molecule immobilized on the bead surface. AP was also attached to the magnetic beads using epoxy groups on the bead surfaces (instead of avidin-biotin binding) to study the impact of immobilization chemistry. The formation and retention of magnetic bead plugs were studied quantitatively using light scattering detection of magnetic particles eluting from the bead plugs and qualitatively using microscopy. Both the types of biomolecule immobilized on the magnetic bead surface and the chemistry used to link the biomolecule to the magnetic bead impacted the formation and retention of the bead plugs. PMID:22437880

  4. Polymerase chain reaction system using magnetic beads for analyzing a sample that includes nucleic acid

    SciTech Connect

    Nasarabadi, Shanavaz

    2011-01-11

    A polymerase chain reaction system for analyzing a sample containing nucleic acid includes providing magnetic beads; providing a flow channel having a polymerase chain reaction chamber, a pre polymerase chain reaction magnet position adjacent the polymerase chain reaction chamber, and a post pre polymerase magnet position adjacent the polymerase chain reaction chamber. The nucleic acid is bound to the magnetic beads. The magnetic beads with the nucleic acid flow to the pre polymerase chain reaction magnet position in the flow channel. The magnetic beads and the nucleic acid are washed with ethanol. The nucleic acid in the polymerase chain reaction chamber is amplified. The magnetic beads and the nucleic acid are separated into a waste stream containing the magnetic beads and a post polymerase chain reaction mix containing the nucleic acid. The reaction mix containing the nucleic acid flows to an analysis unit in the channel for analysis.

  5. Fast epitope mapping for the anti-MUC1 monoclonal antibody by combining a one-bead-one-glycopeptide library and a microarray platform.

    PubMed

    Garcia-Martin, Fayna; Matsushita, Takahiko; Hinou, Hiroshi; Nishimura, Shin-Ichiro

    2014-11-24

    Anti-MUC1 monoclonal antibodies (mAbs) are powerful tools that can be used to recognize cancer-related MUC1 molecules, the O-glycosylation status of which is believed to affect binding affinity. We demonstrate the feasibility of using a rapid screening methodology to elucidate those effects. The approach involves i) "one-bead-one-compound"-based preparation of bilayer resins carrying glycopeptides on the shell and mass-tag tripeptides coding O-glycan patterns in the core, ii) on-resin screening with an anti-MUC1 mAb, iii) separating positive resins by utilizing secondary antibody conjugation with magnetic beads, and (iv) decoding the mass-tag that is detached from the positive resins pool by using mass spectrometric analysis. We tested a small library consisting of 27 MUC1 glycopeptides with different O-glycosylations against anti-MUC1 mAb clone VU-3C6. Qualitative mass-tag analysis showed that increasing the number of glycans leads to an increase in the binding affinity. Six glycopeptides selected from the library were validated by using a microarray-based assay. Our screening provides valuable information on O-glycosylations of epitopes leading to high affinity with mAb. PMID:25303614

  6. Comparison between simulation and experimentally observed interactions between two magnetic beads in a fluidic system

    NASA Astrophysics Data System (ADS)

    Oduwole, Olayinka; Grob, David Tim; Sheard, Steve

    2016-06-01

    Continuous flow separation of magnetic particles within a microfluidic device could lead to improved performance of magnetic bead-based assays but the undesirable formation of bead clusters reduces its efficiency; this efficiency refers to the ability to separate bound magnetic beads from a mixture of particles. Such agglomerates are formed due to magnetic binding forces while hydrodynamic interactions strongly influence the particles' movement. This paper presents a model for interactions between a pair of equal sized super-paramagnetic beads suspended in water within a uniform magnetic field. To the best of our knowledge, we present for the first time a comparison between simulated trajectories and the beads' movement captured on video; the beads were suspended in a stationary fluid placed within a uniform magnetic field. In conclusion, the model is a good approximation for beads interacting with their nearest neighbours and is able to predict the trajectory pattern of these particles in a magnetic bead-based assay. Predicting the magnetically induced interaction of nearby beads will help in determining the density of beads in an assay and in avoiding agglomeration over a fixed time duration.

  7. Comparison of three magnetic bead surface functionalities for RNA extraction and detection.

    PubMed

    Adams, Nicholas M; Bordelon, Hali; Wang, Kwo-Kwang A; Albert, Laura E; Wright, David W; Haselton, Frederick R

    2015-03-25

    Magnetic beads are convenient for extracting nucleic acid biomarkers from biological samples prior to molecular detection. These beads are available with a variety of surface functionalities designed to capture particular subsets of RNA. We hypothesized that bead surface functionality affects binding kinetics, processing simplicity, and compatibility with molecular detection strategies. In this report, three magnetic bead surface chemistries designed to bind nucleic acids, silica, oligo (dT), and a specific oligonucleotide sequence were evaluated. Commercially available silica-coated and oligo (dT) beads, as well as beads functionalized with oligonucleotides complementary to respiratory syncytial virus (RSV) nucleocapsid gene, respectively recovered ∼75, ∼71, and ∼7% target RSV mRNA after a 1 min of incubation time in a surrogate patient sample spiked with the target. RSV-specific beads required much longer incubation times to recover amounts of the target comparable to the other beads (∼77% at 180 min). As expected, silica-coated beads extracted total RNA, oligo (dT) beads selectively extracted total mRNA, and RSV-specific beads selectively extracted RSV N gene mRNA. The choice of bead functionality is generally dependent on the target detection strategy. The silica-coated beads are most suitable for applications that require nucleic acids other than mRNA, especially with detection strategies that are tolerant of a high concentration of nontarget background nucleic acids, such as RT-PCR. On the other hand, oligo (dT) beads are best-suited for mRNA targets, as they bind biomarkers rapidly, have relatively high recovery, and enable detection strategies to be performed directly on the bead surface. Sequence-specific beads may be best for applications that are not tolerant of a high concentration of nontarget nucleic acids that require short RNA sequences without poly(A) tails, such as microRNAs, or that perform RNA detection directly on the bead surface. PMID

  8. Dose-response curve of a microfluidic magnetic bead-based surface coverage sandwich assay.

    PubMed

    Cornaglia, Matteo; Trouillon, Raphaël; Tekin, H Cumhur; Lehnert, Thomas; Gijs, Martin A M

    2015-09-25

    Magnetic micro- and nanoparticles ('magnetic beads') have been used to advantage in many microfluidic devices for sensitive antigen (Ag) detection. Today, assays that use as read-out of the signal the number count of immobilized beads on a surface for quantification of a sample's analyte concentration have been among the most sensitive and have allowed protein detection lower than the fgmL(-1) concentration range. Recently, we have proposed in this category a magnetic bead surface coverage assay (Tekin et al., 2013 [1]), in which 'large' (2.8μm) antibody (Ab)-functionalized magnetic beads captured their Ag from a serum and these Ag-carrying beads were subsequently exposed to a surface pattern of fixed 'small' (1.0μm) Ab-coated magnetic beads. When the system was exposed to a magnetic induction field, the magnet dipole attractive interactions between the two bead types were used as a handle to approach both bead surfaces and assist with Ag-Ab immunocomplex formation, while unspecific binding (in absence of an Ag) of a large bead was reduced by exploiting viscous drag flow. The dose-response curve of this type of assay had two remarkable features: (i) its ability to detect an output signal (i.e. bead number count) for very low Ag concentrations, and (ii) an output signal of the assay that was non-linear with respect to Ag concentration. We explain here the observed dose-response curves and show that the type of interactions and the concept of our assay are in favour of detecting the lowest analyte concentrations (where typically either zero or one Ag is carried per large bead), while higher concentrations are less efficiently detected. We propose a random walk process for the Ag-carrying bead over the magnetic landscape of small beads and this model description explains the enhanced overall capture probability of this assay and its particular non-linear dose response curves. PMID:25817550

  9. Bioconjugation of Antibodies and Enzyme Labels onto Magnetic Beads.

    PubMed

    Otieno, B A; Krause, C E; Rusling, J F

    2016-01-01

    Immunoassays employ antibodies and labels to capture and detect target macromolecular analytes, often from complex sample matrices such as serum, plasma, or saliva. The high affinity and specificity of antibody-antigen interactions makes immunoassays critically important analytical techniques for clinical diagnostics as well as other research applications in the areas of pharmaceutical and environmental analysis. Integration of magnetic beads (MBs) into immunoassays and other bioanalytical methodologies is a valuable approach to allow efficient target capture, enrichment, and convenient separation. In addition, large signal amplification can be achieved by preconcentration of the target and by attaching many thousands of enzyme labels to the MBs. These features have enabled MB-based biosensors to achieve ultra-low detection limits needed for advanced clinical diagnostics that are challenging or impossible using traditional immunoassays. MBs are employed either as mobile substrates for target analyte capture, as detection labels (or label carriers), or simultaneously as substrates and labels. For optimal assay performance, it is crucial to apply an easy, efficient, and robust bead-probe conjugation protocol, and to thoroughly characterize the bioconjugated products. Herein, we describe methods used in our laboratory to functionalize MBs with antibodies and enzyme labels for ultrasensitive detection of protein analytes. We also present detailed strategies for characterizing the MB bioconjugates. PMID:27112398

  10. Magnetic bead detection using domain wall-based nanosensor

    NASA Astrophysics Data System (ADS)

    Corte-León, H.; Krzysteczko, P.; Schumacher, H. W.; Manzin, A.; Cox, D.; Antonov, V.; Kazakova, O.

    2015-05-01

    We investigate the effect of a single magnetic bead (MB) on the domain wall (DW) pinning/depinning fields of a DW trapped at the corner of an L-shaped magnetic nanodevice. DW propagation across the device is investigated using magnetoresistance measurements. DW pinning/depinning fields are characterized in as-prepared devices and after placement of a 1 μm-sized MB (Dynabeads® MyOne™) at the corner. The effect of the MB on the DW dynamics is seen as an increase in the depinning field for specific orientations of the device with respect to the external magnetic field. The shift of the depinning field, ΔBdep = 4.5-27.0 mT, is highly stable and reproducible, being significantly above the stochastic deviation which is about 0.5 mT. The shift in the deppinning field is inversely proportional to the device width and larger for small negative angles between the device and the external magnetic field. Thus, we demonstrate that DW-based devices can be successfully used for detection of single micron size MB.

  11. Magnetic bead detection using domain wall-based nanosensor

    SciTech Connect

    Corte-León, H.; Krzysteczko, P.; Schumacher, H. W.; Manzin, A.; Cox, D.; Antonov, V.; Kazakova, O.

    2015-05-07

    We investigate the effect of a single magnetic bead (MB) on the domain wall (DW) pinning/depinning fields of a DW trapped at the corner of an L-shaped magnetic nanodevice. DW propagation across the device is investigated using magnetoresistance measurements. DW pinning/depinning fields are characterized in as-prepared devices and after placement of a 1 μm-sized MB (Dynabeads{sup ®} MyOne{sup ™}) at the corner. The effect of the MB on the DW dynamics is seen as an increase in the depinning field for specific orientations of the device with respect to the external magnetic field. The shift of the depinning field, ΔB{sub dep} = 4.5–27.0 mT, is highly stable and reproducible, being significantly above the stochastic deviation which is about 0.5 mT. The shift in the deppinning field is inversely proportional to the device width and larger for small negative angles between the device and the external magnetic field. Thus, we demonstrate that DW-based devices can be successfully used for detection of single micron size MB.

  12. Parallel RNA extraction using magnetic beads and a droplet array

    PubMed Central

    Shi, Xu; Chen, Chun-Hong; Gao, Weimin; Meldrum, Deirdre R.

    2015-01-01

    Nucleic acid extraction is a necessary step for most genomic/transcriptomic analyses, but it often requires complicated mechanisms to be integrated into a lab-on-a-chip device. Here, we present a simple, effective configuration for rapidly obtaining purified RNA from low concentration cell medium. This Total RNA Extraction Droplet Array (TREDA) utilizes an array of surface-adhering droplets to facilitate the transportation of magnetic purification beads seamlessly through individual buffer solutions without solid structures. The fabrication of TREDA chips is rapid and does not require a microfabrication facility or expertise. The process takes less than 5 minutes. When purifying mRNA from bulk marine diatom samples, its repeatability and extraction efficiency are comparable to conventional tube-based operations. We demonstrate that TREDA can extract the total mRNA of about 10 marine diatom cells, indicating that the sensitivity of TREDA approaches single-digit cell numbers. PMID:25519439

  13. Three-dimensional pattern formation of magnetically labeled microgel beads for biological tissue engineering

    NASA Astrophysics Data System (ADS)

    Kawamoto, H.; Inoue, H.; Nakamura, M.

    2009-03-01

    We commenced basic research on the three-dimensional (3D) pattern formation of microgel beads for applications in biological tissue engineering. In this new technique, microgel beads are premagnetized by doping them with magnetic nanoparticles. Living cells will be included in the beads for actual use. If a nonuniform magnetic field is applied to a solution containing these magnetized beads, the beads will align, contact, and form a 3D structure. The structure is controlled by the seed pattern of the magnetic particles plugged in a substrate and the profile of the magnetic field distribution. We constructed tubes, which imitate blood vessels, for demonstration using gel beads whose diameters are of the order of several tens of micrometers. The diameter of the demonstrated tube was less than 0.5 mm and its length was 6.6 mm, although living cells were not included in the beads. Numerical calculations by using the discrete element method were conducted to confirm the formation of the tube and to predict the effect of centrifugal force, which will be applied to fill cells in the space between magnetically patterned beads. Although this unique technology is in the nascent stage, this 3D pattern formation technique by the control of the magnetic field has potential to be one of the effective engineering technologies for manufacturing 3D patterned biological tissues in the future.

  14. Assessment of direct versus indirect magnetic bead-based T-cell isolation procedures followed by magnetic bead-based DNA isolation

    PubMed Central

    Rosenbaum, Anna; Bleck, Ellen; Schneider, Matthias; Pongratz, Georg; Vordenbäumen, Stefan

    2016-01-01

    Objective To compare direct and indirect bead-based T-cell isolation followed by magnetic bead-based DNA isolation. Methods T-cells were isolated by direct or indirect selection with magnetic bead coated antbiodies followed by magnetic bead-based automated DNA isolation in 10 healthy subjects. Purity of T-cells, purity of DNA (by A260/A280 ratio measurement) and DNA concentration were assessed. Results Direct and indirect labelling resulted in comparable T-cell purity (93.11±1.47% vs. 94.99±1.54%, p= 0.125) and DNA concentration per cell (50.97±14.15 ng/(mlxcell) vs. 49.53±13.62 ng/(mlxcell), p=0.492), while DNA purity was significantly higher after direct labelling (1.82±0.05 vs. 1.78±0.03, p=0.0488). Conclusions Both direct and indirect magnetic bead-based T-cell selection may be used prior to magnetic bead-based DNA isolation procedures. PMID:27547441

  15. Magnetic Beads-based Bioelectrochemical Immunoassay of Polycyclic Aromatic Hydrocarbons

    SciTech Connect

    Lin, Ying-Ying; Liu, Guodong; Wai, Chien M.; Lin, Yuehe

    2007-07-01

    A simple, rapid, and sensitive bioelectrochemical immunoassay method based on magnetic beads (MBs) has been developed to detect polycyclic aromatic hydrocarbons (PAHs). The principle of this bioassay is based on a direct competitive enzyme-linked immunosorbent assay using PAH-antibody-coated MBs and horseradish peroxidase (HRP)-labeled PAH (HRP-PAH). A magnetic process platform was used to mix and shake the samples during the immunoreactions and to separate free and unbound reagents after the liquid-phase competitive immunoreaction among PAH-antibody-coated MBs, PAH analyte, and HRP-PAH. After a complete immunoassay, the HRP tracers attached to MBs were transferred to a substrate solution containing 3, 3´, 5, 5´- tetramethylbenzidine (TMB) and hydrogen peroxide (H2O2) for electrochemical detection. The voltammetric characteristics of the substrate were investigated, and the reduction peak current of TMB was used to quantify the concentration of PAH. The different parameters, including the amount of HRP-PAH conjugates, the enzyme catalytic reaction time, and the pH of the supporting electrolyte that governs the analytical performance of the immunoassay have been studied in detail and optimized. The detection limit of 50 pg mL-1 was obtained under optimum experimental conditions. The performance of this bioelectrochemical magnetic immunoassay was successfully evaluated with tap water spiked with PAHs, indicating that this convenient and sensitive technique offers great promise for decentralized environmental applications.

  16. Magnetic tweezers with high permeability electromagnets for fast actuation of magnetic beads.

    PubMed

    Chen, La; Offenhäusser, Andreas; Krause, Hans-Joachim

    2015-04-01

    As a powerful and versatile scientific instrument, magnetic tweezers have been widely used in biophysical research areas, such as mechanical cell properties and single molecule manipulation. If one wants to steer bead position, the nonlinearity of magnetic properties and the strong position dependence of the magnetic field in most magnetic tweezers lead to quite a challenge in their control. In this article, we report multi-pole electromagnetic tweezers with high permeability cores yielding high force output, good maneuverability, and flexible design. For modeling, we adopted a piece-wise linear dependence of magnetization on field to characterize the magnetic beads. We implemented a bi-linear interpolation of magnetic field in the work space, based on a lookup table obtained from finite element simulation. The electronics and software were custom-made to achieve high performance. In addition, the effects of dimension and defect on structure of magnetic tips also were inspected. In a workspace with size of 0.1 × 0.1 mm(2), a force of up to 400 pN can be applied on a 2.8 μm superparamagnetic bead in any direction within the plane. Because the magnetic particle is always pulled towards a tip, the pulling forces from the pole tips have to be well balanced in order to achieve control of the particle's position. Active video tracking based feedback control is implemented, which is able to work at a speed of up to 1 kHz, yielding good maneuverability of the magnetic beads. PMID:25933874

  17. Magnetic tweezers with high permeability electromagnets for fast actuation of magnetic beads

    SciTech Connect

    Chen, La; Offenhäusser, Andreas; Krause, Hans-Joachim

    2015-04-15

    As a powerful and versatile scientific instrument, magnetic tweezers have been widely used in biophysical research areas, such as mechanical cell properties and single molecule manipulation. If one wants to steer bead position, the nonlinearity of magnetic properties and the strong position dependence of the magnetic field in most magnetic tweezers lead to quite a challenge in their control. In this article, we report multi-pole electromagnetic tweezers with high permeability cores yielding high force output, good maneuverability, and flexible design. For modeling, we adopted a piece-wise linear dependence of magnetization on field to characterize the magnetic beads. We implemented a bi-linear interpolation of magnetic field in the work space, based on a lookup table obtained from finite element simulation. The electronics and software were custom-made to achieve high performance. In addition, the effects of dimension and defect on structure of magnetic tips also were inspected. In a workspace with size of 0.1 × 0.1 mm{sup 2}, a force of up to 400 pN can be applied on a 2.8 μm superparamagnetic bead in any direction within the plane. Because the magnetic particle is always pulled towards a tip, the pulling forces from the pole tips have to be well balanced in order to achieve control of the particle’s position. Active video tracking based feedback control is implemented, which is able to work at a speed of up to 1 kHz, yielding good maneuverability of the magnetic beads.

  18. Microarrays

    ERIC Educational Resources Information Center

    Plomin, Robert; Schalkwyk, Leonard C.

    2007-01-01

    Microarrays are revolutionizing genetics by making it possible to genotype hundreds of thousands of DNA markers and to assess the expression (RNA transcripts) of all of the genes in the genome. Microarrays are slides the size of a postage stamp that contain millions of DNA sequences to which single-stranded DNA or RNA can hybridize. This…

  19. Development of a magnetic nanoparticles microarray for simultaneous and simple detection of foodborne pathogens.

    PubMed

    Li, Song; Liu, Hongna; Deng, Yan; Lin, Lin; He, Nongyue

    2013-07-01

    Foodborne diseases are a widespread and growing public health problem affecting both developed and developing countries, microbiologically contaminated food and water are the major causes of diarrhoeal diseases. Methods based on polymerase chain reaction (PCR) and microarrays are rapid and sensitive enough to detect very small quantities of microorganisms, however, the requirement for expensive equipments limits their application. In the present paper, we describe a method based on multiplex PCR and magnetic nanoparticles labelling for simultaneous detection of four major foodborne pathogens, including Escherichia coli O157:H7, Salmonella enterica, Vibrio cholera and Campylobacter jejuni. The process utilizes an oligonucleotide array onto which 5' biotinylated single strand PCR products were hybridized and visualized with streptavidin-coated magnetic nanoparticles (SA-MNPs), the signal from which could be detected by the naked eye, microscope or CCD camera. By employing SA-MNPs as visible labels, the microarray unambiguously distinguished all 4 pathogens with detection sensitivity up to 316 CFU/mL. Due to its high sensitivity, specificity and simple detection procedure, the magnetic bead assay provides a powerful tool for the detection and identification of foodborne pathogens in a modestly equipped laboratory. PMID:23909141

  20. On-chip magnetic separation of superparamagnetic beads for integrated molecular analysis

    NASA Astrophysics Data System (ADS)

    Florescu, Octavian; Wang, Kevan; Au, Patrick; Tang, Jimmy; Harris, Eva; Beatty, P. Robert; Boser, Bernhard E.

    2010-03-01

    We have demonstrated a postprocessed complementary metal oxide semiconductor (CMOS) integrated circuit (IC) capable of on-chip magnetic separation, i.e., removing via magnetic forces the nonspecifically bound magnetic beads from the detection area on the surface of the chip. Initially, 4.5 μm wide superparamagnetic beads sedimenting out of solution due to gravity were attracted to the detection area by a magnetic concentration force generated by flowing current through a conductor embedded in the IC. After sedimentation, the magnetic beads that did not bind strongly to the functionalized surface of the IC through a specific biochemical complex were removed by a magnetic separation force generated by flowing current through another conductor placed laterally to the detection area. As the spherical bead pivoted on the surface of the chip, the lateral magnetic force was further amplified by mechanical leveraging, and 50 mA of current flowing through the separation conductor placed 18 μm away from the bead resulted in 7.5 pN of tensile force on the biomolecular tether immobilizing the bead. This force proved high enough to break nonspecific interactions while leaving specific antibody-antigen bonds intact. A sandwich capture immunoassay on purified human immunoglobulin G showed strong correlation with a control enzyme linked immunosorbent assay and a detection limit of 10 ng/ml or 70 pM. The beads bound to the detection area after on-chip magnetic separation were detected optically. To implement a fully integrated molecular diagnostics platform, the on-chip magnetic separation functionality presented in this work can be readily combine with state-of-the art CMOS-based magnetic bead detection technology.

  1. The synchronization of superparamagnetic beads driven by a micro-magnetic ratchet.

    PubMed

    Gao, Lu; Gottron, Norman J; Virgin, Lawrence N; Yellen, Benjamin B

    2010-08-21

    We present theoretical, numerical, and experimental analyses on the non-linear dynamic behavior of superparamagnetic beads exposed to a periodic array of micro-magnets and an external rotating field. The agreement between theoretical and experimental results revealed that non-linear magnetic forcing dynamics are responsible for transitions between phase-locked orbits, sub-harmonic orbits, and closed orbits, representing different mobility regimes of colloidal beads. These results suggest that the non-linear behavior can be exploited to construct a novel colloidal separation device that can achieve effectively infinite separation resolution for different types of beads, by exploiting minor differences in their bead's properties. We also identify a unique set of initial conditions, which we denote the "devil's gate" which can be used to expeditiously identify the full range of mobility for a given bead type. PMID:20556295

  2. Self-assembled magnetic bead chains for sensitivity enhancement of microfluidic electrochemical biosensor platforms.

    PubMed

    Armbrecht, L; Dincer, C; Kling, A; Horak, J; Kieninger, J; Urban, G

    2015-11-21

    In this paper, we present a novel approach to enhance the sensitivity of microfluidic biosensor platforms with self-assembled magnetic bead chains. An adjustable, more than 5-fold sensitivity enhancement is achieved by introducing a magnetic field gradient along a microfluidic channel by means of a soft-magnetic lattice with a 350 μm spacing. The alternating magnetic field induces the self-assembly of the magnetic beads in chains or clusters and thus improves the perfusion and active contact between the analyte and the beads. The soft-magnetic lattices can be applied independent of the channel geometry or chip material to any microfluidic biosensing platform. At the same time, the bead-based approach achieves chip reusability and shortened measurement times. The bead chain properties and the maximum flow velocity for bead retention were validated by optical microscopy in a glass capillary. The magnetic actuation system was successfully validated with a biotin-streptavidin model assay on a low-cost electrochemical microfluidic chip, fabricated by dry-film photoresist technology (DFR). Labelling with glucose oxidase (GOx) permits rapid electrochemical detection of enzymatically produced H2O2. PMID:26394820

  3. On-chip magnetic bead-based DNA melting curve analysis using a magnetoresistive sensor

    NASA Astrophysics Data System (ADS)

    Rizzi, Giovanni; Østerberg, Frederik W.; Henriksen, Anders D.; Dufva, Martin; Hansen, Mikkel F.

    2015-04-01

    We present real-time measurements of DNA melting curves in a chip-based system that detects the amount of surface-bound magnetic beads using magnetoresistive magnetic field sensors. The sensors detect the difference between the amount of beads bound to the top and bottom sensor branches of the differential sensor geometry. The sensor surfaces are functionalized with wild type (WT) and mutant type (MT) capture probes, differing by a single base insertion (a single nucleotide polymorphism, SNP). Complementary biotinylated targets in suspension couple streptavidin magnetic beads to the sensor surface. The beads are magnetized by the field arising from the bias current passed through the sensors. We demonstrate the first on-chip measurements of the melting of DNA hybrids upon a ramping of the temperature. This overcomes the limitation of using a single washing condition at constant temperature. Moreover, we demonstrate that a single sensor bridge can be used to genotype a SNP.

  4. Magnetic Bead Based Immunoassay for Autonomous Detection of Toxins

    SciTech Connect

    Kwon, Y; Hara, C A; Knize, M G; Hwang, M H; Venkatesteswaran, K S; Wheeler, E K; Bell, P M; Renzi, R F; Fruetel, J A; Bailey, C G

    2008-05-01

    As a step towards toward the development of a rapid, reliable analyzer for bioagents in the environment, we are developing an automated system for the simultaneous detection of a group of select agents and toxins. To detect toxins, we modified and automated an antibody-based approach previously developed for manual medical diagnostics that uses fluorescent eTag{trademark} reporter molecules and is suitable for highly multiplexed assays. Detection is based on two antibodies binding simultaneously to a single antigen, one of which is labeled with biotin while the other is conjugated to a fluorescent eTag{trademark} through a cleavable linkage. Aqueous samples are incubated with the mixture of antibodies along with streptavidin-coated magnetic beads coupled to a photo-activatable porphyrin complex. In the presence of antigen, a molecular complex is formed where the cleavable linkage is held in proximity to the photoactivable group. Upon excitation at 680 nm, free radicals are generated, which diffuse and cleave the linkage, releasing the eTags{trademark}. Released eTags{trademark} are analyzed using capillary gel electrophoresis with laser-induced fluorescence detection. Limits of detection for ovalbumin and botulinum toxoid individually were 4 ng/mL (or 80 pg) and 16 ng/mL (or 320 pg), respectively, using the manual assay. In addition, we demonstrated the use of pairs of antibodies from different sources in a single assay to decrease the rate of false positives. Automation of the assay was demonstrated on a flow-through format with higher LODs of 125 ng/mL (or 2.5 ng) each of a mixture of ovalbumin and botulinum toxoid. This versatile assay can be easily modified with the appropriate antibodies to detect a wide range of toxins and other proteins.

  5. Magnetic Pycnoporus sanguineus-loaded alginate composite beads for removing dye from aqueous solutions.

    PubMed

    Yang, Chih-Hui; Shih, Ming-Cheng; Chiu, Han-Chen; Huang, Keng-Shiang

    2014-01-01

    Dye pollution in wastewater is a severe environmental problem because treating water containing dyes using conventional physical, chemical, and biological treatments is difficult. A conventional process is used to adsorb dyes and filter wastewater. Magnetic filtration is an emerging technology. In this study, magnetic Pycnoporus sanguineus-loaded alginate composite beads were employed to remove a dye solution. A white rot fungus, P. sanguineus, immobilized in alginate beads were used as a biosorbent to remove the dye solution. An alginate polymer could protect P. sanguineus in acidic environments. Superparamagnetic nanomaterials, iron oxide nanoparticles, were combined with alginate gels to form magnetic alginate composites. The magnetic guidability of alginate composites and biocompatibility of iron oxide nanoparticles facilitated the magnetic filtration and separation processes. The fungus cells were immobilized in loaded alginate composites to study the influence of the initial dye concentration and pH on the biosorption capacity. The composite beads could be removed easily post-adsorption by using a magnetic filtration process. When the amount of composite beads was varied, the results of kinetic studies of malachite green adsorption by immobilized cells of P. sanguineus fitted well with the pseudo-second-order model. The results indicated that the magnetic composite beads effectively adsorbed the dye solution from wastewater and were environmentally friendly. PMID:24945580

  6. Use of a magnetic field to modify and detect avalanche behavior on a conical bead pile

    NASA Astrophysics Data System (ADS)

    Johnson, Nathan; Lehman, Susan

    2015-03-01

    A conical bead pile subject to slow driving and an external magnetic field is used to test the effects of drop height and cohesion on avalanche statistics. Magnetically susceptible beads were dropped onto a pile from different heights and into different strengths of magnetic field. Avalanches were recorded by the change in mass as beads fall off the pile. For beads dropped from a low drop height with no cohesion, the avalanche size distribution follows a power law. As cohesion increases, we observe an increase in the probability of very large avalanches and decreases in the mid-size avalanches. The resulting bump in the avalanche distribution moves to larger avalanche size as the cohesion in the system is increased, matching the prediction by an analytic theory from a mean-field model of slip avalanches. The model also makes predictions for avalanche duration, which is not measurable with our current system. Since the steel beads are magnetized while in the applied magnetic field, their motion during an avalanche creates a change in magnetic flux. To detect this motion, we have placed a large-diameter pick-up coil around the pile. Results of the testing and calibration of this coil to measure avalanche duration are presented.

  7. Development of a Magnetic Beads Quantitative Detection System for Fast Diagnosis

    NASA Astrophysics Data System (ADS)

    Yamamoto, Yujiro; Morishita, Tomohiro; Matsuyama, Kenji; Takasa, Kenji; Shibasaki, Ichiro

    This paper reports the development and performance of a detection system for magnetic beads. The system consists of a semiconductor based magneto-resistance sensor for beads detection and a lateral flow kit. Detection of anti-gen of H.Influenza at concentration of 0.1ng/ml was performed with satisfactory sensitivity, showing the system to be a promising for immunoassay.

  8. Development and potential applications of microarrays based on fluorescent nanocrystal-encoded beads for multiplexed cancer diagnostics

    NASA Astrophysics Data System (ADS)

    Brazhnik, Kristina; Grinevich, Regina; Efimov, Anton E.; Nabiev, Igor; Sukhanova, Alyona

    2014-05-01

    Advanced multiplexed assays have recently become an indispensable tool for clinical diagnostics. These techniques provide simultaneous quantitative determination of multiple biomolecules in a single sample quickly and accurately. The development of multiplex suspension arrays is currently of particular interest for clinical applications. Optical encoding of microparticles is the most available and easy-to-use technique. This technology uses fluorophores incorporated into microbeads to obtain individual optical codes. Fluorophore-encoded beads can be rapidly analyzed using classical flow cytometry or microfluidic techniques. We have developed a new generation of highly sensitive and specific diagnostic systems for detection of cancer antigens in human serum samples based on microbeads encoded with fluorescent quantum dots (QDs). The designed suspension microarray system was validated for quantitative detection of (1) free and total prostate specific antigen (PSA) in the serum of patients with prostate cancer and (2) carcinoembryonic antigen (CEA) and cancer antigen 15-3 (CA 15-3) in the serum of patients with breast cancer. The serum samples from healthy donors were used as a control. The antigen detection is based on the formation of an immune complex of a specific capture antibody (Ab), a target antigen (Ag), and a detector Ab on the surface of the encoded particles. The capture Ab is bound to the polymer shell of microbeads via an adapter molecule, for example, protein A. Protein A binds a monoclonal Ab in a highly oriented manner due to specific interaction with the Fc-region of the Ab molecule. Each antigen can be recognized and detected due to a specific microbead population carrying the unique fluorescent code. 100 and 231 serum samples from patients with different stages of prostate cancer and breast cancer, respectively, and those from healthy donors were examined using the designed suspension system. The data were validated by comparing with the results of

  9. Ultrasensitive protein detection: a case for microfluidic magnetic bead-based assays.

    PubMed

    Tekin, H Cumhur; Gijs, Martin A M

    2013-12-21

    We review the use of magnetic micro- and nanoparticles ('magnetic beads') in microfluidic systems for ultrasensitive protein detection. During recent years magnetic beads have been used frequently in immunoassays, either as mobile substrates on which the target antigen is captured, as detection labels, or simultaneously as substrates and labels. The major part of the reviewed work has as application the detection of antibodies or disease biomarkers in serum or of biotoxins from food samples. Several of the most sensitive assays allow protein detection down to fg mL(-1) concentrations. We benchmark the performance of these microfluidic magnetic bead-based assays with the most promising earlier work and with alternative solutions. PMID:24145920

  10. Design criteria for developing low-resource magnetic bead assays using surface tension valves.

    PubMed

    Adams, Nicholas M; Creecy, Amy E; Majors, Catherine E; Wariso, Bathsheba A; Short, Philip A; Wright, David W; Haselton, Frederick R

    2013-01-01

    Many assays for biological sample processing and diagnostics are not suitable for use in settings that lack laboratory resources. We have recently described a simple, self-contained format based on magnetic beads for extracting infectious disease biomarkers from complex biological samples, which significantly reduces the time, expertise, and infrastructure required. This self-contained format has the potential to facilitate the application of other laboratory-based sample processing assays in low-resource settings. The technology is enabled by immiscible fluid barriers, or surface tension valves, which stably separate adjacent processing solutions within millimeter-diameter tubing and simultaneously permit the transit of magnetic beads across the interfaces. In this report, we identify the physical parameters of the materials that maximize fluid stability and bead transport and minimize solution carryover. We found that fluid stability is maximized with ≤0.8 mm i.d. tubing, valve fluids of similar density to the adjacent solutions, and tubing with ≤20 dyn/cm surface energy. Maximizing bead transport was achieved using ≥2.4 mm i.d. tubing, mineral oil valve fluid, and a mass of 1-3 mg beads. The amount of solution carryover across a surface tension valve was minimized using ≤0.2 mg of beads, tubing with ≤20 dyn/cm surface energy, and air separators. The most favorable parameter space for valve stability and bead transport was identified by combining our experimental results into a single plot using two dimensionless numbers. A strategy is presented for developing additional self-contained assays based on magnetic beads and surface tension valves for low-resource diagnostic applications. PMID:24403996

  11. Theoretical study of moving magnetic beads on an inclined plane and its application in the ratchet separation technique

    NASA Astrophysics Data System (ADS)

    Rashidi, M. M.; Johnson, S.; Yang, Z.

    2016-01-01

    For first time, motion of a magnetic bead ascending an inclined surface is investigated. The translational and rotational velocities of magnetic beads traveling on an inclined plane in the creeping flow regime are studied. The governing equations considering lift force and magnetic torque are obtained. Rolling and slipping cases are studied in detail. It is shown that the lift force effect is critical for large values of sedimentation Reynolds number (Res) and negligible for small values of Res. This method is applicable for neutrally buoyant and heavy magnetic bead motion. Practical application of this study is implemented in the ratchet configuration for separation of magnetic beads with different sizes. This is applicable for novel applications such as drug delivery, magnetic tweezers, and magnetic actuated stiffness testing systems which require accurate magnetic bead sizes for accurate function.

