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Magnetic Nanoparticles (magnetic + nanoparticle)
Kinds of Magnetic Nanoparticles Selected AbstractsChemInform Abstract: Immobilization of Dipyridyl Complex to Magnetic Nanoparticle via Click Chemistry as a Recyclable Catalyst for Suzuki Cross-Coupling Reactions.CHEMINFORM, Issue 40 2008Guanghua Lv Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] DNA 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] Monodisperse magnetic nanoparticles for biomedical applicationsPOLYMER INTERNATIONAL, Issue 7 2007Chenjie Xu Abstract Magnetic nanoparticles that are superparamagnetic with high saturation moment have great potential for biomedical applications. Solution-phase syntheses have recently been applied to make various kinds of monodisperse magnetic nanoparticles with standard deviation in diameter of less than 10%. However, the surface of these nanoparticles is coated with a layer of hydrocarbon molecules due to the use of lipid-like carboxylic acid and amine in the syntheses. Surface functionalization leads to the formation of water-soluble nanoparticles that can be further modified with various biomolecules. Such functionalization has brought about several series of monodisperse magnetic nanoparticle systems that have shown promising applications in protein or DNA separation, detection and magnetic resonance imaging contrast enhancement. The goal of this mini review is to summarize the recent progress in the synthesis and surface modification of monodisperse magnetic nanoparticles and their applications in biomedicine. Copyright © 2007 Society of Chemical Industry [source] Magnetic-Field-Induced Locomotion of Glass Fibers on Water Surfaces: Towards the Understanding of How Much Force One Magnetic Nanoparticle Can DeliverADVANCED MATERIALS, Issue 19 2009Feng Shi The amount of force one magnetic nanoparticle (MNPs) can deliver is calculated using Fe3O4 MNPs building blocks to modify glass fibers. Our results demonstrate that one weight unit of Fe3O4 MNPs can eventually drag ,10,000 times its own weight on a water surface, a significant finding for the development of new magnetic delivery systems and micromanipulators. [source] Proposing magnetic nanoparticle hyperthermia in low-field MRICONCEPTS IN MAGNETIC RESONANCE, Issue 1 2010Pádraig Cantillon-Murphy Abstract This work examines feasibility, practical advantages, and disadvantages of a combined MRI/magnetic particle hyperthermia (MPH) system for cancerous tumor treatment in low perfusion tissue. Although combined MRI/hyperthermia systems have been proposed and constructed, the current proposal differs because the hyperthermia system would be specifically designed to interact with the magnetic nanoparticles injected at the tumor site. The proposal exploits the physical similarities between the magnetic nanoparticles currently employed for MPH and those used as superparamagnetic iron oxide (SPIO) contrast agents in MR imaging. The proposal involves the addition of a rotating magnetic field RF hyperthermia source perpendicular to the MRI B0 field which operates in a similar manner to the MRI RF excitation field, B1, but at significantly higher frequency and field strength such that the magnetic nanoparticles are forced to rotate in its presence. This rotation is the source of increases in temperature which are of therapeutic benefit in cancer therapy. For rotating magnetic fields with amplitudes much smaller than B0, the nanoparticles' suspension magnetization rapidly saturates with increasing B0. Therefore, the proposal is best suited to low-field MRI systems when magnetic saturation is incomplete. In addition, careful design of the RF hyperthermia source is required to ensure no physical or RF interference with the B1 field used for MRI excitation. Notwithstanding these caveats, the authors have shown that localized steady-state temperature rises in small spherical tumors of up to 10°C are conceivable with careful selection of the nanoparticle radius and concentration, RF hyperthermia field amplitude and frequency. © 2010 Wiley Periodicals, Inc. Concepts Magn Reson Part A 36A: 36,47, 2010. [source] CMR 2005: 1.03: Analysis of hepatic uptake of anionic magnetic nanoparticlesCONTRAST MEDIA & MOLECULAR IMAGING, Issue 2 2006E. Lee [source] DNA 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] Cover Picture: Electrophoresis 