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Magnetic Separation (magnetic + separation)
Selected AbstractsDNA Hybridization at Magnetic Nanoparticles with Electrochemical Stripping DetectionELECTROANALYSIS, Issue 23 2004Ningning Zhu Abstract A simple and practical method for electrochemical DNA hybridization assay has been developed to take advantage of magnetic nanoparticles for ssDNA immobilization and zinc sulfide nanoparticle as oligonucleotide label. Magnetic nanoparticles were prepared by coprecipitation of Fe2+ and Fe3+ with NH4OH, and then amino silane was coated onto the surface of magnetite nanoparticles. The magnetic nanoparticles have the advantages of easy preparation, easy surface modification and low cost. The target ssDNA with the phosphate group at the 5, end was then covalently immobilized to the amino group of magnetite nanoparticles by forming a phosphoramidate bond in the presence of 1-ethyl-3-(3-dimeth-ylaminopropyl)carbodiimide (EDAC). The zinc sulfide (ZnS) nanoparticle-labeled oligonucleotides probe was used to identify the target ssDNA immobilized on the magnetic nanoparticles based on a specific hybridization reaction. The hybridization events were assessed by the dissolution of the zinc sulfide nanoparticles anchored on the hybrids and the indirect determination of the dissolved zinc ions by anodic stripping voltammetry (ASV) at a mercury film glassy carbon electrode (GCE). The proposed method couples the high sensitivity of anodic stripping analysis for zinc ions with effective magnetic separation for eliminating nonspecific adsorption effects and offers great promise for DNA hybridization analysis. [source] Functional characterization of highly adherent CD34+ keratinocytes isolated from human skinEXPERIMENTAL DERMATOLOGY, Issue 7 2010Araika Gutiérrez-Rivera Please cite this paper as: Functional characterization of highly adherent CD34+ keratinocytes isolated from human skin. Experimental Dermatology 2010; 19: 685,688. Abstract:, Compared to murine models, data on cells responsible for the homeostasis of human epidermis are scarce and often contradictory. Given the conflicting results and the availability of clinical grade protocols to purify CD34 cells from a given tissue, we pursued to phenotypically characterize human epidermal CD34+ population. After magnetic separation of whole skin CD34+ and CD34, cell fractions and selection for cells highly adherent to extracellular matrix, both CD34± fractions retained the ability to form a stratified epidermis in organotypic cultures and presented similar in vitro migratory phenotypes. However CD34, cells showed higher clonogenic potential and in vitro proliferative capacity. These results indicated that CD34, cell fraction contains stem/early progenitor cells, while CD34+ cells might be a transit-amplifying precursor for hair follicle (HF) sheath cells. The ability to isolate living cells using differential cell adhesion and surface markers provides an opportunity to study cells from different morphological regions of the HF. [source] Functionalization Strategies for Protease Immobilization on Magnetic NanoparticlesADVANCED FUNCTIONAL MATERIALS, Issue 11 2010Dan Li Abstract A comprehensive study on the general functionalization strategies for magnetic nanoparticles (MNPs) is presented in this work. Using well-established techniques as well as modified protocols, the wide range of functional moieties grafted on ,-Fe2O3 (maghemite) nanosurfaces include those of amine, aldehyde, carboxylic, epoxy, mercapto, and maleimide ends. Among the modified protocols are the one-step water-catalyzed silanization with mercaptopropyltrimethoxysilane, resulting in dense distal thiols, and the direct functionalization with a heterogeneous bifunctional linker N -[p-maleimidophenyl]isocynanate (PMPI). The former results in a protective Stöber type coating while simultaneously reducing the iron oxide core to magnetite (Fe3O4). The conjugation of trypsin, hereby chosen as model biomolecule, onto the differently functionalized MNPs is further demonstrated and assessed based on its activity, kinetics, and thermo-/long-term stability as well as reusability. Besides aqueous stability and ease in recovery by magnetic separation, the immobilized trypsin on MNPs offers superior protease durability and reusability, without compromising the substrate specificity and sequence coverage of free trypsin. The MNP-based proteases can be used as valuable carriers in proteomics and miniaturized total analysis devices. The applicability of the functional surfaces devised in the current study is also relevant for the conjugation of other biomolecules beyond trypsin. [source] Segmented filamentous bacteria in a defined bacterial cocktail induce intestinal inflammation in SCID mice reconstituted with CD45RBhigh