  12. Design of a Microfluidic Chip for Magnetic-Activated Sorting of One-Bead-One-Compound Libraries.

    PubMed

    Cho, Choi-Fong; Lee, Kyungheon; Speranza, Maria-Carmela; Bononi, Fernanda C; Viapiano, Mariano S; Luyt, Leonard G; Weissleder, Ralph; Chiocca, E Antonio; Lee, Hakho; Lawler, Sean E

    2016-06-13

    Molecular targeting using ligands specific to disease markers has shown great promise for early detection and directed therapy. Bead-based combinatorial libraries have served as powerful tools for the discovery of novel targeting agents. Screening platforms employing magnetic capture have been used to achieve rapid and efficient identification of high-affinity ligands from one-bead-one-compound (OBOC) libraries. Traditional manual methodologies to isolate magnetized "hit" beads are tedious and lack accuracy, and existing instruments to expedite bead sorting tend to be costly and complex. Here, we describe the design and construction of a simple and inexpensive microfluidic magnetic sorting device using standard photolithography and soft lithography approaches to facilitate high-throughput isolation of magnetized positive hit beads from combinatorial libraries. We have demonstrated that the device is able to sort magnetized beads with superior accuracy compared to conventional manual sorting approaches. This chip offers a very convenient yet inexpensive alternative for screening OBOC libraries. PMID:27124678

  13. Kinetics of mercury ions removal from synthetic aqueous solutions using by novel magnetic p(GMA-MMA-EGDMA) beads.

    PubMed

    Bayramoğlu, Gülay; Arica, M Yakup

    2007-06-01

    Poly(glycidylmethacrylate-methylmethacrylate), p(GMA-MMA-EGDMA), magnetic beads were prepared via suspension polymerization in the presence of ferric ions. The epoxy groups of the beads were converted into amino groups via ring opening reaction of the ammonia and, the aminated magnetic beads were used for the removal of Hg(II) ions from aqueous solution in a batch experiment and in a magnetically stabilized fluidized bed reactor (MFB). The magnetic p(GMA-MMA-EGDMA) beads were characterized with scanning electron microscope (SEM), FT-IR and ESR spectrophotometers. The optimum removal of Hg(II) ions was observed at pH 5.5. The maximum adsorption capacity of Hg(II) ions by using the magnetic beads was 124.8+/-2.1 mgg(-1) beads. In the continuous MFB reactor, Hg(II) ions adsorption capacity of the magnetic beads decreased with an increase in the flow-rate. The maximum adsorption capacity of the magnetic beads in the MFB reactor was 139.4+/-1.4 mgg(-1). The results indicate that the magnetic beads are promising for use in MFB for removal of Hg(II) ions from aqueous solution and/or waste water treatment. PMID:17118552

  14. Adsorption of a cationic surfactant by a magsorbent based on magnetic alginate beads.

    PubMed

    Obeid, Layaly; El Kolli, Nadia; Dali, Noëlle; Talbot, Delphine; Abramson, Sébastien; Welschbillig, Mathias; Cabuil, Valérie; Bée, Agnès

    2014-10-15

    Adsorption of cetylpyridinium chloride (CPC), a cationic surfactant, by magnetic alginate beads (MagAlgbeads) was investigated. The magnetic adsorbent (called magsorbent) was prepared by encapsulation of magnetic functionalized nanoparticles in an alginate gel. The influence on CPC adsorption of several parameters such as contact time, pH and initial surfactant concentration was studied. The equilibrium isotherm shows that adsorption occurs through both electrostatic interactions with charge neutralization of the carboxylate groups of the beads and hydrophobic interactions inducing the formation of surfactant aggregates in the beads. The dosage of calcium ions released in the solution turns out to be a useful tool for understanding the adsorption mechanisms. Adsorption is accompanied by a shrinking of the beads that corresponds to a 45% reduction of the volume. Adsorption kinetic experiments show that equilibrium time is strongly dependent on the surfactant concentration, which monitors the nature of the interactions. On the other hand, since the pH affects the ionization state of adsorption sites, adsorption depends on the pH solution, maximum adsorption being obtained in a large pH range (3.2-12) in agreement with the pKa value of alginate (pKa=3.4-4.2). Finally, due to the formation of micelle-like surfactants aggregates in the magnetic alginate beads, they could be used as a new efficient magsorbent for hydrophobic pollutants. PMID:25086393

  15. Magnetic bead-quantum dot assay for detection of a biomarker for traumatic brain injury.

    PubMed

    Kim, Chloe; Searson, Peter C

    2015-11-14

    Current diagnostic methods for traumatic brain injury (TBI), which accounts for 15% of all emergency room visits, are limited to neuroimaging modalities. The challenges of accurate diagnosis and monitoring of TBI have created the need for a simple and sensitive blood test to detect brain-specific biomarkers. Here we report on an assay for detection of S100B, a putative biomarker for TBI, using antibody-conjugated magnetic beads for capture of the protein, and antibody-conjugated quantum dots for optical detection. From Western Blot, we show efficient antigen capture and concentration by the magnetic beads. Using magnetic bead capture and quantum dot detection in serum samples, we show a wide detection range and detection limit below the clinical cut-off level. PMID:26457768

  16. Magnetic bead-quantum dot assay for detection of a biomarker for traumatic brain injury

    NASA Astrophysics Data System (ADS)

    Kim, Chloe; Searson, Peter C.

    2015-10-01

    Current diagnostic methods for traumatic brain injury (TBI), which accounts for 15% of all emergency room visits, are limited to neuroimaging modalities. The challenges of accurate diagnosis and monitoring of TBI have created the need for a simple and sensitive blood test to detect brain-specific biomarkers. Here we report on an assay for detection of S100B, a putative biomarker for TBI, using antibody-conjugated magnetic beads for capture of the protein, and antibody-conjugated quantum dots for optical detection. From Western Blot, we show efficient antigen capture and concentration by the magnetic beads. Using magnetic bead capture and quantum dot detection in serum samples, we show a wide detection range and detection limit below the clinical cut-off level.Current diagnostic methods for traumatic brain injury (TBI), which accounts for 15% of all emergency room visits, are limited to neuroimaging modalities. The challenges of accurate diagnosis and monitoring of TBI have created the need for a simple and sensitive blood test to detect brain-specific biomarkers. Here we report on an assay for detection of S100B, a putative biomarker for TBI, using antibody-conjugated magnetic beads for capture of the protein, and antibody-conjugated quantum dots for optical detection. From Western Blot, we show efficient antigen capture and concentration by the magnetic beads. Using magnetic bead capture and quantum dot detection in serum samples, we show a wide detection range and detection limit below the clinical cut-off level. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr05608j

  17. Fine-tuning of magnetic and microfluidic viscous forces for specific magnetic bead-based immunocomplex formation

    NASA Astrophysics Data System (ADS)

    Cornaglia, M.; Tekin, H. C.; Lehnert, T.; Gijs, M. A. M.

    2013-08-01

    We investigate the working principle of a novel type of microfluidic sandwich immunoassay, as used for the detection of biomarkers. The heterogeneous assay is based on the specific interactions between an array of functionalized superparamagnetic beads and a flow of secondary superparamagnetic beads that carry the antigens and are simultaneously used as detection labels. We identify the main forces governing the immunoassay performance and develop a combined finite element method/analytical model to predict and control these forces. The clue for the improved assay specificity is in the fine-tuning of inter-bead magnetic dipolar and microfluidic viscous forces, which allows strongly reducing non-specific interactions, while enhancing the specific formation of immunocomplexes. We exploit our theoretical model to explain the enhanced sensitivity of magnetic bead-based immunoassay experiments performed in microfluidic chips.

  18. Alginate/magnetite hybrid beads for magnetically stimulated release of dopamine.

    PubMed

    Kondaveeti, Stalin; Cornejo, Daniel R; Petri, Denise Freitas Siqueira

    2016-02-01

    Hybrid beads composed of magnetite nanoparticles (MNP) and alginate (Alg) were synthesized and coded as Alg-MNP. They were incubated in dopamine (DOPA) solution (5 g/L), at pH 7.4 and 8 °C, during 12 h, promoting the DOPA loaded magnetic beads, coded as Alg-MNP/DOPA. The release of DOPA was further evaluated in the absence and the presence of external magnetic field (EMF) of 0.4 T. The products Alg-MNP and Alg-MNP/DOPA were characterized by scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS), Fourier transform infrared vibrational spectroscopy (FTIR), UV spectrophotometry, thermogravimetric analyses (TGA), inductively coupled plasma atomic emission spectroscopy (ICP-AES) analyses and superconducting quantum interference device (SQUID) magnetometer. The magnetic and chemical properties of Alg-MNP beads were not affected by DOPA loading. The incorporation of DOPA into the beads depended on the pH and on the negative charge density. At pH 7.4 38% of DOPA were loaded into Alg-MNP beads, whereas at pH 2 or using neat Alg beads (lower charge density than Alg-MNP) the loading efficiency decreased to one third or less. In the absence of EMF, 24% of the loaded DOPA was released from Alg-MNP at pH 7.4 over a period of 26 h. The released amount increased to 33% under the stimulus of EMF. A model was proposed to explain the loading efficiency of charged drugs, as DOPA, into hybrid beads and the role played by EMF on delivery systems, where drug and matrix are oppositely charged. The results suggest that the alginate combined with magnetite nanoparticles is a promising system for release of DOPA in the presence of EMF. PMID:26674837

  19. Synthesis of magnetic alginate hybrid beads for efficient chromium (VI) removal.

    PubMed

    Gopalakannan, Venkatrajan; Viswanathan, Natrayasamy

    2015-01-01

    Recently magnetic bio-composites have attracted the attention of scientists because of their unique characteristics like selectivity and high sorption capacity. In the present study, Fe3O4@Alg-Ce magnetic composite beads were developed by incorporating Fe3O4 particles onto alginate (Alg) biopolymer followed by cross-linking with Ce(3+) ions. The synthesized magnetic beads were characterized using FTIR and SEM with EDAX analysis and utilized for chromium (VI) removal in batch mode. A comparative adsorption performance of Fe3O4 particles, calcium alginate (CaAlg) composite and Fe3O4@Alg-Ce magnetic hybrid beads was made. The magnetic alginate beads possess an enhanced SC of 14.29 mg/g than CaAlg composite and Fe3O4 particles which possess SC of 9.45 and 9.72 mg/g respectively. The various sorption influencing parameters like contact time, pH, challenger anions, initial chromium concentration and temperature were optimized. The adsorption process was explained using Freundlich and Langmuir isotherms. The sorption kinetics was fitted well with the pseudo second order and intra particle diffusion model. The calculated thermodynamic parameters indicate the nature of chromium sorption is spontaneous and endothermic. PMID:25256552

  20. Design Considerations for CMOS-Integrated Hall-Effect Magnetic Bead Detectors for Biosensor Applications

    PubMed Central

    Skucha, K.; Gambini, S.; Liu, P.; Megens, M.; Kim, J.; Boser, BE

    2014-01-01

    We describe a design methodology for on-chip magnetic bead label detectors based on Hall-effect sensors. Signal errors caused by the label-binding process and other factors that limit the minimum detection area are quantified and adjusted to meet typical assay accuracy standards. The methodology is demonstrated by designing an 8192 element Hall sensor array, implemented in a commercial 0.18 μm CMOS process with single-mask postprocessing. The array can quantify a 1% surface coverage of 2.8 μm beads in 30 seconds with a coefficient of variation of 7.4%. This combination of accuracy and speed makes this technology a suitable detection platform for biological assays based on magnetic bead labels. PMID:25031503

  1. Co(II) removal by magnetic alginate beads containing Cyanex 272.

    PubMed

    Ngomsik, Audrey-Flore; Bee, Agnès; Siaugue, Jean-Michel; Talbot, Delphine; Cabuil, Valérie; Cote, Gérard

    2009-07-30

    In this study, a series of batch experiments is conducted to investigate the ability of magnetic alginate beads containing Cyanex 272 to remove Co(II) ions from aqueous solutions. Equilibrium sorption experiments show a Co(II) uptake capacity of 0.4 mmol g(-1). The data are successfully modelled with a Langmuir equation. A series of kinetics experiments is then carried out and a pseudo-second order equation is used to fit the experimental data. The effect of pH on the sorption of Co(II) ions is also investigated. Desorption experiments by elution of the loaded beads with nitric acid at pH 1 show that the magnetic alginate beads could be reused without significant losses of their initial properties even after 3 adsorption-desorption cycles. PMID:19157703

  2. Performance of dye-affinity beads for aluminium removal in magnetically stabilized fluidized bed

    PubMed Central

    Yavuz, Handan; Say, Ridvan; Andaç, Müge; Bayraktar, Necmi; Denizli, Adil

    2004-01-01

    Background Aluminum has recently been recognized as a causative agent in dialysis encephalopathy, osteodystrophy, and microcytic anemia occurring in patients with chronic renal failure who undergo long-term hemodialysis. Only a small amount of Al(III) in dialysis solutions may give rise to these disorders. Methods Magnetic poly(2-hydroxyethyl methacrylate) (mPHEMA) beads in the size range of 80–120 μm were produced by free radical co-polymerization of HEMA and ethylene dimethacrylate (EDMA) in the presence of magnetite particles (Fe3O4). Then, metal complexing ligand alizarin yellow was covalently attached onto mPHEMA beads. Alizarin yellow loading was 208 μmol/g. These beads were used for the removal of Al(III) ions from tap and dialysis water in a magnetically stabilized fluidized bed. Results Al(III) adsorption capacity of the beads decreased with an increase in the flow-rate. The maximum Al(III) adsorption was observed at pH 5.0. Comparison of batch and magnetically stabilized fluidized bed (MSFB) maximum capacities determined using Langmuir isotherms showed that dynamic capacity (17.5 mg/g) was somewhat higher than the batch capacity (11.8 mg/g). The dissociation constants for Al(III) were determined using the Langmuir isotherm equation to be 27.3 mM (MSFB) and 6.7 mM (batch system), indicating medium affinity, which was typical for pseudospecific affinity ligands. Al(III) ions could be repeatedly adsorbed and desorbed with these beads without noticeable loss in their Al(III) adsorption capacity. Conclusions Adsorption of Al(III) demonstrate the affinity of magnetic dye-affinity beads. The MSFB experiments allowed us to conclude that this inexpensive sorbent system may be an important alternative to the existing adsorbents in the removal of aluminium. PMID:15329149

  3. Characterizing protein modifications by reactive metabolites using magnetic bead bioreactors and LC-MS/MS.

    PubMed

    Li, Dandan; Fu, You-Jun; Rusling, James F

    2015-03-18

    We report here label-free metabolite-protein adduct detection and identification employing magnetic beads coated with metabolic enzymes as bioreactors to generate metabolites and possible metabolite-protein adducts for analysis by liquid chromatography-tandem mass spectrometry. PMID:25693065

  4. Specificity and kinetics of norovirus binding to magnetic bead- conjugated histo-blood group antigens

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Histo-blood group antigens (HBGA) have been identified as candidate receptors for human norovirus (NOR). Type A, type H1, and Lewis histo-blood group antigens (HBGAs) in humans have been identified as major targets for NOR binding. Pig HBGA-conjugated magnetic beads have been utilized as a means ...

  5. Use of magnetic beads for tissue DNA extraction and IS6110 Mycobacterium tuberculosis PCR.

    PubMed Central

    Caldarelli-Stefano, R; Vago, L; Bonetto, S; Nebuloni, M; Costanzi, G

    1999-01-01

    Polymerase chain reaction (PCR) techniques are used increasingly for the diagnosis of Mycobacterium tuberculosis infection and can be used on the DNA obtained from both frozen and formalin fixed, paraffin wax embedded tissues. However, the extraction of DNA by means of the conventional phenol/chloroform method is time consuming and requires the use of potentially dangerous chemical reagents. This paper describes a method based upon the use of magnetic beads for the extraction of M tuberculosis DNA from both routinely formalin fixed, paraffin wax embedded tissues and frozen tissues. Magnetic bead extracted DNA from brain, lymph node, and lung tissues collected from patients with human immunodeficiency virus and tuberculosis was compared with that extracted using the phenol/chloroform method. The magnetic bead extraction procedure requires less than two hours, including the time necessary to dewax the tissue sections. In all cases, the DNA extracted with both methods was amplified successfully by PCR for the M tuberculosis IS6110 sequence. Magnetic bead DNA extraction can be used on both frozen and archival tissues: the method is reliable, simple, sensitive, and rapid; in addition, it does not use hazardous procedures or specialised laboratory equipment and can be used for routine DNA isolation from various human tissues. PMID:10621838

  6. Characterizing Protein Modifications by Reactive Metabolites using Magnetic Bead Bioreactors and LC-MS/MS

    PubMed Central

    Li, Dandan; Fu, You-Jun; Rusling, James F.

    2015-01-01

    We report here label-free metabolite-protein adduct detection and identification employing magnetic beads coated with metabolic enzymes as bioreactors to generate metabolites and possible metabolite-protein adducts for analysis by liquid chromatography-tandem mass spectrometry. PMID:25693065

  7. Attempt to remove peanut allergens from peanut extracts, using IgE-attached magnetic beads.

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Immunoglobulin E (IgE) antibodies from sera of peanut-allergic individuals are known to bind specifically to major peanut allergens, Ara h 1 and Ara h 2. The objective of this study was to determine the efficiency of magnetic beads (Dynabeads) attached with IgE antibodies in the removal of major pea...

  8. A multi-purpose ultrasonic streaming mixer for integrated magnetic bead ELISAs

    NASA Astrophysics Data System (ADS)

    Brandhoff, Lukas; Zirath, Helene; Salas, Mariugenia; Haller, Anna; Peham, Johannes; Wiesinger-Mayr, Herbert; Spittler, Andreas; Schnetz, Guntram; Lang, Walter; Vellekoop, Michael J.

    2015-10-01

    We present an ultrasonic streaming mixer for disposable and on-chip magnetic bead ELISAs. The ultrasonic transducer is placed at system-level to keep cost per chip as low as possible, and is coupled to the chip by means of a solid ultrasonic horn. The system provides mixing of liquids, as well as dispersion of the superparamagnetic beads in the ELISA. Additionally it can be used clean the chamber surface from nonspecifically bound proteins during the washing steps in the ELISA protocol. Using our system the time for the ELISA protocol has been greatly reduced down to 30 min.

  9. Antibody-integrated and functionalized graphite-encapsulated magnetic beads, produced using ammonia gas plasma technology, for capturing Salmonella.

    PubMed

    Sakudo, Akikazu; Chou, Han; Nagatsu, Masaaki

    2015-03-01

    Salmonella spp. is the single and most important causative agent of foodborne infections, especially involving foods such as eggs, milk and meat. To prevent infection, a reliable surveillance system is required that can quickly and sensitively detect Salmonella. Here, we describe the development of antibody-integrated magnetic beads that are functionalized by a novel strategy using ammonia gas plasma. Ammonia plasma, produced by a radio frequency (RF) power supply, was allowed to react with the surface of graphite-encapsulated magnetic beads, resulting in the introduction of amino groups. An anti-Salmonella antibody was then anchored by sulfide groups present on the protein surface to the amino groups of the magnetic beads via N-succinimidyl 3-(2-pyridyldithio) propionate (SPDP). The potential usefulness of these magnetic beads for capturing Salmonella was examined as follows. The beads were incubated with Salmonella in liquid medium and then separated from the supernatant by applying a magnetic field. After thorough washing, adsorption of Salmonella to the beads was confirmed by immunochromatography, polymerase chain reaction and a direct culture assay. Our findings indicate that the capture and concentration of Salmonella using the antibody-integrated magnetic beads was more efficient than commercial Dynabeads® anti-Salmonella, which are conventionally used for concentrating Salmonella from liquid cultures. We believe this novel bead technology will contribute to the enhanced detection of Salmonella. PMID:25660257

  10. Immobilization of lipase onto micron-size magnetic beads.

    PubMed

    Liu, Xianqiao; Guan, Yueping; Shen, Rui; Liu, Huizhou

    2005-08-01

    A novel and economical magnetic poly(methacrylate-divinylbenzene) microsphere (less than 8 microm in diameter) was synthesized by the modified suspension polymerization of methacrylate and cross-linker divinylbenzene in the presence of magnetic fluid. Then, surface aminolysis was employed to obtain a high content of surface amino groups (0.40-0.55 mmolg(-1) supports). The morphology and properties of these magnetic supports were characterized with scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy and a vibrating sample magnetometer. These magnetic supports exhibited superparamagnetism with a high specific saturation magnetization (sigma(s)) of 14.6 emicrog(-1). Candida cylindracea lipase was covalently immobilized on the amino-functionalized magnetic supports with the activity recovery up to 72.4% and enzyme loading of 34.0 mgg(-1) support, remarkably higher than the previous studies. The factors involved in the activity recovery and enzymatic properties of the immobilized lipase prepared were studied in comparison with free lipase, for which olive oil was chosen as the substrate. The results show that the immobilized lipase has good stability and reusability after recovery by magnetic separation within 20s. PMID:15998604

  11. Capture and Concentration of Waterborne Pathogens Using Lectin and Antibody Coupled Magnetic Beads

    SciTech Connect

    Bennett, Alena M.; Ozanich, Rich M.

    2005-01-01

    Capture and Concentration of Waterborne Pathogens Using Lectin and Antibody Coupled Magnetic Beads. ALENA BENNETT (University of Puget Sound, Tacoma, WA, 98416) RICHARD M. OZANICH, JR. (Pacific Northwest National Laboratory, Richland, WA 99352). The primary challenge of the surveillance of natural and introduced biological threats in large water samples is the purification and concentration process. A method for simultaneously capturing many types of biological pathogens is desired. Lectins coupled with magnetic beads were studied due to their ability to bind to the carbohydrates on the surfaces of cells. With lectin coupled beads we attempted to trap Escherichia coli, Bacillus subtilis, and Brevundimonas diminuta. Also E. coli antibody coupled beads were tested for their effectiveness at concentrating E. coli cells. Bench top indirect and direct cell capture methods were studied for both lectins and antibodies. The indirect method was found to be more effective for cell concentration. Experiments are underway to understand the differences in the two approaches and improve the direct capture method for implementation on an online automated system.

  12. A magnetic bead-based ligand binding assay to facilitate human kynurenine 3-monooxygenase drug discovery.

    PubMed

    Wilson, Kris; Mole, Damian J; Homer, Natalie Z M; Iredale, John P; Auer, Manfred; Webster, Scott P

    2015-02-01

    Human kynurenine 3-monooxygenase (KMO) is emerging as an important drug target enzyme in a number of inflammatory and neurodegenerative disease states. Recombinant protein production of KMO, and therefore discovery of KMO ligands, is challenging due to a large membrane targeting domain at the C-terminus of the enzyme that causes stability, solubility, and purification difficulties. The purpose of our investigation was to develop a suitable screening method for targeting human KMO and other similarly challenging drug targets. Here, we report the development of a magnetic bead-based binding assay using mass spectrometry detection for human KMO protein. The assay incorporates isolation of FLAG-tagged KMO enzyme on protein A magnetic beads. The protein-bound beads are incubated with potential binding compounds before specific cleavage of the protein-compound complexes from the beads. Mass spectrometry analysis is used to identify the compounds that demonstrate specific binding affinity for the target protein. The technique was validated using known inhibitors of KMO. This assay is a robust alternative to traditional ligand-binding assays for challenging protein targets, and it overcomes specific difficulties associated with isolating human KMO. PMID:25296660

  13. Combination of carboxymethyl chitosan-coated magnetic nanoparticles and chitosan-citrate complex gel beads as a novel magnetic adsorbent.

    PubMed

    Mi, Fwu-Long; Wu, Shao-Jung; Chen, Yung-Chih

    2015-10-20

    Magnetic chitosan beads were synthesized by incorporating N,O-carboxymethyl chitosan-coated magnetic nanoparticles (NOCC-MNPs) into chitosan-citrate gel beads (CCGBs) for adsorbing Cu(II) ions. An increase of Cu(II) adsorption capacity was due to the combined chelation effects from the electron-donating functional groups in the CCGBs and NOCC-MNPs. Moreover, the paramagnetic susceptibility of Cu(II) citrate chelates could further improve the Cu(II) adsorption efficiency through the force of magnetic attraction. The adsorption data of the magnetic CCGBs fitted well with the Freundlich model, whereas the adsorption kinetics followed the pseudo-second-order kinetic model. The maximal adsorption capacity as estimated by the Langmuir model was 294.11mg/g. The adsorption thermodynamic parameters indicated that the involved process should be spontaneous and exothermic. PMID:26256183

  14. A tosyl-activated magnetic bead cellulose as solid support for sensitive protein detection.

    PubMed

    Yan, Junhong; Horák, Daniel; Lenfeld, Jiří; Hammond, Maria; Kamali-Moghaddam, Masood

    2013-09-10

    Magnetic bead cellulose (MBC) was prepared using sol-gel transition of viscose in the presence of maghemite (γ-Fe₂O₃) nanoparticles. The MBC particles were then activated with p-toluenesulfonyl chloride to yield tosyl-activated magnetic bead cellulose (MBC-Ts). The microspheres were characterized by light and electron microscopy, elemental analysis and atomic absorption spectroscopy to determine morphology, size, polydispersity and content of iron and tosyl groups. The functionality of the MBC-Ts microspheres was demonstrated using proximity ligation assay (PLA) to detect vascular endothelial growth factor in femtomolar concentration range. The MBC-Ts microspheres performed equally well as commercially available microparticles that are routinely used as solid support in solid phase PLA. PMID:23811391

  15. Magnetic bead-based reverse colorimetric immunoassay strategy for sensing biomolecules.

    PubMed

    Gao, Zhuangqiang; Xu, Mingdi; Hou, Li; Chen, Guonan; Tang, Dianping

    2013-07-16

    A novel reverse colorimetric immunoassay (RCIA) strategy was for the first time designed and utilized for sensitive detection of low-abundance protein (prostate-specific antigen, PSA, used in this case) in biological fluids by coupling highly catalytic efficient catalase with magnetic bead-based peroxidase mimics. To construct such a RCIA system, two nanostructures including magnetic beads and gold nanoparticles were first synthesized and functionalized with anti-PSA capture antibody and catalase/anti-PSA detection antibody, respectively. Thereafter, a specific sandwich-type immunoassay format was employed for determination of PSA by using functional gold nanoparticles as enzymatic bioreactors and anti-PSA-conjugated magnetic beads as a colorimetric developer. The carried catalase, followed by the sandwiched immunocomplex, partially consumed the added hydrogen peroxide in the detection solution, which slowed down the catalytic efficiency of magnetic bead-based peroxidase mimics toward TMB/H2O2, thereby weakening the visible color and decreasing the colorimetric density. Different from conventional colorimetric immunoassay, the RCIA method determined the residual hydrogen peroxide in the substrate after consumption. Under the optimal conditions, the developed RCIA exhibited a wide dynamic range of 0.05-20 ng mL(-1) toward PSA with a detection limit of 0.03 ng mL(-1) at the 3Sblank level. Intra- and interassay coefficients of variation were below 6.1% and 9.3%, respectively. Additionally, the methodology was further validated for the analysis of 12 PSA clinical serum specimens, giving results in good accordance with those obtained by the commercially available enzyme-linked immunosorbent assay (ELISA) method. PMID:23806145

  16. Concentric Magnetic Structures for Magnetophoretic Bead Collection, Cell Trapping and Analysis of Cell Morphological Changes Caused by Local Magnetic Forces

    PubMed Central

    Huang, Chen-Yu; Wei, Zung-Hang

    2015-01-01

    Concentric magnetic structures (ring and square) with domain wall (DW) pinning geometry are designed for biological manipulation. Magnetic beads collection was firstly demonstrated to analyse the local magnetic field generated by DWs and the effective regions to capture magnetic targets of size 1 μm. Primary mouse embryonic fibroblasts (MEFs) are magnetically labeled by internalizing poly (styrene sulfonic acid) stabilized magnetic nanoparticles (PSS-MNPs) and then are selectively trapped by head-to-tail DWs (HH DWs) or tail-to-tail DWs (TT DWs) to be arranged into linear shape or cross shape. The morphologies and the nuclear geometry of the cells growing on two kinds of concentric magnetic structures are shown to be distinctive. The intracellular magnetic forces generated by the local magnetic field of DWs are found to influence the behaviour of cells. PMID:26270332

  17. Salmonella detection in a microfluidic channel using orbiting magnetic beads

    NASA Astrophysics Data System (ADS)

    Ballard, Matt; Mills, Zachary; Owen, Drew; Hanasoge, Srinivas; Hesketh, Peter; Alexeev, Alexander

    2015-03-01

    We use three-dimensional simulations to model the detection of salmonella in a complex fluid sample in a microfluidic channel. Salmonella is captured using magnetic microbeads orbiting around soft ferromagnetic discs at the microchannel bottom subjected to a rotating external magnetic field. Numerical simulations are used to model the dynamics of salmonella and microbeads throughout the detection process. We examine the effect of the channel geometry on the salmonella capture, and the forces applied to the salmonella as it is dragged through the fluid after capture. Our findings guide the design of a lab-on-a-chip device to be used for detection of salmonella in food samples in a way that ensures that salmonella captured by orbiting microbeads are preserved until they can be extracted from the system for testing, and are not washed away by the fluid flow or damaged due to the experience of excessive stresses. Such a device is needed to detect bacteria at the food source and prevention of consumption of contaminated food, and also can be used for the detection of a variety of biomaterials of interest from complex fluid samples. Support from USDA and NSF is gratefully acknowledged.

  18. An integrated microfluidic biochemical detection system for protein analysis with magnetic bead-based sampling capabilities.

    PubMed

    Choi, Jin-Woo; Oh, Kwang W; Thomas, Jennifer H; Heineman, William R; Halsall, H Brian; Nevin, Joseph H; Helmicki, Arthur J; Henderson, H Thurman; Ahn, Chong H

    2002-02-01

    This paper presents the development and characterization of an integrated microfluidic biochemical detection system for fast and low-volume immunoassays using magnetic beads, which are used as both immobilization surfaces and bio-molecule carriers. Microfluidic components have been developed and integrated to construct a microfluidic biochemical detection system. Magnetic bead-based immunoassay, as a typical example of biochemical detection and analysis, has been successfully performed on the integrated microfluidic biochemical analysis system that includes a surface-mounted biofilter and electrochemical sensor on a glass microfluidic motherboard. Total time required for an immunoassay was less than 20 min including sample incubation time, and sample volume wasted was less than 50 microl during five repeated assays. Fast and low-volume biochemical analysis has been successfully achieved with the developed biofilter and immunosensor, which is integrated to the microfluidic system. Such a magnetic bead-based biochemical detection system, described in this paper, can be applied to protein analysis systems. PMID:15100857

  19. Specific capture of the hydrolysate on magnetic beads for sensitive detecting plant vacuolar processing enzyme activity.

    PubMed

    Zhou, Jun; Cheng, Meng; Zeng, Lizhang; Liu, Weipeng; Zhang, Tao; Xing, Da

    2016-05-15

    Conventional plant protease detection always suffers from high background interference caused by the complex coloring metabolites in plant cells. In this study, a bio-modified magnetic beads-based strategy was developed for sensitive and quantitative detection of plant vacuolar processing enzyme (VPE) activity. Cleavage of the peptide substrate (ESENCRK-FITC) after asparagine residue by VPE resulted in the 2-cyano-6-amino-benzothiazole (CABT)-functionalized magnetic beads capture of the severed substrate CRK-FITC via a condensation reaction between CABT and cysteine (Cys). The catalytic activity was subsequently obtained by the confocal microscopy imaging and flow cytometry quantitative analysis. The sensor system integrated advantages of (i) the high efficient enrichment and separation capabilities of magnetic beads and (ii) the catalyst-free properties of the CABT-Cys condensation reaction. It exhibited a linear relationship between the fluorescence signal and the concentration of severed substrate in the range of 10-600 pM. The practical results showed that, compared with normal growth conditions, VPE activity was increased by 2.7-fold (307.2 ± 25.3 μM min(-1)g(-1)) upon cadmium toxicity stress. This platform effectively overcame the coloring metabolites-caused background interference, showing fine applicability for the detection of VPE activity in real samples. The strategy offers great sensitivity and may be further extended to other protease activity detection. PMID:26797250

  20. Cetylpyridinium chloride/magnetic alginate beads: an efficient system to remove p-nitrophenol from wastewater

    NASA Astrophysics Data System (ADS)

    Obeid, Layaly; Bee, Agnes; Talbot, Delphine; Abramson, Sebastien; Welschbillig, Mathias

    2014-05-01

    The adsorption process is one of the most efficient methods to remove pollutants from wastewater provided that suitable adsorbents are used. In order to produce environmentally safe adsorbents, natural polymers have received increasing attention in recent years. Thus, alginate, a polysaccharide extracted from brown seaweeds, is extensively used as inexpensive, non-toxic and efficient biosorbent. Furthermore, it has been shown that the encapsulation of magnetic materials in alginate beads facilitates their recovery from wastewater after the adsorption step, by the use of an external magnetic field gradient, obtained with a magnet or an electromagnet [1, 2]. In the present work, we have studied the adsorption affinity of magnetic alginate beads (called magsorbents)for p-nitrophenol (PNP), used as a hydrophobic pollutant, in presence of cetylpyridinium chloride (CPC), a cationic surfactant. First, the effect of different parameters (pH solution, contact time, surfactant initial concentration…) on the adsorption of CPC on the alginate beads was investigated. Adsorption of the surfactant occurs due to electrostatic attractions between its cationic head groups and negative carboxylate functions of the alginate beads. At larger surfactant concentrations, adsorption is also due to the interaction between the hydrocarbon chains of CPC forming aggregated structures capable of solubilizing hydrophobic solutes. In a second step, we showed that PNP can reach up to 95% of adsorption in the beads in presence of CPC, although the pollutant is poorly adsorbed by alginate in absence of the surfactant. At highest CPC concentrations, desorption occurs as micellar solubilization is preferred over coadsorption. Our magsorbents appear to efficiently remove both cationic surfactant and hydrophobic pollutants and we hope that this fundamental research will be helpful for the future development of magnetically assisted processes in water treatment plants. 1. A.Bee, D.Talbot, S.Abramson, V

  1. Bioinspired methodology for preparing magnetic responsive chitosan beads to be integrated in a tubular bioreactor for biomedical applications.

    PubMed

    Song, Wenlong; Oliveira, Mariana B; Sher, Praveen; Gil, Sara; Nóbrega, J Miguel; Mano, João F

    2013-08-01

    Magnetic responsive chitosan beads were prepared using a methodology inspired by the rolling of water droplets over lotus leaves. Liquid precursors containing chitosan and magnetic microparticles were dispensed in the form of spherical droplets and crosslinked with genipin over synthetic superhydrophobic surfaces. Scanning electronic microscopy, histology and micro-computed tomography were employed to characterize the structure of the prepared composite beads and the inner distribution of the magnetic particles. Cellular metabolic activity tests showed that fibroblasts-like (L929 cell line) can adhere and proliferate on the prepared chitosan beads. We hypothesize that such spherical biomaterials could be integrated in a new concept of tubular bioreactor. The magnetic beads can be immobilized by an external magnetic field at specific positions and may be transported along the bioreactor by the drag of the culture medium flow. The system behavior was also studied through numerical modeling, which allowed to identify the relative importance of the main parameters, and to conclude that the distance between carrier beads plays a major role on their interaction with the culture medium and, consequently, on the overall system performance. In an up-scaled version of this bioreactor, the herein presented system may comprise different chambers in serial or parallel configurations. This constitutes a simple way of preparing magnetic responsive beads combined with a new design of bioreactor, which may find application in biomedicine and biotechnology, including in cell expansion for tissue engineering or for the production of therapeutic proteins to be used in cell therapies. PMID:23770831

  2. Reconfigurable and resettable arithmetic logic units based on magnetic beads and DNA

    NASA Astrophysics Data System (ADS)

    Zhang, Siqi; Wang, Kun; Huang, Congcong; Sun, Ting

    2015-12-01

    Based on the characteristics of magnetic beads and DNA, a simple and universal platform was developed for the integration of multiple logic gates to achieve resettable half adder and half subtractor functions. The signal reporter was composed of a split G-quadruplex DNAzyme and AuNP-surface immobilized molecular beacon molecule. The novel feature of the designed system is that the inputs (split G-quadruplexes) can interact with hairpin-modified Au NPs linked to magnetic particles. Another novel feature is that the logic operations can be reset by heating the output system and by using the magnetic separation of the computing modules. Moreover, the developed half adder and half subtractor are realized on a simple DNA/magnetic bead platform in an enzyme-free system and share a constant threshold setpoint. Due to the diversity and design flexibility of DNA, these investigations may provide a new method for the development of resettable DNA-based arithmetic operations.Based on the characteristics of magnetic beads and DNA, a simple and universal platform was developed for the integration of multiple logic gates to achieve resettable half adder and half subtractor functions. The signal reporter was composed of a split G-quadruplex DNAzyme and AuNP-surface immobilized molecular beacon molecule. The novel feature of the designed system is that the inputs (split G-quadruplexes) can interact with hairpin-modified Au NPs linked to magnetic particles. Another novel feature is that the logic operations can be reset by heating the output system and by using the magnetic separation of the computing modules. Moreover, the developed half adder and half subtractor are realized on a simple DNA/magnetic bead platform in an enzyme-free system and share a constant threshold setpoint. Due to the diversity and design flexibility of DNA, these investigations may provide a new method for the development of resettable DNA-based arithmetic operations. Electronic supplementary information

  3. Resistive pulse sensing of magnetic beads and supraparticle structures using tunable pores

    PubMed Central

    Willmott, Geoff R.; Platt, Mark; Lee, Gil U.

    2012-01-01

    Tunable pores (TPs) have been used for resistive pulse sensing of 1 μm superparamagnetic beads, both dispersed and within a magnetic field. Upon application of this field, magnetic supraparticle structures (SPSs) were observed. Onset of aggregation was most effectively indicated by an increase in the mean event magnitude, with data collected using an automated thresholding method. Simulations enabled discrimination between resistive pulses caused by dimers and individual particles. Distinct but time-correlated peaks were often observed, suggesting that SPSs became separated in pressure-driven flow focused at the pore constriction. The distinct properties of magnetophoretic and pressure-driven transport mechanisms can explain variations in the event rate when particles move through an asymmetric pore in either direction, with or without a magnetic field applied. Use of TPs for resistive pulse sensing holds potential for efficient, versatile analysis and measurement of nano- and microparticles, while magnetic beads and particle aggregation play important roles in many prospective biosensing applications. PMID:22662090

  4. Detection of a magnetic bead by hybrid nanodevices using scanning gate microscopy

    NASA Astrophysics Data System (ADS)

    Corte-León, H.; Krzysteczko, P.; Marchi, F.; Motte, J.-F.; Manzin, A.; Schumacher, H. W.; Antonov, V.; Kazakova, O.

    2016-05-01

    Hybrid ferromagnetic(Py)/non-magnetic metal(Au) junctions with a width of 400 nm are studied by magnetotransport measurements, magnetic scanning gate microscopy (SGM) with a magnetic bead (MB) attached to the probe, and micromagnetic simulations. In the transverse geometry, the devices demonstrate a characteristic magnetoresistive behavior that depends on the direction of the in plane magnetic field, with minimum/maximum variation when the field is applied parallel/perpendicular to the Py wire. The SGM is performed with a NdFeB bead of 1.6 μm diameter attached to the scanning probe. Our results demonstrate that the hybrid junction can be used to detect this type of MB. A rough approximation of the sensing volume of the junction has the shape of elliptical cylinder with the volume of ˜1.51 μm3. Micromagnetic simulations coupled to a magnetotransport model including anisotropic magnetoresistance and planar Hall effects are in good agreement with the experimental findings, enabling the interpretation of the SGM images.

