Surface Of γ-Fe2O3 Nanoparticles Research Articles

Transient coating of γ-Fe2O3 nanoparticles with glutamate for its delivery to and removal from brain nerve terminals.

Glutamate is the main excitatory neurotransmitter in the central nervous system and excessive extracellular glutamate concentration is a characteristic feature of stroke, brain trauma, and epilepsy. Also, glutamate is a potential tumor growth factor. Using radiolabeled ʟ-[14C]glutamate and magnetic fields, we developed an approach for monitoring the biomolecular coating (biocoating) with glutamate of the surface of maghemite (γ-Fe2O3) nanoparticles. The nanoparticles decreased the initial rate of ʟ-[14C]glutamate uptake, and increased the ambient level of ʟ-[14C]glutamate in isolated cortex nerve terminals (synaptosomes). The nanoparticles exhibit a high capability to adsorb glutamate/ʟ-[14C]glutamate in water. Some components of the incubation medium of nerve terminals, that is, 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid (HEPES) and NaH2PO4, decreased the ability of γ-Fe2O3 nanoparticles to form a glutamate biocoating by about 50% and 90%, respectively. Only 15% of the amount of glutamate biocoating obtained in water was obtained in blood plasma. Albumin did not prevent the formation of a glutamate biocoating. It was shown that the glutamate biocoating is a temporal dynamic structure at the surface of γ-Fe2O3 nanoparticles. Also, components of the nerve terminal incubation medium and physiological fluids responsible for the desorption of glutamate were identified. Glutamate-coated γ-Fe2O3 nanoparticles can be used for glutamate delivery to the nervous system or for glutamate adsorption (but with lower effectiveness) in stroke, brain trauma, epilepsy, and cancer treatment following by its subsequent removal using a magnetic field. γ-Fe2O3 nanoparticles with transient glutamate biocoating can be useful for multifunctional theranostics.

Magnetic‐Nanoparticle‐Supported 2,2′‐Bis[3‐(triethoxysilyl)propyl]imidazolium‐Substituted Diethyl Ether Bis(tribromide): A Convenient Recyclable Reagent for Bromination

A new magnetic-nanoparticle-supported bromination reagent was synthesized by anchoring a 2,2′-bis[3-(triethoxysilyl)propyl]imidazolium-substituted diethyl ether bis(tribromide) onto the surface of γ-Fe2O3 nanoparticles and subsequently treating this new ionic liquid with bromine. The nanoparticle reagent was obtained with good loading levels and has been successfully used for the efficient bromination of a wide range of alkenes, alkynes, ketones, and aromatic substrates. More importantly, the reagent could be easily recovered by an external magnet and reused six times without significant loss of activity.

Fabrication of Magnetic Hydroxyapatite Microcapsule for Protein Collection

When pH or temperature of simulated body fluid (SBF) is raised, fine particles of calcium phosphate are precipitated. We found that this fine particle actively induces hydroxyapatite from body fluid or SBF and named the particle Apatite Nucleus (AN). In this study, we attached AN on the surface of γ-Fe2O3 nanoparticles and soaked them in SBF. By this treatment, hydroxyapatite was induced from AN and covered the whole surface of the γ-Fe2O3 nanoparticles, then hydroxyapatite microcapsule encapsulated γ-Fe2O3 was fabricated. We dispersed the microcapsules in urease solution, and collected the microcapsules by neodymium magnet. It was indicated that the urease was adsorbed to the hydroxyapatite microcapsules and collected by the magnetism of γ-Fe2O3 successfully.

