Superparamagnetic iron oxide nanoparticles for delivery of tissue plasminogen activator

Magnetic nanoparticle (MNP) modified by carboxymethyl dextran (CMD) was synthesized and characterized by Fourier transform infrared spectroscopy, transmission electron microscopy, superconducting quantum interference device, dynamic light-scattering, thermogravimetric analysis, and X-ray diffraction. CMD coating on the particle surface provides abundant -COOH functional groups for conjugating with a thrombolytic drug, recombinant tissue plasminogen activator (rtPA). CMD-coated MNP (CMD-MNP) prepared with higher CMD/MNP ratios had higher CMD content, less iron content, more -COOH surface groups, smaller hydrodynamic diameter, and smaller saturation magnetization. The in vitro biocompatibility study using lactate dehydrogenase assays indicated that CMD-MNP elicited no cell cytotoxicity. The optimum drug loading could be achieved by contacting 0.25 mg rtPA with 5 mg CMD-MNP where all rtPA is immobilized to the magnetic nanocarrier with full retention of its thrombolytic activity.     

Superparamagnetic iron oxide nanoparticles assembled magnetic nanobubbles and their application for neural stem cells labeling

Micro/nanobubbles for use as ultrasound contrast agents have been fabricated with different shell materials.When various biomedical nanoparticles have been embedded in the shells of bubbles,the composite structures have shown promising applications in multi-modal imaging,drug/gene delivery,and biomedical sensing.In this study,we developed a new gas-liquid interface self-assembly method to prepare magnetic nanobubbles embedded with superparamagnetic iron oxide nanoparticles(SPIONs).The diameter of the generated assembled nanobubbles was 227.40±87.21 nm with a good polydispersity index(PDI)of 0.29.Under the condition of 150 compression cycles,the nanobubble concentration could reach about 6.12×10⁹/mL.Transmission electron microscopy(TEM)and scanning electronic microscopy(SEM)demonstrated that the assembled nanobubbles had a hollow gas core with SPIONs adsorbed on the surface.Ultrasound(US)imaging and magnetic resonance imaging(MRI)experiments indicated that the assembled magnetic nanobubbles exhibited good US and MR contrast capabilities.Moreover,the assembled magnetic nanobubbles were used to label neural stem cells under ultrasound exposure.After 40 s US exposure,the magnetic nanobubbles could be delivered into cells with 2.80 pg Fe per cell,which could be observed in the intracellular endosome by TEM.Compared with common incubation methods,the ultrasound exposure method did not introduce the potential cytotoxicity of transfection reagents and the efficiency was about twice as high as the efficiency of incubation.Therefore,the assembled magnetic nanobubbles prepared through the pressure-driven gas-liquid interface assembly approach could be a potential US/MRI dual model imaging nanocarrier for regenerative applications.     

A simple synthesis of amine-derivatised superparamagnetic iron oxide nanoparticles for bioapplications

Adsorption of 3-aminopropyltriethoxysilane (APTS) on magnetite nanoparticles during its formation has been investigated to optimise the preparation of stable aqueous dispersion of amine derivatised magnetite nanoparticles. APTS adsorbs chemically on the surface of magnetite particle modifying its surface which is evident from thermal and C, H, N analysis. The variation of particle size has been observed with change of APTS concentration. X-ray diffractogram shows the formation of pure inverse spinel phase magnetite with average crystallite size 7 nm when equimolar (Fe₃O₄: APTS = 1:1) quantity of APTS was used during its synthesis. The presence of free surface –NH₂ groups and Fe–O–Si bonds was observed by FTIR. Raman spectrum further confirms the presence of surface –NH₂ groups. Transmission electron microscopy shows formation of particles of average size between 7 nm and 12 nm. The effective hydrodynamic diameter of the APTS coated particle agglomerates is 45.8 nm in stable aqueous colloidal dispersion, which is evident from photon correlation spectroscopy. VSM measurements at room temperature of both silanised and unsilanised magnetite shows their superparamagnetic nature with saturation magnetisation 41 e.m.u/g and 56 e.m.u/g, respectively. Avidin has been immobilised on the surface through glutaraldehyde, which demonstrates the possibility of the synthesised material to be used in protein immobilisation to form bioactive magnetic particles.     