  5. Magnetic beads-based electrochemical immunosensor for monitoring allergenic food proteins.

    PubMed

    Čadková, Michaela; Metelka, Radovan; Holubová, Lucie; Horák, Daniel; Dvořáková, Veronika; Bílková, Zuzana; Korecká, Lucie

    2015-09-01

    Screen-printed platinum electrodes as transducer and magnetic beads as solid phase were combined to develop a particle-based electrochemical immunosensor for monitoring the serious food allergen ovalbumin. The standard arrangement of enzyme-linked immunosorbent assay became the basis for designing the immunosensor. A sandwich-type immunocomplex was formed between magnetic particles functionalized with specific anti-ovalbumin immunoglobulin G and captured ovalbumin molecules, and secondary anti-ovalbumin antibodies conjugated with the enzyme horseradish peroxidase were subsequently added as label tag. The electrochemical signal proportional to the enzymatic reaction of horseradish peroxidase during the reduction of hydrogen peroxide with thionine as electron mediator was measured by linear sweep voltammetry. The newly established method of ovalbumin detection exhibits high sensitivity suitable for quantification in the range of 11 to 222nM and a detection limit of 5nM. Magnetic beads-based assay format using external magnets for rapid and simple separation has been proven to be an excellent basis for electrochemical detection and quantification of food allergens in highly complex sample matrices. PMID:25963896

  6. Paramagnetic Beads and Magnetically Mediated Strain Enhance Cardiomyogenesis in Mouse Embryoid Bodies

    PubMed Central

    Geuss, Laura R.; Wu, Douglas C.; Ramamoorthy, Divya; Alford, Corinne D.; Suggs, Laura J.

    2014-01-01

    Mechanical forces play an important role in proper embryologic development, and similarly such forces can directly impact pluripotency and differentiation of mouse embryonic stem cells (mESC) in vitro. In addition, manipulation of the embryoid body (EB) microenvironment, such as by incorporation of microspheres or microparticles, can similarly influence fate determination. In this study, we developed a mechanical stimulation regimen using permanent neodymium magnets to magnetically attract cells within an EB. Arginine-Glycine-Aspartic Acid (RGD)-conjugated paramagnetic beads were incorporated into the interior of the EBs during aggregation, allowing us to exert force on individual cells using short-term magnetization. EBs were stimulated for one hour at different magnetic field strengths, subsequently exerting a range of force intensity on the cells at different stages of early EB development. Our results demonstrated that following exposure to a 0.2 Tesla magnetic field, ESCs respond to magnetically mediated strain by activating Protein Kinase A (PKA) and increasing phosphorylated extracellular signal-regulated kinase 1/2 (pERK1/2) expression. The timing of stimulation can also be tailored to guide ESC differentiation: the combination of bone morphogenetic protein 4 (BMP4) supplementation with one hour of magnetic attraction on Day 3 enhances cardiomyogenesis by increasing contractile activity and the percentage of sarcomeric α-actin-expressing cells compared to control samples with BMP4 alone. Interestingly, we also observed that the beads alone had some impact on differentiation by increasingly slightly, albeit not significantly, the percentage of cardiomyocytes. Together these results suggest that magnetically mediated strain can be used to enhance the percentage of mouse ESC-derived cardiomyocytes over current differentiation protocols. PMID:25501004

  7. Microarrays--status and prospects.

    PubMed

    Venkatasubbarao, Srivatsa

    2004-12-01

    Microarrays have become an extremely important research tool for life science researchers and are also beginning to be used in diagnostic, treatment and monitoring applications. This article provides a detailed description of microarrays prepared by in situ synthesis, deposition using microspotting methods, nonplanar bead arrays, flow-through microarrays, optical fiber bundle arrays and nanobarcodes. The problems and challenges in the development of microarrays, development of standards and diagnostic microarrays are described. Tables summarizing the vendor list of various derivatized microarray surfaces, commercially sold premade microarrays, bead arrays and unique microarray products in development are also included. PMID:15542153

  8. Evidence of protein-free homology recognition in magnetic bead force–extension experiments

    PubMed Central

    (O’) Lee, D. J.; Danilowicz, C.; Rochester, C.; Prentiss, M.

    2016-01-01

    Earlier theoretical studies have proposed that the homology-dependent pairing of large tracts of dsDNA may be due to physical interactions between homologous regions. Such interactions could contribute to the sequence-dependent pairing of chromosome regions that may occur in the presence or the absence of double-strand breaks. Several experiments have indicated the recognition of homologous sequences in pure electrolytic solutions without proteins. Here, we report single-molecule force experiments with a designed 60 kb long dsDNA construct; one end attached to a solid surface and the other end to a magnetic bead. The 60 kb constructs contain two 10 kb long homologous tracts oriented head to head, so that their sequences match if the two tracts fold on each other. The distance between the bead and the surface is measured as a function of the force applied to the bead. At low forces, the construct molecules extend substantially less than normal, control dsDNA, indicating the existence of preferential interaction between the homologous regions. The force increase causes no abrupt but continuous unfolding of the paired homologous regions. Simple semi-phenomenological models of the unfolding mechanics are proposed, and their predictions are compared with the data. PMID:27493568

  9. Simultaneous detection of Escherichia coli O157:H7 and Salmonella Typhimurium: The use of magnetic beads conjugated with multiple capture antibodies

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Streptavidin-coated magnetic beads were conjugated with biotinylated capture antibodies to both Escherichia coli O157:H7 and Samonella Typhimurium to form multi-pathogen capture immunomagnetic beads (IMB-M). The efficacy of these beads was investigated and compared to the use of a mixture of IMB ag...

  10. Gold nanolabels for new enhanced chemiluminescence immunoassay of alpha-fetoprotein based on magnetic beads.

    PubMed

    Bi, Sai; Yan, Yameng; Yang, Xiaoyan; Zhang, Shusheng

    2009-01-01

    Gold'n'beads: A chemiluminescence immunoassay for the sensitive and rapid determination of AFP has been developed, employing bromophenol blue as a novel chemiluminescence enhancer by taking advantages of easy separation by magnetic beads and signal amplification by gold nanoparticles based on a sandwich-type immunoreaction (see scheme).A novel and sensitive chemiluminescence immunoassay (CLIA) has been developed by employing a new chemiluminescence (CL) enhancer, bromophenol blue (BPB), for the determination of alpha-fetoprotein (AFP) based on magnetic beads (MBs) and colloidal gold nanoparticles (AuNPs) modified with HRP-labeled anti-AFP antibodies. BPB, as a chemical indicator, was found to act as a novel and highly signal enhancer of the peroxidase-catalyzed CL reaction of luminol with hydrogen peroxide. After optimizing the CL reaction conditions, this new luminol-H(2)O(2)-HRP-BPB CL system was applied to a sandwich-type CLIA based on the magnetic separation and the amplification feature of AuNPs as HRP labels. A linear range was obtained when the concentrations of AFP were from 0.1 to 5.0 ng mL(-1) (R=0.9997) with the detection limit of 0.01 ng mL(-1) (3sigma), which is one order of magnitude lower than that obtained without using AuNPs, and much lower than that typically achieved by ELISA. The present method was successfully applied to the determination of AFP in human serum samples. The results indicated that this proposed protocol could be quite promising for the application in immunoassays. PMID:19291715

  11. Binding kinetics of magnetic nanoparticles on latex beads and yeast cells studied by magnetorelaxometry

    NASA Astrophysics Data System (ADS)

    Eberbeck, Dietmar; Bergemann, Christian; Hartwig, Stefan; Steinhoff, Uwe; Trahms, Lutz

    2005-03-01

    The ion exchange mediated binding of magnetic nanoparticles (MNP) to modified latex spheres and yeast cells was quantified using magnetorelaxometry. By fitting subsequently recorded relaxation curves, the kinetics of the binding reactions was extracted. The signal of MNP with weak ion exchanger groups bound to latex and yeast cells scales linearly with the concentration of latex beads or yeast cells whereas that of MNP with strong ion exchanger groups is proportional to the square root of concentration. The binding of the latter leads to a much stronger aggregation of yeast cells than the former MNP.

  12. Discrimination of clostridium species using a magnetic bead based hybridization assay

    NASA Astrophysics Data System (ADS)

    Pahlow, Susanne; Seise, Barbara; Pollok, Sibyll; Seyboldt, Christian; Weber, Karina; Popp, Jürgen

    2014-05-01

    Clostridium chauvoei is the causative agent of blackleg, which is an endogenous bacterial infection. Mainly cattle and other ruminants are affected. The symptoms of blackleg are very similar to those of malignant edema, an infection caused by Clostridium septicum. [1, 2] Therefore a reliable differentiation of Clostridium chauvoei from other Clostridium species is required. Traditional microbiological detection methods are time consuming and laborious. Additionally, the unique identification is hindered by the overgrowing tendency of swarming Clostridium septicum colonies when both species are present. [1, 3, 4] Thus, there is a crucial need to improve and simplify the specific detection of Clostridium chauvoei and Clostridium septicum. Here we present an easy and fast Clostridium species discrimination method combining magnetic beads and fluorescence spectroscopy. Functionalized magnetic particles exhibit plentiful advantages, like their simple manipulation in combination with a large binding capacity of biomolecules. A specific region of the pathogenic DNA is amplified and labelled with biotin by polymerase chain reaction (PCR). These PCR products were then immobilized on magnetic beads exploiting the strong biotin-streptavidin interaction. The specific detection of different Clostridium species is achieved by using fluorescence dye labeled probe DNA for the hybridization with the immobilized PCR products. Finally, the samples were investigated by fluorescence spectroscopy. [5

  13. Electrochemical magnetic beads-based immunosensing platform for the determination of α-lactalbumin in milk.

    PubMed

    Ruiz-Valdepeñas Montiel, Víctor; Campuzano, Susana; Torrente-Rodríguez, Rebeca M; Reviejo, A Julio; Pingarrón, José M

    2016-12-15

    Alpha-lactalbumin (α-LA) is one of the whey proteins in cows' milk that has been identified as allergenic. In this work, we present, for the first time, a very sensitive magnetic beads (MBs)-based immunosensor for the determination of α-LA. A sandwich configuration involving selective capture and horseradish peroxidase-labeled detector antibodies was implemented on carboxylic acid-modified magnetic beads, captured magnetically under the surface of a disposable screen-printed carbon electrode for amperometric detection using the hydroquinone (HQ)/H2O2 system. The α-LA immunosensor exhibited a wide linear range (37.0-5000pg/ml), a low limit of detection (LOD, 11.0pg/ml) and noteworthy selectivity against other non-target proteins. The MBs-based immunosensing platform was applied successfully for the determination of α-LA in several varieties of milk (raw and UHT cows' milk as well as human milk) and infant formulations. The results were corroborated with those obtained using a commercial ELISA method, thereby substantiating the analytical merits of this unique method. PMID:27451223

  14. A Criterion for the Complete Deposition of Magnetic Beads on the Walls of Microchannels

    PubMed Central

    Pallares, Jordi

    2016-01-01

    This paper analyzes numerical simulations of the trajectories of magnetic beads in a microchannel, with a nearby permanent cubical magnet, under different flow and magnetic conditions. Analytically derived local fluid velocities and local magnetic forces have been used to track the particles. A centered position and a lateral position of the magnet above the microchannel are considered. The computed fractions of deposited particles on the walls are compared successfully with a new theoretically derived criterion that imposes a relation between the sizes of the magnet and the microchannel and the particle Stokes and Alfvén numbers to obtain the complete deposition of the flowing particles on the wall. In the cases in which all the particles, initially distributed uniformly across the section of the microchannel, are deposited on the walls, the simulations predict the accumulation of the major part of particles on the wall closest to the magnet and near the first half of the streamwise length of the magnet. PMID:27007336

  15. Fibrous polymer grafted magnetic chitosan beads with strong poly(cation-exchange) groups for single step purification of lysozyme.

    PubMed

    Bayramoglu, Gulay; Tekinay, Turgay; Ozalp, V Cengiz; Arica, M Yakup

    2015-05-15

    Lysozyme is an important polypetide used in medical and food applications. We report a novel magnetic strong cation exchange beads for efficient purification of lysozyme from chicken egg white. Magnetic chitosan (MCHT) beads were synthesized via phase inversion method, and then grafted with poly(glycidyl methacrylate) (p(GMA)) via the surface-initiated atom transfer radical polymerization (SI-ATRP). Epoxy groups of the grafted polymer, were modified into strong cation-exchange groups (i.e., sulfonate groups) in the presence of sodium sulfite. The MCTH and MCTH-g-p(GMA)-SO3H beads were characterized by ATR-FTIR, SEM, and VSM. The sulphonate groups content of the modified MCTH-g-p(GMA)-4 beads was found to be 0.53mmolg(-1) of beads by the potentiometric titration method. The MCTH-g-p(GMA)-SO3H beads were first used as an ion-exchange support for adsorption of lysozyme from aqueous solution. The influence of different experimental parameters such as pH, contact time, and temperature on the adsorption process was evaluated. The maximum adsorption capacity was found to be 208.7mgg(-1) beads. Adsorption of lysozyme on the MCTH-g-p(GMA)-SO3H beads fitted to Langmuir isotherm model and followed the pseudo second-order kinetic. More than 93% of the adsorbed lysozyme was desorbed using Na2CO3 solution (pH 11.0). The purity of the lysozyme was checked by HPLC and SDS gel electrophoresis. In addition, the MCTH-g-p(GMA)-SO3H beads prepared in this work showed promising potential for separation of various anionic molecules. PMID:25864009

  16. Immobilization of Brassica oleracea chlorophyllase 1 (BoCLH1) and Candida rugosa lipase (CRL) in magnetic alginate beads: an enzymatic evaluation in the corresponding proteins.

    PubMed

    Yang, Chih-Hui; Yen, Chih-Chung; Jheng, Jen-Jyun; Wang, Chih-Yu; Chen, Sheau-Shyang; Huang, Pei-Yu; Huang, Keng-Shiang; Shaw, Jei-Fu

    2014-01-01

    Enzymes have a wide variety of applications in diverse biotechnological fields, and the immobilization of enzymes plays a key role in academic research or industrialization due to the stabilization and recyclability it confers. In this study, we immobilized the Brassica oleracea chlorophyllase 1 (BoCLH1) or Candida rugosa lipase (CRL) in magnetic iron oxide nanoparticles-loaded alginate composite beads. The catalytic activity and specific activity of the BoCLH1 and CRL entrapped in magnetic alginate composite beads were evaluated. Results show that the activity of immobilized BoCLH1 in magnetic alginate composite beads (3.36±0.469 U/g gel) was higher than that of immobilized BoCLH1 in alginate beads (2.96±0.264 U/g gel). In addition, the specific activity of BoCLH1 beads (10.90±1.521 U/mg protein) was higher than that immobilized BoCLH1 in alginate beads (8.52±0.758 U/mg protein). In contrast, the immobilized CRL in magnetic alginate composite beads exhibited a lower enzyme activity (11.81±0.618) than CRL immobilized in alginate beads (94.83±7.929), and the specific activity of immobilized CRL entrapped in magnetic alginate composite beads (1.99±0.104) was lower than immobilized lipase in alginate beads (15.01±1.255). A study of the degradation of magnetic alginate composite beads immersed in acidic solution (pH 3) shows that the magnetic alginate composite beads remain intact in acidic solution for at least 6 h, indicating the maintenance of the enzyme catalytic effect in low-pH environment. Finally, the enzyme immobilized magnetic alginate composite beads could be collected by an external magnet and reused for at least six cycles. PMID:25105918

  17. Magnetic hydrogel beads based on PVA/sodium alginate/laponite RD and studying their BSA adsorption.

    PubMed

    Mahdavinia, Gholam Reza; Mousanezhad, Sedigheh; Hosseinzadeh, Hamed; Darvishi, Farshad; Sabzi, Mohammad

    2016-08-20

    In this study double physically crosslinked magnetic hydrogel beads were developed by a simple method including solution mixing of sodium alginate and poly(vinyl alcohol) (PVA) containing magnetic laponite RD (Rapid Dispersion). Sodium alginate and PVA were physically crosslinked by Ca(2+) and freezing-thawing cycles, respectively. Magnetic laponite RD nanoparticles were incorporated into the system to create magnetic response and strengthen the hydrogels. All hybrids double physically crosslinked hydrogel beads were stable under different pH values without any disintegration. Furthermore, adsorption of bovine serum albumin (BSA) on the hydrogel beads was investigated on the subject of pH, ion strength, initial BSA concentration, and temperature. Nanocomposite beads exhibited maximum adsorption capacity for BSA at pH=4.5. The experimental adsorption isotherm data were well followed Langmuir model and based on this model the maximum adsorption capacity was obtained 127.3mgg(-1) at 308K. Thermodynamic parameters revealed spontaneous and monolayer adsorption of BSA on magnetic nanocomposites beads. PMID:27178944

  18. Identification of serum biomarkers for lung cancer using magnetic bead-based SELDI-TOF-MS

    PubMed Central

    Song, Qi-bin; Hu, Wei-guo; Wang, Peng; Yao, Yi; Zeng, Hua-zong

    2011-01-01

    Aim: To identify novel serum biomarkers for lung cancer diagnosis using magnetic bead-based surface-enhanced laser desorption/ionization time-of-flight mass spectrum (SELDI-TOF-MS). Methods: The protein fractions of 121 serum specimens from 30 lung cancer patients, 30 pulmonary tuberculosis patients and 33 healthy controls were enriched using WCX magnetic beads and subjected to SELDI-TOF-MS. The spectra were analyzed using Bio-marker Wizard version 3.1.0 and Biomarker Patterns Software version 5.0. A diagnostic model was constructed with the marker proteins using a linear discrimination analysis method. The validity of this model was tested in a blind test set consisted of 8 randomly selected lung cancer patients, 10 pulmonary tuberculosis patients and 10 healthy volunteers. Results: Seventeen m/z peaks were identified, which were significantly different between the lung cancer group and the control (tuberculosis and healthy control) groups. Among these peaks, the 6445, 9725, 11705, and 15126 m/z peaks were selected by the Biomarker Pattern Software to construct a diagnostic model for lung cancer. This four-peak model established in the training set could discriminate lung cancer patients from non-cancer patients with a sensitivity of 93.3% (28/30) and a specificity of 90.5% (57/63). The diagnostic model showed a high sensitivity (75.0%) and a high specificity (95%) in the blind test validation. Database searching and literature mining indicated that the featured 4 peaks represented chaperonin (M9725), hemoglobin subunit beta (M15335), serum amyloid A (M11548), and an unknown protein. Conclusion: A lung cancer diagnostic model based on bead-based SELDI-TOF-MS has been established for the early diagnosis or differential diagnosis of lung cancers. PMID:22019958

  19. Degradation of synthetic pollutants in real wastewater using laccase encapsulated in core-shell magnetic copper alginate beads.

    PubMed

    Le, Thao Thanh; Murugesan, Kumarasamy; Lee, Chung-Seop; Vu, Chi Huong; Chang, Yoon-Seok; Jeon, Jong-Rok

    2016-09-01

    Immobilization of laccase has been highlighted to enhance their stability and reusability in bioremediation. In this study, we provide a novel immobilization technique that is very suitable to real wastewater treatment. A perfect core-shell system composing copper alginate for the immobilization of laccase (Lac-beads) was produced. Additionally, nFe2O3 was incorporated for the bead recycling through magnetic force. The beads were proven to immobilize 85.5% of total laccase treated and also to be structurally stable in water, acetate buffer, and real wastewater. To test the Lac-beads reactivity, triclosan (TCS) and Remazol Brilliant Blue R (RBBR) were employed. The Lac-beads showed a high percentage of TCS removal (89.6%) after 8h and RBBR decolonization at a range from 54.2% to 75.8% after 4h. Remarkably, the pollutants removal efficacy of the Lac-beads was significantly maintained in real wastewater with the bead recyclability, whereas that of the corresponding free laccase was severely deteriorated. PMID:27240236

  20. Multiscale evaluation of cellular adhesion alteration and cytoskeleton remodeling by magnetic bead twisting.

    PubMed

    Isabey, Daniel; Pelle, Gabriel; André Dias, Sofia; Bottier, Mathieu; Nguyen, Ngoc-Minh; Filoche, Marcel; Louis, Bruno

    2016-08-01

    Cellular adhesion forces depend on local biological conditions meaning that adhesion characterization must be performed while preserving cellular integrity. We presently postulate that magnetic bead twisting provides an appropriate stress, i.e., basically a clamp, for assessment in living cells of both cellular adhesion and mechanical properties of the cytoskeleton. A global dissociation rate obeying a Bell-type model was used to determine the natural dissociation rate ([Formula: see text]) and a reference stress ([Formula: see text]). These adhesion parameters were determined in parallel to the mechanical properties for a variety of biological conditions in which either adhesion or cytoskeleton was selectively weakened or strengthened by changing successively ligand concentration, actin polymerization level (by treating with cytochalasin D), level of exerted stress (by increasing magnetic torque), and cell environment (by using rigid and soft 3D matrices). On the whole, this multiscale evaluation of the cellular and molecular responses to a controlled stress reveals an evolution which is consistent with stochastic multiple bond theories and with literature results obtained with other molecular techniques. Present results confirm the validity of the proposed bead-twisting approach for its capability to probe cellular and molecular responses in a variety of biological conditions. PMID:26459324

  1. Monitoring the growth of individual bacteria using asynchronous magnetic bead rotation sensors

    PubMed Central

    Kinnunen, Paivo; Sinn, Irene; McNaughton, Brandon H.; Newton, Duane W.; Burns, Mark A.; Kopelman, Raoul

    2010-01-01

    Continuous growth of individual bacteria has been previously studied by direct observation using optical imaging. However, optical microscopy studies are inherently diffraction limited and limited in the number of individual cells that can be continuously monitored. Here we report on the use of the asynchronous magnetic bead rotation (AMBR) sensor, which is not diffraction limited. The AMBR sensor allows for the measurement of nanoscale growth dynamics of individual bacterial cells, over multiple generations. This torque-based magnetic bead sensor monitors variations in drag caused by the attachment and growth of a single bacterial cell. In this manner, we observed the growth and division of individual E. coli bacteria, with 80 nanometer sensitivity to the cell length. Over the life cycle of a cell we observed up to 300 % increase in the rotational period of the biosensor due to increased cell volume. In addition, we observed single bacterial cell growth response to antibiotics. This work demonstrates a non-microscopy based approach for monitoring individual cell growth dynamics, including cell elongation, generation time, lag time, and division, as well as their sensitivity to antibiotics. PMID:21095112

  2. Lateral flow biosensor for multiplex detection of nitrofuran metabolites based on functionalized magnetic beads.

    PubMed

    Lu, Xuewen; Liang, Xiaoling; Dong, Jianghong; Fang, Zhiyuan; Zeng, Lingwen

    2016-09-01

    The use of potential mutagenic nitrofuran antibiotic in food animal production has been banned world-wide. Common methods for nitrofuran detection involve complex extraction procedures. In the present study, magnetic beads functionalized with antibody against nitrofuran derivative were used as both the extraction and color developing media in lateral flow biosensor. Derivatization reagent carboxybenzaldehyde is firstly modified with ractopamine. After reaction with nitrofuran metabolites, the resultant molecule has two functional groups: the metabolite moiety and the ractopamine moiety. Metabolite moiety is captured by the antibody that is coated on magnetic beads. This duplex is then loaded onto biosensor and ractopamine moiety is further captured by the antibody immobilized on the test zone of nitrocellulose membrane. Without tedious organic reagent-based extraction procedure, this biosensor was capable of visually detecting four metabolites simultaneously with a detection limit of 0.1 μg/L. No cross-reactivity was observed in the presence of 50 μg/L interferential components. Graphical abstract Derivatization of nitrofuran metabolites (AHD, AOZ, SEM, or AMOZ) and LFA detection of the derivative products. PMID:27438720

  3. Improvement of extraction capability of magnetic molecularly imprinted polymer beads in aqueous media via dual-phase solvent system.

    PubMed

    Hu, Yuling; Liu, Ruijin; Zhang, Yi; Li, Gongke

    2009-08-15

    In this study, a novel and simple dual-phase solvent system for the improvement of extraction capability of magnetic molecularly imprinted polymer (MIP) beads in aqueous sample was proposed. The method integrated MIP extraction and micro-liquid-liquid extraction (micro-LLE) into only one step. A magnetic MIP beads using atrazine as template was synthesized, and was applied to aqueous media by adding micro-volume of n-hexane to form a co-extraction system. The magnetic MIP beads preferred to suspend in the organic phase, which shielded them from the disturbance of water molecule. The target analytes in the water sample was extracted into the organic phase by micro-LLE and then further bound to the solid-phase of magnetic MIP beads. The beads specificity was significantly improved with the imprinting efficiency of template increasing from 0.5 to 4.4, as compared with that in pure aqueous media. The extraction capacity, equilibration process and cross-selectivity of the MIP dual-phase solvent extraction system were investigated. The proposed method coupled with high-performance liquid chromatography was applied to the analysis of atrazine, simazine, propazine, simetryn, prometryne, ametryn and terbutryn in complicated sample such as tomato, strawberry juice and milk. The method is selective, sensitive and low organic solvent-consuming, and has potential to broaden the range of MIP application in biological and environmental sample. PMID:19576415

  4. Trapping and dynamic manipulation of polystyrene beads mimicking circulating tumor cells using targeted magnetic/photoacoustic contrast agents

    NASA Astrophysics Data System (ADS)

    Wei, Chen-Wei; Xia, Jinjun; Pelivanov, Ivan; Hu, Xiaoge; Gao, Xiaohu; O'Donnell, Matthew

    2012-10-01

    Results on magnetically trapping and manipulating micro-scale beads circulating in a flow field mimicking metastatic cancer cells in human peripheral vessels are presented. Composite contrast agents combining magneto-sensitive nanospheres and highly optical absorptive gold nanorods were conjugated to micro-scale polystyrene beads. To efficiently trap the targeted objects in a fast stream, a dual magnet system consisting of two flat magnets to magnetize (polarize) the contrast agent and an array of cone magnets producing a sharp gradient field to trap the magnetized contrast agent was designed and constructed. A water-ink solution with an optical absorption coefficient of 10 cm-1 was used to mimic the optical absorption of blood. Magnetomotive photoacoustic imaging helped visualize bead trapping, dynamic manipulation of trapped beads in a flow field, and the subtraction of stationary background signals insensitive to the magnetic field. The results show that trafficking micro-scale objects can be effectively trapped in a stream with a flow rate up to 12 ml/min and the background can be significantly (greater than 15 dB) suppressed. It makes the proposed method very promising for sensitive detection of rare circulating tumor cells within high flow vessels with a highly absorptive optical background.

  5. MicroRNA Sensor Based on Magnetic Beads and Enzymatic Probes

    NASA Astrophysics Data System (ADS)

    Zhang, Yue; Zhou, Dejian; He, Junhui

    2014-12-01

    MicroRNAs are associated with multiple cellular processes and diseases. Here, we designed a highly sensitive, magnetically retrievable biosensor using magnetic beads (MBs) as a model RNA sensor. The assay utilized two biotinylated probes, which were hybridized to the complementary target miRNA in a sandwich assay format. One of the biotinylated ends of the hybridization complex was immobilized onto the surface of a NeutrAvidin (NAV) coated MB and the other biotinylated end was conjugated to HRP via NAV-biotin interaction. The results were presented by colorimetric absorbance of the resorufin product from amplex red oxidation. We show that by combining the use of MBs as well as bio-specific immobilization, the sensitivity of miRNA detection is down to 100 pM. This model HRP-MBs system can be used for simple, rapid colorimetric quantification of low level DNA/RNA or other small molecules.

  6. Fluorescent magnetic bead-based mast cell biosensor for electrochemical detection of allergens in foodstuffs.

    PubMed

    Jiang, Donglei; Zhu, Pei; Jiang, Hui; Ji, Jian; Sun, Xiulan; Gu, Wenshu; Zhang, Genyi

    2015-08-15

    In this study, a novel electrochemical rat basophilic leukemia cell (RBL-2H3) cell sensor, based on fluorescent magnetic beads, has been developed for the detection and evaluation of different allergens in foodstuffs. Fluorescein isothiocyanate (FITC) was successfully fused inside the SiO2 layer of SiO2 shell-coated Fe3O4 nanoparticles, which was superior to the traditional Fe3O4@SiO2@FITC modification process. The as-synthesized fluorescent magnetic beads were then encapsulated with lipidosome to form cationic magnetic fluorescent nanoparticles (CMFNPs) for mast cell magnetofection. The CMFNPs were then characterized by SEM, TEM, VSM, FTIR, and XRD analyses, and transfected into RBL-2H3 cells through a highly efficient, lipid-mediated magnetofection procedure. Magnetic glassy carbon electrode (MGCE), which possesses excellent reproducibility and regeneration qualities, was then employed to adsorb the CMFNP-transfected RBL-2H3 cells activated by an allergen antigen for electrochemical assay. Results show that the exposure of model antigen-dinitrophenol-bovine serum albumin (DNP-BSA) to anti-DNP IgE-sensitized mast cells induced a robust and long-lasting electrochemical impedance signal in a dose-dependent manner. The detection limit was identified at 3.3×10(-4) ng/mL. To demonstrate the utility of this mast cell-based biosensor for detection of real allergens in foodstuffs, Anti-Pen a1 IgE and Anti-PV IgE-activated cells were employed to quantify both shrimp allergen tropomyosin (Pen a 1) and fish allergen parvalbumin (PV). Results show high detection accuracy for these targets, with a limit of 0.03 μg/mL (shrimp Pen a 1) and 0.16 ng/mL (fish PV), respectively. To this effect, we conclude the proposed method is a facile, highly sensitive, innovative electrochemical method for the evaluation of food allergens. PMID:25889258

  7. Capture and separation of biomolecules using magnetic beads in a simple microfluidic channel without an external flow device.

    PubMed

    Wang, Jingjing; Morabito, Kenneth; Erkers, Tom; Tripathi, Anubhav

    2013-11-01

    The use of microfluidic devices and magnetic beads for applications in biotechnology has been extensively explored over the past decade. Many elaborate microfluidic chips have been used in efficient systems for biological assays. However most fail to achieve the ideal point of care (POC) status, as they require larger conventional external devices in conjunction with the microchip. This paper presents a simple technique to capture and separate biomolecules using magnetic bead movement on a microchip without the use of an external flow device. This microchip consisted of two well reservoirs (W1 and W2) connected via a tapered microchannel. Beads were dragged through the microchannel between the two wells at an equivalent speed to a permanent magnet that moved alongside the microchip. More than 95% of beads were transferred from W1 to W2 within 2 min at an average velocity of 0.7 mm s(-1). Enzymatic reactions were employed to test our microchip. Specifically, three assays were performed using the streptavidin coated magnetic beads as a solid support to capture and transfer biomolecules: (1) non-specific adsorption of the substrate, 6-8-difluoro-4-methylumbelliferyl phosphate (DiFMUP), (2) capture of the enzyme, biotinylated alkaline phosphatase (AP), and (3) separation of AP from DiFMUP. Our non-specific adsorption assay indicated that the microchip was capable of transferring the beads with less than 0.002% carryover of DiFMUP. Our capture assay indicated efficient capture and transfer of AP with beads to W2 containing DiFMUP, where the transferred AP converted 100% of DiFMUP to DiFMU within 15 minutes. Our separation assay showed effective separation of AP from DiFMUP and elucidated the binding capacity of the beads for AP. The leftover unbound AP in W1 converted 100% of DiFMUP within 10 minutes and samples with less than the full bead capacity of AP (i.e. all AP was transferred) did not convert any of the DiFMUP. The immobilization of AP on the bead surface

  8. A micropreparation of mitochondria from cells using magnetic beads with immunoaffinity.

    PubMed

    Ru, Yawei; Yin, Liang; Sun, Haidan; Yin, Songyue; Pan, Qin; Wei, Hanfu; Wu, Lin; Liu, Siqi

    2012-02-01

    Mitochondrial preparation is a key technique in the study of mitochondria. Growing evidence has demonstrated that mitochondrial proteins are tissue or cell type dependent. Locating the proteins in the global presence of mitochondrial membranes is a primary consideration in adopting antibodies for affinity enrichment of mitochondria on a micro scale. Two proteins located on the outer membrane of mitochondria, cytochrome b5 type B (CYB5B) and synaptojanin-2-binding protein (SYNJ2BP), were selected as candidates based on a survey of databases and the literature. The polyclonal antibodies against the truncated CYB5B and SYNJ2BP exhibited specific recognition to mitochondria and wider sensitivity to several tested mouse tissues and cell lines, whereas the antibody 22-kDa translocase of the outer mitochondrial membrane (TOM22) nearly missed detection of mitochondria in the liver and responded minimally to mitochondria from H9C2 and L-02 cells. Through the affinity enrichment for cellular mitochondria using magnetic beads coated with anti-CYB5B or anti-SYNJ2BP, we found that the anti-CYB5B beads could enrich mitochondria more efficiently even on a scale of 10,000 cultured cells. For the integrity and protein components, the enriched mitochondria on anti-CYB5B were carefully examined and were accepted in further functional study. We propose that an anti-CYB5B immunomagnetic approach is feasible in the micropreparation of mitochondria from cultured cells. PMID:22178913

  9. Quantification of cardiovascular disease biomarkers via functionalized magnetic beads and on-demand detachable quantum dots

    NASA Astrophysics Data System (ADS)

    Park, Hoyoung; Lee, Jong-Wook; Hwang, Mintai P.; Lee, Kwan Hyi

    2013-08-01

    Cardiovascular disease (CVD) is a potent cause of mortality in both advanced and developing countries. While soluble CD40L (sCD40L) has been implicated as a correlative factor among CVD patients, methods to quantify sCD40L are not yet well-established. In this paper, we present an ability to separate and quantify sCD40L via a simple immunomagnetic assay. Composed of functionalized magnetic beads conferred with directionality and on-demand detachable quantum dots for subsequent optical analysis, our system utilizes the competitive nature of imidazole and nickel ions for histidine. In essence, we demonstrate the capacity to effectively separate and detect sCD40L within a clinically relevant range that contains the cut-off value for acute coronary disease. While sCD40L was used to conduct this study, we envision the use of our system for the separation and quantification of other biomarkers.

  10. Magnetic bead-based nucleic acid purification kit: Clinical application and performance evaluation in stool specimens.

    PubMed

    Yoon, Jihoon G; Kang, Jin Seok; Hwang, Seung Yong; Song, Jaewoo; Jeong, Seok Hoon

    2016-05-01

    Two different methods - the semi-automated magnetic bead-based kit (SK, Stool DNA/RNA Purification kit®) and the manual membrane column-based kit (QS, QIAamp® DNA Stool Mini kit) - for purifying nucleic acids from clinical stool samples were compared and evaluated. The SK kit was more user-friendly than QS due to the reduced manual processing, partial automation, and short turnaround time with half cost. Furthermore, SK produced high yields in both DNA and RNA extractions but poor purity in RNA extraction. In the assessment of rotavirus and Clostridium difficile infection, both kits had equivalent or more sensitive performance compared with the standard method. Although SK showed some interference and inhibition in nucleic acid extraction, the performance, including the repeatability, linearity, analytical sensitivity, and matrix effect, was sufficient for routine clinical use. PMID:27030641

  11. Quantification of cardiovascular disease biomarkers via functionalized magnetic beads and on-demand detachable quantum dots.

    PubMed

    Park, Hoyoung; Lee, Jong-Wook; Hwang, Mintai P; Lee, Kwan Hyi

    2013-09-21

    Cardiovascular disease (CVD) is a potent cause of mortality in both advanced and developing countries. While soluble CD40L (sCD40L) has been implicated as a correlative factor among CVD patients, methods to quantify sCD40L are not yet well-established. In this paper, we present an ability to separate and quantify sCD40L via a simple immunomagnetic assay. Composed of functionalized magnetic beads conferred with directionality and on-demand detachable quantum dots for subsequent optical analysis, our system utilizes the competitive nature of imidazole and nickel ions for histidine. In essence, we demonstrate the capacity to effectively separate and detect sCD40L within a clinically relevant range that contains the cut-off value for acute coronary disease. While sCD40L was used to conduct this study, we envision the use of our system for the separation and quantification of other biomarkers. PMID:23893124

  12. Quantitative determination of magnetic beads using a magnetoimpedance-based lab-on-a-chip platform

    NASA Astrophysics Data System (ADS)

    Wang, Tao; Yang, Zhen; Lei, Chong; Lei, Jian; Zhou, Yong

    2014-06-01

    This research aims at establishing a lab-on-a-chip platform based on giant magnetoimpedance (GMI) effect for quantitative determination of magnetic beads (MB). A micro-integrated GMI sensor consists of Cr/Cu/NiFe/Cu/NiFe/Al2O3/Cr/Au films that were prepared by Micro-Electro-Mechanical-Systems technology. Au film was integrated into GMI sensor for potential biochemical binding function, and quantitative immobilization of MB was performed on Au film of the GMI sensor. The GMI responses were significantly enhanced at high frequencies after coating MB on the sensing elements. This research offers scientific reference for further study and exploitation on quantitative determination of biomolecules by using the micro-integrated GMI sensor.