16'2010ELECTROPHORESIS, Issue 16 2010Article first published online: 19 AUG 2010 Issue no. 16 is a regular issue with an Emphasis on "Proteins and Proteomics" comprising 20 manuscripts distributed over 4 separate parts. Part I has 7 research articles on various aspects of proteins and proteomics including combinatorial peptide ligand library for accessing low abundance proteins, analysis of membrane proteins, proteomic profiling of human colon cancer cells, quantitative determinations of biomarkers in clinical diagnostics, recombinant factor VIII, analysis of E. coli soluble proteins, and a weakly basic amino-reactive fluorescent label for IEF of proteins and chip electrophoresis. Part II has 2 research articles dealing with the CE analysis of magnetic nanoparticles and a microfluidic magnetic bead impact for cell stimulation. Part III consists of 2 research articles dealing with on-line preconcentration in CE. Instrumentation, devices and various methodologies are described in 9 research articles, which make the content of Part IV. Featured articles include: Combinatorial peptide ligand library plasma treatment: Advantages for accessing low-abundance proteins ((doi: 10.1002/elps.201000188)) Precautions to improve the accuracy of quantitative determinations of biomarkers in clinical diagnostics ((doi: 10.1002/elps.201000243)) Rapid identification of Candida albicans in blood by combined capillary electrophoresis and fluorescence in situ hybridization ((doi: 10.1002/elps.201000138)) [source] Facile Functionalization and Phase Reduction Route of Magnetic Iron Oxide Nanoparticles for Conjugation of Matrix Metalloproteinase,ADVANCED ENGINEERING MATERIALS, Issue 6 2010Dan Li Abstract A protocol for the simultaneous functionalization and phase reduction route of iron oxide magnetic nanoparticles (MNPs) and its further bioconjugation is presented. It was found that surface functionalization of maghemite (,-Fe2O3) nanoparticles with mercaptopropyltrimethoxysilane (MPTMS) under anoxic environment at above 80,°C promotes in situ conversion to magnetite (Fe3O4). Full conversion to Fe3O4, as probed by Mössbauer spectroscopy, with accompanied increase in the composite saturation magnetization, was achieved at 120,°C. By controlling the MPTMS concentration, the resultant silane-MNPs morphology can be tuned from having homogeneous thin layer (<1,nm) to thick continuous silane with embedded MNP multicores. Likewise the amount of surface distal thiol moieties was dependent on the silanization conditions. The density of distal thiols (i.e., amount of thiol per surface area) and resultant aggregate size have direct impact on the attachment, as well as the activity and reusability of the conjugated matrix metalloproteinase (MMP-2, using sulfo-SMCC as crosslinker). The work has important implication to the field of magneto-chemotherapeutics, where spatial control of conjugated active biomolecules under magnetic field and T2 -weighted MRI contrast can be achieved simultaneously. [source] Cytotoxicity and Cell Cycle Effects of Bare and Poly(vinyl alcohol)-Coated Iron Oxide Nanoparticles in Mouse FibroblastsADVANCED ENGINEERING MATERIALS, Issue 12 2009Morteza Mahmoudi Super-paramagnetic iron oxide nanoparticles (SPIONs) are recognized as powerful biocompatible materials for use in various biomedical applications, such as drug delivery, magnetic-resonance imaging, cell/protein separation, hyperthermia and transfection. This study investigates the impact of high concentrations of SPIONs on cytotoxicity and cell-cycle effects. The interactions of surface-saturated (via interactions with cell medium) bare SPIONs and those coated with poly(vinyl alcohol) (PVA) with adhesive mouse fibroblast cells (L929) are investigated using an MTT assay. The two SPION formulations are synthesized using a co-precipitation method. The bare and coated magnetic nanoparticles with passivated surfaces both result in changes in cell morphology, possibly due to clustering through their magnetostatic effect. At concentrations ranging up to 80,×,10,3,M, cells exposed to the PVA-coated nanoparticles demonstrate high cell viability without necrosis and apoptosis. In contrast, significant apoptosis is observed in cells exposed to bare SPIONs at a concentration of 80,×,10,3,M. Nanoparticle exposure (20,80,×,10,3,M) leads to variations in both apoptosis and cell cycle, possibly due to irreversible