Seed-mediated synthesis of iron oxide and gold/iron oxide nanoparticles

In this study, we prepared magnetic iron oxide and gold/iron oxide nanoparticles (NPs) and characterized their morphologies and properties by XRD, TEM, EDX, VSM and UV-vis measurements. The magnetite iron oxide NPs of 10 nm were synthesized by coprecipitation of Fe2+ and Fe+3 in the solution of NH4OH and then they were used as seed particles for the subsequent growth to prepare the magnetite NPs of different particle sizes and also to prepare gold/iron oxide composite NPs. All those magnetite NPs are superparamagnetic and the gold/iron oxide composite NPs combine the optical and magnetic properties, which are contributed by gold and iron oxide components, respectively.     

Carbon microspheres with embedded magnetic iron oxide nanoparticles

Narrow-size disperse porous carbon microspheres with embedded magnetite nanoparticles were prepared by annealing Fe(III)-containing microspheres composed of a copolymer of acrylic acid and divinylbenzene at 800 °C under inert atmosphere. The Fe(III)-containing microspheres were prepared by uptake of Fe²⁺ ions through ion exchange process by poly(acrylic acid-divinylbenzene) microspheres that were prepared by distillation-precipitation polymerization, followed by annealing at 250 °C at ambient atmosphere. The carbonization of the microspheres created micropores with a maximum pore diameter of about 0.38 nm and a BET surface area of ~ 200 m²/g. The saturation magnetization of the magnetic carbon microspheres was 31.5 emu/g with a low remnant magnetization and coercivity.     

Phase composition and magnetic properties of iron oxide nanoparticles obtained by impulse electric discharge in water

The chemical composition and the magnetic properties of iron oxide nanoparticles obtained by impulse electric discharge in water are investigated. The phase composition of the Fe₃O₄, Fe₂O₃, and Fe nanoparticles is determined. By means of the nuclear magnatiec resonance (NMR) technique, the magnetic moments of the nanoparticles are determined. The magnetic moment of the spherical nanoparticles equals to 2.39 × 10^–19 A m², and that of the cubical ones is 4.56 × 10^–19 A m².     

Microstructural evolution of iron oxide hollow nanoparticles toward iron oxide nanotubes in a prolonged sintering condition

Prolonged sintering of iron oxide hollow nanoparticles (HNPs) during chemical vapor condensation (CVC) at 800 °C for 6 h showed some interesting morphologies of the iron oxide nanotubes. TEM and XRD studies confirmed that single-walled nanotubes of a mixed phase of α, β, and γ-Fe₂O₃, with a wall thickness of less than 10 nm and an outer diameter of approximately 50 nm were synthesized. The formation of iron oxide nanotubes was thought to be an evolution of iron oxide HNPs based on the sintering.     

Biological crystallization of self-aligned iron oxide nanoparticles

Crystal growth and magnetic behavior of iron oxide nanoparticles assembled with biomolecules have been investigated. The nanoparticles assembled with trypsin molecules exhibit superparamagnetism at room temperature with blocking temperature ($sim$80 K) significantly lower than those without trypsin ($sim$140 K). This is attributed to reduced magnetostatic couplings between particles due to increased distance between particles separated by trypsin molecules. Moreover, the synthesized nanoparticle–biomolecule assemblies consist of a unique one-dimensional self-assembled arrays of nanoparticles found by structural analysis using transmission electron microscopy. The moirÉ fringes observed from the particle arrays indicate that the particles are aligned with slight misorientation of their crystallographic axes. Such an unusual formation of nanoparticle arrays may be relevant to specific ligand sites in trypsin molecules and the magnetostatic interparticle couplings.     

Abrasive properties of aluminum iron oxide nanoparticles

Aluminum iron oxide nanoparticles have been prepared by heat-treating ammonium hydroxycarbonate complexes with the general formula NH₄Al₂Fe(OH)₅(CO₃) · nH₂O and have been characterized by X-ray diffraction, IR spectroscopy, differential thermal analysis, scanning electron microscopy, and particle size analysis. The mixed oxide α-Al_{2 − x} Fe _x O₃ with x = 0.30−0.37 prepared from hydroxy complexes ensures surface roughness values R _a = 0.005−0.02 μm in polishing of the ShKh15 quenched steel with an austenite/martensite structure and offers high abrasion rate owing to its enhanced tribochemical activity and the presence of particles in the size range 1–10 nm.     