  13. Magnetic bead purification of labeled DNA fragments forhigh-throughput capillary electrophoresis sequencing

    SciTech Connect

    Elkin, Christopher; Kapur, Hitesh; Smith, Troy; Humphries, David; Pollard, Martin; Hammon, Nancy; Hawkins, Trevor

    2001-09-15

    We have developed an automated purification method for terminator sequencing products based on a magnetic bead technology. This 384-well protocol generates labeled DNA fragments that are essentially free of contaminates for less than $0.005 per reaction. In comparison to laborious ethanol precipitation protocols, this method increases the phred20 read length by forty bases with various DNA templates such as PCR fragments, Plasmids, Cosmids and RCA products. Our method eliminates centrifugation and is compatible with both the MegaBACE 1000 and ABIPrism 3700 capillary instruments. As of September 2001, this method has produced over 1.6 million samples with 93 percent averaging 620 phred20 bases as part of Joint Genome Institutes Production Process.

  14. Rapid Detection of Ricin in Serum Based on Cu-Chelated Magnetic Beads Using Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Zhao, Yong-Qiang; Song, Jian; Wang, Hong-Li; Xu, Bin; Liu, Feng; He, Kun; Wang, Na

    2016-04-01

    The protein toxin ricin obtained from castor bean plant (Ricinus communis) seeds is a potent biological warfare agent due to its ease of availability and acute toxicity. In this study, we demonstrated a rapid and simple method to detect ricin in serum in vitro. The ricin was mixed with serum and digested by trypsin, then all the peptides were efficiently extracted using Cu-chelated magnetic beads and were detected with matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. The specific ricin peptides were identified by Nanoscale Ultra Performance liquid chromatography coupled to tandem mass spectrometry according to their sequences. The assay required 2.5 hours, and a characteristic peptide could be detected down to 4 ng/μl and used as a biomarker to detect ricin in serum. The high sensitivity and simplicity of the procedure makes it valuable in clinical practice.

  15. Rapid Detection of Ricin in Serum Based on Cu-Chelated Magnetic Beads Using Mass Spectrometry.

    PubMed

    Zhao, Yong-Qiang; Song, Jian; Wang, Hong-Li; Xu, Bin; Liu, Feng; He, Kun; Wang, Na

    2016-04-01

    The protein toxin ricin obtained from castor bean plant (Ricinus communis) seeds is a potent biological warfare agent due to its ease of availability and acute toxicity. In this study, we demonstrated a rapid and simple method to detect ricin in serum in vitro. The ricin was mixed with serum and digested by trypsin, then all the peptides were efficiently extracted using Cu-chelated magnetic beads and were detected with matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. The specific ricin peptides were identified by Nanoscale Ultra Performance liquid chromatography coupled to tandem mass spectrometry according to their sequences. The assay required 2.5 hours, and a characteristic peptide could be detected down to 4 ng/μl and used as a biomarker to detect ricin in serum. The high sensitivity and simplicity of the procedure makes it valuable in clinical practice. Graphical Abstract ᅟ. PMID:26873724

  16. The Application of Magnetic Bead Selection to Investigate Interactions between the Oral Microbiota and Salivary Immunoglobulins

    PubMed Central

    Madhwani, Tejal

    2016-01-01

    The effect of humoral immunity on the composition of the oral microbiota is less intensively investigated than hygiene and diet, in part due to a lack of simple and robust systems for investigating interactions between salivary immunoglobulins and oral bacteria. Here we report the application of an ex situ method to investigate the specificity of salivary immunoglobulins for salivary bacteria. Saliva collected from six volunteers was separated into immunoglobulin and microbial fractions, and the microbial fractions were then directly exposed to salivary immunoglobulins of “self” and “non-self” origin. Antibody-selected bacteria were separated from their congeners using a magnetic bead system, selective for IgA or IgG isotypes. The positively selected fractions were then characterized using gel-based eubacterial-specific DNA profiling. The eubacterial profiles of positively selected fractions diverged significantly from profiles of whole salivary consortia based on volunteer (P≤ 0.001%) and immunoglobulin origin (P≤ 0.001%), but not immunoglobulin isotype (P = 0.2). DNA profiles of separated microbial fractions were significantly (p≤ 0.05) less diverse than whole salivary consortia and included oral and environmental bacteria. Consortia selected using self immunoglobulins were generally less diverse than those selected with immunoglobulins of non-self origin. Magnetic bead separation facilitated the testing of interactions between salivary antibodies and oral bacteria, showing that these interactions are specific and may reflect differences in recognition by self and non-self immunoglobulins. Further development of this system could improve understanding of the relationship between the oral microbiota and the host immune system and of mechanisms underlying the compositional stability of the oral microbiota. PMID:27483159

  17. The Application of Magnetic Bead Selection to Investigate Interactions between the Oral Microbiota and Salivary Immunoglobulins.

    PubMed

    Madhwani, Tejal; McBain, Andrew J

    2016-01-01

    The effect of humoral immunity on the composition of the oral microbiota is less intensively investigated than hygiene and diet, in part due to a lack of simple and robust systems for investigating interactions between salivary immunoglobulins and oral bacteria. Here we report the application of an ex situ method to investigate the specificity of salivary immunoglobulins for salivary bacteria. Saliva collected from six volunteers was separated into immunoglobulin and microbial fractions, and the microbial fractions were then directly exposed to salivary immunoglobulins of "self" and "non-self" origin. Antibody-selected bacteria were separated from their congeners using a magnetic bead system, selective for IgA or IgG isotypes. The positively selected fractions were then characterized using gel-based eubacterial-specific DNA profiling. The eubacterial profiles of positively selected fractions diverged significantly from profiles of whole salivary consortia based on volunteer (P≤ 0.001%) and immunoglobulin origin (P≤ 0.001%), but not immunoglobulin isotype (P = 0.2). DNA profiles of separated microbial fractions were significantly (p≤ 0.05) less diverse than whole salivary consortia and included oral and environmental bacteria. Consortia selected using self immunoglobulins were generally less diverse than those selected with immunoglobulins of non-self origin. Magnetic bead separation facilitated the testing of interactions between salivary antibodies and oral bacteria, showing that these interactions are specific and may reflect differences in recognition by self and non-self immunoglobulins. Further development of this system could improve understanding of the relationship between the oral microbiota and the host immune system and of mechanisms underlying the compositional stability of the oral microbiota. PMID:27483159

  18. Magnetic/pH-responsive beads based on caboxymethyl chitosan and κ-carrageenan and controlled drug release.

    PubMed

    Mahdavinia, Gholam Reza; Etemadi, Hossein; Soleymani, Fatemeh

    2015-09-01

    This paper reports the synthesis of magnetic and pH-sensitive beads derived from κ-carrageenan and carboxymethyl chitosan for drug delivery. The magnetic Fe3O4 nanoparticles were synthesized inside a mixture of biopolymers by in situ method. The structural properties of hydrogel beads were characterized by TEM, SEM, XRD, and VSM techniques. The swelling ratio of beads indicated pH-dependent properties with maximum water absorbing at pH 7.4. Introducing magnetic nanoparticles caused a decrease in swelling capacity from 16.4 to 10 g/g. Drug loading and release efficiency were investigated using diclofenac sodium as a model system. The in vitro drug release studies exhibited significant behaviors on the subject of physiological simulated pHs and external alternative magnetic fields. The maximum cumulative release was around 82% at pH 7.4. The presence of magnetite nanoparticles certainly influenced the drug release patterns. The response of beads to external stimulus makes them as good candidates for novel drug delivery systems. PMID:26005146

  19. Investigation of the complex susceptibility of magnetic beads containing maghemite nanoparticles

    NASA Astrophysics Data System (ADS)

    Fannin, P. C.; Cohen-Tannoudji, L.; Bertrand, E.; Giannitsis, A. T.; Mac Oireachtaigh, C.; Bibette, J.

    2006-08-01

    We report on frequency and field-dependent complex susceptibility, χ(ω)=χs'(ω)-iχs″(ω), measurements of a magnetic colloidal system consisting of 200 nm spherical beads, containing maghemite ( γFe 2O 3) nanoparticles. The relaxation properties of both the magnetic colloid and a free suspension of the γFe 2O 3 particles, are investigated over the frequency range 200 Hz-1 MHz. Under a polarizing field H, an absorption peak is detected in the χs″ component at frequencies fmax between 1.1 and 1.7 kHz. We show that this absorption peak can be attributed to the Néel relaxation of the inner maghemite nanoparticles. It is also shown that the general trend for the value of fmax and the amplitude of both χs' and χs″ is to increase with increasing H. Furthermore, the relation between χs'(ω) and χs″(ω) and their dependence on frequency, ω/2 π, is investigated by means of the magnetic analogue of the Cole-Cole plot and a measure of the Cole-Cole distribution parameter αs is determined.

  20. Rapid Isolation of Staphylococcus aureus Pathogens from Infected Clinical Samples Using Magnetic Beads Coated with Fc-Mannose Binding Lectin.

    PubMed

    Bicart-See, A; Rottman, M; Cartwright, M; Seiler, B; Gamini, N; Rodas, M; Penary, M; Giordano, G; Oswald, E; Super, M; Ingber, D E

    2016-01-01

    Here we describe how Staphylococcus aureus bacteria can be rapidly isolated from clinical samples of articular fluid and synovial tissue using magnetic beads coated with the engineered chimeric human opsonin protein, Fc-mannose-binding lectin (FcMBL). The FcMBL-beads were used to capture and magnetically remove bacteria from purified cultures of 12 S. aureus strains, and from 8 articular fluid samples and 4 synovial tissue samples collected from patients with osteoarthritis or periprosthetic infections previously documented by positive S. aureus cultures. While the capture efficiency was high (85%) with purified S. aureus strains grown in vitro, direct FcMBL-bead capture from the clinical samples was initially disappointing (< 5% efficiency). Further analysis revealed that inhibition of FcMBL binding was due to coating of the bacteria by immunoglobulins and immune cells that masked FcMBL binding sites, and to the high viscosity of these complex biological samples. Importantly, capture of pathogens using the FcMBL-beads was increased to 76% efficiency by pretreating clinical specimens with hypotonic washes, hyaluronidase and a protease cocktail. Using this approach, S. aureus bacteria could be isolated from infected osteoarthritic tissues within 2 hours after sample collection. This FcMBL-enabled magnetic method for rapid capture and concentration of pathogens from clinical samples could be integrated upstream of current processes used in clinical microbiology laboratories to identify pathogens and perform antibiotic sensitivity testing when bacterial culture is not possible or before colonies can be detected. PMID:27275840

  1. Rapid Isolation of Staphylococcus aureus Pathogens from Infected Clinical Samples Using Magnetic Beads Coated with Fc-Mannose Binding Lectin

    PubMed Central

    Seiler, B.; Gamini, N.; Rodas, M.; Penary, M.; Giordano, G.; Oswald, E.; Super, M.; Ingber, D. E.

    2016-01-01

    Here we describe how Staphylococcus aureus bacteria can be rapidly isolated from clinical samples of articular fluid and synovial tissue using magnetic beads coated with the engineered chimeric human opsonin protein, Fc-mannose-binding lectin (FcMBL). The FcMBL-beads were used to capture and magnetically remove bacteria from purified cultures of 12 S. aureus strains, and from 8 articular fluid samples and 4 synovial tissue samples collected from patients with osteoarthritis or periprosthetic infections previously documented by positive S. aureus cultures. While the capture efficiency was high (85%) with purified S. aureus strains grown in vitro, direct FcMBL-bead capture from the clinical samples was initially disappointing (< 5% efficiency). Further analysis revealed that inhibition of FcMBL binding was due to coating of the bacteria by immunoglobulins and immune cells that masked FcMBL binding sites, and to the high viscosity of these complex biological samples. Importantly, capture of pathogens using the FcMBL-beads was increased to 76% efficiency by pretreating clinical specimens with hypotonic washes, hyaluronidase and a protease cocktail. Using this approach, S. aureus bacteria could be isolated from infected osteoarthritic tissues within 2 hours after sample collection. This FcMBL-enabled magnetic method for rapid capture and concentration of pathogens from clinical samples could be integrated upstream of current processes used in clinical microbiology laboratories to identify pathogens and perform antibiotic sensitivity testing when bacterial culture is not possible or before colonies can be detected. PMID:27275840

  2. Construction of hydrodynamic bead models from high-resolution X-ray crystallographic or nuclear magnetic resonance data.

    PubMed Central

    Byron, O

    1997-01-01

    Computer software such as HYDRO, based upon a comprehensive body of theoretical work, permits the hydrodynamic modeling of macromolecules in solution, which are represented to the computer interface as an assembly of spheres. The uniqueness of any satisfactory resultant model is optimized by incorporating into the modeling procedure the maximal possible number of criteria to which the bead model must conform. An algorithm (AtoB, for atoms to beads) that permits the direct construction of bead models from high resolution x-ray crystallographic or nuclear magnetic resonance data has now been formulated and tested. Models so generated then act as informed starting estimates for the subsequent iterative modeling procedure, thereby hastening the convergence to reasonable representations of solution conformation. Successful application of this algorithm to several proteins shows that predictions of hydrodynamic parameters, including those concerning solvation, can be confirmed. PMID:8994627

  3. Detection Techniques for Biomolecules using Semi-Conductor Nanocrystals and Magnetic Beads as Labels

    NASA Astrophysics Data System (ADS)

    Chatterjee, Esha

    Continued interest in the development of miniaturized and portable analytical platforms necessitates the exploration of sensitive methods for the detection of trace analytes. Nanomaterials, on account of their unique physical and chemical properties, are not only able to overcome many limitations of traditional detection reagents but also enable the exploration of many new signal transduction technologies. This dissertation presents a series of investigations of alternative detection techniques for biomolecules, involving the use of semi-conductor nanocrystals and magnetic beads as labels. Initial research focused on the development of quantum dot-encapsulating liposomes as a novel fluorescent label for immunoassays. This hybrid nanomaterial was anticipated to overcome the drawbacks presented by traditional fluorophores as well as provide significant signal amplification. Quantum dot-encapsulating liposomes were synthesized by the method of thin film hydration and characterized. The utility of these composite nanostructures for bioanalysis was demonstrated. However, the longterm instability of the liposomes hampered quantitative development. A second approach for assay development exploited the ability of gold nanoparticles to quench the optical signals obtained from quantum dots. The goal of this study was to demonstrate the feasibility of using aptamer-linked nanostructures in FRET-based quenching for the detection of proteins. Thrombin was used as the model analyte in this study. Experimental parameters for the assay were optimized. The assay simply required the mixing of the sample with the reagents and could be completed in less than an hour. The limit of detection for thrombin by this method was 5 nM. This homogeneous assay can be easily adapted for the detection of a wide variety of biochemicals. The novel technique of ferromagnetic resonance generated in magnetic bead labels was explored for signal transduction. This inductive detection technique lends

  4. Nonlinear dynamics of superparamagnetic beads in a traveling magnetic-field wave.

    PubMed

    Yellen, Benjamin B; Virgin, Lawrence N

    2009-07-01

    The nonlinear dynamic behavior of superparamagnetic beads exposed to a periodic array of micromagnets and an external rotating field is simulated as a function of the relative size of the bead with respect to the micromagnet size and the strength of the external field relative to the pole density of the substrate. For large bead sizes, it is confirmed that the motion of the beads corresponds to the dynamics of an overdamped nonlinear harmonic oscillator. For lower bead sizes, additional subharmonic locking effects are observed along with the emergence of bounded orbits. These results qualitatively support previous experimental investigations of traveling-wave magnetophoresis and provide guidelines for achieving nearly infinite separation resolution between differently sized beads. PMID:19658704

  5. Magnetic Bead-Based Colorimetric Immunoassay for Aflatoxin B1 Using Gold Nanoparticles

    PubMed Central

    Wang, Xu; Niessner, Reinhard; Knopp, Dietmar

    2014-01-01

    A competitive colorimetric immunoassay for the detection of aflatoxin B1 (AFB) has been established using biofunctionalized magnetic beads (MBs) and gold nanoparticles (GNPs). Aflatoxin B1-bovine serum albumin conjugates (AFB-BSA) modified MBs were employed as capture probe, which could specifically bind with GNP-labeled anti-AFB antibodies through immunoreaction, while such specific binding was competitively inhibited by the addition of AFB. After magnetic separation, the supernatant solution containing unbound GNPs was directly tested by UV-Vis spectroscopy. The absorption intensity was directly proportional to the AFB concentration. The influence of GNP size, incubation time and pH was investigated in detail. After optimization, the developed method could detect AFB in a linear range from 20 to 800 ng/L, with the limit of detection at 12 ng/L. The recoveries for spiked maize samples ranged from 92.8% to 122.0%. The proposed immunoassay provides a promising approach for simple, rapid, specific and cost-effective detection of toxins in the field of food safety. PMID:25405511

  6. Sensitive DNA detection and SNP discrimination using ultrabright SERS nanorattles and magnetic beads for malaria diagnostics.

    PubMed

    Ngo, Hoan T; Gandra, Naveen; Fales, Andrew M; Taylor, Steve M; Vo-Dinh, Tuan

    2016-07-15

    One of the major obstacles to implement nucleic acid-based molecular diagnostics at the point-of-care (POC) and in resource-limited settings is the lack of sensitive and practical DNA detection methods that can be seamlessly integrated into portable platforms. Herein we present a sensitive yet simple DNA detection method using a surface-enhanced Raman scattering (SERS) nanoplatform: the ultrabright SERS nanorattle. The method, referred to as the nanorattle-based method, involves sandwich hybridization of magnetic beads that are loaded with capture probes, target sequences, and ultrabright SERS nanorattles that are loaded with reporter probes. Upon hybridization, a magnet was applied to concentrate the hybridization sandwiches at a detection spot for SERS measurements. The ultrabright SERS nanorattles, composed of a core and a shell with resonance Raman reporters loaded in the gap space between the core and the shell, serve as SERS tags for signal detection. Using this method, a specific DNA sequence of the malaria parasite Plasmodium falciparum could be detected with a detection limit of approximately 100 attomoles. Single nucleotide polymorphism (SNP) discrimination of wild type malaria DNA and mutant malaria DNA, which confers resistance to artemisinin drugs, was also demonstrated. These test models demonstrate the molecular diagnostic potential of the nanorattle-based method to both detect and genotype infectious pathogens. Furthermore, the method's simplicity makes it a suitable candidate for integration into portable platforms for POC and in resource-limited settings applications. PMID:26913502

  7. Ion exchange kinetics of magnetic alginate ferrogel beads produced by external gelation.

    PubMed

    Teixeira, Vânea Ferreira Torres; Pereira, Nádia Rosa; Waldman, Walter Ruggeri; Ávila, Ana Luiza Cassiano Dias; Pérez, Victor Haber; Rodríguez, Rubén Jesus Sánchez

    2014-10-13

    This paper reports on a study of the influence of sodium alginate concentration and iron addition on the ion exchange kinetics of calcium alginate ferrogel beads produced by external gelation. The calcium absorption and sodium release of the beads were fitted to Fick's second law for unsteady state diffusion in order to obtain the effective diffusion coefficients of Na(+) and Ca(2+). The dried beads were characterized concerning their thermal stability, particle size distribution and morphology. The gelation kinetics showed that an increase in alginate concentration from 1% to 2% increased the Ca(2+) equilibrium concentration, but presented no effect on Ca(2+) effective diffusion coefficient. Alginate concentration higher than 2% promoted saturation of binding sites at the bead surfaces. The addition of iron promoted faster diffusion of Ca(2+) inside the gel beads and reduced the Ca(2+) equilibrium concentration. Also, iron particles entrapped in the alginate gel beads promoted greater absorption of water compared to pure alginate gel and lower thermal stability of the beads. The main diffusion of Ca(2+) into and Na(+) out from the bead took place during the first 60 min, during which almost 85-90% of the Ca(2+) equilibrium concentration is achieved, indicating that this period is sufficient to produce a Ca-alginate bead with high crosslinking of the polymer network. PMID:25037343

  8. Rapid extraction of genomic DNA from saliva for HLA typing on microarray based on magnetic nanobeads

    NASA Astrophysics Data System (ADS)

    Xie, Xin; Zhang, Xu; Yu, Bingbin; Gao, Huafang; Zhang, Huan; Fei, Weiyang

    2004-09-01

    A series of simplified protocols are developed for extracting genomic DNA from saliva by using the magnetic nanobeads as absorbents. In these protocols, both the enrichment of the target cells and the adsorption of DNA can be achieved simultaneously by our functionally modified magnetic beads in one step, and the DNA-nanobeads complex can be used as PCR templates. HLA typing based on an oligonucleotide array was conducted by hybridization with the PCR products. The result shows that the protocols are robust and sensitive.

  9. Comparison of three magnetic-bead-based RNA extraction methods for detection of cucumber green mottle mosaic virus by real-time RT-PCR.

    PubMed

    Zhao, Xiaoli; Zhou, Qi; Zhang, Lijie; Yan, Wenlong; Sun, Ning; Liang, Xinmiao; Deng, Congliang

    2015-07-01

    To determine the efficiency of RNA extraction methods based on magnetic beads, three different bead-based methods (one using silica-coated magnetic beads [SMNP], one using immunomagnetic beads conjugated to a specific antibody [IMB], and one using magnetic beads to nonspecifically adsorb virions [MNP]) were compared with the TRIzol method for the extraction of cucumber green mottle mosaic virus (CGMMV) RNA from cucumber leaves by real-time RT-PCR. The results indicated that the extraction efficiency of the SMNP method was 10 times higher than those of the IMB and MNP methods and 100 times higher than that of the TRIzol method. Therefore, the SMNP method could be considered for use in quarantine measures for the prevention and control of the disease caused by CGMMV. PMID:25951973

  10. Graphite-coated magnetic nanoparticle microarray for few-cells enrichment and detection.

    PubMed

    Chen, Zhuo; Hong, Guosong; Wang, Hailiang; Welsher, Kevin; Tabakman, Scott M; Sherlock, Sarah P; Robinson, Joshua T; Liang, Yongye; Dai, Hongjie

    2012-02-28

    Graphite-coated, highly magnetic FeCo core-shell nanoparticles were synthesized by a chemical vapor deposition method and solubilized in aqueous solution through a unique polymer mixture modification, which significantly improved the biocompatibility and stability of the magnetic nanoparticles (MNPs). Such functionalized MNPs were proven to be very stable in different conditions which would be significant for biological applications. Cell staining, manipulation, enrichment, and detection were developed with these MNPs. Under external magnetic manipulation, the MNP-stained cells exhibited directed motions. Moreover, MNPs were printed on substrates to modulate the magnetic field distribution on the surface. Capture and detection of sparse populations of cancer cells spiked into whole blood has been explored in a microarray fashion. Cancer cells from hundreds down to only two were able to be simply and efficiently detected from 1 mL of whole blood on the MNP microarray chips. Interestingly, the cells captured through the MNP microarray still showed viability and adhered to the MNP spots after incubation, which could be utilized for cancer cell detection, localized growth, and proliferation. PMID:22229344

  11. Facile synthesis of magnetic-/pH-responsive hydrogel beads based on Fe3O4 nanoparticles and chitosan hydrogel as MTX carriers for controlled drug release.

    PubMed

    Wu, Juan; Jiang, Wei; Tian, Renbing; Shen, Yewen; Jiang, Wei

    2016-10-01

    In the present study, methotrexate (MTX)-encapsulated magnetic-/pH-responsive hydrogel beads based on Fe3O4 nanoparticles and chitosan were successfully prepared through a one-step gelation process, which is a very facile, economic and environmentally friendly route. The developed hydrogel beads exhibited homogeneous porous structure and super-paramagnetic responsibility. MTX can be successfully encapsulated into magnetic chitosan hydrogel beads, and the drug encapsulation efficiency (%) and encapsulation content (%) were 93.8 and 6.28%, respectively. In addition, the drug release studies in vitro indicated that the MTX-encapsulated magnetic chitosan hydrogel beads had excellent pH-sensitivity, 90.6% MTX was released from the magnetic chitosan hydrogel beads within 48 h at pH 4.0. WST-1 assays in human liver hepatocellular carcinoma cells (HepG2) demonstrated that the MTX-encapsulated magnetic chitosan hydrogel beads had good cytocompatibility and high anti-tumor activity. Therefore, our results revealed that the MTX-encapsulated magnetic chitosan hydrogel beads would be a competitive candidate for controlled drug release in the area of targeted cancer therapy in the near future. PMID:27464586

  12. Enrichment and identification of glycoproteins in human saliva using lectin magnetic bead arrays.

    PubMed

    Caragata, Michael; Shah, Alok K; Schulz, Benjamin L; Hill, Michelle M; Punyadeera, Chamindie

    2016-03-15

    Aberrant glycosylation of proteins is a hallmark of tumorigenesis and could provide diagnostic value in cancer detection. Human saliva is an ideal source of glycoproteins due to the relatively high proportion of glycosylated proteins in the salivary proteome. Moreover, saliva collection is noninvasive and technically straightforward, and the sample collection and storage is relatively easy. Although differential glycosylation of proteins can be indicative of disease states, identification of differential glycosylation from clinical samples is not trivial. To facilitate salivary glycoprotein biomarker discovery, we optimized a method for differential glycoprotein enrichment from human saliva based on lectin magnetic bead arrays (saLeMBA). Selected lectins from distinct reactivity groups were used in the saLeMBA platform to enrich salivary glycoproteins from healthy volunteer saliva. The technical reproducibility of saLeMBA was analyzed with liquid chromatography-tandem mass spectrometry (LC-MS/MS) to identify the glycosylated proteins enriched by each lectin. Our saLeMBA platform enabled robust glycoprotein enrichment in a glycoprotein- and lectin-specific manner consistent with known protein-specific glycan profiles. We demonstrated that saLeMBA is a reliable method to enrich and detect glycoproteins present in human saliva. PMID:26743719

  13. Dual chronoamperometric detection of enzymatic biomarkers using magnetic beads and a low-cost flow cell.

    PubMed

    Moral-Vico, Javier; Barallat, Jaume; Abad, Llibertat; Olivé-Monllau, Rosa; Muñoz-Pascual, Francesc Xavier; Galán Ortega, Amparo; del Campo, F Javier; Baldrich, Eva

    2015-07-15

    In this work we report on the production of a low cost microfluidic device for the multiplexed electrochemical detection of magneto bioassays. As a proof of concept, the device has been used to detect myeloperoxidase (MPO), a cardiovascular biomarker. With this purpose, two bioassays have been optimized in parallel onto magnetic beads (MBs) for the simultaneous detection of MPO endogenous peroxidase activity and quantification of total MPO. Since the two bioassays produced signals of different magnitude for each concentration of MPO tested, two detection strategies have been compared, which entailed registering steady state currents (Iss) under substrate flow, and measuring the peak currents (Ip) produced in a stopped flow approach. As it will be shown, appropriate tuning of the detection and flow conditions can provide extremely sensitive detection, but also allow simultaneous detection of assays or parameters that would produce signals of different orders of magnitude when measured by a single detection strategy. In order to demonstrate the feasibility of the detection strategy reported, a dual MPO mass and activity assay has been finally applied to the study of 10 real plasma samples, allowing patient classification according to the risk of suffering a cardiovascular event. PMID:25791338

  14. Absorption control in immunohistochemistry using phospho-peptides immobilized on magnetic beads.

    PubMed

    Schoephoerster, Jordan; Frisch, Jillian; Grahek, Michael; Wu, Chun; He, Yingwei; Wang, Wei; Nguyen, Jennifer; Schwartz, David; Kalyuzhny, Alexander E

    2011-01-01

    Although phospho-specific primary antibodies used in immunohistochemistry (IHC) are expected to detect phosphorylated proteins, in some cases these antibodies may also cross-react with nonphosphorylated proteins. Therefore, it is of ultimate importance to employ a control to determine that the staining pattern is specific. One of the frequently used controls in IHC is a so-called absorption control: phospho-specific primary antibodies are first incubated with a phospho-peptide immunogen to block antibody-binding sites, and this mixture is subsequently applied to tissue sections. If the antibody blocked with cognate immunogen does not produce tissue staining, then the antibody is considered specific, but if staining is obtained, the antibody is considered nonspecific. Unfortunately, bound peptide can dissociate from the antibody allowing unblocked antibody to bind to tissue targets, producing unwanted staining. We have developed a simple absorption-control protocol allowing for the efficient neutralization of phospho-specific antibodies with phospho-peptides immobilized on magnetic beads. This technique allows for sequestration of antibody-peptide complex from the incubation solution, minimizing the risk of formation of unblocked antibodies capable of producing tissue staining. PMID:21370038

  15. Dual-recognition detection of Staphylococcus aureus using vancomycin-functionalized magnetic beads as concentration carriers.

    PubMed

    Yang, Shijia; Ouyang, Hui; Su, Xiaoxiao; Gao, Hongfei; Kong, Weijun; Wang, Mengyao; Shu, Qi; Fu, Zhifeng

    2016-04-15

    Vancomycin, which has a strong antibacterial effect to Gram-positive bacteria, was adopted as one molecular recognition agent for bacterial detection. Magnetic beads (MBs) were functionalized with this antibiotic to effectively concentrate Staphylococcus aureus (S. aureus). In addition, alkaline phosphatase (ALP)-tagged rabbit immunoglobulin G (ALP-IgG) was used as the second recognition agent to improve the specificity based on the binding between the Fc region of rabbit IgG and protein A in the cell wall of S. aureus. MBs-concentrated sandwich complex of vancomycin/S. aureus/ALP-IgG was formed with a one-step incubation protocol. Then ALP chemiluminescent reaction was triggered by injecting substrate solution to quantitate S. aureus. Based on the sandwich molecular recognition mechanism and MBs concentration, an ultrasensitive, specific and rapid method was developed for S. aureus detection. The linear range for S. aureus detection was 12-1.2 × 10(6)CFU mL(-1), with a very low detection limit of 3.3 CFU mL(-1). The whole detection process could be completed in 75 min. Other Gram-positive bacteria and Gram-negative bacteria, including Escherichia coli, Salmonella, Pseudomonas aeruginosa, Micrococcus luteus, Bacillus cereus and Bacillus subtilis, showed negligible interference to S. aureus detection. This method was successfully used to quantitate S. aureus in lake water, milk, human urine and human saliva with acceptable recoveries ranging from 70.0% to 116.7%. PMID:26606309

  16. Single functional magnetic-bead as universal biosensing platform for trace analyte detection using SERS-nanobioprobe.

    PubMed

    Xiao, R; Wang, C W; Zhu, A N; Long, F

    2016-05-15

    SERS biosensor has demonstrated remarkable potential to analyze various bio/chemical targets with ultrahigh sensitivity. However, the development of universal SERS biosensing platforms with a uniform and reproducible structure that can quantitatively detect a broad range of trace analytes remains a significant challenge. The production of SERS nanotags with abundant Raman reporters and rational structure to conjugate with detection biomolecules is another key to design SERS-nanobioprobes. Here, we introduce a facile single magnetic-bead biosensing platform, formed by combining the captured antibodies/antigens conjugated magnetic-beads and the Au@Raman-Reporters@Ag sandwich-based nanorod tags labeled nanobioprobes. The advantage of the robust sandwich-structure-based nanotags is attributed not only to the high density Raman reporters contained inside, with high EF value because of enhanced electromagnetic field density, but also to the flexibility for bioconjugation of the detection biomolecules. The 3-D structure of the functional magnetic-bead provides a perfect platform to rapidly capture and enrich biomolecules. Ultrasensitive detection of two small molecules and a protein was achieved in samples, respectively. PMID:26765530

  17. Capture of dengue viruses using antibody-integrated graphite-encapsulated magnetic beads produced using gas plasma technology.

    PubMed

    Sakudo, Akikazu; Viswan, Anchu; Chou, Han; Sasaki, Tadahiro; Ikuta, Kazuyoshi; Nagatsu, Masaaki

    2016-07-01

    Despite significant advances in medicine, global health is threatened by emerging infectious diseases caused by a number of viruses. Dengue virus (DENV) is a mosquito‑borne virus, which can be transmitted to humans via mosquito vectors. Previously, the Ministry of Health, Labour and Welfare in Japan reported the country's first domestically acquired case of dengue fever for almost 70 years. To address this issue, it is important to develop novel technologies for the sensitive detection of DENV. The present study reported on the development of plasma-functionalized, graphite-encapsulated magnetic nanoparticles (GrMNPs) conjugated with anti-DENV antibody for DENV capture. Radiofrequency wave‑excited inductively‑coupled Ar and ammonia gas plasmas were used to introduce amino groups onto the surface of the GrMNPs. The GrMNPs were then conjugated with an antibody against DENV, and the antibody‑integrated magnetic beads were assessed for their ability to capture DENV. Beads incubated in a cell culture medium of DENV‑infected mosquito cells were separated from the supernatant by applying a magnetic field and were then washed. The adsorption of DENV serotypes 1‑4 onto the beads was confirmed using reverse transcription‑polymerase chain reaction, which detected the presence of DENV genomic RNA on the GrMNPs. The methodology described in the present study, which employed the plasma-functionalization of GrMNPs to enable antibody‑integration, represents a significant improvement in the detection of DENV. PMID:27221214

  18. Capture of dengue viruses using antibody-integrated graphite-encapsulated magnetic beads produced using gas plasma technology

    PubMed Central

    SAKUDO, AKIKAZU; VISWAN, ANCHU; CHOU, HAN; SASAKI, TADAHIRO; IKUTA, KAZUYOSHI; NAGATSU, MASAAKI

    2016-01-01

    Despite significant advances in medicine, global health is threatened by emerging infectious diseases caused by a number of viruses. Dengue virus (DENV) is a mosquito-borne virus, which can be transmitted to humans via mosquito vectors. Previously, the Ministry of Health, Labour and Welfare in Japan reported the country's first domestically acquired case of dengue fever for almost 70 years. To address this issue, it is important to develop novel technologies for the sensitive detection of DENV. The present study reported on the development of plasma-functionalized, graphite-encapsulated magnetic nanoparticles (GrMNPs) conjugated with anti-DENV antibody for DENV capture. Radiofrequency wave-excited inductively-coupled Ar and ammonia gas plasmas were used to introduce amino groups onto the surface of the GrMNPs. The GrMNPs were then conjugated with an antibody against DENV, and the antibody-integrated magnetic beads were assessed for their ability to capture DENV. Beads incubated in a cell culture medium of DENV-infected mosquito cells were separated from the supernatant by applying a magnetic field and were then washed. The adsorption of DENV serotypes 1–4 onto the beads was confirmed using reverse transcription-polymerase chain reaction, which detected the presence of DENV genomic RNA on the GrMNPs. The methodology described in the present study, which employed the plasma-functionalization of GrMNPs to enable antibody-integration, represents a significant improvement in the detection of DENV. PMID:27221214

  19. A novel automated device for rapid nucleic acid extraction utilizing a zigzag motion of magnetic silica beads.

    PubMed

    Yamaguchi, Akemi; Matsuda, Kazuyuki; Uehara, Masayuki; Honda, Takayuki; Saito, Yasunori

    2016-02-01

    We report a novel automated device for nucleic acid extraction, which consists of a mechanical control system and a disposable cassette. The cassette is composed of a bottle, a capillary tube, and a chamber. After sample injection in the bottle, the sample is lysed, and nucleic acids are adsorbed on the surface of magnetic silica beads. These magnetic beads are transported and are vibrated through the washing reagents in the capillary tube under the control of the mechanical control system, and thus, the nucleic acid is purified without centrifugation. The purified nucleic acid is automatically extracted in 3 min for the polymerase chain reaction (PCR). The nucleic acid extraction is dependent on the transport speed and the vibration frequency of the magnetic beads, and optimizing these two parameters provided better PCR efficiency than the conventional manual procedure. There was no difference between the detection limits of our novel device and that of the conventional manual procedure. We have already developed the droplet-PCR machine, which can amplify and detect specific nucleic acids rapidly and automatically. Connecting the droplet-PCR machine to our novel automated extraction device enables PCR analysis within 15 min, and this system can be made available as a point-of-care testing in clinics as well as general hospitals. PMID:26772121

  20. Generation of Internal-Image Functional Aptamers of Okadaic Acid via Magnetic-Bead SELEX

    PubMed Central

    Lin, Chao; Liu, Zeng-Shan; Wang, Dong-Xu; Li, Lin; Hu, Pan; Gong, Sheng; Li, Yan-Song; Cui, Cheng; Wu, Zong-Cheng; Gao, Yang; Zhou, Yu; Ren, Hong-Lin; Lu, Shi-Ying

    2015-01-01

    Okadaic acid (OA) is produced by Dinophysis and Prorocentrum dinoflagellates and primarily accumulates in bivalves, and this toxin has harmful effects on consumers and operators. In this work, we first report the use of aptamers as novel non-toxic probes capable of binding to a monoclonal antibody against OA (OA-mAb). Aptamers that mimic the OA toxin with high affinity and selectivity were generated by the magnetic bead-assisted systematic evolution of ligands by exponential enrichment (SELEX) strategy. After 12 selection rounds, cloning, sequencing and enzyme-linked immunosorbent assay (ELISA) analysis, four candidate aptamers (O24, O31, O39, O40) were selected that showed high affinity and specificity for OA-mAb. The affinity constants of O24, O31, O39 and O40 were 8.3 × 108 M−1, 1.47 × 109 M−1, 1.23 × 109 M−1 and 1.05 × 109 M−1, respectively. Indirect competitive ELISA was employed to determine the internal-image function of the aptamers. The results reveal that O31 has a similar competitive function as free OA toxin, whereas the other three aptamers did not bear the necessary internal-image function. Based on the derivation of the curvilinear equation for OA/O31, the equation that defined the relationship between the OA toxin content and O31 was Y = 2.185X − 1.78. The IC50 of O31 was 3.39 ng·mL−1, which was close to the value predicted by the OA ELISA (IC50 = 4.4 ng·mL−1); the IC10 was 0.33 ng·mL−1. The above data provides strong evidence that internal-image functional aptamers could be applicable as novel probes in a non-toxic assay. PMID:26694424

  1. Enhanced quality factors and force sensitivity by attaching magnetic beads to cantilevers for atomic force microscopy in liquid

    NASA Astrophysics Data System (ADS)

    Hoof, Sebastian; Nand Gosvami, Nitya; Hoogenboom, Bart W.