CD4+ T cellsINFLAMMATORY BOWEL DISEASES, Issue 10 2007Renata Stepankova PhD Abstract Background: The aim was to analyze the influence of intestinal microbiota on the development of intestinal inflammation. We used the model of chronic inflammation that develops spontaneously in the colon of conventional severe combined immunodeficiency (SCID) mice restored with the CD45 RBhigh subset of CD4+T cells isolated from the spleen of normal BALB/c mice. Methods: A CD4+CD45RBhigh subpopulation of T cells was purified from the spleen of conventional BALB/c mice by magnetic separation (MACS) and transferred into immunodeficient SCID mice. Germ-free (GF) SCID mice or SCID mice monoassociated with Enterococcus faecalis, SFB (segmented filamentous bacteria), Fusobacterium mortiferum, Bacteroides distasonis, and in combination Fusobacterium mortiferum + SFB or Bacteroides distasonis + SFB were used as recipients. SCID mice were colonized by a defined cocktail of specific pathogen-free (SPF) bacteria. Mice were evaluated 8,12 weeks after the cell transfer for clinical and morphological signs of inflammatory bowel disease (IBD). Results: After the transfer of the CD4+CD45RBhigh T-cell subpopulation to SCID mice severe colitis was present in conventional animals and in mice colonized with a cocktail of SPF microflora plus SFB. Altered intestinal barrier in the terminal ileum of mice with severe colitis was documented by immunohistology using antibodies to ZO-1 (zona occludens). Conclusions: Only SFB bacteria together with a defined SPF mixture were effective in triggering intestinal inflammation in the model of IBD in reconstituted SCID mice, while no colitis was detected in GF mice or in mice colonized either with SPF microflora or monoassociated only with SFB or colonized by Bacteroides distasonis + SFB or Fusobacterium mortiferum + SFB. (Inflamm Bowel Dis 2007) [source] Surface Structure of Converter Slag Stabilized by HeatingJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 1 2007Naomitsu Tsuyuki Converter slag contains free lime (CaO) and unstable iron oxides (FeO, FeOOH) that may lead to expansive self-destruction. A typical industry practice for converter slag has been stabilization by steam curing and autoclaving; however, the stabilization can only reach the surface, and not the inside, of slag particles. A new method is proposed in this study to stabilize the converter slag by heating at a low temperature. After magnetic separation, specimens of converter slag were subjected to heating for 2 h at a temperature of 500°C, resulting in a decrease of free lime content irrespective of the particle size. This effect was attributed to the formation of Ca2Fe9O13 and complicated apatite groups owing to the heating. The iron oxides in the converter slag were analyzed by X-ray photoelectron spectra. It was found that after heating, the unstable FeO (wustite) content decreased and an oxidized ,-Fe2O3 (hematite) increased. This led to the prevention of the iron-induced expansion. The rate of heat liberation by the free lime in converter slag was smaller than that of the reagent CaO. This suggests that the presumed free lime is in a different form based on the Ca bond energy in the surface of slag particles. [source] Ultrasonically initiated miniemulsion polymerization of styrene in the presence of Fe3O4 nanoparticlesPOLYMER INTERNATIONAL, Issue 3 2006Guihua Qiu Abstract Ultrasonically initiated miniemulsion polymerization of styrene was conducted in the presence of Fe3O4 nanoparticles. Stable polystyrene (PS)/Fe3O4 nanocomposite emulsions were prepared and magnetic PS/Fe3O4 composite particles were obtained through magnetic separation. The whole procedure comprised two steps. First, Fe3O4 nanoparticles were dispersed in the monomer phase with the aid of stabilizer Span-80. Second, miniemulsion polymerization of styrene in the presence of Fe3O4 nanoparticles was carried out under an ultrasonic field in the absence of a chemical initiator. The affecting factors, including stabilizer concentration, surfactant concentration, hexadecane concentration and the amount of Fe3O4, were systematically studied. Stabilizer concentration, surfactant concentration and hexadecane concentration strongly affected the formation of the coagulation. The least amount of coagulation was formed at 2.5 wt% Span-80 concentration. The addition of Fe3O4 nanoparticles drastically increased the polymerization rate owing to the fact that Fe3O4 nanoparticles increased the acoustic intensity and Fe2+ reacted with H2O2 to produce hydroxyl radicals and increase the number of radicals. The increase in cosurfactant concentration and power output also increased the polymerization rate. Copyright © 2005 Society of Chemical Industry [source] In situ magnetic separation for extracellular protein