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Results for “Magnetite Nanoparticles”

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At least 73 records · Page 4Linked to original sources

PubMed2005

Removal of nanoparticles from CMP wastewater by magnetic seeding aggregation.

CMP wastewaters have high solids content resulted from abrasive nanoparticles. Tremendous amount of ultrapure water consumption also makes the removal of nanoparticles from CMP wastewaters an important issue. Magnetic seeding aggregation of silica nanoparticles from the oxide CMP wastewater is studied in this work. Magnetite nanoparticles were synthesized and used as seeding particles. The turbidity of the CMP wastewater was reduced from 110 NTU to 7 NTU when solution pH was 6 and no addition of salt. This is because silica and magnetite nanoparticles were highly oppositely charged and the aggregation between silica and magnetite nanoparticles was achieved by electrostatic attractions. When the seeded wastewater was placed in a magnetic field strength higher than 800 G, the turbidity of the CMP wastewater was reduced to 1 NTU, which was clearer than the CMP wastewater treated by many other technologies.

Electronics↗

PubMed2006

Preparation of poly epsilon-caprolactone nanoparticles containing magnetite for magnetic drug carrier.

Magnetic poly epsilon-caprolactone (PCL) nanoparticles were prepared in a well shaped spherical form by the o/w emulsion method. The influence of some preparative variables on the size and surface property was investigated. Nanoparticles were smooth, well individualized and homogeneous in size. The presence of magnetite and its superparamagnetic characteristic were confirmed by transmission electron microscope (TEM), Fourier transform infrared spectroscopy (FT-IR) and vibrating sample magnetometer (VSM), respectively. The anti-cancer drug was encapsulated in the magnetic nanoparticle during preparation. A typical release behavior was observed for 30 days. In vitro experiment of magnetic susceptibility under external magnetic field demonstrated that the magnetic PCL nanoparticles have sufficient magnetic susceptibility for a potential magnetic drug carrier for targeted delivery.

Cisplatin↗

PubMed1997

Investigation of blood-brain barrier permeability to magnetite-dextran nanoparticles (MD3) after osmotic disruption in rats.

The permeability of experimentally disrupted blood-brain barrier (BBB) to superparamagnetic nanoparticles (MD3) was studied in rats. BBB opening was induced by intracarotid injection of mannitol. One hundred eighty rats were used for the study. Rats were examined at two time points, 30 minutes and 12 hours after intracarotid mannitol injection. Different preparations intravenously injected 30 minutes before rat sacrifice were used for characterization of BBB disruption. BBB integrity was determined with 99mTc-diethylenetriamine pentaacetic acid (DTPA) and 99mTc-albumin. Iron oxide-glucose particles (12-nm mean diameter), 99mTc-labeled lecithin-cholesterol liposomes of three different sizes (50, 100, and 200 nm), and polyethylene glycol (PEG)-coated 99mTc liposomes (50 nm) were used for investigations of the dependence of BBB permeability on particle system size or surface. Magnetite-dextran nanoparticles (MD3) were evaluated as superparamagnetic contrast agent to monitor with magnetic resonance imaging (MRI) the BBB breakdown. In vitro T1 and T2 relaxation times of the brain tissue were measured at 40 MHz and 37 degrees C, and T2-weighted MR images were acquired at 0.5 T. After intracarotid mannitol infusion, as expected, the BBB breakdown was immediate and temporary as judged by soluble molecule diffusion. MD3 nanoparticles crossed the BBB 12 hours after intravenous mannitol injection, at a time when brain permeability for molecules or small particles returns to normal. Magnetite crystals were found in cytoplasmic vesicles of glial cells. On MRI, signal intensity decreased after injection of MD3, even 12 hours after mannitol injection. This particularity could be useful in the study of focal pathological lesions accompanied by BBB permeability modifications. In such conditions, superparamagnetic particle contrast agents could be caught by the BBB, allowing the observation of impaired BBB areas without detectable cellular lesions.

Animals↗

PubMed2002

[Preparation of surface functional magnetic microspheres and their application in nucleic acid separation and enzyme immobilization].