DNA damage and repair of oxidative DNA lesions, respectively. Additionally, the formation of vacuoles within the cells and granular cells indicates autophagy cell death rather than either apoptosis or necrosis. [source] Synthesis and Characterization of Thrombin Conjugated ,-Fe2O3 Magnetic Nanoparticles for HemostasisADVANCED ENGINEERING MATERIALS, Issue 12 2009Ofra Ziv Abstract Thrombin is the final protease produced in the clotting pathways. Thrombin has been used in the clinic more than six decades for topical hemostasis and wound management. In human plasma the half-life of thrombin is shorter than 15 seconds due to close control by inhibitors. In order to stabilize thrombin, this enzyme was conjugated covalently and physically to ,-Fe2O3 magnetic nanoparticles. The physical conjugation was accomplished through adsorption of thrombin to BSA coating on the nanoparticles. The coagulant activity of the covalently bound thrombin was significantly lower than that of the physically adsorbed thrombin. Leakage of the physically bound thrombin into PBS containing 4% HSA was negligible. The physical conjugation of thrombin onto the nanoparticles stabilized the thrombin against its major inhibitor antithrombin III and improved its storage stability. At optimal CaCl2 concentration, the clotting time by the bound thrombin is shorter than that of the free enzyme. This novel conjugated thrombin may be an efficient candidate for topical hemostasis and wound healing. [source] Mesoporous Systems for the Preparation of Ordered Magnetic Nanowire Arrays,ADVANCED ENGINEERING MATERIALS, Issue 4 2005A. Eliseev Some tendencies in data storage technologies based on magnetic nanostructures are discussed and a novel approach to anisotropic magnetic nanoparticles which can be used as an active components of magnetic storage media is proposed by the authors [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] Multifunctional Magnetic Optical Sensor Particles with Tunable Sizes for Monitoring Metabolic Parameters and as a Basis for NanotherapeuticsADVANCED FUNCTIONAL MATERIALS, Issue 11 2010Günter Mistlberger Abstract Magnetic optical sensor particles with multifunctional cores and shells are synthesized via a facile nanoprecipitation method and the subsequent modification of the particle shell. The hydrophobic particle core includes optical oxygen indicators, a light harvesting system, photosensitizers, and magnetic nanoparticles. Further functionalities are introduced by modifying the shell with enzymes, antibodies, multiple layers of polyelectrolytes, stimuli-responsive polymers, and luminescent indicator dyes. The hydrodynamic diameter is tunable by varying different precipitation parameters. [source] Designed Multifunctional Nanocomposites for Biomedical ApplicationsADVANCED FUNCTIONAL MATERIALS, Issue 10 2010Humphrey H. P. Yiu Abstract The assembly of multifunctional nanocomposite materials is demonstrated by exploiting the molecular sieving property of SBA-16 nanoporous silica and using it as a template material. The cages of the pore networks are used to host iron oxide magnetic nanoparticles, leaving a pore volume of 0.29,cm3,g,1 accessible for drug storage. This iron oxide,silica nanocomposite is then functionalized with amine groups. Finally the outside of the particle is decorated with antibodies. Since the size of many protein molecules, including that of antibodies, is too large to enter the pore system of SBA-16, the amine groups inside the pores are preserved for drug binding. This is proven using a fluorescent protein, fluorescein-isothiocyanate-labeled bovine serum albumin (FITC-BSA), with the unreacted amine groups inside the pores dyed with rhodamine B isothiocyanate (RITC). The resulting nanocomposite material offers a dual-targeting drug delivery mechanism, i.e., magnetic and antibody-targeting, while the functionalization approach is extendable to other applications, e.g., fluorescence,magnetic dual-imaging diagnosis. [source] Integrated Multifunctional Nanosystems for Medical Diagnosis and TreatmentADVANCED FUNCTIONAL MATERIALS, Issue 21 2009*Article first published online: 9 OCT 200, Donglu Shi Abstract This article provides an overview on the development of integrated multifunctional nanosystems for medical diagnosis and treatment. In particular, a novel system is developed specifically for achieving simultaneous diagnosis