    2012-12-01

    Dynamic-mode atomic force microscopy (AFM) in liquid remains complicated due to the strong viscous damping of the cantilever resonance. Here, we show that a high-quality resonance (Q >20) can be achieved in aqueous solution by attaching a microgram-bead at the end of the nanogram-cantilever. The resulting increase in cantilever mass causes the resonance frequency to drop significantly. However, the force sensitivity—as expressed via the minimum detectable force gradient—is hardly affected, because of the enhanced quality factor. Through the enhancement of the quality factor, the attached bead also reduces the relative importance of noise in the deflection detector. It can thus yield an improved signal-to-noise ratio when this detector noise is significant. We describe and analyze these effects for a set-up that includes magnetic actuation of the cantilevers and that can be easily implemented in any AFM system that is compatible with an inverted optical microscope.

  2. Influence of a cationic surfactant on adsorption of p-nitrophenol by a magsorbent based on magnetic alginate beads.

    PubMed

    Obeid, Layaly; El Kolli, Nadia; Talbot, Delphine; Welschbillig, Mathias; Bée, Agnès

    2015-11-01

    The paper focuses on the removal of p-nitrophenol by an adsorption process. A magnetic adsorbent was synthesized by encapsulation of magnetic functionalized nanoparticles using alginate as a green biopolymer matrix. A cationic surfactant, cetylpyridinium chloride (CPyCl), was used to confer a hydrophobic character to the magnetic beads and thus to promote their adsorption efficiency. The effect of different parameters such as initial concentrations of both PNP and CPyCl, contact time and solution pH value on the adsorption of PNP in the presence of CPyCl was investigated. It should be noted that combination of magnetic and adsorption properties in a same material is an interesting challenge which could overcome the recovery problems of pollutant-loaded adsorbent. PMID:26188728

  3. Optimization of magnetoresistive sensor current for on-chip magnetic bead detection using the sensor self-field

    NASA Astrophysics Data System (ADS)

    Henriksen, Anders Dahl; Rizzi, Giovanni; Østerberg, Frederik Westergaard; Hansen, Mikkel Fougt

    2015-04-01

    We investigate the self-heating of magnetoresistive sensors used for measurements on magnetic beads in magnetic biosensors. The signal from magnetic beads magnetized by the field due to the sensor bias current is proportional to the bias current squared. Therefore, we aim to maximize the bias current while limiting the sensor self-heating. We systematically characterize and model the Joule heating of magnetoresistive sensors with different sensor geometries and stack compositions. The sensor heating is determined using the increase of the sensor resistance as function of the bias current. The measured temperature increase is in good agreement with a finite element model and a simple analytical thermal model. The heat conductance of our system is limited by the 1 μm thick electrically insulating silicon dioxide layer between the sensor stack and the underlying silicon wafer, thus the heat conductance is proportional to the sensor area and inversely proportional to the oxide thickness. This simple heat conductance determines the relationship between bias current and sensor temperature, and we show that 25 μm wide sensor on a 1 μm oxide can sustain a bias current of 30 mA for an allowed temperature increase of 5 °C. The method and models used are generally applicable for thin film sensor systems. Further, the consequences for biosensor applications of the present sensor designs and the impact on future sensor designs are discussed.

  4. Optimization of the virus concentration method using polyethyleneimine-conjugated magnetic beads and its application to the detection of human hepatitis A, B and C viruses.

    PubMed

    Uchida, Eriko; Kogi, Mieko; Oshizawa, Tadashi; Furuta, Birei; Satoh, Koei; Iwata, Akiko; Murata, Mitsuhiro; Hikata, Mikio; Yamaguchi, Teruhide

    2007-07-01

    To enhance the sensitivity of virus detection by polymerase chain reaction (PCR) and reverse transcription PCR (RT-PCR), a novel virus concentration method using polyethyleneimine (PEI)-conjugated magnetic beads was developed in our previous study. However, several viruses could not be concentrated by this method. In this paper, the conditions of virus concentration were optimized to concentrate a wide range of viruses more efficiently. The PEI beads adsorbed viruses more efficiently than other cationic polymers, and the optimum virus concentration was obtained under weak acidic conditions. Mass spectrometric analysis revealed that several serum proteins, such as complement type 3, complement type 4 and immunoglobulin M (IgM), were co-adsorbed by the PEI beads, suggesting that the beads may adsorb viruses not only by direct adsorption, but also via immune complex formation. This hypothesis was confirmed by the result that poliovirus, which PEI beads could not adsorb directly, could be concentrated by the beads via immune complex formation. On the other hand, hepatitis A (HAV) and hepatitis C (HCV) viruses were adsorbed directly by PEI beads almost completely. Like poliovirus, hepatitis B virus (HBV) was concentrated efficiently by the addition of anti-HBV IgM. In conclusion, virus concentration using PEI beads is a useful method to concentrate a wide range of viruses and can be used to enhance the sensitivity of detection of HAV, HBV and HCV. PMID:17433454

  5. Integration of antibody by surface functionalization of graphite-encapsulated magnetic beads using ammonia gas plasma technology for capturing influenza A virus.

    PubMed

    Sakudo, Akikazu; Chou, Han; Ikuta, Kazuyoshi; Nagatsu, Masaaki

    2015-05-01

    Antibody-integrated magnetic beads have been functionalized for influenza A virus capture. First, ammonia plasma produced by a radio frequency power source was reacted with the surface of graphite-encapsulated magnetic beads to introduce amino groups. Anti-influenza A virus hemagglutinin antibody was then anchored by its surface sulfide groups to the amino groups on the beads via N-succinimidyl 3-(2-pyridyldithio) propionate. After incubation with influenza A virus, adsorption of the virus to the beads was confirmed by immunochromatography, polymerase chain reaction (PCR), enzyme-linked immunosorbent assay (ELISA), and inoculation of chicken embryonated eggs, indicating that virus infectivity is maintained and that the proposed method is useful for the enhanced detection and isolation of influenza A virus. PMID:25857943

  6. Molecular charge contact biosensing based on the interaction of biologically modified magnetic beads with an ion-sensitive field effect transistor.

    PubMed

    Miyazawa, Yuuya; Sakata, Toshiya

    2014-05-01

    In this article, we report a novel method of biomolecular recognition based on the molecular charge contact (MCC). As one of the MCC biosensing method, the interaction between DNA-coated magnetic beads and a silicon-based semiconductor, an ion-sensitive field effect transistor (ISFET) could be detected for DNA molecular recognition events using the principle of the field effect, which enables detecting ionic or molecular charges. After DNA-coated magnetic beads had been introduced and brought in contact with the gate surface by a magnet, the threshold voltage of the ISFET was shifted in the positive direction by immobilization, hybridization and extension reaction of DNA molecules on magnetic beads. This positive shift was based on the increase in negative charges of the phosphate groups in them. Then, the ISFET device could be reused a couple of dozen times continuously and cost-effectively because the oligonucleotide probes were tethered to the magnetic beads, but this was not done directly on the gate surface of the ISFET. Moreover, the MCC biosensing method enabled discrimination of a single nucleotide polymorphism. By creating an interaction of magnetic beads with the semiconductor, we can expect enhancement of the reaction efficiency in a solution and reuse of the device by separating the reaction field from the sensing substrate. PMID:24595376

  7. An Electrochemical Genosensing Assay Based on Magnetic Beads and Gold Nanoparticle-Loaded Latex Microspheres for Vibrio cholerae Detection.

    PubMed

    Low, Kim-Fatt; Rijiravanich, Patsamon; Singh, Kirnpal Kaur Banga; Surareungchai, Werasak; Yean, Chan Yean

    2015-04-01

    An ultrasensitive electrochemical genosensing assay was developed for the sequence-specific detection of Vibrio cholerae DNA using magnetic beads as the biorecognition surface and gold nanoparticle-loaded latex microspheres (latex-AuNPs) as a signal-amplified hybridization tag. This biorecognition surface was prepared by immobilizing specific biotinylated capturing probes onto the streptavidin-coupled magnetic beads. Fabricating a hybridization tag capable of amplifying the electrochemical signal involved loading multiple AuNPs onto polyelectrolyte multilayer film-coated poly(styrene-co-acrylic acid) latex microspheres as carrier particles. The detection targets, single-stranded 224-bp asymmetric PCR amplicons of the V. cholerae lolB gene, were sandwich-hybridized to magnetic bead-functionalized capturing probes and fluorescein-labeled detection probes and tagged with latex-AuNPs. The subsequent electrochemical stripping analysis of chemically dissolved AuNPs loaded onto the latex microspheres allowed for the quantification of the target amplicons. The high-loading capacity of the AuNPs on the latex microspheres for sandwich-type dual-hybridization genosensing provided eminent signal amplification. The genosensing variables were optimized, and the assay specificity was demonstrated. The clinical applicability of the assay was evaluated using spiked stool specimens. The current signal responded linearly to the different V. cholerae concentrations spiked into stool specimens with a detection limit of 2 colony-forming units (CFU)/ml. The proposed latex-AuNP-based magnetogenosensing platform is promising, exhibits an effective amplification performance, and offers new opportunities for the ultrasensitive detection of other microbial pathogens. PMID:26310076

  8. Magnetic-bead-based sub-femtomolar immunoassay using resonant Raman scattering signals of ZnS nanoparticles.

    PubMed

    Ding, Yadan; Cong, Tie; Chu, Xueying; Jia, Yan; Hong, Xia; Liu, Yichun

    2016-07-01

    Highly sensitive, specific, and selective immunoassays are of great significance for not only clinical diagnostics but also food safety, environmental monitoring, and so on. Enzyme-linked immunosorbent assays and fluorescence-based and electrochemical immunoassays are important intensively investigated immunoassay techniques. However, they might suffer from low sensitivity or false-positive results. In this work, a simple, reliable, and ultrasensitive magnetic-bead-based immunoassay was performed using biofunctionalized ZnS semiconductor nanocrystals as resonant Raman probes. The resonant Raman scattering of ZnS nanocrystals displays evenly spaced multi-phonon resonant Raman lines with narrow bandwidths and has strong resistance to environmental variation due to the nature of the electron-phonon interaction, thus rendering reliable signal readout in the immunoassays. The superparamagnetic Fe3O4 nanoparticles facilitated greatly the separation, purification, and concentration processes. It is beneficial for both reducing the labor intensity and amplifying the detection signals. The immobilization of antibodies on the surface of magnetic beads, the preparation of resonant Raman probes, and the immunological recognition between the antibody and analyte all occurred in the liquid phase, which minimized the diffusion barriers and boundary layer constraints. All these factors contributed to the ultralow detection limit of human IgG, which was determined to be about 0.5 fM (∼0.08 pg/ml). It is nearly the highest sensitivity obtained for IgG detection. This work shall facilitate the design of nanoplatforms for ultrasensitive detections of proteins, DNAs, bacteria, explosives, and so on. Graphical abstract An ultrasensitive magnetic-bead-based immunoassay was performed using multi-phonon resonant Raman lines of ZnS nanoparticles as detection signals. PMID:27173389

  9. Magnetic force-assisted self-locking metallic bead array for fabrication of diverse concave microwell geometries.

    PubMed

    Lee, Gi-Hun; Park, Ye Eun; Cho, Minhaeng; Park, Hansoo; Park, Joong Yull

    2016-09-21

    Spheroid cell culture is very useful for further understanding cellular behavior including motility and biochemical reaction since it mimics three-dimensional (3D) in vivo organ tissue. Among previously proposed various methods for spheroid production, such as hanging drop and spinner flask, microwell is a recently developed method harnessing microtechnology to produce uniform-sized spheroids. Although soft-lithography has been popular for creating microwell arrays, a 3D spherical geometry has been regarded as difficult to fabricate using conventional methods, or often requires complex fabrication processes and expensive equipment. Here, we propose a new method for fabricating concave microwells for cell spheroid production and culture. To demonstrate this method, we fabricated a 30 × 30 microwell array in 3 × 3 cm plates, utilizing metal beads, a through-hole array, and an assembly of small magnets. The spherical metal beads were used as a mold for the microwell, naturally creating the desired 3D concave microwell geometry. One of the key ideas was to place and hold each metal bead in the designated through-hole using the small magnet array. We also performed computational simulation of the magnetostatic force to design and observe the magnetic force field in detail. In addition, to provide a practical demonstration of the proposed system in cell biology, we created and cultured adipose-derived stem cell spheroids for 14 days for chondrogenic differentiation. This method allows further variations in microwell geometry that will enhance the method's applicability as a helpful tool for various studies in cell biology, cancer research, and tissue engineering. PMID:27509885

  10. An immune sandwich assay of carcinoembryonic antigen based on the joint use of upconversion phosphors and magnetic beads.

    PubMed

    Li, Yaohua; Wu, Zhengjun; Liu, Zhihong

    2015-06-21

    We herein report a sensitive and selective immunosensor for carcinoembryonic antigen (CEA) based on the joint use of upconversion phosphors (UCPs) and magnetic beads (MBs). UCPs as the signal probe were designed with a core-shell structure which provided a 40-fold enhancement of the luminescence intensity. Poly(acrylic acid) (PAA)-modified UCPs were covalently conjugated with the anti-CEA antibody (coating), and streptavidin functionalized magnetic beads were combined with another biotin-tagged anti-CEA antibody. With the assistance of a magnet, the as-formed immune sandwich in the presence of CEA can be readily separated from the assay matrix. The immunosensor showed a linear dynamic range for CEA within 0.05-20 ng mL(-1) in a buffered aqueous solution, and 0.1-20 ng mL(-1) in a human serum sample. The sensor was highly specific to CEA. Our results have suggested the potential application of the UCP-MB based immunoassay for CEA in clinical analysis. PMID:25882752

  11. A highly sensitive quartz crystal microbalance immunosensor based on magnetic bead-supported bienzymes catalyzed mass enhancement strategy.

    PubMed

    Akter, Rashida; Rhee, Choong Kyun; Rahman, Md Aminur

    2015-04-15

    A highly sensitive quartz crystal microbalance (QCM) immunosensor based on magnetic bead-supported bienzyme catalyzed mass enhanced strategy was developed for the detection of human immunoglobulin G (hIgG) protein. The high sensitive detection was achieved by increasing the deposited mass on the QCM crystal through the enhanced precipitation of 4-chloro-1-naphthol (CN) using higher amounts of horseradish peroxidase (HRP) and glucose oxidase (GOx) bienzymes attached on the magnetic beads (MB). The protein A (PA) and capture antibody (monoclonal anti-human IgG antibody produced in mouse, Ab1)-based QCM probe and the detection antibody (anti-human IgG antibody produced in goat, Ab2)-based MB/HRP/GOx bienzymatic bioconjugates were characterized using scanning electron microscope, transmission electron microscope, cyclic voltammetry, and electrochemical impedance spectroscopy techniques. Under the optimized experimental condition, the linear range and the detection limit of hIgG immunosensor were determined to be 5.0pg/mL-20.0ng/mL and 5.0±0.18pg/mL, respectively. The applicability of the present hIgG immunosensor was examined in hIgG spiked human serum samples and excellent recoveries of hIgG were obtained. PMID:25506902

  12. The application of magnetic bead hybridization for the recovery and STR amplification of degraded and inhibited forensic DNA.

    PubMed

    Wang, Jing; McCord, Bruce

    2011-06-01

    A common problem in the analysis of forensic DNA evidence is the presence of environmentally degraded and inhibited DNA. Such samples produce a variety of interpretational problems such as allele imbalance, allele dropout and sequence specific inhibition. In an attempt to develop methods to enhance the recovery of this type of evidence, magnetic bead hybridization has been applied to extract and preconcentrate DNA sequences containing short tandem repeat (STR) alleles of interest. In this work, genomic DNA was fragmented by heating, and sequences associated with STR alleles were selectively hybridized to allele-specific biotinylated probes. Each particular biotinylated probe-DNA complex was bound to streptavidin-coated magnetic beads using enabling enrichment of target DNA sequences. Experiments conducted using degraded DNA samples, as well as samples containing a large concentration of inhibitory substances, showed good specificity and recovery of missing alleles. Based on the favorable results obtained with these specific probes, this method should prove useful as a tool to improve the recovery of alleles from degraded and inhibited DNA samples. PMID:21706494

  13. Peptidomic analysis of Chinese shrimp ( Fenneropenaeus chinensis) hemolymph by magnetic bead-based MALDI-TOF MS

    NASA Astrophysics Data System (ADS)

    Wang, Baojie; Liu, Mei; Jiang, Keyong; Zhang, Guofan; Wang, Lei

    2013-03-01

    Peptides in shrimp hemolymph play an important role in the innate immune response. Analysis of hemolymph will help to detect and identify potential novel biomarkers of microbial infection. We used magnetic bead-based purification (ClinProt system) and matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF MS) to characterize shrimp hemolymph peptides. Shrimp serum and plasma were used as the source of samples for comparative analysis, and it was found that serum was more suitable for shrimp hemolymph peptidomic analysis. To screen potential specific biomarkers in serum of immune-challenged shrimps, we applied magnetic bead-based MALDI-TOF MS to serum samples from 10 immune-challenged and 10 healthy shrimps. The spectra were analyzed using FlexAnalysis 3.0 and ClinProTools 2.1 software. Thirteen peptide peaks significantly different between the two groups were selected as candidate biomarkers of lipopolysaccharide (LPS)-infection. The diagnostic model established by genetic algorithm using five of these peaks was able to discriminate LPS-challenged shrimps from healthy control shrimps with a sensitivity of 90% and a specificity of 100%. Our approach in MALDITOF MS-based peptidomics is a powerful tool for screening bioactive peptides or biomarkers derived from hemolymph, and will help to enable a better understanding of the innate immune response of shrimps.

  14. Preparation of styrene-co-4-vinylpyridine magnetic polymer beads by microwave irradiation for analysis of trace 24-epibrassinolide in plant samples using high performance liquid chromatography.

    PubMed

    Zhang, Zhuomin; Zhang, Yi; Tan, Wei; Li, Gongke; Hu, Yuling

    2010-10-15

    In the study, a kind of novel styrene-co-4-vinylpyridine (St-co-4-VP) porous magnetic polymer beads was prepared by microwave irradiation using suspension polymerization. Microwave heating preparation greatly reduced the polymerization time to 1h. Physical characteristic tests suggested that these beads were cross-linking and possessed spherical shape, good magnetic response and porous morphologies with a narrow diameter distribution of 70-180 μm. Therefore, these beads displayed the long-term stability after undergoing 100-time extractions. Then, an analytical method for the determination of trace 24-epiBR in plant samples was developed by magnetic polymer bead extraction coupled with high performance liquid chromatography-fluorescence detection. St-co-4-VP magnetic polymer beads demonstrated the higher extraction selectivity for 24-epiBR than other reference compounds. Linear range was 10.00-100.0 μg/L with a relative standard deviation (RSD) of 6.7%, and the detection limit was 6.5 μg/kg. This analytical method was successfully applied to analyze the trace 24-epiBR in cole and breaking-wall rape pollen samples with recoveries of 77.2-90.0% and 72.3-83.4%, respectively, and RSDs were less than 4.1%. The amount of 24-epiBR in real breaking-wall rape pollen samples was found to be 26.2 μg/kg finally. This work proposed a sensitive, rapid, reliable and convenient analytical method for the determination of trace brassinosteroids in complicated plant samples by the use of St-co-4-VP magnetic polymer bead extraction coupled with chromatographic method. PMID:20846659

  15. Microfluidic bead suspension hopper.

    PubMed

    Price, Alexander K; MacConnell, Andrew B; Paegel, Brian M

    2014-05-20

    Many high-throughput analytical platforms, from next-generation DNA sequencing to drug discovery, rely on beads as carriers of molecular diversity. Microfluidic systems are ideally suited to handle and analyze such bead libraries with high precision and at minute volume scales; however, the challenge of introducing bead suspensions into devices before they sediment usually confounds microfluidic handling and analysis. We developed a bead suspension hopper that exploits sedimentation to load beads into a microfluidic droplet generator. A suspension hopper continuously delivered synthesis resin beads (17 μm diameter, 112,000 over 2.67 h) functionalized with a photolabile linker and pepstatin A into picoliter-scale droplets of an HIV-1 protease activity assay to model ultraminiaturized compound screening. Likewise, trypsinogen template DNA-coated magnetic beads (2.8 μm diameter, 176,000 over 5.5 h) were loaded into droplets of an in vitro transcription/translation system to model a protein evolution experiment. The suspension hopper should effectively remove any barriers to using suspensions as sample inputs, paving the way for microfluidic automation to replace robotic library distribution. PMID:24761972

  16. Applications of immuno-magnetic bead and immunofluorescent flow cytometric techniques for the quantitative detection of HAB microalgae

    NASA Astrophysics Data System (ADS)

    Huang, Jian; Wen, Ruobing; Bao, Zhenmin; Sui, Zhenghong; Sun, Ningbo; Kang, Kyoungho

    2012-05-01

    Over the last several decades, harmful algal blooms (HABs) have become a serious environmental problem in many parts of the world. A rapid and accurate detection process for HAB algae has yet to be developed. Heterosigma akashiwo is one of the most important HABs species in China. The objective of this study was to develop an immunologic technique that can rapidly and sensitively count H. akashiwo cells. Five HABs species ( Alexandrium catenella, Thalassiosira sp., Cryptomonas sp., Alexandrium tamarense and Symbiodinium sp.), were used in this study to evaluate the analysis process we developed. A polyclonal antibody with high titers against H. akashiwo was obtained by injecting H. akashiwo cells into rabbits. Immuno-magnetic beads (IMB) were produced via conjugated polyclonal antibodies with magnetic beads and applied to isolate and count H. akashiwo cells from the culture. Results show that 66.7%-91.6% of the cells were captured from unialgal culture by IMBs, and only 5.3%-12.5% of the four other HAB microalgae species were captured, indicating that the constructed IMBs combined specifically with the H. akashiwo cells. At the same time, flow cytometry (FCM) sorting was exploited to screen H. akashiwo cells after labeling with FITC conjugated polyclonal antibodies. Using the FCM technique, 91.7% of the targeted cells were sorted out from mixed microalgae samples in just a few minutes. These results indicate that both antibody-involved IMB and antibody-based FCM techniques are highly effective at detecting and quantifying HAB species. These techniques, especially immuno-magnetic separation, have low associated cost, and are fast and simple processes compared with other techniques currently in use.

  17. Sliced Magnetic Polyacrylamide Hydrogel with Cell-Adhesive Microarray Interface: A Novel Multicellular Spheroid Culturing Platform.

    PubMed

    Hu, Ke; Zhou, Naizhen; Li, Yang; Ma, Siyu; Guo, Zhaobin; Cao, Meng; Zhang, Qiying; Sun, Jianfei; Zhang, Tianzhu; Gu, Ning

    2016-06-22

    Cell-adhesive properties are of great significance to materials serving as extracellular matrix mimics. Appropriate cell-adhesive property of material interface can balance the cell-matrix interaction and cell-cell interaction and can promote cells to form 3D structures. Herein, a novel magnetic polyacrylamide (PAM) hydrogel fabricated via combining magnetostatic field induced magnetic nanoparticles assembly and hydrogel gelation was applied as a multicellular spheroids culturing platform. When cultured on the cell-adhesive microarray interface of sliced magnetic hydrogel, normal and tumor cells from different cell lines could rapidly form multicellular spheroids spontaneously. Furthermore, cells which could only form loose cell aggregates in a classic 3D cell culture model (such as hanging drop system) were able to be promoted to form multicellular spheroids on this platform. In the light of its simplicity in fabricating as well as its effectiveness in promoting formation of multicellular spheroids which was considered as a prevailing tool in the study of the microenvironmental regulation of tumor cell physiology and therapeutic problems, this composite material holds promise in anticancer drugs or hyperthermia therapy evaluation in vitro in the future. PMID:27258682

  18. Liquid carry-over in an injection moulded all-polymer chip system for immiscible phase magnetic bead-based solid-phase extraction

    NASA Astrophysics Data System (ADS)

    Kistrup, Kasper; Skotte Sørensen, Karen; Wolff, Anders; Fougt Hansen, Mikkel

    2015-04-01

    We present an all-polymer, single-use microfluidic chip system produced by injection moulding and bonded by ultrasonic welding. Both techniques are compatible with low-cost industrial mass-production. The chip is produced for magnetic bead-based solid-phase extraction facilitated by immiscible phase filtration and features passive liquid filling and magnetic bead manipulation using an external magnet. In this work, we determine the system compatibility with various surfactants. Moreover, we quantify the volume of liquid co-transported with magnetic bead clusters from Milli-Q water or a lysis-binding buffer for nucleic acid extraction (0.1 (v/v)% Triton X-100 in 5 M guanidine hydrochloride). A linear relationship was found between the liquid carry-over and mass of magnetic beads used. Interestingly, similar average carry-overs of 1.74(8) nL/μg and 1.72(14) nL/μg were found for Milli-Q water and lysis-binding buffer, respectively.

  19. New advances in electrochemical biosensors for the detection of toxins: Nanomaterials, magnetic beads and microfluidics systems. A review.

    PubMed

    Reverté, Laia; Prieto-Simón, Beatriz; Campàs, Mònica

    2016-02-18

    The use of nanotechnology in bioanalytical devices has special advantages in the detection of toxins of interest in food safety and environmental applications. The low levels to be detected and the small size of toxins justify the increasing number of publications dealing with electrochemical biosensors, due to their high sensitivity and design versatility. The incorporation of nanomaterials in their development has been exploited to further increase their sensitivity, providing simple and fast devices, with multiplexed capabilities. This paper gives an overview of the electrochemical biosensors that have incorporated carbon and metal nanomaterials in their configurations for the detection of toxins. Biosensing systems based on magnetic beads or integrated into microfluidics systems have also been considered because of their contribution to the development of compact analytical devices. The roles of these materials, the methods used for their incorporation in the biosensor configurations as well as the advantages they provide to the analyses are summarised. PMID:26826685

  20. Microgels at the Water/Oil Interface: In Situ Observation of Structural Aging and Two-Dimensional Magnetic Bead Microrheology.

    PubMed

    Huang, Shilin; Gawlitza, Kornelia; von Klitzing, Regine; Gilson, Laurent; Nowak, Johannes; Odenbach, Stefan; Steffen, Werner; Auernhammer, Günter K

    2016-01-26

    Stimuli-responsive microgels can be used as stabilizers for emulsions. However, the details of structure and the viscoelastic property of the microgel-laden interface are still not well-known. We synthesized fluorescently labeled microgels and used confocal microscopy to observe their arrangement at the water/oil interface. The microgels aggregated spontaneously at the interface, and the aggregated structure reorganized due to thermal motion. The structure of the interfacial layer formed by microgels depended on the microgel concentration at the interface. We suggest that the structure was controlled by the aggregation and adsorption of microgels at the interface. The interparticle separation between microgels at the interface decreased over time, implying a slow aging process of the microgels at the interface. Magnetic beads were introduced at the interface and used to trigger deformation of the microgel layer. Under compression and shear the microgels in the aggregated structure rearranged, leading to plastic deformation, and some elastic responses were also observed. PMID:26704516

  1. Diagnostic model of saliva peptide finger print analysis of oral squamous cell carcinoma patients using weak cation exchange magnetic beads

    PubMed Central

    Jiang, Wei-Peng; Wang, Zhen; Xu, Li-Xin; Peng, Xin; Chen, Feng

    2015-01-01

    Saliva diagnostics utilizing nanotechnology and molecular technologies to detect oral squamous cell carcinoma (OSCC) has become an attractive field of study. However, no specific methods have been established. To refine the diagnostic power of saliva peptide fingerprints for the early detection of OSCC, we screened the expression spectrum of salivary peptides in 40 T1 stage OSCC patients (and healthy controls) using MALDI-TOF-MS combined with magnetic beads. Fifty proteins showed significantly different expression levels in the OSCC samples (P<0.05). Potential biomarkers were also predicted. The novel diagnostic proteomic model with m/z peaks of 1285.6 Da and 1432.2 Da are of certain value for early diagnosis of OSCC. PMID:26182373

  2. Rapid Detection and Isolation of Escherichia coli O104:H4 from Milk Using Monoclonal Antibody-coated Magnetic Beads.

    PubMed

    Luciani, Mirella; Di Febo, Tiziana; Zilli, Katiuscia; Di Giannatale, Elisabetta; Armillotta, Gisella; Manna, Laura; Minelli, Fabio; Tittarelli, Manuela; Caprioli, Alfredo

    2016-01-01

    Monoclonal antibodies (MAbs) specific for the lipopolysaccharide (LPS) of Escherichia coli O104:H4 were produced by fusion of Sp2/O-Ag-14 mouse myeloma cells with spleen cells of Balb/c mice, immunized with heat-inactivated and sonicated E. coli O104:H4 bacterial cells. Four MAbs specific for the E. coli O104:H4 LPS (1E6G6, 1F4C9, 3G6G7, and 4G10D2) were characterized and evaluated for the use in a method for the detection of E. coli O104:H4 in milk samples that involves antibody conjugation to magnetic microbeads to reduce time and increase the efficiency of isolation. MAb 1E6G6 was selected and coupled to microbeads, then used for immuno-magnetic separation (IMS); the efficiency of the IMS method for E. coli O104:H4 isolation from milk was evaluated and compared to that of the EU RL VTEC conventional culture-based isolation procedure. Milk suspensions also containing other pathogenic bacteria that could potentially be found in milk (Campylobacter jejuni, Listeria monocytogenes, and Staphylococcus aureus) were also tested to evaluate the specificity of MAb-coated beads. Beads coated with MAb 1E6G6 showed a good ability to capture the E. coli O104:H4, even in milk samples contaminated with other bacteria, with a higher number of E. coli O104:H4 CFU reisolated in comparison with the official method (121 and 41 CFU, respectively, at 10(3) E. coli O104:H4 initial load; 19 and 6 CFU, respectively, at 10(2) E. coli O104:H4 initial load; 1 and 0 CFU, respectively, at 10(1) E. coli O104:H4 initial load). The specificity was 100%. PMID:27379071

  3. Rapid Detection and Isolation of Escherichia coli O104:H4 from Milk Using Monoclonal Antibody-coated Magnetic Beads

    PubMed Central

    Luciani, Mirella; Di Febo, Tiziana; Zilli, Katiuscia; Di Giannatale, Elisabetta; Armillotta, Gisella; Manna, Laura; Minelli, Fabio; Tittarelli, Manuela; Caprioli, Alfredo

    2016-01-01

    Monoclonal antibodies (MAbs) specific for the lipopolysaccharide (LPS) of Escherichia coli O104:H4 were produced by fusion of Sp2/O-Ag-14 mouse myeloma cells with spleen cells of Balb/c mice, immunized with heat-inactivated and sonicated E. coli O104:H4 bacterial cells. Four MAbs specific for the E. coli O104:H4 LPS (1E6G6, 1F4C9, 3G6G7, and 4G10D2) were characterized and evaluated for the use in a method for the detection of E. coli O104:H4 in milk samples that involves antibody conjugation to magnetic microbeads to reduce time and increase the efficiency of isolation. MAb 1E6G6 was selected and coupled to microbeads, then used for immuno-magnetic separation (IMS); the efficiency of the IMS method for E. coli O104:H4 isolation from milk was evaluated and compared to that of the EU RL VTEC conventional culture-based isolation procedure. Milk suspensions also containing other pathogenic bacteria that could potentially be found in milk (Campylobacter jejuni, Listeria monocytogenes, and Staphylococcus aureus) were also tested to evaluate the specificity of MAb-coated beads. Beads coated with MAb 1E6G6 showed a good ability to capture the E. coli O104:H4, even in milk samples contaminated with other bacteria, with a higher number of E. coli O104:H4 CFU reisolated in comparison with the official method (121 and 41 CFU, respectively, at 103 E. coli O104:H4 initial load; 19 and 6 CFU, respectively, at 102 E. coli O104:H4 initial load; 1 and 0 CFU, respectively, at 101 E. coli O104:H4 initial load). The specificity was 100%. PMID:27379071

  4. Application of porcine gastric mucin-conjugated magnetic beads and polyethylene glycol goncentration and detection of human noroviruses from green onion and grape

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Objective: To set up detection methods for norovirus in fruits and vegetables by using porcine gastric mucin-conjugated magnetic beads (PGM-MB) and polyethylene glycol 8000 (PEG8000) concentrating and detecting the norovirus in green onion and grape. Methods: The highest virus dilution given a posit...

  5. Efficient isolation of pure and functional mitochondria from mouse tissues using automated tissue disruption and enrichment with anti-TOM22 magnetic beads.

    PubMed

    Franko, Andras; Baris, Olivier R; Bergschneider, Eva; von Toerne, Christine; Hauck, Stefanie M; Aichler, Michaela; Walch, Axel K; Wurst, Wolfgang; Wiesner, Rudolf J; Johnston, Ian C D; de Angelis, Martin Hrabĕ

    2013-01-01

    To better understand molecular mechanisms regulating changes in metabolism, as observed e.g. in diabetes or neuronal disorders, the function of mitochondria needs to be precisely determined. The usual isolation methods such as differential centrifugation result in isolates of highly variable quality and quantity. To fulfill the need of a reproducible isolation method from solid tissues, which is suitable to handle parallel samples simultaneously, we developed a protocol based on anti-TOM22 (translocase of outer mitochondrial membrane 22 homolog) antibody-coupled magnetic beads. To measure oxygen consumption rate in isolated mitochondria from various mouse tissues, a traditional Clark electrode and the high-throughput XF Extracellular Flux Analyzer were used. Furthermore, Western blots, transmission electron microscopic and proteomic studies were performed to analyze the purity and integrity of the mitochondrial preparations. Mitochondrial fractions isolated from liver, brain and skeletal muscle by anti-TOM22 magnetic beads showed oxygen consumption capacities comparable to previously reported values and little contamination with other organelles. The purity and quality of isolated mitochondria using anti-TOM22 magnetic beads was compared to traditional differential centrifugation protocol in liver and the results indicated an obvious advantage of the magnetic beads method compared to the traditional differential centrifugation technique. PMID:24349272

  6. Planar Hall effect bridge sensors with NiFe/Cu/IrMn stack optimized for self-field magnetic bead detection

    NASA Astrophysics Data System (ADS)

    Henriksen, Anders Dahl; Rizzi, Giovanni; Hansen, Mikkel Fougt

    2016-03-01

    The stack composition in trilayer Planar Hall effect bridge sensors is investigated experimentally to identify the optimal stack for magnetic bead detection using the sensor self-field. The sensors were fabricated using exchange-biased stacks Ni80Fe20(tFM)/Cu(tCu)/Mn80Ir20(10 nm) with tFM = 10, 20, and 30 nm, and 0 ≤ tCu ≤ 0.6 nm. The sensors were characterized by magnetic hysteresis measurements, by measurements of the sensor response vs. applied field, and by measurements of the sensor response to a suspension of magnetic beads magnetized by the sensor self-field due to the sensor bias current. The exchange bias field was found to decay exponentially with tCu and inversely with tFM. The reduced exchange field for larger values of tFM and tCu resulted in higher sensitivities to both magnetic fields and magnetic beads. We argue that the maximum magnetic bead signal is limited by Joule heating of the sensors and, thus, that the magnetic stacks should be compared at constant power consumption. For a fixed sensor geometry, the figure of merit for this comparison is the magnetic field sensitivity normalized by the sensor bias voltage. In this regard, we found that sensors with tFM = 20 nm or 30 nm outperformed those with tFM = 10 nm by a factor of approximately two, because the latter have a reduced AMR ratio. Further, the optimum layer thicknesses, tCu ≈ 0.6 nm and tFM = 20-30 nm, gave a 90% higher signal compared to the corresponding sensors with tCu = 0 nm.

  7. Magnetic Bead/Gold Nanoparticle Double-Labeled Primers for Electrochemical Detection of Isothermal Amplified Leishmania DNA.

    PubMed

    de la Escosura-Muñiz, Alfredo; Baptista-Pires, Luis; Serrano, Lorena; Altet, Laura; Francino, Olga; Sánchez, Armand; Merkoçi, Arben

    2016-01-13

    A novel methodology for the isothermal amplification of Leishmania DNA using labeled primers combined with the advantages of magnetic purification/preconcentration and the use of gold nanoparticle (AuNP) tags for the sensitive electrochemical detection of such amplified DNA is developed. Primers labeled with AuNPs and magnetic beads (MBs) are used for the first time for the isothermal amplification reaction, being the amplified product ready for the electrochemical detection. The electrocatalytic activity of the AuNP tags toward the hydrogen evolution reaction allows the rapid quantification of the DNA on screen-printed carbon electrodes. Amplified products from the blood of dogs with Leishmania (positive samples) are discriminated from those of healthy dogs (blank samples). Quantitative studies demonstrate that the optimized method allows us to detect less than one parasite per microliter of blood (8 × 10(-3) parasites in the isothermal amplification reaction). This pioneering approach is much more sensitive than traditional methods based on real-time polymerase chain reaction (PCR), and is also more rapid, cheap, and user-friendly. PMID:26578391

  8. Use of carboxylated cellulose nanofibrils-filled magnetic chitosan hydrogel beads as adsorbents for Pb(II).

    PubMed

    Zhou, Yiming; Fu, Shiyu; Zhang, Liangliang; Zhan, Huaiyu; Levit, Mikhail V

    2014-01-30

    Novel magnetic hydrogel beads (m-CS/PVA/CCNFs), consisting of carboxylated cellulose nanofibrils (CCNFs), amine-functionalized magnetite nanoparticles and poly(vinyl alcohol) (PVA) blended chitosan (CS), were prepared by an instantaneous gelation method. SEM, XRD, and TGA techniques were applied to investigate the structure of the hydrogel materials. The magnetic hydrogels were employed as absorbents for removal of Pb(II) ions from aqueous solutions and the fundamental adsorption behavior was studied. Experimental results revealed that the m-CS/PVA/CCNFs hydrogels exhibit higher adsorption capacity with the value of 171.0mg/g, and the carboxylate groups on the CCNFs surface play an important role in Pb(II) adsorption. Moreover, adsorption isotherm data were reliably described by the Langmuir model and the adsorption kinetics closely followed pseudo-second order model. Additionally, the Pb(II)-loaded m-CS/PVA/CCNFs hydrogels could be easily regenerated in weak acid solution and the adsorption effectiveness of 90% can be maintained after the 4 cycles. PMID:24299751

  9. Mesoporous silica beads embedded with semiconductor quantum dots and iron oxide nanocrystals: dual-function microcarriers for optical encoding and magnetic separation.