OBJECTIVE: To Prepare surface functional magnetic microspheres for the separation of vascular endothelial growth factor (VEGF) nucleic acid and lactase enzyme immobilization. METHODS: Using suspension polymerization methods to copolymerize MA-styrene containing magnetite nanoparticles and GMA-styrene also containing magnetite nanoparticles, respectively. Both the carboxyl-modified magnetic microspheres and epoxy-modified magnetic microspheres were obtained. In addition, the chloromethyl-modified magnetic microspheres were prepared by seedy microemulsion. The magnetic microspheres bound with b-gamma IgG were determined by radioimmunoassay (RIA), and the separation of VEGF nucleic acid and lactase enzyme immobilization were performed by carboxyl-modified magnetic microspheres. RESULTS: Transmission electron microscopy (TEM), energy-dispersive spectroscopy (EDS) and infrared (IR) spectra showed that the products of polymer magnetic microspheres were monodispersed and that the magnetic particles were uniformly distributed in the microsphere with special functional group on the surface of the microsphere. RIA showed that three kinds of magnetic microspheres could be bound with b-gamma IgG and the absorption of b-gamma IgG reached 75 micrograms/mg, especially for the carboxyl-modified magnetic microspheres. The carboxyl-modified magnetic microspheres can be used for the separation of VEGF nucleic acid by coupling with corresponding primer. Moreover, the immobilized enzyme was proportional to the amount of the carboxyl-modified magnetic microspheres. CONCLUSIONS: The surface functional magnetic polymer microspheres can be bound with active bio-substance, and have a wide application prospect in the fields of biology and medicine.

Adsorption↗

PubMed2007

Synthesis and characterization of biocompatible Fe3O4 nanoparticles.

In this study, magnetite (Fe3O4) nanoparticles with a size range of 8-20 nm were prepared by the modified controlled chemical coprecipitation method from the solution of ferrous/ferric mixed salt-solution in alkaline medium. In the process, two kinds of surfactant (sodium oleate and polyethylene glycol) were studied; then, sodium oleate was chosen as the apt surfactant to attain ultrafine, nearly spherical and well-dispersed (water-base) Fe3O4 nanoparticles, which had well magnetic properties. The size and size distribution of nanoparticles were determined by particle size analyzer. And the magnetite nanoparticles was characterized by X-ray powder diffraction (XRD) analysis, transmission electron microscopy (TEM), electron diffraction (ED) photography, Fourier transform infrared spectrometer (FT-IR), and vibrating-sample magnetometer (VSM). Also the effect of many parameters on the Fe3O4 nanoparticles was studied, such as reaction temperature, pH of the solution, stirring rate and concentration of sodium oleate. And the 5-dimethylthiazol-2-yl-2,5- diphenyltetrazolium bromide (MTT) assay was performed to evaluate the biocompatibility of magnetite nanoparticles. The results showed that the Fe3O4 nanoparticles coated by sodium oleate had a better biocompatibility, better magnetic properties, easier washing, lower cost, and better dispersion than the magnetite nanoparticles coated by PEG.

3T3 Cells↗

PubMed2005

Medical application of functionalized magnetic nanoparticles.

Since magnetic particles have unique features, the development of a variety of medical applications has been possible. The most unique feature of magnetic particles is their reaction to a magnetic force, and this feature has been utilized in applications such as drug targeting and bioseparation including cell sorting. Recently, magnetic nanoparticles have attracted attention because of their potential as contrast agents for magnetic resonance imaging (MRI) and heating mediators for cancer therapy (hyperthermia). Magnetite cationic liposomes (MCLs), one of the groups of cationic magnetic particles, can be used as carriers to introduce magnetite nanoparticles into target cells since their positively charged surface interacts with the negatively charged cell surface; furthermore, they find applications to hyperthermic treatments. Magnetite nanoparticles conjugated with antibodies (antibody-conjugated magnetoliposomes, AMLs) are also applied to hyperthermia and have enabled tumor-specific contrast enhancement in MRI via systemic administration. Since magnetic nanoparticles are attracted to a high magnetic flux density, it is possible to manipulate cells labeled with magnetic nanoparticles using magnets; this feature has been applied in tissue engineering. Magnetic force and MCLs were used to construct multilayered cell structures and a heterotypic layered 3D coculture system. Thus, the applications of these functionalized magnetic nanoparticles with their unique features will further improve medical techniques.

Animals↗

PubMed2004

Magnetic hydrophilic methacrylate-based polymer microspheres designed for polymerase chain reactions applications.