and treatment of cancer. Critical issues are addressed on the architecture and assembly of nanocomponents based on medical requirements: targeted in vivo imaging, controlled drug release, localized hyperthermia, and toxicity. Nanotube-based carriers are summarized with surface functionalized properties. Other types of nanocarriers are also included such as super paramagnetic composite nanospheres and biodegradable hydroxylapatite nanoparticles. In addition, polymeric-based nanosystems are introduced with several novel features: they can be bio-dissolved due to environmental pH and temperature fluctuations. The nanocarriers are surface tailored with key functionalities: surface antibodies for cell targeting, anti-cancer drug loading, and magnetic nanoparticles for both hyperthermia and MRI. Future requirements, aims, and trends in the development of multifunctional nanosystems, particularly with intelligent functionalities for fundamental studies, are also provided. [source] Rheological properties of magnetic fluids and their microstructural backgroundGAMM - MITTEILUNGEN, Issue 1 2007S. Odenbach Abstract Beyond the changes exerted by magnetic fields on the flows and properties of suspensions of magnetic nanoparticles, the change of their viscous behavior attracts ongoing research interest since nearly four decades. Within this contribution we'll review the general rheological features of ferrofluids and will present theoretical explanations on microstructural basis providing an insight in the mechanisms leading to a magnetic field dependence of ferrofluid's rheology. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Facile Fabrication and Superparamagnetism of Silica-Shielded Magnetite Nanoparticles on Carbon Nitride NanotubesADVANCED FUNCTIONAL MATERIALS, Issue 14 2009Jung Woo Lee Abstract Using conventional methods to synthesize magnetic nanoparticles (NPs) with uniform size is a challenging task. Moreover, the degradation of magnetic NPs is an obstacle to practical applications. The fabrication of silica-shielded magnetite NPs on carbon nitride nanotubes (CNNTs) provides a possible route to overcome these problems. While the nitrogen atoms of CNNTs provide selective nucleation sites for NPs of a particular size, the silica layer protects the NPs from oxidation. The morphology and crystal structure of NP,CNNT hybrid material is investigated by transmission electron microscopy (TEM) and X-ray diffraction. In addition, the atomic nature of the N atoms in the NP,CNNT system is studied by near-edge X-ray absorption fine structure spectroscopy (nitrogen K-edge) and calculations of the partial density of states based on first principles. The structure of the silica-shielded NP,CNNT system is analyzed by TEM and energy dispersive X-ray spectroscopy mapping, and their magnetism is measured by vibrating sample and superconducting quantum interference device magnetometers. The silica shielding helps maintain the superparamagnetism of the NPs; without the silica layer, the magnetic properties of NP,CNNT materials significantly degrade over time. [source] Generation of Monodisperse Inorganic,Organic Janus Microspheres in a Microfluidic DeviceADVANCED FUNCTIONAL MATERIALS, Issue 10 2009Naveen Prasad Abstract This study presents a simple synthetic approach for the in situ preparation of monodisperse hybrid Janus microspheres (HJM) having organic and inorganic parts in a PDMS-based microfluidic device. Based on the mechanism of shear-force-driven break-off, merged droplets of two photocurable oligomer solutions having distinctive properties are generated into an immiscible continuous phase. Functionalized perfluoropolyether (PFPE) as the organic phase and hydrolytic allylhydridopolycarbosilane (AHPCS) as the inorganic phase are used for the generation in aqueous medium of HJM with well-defined morphology and high monodispersity (average diameter of 162,µm and a 3.5% coefficient of variation). The size and shape of the HJM is controlled by varying the flow rate of the disperse and continuous phases. The HJM have two distinctive regions: a hydrophobic hemisphere (PFPE) having a smooth surface and a relatively hydrophilic region (AHPCS) with a rough, porous surface. In addition, pyrolysis and subsequent oxidation of these HJM convert them into SiC-based ceramic hemispheres through the removal of the organic portion and etching off the silica