Hydrothermal synthesis of surface-modified iron oxide nanoparticles

We synthesized surface-modified iron oxide nanoparticles in aqueous phase by heating an aqueous solution of iron sulfate (FeSO₄) at 473 K with a small amount of either n-decanoic acid (C₉H₁₉COOH) or n-decylamine (C₁₀H₂₁NH₂), which is not miscible with water at room temperature. Transmission electron microscopy showed that the addition of n-decanoic acid or decylamine changed the shape of the obtained nanoparticles. X-ray diffraction spectra revealed that the synthesized nanoparticles were in α-Fe₂O₃ or Fe₃O₄ phase while Fourier transform infrared spectroscopy and thermogravimetry indicated the existence of an organic layer on the surface of the nanoparticles. In the synthetic condition, decreased dielectric constant of water at higher temperature increased the solubility of n-decanoic acid or n-decylamine in water to promote the reaction between the surface of iron oxide nanoparticles and the organic reagents. After the synthesis, the used organic modifiers separated from the aqueous phase at room temperature, which may help the environmentally benign synthesis of surface-modified metal oxide nanoparticles.     

Ultrasonic-assisted preparation of monodisperse iron oxide nanoparticles

Monodisperse iron oxide nanoparticles with 5–20 nm can be synthesized by an inexpensive and simple ultrasonic-assisted method at low temperature. This is based on the decomposition of iron pentacarbonyl in cis–trans decalin. The high energy emitted by ultrasonic irradiation at a short time can promote the crystallization process simultaneously. At low temperature, these crystalline nucleuses can grow to monodisperse nanoparticles. Effects of ultrasonic treatment, the concentration of surfactant and the refluxing time on the size and size distribution of iron oxide nanoparticles were investigated. The morphology and crystal structure of iron oxide nanoparticles obtained at different conditions were characterized by high-resolution transmission electron microscope, X-ray diffraction and selected area electron diffraction.     

Peculiarities of metal oxide nanoparticles obtained in acoustoplasma discharge

Nanoparticles of tungsten, copper, iron, and zinc oxides were synthesized in acoustoplasma discharge. Their size distribution was studied by electron microscopy and laser correlation spectroscopy. Ultrasound was found to narrow significantly the size distribution width of zinc oxide nanoparticles. Water suspensions of zinc oxide nanoparticles showed photoluminescence in red and near infrared spectral ranges, which makes them a promising material for luminescent diagnostics of biological systems.     

Glycoconjugated chitosan stabilized iron oxide nanoparticles as a multifunctional nanoprobe

Surface modification of iron oxide nanoparticles (IOPs) with functional polymer can be used for the preparation of multifunction nanoprobes. The present study dealt with the preparation of glycoconjugated chitosan (GC) stabilized IOPs (GC-IOPs). GC was prepared by direct coupling of lactobionic acid (LA) on chitosan. GC was subsequently grafted onto the surface of IOPs to enhance colloid stability. X-ray diffraction (XRD), Fourier transform infrared spectrometer (FT-IR), transmission electron microscopy (TEM), dynamic light scattering (DLS), electrophoretic light scattering (ELS) and superconducting quantum interference device (SQUID) measurements were performed to investigate the properties of nanoparticles. FT-IR and XRD analysis of GC-IOPs showed that backbone and side chain functionality of chitosan and phase purity of IOPs remained intact during conjugation. TEM observations revealed that GC-IOPs were spherical (8–10 nm) but the dispersibility and stability in acetated buffer (pH 7.4) linearly increased with degree of substitution (DS) of chitosan. The specific magnetization of GC-IOPs was varied with DS from 19.50 to 41.56 emu/g. This variation in colloid stability and specific magnetization suggests that DS can be varied to tailor the degree of dispersion and magnetic properties of IOPs. The advantage of GC-IOPS is the ability to achieve a homogeneous nanosize particle distribution and specific surface functionality for bioconjugation. These characteristics make the GC-IOPs a potential candidate for biomedical research and clinical diagnosis.     

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.     