Magnetic hydrophilic non-porous P(HEMA-co-EDMA), P(HEMA-co-GMA) and PGMA microspheres were prepared by dispersion (co)polymerization of 2-hydroxyethyl methacrylate (HEMA) and ethylene dimethacrylate (EDMA) or glycidyl methacrylate (GMA) in the presence of several kinds of magnetite. It was found that some components used in the preparation of magnetic carriers interfered with polymerase chain reaction (PCR). Influence of non-magnetic and magnetic microspheres, including magnetite nanoparticles and various components used in their synthesis, on the PCR course was thus investigated. DNA isolated from bacterial cells of Bifidobacterium longum was used in PCR evaluation of non-interfering magnetic microspheres. The method enabled verification of the incorporation of magnetite nanoparticles in the particular methacrylate-based polymer microspheres and evaluation of suitability of their application in PCR. Preferably, electrostatically stabilized colloidal magnetite (ferrofluid) should be used in the design of new magnetic methacrylate-based microspheres by dispersion polymerization.

Bifidobacterium↗

PubMed2006

Synthesis of monodisperse iron oxide and iron/iron oxide core/shell nanoparticles via iron-oleylamine complex.

Monodisperse magnetic nanoparticles are of great scientific and technical interests. This paper reports a single-step synthesis of monodisperse magnetite nanoparticles with particle size of 8 nm. Iron/maghaemite core/shell nanoparticles with particle size of 11 nm were obtained by reducing the concentration of oleylamine. TEM and in-situ FTIR results suggested that iron-oleylamine intermediate was generated in-situ and decomposed at higher temperature. Oleylamine was also found on the surface of nanoparticles, indicating its role as capping agent which provided steric protection of as-synthesized nanoparticles from agglomeration. Both magnetite and iron/maghaemite core/shell nanoparticles were superparamagnetic at room temperature with a blocking temperature at 80 K and 67 K, respectively.

Adsorption↗

PubMed2005

Epithelial internalization of superparamagnetic nanoparticles and response to external magnetic field.

Superparamagnetic magnetite nanoparticles (MNP) coated with silica were synthesized and chronically implanted into the middle ear epithelial tissues of a guinea pig model (n=16) for the generation of force by an external magnetic field. In vivo limitations of biocompatibility include particle morphology, size distribution, composition and mode of internalization. Synthesis of MNP was performed using a modified precipitation technique and they were characterized by transmission electron microscopy, X-ray diffractometry and energy dispersive spectroscopy, which verified size distribution, composition and silica encapsulation. The mechanism for internalizing 16+/-2.3 nm diameter MNP was likely endocytosis, enhanced by magnetically force. Using sterile technique, middle ear epithelia of tympanic membrane or ossicles was exposed and a suspension of particles with fluoroscein isothiocyanate (FITC) label applied to the surface. A rare earth, NdFeBo magnet (0.35 T) placed under the animal, was used to pull the MNP into the tissue. After 8 days, following euthanasia, tissues were harvested and confocal scanning laser interferometry was used to verify intracellular MNP. Displacements of the osscicular chain in response to an external sinusoidal electromagnetic field were also measured using laser Doppler interferometry. We showed for the first time a physiologically relevant, biomechanical function, produced by MNP responding to a magnetic field.

Animals↗

PubMed2006

Oriented assembly of Fe3O4 nanoparticles into monodisperse hollow single-crystal microspheres.

Magnetite nanoparticles of Fe3O4 were found to assemble into monodisperse hollow Fe3O4 microspheres with tunable diameters ranging from 200 to 400 nm and open pores on the shells in ethylene glycol in the presence of dodecylamine (DDA). The oriented assembly of nanoparticles conferred the individual hollow Fe3O4 microspheres a remarkable feature of single crystals. The morphologies of the products could be easily manipulated by varying the synthesis parameters. Increasing the concentration of DDA led to an obvious shape evolution of the products from rhombic nanoparticles to hollow microspheres, solid microspheres, and finally irregular nanoparticles, which were mainly attributed to the special self-assembly phenomenon of Fe3O4 nanoparticles in the solvothermal process.

Ferrosoferric Oxide↗

PubMed2001

Biocolloids with ordered urease multilayer shells as enzymatic reactors.