shell. The selective incorporation of magnetic nanoparticles into the inorganic part shows the feasibility of the forced assembly of HJM in an applied magnetic field. [source] Labeling of Adipose-Derived Stem Cells by Oleic-Acid-Modified Magnetic NanoparticlesADVANCED FUNCTIONAL MATERIALS, Issue 8 2009Lian Cen Abstract The in vivo tracking of adipose derived stem cells (ASCs) is of essential concern when they are used as seed cells in tissue engineering. This study explores the feasibility of using magnetic nanoparticles (MNs), a type of contrast agents in magnetic resonance imaging (MRI), to label ASCs such that the labeled ASCs could be tracked in vivo by MRI non-invasively and repeatedly. To do this, MNs of <10,nm surface-coated with oleic acid are synthesized via a high-temperature solution-phase reaction. Cytotoxicity of the as-synthesized MNs at concentrations up to 0.1,mg,mL,1 on 104,cells,mL,1 ASCs is evaluated by LDH release. Since only minor cytotoxicity is detected, the effects of the labeling technique on cellular behaviors and uptake by labeled cells are investigated. Cell proliferation and differentiation with and without MNs are compared. The results show that proliferation of ASCs (104,cells,mL,1) labeled by MNs (0.05,mg,mL,1) is significantly enhanced and dependent on the labeling time. The MNs are located in the vesicles within cytoplasm of ASCs. The cellular uptake reaches as high as ,180,pg/cell. Nevertheless, the labeled ASCs still maintained adipogenic and osteogenic differentiation. Hence, the feasibility of labeling ASCs by oleic acid coated MNs is ascertained and it was better to label the cells during their quiescent stage. The labeled ASCs can also be in vivo detected by MRI in a subcutaneous model in vivo. Further MRI tracking of the labeled ASCs in long-term follow-up would thus follow this current study. [source] Design and Fabrication of Magnetically Functionalized Core/Shell Microspheres for Smart Drug DeliveryADVANCED FUNCTIONAL MATERIALS, Issue 2 2009Xiuqing Gong Abstract The fabrication of magnetically functionalized core/shell microspheres by using the microfluidic flow-focusing (MFF) approach is reported. The shell of each microsphere is embedded with magnetic nanoparticles, thereby enabling the microspheres to deform under an applied magnetic field. By encapsulating a drug, for example, aspirin, inside the microspheres, the drug release of the microspheres is enhanced under the compression,extension oscillations that are induced by an AC magnetic field. This active pumping mode of drug release can be controlled by varying the frequency and magnitude of the applied magnetic field as well as the time profile of the magnetic field. UV absorption measurements of cumulative aspirin release are carried out to determine the influence of these factors. The drug release behavior is found to be significantly different depending on whether the applied field varies sinusoidally or in a step-function manner with time. [source] Templated Synthesis of Mesoporous Superparamagnetic Polymers,ADVANCED FUNCTIONAL MATERIALS, Issue 14 2007B. Fuertes Abstract We present a novel synthetic strategy for fabricating superparamagnetic nanoparticles randomly dispersed in a mesoporous polymeric matrix. This method is based on the use of mesoporous silica materials as templates. The procedure used to obtain these mesoporous magnetic polymers consisted in: a),generating iron oxide ferrite magnetic nanoparticles (FMNP) of size ,,7,8,nm within the pores of the silica, b),loading the porosity of the silica/FMNP composite with a polymer (Polydivinylbenzene), c),selectively removing the silica framework from the resulting silica/FMNP/polymer composite. Such magnetic porous polymeric materials exhibit large surface areas (up to 630,m2,g,1), high pore volumes (up to 0.73,cm3,g,1) and a porosity made up of mesopores. In this way, it is possible to obtain superparamagnetic mesoporous hybrid nanocomposites that are easily manipulated by an external magnetic field and display different magnetic behaviours depending on the textural properties of the template employed. [source] Cover Picture: Composite Silica Spheres with Magnetic and Luminescent Functionalities (Adv. Funct.ADVANCED FUNCTIONAL MATERIALS, Issue 4 2006Mater. Abstract Photographs of a colloidal dispersion of composite nanoparticles with magnetic and luminescent functionalities