Formation of water-soluble iron oxide nanoparticles derived from iron storage protein

This paper reports novel findings of an investigation of the formation of water-soluble iron oxide nanoparticles from iron-storage protein ferritin. The strategy couples thermal removal of the protein shell on a planar substrate and subsequent sonication in aqueous solution under controlled temperature. Advantages of using ferritin as a precursor include well-defined core size, core composition, water-solubility and processibility. The formation of the nanoparticles was characterized using TEM, UV-Vis and FTIR techniques. Iron oxide nanoparticles in the size range of 5-20 nm diameters were produced. In addition to thermal treatment conditions, the sonication temperature of the nanoparticles in water was found to play an important role in determining the resulting particle size. This simple and effective route has important implications to the design of composite nanoparticles for potential magnetic, catalytic, biomedical sensing and other nanotechnological applications.     

Functionalisation of glass with iron oxide nanoparticles produced by laser pyrolysis

In the present work, a new process for depositing nanoparticle layers onto glass has been developed by using one of the most interesting nanoparticle generation technologies at the moment, which is based on the pyrolysis induced by laser of vapours combined with CVD of the particles onto glass. Nanoparticles prepared by this method were deposited into a hot silica substrate obtaining new nanocomposites with unique properties. The coated glasses present new specific functionalities such as colour, and interesting magnetic and optical properties. Control of the thickness and the iron oxide phase, either magnetic or not, has been achieved by adjusting the experimental conditions. Thus, thickness is controlled by the glass and the precursor temperature, while the iron phase is controlled by the precursor temperature and the nature and the flow of the carrier gas. This process is inexpensive, adaptable to current glass production technologies and takes place at atmospheric pressure.     

Structure and magnetic properties of iron based nanoparticles with oxide shells

Oxide-coated iron nanoparticles with average dimensions from 6 to 75 nm have been synthesized by chemical vapor condensation. The structure of particles and their size distribution have been determined. These data are used to interpret the results of measurements of the magnetic hysteresis characteristics.     

Synthesis and characterization of multifunctional iron oxide nanoparticles

In order to get high water solubility, monodisperse, superparamagnetic nanoparticles, poly (acrylic acid) was employed to modify Fe3O4 by a high-temperature solution-phase hydrolysis approach. Then, folic acid (FA) and fluorescein isothiocyanate were successively conjugated with prepared magnetic nanoparticles (MNPs). The functional MNPs were characterized by X-ray diffraction (XRD), dynamic light scattering (DLS), transmission electron microscope (TEM), inductively coupled plasma-atomic emission spectrometer (ICP-AES), and vibrating sample magnetometer (VSM), respectively. The toxicity of the materials was evaluated by selecting NIH/3T3 fibroblast cells and no toxic effect was observed. The fluorescent imaging and targeting property of the MNPs were also realized in vitro and in vivo experiments by confocal laser scanning microscopy (CLSM) and Kodak In-Vivo FX Professional Imaging System, respectively. The results indicated that the final products exhibited interesting magnetic, optical and targeting properties for further potential applications in biological and biomedical fields.     

Fabrication of iron oxide nanoparticles: magnetic and electrochemical sensing property

In this paper, we report a simple synthesis of Fe₂O₃ nanoparticles using hydrothermal method. The formation of the sample was confirmed by X-ray diffraction analysis, X-ray photoelectron spectroscopy, Fourier transformed infrared spectroscopy, Raman spectroscopy and UV–Visible absorption spectroscopy. The average crystallite size of the synthesized Fe₂O₃ nanoparticles was estimated to be 61 nm and the particles were of good crystalline nature. Field emission-scanning electron microscopy study of the sample revealed that the Fe₂O₃ powder has rod-like morphology which is composed of nanoparticles. The vibrating sample magnetometer measurement shows that the nanoparticles possess ferromagnetic property. The synthesized Fe₂O₃ nanoparticles were used to modify glassy carbon electrode (Fe₂O₃/GCE) and the modified electrode was used to detect pyrocatechol (PC) in a pH 7.4 phosphate buffer solutions by cyclic voltammetry and chronoamperometry. At the Fe₂O₃/GCE, PC is oxidized at less positive potential with larger current response than the bare GCE. The proposed sensor exhibits great potential in the field of electrochemical sensing of PC.