    PubMed

    Sathe, Tushar R; Agrawal, Amit; Nie, Shuming

    2006-08-15

    Mesoporous beads are promising materials for embedding functional nanoparticles because of their nanometer-sized pores and large surface areas. Here we report the development of silica microbeads embedded with both semiconductor quantum dots (QD) and iron oxide (Fe3O4) nanocrystals as a new class of dual-function carriers for optical encoding and magnetic separation. The embedding (doping) process is carried out by either simultaneous or sequential addition of quantum dots and iron oxide (Fe3O4) nanocrystals in solution. The doping process is fast and quantitative, but the incorporated iron oxide strongly attenuates the signal intensity of QD fluorescence. We find that this attenuation is not due to conventional fluorescence quenching but is caused by the broad optical absorption spectrum of mixed-valence Fe3O4. For improved biocompatibility and reduced nonspecific binding, the encoded beads are further coated with amphiphilic polymers such as octylamine poly(acrylic acid). The results indicate that the polymer-coated beads are well suited for target capturing and enrichment, yielding magnetic separation efficiencies higher than 99%. By combining the multiplexing capability of QDs with the superparamagnetic properties of iron oxide nanocrystals, this class of encoded beads is expected to find broad applications in high-throughput and multiplexed biomolecular assays. PMID:16906704

  10. Sensitivity enhancement of an electrochemical immunosensor through the electrocatalysis of magnetic bead-supported non-enzymatic labels.

    PubMed

    Akter, Rashida; Kyun Rhee, Choong; Rahman, Md Aminur

    2014-04-15

    An ultrasensitive non-enzymatic electrochemical carcinoembryonic antigen (CEA) immunosensor was fabricated by the immobilization of a monoclonal CEA antibody (anti-CEA) on a protein A (PA) attached-gold nanoparticles (AuNPs)-deposited electrochemically prepared polydopamine film (e-PD/AuNPs). Magnetic beads (MB)-supported and CEA-conjugated multiple 3,3',5,5'-tetramethylbenzidine (TMB) was used as electrochemical labels. The detection was based on the measurements of the electrocatalyzed oxidation of ascorbic acid (AA) by the multiple TMB labels after competitive binding between MB/TMB-conjugated-CEA and free-CEA. The electrocatalyzed oxidation current of AA by TMB decreased with increasing concentration of the free-CEA as the amount of CEA/MB/TMB labels decreased at the immunosensor probe. The immunosensor surface was characterized using electrochemical impedance spectroscopy, Fourier transform infrared spectroscopy, quartz crystal microbalance, and scanning electron microscopy techniques. Cyclic voltammetry (CV) and differential pulse voltammetry (DPV) techniques were used to monitor the electrocatalyzed response. The proposed immunosensor exhibited a wide linear dynamic range (1.0 pg/mL to 10.0 ng/mL), low detection limit (1.0±0.04 pg/mL), good selectivity, and long-time stability. It was successfully applied to various CEA spiked human serum samples for the detection of CEA. PMID:24292139

  11. A novel assay for screening inhibitors targeting HIV-1 integrase dimerization based on Ni-NTA magnetic agarose beads

    PubMed Central

    Zhang, Dawei; He, Hongqiu; Liu, Mengmeng; Meng, Zhixia; Guo, Shunxing

    2016-01-01

    Human immunodeficiency virus (HIV)-1 integrase (IN), which mediates integration of viral cDNA into the cellular chromosome, is a validated antiviral drug target. Three IN inhibitors, raltegravir, elvitegravir and dolutegravir, have been clinically approved since 2008. However, drug resistance have emerged in infected patients receiving treatment using these drugs which share the same mechanism of action and have a low genetic barrier for resistance. Therefore, there is an urgent need to develop drugs with novel mechanism. IN requires a precise and dynamic equilibrium between several oligomeric species for its activities. The modulation of the process which is termed as IN oligomerization, presents an interesting allosteric target for drug development. In this research, we developed a magnetic beads based approach to assay the IN dimerization. Then, using the assay we screened a library of 1000 Food and Drug Administration (FDA)-approved drugs for IN dimerization inhibitors and identified dexlansoprazole as a potential IN dimerization inhibitor. In conclusion, the assay presented here has been proven to be sensitive and specific for the detection of IN dimerization as well as for the identification of antiviral drugs targeting IN dimerization. Moreover, a FDA-approved proton-pump inhibitors, dexlansoprazole, was identified as a potential inhibitor for IN dimerization. PMID:27137477

  12. Adsorptive removal of Lead from water by the effective and reusable magnetic cellulose nanocomposite beads entrapping activated bentonite.

    PubMed

    Luo, Xiaogang; Lei, Xiaojuan; Xie, Xiuping; Yu, Bo; Cai, Ning; Yu, Faquan

    2016-10-20

    Many efforts have been driven to decontaminate the drinking water, and the development of efficient adsorbents with the advantages of cost-effectiveness and operating convenience for the removal of Pb(2+) from water is a major challenge. This work was aimed to explore the possibility of using cellulose-based adsorbents for efficient adsorption of Pb(2+). The millimeter-scale magnetic cellulose-based nanocomposite beads were fabricated via an optimal extrusion dropping technology by blending cellulose with the carboxyl-functionalized magnetite nanoparticles and acid-activated bentonite in NaOH/urea aqueous solution, and then they had been tested to evaluate the effectiveness in the removal of Pb(2+) from water. The effects of contact time, initial heavy metal ion concentrations, adsorption isotherms and solution pH on the sorption behavior were studied. The thermodynamic parameters (ΔG, ΔH and ΔS) indicated that the adsorption processes were feasible, spontaneous, endothermic and mainly controlled by chemical mechanisms. The reusability of the adsorbent was also studied. PMID:27474609

  13. Rapid magnetic bead based sample preparation for automated and high throughput N-glycan analysis of therapeutic antibodies.

    PubMed

    Váradi, Csaba; Lew, Clarence; Guttman, András

    2014-06-17

    Full automation to enable high throughput N-glycosylation profiling and sequencing with good reproducibility is vital to fulfill the contemporary needs of the biopharmaceutical industry and requirements of national regulatory agencies. The most prevalently used glycoanalytical methods of capillary electrophoresis and hydrophilic interaction liquid chromatography, while very efficient, both necessitate extensive sample preparation and cleanup, including glycoprotein capture, N-glycan release, fluorescent derivatization, purification, and preconcentration steps during the process. Currently used protocols to fulfill these tasks require multiple centrifugation and vacuum-centrifugation steps, making liquid handling robot mediated automated sample preparation difficult and expensive. In this paper we report on a rapid magnetic bead based sample preparation approach that enables full automation including all the process phases just in a couple of hours without requiring any centrifugation and/or vacuum centrifugation steps. This novel protocol has been compared to conventional glycan sample preparation strategies using standard glycoproteins (IgG, fetuin, and RNase B) and featured rapid processing time, high release and labeling efficiency, good reproducibility, and the potential of easy automation. PMID:24909945

  14. Rapid removal of copper with magnetic poly-acrylic weak acid resin: quantitative role of bead radius on ion exchange.

    PubMed

    Fu, Lichun; Shuang, Chendong; Liu, Fuqiang; Li, Aimin; Li, Yan; Zhou, Yang; Song, Haiou

    2014-05-15

    A novel magnetic weak acid resin NDMC was self-synthesized for the removal of Cu(2+) from aqueous solutions. NDMC showed superior properties on the removal of Cu(2+) compared to commercial resins C106 and IRC-748, which was deeply investigated by adsorption isotherms and kinetic tests. The equilibrium adsorption amount of Cu(2+) onto NDMC (267.2mg/g) was almost twice as large as that onto IRC-748 (120.0mg/g). The adsorption kinetics of Cu(2+) onto the three resins fitted well with the pseudo-second-order equation. The initial adsorption rate h of NDMC was about 4 times that of C106 and nearly 8 times that of IRC-748 at the initial concentration of 500mg/L. External surface area was determined to be the key factor in rate-controlling by further analyzing the adsorption thermodynamics, kinetics parameters and physicochemical properties of the resins. NDMC resin with the smallest bead radius possessed the largest external surface and therefore exhibited the fastest kinetics. The adsorption amount of Cu(2+) onto NDMC was not influenced as the concentration of Na(+) increased from 1.0 to 10.0mM/L. Dilute HCl solution could effectively desorb Cu(2+). NDMC demonstrated high stability during 10 adsorption/desorption cycles, showing great potential in the rapid removal of Cu(2+) from wastewater. PMID:24681592

  15. Thrombin-linked aptamer assay for detection of platelet derived growth factor BB on magnetic beads in a sandwich format.

    PubMed

    Guo, Limin; Zhao, Qiang

    2016-09-01

    Here we describe a thrombin-linked aptamer assay (TLAA) for protein by using thrombin as an enzyme label, harnessing enzyme activity of thrombin and aptamer affinity binding. TLAA converts detection of specific target proteins to the detection of thrombin by using a DNA sequence that consists of two aptamers with the first aptamer binding to the specific target protein and the second aptamer binding to thrombin. Through the affinity binding, the thrombin enzyme is labeled on the protein target, and thrombin catalyzes the hydrolysis of small peptide substrate into product, generating signals for quantification. As a proof of principle, we show a sandwich TLAA for platelet derived growth factor BB (PDGF-BB) by using anti-PDGF-BB antibody coated on magnetic beads and an oligonucleotide containing the aptamer for PDGF-BB and the aptamer for thrombin. The binding of PDGF-BB to both the antibody and the aptamer results in labeling the complex with thrombin. We achieved detection of PDGF-BB at 16 pM. This TLAA contributes a new application of thrombin and its aptamer in bioanalysis, and shows potentials in assay developments. PMID:27343590

  16. Magnetic bead-based fluorescence immunoassay for aflatoxin B1 in food using biofunctionalized rhodamine B-doped silica nanoparticles.

    PubMed

    Tang, Dianping; Yu, Yongliang; Niessner, Reinhard; Miró, Manuel; Knopp, Dietmar

    2010-10-01

    A simple and sensitive fluorescence immunoassay for the detection of aflatoxin B(1) (AFB(1), as a model compound) in food was developed using AFB(1)-bovine serum albumin conjugate (AFB(1)-BSA)-functionalized magnetic beads as immunosensing probes. The recognition elements were prepared by doping of rhodamine B (RB) fluorophore into silica nanoparticles followed by immobilization of monoclonal anti-AFB(1) antibodies on the silica shell. Based on a competitive-type immunoassay format, the assay was performed both in low-binding polypropylene 96-well microtiter plates (MTPs) and in an automated sequential injection (SI) format. Similar detection limit (LOD) of 0.2 ng mL(-1)vs. 0.1 ng mL(-1) but narrower dynamic working linear range of 0.5-7 ng mL(-1)vs. 0.5-30 ng mL(-1) was obtained toward AFB(1) standards with the flow setup compared to the MTP format. Intra-batch assay precision was substantially improved (≤5.3% vs.≤8.7%) by resorting to the SI manifold. The proposed method features unbiased identification of negative (blank) and positive samples. No significant differences at the 95% confidence level were encountered in the analysis of naturally contaminated peanut samples between the proposed immunoassay and liquid chromatography for determination of AFB(1). PMID:20820489

  17. A novel assay for screening inhibitors targeting HIV-1 integrase dimerization based on Ni-NTA magnetic agarose beads.

    PubMed

    Zhang, Dawei; He, Hongqiu; Liu, Mengmeng; Meng, Zhixia; Guo, Shunxing

    2016-01-01

    Human immunodeficiency virus (HIV)-1 integrase (IN), which mediates integration of viral cDNA into the cellular chromosome, is a validated antiviral drug target. Three IN inhibitors, raltegravir, elvitegravir and dolutegravir, have been clinically approved since 2008. However, drug resistance have emerged in infected patients receiving treatment using these drugs which share the same mechanism of action and have a low genetic barrier for resistance. Therefore, there is an urgent need to develop drugs with novel mechanism. IN requires a precise and dynamic equilibrium between several oligomeric species for its activities. The modulation of the process which is termed as IN oligomerization, presents an interesting allosteric target for drug development. In this research, we developed a magnetic beads based approach to assay the IN dimerization. Then, using the assay we screened a library of 1000 Food and Drug Administration (FDA)-approved drugs for IN dimerization inhibitors and identified dexlansoprazole as a potential IN dimerization inhibitor. In conclusion, the assay presented here has been proven to be sensitive and specific for the detection of IN dimerization as well as for the identification of antiviral drugs targeting IN dimerization. Moreover, a FDA-approved proton-pump inhibitors, dexlansoprazole, was identified as a potential inhibitor for IN dimerization. PMID:27137477

  18. Isolation of prostate cancer cell subpopulations of functional interest by use of an on-chip magnetic bead-based cell separator

    NASA Astrophysics Data System (ADS)

    Estes, Matthew D.; Ouyang, Bin; Ho, Shuk-mei; Ahn, Chong H.

    2009-09-01

    This work presents the design, fabrication and characterization of a modular magnetic bead-based cell separation device developed for the sequential sorting of a heterogeneous prostate cancer (CaP) cell population. The chief aim is cell sorting carried out on the basis of surface marker expression, serially selecting cellular subpopulations for capture by the use of antibody-coated magnetic beads. The markers of interest, prostate specific membrane antigen (PSMA) and CD10 were selected for their relevance to ongoing CaP development research. The separation device was fabricated out of plastic, by the use of cyclic olefin copolymer (COC) injection molding, nickel-iron electroplating and thermoplastic fusion bonding. Effective depletion and enrichment of cell subsets based on multiple surface markers was achieved. Various flow rates and incubation times were tested for optimizing the sorting procedure.

  19. Detection of Leishmania-specific DNA and surface antigens using a combination of functionalized magnetic beads and cadmium selenite quantum dots.

    PubMed

    Andreadou, Margarita; Liandris, Emmanouil; Gazouli, Maria; Mataragka, Antonia; Tachtsidis, Ilias; Goutas, Nikolaοs; Vlachodimitropoulos, Dimitrios; Ikonomopoulos, John

    2016-04-01

    Leishmaniosis is a zoonotic disease that affects millions of people especially in resource-poor settings. The development of reliable diagnostic assays that do not require dedicated equipment or highly trained personnel would improve early diagnosis and effective control. For this purpose, a combination of magnetic bead and cadmium selenite quantum dot probes was applied for the detection of Leishmania-specific surface antigens (proteins) and DNA. Both analytes are isolated from the solution using magnetic bead capture probes whereas the presence of the targeted molecules is demonstrated by quantum dot detection probes. The sensitivity and specificity of this method reached 100% based on an assessment performed on 55 cultured isolates of various microbial pathogens. The low limit of detection was 3125 ng/μl and 10(3)cells/ml for Leishmania DNA and protein, respectively. The method shows considerable potential for clinical application in human and veterinary medicine, especially in resource-poor settings. PMID:26658854

  20. Development of an in situ magnetic beads based RT-PCR method for electrochemiluminescent detection of rotavirus

    NASA Astrophysics Data System (ADS)

    Zhan, Fangfang; Zhou, Xiaoming

    2012-12-01

    Rotaviruses are double-stranded RNA viruses belonging to the family of enteric pathogens. It is a major cause of diarrhoeal disease in infants and young children worldwide. Consequently, rapid and accurate detection of rotaviruses is of great importance in controlling and preventing food- and waterborne diseases and outbreaks. Reverse transcription-polymerase chain reaction (RT-PCR) is a reliable method that possesses high specificity and sensitivity. It has been widely used to detection of viruses. Electrochemiluminescence (ECL) can be considered as an important and powerful tool in analytical and clinical application with high sensitivity, excellent specificity, and low cost. Here we have developed a method for the detection of rotavirus by combining in situ magnetic beads (MBs) based RT-PCR with ECL. RT of rotavirus RNA was carried out in a traditional way and the resulting cDNA was directly amplified on MBs. Forward primers were covalently bounded to MBs and reverse primers were labeled with tris-(2, 2'-bipyridyl) ruthenium (TBR). During the PCR cycling, the TBR labeled products were directly loaded and enriched on the surface of MBs. Then the MBs-TBR complexes could be analyzed by a magnetic ECL platform without any post-modification or post-incubation which avoid some laborious manual operations and achieve rapid yet sensitive detection. In this study, rotavirus from fecal specimens was successfully detected within 2 h, and the limit of detection was estimated to be 104copies/μL. This novel in situ MBs based RT-PCR with ECL detection method can be used for pathogen detection in food safety field and clinical diagnosis.

  1. PCR amplification from single DNA molecules on magnetic beads in emulsion: application for high-throughput screening of transcription factor targets

    PubMed Central

    Kojima, Takaaki; Takei, Yoshiaki; Ohtsuka, Miharu; Kawarasaki, Yasuaki; Yamane, Tsuneo; Nakano, Hideo

    2005-01-01

    We have developed a novel method of genetic library construction on magnetic microbeads based on solid-phase single-molecule PCR in a fine and robust water-phase compartment formed in water-in-oil (w/o) emulsions. In this method, critically diluted DNA fragments were distributed over the emulsion as templates, where beads crosslinked with multiple primers and other PCR components were encapsulated to form multiple reaction compartments. The delivered DNA was then amplified and covalently immobilized on the beads in parallel, within individual compartments, to construct a genetic library on beads (GLOBE), which was readily applicable to a genomewide global scanning of genetic elements recognized by a defined DNA-binding protein. We constructed a GLOBE of Paracoccus denitrificans and selected gene beads that were bound to the His-tagged transcription factor PhaR by flow cytometry. As a result of flow cytometry screening with an anti-His fluorescent antibody, the PhaR target fragments were enriched 1200-fold from this library with this system. Therefore, this system is a powerful tool for analyzing the transcription network on a genomewide scale. PMID:16214800

  2. Development of a fluorescent enzyme-linked DNA aptamer-magnetic bead sandwich assay and portable fluorometer for sensitive and rapid leishmania detection in sandflies.

    PubMed

    Bruno, John G; Richarte, Alicia M; Phillips, Taylor; Savage, Alissa A; Sivils, Jeffrey C; Greis, Alex; Mayo, Michael W

    2014-01-01

    A fluorescent peroxidase-linked DNA aptamer-magnetic bead sandwich assay is described which detects as little as 100 ng of soluble protein extracted from Leishmania major promastigotes with a high molarity chaotropic salt. Lessons learned during development of the assay are described and elucidate the pros and cons of using fluorescent dyes or nanoparticles and quantum dots versus a more consistent peroxidase-linked Amplex Ultra Red (AUR; similar to resazurin) fluorescence version of the assay. While all versions of the assays were highly sensitive, the AUR-based version exhibited lower variability between tests. We hypothesize that the AUR version of this assay is more consistent, especially at low analyte levels, because the fluorescent product of AUR is liberated into bulk solution and readily detectable while fluorophores attached to the reporter aptamer might occasionally be hidden behind magnetic beads near the detection limit. Conversely, fluorophores could be quenched by nearby beads or other proximal fluorophores on the high end of analyte concentration, if packed into a small area after magnetic collection when an enzyme-linked system is not used. A highly portable and rechargeable battery-operated fluorometer with on board computer and color touchscreen is also described which can be used for rapid (<1 h) and sensitive detection of Leishmania promastigote protein extracts (∼ 100 ng per sample) in buffer or sandfly homogenates for mapping of L. major parasite geographic distributions in wild sandfly populations. PMID:24222436

  3. Synthesis and characterization of SIRT6 protein coated magnetic beads: identification of a novel inhibitor of SIRT6 deacetylase from medicinal plant extracts.

    PubMed

    Yasuda, M; Wilson, D R; Fugmann, S D; Moaddel, R

    2011-10-01

    SIRT6 is a histone deacetylase that has been proposed as a potential therapeutic target for metabolic disorders and the prevention of age-associated diseases. Thus, the identification of compounds that modulate SIRT6 activity could be of great therapeutic importance. The aim of this study was to develop a screening method for the identification of novel modulators of SIRT6 from a natural plant extract. We immobilized SIRT6 onto the surface of magnetic beads, and assessed SIRT6 enzymatic activity on synthetic acetylated histone tails (H3K9Ac) by measuring products of the deacetylation process. The SIRT6 coated magnetic beads were then suspended in fenugreek seed extract (Trigonella foenum-graecum) as a bait to identify active ligands that suppress SIRT6 activity. While the entire extract also inhibited SIRT6 activity in a cell-based assay, the inhibitory effect of two flavonoids from this extract, quercetin and vitexin, was only detected in vitro. This is the first report on the use of protein-coated magnetic beads for the identification of an active ligand from a botanical matrix, and it sets the basis for the de novo identification of SIRT6 modulators from complex biological mixtures. PMID:21854049

  4. The Synthesis and characterization of SIRT6 protein coated magnetic beads: Identification of a novel inhibitor of SIRT6 deacetylase from medicinal plant extracts

    PubMed Central

    Yasuda, M.; Wilson, D.R.; Fugmann, S.D.; Moaddel, R.

    2011-01-01

    SIRT6 is a histone deacetylase that has been proposed as a potential therapeutic target for metabolic disorders and the prevention of age-associated diseases. Thus the identification of compounds that modulate SIRT6 activity could be of great therapeutic importance. The aim of this study was to develop a screening method for the identification of novel modulators of SIRT6 from a natural plant extract. We immobilized SIRT6 onto the surface of magnetic beads, and assessed SIRT6 enzymatic activity on synthetic acetylated histone tails (H3K9Ac) by measuring products of the deacetylation process. The SIRT6 coated magnetic beads were then suspended in fenugreek seed extract (Trigonella foenumgraecum) as a bait to identify active ligands suppressing SIRT6 activity. While the whole extract also inhibited SIRT6 activity in a cell-based assay, the inhibitory effect of two flavonoids from this extract, quercetin and vitexin, was only detected in vitro. This is the first report for the use of protein-coated magnetic beads for the identification of an active ligand from a botanical matrix, and sets the basis for the de novo identification of SIRT6 modulators from complex biological mixtures. PMID:21854049

  5. Comperative study of catalase immobilization on chitosan, magnetic chitosan and chitosan-clay composite beads.

    PubMed

    Başak, Esra; Aydemir, Tülin; Dinçer, Ayşe; Becerik, Seda Çınar

    2013-12-01

    Catalase was immobilized on chitosan and modified chitosan. Studies were carried out on free-immobilized catalase concerning the determination of optimum temperature, pH, thermal, storage stability, reusability, and kinetic parameters. Optimum temperature and pH for free catalase and catalase immobilized were found as 35°C and 7.0, respectively. After 100 times of repeated tests, the immobilized catalases on chitosan-clay and magnetic chitosan maintain over 50% and 60% of the original activity, respectively. The ease of catalase immobilization on low-cost matrices and good stability upon immobilization in the present study make it a suitable product for further use in the food industry. PMID:23687952

  6. Facile fabrication of an electrochemical aptasensor based on magnetic electrode by using streptavidin modified magnetic beads for sensitive and specific detection of Hg(2.).

    PubMed

    Wu, Dan; Wang, Yaoguang; Zhang, Yong; Ma, Hongmin; Pang, Xuehui; Hu, Lihua; Du, Bin; Wei, Qin

    2016-08-15

    In this work, a novel electrochemical aptasensor was developed for sensitive and specific detection of Hg(2+) based on thymine-Hg(2+)-thymine (T-Hg(2+)-T) structure via application of thionine (Th) as indicator signal. For the fabrication of the aptasensor, streptavidin modified magnetic beads (Fe3O4-SA) was firmly immobilized onto the magnetic glassy carbon electrode (MGCE) benefited from its magnetic character. Then biotin labeled T-riched single stranded DNA (Bio-ssDNA) connected with Fe3O4-SA specifically and steadily because of the specific binding capacity between streptavidin and biotin. The stable structure of T-Hg(2+)-T formed in the present of Hg(2+) provided convenience for the intercalation of Th. The detection of Hg(2+) was achieved by recording the differential pulse voltammetry (DPV) signal of Th. Under optimal experimental conditions, the linear range of the fabricated electrochemical aptasensor was 1-200nmol/L, with a detection limit of 0.33nmol/L. Furthermore, the proposed aptasensor may find a potential application for the detection of Hg(2+) in real water sample analysis. PMID:27031185

  7. On-Chip Magnetic Bead Manipulation and Detection Using a Magnetoresistive Sensor-Based Micro-Chip: Design Considerations and Experimental Characterization.

    PubMed

    Gooneratne, Chinthaka P; Kodzius, Rimantas; Li, Fuquan; Foulds, Ian G; Kosel, Jürgen

    2016-01-01

    The remarkable advantages micro-chip platforms offer over cumbersome, time-consuming equipment currently in use for bio-analysis are well documented. In this research, a micro-chip that includes a unique magnetic actuator (MA) for the manipulation of superparamagnetic beads (SPBs), and a magnetoresistive sensor for the detection of SPBs is presented. A design methodology, which takes into account the magnetic volume of SPBs, diffusion and heat transfer phenomena, is presented with the aid of numerical analysis to optimize the parameters of the MA. The MA was employed as a magnetic flux generator and experimental analysis with commercially available COMPEL™ and Dynabeads(®) demonstrated the ability of the MA to precisely transport a small number of SPBs over long distances and concentrate SPBs to a sensing site for detection. Moreover, the velocities of COMPEL™ and Dynabead(®) SPBs were correlated to their magnetic volumes and were in good agreement with numerical model predictions. We found that 2.8 μm Dynabeads(®) travel faster, and can be attracted to a magnetic source from a longer distance, than 6.2 μm COMPEL™ beads at magnetic flux magnitudes of less than 10 mT. The micro-chip system could easily be integrated with electronic circuitry and microfluidic functions, paving the way for an on-chip biomolecule quantification device. PMID:27571084

  8. Magnetic bead and gold nanoparticle probes based immunoassay for β-casein detection in bovine milk samples.

    PubMed

    Li, Y S; Meng, X Y; Zhou, Y; Zhang, Y Y; Meng, X M; Yang, L; Hu, P; Lu, S Y; Ren, H L; Liu, Z S; Wang, X R

    2015-04-15

    In this work, a double-probe based immunoassay was developed for rapid and sensitive determination of β-casein in bovine milk samples. In the method, magnetic beads (MBs), employed as supports for the immobilization of anti-β-casein polyclonal antibody (PAb), were used as the capture probe. Colloidal gold nanoparticles (AuNPs), employed as a bridge for loading anti-β-casein monoclonal antibody (McAb) and horseradish peroxidase (HRP), were used as the amplification probe. The presence of β-casein causes the sandwich structures of MBs-PAb-β-casein-McAb-AuNPs through the interaction between β-casein and the anti-β-casein antibodies. The HRP, used as an enzymatic-amplified tracer, can catalytically oxidize the substrate 3,3',5,5'-tetramethylbenzidine (TMB), generating optical signals that are proportional to the quantity of β-casein. The linear range of the immunoassay was from 6.5 to 1520ngmL(-1). The limit of detection (LOD) was 4.8ngmL(-1) which was 700 times lower than that of MBs-antibody-HRP based immunoassay and 6-7 times lower than that from the microplate-antibody-HRP based assay. The recoveries of β-casein from bovine milk samples were from 95.0% to 104.3% that had a good correlation coefficient (R(2)=0.9956) with those obtained by an official standard Kjeldahl method. For higher sensitivity, simple sample pretreatment and shorter time requirement of the antigen-antibody reaction, the developed immunoassay demonstrated the viability for detection of β-casein in bovine milk samples. PMID:25522084

  9. Novel circulating peptide biomarkers for esophageal squamous cell carcinoma revealed by a magnetic bead-based MALDI-TOFMS assay.

    PubMed

    Jia, Kun; Li, Wei; Wang, Feng; Qu, Haixia; Qiao, Yuanyuan; Zhou, Lanping; Sun, Yulin; Ma, Qingwei; Zhao, Xiaohang

    2016-04-26

    Esophageal squamous cell carcinoma (ESCC) is one of the most common malignant neoplasms worldwide. Patients are often diagnosed at advanced stages with poor prognosis due to the absence of obvious early symptoms. Here, we applied a high-throughput serum peptidome analysis to identify circulating peptide markers of ESCC. Weak cationic exchange magnetic beads coupled to matrix-assisted laser desorption/ionization time-of-flight mass spectrometry was used for two-stage proteotypic peptide profiling in complex serum samples collected from 477 cancer patients and healthy controls. We established a genetic algorithm model containing three significantly differentially expressed peptides at 1,925.5, 2,950.6 and 5,900.0 Da with a sensitivity and specificity of 97.00% and 95.92% in the training set and 97.03% and 100.00% in the validation set, respectively. The model's diagnostic capability was significantly better than SCC-Ag and Cyfra 21-1, especially for early stage ESCC, with an achieved sensitivity of 96.94%. Subsequently, these peptides were identified as fragments of AHSG, TSP1 and FGA by linear ion trap-orbitrap hybrid tandem mass spectrometry. Notably, increased tissue and serum levels of TSP1 in ESCC were verified and correlated with disease progression. In addition, tissue TSP1 was an independent poor prognostic factor in ESCC. In conclusion, the newly established circulating peptide panel and identified proteins could serve as potential biomarkers for the early detection and diagnosis of ESCC. Nevertheless, a larger cohort will be required for further unequivocal validation of their clinical application. PMID:26993605

  10. Droplet-based magnetic bead immunoassay using microchannel-connected multiwell plates (μCHAMPs) for the detection of amyloid beta oligomers.

    PubMed

    Park, Min Cheol; Kim, Moojong; Lim, Gun Taek; Kang, Sung Min; An, Seong Soo A; Kim, Tae Song; Kang, Ji Yoon

    2016-06-21

    Multiwell plates are regularly used in analytical research and clinical diagnosis but often require laborious washing steps and large sample or reagent volumes (typically, 100 μL per well). To overcome such drawbacks in the conventional multiwell plate, we present a novel microchannel-connected multiwell plate (μCHAMP) that can be used for automated disease biomarker detection in a small sample volume by performing droplet-based magnetic bead immunoassay inside the plate. In this μCHAMP-based immunoassay platform, small volumes (30-50 μL) of aqueous-phase working droplets are stably confined within each well by the simple microchannel structure (200-300 μm in height and 0.5-1 mm in width), and magnetic beads are exclusively transported into an adjacent droplet through the oil-filled microchannels assisted by a magnet array aligned beneath and controlled by a XY-motorized stage. Using this μCHAMP-based platform, we were able to perform parallel detection of synthetic amyloid beta (Aβ) oligomers as a model analyte for the early diagnosis of Alzheimer's disease (AD). This platform easily simplified the laborious and consumptive immunoassay procedure by achieving automated parallel immunoassay (32 assays per operation in 3-well connected 96-well plate) within 1 hour and at low sample consumption (less than 10 μL per assay) with no cumbersome manual washing step. Moreover, it could detect synthetic Aβ oligomers even below 10 pg mL(-1) concentration with a calculated detection limit of ∼3 pg mL(-1). Therefore, the μCHAMP and droplet-based magnetic bead immunoassay, with the combination of XY-motorized magnet array, would be a useful platform in the diagnosis of human disease, including AD, which requires low consumption of the patient's body fluid sample and automation of the entire immunoassay procedure for high processing capacity. PMID:27185215

  11. Magnetic bead droplet immunoassay of oligomer amyloid β for the diagnosis of Alzheimer's disease using micro-pillars to enhance the stability of the oil-water interface.

    PubMed

    Kim, Jeong Ah; Kim, Moojong; Kang, Sung Min; Lim, Kun Taek; Kim, Tae Song; Kang, Ji Yoon

    2015-05-15

    Despite scientific progress in the study of Alzheimer's disease (AD), it is still challenging to develop a robust and sensitive methodology for the early diagnosis of AD due to the lack of a decisive biomarker in blood. Recent reports on the oligomer amyloid β (Aβ) as a biomarker demonstrated its possibility for identifying early onset of AD in patients, but its low concentration in blood requires highly reliable detection techniques. To overcome the low reliability and labor-intensive procedures of conventional enzyme-linked immunosorbent assay (ELISA), we present a magnetic bead-droplet immunoassay platform for simple and highly sensitive detection of oligomer Aβ for the diagnosis of AD. This microchip consists of chambers that contain water-based reagents or oil for consecutive assay procedures, and there are arrays of micro-pillars fabricated between the two adjacent chambers to form robust water-oil interfaces. With the aid of these micro-pillars, magnetic beads can stably pass through each chamber by linearly actuating a magnet along the microchip. The robust water-oil interface and simple procedures of the assay make it possible to obtain reliable results from this microchip. The intensity of the fluorescence at the read-out chamber increased quantitatively and linearly, depending on the amount of serially-diluted standard Aβ solution. The results of the assay indicated that the limit of detection was about 10 pg/mL even though it was done with manual manipulation of the magnet. This platform simplified the complicated ELISA procedure and achieved high sensitivity that was no lower than that of the conventional magnetic bead immunoassay. The magnetic bead-droplet platform reduced the assay time to 45 min, and it also reduced the amount of antibody usage in a single diagnosis significantly (10-30 ng of antibody per single assay). Consequently, this microfluidic chip has strong potential as a feasible system for use in the diagnosis of AD with a fast and

  12. Analysis of glycoproteins in human serum by means of glycospecific magnetic bead separation and LC-MALDI-TOF/TOF analysis with automated glycopeptide detection.

    PubMed

    Sparbier, Katrin; Asperger, Arndt; Resemann, Anja; Kessler, Irina; Koch, Sonja; Wenzel, Thomas; Stein, Günter; Vorwerg, Lars; Suckau, Detlev; Kostrzewa, Markus

    2007-09-01

    Comprehensive proteomic analyses require efficient and selective pre-fractionation to facilitate analysis of post-translationally modified peptides and proteins, and automated analysis workflows enabling the detection, identification, and structural characterization of the corresponding peptide modifications. Human serum contains a high number of glycoproteins, comprising several orders of magnitude in concentration. Thereby, isolation and subsequent identification of low-abundant glycoproteins from serum is a challenging task. selective capturing of glycopeptides and -proteins was attained by means of magnetic particles specifically functionalized with lectins or boronic acids that bind to various structural motifs. Human serum was incubated with differentially functionalized magnetic micro-particles (lectins or boronic acids), and isolated proteins were digested with trypsin. Subsequently, the resulting complex mixture of peptides and glycopeptides was subjected to LC-MALDI analysis and database searching. In parallel, a second magnetic bead capturing was performed on the peptide level to separate and analyze by LC-MALDI intact glycopeptides, both peptide sequence and glycan structure. Detection of glycopeptides was achieved by means of a software algorithm that allows extraction and characterization of potential glycopeptide candidates from large LC-MALDI-MS/MS data sets, based on N-glycopeptide-specific fragmentation patterns and characteristic fragment mass peaks, respectively. By means of fast and simple glycospecific capturing applied in conjunction with extensive LC-MALDI-MS/MS analysis and novel data analysis tools, a high number of low-abundant proteins were identified, comprising known or predicted glycosylation sites. According to the specific binding preferences of the different types of beads, complementary results were obtained from the experiments using either magnetic ConA-, LCA-, WGA-, and boronic acid beads, respectively. PMID:17916798

  13. A Highly Selective and Sensitive Fluorescence Detection Method of Glyphosate Based on an Immune Reaction Strategy of Carbon Dot Labeled Antibody and Antigen Magnetic Beads.

    PubMed

    Wang, Duo; Lin, Bixia; Cao, Yujuan; Guo, Manli; Yu, Ying

    2016-08-01

    A sensitive fluorescence detection method for glyphosate (GLY) was established based on immune reaction. First, carbon dot labeled antibodies (lgG-CDs) which were able to specifically identify glyphosate were prepared with the environmentally friendly carbon dots (CDs) and glyphosate antibody (lgG). lgG-CDs could be used to in situ visualize the distribution of glyphosate in plant tissues. In order to eliminate the effects of excess lgG-CDs on the determination of GLY, antigen magnetic beads Fe3O4-GLY based on magnetic nanoparticles Fe3O4 and glyphosate were constructed and utilized to couple with the excess lgG-CDs. After magnetic separation to remove antigen magnetic beads, there was a linear relationship between the fluorescence intensity of lgG-CDs and the logarithmic concentration of glyphosate in the range of 0.01-80 μg/mL with a detection limit of 8 ng/mL. The method was used for the detection of glyphosate in Pearl River water, tea, and soil samples with satisfactory recovery ratio between 87.4% and 103.7%. PMID:27403652

  14. An enzyme-free and resettable platform for the construction of advanced molecular logic devices based on magnetic beads and DNA.