Nafion-based magnetically aligned nanocomposite proton exchange membranes for direct methanol fuel cells

Magnetic ion-conducting nanoparticles were prepared for application in polyelectrolyte membranes. The surface of γ-Fe2O3 nanoparticles is modified via silanation reaction and then by oxidation of the terminal mercapto groups to make functional sulfonate groups. The modified nanoparticles are characterized by using Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), scanning electron microscopy–energy dispersive X-ray spectroscopy (SEM–EDS) and vibrating sample magnetometer (VSM). Afterward, by applying the magnetic field during solvent casting and evaporation, Polyelectrolyte membranes are prepared based on Nafion and γ-Fe2O3 nanoparticles with oriented microstructure. Under such conditions, the subjected magnetic field induced nanoparticles form long chains extending across the membrane. By clustering sulfonate groups of Nafion around aligned nanoparticles, a short path length for proton transportation is achieved and leads to increase in proton conductivity. Effects of sulfonation and also ordering of the particles on swelling property, proton conductivity, activation energy, methanol permeability and selectivity are investigated. Nanocomposite membranes with oriented microstructure, due to high proton conductivity and low methanol permeability, displayed significantly enhanced selectivity in comparison with membranes with randomly distributed nanoparticles. This new type of proton exchange nanocomposite membranes could be considered as electrolytes for use in hydrogen or direct methanol fuel cells.

Post-synthesis heat treatments of γ-Fe2O3 nanoparticles embedded in a refractory matrix: From annealing of structural defects to doping

Magnetic nanoparticles (NPs) synthesized by low-temperature routes often present structural disorder, from extended defects to local rearrangements related to vacancy order or inversion in spinel ferrites. Post-synthesis heat treatments of preformed particles embedded in a refractory matrix are shown to modify magnetic anisotropy, either by annealing of crystal defects or by doping, while preserving the mean size and size distribution of the initial colloid. Such protected annealing of γ-Fe2O3 NPs allows a large and tunable increase of the anisotropy constant upon cobalt doping, using a two-step protocol that may involve adsorption of Co(II) ions at the surface of γ-Fe2O3 NPs followed by their dispersion in a silica matrix and heat treatments up to 600 °C.

Synthesis of Magnetic Fe2O3/Au Core/Shell Nanoparticles for Bioseparation and Immunoassay Based on Surface-Enhanced Raman Spectroscopy

Magnetic Fe2O3/Au core/shell nanoparticles can be particularly used in biological separation, but the development of an appropriate technique including a production process for higher efficient separation and the subsequent immunoassay for lower level still represent a great challenge. In this article, Fe2O3/Au core/shell nanoparticles with different Au ratios were prepared by reducing HAuCl4 on the surface of gamma-Fe2O3 nanoparticles. Scanning electron microscopy (SEM) images and surface-enhanced Raman spectroscopy (SERS) spectra clearly show that the surfaces of Fe2O3 nanoparticles were covered by Au. SERS signals of pyridine (Py) have been obtained on the Fe2O3/Au nanoparticles, and it has been found that the SERS intensity enhanced with the increase of iterative additions of HAuCl4. The antigens in test solution have been effectively separated by the magnetic Fe2O3/Au core/shell nanoparticles, and subsequent rapid detection was examined by immunoassay analysis based on SERS. The result demonstrates that the magnetic bioseparation program used by this magnetic Fe2O3/Au core/shell nanoparticles could separate almost all of the antigens in test solution. The ease of operation and good separation efficiency of this effective method has shown a potential application for magnetic Fe2O3/Au core/shell nanoparticles in bioseparation.

Cobalt doped γ-Fe2O3 nanoparticles: synthesis and magnetic properties

We demonstrate here the wet chemical synthesis of cobalt dopedγ-Fe2O3 nanoparticles and the subsequent effect on magnetic properties with the variation in dopantconcentration. It is observed that cobalt can be homogeneously doped into theγ-Fe2O3 lattice up to 5 mol% without any appreciable change in the particle size ( nm). Further increase in cobalt concentration (10 mol% here) resulted in an increase inparticle size ( nm) due to possible adsorption of a cobalt layer on the surface ofγ-Fe2O3 nanoparticles rather than complete doping in the iron oxide lattice. The acsusceptibility measurements revealed an increase in blocking temperature(TB) with percentage variation in cobalt doping (2–10%), indicating substitution ofFe3+ ions byCo2+ ionsin the γ-Fe2O3 lattice. The dc magnetization measurements showed an increase in saturation magnetizationonly up to 5%, beyond which it significantly diminished. The reduction in saturationmagnetization is attributed to the contribution from surface anisotropy in cobalt coatedγ-Fe2O3 nanoparticles.