are shown (left, in column), which are schematically illustrated in the main image. As reported by Salgueirińo-Maceira and co-workers on p.,509, such functionalities are imparted by magnetic and semiconductor nanoparticles within a silica matrix. In the absence of a magnetic field the particles are uniformly dispersed, although they accumulate and can be dragged under the influence of a magnetic field. Their movement can be monitored by their photoluminescence. A new class of highly fluorescent, photostable, and magnetic core/shell nanoparticles in the submicrometer size range has been synthesized from a modified Stöber method combined with the layer-by-layer (LbL) assembly technique. Luminescent magnetic nanoparticles are prepared via two main steps. The first step involves controlled addition of tetraethoxysilane to a dispersion of Fe3O4/,-Fe2O3 nanoparticles, which are thereby homogeneously incorporated as cores into monodisperse silica spheres. The second step involves the LbL assembly of polyelectrolytes and luminescent CdTe quantum dots onto the surfaces of the silica-coated magnetite/maghemite particles, which are finally covered with an outer shell of silica. These spherical particles have a typical diameter of 220,±,10,nm and a saturation magnetization of 1.34,emu,g,1 at room temperature, and exhibit strong excitonic photoluminescence. Nanoparticles with such a core/shell architecture have the added benefit of providing a robust platform (the outer silica shell) for incorporating diverse functionalities into a single nanoparticle. [source] Palladium(II)-Phosphine Complexes Supported on Magnetic Nanoparticles: Filtration-Free, Recyclable Catalysts for Suzuki,Miyaura Cross-Coupling ReactionsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 2-3 2010Sankaranarayanapillai Shylesh Abstract An organic-inorganic hybrid heterogeneous nanocatalyst system was synthesized by covalent grafting a palladium dichloride complex of the type (L)2PdCl2 (L=trimethoxysilyl-functionalized triphenylphosphine) on silica-coated magnetic nanoparticles. It is a highly active and recyclable catalyst for the Suzuki,Miyaura cross-coupling reaction. The new catalyst can easily be separated from the reaction mixture by applying an external magnetic field and can be recycled many times without any loss of activity. [source] Magnetic Nanoparticle Supported Second Generation Hoveyda,Grubbs Catalyst for Metathesis of Unsaturated Fatty Acid EstersADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 16 2009Zhu Yinghuai Abstract The Hoveyda,Grubbs catalyst has been successfully immobilized on surface-modified magnetic nanoparticles with a loading amount of 0.28,mmol ruthenium/g (magnetic support). The supported catalysts were active for the self-metathesis of methyl oleate and macro-monomer in a quantitative conversion, respectively. In addition, the catalyst can be easily separated by using a magnet and reused several times with sustained activity. [source] Nanoparticle Supported, Magnetically Recoverable Oxodiperoxo Molybdenum Complexes: Efficient Catalysts for Selective Epoxidation ReactionsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 11-12 2009Sankaranarayanapillai Shylesh Abstract Organic-inorganic hybrid heterogeneous nanocatalyst systems were synthesized by covalent anchoring of oxodiperoxomolybdenum complexes [(LL)MoO(O2)2] on silica coated magnetic nanoparticles as an active, magnetically separable epoxidation catalyst. [source] Platinum Nanoparticles Supported on Ionic Liquid-Modified Magnetic Nanoparticles: Selective Hydrogenation CatalystsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 13 2007Raed Abu-Reziq Abstract A method for supporting platinum nanoparticles on magnetite nanoparticles is described. The method requires modification of the surface of the magnetic nanoparticles with ionic liquid groups. Before modification, the magnetic nanoparticles are not stable and easily aggregate and, after modification, the magnetite nanoparticles become highly stable and soluble in polar or non-polar organic solvents depending on the alkyl group of the linked ionic liquids. The supporting of platinum nanoparticles on the modified magnetic nanoparticles was achieved by adsorbing platinum salts (K2PtCl4) on the surface of the magnetite nanoparticles via ion exchange with the linked ionic liquid groups and then reducing them by hydrazine. The