    PubMed

    Zhang, Siqi; Wang, Kun; Huang, Congcong; Li, Zhenyu; Sun, Ting; Han, De-Man

    2016-08-25

    A series of multiple logic circuits based on magnetic beads and DNA are constructed to perform resettable nonarithmetic functions, including a digital comparator, 4-to-2 encoder and 2-to-3 decoder, 2-to-1 encoder and 1-to-2 decoder. The signal reporter is composed of a G-quadruplex/NMM complex and a AuNP-surface immobilized molecular beacon. It is the first time that the designed DNA-based nonarithmetic nanodevices can share the same DNA platform with a reset function, which has great potential application in information processing at the molecular level. Another novel feature of the designed system is that the developed nanodevices are operated on a simple DNA/magnetic bead platform and share a constant threshold setpoint without the assistance of any negative logic conversion. The reset function is realized by heating the output system and the magnetic separation of the computing modules. Due to the biocompatibility and design flexibility of DNA, these investigations may provide a new route towards the development of resettable advanced logic circuits in biological and biomedical fields. PMID:27524500

  15. The Current Status of DNA Microarrays

    NASA Astrophysics Data System (ADS)

    Shi, Leming; Perkins, Roger G.; Tong, Weida

    DNA microarray technology that allows simultaneous assay of thousands of genes in a single experiment has steadily advanced to become a mainstream method used in research, and has reached a stage that envisions its use in medical applications and personalized medicine. Many different strategies have been developed for manufacturing DNA microarrays. In this chapter, we discuss the manufacturing characteristics of seven microarray platforms that were used in a recently completed large study by the MicroArray Quality Control (MAQC) consortium, which evaluated the concordance of results across these platforms. The platforms can be grouped into three categories: (1) in situ synthesis of oligonucleotide probes on microarrays (Affymetrix GeneChip® arrays based on photolithography synthesis and Agilent's arrays based on inkjet synthesis); (2) spotting of presynthesized oligonucleotide probes on microarrays (GE Healthcare's CodeLink system, Applied Biosystems' Genome Survey Microarrays, and the custom microarrays printed with Operon's oligonucleotide set); and (3) deposition of presynthesized oligonucleotide probes on bead-based microarrays (Illumina's BeadChip microarrays). We conclude this chapter with our views on the challenges and opportunities toward acceptance of DNA microarray data in clinical and regulatory settings.

  16. The Current Status of DNA Microarrays

    NASA Astrophysics Data System (ADS)

    Shi, Leming; Perkins, Roger G.; Tong, Weida

    DNA microarray technology that allows simultaneous assay of thousands of genes in a single experiment has steadily advanced to become a mainstream method used in research, and has reached a stage that envisions its use in medical applications and personalized medicine. Many different strategies have been developed for manufacturing DNA microarrays. In this chapter, we discuss the manu facturing characteristics of seven microarray platforms that were used in a recently completed large study by the MicroArray Quality Control (MAQC) consortium, which evaluated the concordance of results across these platforms. The platforms can be grouped into three categories: (1) in situ synthesis of oligonucleotide probes on microarrays (Affymetrix GeneChip® arrays based on photolithography synthesis and Agilent's arrays based on inkjet synthesis); (2) spotting of presynthe-sized oligonucleotide probes on microarrays (GE Healthcare's CodeLink system, Applied Biosystems' Genome Survey Microarrays, and the custom microarrays printed with Operon's oligonucleotide set); and (3) deposition of presynthesized oligonucleotide probes on bead-based microarrays (Illumina's BeadChip microar-rays). We conclude this chapter with our views on the challenges and opportunities toward acceptance of DNA microarray data in clinical and regulatory settings.

  17. Detection of Leishmania donovani infection using magnetic beads-based serum peptide profiling by MALDI-TOF MS in mice model.

    PubMed

    Li, Lixia; Li, Jiping; Jin, Hongtao; Shang, Limin; Li, Bo; Wei, Feng; Liu, Quan

    2012-03-01

    Leishmaniasis is an important parasitic disease, and definite diagnosis using a specific and sensitive method is the first step to cure the disease. Here, we present a novel diagnostic strategy based on serum peptide profiling by magnetic beads and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). The serum peptides from the Leishmani donovani-infected and healthy mice were enriched by the optimized magnetic beads. The mass spectrograms were acquired by MALDI-TOF MS and analyzed by the ClinProTools bioinformatics software from Bruker Daltonics. The diagnostic model of serum peptide profiling produced by the ClinProTools software could correctly detect L. donovani infection in mice from the third day post-infection, with the accuracy of 94.1%, sensitivity of 92.4%, and specificity of 97.1%, respectively. The results of the present study suggested that the serum peptide profiling by MALDI-TOF MS is a novel potential tool for the clinical diagnosis of leishmaniasis. PMID:21850454

  18. Magnetic bead fluorescent immunoassay for the rapid detection of the novel inflammation marker YKL40 at the point-of-care.

    PubMed

    Schmalenberg, Michael; Beaudoin, Christopher; Bulst, Ludwig; Steubl, Dominik; Luppa, Peter B

    2015-12-01

    Pneumonia is one of the leading causes of death worldwide.We present a magnetic bead fluorescent sandwich immunoassay that allows rapid serum measurement of the novel inflammation marker YKL40 (CHI3L1) at the point of care (POC) that could aid pneumonia diagnosis. The magnetic beads serve as the solid phase for separation of YKL40 from serum. The readout is performed using a small and robust fluorescence reader,which detects the turnover of a fluorescent substrate. The assay procedure, from sample addition to data retrieval, consists of three steps and is performed in less than 20 min. The presented assay has a linear range from 3 to 111 ng/mL, with a limit of detection of 2.9 ng/mL. The average recoveries were found between 101 and 111%. The developed method was applied in sera from healthy subjects (n= 14; c(YKL40)= 50 ± 49 ng/mL) and from pneumonia patients (n = 14; c(YKL40) = 333.6 ± 225 ng/mL). The elevated YKL40 concentrations in pneumonia-diseased patients are in good agreement with previously published data. The POC-ready device provides a simple immunoassay that could help to optimize pneumonia inflammation diagnostics in low-resource settings. PMID:26434383

  19. Development of a fluorescent enzyme-linked DNA aptamer-magnetic bead sandwich assay and portable fluorometer for sensitive and rapid listeria detection.

    PubMed

    Bruno, John G; Phillips, Taylor; Montez, Tiffany; Garcia, Adrian; Sivils, Jeffrey C; Mayo, Michael W; Greis, Alex

    2015-01-01

    A fluorescent DNA aptamer-magnetic bead sandwich assay was developed to detect listeriolysin O (LLO) protein from pathogenic Listeria bacteria using a peroxidase-linked system, Amplex Ultra Red (AUR; derivatized resazurin) substrate, and a custom-designed handheld fluorometer. The assay is highly sensitive with demonstrated limits of detection (LODs) in the range of 4 to 61 L. monocytogenes cells or the equivalent LLO produced by 4 to 61 cells on average in separate titration trials. Total assay processing and analysis time was approximately 30 mins. The assay has demonstrated the ability to detect 6 species of Listeria as desired by the USDA's Food Safety Inspection Service (FSIS). The portable system was designed to be used primarily with surface swab samples from fomites, but it can also be used to assess enrichment cultures. The minimal time to detect a positive enrichment culture in our hands from an initial 10 cell inoculum in 200 ml of broth has been 8 h post-incubation at 37 °C in shaker flask cultures. An optional automated magnetic bead assay processing and wash device capable of simultaneously processing 6 samples with low and consistent fluorescence background for higher volume central laboratories is also described. PMID:25511112

  20. Early diagnosis of Irkut virus infection using magnetic bead-based serum peptide profiling by MALDI-TOF MS in a mouse model.

    PubMed

    Li, Nan; Liu, Ye; Hao, Zhuo; Zhang, Shoufeng; Hu, Rongliang; Li, Jiping

    2014-01-01

    Early diagnosis is important for the prompt post-exposure prophylaxis of lyssavirus infections. To diagnose Irkut virus (IRKV) infection during incubation in mice, a novel method using magnetic bead-based serum peptide profiling by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) has been established. For this test, serum peptides were concentrated by adsorption to and elution from the magnetic bead-based weak cation ion exchanger. Mass spectrograms obtained by MALDI-TOF MS were analyzed using ClinProTools bioinformatics software. Construction of the diagnostic model was performed using serum samples from mice infected with IRKV and rabies virus (RABV) BD06, Flury-LEP, and SRV9 (as controls). The method accurately diagnosed sera 2, 4 and 8 days after IRKV and RABV infections. The sensitivity, specificity, and total accuracy of diagnosis were 86.7%, 95.2%, and 92.9%, respectively. However, IRKV could not be differentiated from RABV 1 day after infection. The results of the present study indicate that serum peptide profiling by MALDI-TOF MS is a promising technique for the early clinical diagnosis of lyssavirus infections and needs to be further tested in humans and farm animals. PMID:24670473

  1. Plastic protein microarray to investigate the molecular pathways of magnetic nanoparticle-induced nanotoxicity

    NASA Astrophysics Data System (ADS)

    Liu, Yingshuai; Li, Xuelian; Bao, Shujuan; Lu, Zhisong; Li, Qing; Li, Chang Ming

    2013-05-01

    Superparamagnetic iron oxide nanoparticles (SPIONs) (about 15 nm) were synthesized via a hydrothermal method and characterized by field emission scanning electron microscopy, transmission electron microscopy, dynamic light scattering, x-ray diffraction, and vibrating sample magnetometer. The molecular pathways of SPIONs-induced nanotoxicity was further investigated by protein microarrays on a plastic substrate from evaluation of cell viability, reactive oxygen species (ROS) generation and cell apoptosis. The experimental results reveal that 50 μg ml-1 or higher levels of SPIONs cause significant loss of cell viability, considerable generation of ROS and cell apoptosis. It is proposed that high level SPIONs could induce cell apoptosis via a mitochondria-mediated intrinsic pathway by activation of caspase 9 and caspase 3, an increase of the Bax/Bcl-2 ratio, and down-regulation of HSP70 and HSP90 survivor factors.

  2. A highly efficient bead extraction technique with low bead number for digital microfluidic immunoassay.

    PubMed

    Huang, Cheng-Yeh; Tsai, Po-Yen; Lee, I-Chin; Hsu, Hsin-Yun; Huang, Hong-Yuan; Fan, Shih-Kang; Yao, Da-Jeng; Liu, Cheng-Hsien; Hsu, Wensyang

    2016-01-01

    Here, we describe a technique to manipulate a low number of beads to achieve high washing efficiency with zero bead loss in the washing process of a digital microfluidic (DMF) immunoassay. Previously, two magnetic bead extraction methods were reported in the DMF platform: (1) single-side electrowetting method and (2) double-side electrowetting method. The first approach could provide high washing efficiency, but it required a large number of beads. The second approach could reduce the required number of beads, but it was inefficient where multiple washes were required. More importantly, bead loss during the washing process was unavoidable in both methods. Here, an improved double-side electrowetting method is proposed for bead extraction by utilizing a series of unequal electrodes. It is shown that, with proper electrode size ratio, only one wash step is required to achieve 98% washing rate without any bead loss at bead number less than 100 in a droplet. It allows using only about 25 magnetic beads in DMF immunoassay to increase the number of captured analytes on each bead effectively. In our human soluble tumor necrosis factor receptor I (sTNF-RI) model immunoassay, the experimental results show that, comparing to our previous results without using the proposed bead extraction technique, the immunoassay with low bead number significantly enhances the fluorescence signal to provide a better limit of detection (3.14 pg/ml) with smaller reagent volumes (200 nl) and shorter analysis time (<1 h). This improved bead extraction technique not only can be used in the DMF immunoassay but also has great potential to be used in any other bead-based DMF systems for different applications. PMID:26858807

  3. Lab-on-a-disc agglutination assay for protein detection by optomagnetic readout and optical imaging using nano- and micro-sized magnetic beads.

    PubMed

    Uddin, Rokon; Burger, Robert; Donolato, Marco; Fock, Jeppe; Creagh, Michael; Hansen, Mikkel Fougt; Boisen, Anja

    2016-11-15

    We present a biosensing platform for the detection of proteins based on agglutination of aptamer coated magnetic nano- or microbeads. The assay, from sample to answer, is integrated on an automated, low-cost microfluidic disc platform. This ensures fast and reliable results due to a minimum of manual steps involved. The detection of the target protein was achieved in two ways: (1) optomagnetic readout using magnetic nanobeads (MNBs); (2) optical imaging using magnetic microbeads (MMBs). The optomagnetic readout of agglutination is based on optical measurement of the dynamics of MNB aggregates whereas the imaging method is based on direct visualization and quantification of the average size of MMB aggregates. By enhancing magnetic particle agglutination via application of strong magnetic field pulses, we obtained identical limits of detection of 25pM with the same sample-to-answer time (15min 30s) using the two differently sized beads for the two detection methods. In both cases a sample volume of only 10µl is required. The demonstrated automation, low sample-to-answer time and portability of both detection instruments as well as integration of the assay on a low-cost disc are important steps for the implementation of these as portable tools in an out-of-lab setting. PMID:27183287

  4. Highly specific and rapid immuno-fluorescent visualization and detection of E. coli O104:H4 with protein-A coated magnetic beads based LST-MUG assay.

    PubMed

    Barizuddin, Syed; Balakrishnan, Baskar; Stringer, R Cody; Dweik, Majed

    2015-08-01

    A method combining immunomagnetic separation and fluorescent sensing was developed to detect Escherichia coli (E. coli) O104:H4. The antibody specific to E. coli O104:H4 was immobilized on protein A-coated magnetic beads. This protein-A-anti E. coli O104:H4 complex was used to bind Fluorescein IsoThioCyanate (FITC) labeled E. coli O104:H4 antigen (whole cell) on it. The goal was to achieve a fluorescently detectable protein-A-anti E. coli O104:H4-E. coli O104:H4 complex on the magnetic beads. Fluorescent microscopy was used to image the magnetic beads. The resulting fluorescence on the beads was due to the FITC labeled antigen binding on the protein-A-anti E. coli O104:H4 immobilized magnetic beads. This visually proves the antigen-antibody binding. The fluorescent imaging results were obtained in 2 h if the minimum available bacteria in the sample were at least 10(5) CFU/ml. If no fluorescence was observed on the magnetic beads during fluorescent imaging, it indicates the bacterial concentration in the sample to be too low for it to have bound to the magnetic beads and hence no detection was possible. To detect bacterial concentration less than 10(5) CFU/ml in the sample, an additional step was required for detection. The magnetic bead complex was added to the LST-MUG (lauryl sulfate tryptose-4-methylumbelliferyl-β-D-glucuronide), a signaling reporter. The E. coli O104:H4 grows in LST-MUG and releases β-glucuronidase enzyme. This enzyme cleaves the MUG substrate that produces 4-methylumbelliferone, a highly fluorescent species. This fluorescence was detected using a spectrofluorometer. The emission peak in the fluorescent spectrum was found to be at 450 nm. The lower and upper detection range for this LST-MUG assay was found to be 2.05×10(5)-4.09×10(8) CFU/ml. The results for the LST-MUG assay for concentrations below 10(5) CFU/ml were ascertained in 8h. The advantages of this technique include the specific detection of bacteria without an enrichment step and

  5. Synthesis of magnetic alginate beads based on Fe3O4 nanoparticles for the removal of 3-methylindole from aqueous solution using Fenton process.

    PubMed

    Hammouda, Samia Ben; Adhoum, Nafaâ; Monser, Lotfi

    2015-08-30

    A novel magnetic heterogeneous catalyst has been developed by incorporation of iron(II) and magnetic functionalized nanoparticles Fe3O4 in alginate beads with the aim of using them in the advanced Fenton oxidation of a malodorous compound (3 methyl-indole: 3-MI). The effects of significant operational parameters such as initial pH, oxidant concentration and catalyst amount were investigated and optimized for a better removal of 3-MI at initial concentration of 20mgL(-1). Besides, the catalyst stability was evaluated according to the iron leached into the aqueous solution. Results revealed that the parameters affecting Fenton catalysis must be carefully chosen to avoid excessive iron release. Under optimized conditions, the magnetic catalyst exhibited a good catalytic performance. Total removal of 3 methyl indole and a remarkable organic mineralization, without significant leaching of iron, were attained within 120min at pH 3.0 by using 0.4gL(-1) of Fe-MABs and 9.8mmolL(-1) of H2O2. The novel magnetic catalyst would be of potential application due to its high efficiency, easy recovery and good structural stability. PMID:25867585

  6. Removal of Hg(II) from aqueous solution by resin loaded magnetic β-cyclodextrin bead and graphene oxide sheet: Synthesis, adsorption mechanism and separation properties.

    PubMed

    Cui, Limei; Wang, Yaoguang; Gao, Liang; Hu, Lihua; Wei, Qin; Du, Bin

    2015-10-15

    Resin loaded magnetic β-cyclodextrin bead and graphene oxide sheet (MCD-GO-R) was synthesized successfully and found to be an excellent adsorbent for Hg(II) removal. The as-prepared adsorbent was characterized by SEM, FTIR, BET, magnetization curve and zeta potential analysis respectively. Good magnetic performance made MCD-GO-R simply recover from aqueous solution at low magnetic field within 30s. And also, the rich functional groups and outstanding dispersity play an important role in the adsorption process. The maximum adsorption capacity was 88.43 mg g(-1) at 323 K and pH 7.1. The as-prepared adsorbent could perform well in a wide pH range from 4.0 to 10.0. Static adsorption experimental data showed good correlation with pseudo-second-order model and Freundlich isotherm models. It was found that the contaminant adsorption was accomplished mainly via chelation or ion exchange and come to equilibrium in only 30 min. All experimental results, especially the excellent reproducibility and resistance to ion interference, suggest that MCD-GO-R has promising applications in water treatment. PMID:26092115

  7. Carboxymethyl cellulose film as a substrate for microarray fabrication.

    PubMed

    Shlyapnikov, Yuri M; Shlyapnikova, Elena A; Morozov, Victor N

    2014-02-18

    Magnetic beads (MB) are widely used for quick and highly sensitive signal detection in microarray-based assays. However, this technique imposes stringent requirements for smoothness and adhesive properties of the surface, which most common substrates do not satisfy. We report here a new type of substrate for microarrays with a low adhesion to MB-thermally cross-linked carboxymethyl cellulose (CMC) film. This substrate can be readily fabricated on a conventional glass slide. A highly cross-linked CMC film (∼1 cross-link per monomer unit) possesses a surface smooth on a nanometer scale and a low adhesion to protein-coated MB, which partly originates from electrostatic repulsion of MB from negatively charged CMC surface. The efficiency of the CMC substrate is demonstrated hereby in fabrication of microarrays for the detection of three bacterial toxins: cholera toxin, staphylococcal enterotoxin A, and toxic shock syndrome toxin. The assay employing a primary antibodies arrayed on a CMC surface and detection of the bound bacterial toxins with a biotinylated secondary antibodies and streptavidin-coated MB resulted in a limits of detection as low as 0.1 ng/mL. The CMC-based microarrays demonstrated very high storage stability; their activity did not change after one year storage at room temperature. PMID:24446727

  8. Asynchronous magnetic bead rotation (AMBR) micro-viscometer for rapid, sensitive and label-free studies of bacterial growth and drug sensitivity

    PubMed Central

    Sinn, Irene; Albertson, Theodore; Kinnunen, Paivo; Breslauer, David N.; McNaughton, Brandon H.; Burns, Mark A.; Kopelman, Raoul

    2012-01-01

    The long turnaround time in antimicrobial susceptibility testing (AST) endangers patients and encourages the administration of wide spectrum antibiotics, thus resulting in alarming increases of multi-drug resistant pathogens. A method for faster detection of bacterial proliferation presents one avenue towards addressing this global concern. We report on a label-free asynchronous magnetic bead rotation (AMBR) based viscometry method that rapidly detects bacterial growth and determines drug sensitivity by measuring changes in the suspension’s viscosity. With this platform, we observed the growth of a uropathogenic Escherichia coli isolate, with an initial concentration of 50 cells per drop, within 20 minutes; in addition, we determined the gentamicin minimum inhibitory concentration (MIC) of the E. coli isolate within 100 minutes. We thus demonstrated a label-free, micro-viscometer platform that can measure bacterial growth and drug susceptibility more rapidly, with lower initial bacterial counts than existing commercial systems, and potentially with any microbial strains. PMID:22507307

  9. Rapid and Specific Enrichment of Culturable Gram Negative Bacteria Using Non-Lethal Copper-Free Click Chemistry Coupled with Magnetic Beads Separation

    PubMed Central

    Fugier, Emilie; Dumont, Audrey; Malleron, Annie; Poquet, Enora; Mas Pons, Jordi; Baron, Aurélie; Vauzeilles, Boris; Dukan, Sam

    2015-01-01

    Currently, identification of pathogenic bacteria present at very low concentration requires a preliminary culture-based enrichment step. Many research efforts focus on the possibility to shorten this pre-enrichment step which is needed to reach the minimal number of cells that allows efficient identification. Rapid microbiological controls are a real public health issue and are required in food processing, water quality assessment or clinical pathology. Thus, the development of new methods for faster detection and isolation of pathogenic culturable bacteria is necessary. Here we describe a specific enrichment technique for culturable Gram negative bacteria, based on non-lethal click chemistry and the use of magnetic beads that allows fast detection and isolation. The assimilation and incorporation of an analog of Kdo, an essential component of lipopolysaccharides, possessing a bio-orthogonal azido function (Kdo-N3), allow functionalization of almost all Gram negative bacteria at the membrane level. Detection can be realized through strain-promoted azide-cyclooctyne cycloaddition, an example of click chemistry, which interestingly does not affect bacterial growth. Using E. coli as an example of Gram negative bacterium, we demonstrate the excellent specificity of the technique to detect culturable E. coli among bacterial mixtures also containing either dead E. coli, or live B. subtilis (as a model of microorganism not containing Kdo). Finally, in order to specifically isolate and concentrate culturable E. coli cells, we performed separation using magnetic beads in combination with click chemistry. This work highlights the efficiency of our technique to rapidly enrich and concentrate culturable Gram negative bacteria among other microorganisms that do not possess Kdo within their cell envelope. PMID:26061695

  10. Gold bead implants.

    PubMed

    Durkes, T E

    1992-03-01

    Gold bead implantation is an experimental area of study in the acupuncture field dealing with chronic diseases. Special acupuncture techniques are required to implant the gold beads successfully in the proper location. Gold beads are used to treat degenerative joint disease, osteochondritis, osteochondritis dessicans, ventral spondylosis, and seizures. PMID:1581658

  11. Isolating Sperm from Cell Mixtures Using Magnetic Beads Coupled with an Anti-PH-20 Antibody for Forensic DNA Analysis

    PubMed Central

    Zhao, Xing-Chun; Wang, Le; Sun, Jing; Jiang, Bo-Wei; Zhang, Er-Li; Ye, Jian

    2016-01-01

    Vaginal swabs taken in rape cases usually contain epithelial cells from the victim and sperm from the assailant and forensic DNA analysis requires separation of sperm from these cell mixtures. PH-20, which is a glycosylphosphatidylinositol-anchored hyaluronidase located on the head of sperm, has important functions in fertilization. Here we describe a newly developed method for sperm isolation using anti-PH-20 antibody-coupled immunomagnetic beads (anti-PH-20 IMBs). Optical microscopy and scanning electron microscopy showed the IMBs recognized the head of sperm specifically and exhibited a great capacity to capture sperm cells. However, we found it necessary to incubate the IMB–sperm complex with DNase I before sperm lysis in order to remove any female DNA completely. We compared the sensitivity of anti-PH-20 IMBs in sperm and epithelial cell discrimination to those coated with a different anti-sperm antibody (anti-SP-10, anti-ADAM2 or anti-JLP). Only the anti-PH-20 IMBs succeeded in isolating sperm from cell mixtures at a sperm/epithelial cell ratio of 103:105. Further, our method exhibited greater power and better stability for sperm isolation compared to the traditional differential lysis strategy. Taken together, the anti-PH-20 IMB method described here could be effective for the isolation of sperm needed to obtain a single-sourced DNA profile as an aid to identifying the perpetrator in sexual assault cases. PMID:27442128

  12. Isolating Sperm from Cell Mixtures Using Magnetic Beads Coupled with an Anti-PH-20 Antibody for Forensic DNA Analysis.

    PubMed

    Zhao, Xing-Chun; Wang, Le; Sun, Jing; Jiang, Bo-Wei; Zhang, Er-Li; Ye, Jian

    2016-01-01

    Vaginal swabs taken in rape cases usually contain epithelial cells from the victim and sperm from the assailant and forensic DNA analysis requires separation of sperm from these cell mixtures. PH-20, which is a glycosylphosphatidylinositol-anchored hyaluronidase located on the head of sperm, has important functions in fertilization. Here we describe a newly developed method for sperm isolation using anti-PH-20 antibody-coupled immunomagnetic beads (anti-PH-20 IMBs). Optical microscopy and scanning electron microscopy showed the IMBs recognized the head of sperm specifically and exhibited a great capacity to capture sperm cells. However, we found it necessary to incubate the IMB-sperm complex with DNase I before sperm lysis in order to remove any female DNA completely. We compared the sensitivity of anti-PH-20 IMBs in sperm and epithelial cell discrimination to those coated with a different anti-sperm antibody (anti-SP-10, anti-ADAM2 or anti-JLP). Only the anti-PH-20 IMBs succeeded in isolating sperm from cell mixtures at a sperm/epithelial cell ratio of 103:105. Further, our method exhibited greater power and better stability for sperm isolation compared to the traditional differential lysis strategy. Taken together, the anti-PH-20 IMB method described here could be effective for the isolation of sperm needed to obtain a single-sourced DNA profile as an aid to identifying the perpetrator in sexual assault cases. PMID:27442128

  13. Development of a single-antigen magnetic bead assay (SAMBA) for the sensitive detection of HPA-1a alloantibodies using tag-engineered recombinant soluble β3 integrin.

    PubMed

    Skaik, Younis; Battermann, Anja; Hiller, Oliver; Meyer, Oliver; Figueiredo, Constanca; Salama, Abdulgabar; Blasczyk, Rainer

    2013-05-31

    Timely and accurate testing for human platelet antigen 1a (HPA-1a) alloantibodies is vital for clinical diagnosis of neonatal alloimmune thrombocytopenia (NAIT). Current antigen-specific assays used for the detection of HPA-1 alloantibodies are technically very complex and cumbersome for most diagnostic laboratories. Hence, we designed and applied recombinant soluble (rs) β3 integrins displaying HPA-1a or HPA-1b epitopes for the development of a single-antigen magnetic bead assay (SAMBA). Soluble HPA-1a and HPA-1b were produced recombinantly in human embryonic kidney 293 (HEK293) cells and differentially tagged. The recombinant soluble proteins were then immobilized onto paramagnetic beads and used for analysis of HPA-1 alloantibodies by enzyme-linked immunosorbent assay (ELISA). HPA-1a serum samples (n=7) from NAIT patients, inert sera and sera containing non-HPA-1a antibodies were used to evaluate the sensitivity and specificity of the SAMBA. Fusion of V5-His or GS-SBP-His tags to the rsβ3 integrins resulted in high-yield expression. SAMBA was able to detect all HPA-1a and -1b alloantibodies recognized by monoclonal antibody-specific immobilization of platelet antigens assay (MAIPA). No cross-reactions between the sera were observed. Two out of seven of the HPA-1a alloantibody-containing sera demonstrated weak to moderate reactivity in MAIPA but strong signals in SAMBA. SAMBA provides a very reliable method for the detection of HPA-1 antibodies with high specificity and sensitivity. This simple and rapid assay can be adapted for use in any routine laboratory and can be potentially adapted for use on automated systems. PMID:23454035

  14. Preparation of magnetic indole-3-acetic acid imprinted polymer beads with 4-vinylpyridine and β-cyclodextrin as binary monomer via microwave heating initiated polymerization and their application to trace analysis of auxins in plant tissues.

    PubMed

    Zhang, Yi; Li, Yuanwen; Hu, Yuling; Li, Gongke; Chen, Yueqin

    2010-11-19

    Auxin is a crucial phytohormone for precise control of growth and development of plants. Due to its low concentration in plant tissues which are rich in interfering substances, the accurate determination of auxins remains a challenge. In this paper, a new strategy for isolation and enrichment of auxins from plant tissues was obtained by the magnetic molecularly imprinted polymer (mag-MIP) beads, which were prepared by microwave heating initiated suspension polymerization using indole-3-acetic acid (IAA) as template. In order to obtain higher selective recognition cavities, an enhanced imprinting method based on binary functional monomers, 4-vinylpyridine (4-VP) and β-cyclodextrin (β-CD), was adopted for IAA imprinting. The morphological and magnetic characteristics of the mag-MIP beads were characterized by scanning electron microscopy, Fourier-transform infrared spectroscopy and vibrating sample magnetometry. A majority of resultant beads were within the size range of 80-150μm. Porous surface morphology and good magnetic property were observed. Furthermore, the mag-MIP beads fabricated with 4-VP and β-CD as binary functional monomers exhibited improved recognition ability to IAA, as compared with the mag-MIP beads prepared with the individual monomer separately. Competitive rebinding experiment results revealed that the mag-MIP beads exhibited a higher specific recognition for the template than the non-imprinted polymer (mag-NIP) beads. An extraction method by mag-MIP beads coupled with high performance liquid chromatography (HPLC) was developed for determination of IAA and indole-3-butyric acid (IBA) in plant tissues. Linear ranges for IAA and IBA were in the range of 7.00-100.0μgL(-1) and 10.0-100.0μgL(-1), and the detection limits were 3.9 and 7.4μgL(-1), respectively. The analytical performance was also estimated by seedlings or immature embryos samples from three different plant tissues, pea, rice and wheat. Recoveries were in the range of 70

  15. Electrochemical immunosensor for carcinoembryonic antigen based on nanosilver-coated magnetic beads and gold-graphene nanolabels.

    PubMed

    Chen, Huafeng; Tang, Dianping; Zhang, Bing; Liu, Bingqian; Cui, Yuling; Chen, Guonan

    2012-03-15

    A novel redox-active magnetic nanostructure was synthesized by using a wet chemical method for high-efficiency electrochemical immunoassay of carcinoembryonic antigen (CEA, as a model analyte). The nanostructures based on the combination of a magnetic nanocore, a layer of electroactive poly(o-phenylenediamine) (PPD), and a silver metallic shell displayed good adsorption properties for the attachment of anti-CEA antibody selective to CEA. The magnetic nanostructure presented good redox behaviors to facilitate and modulate the way it was integrated into a magnetic carbon paste electrode. The assay was based on a sandwich-type immunoassay protocol by using nanogold-patterned graphene oxide nanoscales (AuNP-GO), conjugated with horseradish peroxidase-labeled anti-CEA, as secondary antibodies and biofunctionalized magnetic nanostructures as immunosensing probes. Under optimal conditions, the nanoparticle-based immunocomposites exhibited good electrochemical responses for the determination of CEA, and allowed the detection of CEA at a concentration as low as 1.0 pg mL(-1) at a signal-to-noise ratio of 3. In addition, the magnetic immunosensing had good reproducibility, and acceptable accuracy, and could be successfully applied for the detection of CEA in the clinical serum specimens. Significantly, by controlling the target biomolecules, this assay can be easily extended for use with other immunosensings, and thus represents a versatile design routine. PMID:22365686

  16. Development and Validation of a Novel Diagnostic Test for Human Brucellosis Using a Glyco-engineered Antigen Coupled to Magnetic Beads

    PubMed Central

    Ciocchini, Andrés E.; Rey Serantes, Diego A.; Melli, Luciano J.; Iwashkiw, Jeremy A.; Deodato, Bettina; Wallach, Jorge; Feldman, Mario F.; Ugalde, Juan E.; Comerci, Diego J.

    2013-01-01

    Brucellosis is a highly contagious zoonosis and still a major human health problem in endemic areas of the world. Although several diagnostic tools are available, most of them are difficult to implement especially in developing countries where complex health facilities are limited. Taking advantage of the identical structure and composition of the Brucella spp. and Yersinia enterocolitica O:9 O-polysaccharide, we explored the application of a recombinant Y. enterocolitica O:9-polysaccharide-protein conjugate (OAg-AcrA) as a novel antigen for diagnosis of human brucellosis. We have developed and validated an indirect immunoassay using OAg-AcrA coupled to magnetic beads. OAg-AcrA was produced and purified with high yields in Y. enterocolitica O:9 cells co-expressing the oligosaccharyltransferase PglB and the protein acceptor AcrA of Campylobacter jejuni without the need for culturing Brucella. Expression of PglB and AcrA in Y. enterocolitica resulted in the transfer of the host O-polysaccharide from its lipid carrier to AcrA. To validate the assay and determine the cutoff values, a receiver-operating characteristic analysis was performed using a panel of characterized serum samples obtained from healthy individuals and patients of different clinical groups. Our results indicate that, using this assay, it is possible to detect infection caused by the three main human brucellosis agents (B. abortus, B. melitensis and B. suis) and select different cutoff points to adjust sensitivity and specificity levels as needed. A cutoff value of 13.20% gave a sensitivity of 100% and a specificity of 98.57%, and a cutoff value of 16.15% resulted in a test sensitivity and specificity of 93.48% and 100%, respectively. The high diagnostic accuracy, low cost, reduced assay time and simplicity of this new glycoconjugate-magnetic beads assay makes it an attractive diagnostic tool for using not only in clinics and brucellosis reference laboratories but also in locations with limited

  17. Development and validation of a novel diagnostic test for human brucellosis using a glyco-engineered antigen coupled to magnetic beads.

    PubMed

    Ciocchini, Andrés E; Rey Serantes, Diego A; Melli, Luciano J; Iwashkiw, Jeremy A; Deodato, Bettina; Wallach, Jorge; Feldman, Mario F; Ugalde, Juan E; Comerci, Diego J

    2013-01-01

    Brucellosis is a highly contagious zoonosis and still a major human health problem in endemic areas of the world. Although several diagnostic tools are available, most of them are difficult to implement especially in developing countries where complex health facilities are limited. Taking advantage of the identical structure and composition of the Brucella spp. and Yersinia enterocolitica O:9 O-polysaccharide, we explored the application of a recombinant Y. enterocolitica O:9-polysaccharide-protein conjugate (OAg-AcrA) as a novel antigen for diagnosis of human brucellosis. We have developed and validated an indirect immunoassay using OAg-AcrA coupled to magnetic beads. OAg-AcrA was produced and purified with high yields in Y. enterocolitica O:9 cells co-expressing the oligosaccharyltransferase PglB and the protein acceptor AcrA of Campylobacter jejuni without the need for culturing Brucella. Expression of PglB and AcrA in Y. enterocolitica resulted in the transfer of the host O-polysaccharide from its lipid carrier to AcrA. To validate the assay and determine the cutoff values, a receiver-operating characteristic analysis was performed using a panel of characterized serum samples obtained from healthy individuals and patients of different clinical groups. Our results indicate that, using this assay, it is possible to detect infection caused by the three main human brucellosis agents (B. abortus, B. melitensis and B. suis) and select different cutoff points to adjust sensitivity and specificity levels as needed. A cutoff value of 13.20% gave a sensitivity of 100% and a specificity of 98.57%, and a cutoff value of 16.15% resulted in a test sensitivity and specificity of 93.48% and 100%, respectively. The high diagnostic accuracy, low cost, reduced assay time and simplicity of this new glycoconjugate-magnetic beads assay makes it an attractive diagnostic tool for using not only in clinics and brucellosis reference laboratories but also in locations with limited

  18. Screening of inhibitors of glycogen synthase kinase-3β from traditional Chinese medicines using enzyme-immobilized magnetic beads combined with high-performance liquid chromatography.

    PubMed

    Li, Yunfang; Xu, Jia; Chen, Yu; Mei, Zhinan; Xiao, Yuxiu

    2015-12-18

    Glycogen synthase kinase-3β (GSK-3β) was immobilized on magnetic beads (MBs) by affinity method for the first time. The enzyme-immobilized MBs were coupled with high-performance liquid chromatography-ultraviolet (HPLC-UV) technique to establish a cost-effective and reliable method for screening of inhibitors of GSK-3β. A peptide substrate of GSK-3β containing a tyrosine residue was employed since it can be sensitively detected by UV detector at 214nm. The substrate and its phosphorylated product were separated by baseline within 10min. The enzyme activity was determined by the quantification of peak area of the product. Parameters including enzyme immobilization, enzyme reaction and the performance of immobilized-enzyme were investigated. The immobilized enzyme can be reused for 10 times and remain stable for 4 days at 4°C. The inhibitory activities of extracts of 15 traditional Chinese medicines (TCMs) were screened. As a result, three of them including Euonymus fortunei, Amygdalus communis and Garcinia xanthochymus were found possessing high inhibitory activities (inhibition rate >90%). From G. xanthochymus, a new inhibitor of GSK-3β, fukugetin, was discovered with an IC50 value of 3.18±0.07μM. Enzyme kinetics and molecular docking experiments further revealed the inhibitory mechanism, indicating fukugetin was a non-ATP competitive inhibitor interacting with the phosphate recognizing substrate binding site of GSK-3β. PMID:26610618

  19. Glyco-centric lectin magnetic bead array (LeMBA) - proteomics dataset of human serum samples from healthy, Barrett׳s esophagus and esophageal adenocarcinoma individuals.