productionBIOTECHNOLOGY & BIOENGINEERING, Issue 2 2009Tobias Käppler Abstract A new approach for in situ product removal from bioreactors is presented in which high-gradient magnetic separation is used. This separation process was used for the adsorptive removal of proteases secreted by Bacillus licheniformis. Small, non-porous bacitracin linked magnetic adsorbents were employed directly in the broth during the fermentation, followed by in situ magnetic separation. Proof of the concept was first demonstrated in shake flask culture, then scaled up and applied during a fed batch cultivation in a 3.7 L bioreactor. It could be demonstrated that growth of B. licheniformis was not influenced by the in situ product removal step. Protease production also remained the same after the separation step. Furthermore, degradation of the protease, which followed first order kinetics, was reduced by using the method. Using a theoretical modeling approach, we could show that protease yield in total was enhanced by using in situ magnetic separation. The process described here is a promising technique to improve overall yield in bio production processes which are often limited due to weak downstream operations. Potential limitations encountered during a bioprocess can be overcome such as product inhibition or degradation. We also discuss the key points where research is needed to implement in situ magnetic separation in industrial production. Biotechnol. Bioeng. 2009;102: 535,545. © 2008 Wiley Periodicals, Inc. [source] Influence of different magnetites on properties of magnetic Pseudomonas aeruginosa immobilizates used for biosurfactant productionBIOTECHNOLOGY PROGRESS, Issue 6 2009M. Heyd Abstract During the last decades, whole-cell immobilization has been used successfully in many bioprocesses. In particular, it is aimed at implementing continuous production processes, reaching higher production rates, and reusing the biocatalyst. In some cases, effective retention of immobilizates in the bioprocess is not feasible by membranes or sieves due to pore plugging or undesired losses of immobilizates. In the present publication, it is reported about the investigation of magnetic immobilizates of Pseudomonas aeruginosa for application in continuous biosurfactant production of rhamnolipids by foam fractionation and retention of entrained immobilizates by high-gradient magnetic separation from foam. Different materials and methods were tested with respect to important parameters, such as stability, diffusion properties or magnetic separation. Good magnetic separation of immobilizates was achieved at 5% (w/w) magnetite loading. Best results in terms of homogeneous embedding, good diffusion properties, and stability enhancement vis-à-vis pure alginate beads was achieved with alginate beads with embedded Bayoxide® magnetite or MagPrep® silica particles. Although polyurethane immobilizates showed higher stabilities compared with alginate beads, rhamnolipid diffusion in immobilizates was superior in magnetic alginate beads. Regarding bead production, smaller immobilizates were achieved with suspension polymerization compared to droplet extrusion by the JetCutting® technology. In total, magnetic immobilizates are a promising tool for an easier handling of biocatalysts in a continuous biological production process, but they have to be adapted to the current production task.© 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2009 [source] The efficient and specific isolation of the antibodies from human serum by thiophilic paramagnetic polymer nanospheresBIOTECHNOLOGY PROGRESS, Issue 2 2009Hao Qian Abstract A rapid and effective method to specifically isolate the antibodies from human serum was presented based on the fast magnetic separation and specific adsorption of the novel thiophilic magnetic polymer nanospheres, which were synthesized by using miniemulsion copolymerization. After the thiophilic heterocyclic ligands of 2-mercaptonicotinic acid were first activated via divinyl sulfone, they were immobilized on the surface of these magnetic nanospheres, through which the strong specificity to immunoglobulin G was evidently expressed in the isolation of antibodies from human serum. The mild conditions used in the process, including the physiological pH range, low temperature, and low ion strength, were so favorable for keeping the biological activity of antibodies, which resulted in their bioactivity purity to exceed 99%. The efficient isolation, simplicity process, mild conditions, and the conventional equipments required make this technology so attractive to purify antibodies from human serum. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2009 [source] Characteristics of Immobilized Lipase on Hydrophobic Superparamagnetic Microspheres To Catalyze EsterificationBIOTECHNOLOGY PROGRESS, Issue 2 2004Zheng Guo A novel immobilized lipase (from Candida rugosa) on hydrophobic and superparamagnetic microspheres was prepared and used as a biocatalyst to catalyze esterification reactions in diverse solvents and reaction systems. The results showed that the immobilized lipase had over 2-fold higher activities in higher log P value solvents. An exponential increase of lipase activity against log P of two miscible solvent mixtures was observed for the first time. Both free and immobilized lipase achieved its maximum activity at the range of water activity ( aw) 0.5,0.8 or higher. At aw 0.6, the immobilized lipase exhibited markedly higher activities in heptane and a solvent-free system than did the native lipase. In multicompetitive reactions, the alcohol specificity of the lipase showed a strong chain-length dependency, and the immobilized enzyme exhibited more preference for a longer-chain alcohol, which is different from previous reports. The immobilized lipase showed higher specificities for butyric acid and the medium-chain-length fatty acids (C8,C12). Then, the immobilized lipase was extended to solvent-free synthesis of glycerides from glycerol and fatty acids. Recovered by magnetic separation, the immobilized lipase exhibited good reusability in repeated batch reaction, indicating its promising feature for biotechnology application. [source] A Novel Magnetic Affinity Support for Protein Adsorption and PurificationBIOTECHNOLOGY PROGRESS, Issue 1 2001Xiao-Dong Tong A novel magnetic support was prepared by an oxidization-precipitation method with poly(vinyl alcohol) (PVA) as the entrapment material. Transmission electron microscopy indicated that the magnetic particles had a core-shell structure, containing many nanometer-sized magnetic cores stabilized by the cross-linked PVA. The particles showed a high magnetic responsiveness in magnetic field, and no aggregation of the particles was observed after the particles had been treated in the magnetic field. These facts indicated that the particles were superparamagnetic. Cibacron blue 3GA (CB) was coupled to the particles to prepare a magnetic affinity support (MAS) for protein adsorption. Lysozyme was used as a model protein to test the adsorption properties of the MAS. The adsorption equilibrium of lysozyme to the MAS was described by the Langmuir-type isotherm. The capacity for lysozyme adsorption was more than 70 mg/g MAS (wet weight) at a relatively low CB coupling density (3,5 ,mol/g). In addition, 1.0 M NaCl solution could be used to dissociate the adsorbed lysozyme. Finally, the MAS was recycled for the purification of alcohol dehydrogenase (ADH) from clarified yeast homogenates. Under proper conditions, the magnetic separation yielded over 5-fold purification of the enzyme with 60% recovery of the enzyme activity. [source] Efficiency Optimization and Prediction in High-Gradient Magnetic CentrifugationCHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 8 2010J. Lindner Abstract In order to separate small magnetizable particles down to the micro- and nanometer scale, high-gradient magnetic separation is a well-established process. The superposition of magnetic filtration with centrifugation, called magnetic field-enhanced centrifugation, permits continuous separation. The separation efficiency of magnetic filters and the prediction of the efficiency is described. The separation efficiency of one single stage could be enhanced from 51 to 78,% by increasing the wire number and improving the wire cross section. The separation efficiency on different particle sizes at different filter stage numbers and comparison to the prediction of separation efficiency based on magnetic forces and the fluid drag force is demonstrated. [source] Organic,Inorganic Hybrid Polymer-Encapsulated Magnetic Nanobead CatalystsCHEMISTRY - A EUROPEAN JOURNAL, Issue 3 2008Takayoshi Arai Prof. Abstract A new strategy for the encapsulation of magnetic nanobeads was developed by using the in situ self-assembly of an organic,inorganic hybrid polymer. The hybrid polymer of {[Cu(bpy)(BF4)2(H2O)2](bpy)}n (bpy=4,4,-bipyridine) was constructed on the surface of amino-functionalized magnetic beads and the resulting hybrid-polymer-encapsulated beads were utilized as catalysts for the oxidation of silyl enolates to provide the corresponding ,-hydroxy carbonyl compounds in high yield. After the completion of the reaction, the catalyst was readily recovered by magnetic separation and the recovered catalyst could be reused several times. Because the current method did not require complicated procedures for incorporating the catalyst onto the magnetic beads, the preparation and the application of various other types of organic,inorganic hybrid-polymer-coated magnetic beads could be possible. [source] | |||||||||||||||||||