The preparation of biocolloids with organized enzyme-containing multilayer shells for exploitation as colloidal enzymatic nanoreactors is described. Urease multilayers were assembled onto submicrometer-sized polystyrene spheres by the sequential adsorption of urease and polyelectrolyte, in a predetermined order, utilizing electrostatic interactions for layer growth. The catalytic activity of the biocolloids increased proportionally with the number of urease layers deposited on the particles, demonstrating that biocolloid particles with tailored enzymatic activities can be produced. It was further found that precoating the latex spheres with nanoparticles (40-nm silica or 12-nm magnetite) enhanced both the stability (with respect to adsorption) and enzymatic activity of the urease multilayers. The presence of the magnetite nanoparticle coating also provided a magnetic function that allowed the biocolloids to be easily and rapidly separated with a permanent magnet. The fabrication of such colloids opens new avenues for the application of bioparticles and represents a promising route for the creation of complex catalytic particles.

Colloids↗

PubMed2006

One-pot synthesis of pegylated ultrasmall iron-oxide nanoparticles and their in vivo evaluation as magnetic resonance imaging contrast agents.

A well-defined copolymer poly(oligo(ethylene glycol) methacrylate-co-methacrylic acid) P(OEGMA-co-MAA) was studied as a novel water-soluble biocompatible coating for superparamagnetic iron oxide nanoparticles. This copolymer was prepared via a two-step procedure: a well-defined precursor poly(oligo(ethylene glycol) methacrylate-co-tert-butyl methacrylate), P(OEGMA-co-tBMA) (M(n) = 17300 g mol(-1); M(w)/M(n) = 1.22), was first synthesized by atom-transfer radical polymerization in the presence of the catalyst system copper(I) chloride/2,2'-bipyridyl and subsequently selectively hydrolyzed in acidic conditions. The resulting P(OEGMA-co-MAA) was directly utilized as a polymeric stabilizer in the nanoparticle synthesis. Four batches of ultrasmall PEGylated magnetite nanoparticles (i.e., with an average diameter below 30 nm) were prepared via aqueous coprecipitation of iron salts in the presence of variable amounts of P(OEGMA-co-MAA). The diameter of the nanoparticles could be easily tuned in the range 10-25 nm by varying the initial copolymer concentration. Moreover, the formed PEGylated ferrofluids exhibited a long-term colloidal stability in physiological buffer and could therefore be studied in vivo by magnetic resonance (MR) imaging. Intravenous injection into rats showed no detectable signal in the liver within the first 2 h. Maximum liver accumulation was found after 6 h, suggesting a prolongated circulation of the nanoparticles in the bloodstream as compared to conventional MR imaging contrast agents.

Animals↗

PubMed1999

Titration of the BOLD effect: separation and quantitation of blood volume and oxygenation changes in the human cerebral cortex during neuronal activation and ferumoxide infusion.

Most functional magnetic resonance imaging (fMRI) techniques are sensitive to susceptibility variations and rely on the change in blood oxygenation level in response to neuronal activation (BOLD). The BOLD effect is accompanied by a change in cerebral blood flow (rCBF) and cerebral blood volume (rCBV). Intravascular contrast agents, such as magnetite nanoparticles, can be used to measure changes in rCBV. A new measuring protocol has been developed that enables the separate quantification of changes in blood volume and oxygenation levels. A combination of alternating acoustic stimulation blocks and infusion of a superparamagnetic contrast agent offers the possibility to disentangle the competing influences of oxygenation and blood volume changes. Serial blood sampling during infusion was used to assess the actual contrast agent concentration during infusion in order to calculate absolute blood volume changes during neuronal resting and activation states. Magn Reson Med 42:829-836, 1999.

Acoustic Stimulation↗

PubMed2001

Bicuculline-induced brain activation in mice detected by functional magnetic resonance imaging.

Dynamic measurements of local changes in relative cerebral blood volume (CBV(rel)) during a pharmacological stimulation paradigm were performed in mice. Using magnetite nanoparticles as an intravascular contrast agent, high-resolution CBV(rel) maps were obtained. Intravenous administration of the GABA(A) antagonist bicuculline prompted increases in local CBV(rel) as assessed by MRI with a high spatial resolution of 0.2 x 0.2 mm(2) and a temporal resolution of 21 s. Signal changes occurred 20-30 s after the onset of drug infusion in the somatosensory and motor cortex, followed by other cortical and subcortical structures. The magnitudes of the CBV(rel) increases were 18% +/- 4%, 46% +/- 14%, and 67% +/- 7%, as compared to prestimulation values for the cortex, and 9% +/- 3%, 25% +/- 4%, and 36% +/- 7% for the caudate putamen for bicuculline doses of 0.6, 1.25, and 1.5 mg/kg, respectively. On-line monitoring of transcutaneous carbon dioxide tension PtcCO(2) reflecting arterial PaCO(2) did not show any alteration during the stimulation paradigm. One of five of the mice receiving the highest bicuculline dose, and three of seven receiving the intermediate dose displayed a different cortical response pattern. After a CBV(rel) increase of 40% lasting for approximately 1 min, significant CBV(rel)reductions by 80% have been observed. Subcortical structures did not display this behavior. The present study suggests that this noninvasive approach of functional MRI (fMRI) can be applied to study drug-induced brain activation by central nervous system (CNS) drugs in mice under normal and pathological situations.