    PubMed

    Shah, Alok K; Lê Cao, Kim-Anh; Choi, Eunju; Chen, David; Gautier, Benoît; Nancarrow, Derek; Whiteman, David C; Baker, Peter R; Clauser, Karl R; Chalkley, Robert J; Saunders, Nicholas A; Barbour, Andrew P; Joshi, Virendra; Hill, Michelle M

    2016-06-01

    This data article describes serum glycoprotein biomarker discovery and qualification datasets generated using lectin magnetic bead array (LeMBA) - mass spectrometry techniques, "Serum glycoprotein biomarker discovery and qualification pipeline reveals novel diagnostic biomarker candidates for esophageal adenocarcinoma" [1]. Serum samples collected from healthy, metaplastic Barrett׳s esophagus (BE) and esophageal adenocarcinoma (EAC) individuals were profiled for glycoprotein subsets via differential lectin binding. The biomarker discovery proteomics dataset consisting of 20 individual lectin pull-downs for 29 serum samples with a spiked-in internal standard chicken ovalbumin protein has been deposited in the PRIDE partner repository of the ProteomeXchange Consortium with the data set identifier PRIDE: PXD002442. Annotated MS/MS spectra for the peptide identifications can be viewed using MS-Viewer (〈http://prospector2.ucsf.edu/prospector/cgi-bin/msform.cgi?form=msviewer〉) using search key "jn7qafftux". The qualification dataset contained 6-lectin pulldown-coupled multiple reaction monitoring-mass spectrometry (MRM-MS) data for 41 protein candidates, from 60 serum samples. This dataset is available as a supplemental files with the original publication [1]. PMID:27408916

  20. The identification of a novel SIRT6 modulator from Trigonella foenum-graecum using ligand fishing with protein coated magnetic beads.

    PubMed

    Singh, N; Ravichandran, S; Spelman, K; Fugmann, S D; Moaddel, R

    2014-10-01

    SIRT6 is a histone deacetylase that has been proposed as a potential therapeutic target for metabolic disorders and the prevention of age-associated diseases. Thus the identification of compounds that modulate SIRT6 activity could be of great therapeutic importance. We have previously developed an H3K9 deacetylation guided assay with SIRT6 coated magnetic beads (SIRT6-MB). With the developed assay, we identified quercetin, naringenin and vitexin as SIRT6 inhibitors from T. foenum-graecum seed extract using a candidate approach. Currently, the predominant method for the identification of active compounds from a plant extract is carried out through a dereplication process. A novel targeted approach for the direct identification of active compounds from a complex matrix could save time and resources. Herein, we report the application of the SIRT6-MB for 'fishing' experiments utilizing T. foenum-graecum seed extract. In which orientin, and seventeen other compounds were identified as SIRT6 binders. This is the first use of this method for 'fishing' out active ligands from a botanical matrix, and sets the basis for the identification of active compounds from a complex matrix. PMID:24704183

  1. Rapid Synthesis of a Long Double-Stranded Oligonucleotide from a Single-Stranded Nucleotide Using Magnetic Beads and an Oligo Library

    PubMed Central

    Pengpumkiat, Sumate; Koesdjojo, Myra; Rowley, Erik R.; Mockler, Todd C.; Remcho, Vincent T.

    2016-01-01

    Chemical synthesis of oligonucleotides is a widely used tool in the field of biochemistry. Several methods for gene synthesis have been introduced in the growing area of genomics. In this paper, a novel method of constructing dsDNA is proposed. Short (28-mer) oligo fragments from a library were assembled through successive annealing and ligation processes, followed by PCR. First, two oligo fragments annealed to form a dsDNA molecule. The double-stranded oligo was immobilized onto magnetic beads (solid support) via streptavidin-biotin binding. Next, single-stranded oligo fragments were added successively through ligation to form the complete DNA molecule. The synthesized DNA was amplified through PCR and gel electrophoresis was used to characterize the product. Sanger sequencing showed that more than 97% of the nucleotides matched the expected sequence. Extending the length of the DNA molecule by adding single-stranded oligonucleotides from a basis set (library) via ligation enables a more convenient and rapid mechanism for the design and synthesis of oligonucleotides on the go. Coupled with an automated dispensing system and libraries of short oligo fragments, this novel DNA synthesis method would offer an efficient and cost-effective method for producing dsDNA. PMID:26930667

  2. Rapid Synthesis of a Long Double-Stranded Oligonucleotide from a Single-Stranded Nucleotide Using Magnetic Beads and an Oligo Library.

    PubMed

    Pengpumkiat, Sumate; Koesdjojo, Myra; Rowley, Erik R; Mockler, Todd C; Remcho, Vincent T

    2016-01-01

    Chemical synthesis of oligonucleotides is a widely used tool in the field of biochemistry. Several methods for gene synthesis have been introduced in the growing area of genomics. In this paper, a novel method of constructing dsDNA is proposed. Short (28-mer) oligo fragments from a library were assembled through successive annealing and ligation processes, followed by PCR. First, two oligo fragments annealed to form a dsDNA molecule. The double-stranded oligo was immobilized onto magnetic beads (solid support) via streptavidin-biotin binding. Next, single-stranded oligo fragments were added successively through ligation to form the complete DNA molecule. The synthesized DNA was amplified through PCR and gel electrophoresis was used to characterize the product. Sanger sequencing showed that more than 97% of the nucleotides matched the expected sequence. Extending the length of the DNA molecule by adding single-stranded oligonucleotides from a basis set (library) via ligation enables a more convenient and rapid mechanism for the design and synthesis of oligonucleotides on the go. Coupled with an automated dispensing system and libraries of short oligo fragments, this novel DNA synthesis method would offer an efficient and cost-effective method for producing dsDNA. PMID:26930667

  3. Selective collection and detection of MCF-7 breast cancer cells using aptamer-functionalized magnetic beads and quantum dots based nano-bio-probes.

    PubMed

    Hua, Xin; Zhou, Zhenxian; Yuan, Liang; Liu, Songqin

    2013-07-25

    A novel strategy for selective collection and detection of breast cancer cells (MCF-7) based on aptamer-cell interaction was developed. Mucin 1 protein (MUC1) aptamer (Apt1) was covalently conjugated to magnetic beads to capture MCF-7 cell through affinity interaction between Apt1 and MUC1 protein that overexpressed on the surface of MCF-7 cells. Meanwhile, a nano-bio-probe was constructed by coupling of nucleolin aptamer AS1411 (Apt2) to CdTe quantum dots (QDs) which were homogeneously coated on the surfaces of monodispersed silica nanoparticles (SiO2 NPs). The nano-bio-probe displayed similar optical and electrochemical performances to free CdTe QDs, and remained high affinity to nucleolin overexpressed cells through the interaction between AS1411 and nucleolin protein. Photoluminescence (PL) and square-wave voltammetric (SWV) assays were used to quantitatively detect MCF-7 cells. Improved selectivity was obtained by using these two aptamers together as recognition elements simultaneously, compared to using any single aptamer. Based on the signal amplification of QDs coated silica nanoparticles (QDs/SiO2), the detection sensitivity was enhanced and a detection limit of 201 and 85 cells mL(-1) by PL and SWV method were achieved, respectively. The proposed strategy could be extended to detect other cells, and showed potential applications in cell imaging and drug delivery. PMID:23845492

  4. Protein Microarrays

    NASA Astrophysics Data System (ADS)

    Ricard-Blum, S.

    Proteins are key actors in the life of the cell, involved in many physiological and pathological processes. Since variations in the expression of messenger RNA are not systematically correlated with variations in the protein levels, the latter better reflect the way a cell functions. Protein microarrays thus supply complementary information to DNA chips. They are used in particular to analyse protein expression profiles, to detect proteins within complex biological media, and to study protein-protein interactions, which give information about the functions of those proteins [3-9]. They have the same advantages as DNA microarrays for high-throughput analysis, miniaturisation, and the possibility of automation. Section 18.1 gives a brief overview of proteins. Following this, Sect. 18.2 describes how protein microarrays can be made on flat supports, explaining how proteins can be produced and immobilised on a solid support, and discussing the different kinds of substrate and detection method. Section 18.3 discusses the particular format of protein microarrays in suspension. The diversity of protein microarrays and their applications are then reported in Sect. 18.4, with applications to therapeutics (protein-drug interactions) and diagnostics. The prospects for future developments of protein microarrays are then outlined in the conclusion. The bibliography provides an extensive list of reviews and detailed references for those readers who wish to go further in this area. Indeed, the aim of the present chapter is not to give an exhaustive or detailed analysis of the state of the art, but rather to provide the reader with the basic elements needed to understand how proteins are designed and used.

  5. Immobilized magnetic beads based multi-target affinity selection coupled with high performance liquid chromatography-mass spectrometry for screening anti-diabetic compounds from a Chinese medicine "Tang-Zhi-Qing".

    PubMed

    Tao, Yi; Chen, Zhui; Zhang, Yufeng; Wang, Yi; Cheng, Yiyu

    2013-05-01

    We developed an approach for screening bioactive compounds from botanical drug using multiple target-immobilized magnetic beads coupled with high performance liquid chromatography-mass spectrometry. This novel approach was called magnetic beads based multi-target affinity selection-mass spectrometry (MT-ASMS). It can enrich and identify different types of ligands from mixture extracts. Multiple targets (maltase, invertase, lipase) were immobilized on the magnetic beads by covalent linkage using 1-(3-dimethyl-aminopropyl)-3-ethyl-carbodiimide (EDC) and N-hydroxysuccinimide (NHS) as reaction reagents, respectively. The properties of enzyme conjugated magnetic beads were characterized using transmission electron microscopy, X-ray diffractometer and vibration sample magnetometer. Several factors including pH, ion strength, incubation time and temperature were optimized using three known ligands (caffeic acid, ferulic acid, and hesperidin). The established MT-ASMS approach was applied to screening for ligands from a Chinese medicine "Tang-Zhi-Qing", which was used to treat type II diabetes in China. Seven bound compounds were identified via liquid chromatography-mass spectrometry (LC/MS). Five active compounds including 2,3,4,6-tetra-O-galloyl-D-glucose, 1,2,3,4-tetra-O-galloyl-D-glucose, 1,2,3,4,6-penta-O-galloyl-d-glucose, quercetin-3-O-β-D-glucuronide and quercetin-3-O-β-D-glucoside were identified and their activities were validated by conventional inhibitory assay. Our findings suggested that the proposed approach is efficient in screening compounds with multiple activities from extracts of botanical drugs. PMID:23501439

  6. Magnetic beads-based DNAzyme recognition and AuNPs-based enzymatic catalysis amplification for visual detection of trace uranyl ion in aqueous environment.

    PubMed

    Zhang, Hongyan; Lin, Ling; Zeng, Xiaoxue; Ruan, Yajuan; Wu, Yongning; Lin, Minggui; He, Ye; Fu, FengFu

    2016-04-15

    We herein developed a novel biosensor for the visual detection of trace uranyl ion (UO2(2+)) in aqueous environment with high sensitivity and specificity by using DNAzyme-functionalized magnetic beads (MBs) for UO2(2+) recognition and gold nano-particles (AuNPs)-based enzymatic catalysis oxidation of TMB (3,3',5,5'-tetramethylbenzidine sulfate) for signal generation. The utilization of MBs facilitates the magnetic separation and collection of sensing system from complex sample solution, which leads to more convenient experimental operation and more strong resistibility of the biosensor to the matrix of sample, and the utilization of AuNPs-based enzymatic catalysis amplification greatly improved the sensitivity of the biosensor. Compared with the previous DNAzyme-based UO2(2+) sensors, the proposed biosensor has outstanding advantages such as relative high sensitivity and specificity, operation convenience, low cost and more strong resistibility to the matrix of sample. It can be used to detect as low as 0.02 ppb (74 pM) of UO2(2+) in aqueous environment by only naked-eye observation and 1.89 ppt (7.0 pM) of UO2(2+) by UV-visible spectrophotometer with a recovery of 93-99% and a RSD ≤ 5.0% (n=6) within 3h. Especially, the visual detection limit of 0.02 ppb (74 pM) is much lower than the maximum allowable level of UO2(2+) (130 nM) in the drinking water defined by the U.S. Environmental Protection Agency (EPA), indicating that our method meets the requirement of rapid and on-site detection of UO2(2+) in the aqueous environment by only naked-eye observation. PMID:26594889

  7. Direct numerical simulation of pore-scale flow in a bead pack: Comparison with magnetic resonance imaging observations

    NASA Astrophysics Data System (ADS)

    Yang, Xiaofan; Scheibe, Timothy D.; Richmond, Marshall C.; Perkins, William A.; Vogt, Sarah J.; Codd, Sarah L.; Seymour, Joseph D.; McKinley, Matthew I.

    2013-04-01

    A significant body of current research is aimed at developing methods for numerical simulation of flow and transport in porous media that explicitly resolve complex pore and solid geometries, and at utilizing such models to study the relationships between fundamental pore-scale processes and macroscopic manifestations at larger (i.e., Darcy) scales. A number of different numerical methods for pore-scale simulation have been developed, and have been extensively tested and validated for simplified geometries. However, validation of pore-scale simulations of fluid velocity for complex, three-dimensional (3D) pore geometries that are representative of natural porous media is challenging due to our limited ability to measure pore-scale velocity in such systems. Recent advances in magnetic resonance imaging (MRI) offer the opportunity to measure not only the pore geometry, but also local fluid velocities under steady-state flow conditions in 3D and with high spatial resolution. In this paper, we present a 3D velocity field measured at sub-pore resolution (tens of micrometers) over a centimeter-scale 3D domain using MRI methods. We have utilized the measured pore geometry to perform 3D simulations of Navier-Stokes flow over the same domain using direct numerical simulation techniques. We present a comparison of the numerical simulation results with the measured velocity field. It is shown that the numerical results match the observed velocity patterns well overall except for a variance and small systematic scaling which can be attributed to the known experimental uncertainty in the MRI measurements. The comparisons presented here provide strong validation of the pore-scale simulation methods and new insights for interpretation of uncertainty in MRI measurements of pore-scale velocity. This study also provides a potential benchmark for future comparison of other pore-scale simulation methods. 2012 Elsevier Science.

  8. Direct Numerical Simulation of Pore-Scale Flow in a Bead Pack: Comparison with Magnetic Resonance Imaging Observations

    SciTech Connect

    Yang, Xiaofan; Scheibe, Timothy D.; Richmond, Marshall C.; Perkins, William A.; Vogt, Sarah J.; Codd, Sarah L.; Seymour, Joseph D.; Mckinley, Matthew I.

    2013-04-01

    A significant body of current research is aimed at developing methods for numerical simulation of flow and transport in porous media that explicitly resolve complex pore and solid geometries, and at utilizing such models to study the relationships between fundamental pore-scale processes and macroscopic manifestations at larger (i.e., Darcy) scales. A number of different numerical methods for pore-scale simulation have been developed, and have been extensively tested and validated for simplified geometries. However, validation of pore-scale simulations of fluid velocity for complex, three-dimensional (3D) pore geometries that are representative of natural porous media is challenging due to our limited ability to measure pore-scale velocity in such systems. Recent advances in magnetic resonance imaging (MRI) offer the opportunity to measure not only the pore geometry, but also local fluid velocities under steady-state flow conditions in 3D and with high spatial resolution. In this paper, we present a 3D velocity field measured at sub-pore resolution (tens of micrometers) over a centimeter-scale 3D domain using MRI methods. We have utilized the measured pore geometry to perform 3D simulations of Navier-Stokes flow over the same domain using direct numerical simulation techniques. We present a comparison of the numerical simulation results with the measured velocity field. It is shown that the numerical results match the observed velocity patterns well overall except for a variance and small systematic scaling which can be attributed to the known experimental error in the MRI measurements. The comparisons presented here provide strong validation of the pore-scale simulation methods and new insights for interpretation of uncertainty in MRI measurements of pore-scale velocity. This study also provides a potential benchmark for future comparison of other pore-scale simulation methods.

  9. Chromosome Microarray.

    PubMed

    Anderson, Sharon

    2016-01-01

    Over the last half century, knowledge about genetics, genetic testing, and its complexity has flourished. Completion of the Human Genome Project provided a foundation upon which the accuracy of genetics, genomics, and integration of bioinformatics knowledge and testing has grown exponentially. What is lagging, however, are efforts to reach and engage nurses about this rapidly changing field. The purpose of this article is to familiarize nurses with several frequently ordered genetic tests including chromosomes and fluorescence in situ hybridization followed by a comprehensive review of chromosome microarray. It shares the complexity of microarray including how testing is performed and results analyzed. A case report demonstrates how this technology is applied in clinical practice and reveals benefits and limitations of this scientific and bioinformatics genetic technology. Clinical implications for maternal-child nurses across practice levels are discussed. PMID:27276104

  10. Small, porous polyacrylate beads

    NASA Technical Reports Server (NTRS)

    Rembaum, Alan (Inventor); Yen, Shiao-Ping Siao (Inventor); Dreyer, William J. (Inventor)

    1976-01-01

    Uniformly-shaped, porous, round beads are prepared by the co-polymerization of an acrylic monomer and a cross-linking agent in the presence of 0.05 to 5% by weight of an aqueous soluble polymer such as polyethylene oxide. Cross-linking proceeds at high temperature above about 50.degree.C or at a lower temperature with irradiation. Beads of even shape and even size distribution of less than 2 micron diameter are formed. The beads will find use as adsorbents in chromatography and as markers for studies of cell surface receptors.

  11. Crosslinked, porous, polyacrylate beads

    NASA Technical Reports Server (NTRS)

    Rembaum, Alan (Inventor); Yen, Shiao-Ping Siao (Inventor); Dreyer, William J. (Inventor)

    1976-01-01

    Uniformly-shaped, porous, round beads are prepared by the co-polymerization of an acrylic monomer and a cross-linking agent in the presence of 0.05 to 5% by weight of an aqueous soluble polymer such as polyethylene oxide. Cross-linking proceeds at high temperature above about 50.degree.C or at a lower temperature with irradiation. Beads of even shape and even size distribution of less than 2 micron diameter are formed. The beads will find use as adsorbents in chromatography and as markers for studies of cell surface receptors.

  12. Crosslinked, porous, polyacrylate beads

    NASA Technical Reports Server (NTRS)

    Rembaum, Alan (Inventor); Yen, Shiao-Ping S. (Inventor); Dreyer, William J. (Inventor)

    1977-01-01

    Uniformly-shaped, porous, round beads are prepared by the co-polymerization of an acrylic monomer and a cross-linking agent in the presence of 0.05 to 5% by weight of an aqueous soluble polymer such as polyethylene oxide. Cross-linking proceeds at high temperature above about 50.degree. C or at a lower temperature with irradiation. Beads of even shape and even size distribution of less than 2 micron diameter are formed. The beads will find use as adsorbents in chromatography and as markers for studies of cell surface receptors.

  13. Weak cation exchange magnetic beads coupled with matrix-assisted laser desorption ionization-time of flight-mass spectrometry in screening serum protein markers in osteopenia.

    PubMed

    He, Wei-Tao; Liang, Bo-Cheng; Shi, Zhen-Yu; Li, Xu-Yun; Li, Chun-Wen; Shi, Xiao-Lin

    2016-01-01

    The present study aimed at investigating the weak cation magnetic separation technology and matrix-assisted laser desorption ionization-time of flight-mass spectrometry (MALDI-TOF-MS) in screening serum protein markers of osteopenia from ten postmenopausal women and ten postmenopausal women without osteopenia as control group, to find a new method for screening biomarkers and establishing a diagnostic model for primary type I osteoporosis. Serum samples were collected from postmenopausal women with osteopenia and postmenopausal women with normal bone mass. Proteins were extracted from serum samples by weak cation exchange magnetic beads technology, and mass spectra acquisition was done by MALDI-TOF-MS. The visualization and comparison of data sets, statistical peak evaluation, model recognition, and discovery of biomarker candidates were handled by the proteinchip data analysis system software(ZJU-PDAS). The diagnostic models were established using genetic arithmetic based support vector machine (SVM). The SVM result with the highest Youden Index was selected as the model. Combinatorial Peaks having the highest accuracy in distinguishing different samples were selected as potential biomarker. From the two group serum samples, a total of 133 differential features were selected. Ten features with significant intensity differences were screened. In the pair-wise comparisons, processing of MALDI-TOF spectra resulted in the identification of ten differential features between postmenopausal women with osteopenia and postmenopausal women with normal bone mass. The difference of features by Youden index showed that the highest features had a mass to charge ratio of 1699 and 3038 Da. A diagnosis model was established with these two peaks as the candidate marker, and the specificity of the model is 100 %, the sensitivity was 90 % by leave-one-out cross validation test. The two groups of specimens in SVM results on the scatter plot could be clearly distinguished. The peak

  14. Acupressure Bead in the Eustachian Tube.

    PubMed

    Igarashi, Kazunori; Matsumoto, Yu; Kakigi, Akinobu

    2015-08-01

    In this article, we aim to enlighten practitioners and patients involved with acupressure beads and to contribute to their safer use by reporting a unique case of insidious intrusion of an acupressure bead into the eustachian tube. A metallic object was found in the eustachian tube of a patient while conducting a magnetic resonance imaging (MRI) examination. The object was later confirmed to be an auricular acupressure bead, and was successfully removed by performing a tympanoplasty and a canal wall down mastoidectomy. The bead was assumed to have passed through an existing perforation of the tympanic membrane. According to previously published literature, tympanic membrane perforations exist in ∼1% of the population. Therefore, middle-ear foreign bodies are relatively common occurrences for otolaryngologists. However, metallic objects such as acupressure beads are especially important in the sense that they can cause severe burns during MRI. To avoid potential complications, acupressure-bead practitioners should be aware of the possibility that intrusions through the tympanic membrane could go unnoticed. PMID:26276456

  15. Advancing microarray assembly with acoustic dispensing technology.

    PubMed

    Wong, E Y; Diamond, S L

    2009-01-01

    In the assembly of microarrays and microarray-based chemical assays and enzymatic bioassays, most approaches use pins for contact spotting. Acoustic dispensing is a technology capable of nanoliter transfers by using acoustic energy to eject liquid sample from an open source well. Although typically used for well plate transfers, when applied to microarraying, it avoids the drawbacks of undesired physical contact with the sample; difficulty in assembling multicomponent reactions on a chip by readdressing, a rigid mode of printing that lacks patterning capabilities; and time-consuming wash steps. We demonstrated the utility of acoustic dispensing by delivering human cathepsin L in a drop-on-drop fashion into individual 50-nanoliter, prespotted reaction volumes to activate enzyme reactions at targeted positions on a microarray. We generated variable-sized spots ranging from 200 to 750 microm (and higher) and handled the transfer of fluorescent bead suspensions with increasing source well concentrations of 0.1 to 10 x 10(8) beads/mL in a linear fashion. There are no tips that can clog, and liquid dispensing CVs are generally below 5%. This platform expands the toolbox for generating analytical arrays and meets needs associated with spatially addressed assembly of multicomponent microarrays on the nanoliter scale. PMID:19035650

  16. Automated Immunomagnetic Separation and Microarray Detection of E. coli O157:H7 from Poultry Carcass Rinse

    SciTech Connect

    Chandler, Darrell P. ); Brown, Jeremy D.; Call, Douglas R. ); Wunschel, Sharon C. ); Grate, Jay W. ); Holman, David A.; Olson, Lydia G.; Stottlemyer, Mark S.; Bruckner-Lea, Cindy J. )

    2001-09-01

    We describe the development and application of a novel electromagnetic flow cell and fluidics system for automated immunomagnetic separation of E. coli directly from unprocessed poultry carcass rinse, and the biochemical coupling of automated sample preparation with nucleic acid microarrays without cell growth. Highly porous nickel foam was used as a magnetic flux conductor. Up to 32% recovery efficiency of 'total' E. coli was achieved within the automated system with 6 sec contact times and 15 minute protocol (from sample injection through elution), statistically similar to cell recovery efficiencies in > 1 hour 'batch' captures. The electromagnet flow cell allowed complete recovery of 2.8 mm particles directly from unprocessed poultry carcass rinse whereas the batch system did not. O157:H7 cells were reproducibly isolated directly from unprocessed poultry rinse with 39% recovery efficiency at 103 cells ml-1 inoculum. Direct plating of washed beads showed positive recovery of O 157:H7 directly from carcass rinse at an inoculum of 10 cells ml-1. Recovered beads were used for direct PCR amplification and microarray detection, with a process-level detection limit (automated cell concentration through microarray detection) of < 103 cells ml-1 carcass rinse. The fluidic system and analytical approach described here are generally applicable to most microbial detection problems and applications.

  17. Comprehensive Analysis of DNA Methylation Data with RnBeads

    PubMed Central

    Walter, Jörn; Lengauer, Thomas; Bock, Christoph

    2014-01-01

    RnBeads is a software tool for large-scale analysis and interpretation of DNA methylation data, providing a user-friendly analysis workflow that yields detailed hypertext reports (http://rnbeads.mpi-inf.mpg.de). Supported assays include whole genome bisulfite sequencing, reduced representation bisulfite sequencing, Infinium microarrays, and any other protocol that produces high-resolution DNA methylation data. Important applications of RnBeads include the analysis of epigenome-wide association studies and epigenetic biomarker discovery in cancer cohorts. PMID:25262207

  18. DNA Microarrays

    NASA Astrophysics Data System (ADS)

    Nguyen, C.; Gidrol, X.

    Genomics has revolutionised biological and biomedical research. This revolution was predictable on the basis of its two driving forces: the ever increasing availability of genome sequences and the development of new technology able to exploit them. Up until now, technical limitations meant that molecular biology could only analyse one or two parameters per experiment, providing relatively little information compared with the great complexity of the systems under investigation. This gene by gene approach is inadequate to understand biological systems containing several thousand genes. It is essential to have an overall view of the DNA, RNA, and relevant proteins. A simple inventory of the genome is not sufficient to understand the functions of the genes, or indeed the way that cells and organisms work. For this purpose, functional studies based on whole genomes are needed. Among these new large-scale methods of molecular analysis, DNA microarrays provide a way of studying the genome and the transcriptome. The idea of integrating a large amount of data derived from a support with very small area has led biologists to call these chips, borrowing the term from the microelectronics industry. At the beginning of the 1990s, the development of DNA chips on nylon membranes [1, 2], then on glass [3] and silicon [4] supports, made it possible for the first time to carry out simultaneous measurements of the equilibrium concentration of all the messenger RNA (mRNA) or transcribed RNA in a cell. These microarrays offer a wide range of applications, in both fundamental and clinical research, providing a method for genome-wide characterisation of changes occurring within a cell or tissue, as for example in polymorphism studies, detection of mutations, and quantitative assays of gene copies. With regard to the transcriptome, it provides a way of characterising differentially expressed genes, profiling given biological states, and identifying regulatory channels.

  19. Bead-based microfluidic immunoassay for diagnosis of Johne's disease

    SciTech Connect

    Wadhwa, Ashutosh; Foote, Robert; Shaw, Robert W; Eda, Shigetoshi

    2012-01-01

    Microfluidics technology offers a platform for development of point-of-care diagnostic devices for various infectious diseases. In this study, we examined whether serodiagnosis of Johne s disease (JD) can be conducted in a bead-based microfluidic assay system. Magnetic micro-beads were coated with antigens of the causative agent of JD, Mycobacterium avium subsp. paratuberculosis. The antigen-coated beads were incubated with serum samples of JD-positive or negative serum samples and then with a fluorescently-labeled secondary antibody (SAB). To confirm binding of serum antibodies to the antigen, the beads were subjected to flow cytometric analysis. Different conditions (dilutions of serum and SAB, types of SAB, and types of magnetic beads) were optimized for a great degree of differentiation between the JD-negative and JD-positive samples. Using the optimized conditions, we tested a well-classified set of 155 serum samples from JD negative and JD-positive cattle by using the bead-based flow cytometric assay. Of 105 JD-positive samples, 63 samples (60%) showed higher antibody binding levels than a cut-off value determined by using antibody binding levels of JD-negative samples. In contrast, only 43-49 JD-positive samples showed higher antibody binding levels than the cut-off value when the samples were tested by commercially-available immunoassays. Microfluidic assays were performed by magnetically immobilizing a number of beads within a microchannel of a glass microchip and detecting antibody on the collected beads by laser-induced fluorescence. Antigen-coated magnetic beads treated with bovine serum sample and fluorescently-labeled SAB were loaded into a microchannel to measure the fluorescence (reflecting level of antibody binding) on the beads in the microfluidic system. When the results of five bovine serum samples obtained with the system were compared to those obtained with the flow cytometer, a high level of correlation (linear regression, r2 = 0.994) was

  20. Weld-Bead Shaver

    NASA Technical Reports Server (NTRS)

    Guirguis, Kamal; Price, Daniel S.

    1990-01-01

    Hand-held power tool shaves excess metal from inside circumference of welded duct. Removes excess metal deposited by penetration of tungsten/inert-gas weld or by spatter from electron-beam weld. Produces smooth transition across joint. Easier to use and not prone to overshaving. Also cuts faster, removing 35 in. (89 cm) of weld bead per hour.

  1. Bead-Dazzled Baskets.

    ERIC Educational Resources Information Center

    St. Clair, Sharon

    2002-01-01

    Presents an art lesson used when teaching about North American Indians to fourth- and fifth-grade students. Explains that the students learn how to make baskets using a coil-wrap technique with colored yarns and beads. Provides a step-by-step explanation of how to create the baskets. (CMK)

  2. Aptamer Microarrays

    SciTech Connect

    Angel-Syrett, Heather; Collett, Jim; Ellington, Andrew D.

    2009-01-02

    In vitro selection can yield specific, high-affinity aptamers. We and others have devised methods for the automated selection of aptamers, and have begun to use these reagents for the construction of arrays. Arrayed aptamers have proven to be almost as sensitive as their solution phase counterparts, and when ganged together can provide both specific and general diagnostic signals for proteins and other analytes. We describe here technical details regarding the production and processing of aptamer microarrays, including blocking, washing, drying, and scanning. We will also discuss the challenges involved in developing standardized and reproducible methods for binding and quantitating protein targets. While signals from fluorescent analytes or sandwiches are typically captured, it has proven possible for immobilized aptamers to be uniquely coupled to amplification methods not available to protein reagents, thus allowing for protein-binding signals to be greatly amplified. Into the future, many of the biosensor methods described in this book can potentially be adapted to array formats, thus further expanding the utility of and applications for aptamer arrays.

  3. Coated Aerogel Beads

    NASA Technical Reports Server (NTRS)

    Littman, Howard (Inventor); Plawsky, Joel L. (Inventor); Paccione, John D. (Inventor)

    2014-01-01

    Methods and apparatus for coating particulate material are provided. The apparatus includes a vessel having a top and a bottom, a vertically extending conduit having an inlet in the vessel and an outlet outside of the vessel, a first fluid inlet in the bottom of the vessel for introducing a transfer fluid, a second fluid inlet in the bottom of the vessel for introducing a coating fluid, and a fluid outlet from the vessel. The method includes steps of agitating a material, contacting the material with a coating material, and drying the coating material to produce a coated material. The invention may be adapted to coat aerogel beads, among other materials. A coated aerogel bead and an aerogel-based insulation material are also disclosed.

  4. Microfluidic immunomagnetic multi-target sorting--a model for controlling deflection of paramagnetic beads.

    PubMed

    Tsai, Scott S H; Griffiths, Ian M; Stone, Howard A

    2011-08-01

    We describe a microfluidic system that uses a magnetic field to sort paramagnetic beads by deflecting them in the direction normal to the flow. In the experiments we systematically study the dependence of the beads' deflection on bead size and susceptibility, magnet strength, fluid speed and viscosity, and device geometry. We also develop a design parameter that can aid in the design of microfluidic devices for immunomagnetic multi-target sorting. PMID:21677937

  5. Transport of superparamagnetic beads through a two-dimensional potential energy landscape.

    PubMed

    Tahir, Mukarram A; Gao, Lu; Virgin, Lawrence N; Yellen, Benjamin B

    2011-07-01

    The nonlinear dynamic behavior of superparamagnetic beads transported through a two-dimensional potential energy landscape is explored empirically and through numerical simulation. The beads are driven through a periodic array of micromagnets by an external rotating field oriented at an angle θ relative to the magnetization direction of the substrate. The bead's motion was highly sensitive to the angle of the driving field near critical angles and to various system parameters, including bead size, rotation frequency, and substrate pole density. Our results suggest the possibility of using this behavior in a highly discriminative colloidal separation system, in which two different bead types can be tuned to move in orthogonal directions. PMID:21867167

  6. Basic Concepts of Microarrays and Potential Applications in Clinical Microbiology

    PubMed Central

    Miller, Melissa B.; Tang, Yi-Wei

    2009-01-01

    Summary: The introduction of in vitro nucleic acid amplification techniques, led by real-time PCR, into the clinical microbiology laboratory has transformed the laboratory detection of viruses and select bacterial pathogens. However, the progression of the molecular diagnostic revolution currently relies on the ability to efficiently and accurately offer multiplex detection and characterization for a variety of infectious disease pathogens. Microarray analysis has the capability to offer robust multiplex detection but has just started to enter the diagnostic microbiology laboratory. Multiple microarray platforms exist, including printed double-stranded DNA and oligonucleotide arrays, in situ-synthesized arrays, high-density bead arrays, electronic microarrays, and suspension bead arrays. One aim of this paper is to review microarray technology, highlighting technical differences between them and each platform's advantages and disadvantages. Although the use of microarrays to generate gene expression data has become routine, applications pertinent to clinical microbiology continue to rapidly expand. This review highlights uses of microarray technology that impact diagnostic microbiology, including the detection and identification of pathogens, determination of antimicrobial resistance, epidemiological strain typing, and analysis of microbial infections using host genomic expression and polymorphism profiles. PMID:19822891

  7. Microarrays, Integrated Analytical Systems

    NASA Astrophysics Data System (ADS)

    Combinatorial chemistry is used to find materials that form sensor microarrays. This book discusses the fundamentals, and then proceeds to the many applications of microarrays, from measuring gene expression (DNA microarrays) to protein-protein interactions, peptide chemistry, carbodhydrate chemistry, electrochemical detection, and microfluidics.

  8. A superparamagnetic bead driven fluidic device (Invited Paper)

    NASA Astrophysics Data System (ADS)

    Husband, Benjamin; Melvin, Tracy; Evans, Alan G. R.

    2005-07-01

    Injection strategies have been employed in the field of fluidic MEMS using piezo electric or thermal actuators. A very popular application for such technology is inkjet printing. Largely this technology is used to produce droplets of fluid in air; the aim of this investigation is to produce an injection device for the precise dispensing of nanolitre volumes of fluid. A novel technique for dispensing fluid using superparamagnetic beads has been investigated. The beads used (Dynal Biotech) contain a homogeneous dispersion of Fe2O3, allowing for easy control with a magnet. This magnetic property is exploited, by a plug of approximately 60 000 beads within a micro channel. This is accomplished by applying a non-uniform magnetic field from a bullet magnet within close proximity of the bead plug. Once the plug is formed it can be moved along the micro channel by moving the magnet and thus, provide a plunger-like action. Previous work has demonstrated a bead plug device is able to dispense fluid from a micro channel at rates up to 7.2μlmin-1. This is an investigation using silicon and Pyrex fabricated micro channels with smaller dimensions, such that the dimensions will be similar to those which will be used to produce a pipette device. Here results are presented using these fabricated micro channels, where the effects of using differently sized bead plugs and varying velocities are examined. The results follow our proposed theory; further analysis is required to determine the operation of a bead plug during all states of movement.

  9. Single bead detection with an NMR microcapillary probe

    NASA Astrophysics Data System (ADS)

    Nakashima, Yoshihiro; Boss, Michael; Russek, Stephen E.; Moreland, John

    2012-11-01

    We have developed a nuclear magnetic resonance (NMR) microcapillary probe for the detection of single magnetic microbeads. The geometry of the probe has been optimized so that the signal from the background water has a similar magnitude compared to the signal from the dephased water nearby a single magnetic bead within the probe detector coil. In addition, the RF field of the coil must be uniform within the effective range of the magnetic bead. Three different RF probes were tested in a 7 T (300 MHz) pulsed NMR spectrometer with sample volumes ranging from 5 nL down to 1 nL. The 1 nL probe had a single-shot signal-to-noise ratio (SNR) for pure water of 27 and a volume resolution that exhibits a 600-fold improvement over a conventional (5 mm tube) NMR probe with a sample volume of 18 μL. This allowed for the detection of a 1 μm magnetite/polystyrene bead (m = 2 × 10-14 A m2) with an estimated experimental SNR of 30. Simulations of the NMR spectra for the different coil geometries and positions of the bead within the coil were developed that include the B0 shift near a single bead, the inhomogeneity of the coils, the local coil sensitivity, the skin effect of the coil conductor, and quantitated estimates of the proximity effect between coil windings.

  10. Magnetic Beads Enhance Adhesion of NIH 3T3 Fibroblasts: A Proof-of-Principle In Vitro Study for Implant-Mediated Long-Term Drug Delivery to the Inner Ear

    PubMed Central

    Aliuos, Pooyan; Schulze, Jennifer; Schomaker, Markus; Reuter, Günter; Stolle, Stefan R. O.; Werner, Darja; Ripken, Tammo; Lenarz, Thomas; Warnecke, Athanasia

    2016-01-01

    Introduction Long-term drug delivery to the inner ear may be achieved by functionalizing cochlear implant (CI) electrodes with cells providing neuroprotective factors. However, effective strategies in order to coat implant surfaces with cells need to be developed. Our vision is to make benefit of electromagnetic field attracting forces generated by CI electrodes to bind BDNF-secreting cells that are labelled with magnetic beads (MB) onto the electrode surfaces. Thus, the effect of MB-labelling on cell viability and BDNF production were investigated. Materials and Methods Murine NIH 3T3 fibroblasts—genetically modified to produce BDNF—were labelled with MB. Results Atomic force and bright field microscopy illustrated the internalization of MB by fibroblasts after 24 h of cultivation. Labelling cells with MB did not expose cytotoxic effects on fibroblasts and allowed adhesion on magnetic surfaces with sufficient BDNF release. Discussion Our data demonstrate a novel approach for mediating enhanced long-term adhesion of BDNF-secreting fibroblasts on model electrode surfaces for cell-based drug delivery applications in vitro and in vivo. This therapeutic strategy, once transferred to cells suitable for clinical application, may allow the biological modifications of CI surfaces with cells releasing neurotrophic or other factors of interest. PMID:26918945