supported platinum nanoparticles were applied in the catalytic hydrogenation of alkynes in which cis -alkenes were selectively produced, and in the hydrogenation of ,,,-unsaturated aldehydes where the allyl alcohols were obtained as the exclusive products. The new catalyst can be easily separated from the reaction mixtures by applying an external magnetic field and recycled. [source] Local dynamics in epoxy coatings containing iron oxide nanoparticles by dielectric relaxation spectroscopyJOURNAL OF APPLIED POLYMER SCIENCE, Issue 5 2008G. Kortaberria Abstract Nanocomposites of photocurable epoxy resin and epoxy-modified iron oxide magnetic nanoparticles were analyzed by dielectric relaxation spectroscopy to study the local dynamics at temperatures well below the glass-transition temperature. Two secondary processes were detected, , and , processes, but the second one was just detected at lower temperatures in the high-frequency part of the spectra and moved out of the frequency range at higher temperatures. Data were fitted to the Havriliak,Negami and Arrhenius models, and the obtained parameters were analyzed. Relaxation times of the , secondary relaxation did not change with the nanoparticle content, but the relaxation strength increased. The increase could not be explained when we took into account the molecular origin of the relaxation. The presence of ferromagnetic nanoparticles enhanced the internal field and increased the relaxation strengths. Transmission electron microscopy images showed that the nanoparticles were well dispersed in the matrix, without magnetic agglomerates. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci 2008 [source] Non-viral VEGF165 gene therapy , magnetofection of acoustically active magnetic lipospheres (,magnetobubbles') increases tissue survival in an oversized skin flap modelJOURNAL OF CELLULAR AND MOLECULAR MEDICINE, Issue 3 2010Thomas Holzbach Abstract Adenoviral transduction of the VEGF gene in an oversized skin flap increases flap survival and perfusion. In this study, we investigated the potential of magnetofection of magnetic lipospheres containing VEGF165 -cDNA on survival and perfusion of ischemic skin flaps and evaluated the method with respect to the significance of applied magnetic field and ultrasound. We prepared perfluoropropane-filled magnetic lipospheres (,magnetobubbles') from Tween60-coated magnetic nanoparticles, Metafectene, soybean-oil and cDNA and studied the effect in an oversized random-pattern-flap model in the rats (n= 46). VEGF-cDNA-magnetobubbles were administered under a magnetic field with simultaneously applied ultrasound, under magnetic field alone and with applied ultrasound alone. Therapy was conducted 7 days pre-operative. Flap survival and necrosis were measured 7 days post-operatively. Flap perfusion, VEGF-protein concentration in target and surrounding tissue, formation and appearance of new vessels were analysed additionally. Magnetofection with VEGF-cDNA-magnetobubbles presented an increased flap survival of 50% and increased flap perfusion (P < 0.05). Without ultrasound and without magnetic field, the effect is weakened. VEGF concentration in target tissue was elevated (P < 0.05), while underlying muscle was not affected. Our results demonstrate the successful VEGF gene therapy by means of magnetobubble magnetofection. Here, the method of magnetofection of magnetic lipospheres is equally efficient as adenoviral transduction, but has a presumable superior safety profile. [source] Microwave-assisted graft polymerization of ,-caprolactone onto magnetiteJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 20 2009Alexandrina Nan Abstract The graft polymerization of ,-caprolactone (,-CL) onto magnetite was carried out under microwave irradiation in the presence of tin(II) 2-ethylhexanoate. The molar ratio of ,-CL to tin(II) 2-ethylhexanoate was 300, whereas the molar ratio of ,-CL to magnetite was 5. The chemical structures of the obtained poly(,-caprolactone) coated magnetic nanoparticles were characterized by FTIR and XPS spectroscopy. These magnetic-polymer hybrid nanostructures were further investigated by X-ray diffraction and magnetization measurements. The morphology of the magnetic core-shell nanostructures were determined by TEM. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5397,5404, 2009 [source] | ||||||||||||||||||||||||||||||||||