Animals↗

PubMed2005

Magnetic colloidosomes derived from nanoparticle interfacial self-assembly.

Based on the interfacial self-assembly of magnetite nanoparticles, we demonstrate the formation of colloidosomes with shells predominantly composed of monolayers of liquid-like, close-packed nanoparticles. The gelation of aqueous phase with agarose leads to robust and water-dispersible nanoparticle colloidosomes, allowing encapsulation of various water soluble materials. The cutoff of the nanoparticle colloidosomes obtained is primarily defined by the nanoparticle size. This controllable permeability should be of great importance for the encapsulation application.

Colloids↗

PubMed2001

Magnetic resonance of a dextran-coated magnetic fluid intravenously administered in mice.

Magnetic resonance was used to investigate the kinetic disposition of magnetite nanoparticles (9.4 nm core diameter) from the blood circulation after intravenous injection of magnetite-based dextran-coated magnetic fluid in female Swiss mice. In the first 60 min the time-decay of the nanoparticle concentration in the blood circulation follows the one-exponential (one-compartment) model with a half-life of (6.9 +/- 0.7) min. The X-band spectra show a broad single line at g approximately 2, typical of nanomagnetic particles suspended in a nonmagnetic matrix. The resonance field shifts toward higher values as the particle concentration reduces, following two distinct regimes. At the higher concentration regime (above 10(14) cm(-3)) the particle-particle interaction responds for the nonlinear behavior, while at the lower concentration regime (below 10(14) cm(-3)) the particle-particle interaction is ruled out and the system recovers the linearity due to the demagnetizing field effect alone.

Animals↗

PubMed2006

Polymer-coated magnetic nanoparticles: surface modification and end-functionalization.

ATRP (atom transfer radical polymerization) approach was employed to synthesis polymer-coated magnetite nanoparticles. These particles had an average diameter of 7.1 nm and a narrow size distribution. Characterization was performed using various techniques like Transmission Electron Microscopy (TEM), Ultraviolet-Visible spectroscopy (UV-vis), Fourier Transform Infrared spectroscopy (FTIR), Atomic Force Microscopy (AFM), and Vibrating Sample Magnetometry (VSM). The challenge was to obtain a thin shell and discrete particles in an unagglomerated state. Several factors like presence/choice of solvent, monomer-to-initiator concentration and structure of initiator were found to play a key role in this study. Attempts have been made to tailor the polymer shells by end-functionalization. This work has an enormous biomedical application potential.

Crystallization↗

PubMed2003

Affinity selection of target cells from cell surface displayed libraries: a novel procedure using thermo-responsive magnetic nanoparticles.

Biotinylated thermo-responsive magnetic nanoparticles for use in affinity selection from yeast cell surface display libraries were prepared by coating magnetite nanoparticles with a thermo-responsive polymer consisting of N-isopropyl acrylamide and a biotin derivative. These particles showed a reversible transition between flocculation and dispersion at around the lower critical solution temperature of 30 degrees C, above which the flocculated particles--which absorbed a large amount of avidin due to their large surface area--were quickly separable by magnet. The model library was constructed by mixing control yeast cells with target yeast cells co-displaying IgG binding protein (ZZ) and enhanced green fluorescence protein. Biotinylated IgG and avidin were subsequently added to the model library, and target cells were efficiently enriched with the biotinylated magnetic nanoparticles by avidin-biotin sandwich and ZZ-IgG interaction. The few target cells (0.001%) in the model library were enriched by up to 100% in only 5 days by an affinity selection procedure repeated four times. This novel method based on magnetic nanoparticles and a yeast cell surface display system could fulfill a wide range of applications in the analysis of protein-protein interactions and rapid isolation of novel biomolecules.

Avidin↗