Dispersed Iron Oxide Nanoparticles Research Articles

Micellar Iron Oxide Nanoparticles Coated with Anti-Tumor Glycosides.

The synthesis procedure of nanoparticles based on thermal degradation produces organic solvent dispersible iron oxide nanoparticles (OA-IONP) with oleic acid coating and unique physicochemical properties of the core. Some glycosides with hydrophilic sugar moieties bound to oleyl hydrophobic chains have antimitotic activity on cancer cells but reduced in vivo applications because of the intrinsic low solubility in physiological media, and are prone to enzymatic hydrolysis. In this manuscript, we have synthetized and characterized OA-IONP-based micelles encapsulated within amphiphilic bioactive glycosides. The glycoside-coated IONP micelles were tested as Magnetic Resonance Imaging (MRI) contrast agents as well as antimitotics on rat glioma (C6) and human lung carcinoma (A549) cell lines. Micelle antimitotic activity was compared with the activity of the corresponding free glycosides. In general, all OA-IONP-based micellar formulations of these glycosides maintained their anti-tumor effects, and, in one case, showed an unusual therapeutic improvement. Finally, the micelles presented optimal relaxometric properties for their use as T2-weighed MRI contrast agents. Our results suggest that these bioactive hydrophilic nano-formulations are theranostic agents with synergistic properties obtained from two entities, which separately are not ready for in vivo applications, and strengthen the possibility of using biomolecules as both a coating for OA-IONP micellar stabilization and as drugs for therapy.

Ferrofluid synthesis using oleic acid coated Fe3O4 nanoparticles dispersed in mineral oil for heat transfer applications

Ferrofluids are stable dispersion of iron oxide nanoparticles in a carrier fluid which find potential applications in heat transfer. Fe3O4 nanoparticles of mean size in the range of 5–10 nm were synthesized using conventional co-precipitation method. This work deals with the synthesis of ferrofluids using mineral oil as a carrier fluid and oleic acid coated Fe3O4 nanoparticles as dispersed phase. Morphology (shape and size) and crystallinity of the synthesized nanoparticle is captured using TEM and XRD. Oleic acid coating on nanoparticle is probed using FTIR for confirming the stability of ferrofluid. Thermal properties of mineral oil based ferrofluid with varying concentration of nanoparticles are evaluated in terms of thermal conductivity. It was found that the thermal conductivity of ferrofluid increases upto 2.5% (w/v) nanoparticle loading, where a maximum enhancement of ∼51% in thermal conductivity was recorded as compared to the base fluid.

Exogenous mineralization of hard tissues using photo-absorptive minerals and femto-second lasers; the case of dental enamel

A radical new methodology for the exogenous mineralization of hard tissues is demonstrated in the context of laser-biomaterials interaction. The proposed approach is based on the use of femtosecond pulsed lasers (fs) and Fe3+-doped calcium phosphate minerals (specifically in this work fluorapatite powder containing Fe2O3 nanoparticles (NP)). A layer of the synthetic powder is applied to the surface of eroded bovine enamel and is irradiated with a fs laser (1040 nm wavelength, 1 GHz repetition rate, 150 fs pulse duration and 0.4 W average power). The Fe2O3 NPs absorb the light and may act as thermal antennae, dissipating energy to the vicinal mineral phase. Such a photothermal process triggers the sintering and densification of the surrounding calcium phosphate crystals thereby forming a new, dense layer of typically ∼20 μm in thickness, which is bonded to the underlying surface of the natural enamel. The dispersed iron oxide NPs, ensure the localization of temperature excursion, minimizing collateral thermal damage to the surrounding natural tissue during laser irradiation. Simulated brushing trials (pH cycle and mechanical force) on the synthetic layer show that the sintered material is more acid resistant than the natural mineral of enamel. Furthermore, nano-indentation confirms that the hardness and Young’s modulus of the new layers are significantly more closely matched to enamel than current restorative materials used in clinical dentistry. Although the results presented herein are exemplified in the context of bovine enamel restoration, the methodology may be more widely applicable to human enamel and other hard-tissue regenerative engineering. Statement of significanceIn this work we provide a new methodology for the mineralisation of dental hard tissues using femtosecond lasers and iron doped biomaterials. In particular, we demonstrate selective laser sintering of an iron doped fluorapatite on the surface of eroded enamel under low average power and mid-IR wavelength and the formation of a new layer to substitute the removed material. The new layer is evaluated through simulated brushing trials and nano-indentation. From the results we can conclude that is more acid resistant than natural enamel while, its mechanical properties are superior to that of current restorative materials. To the best of our knowledge this is the first time that someone demonstrated, laser sintering and bonding of calcium phosphate biomaterials on hard tissues. Although we here we discuss the case of dental enamel, similar approach can be adopted for other hard tissues, leading to new strategies for the fixation of bone/tooth defects.

Hexagonal-shaped aminosilane magnetite nanoparticles: Preparation, characterization and hybrid film deposition

Hexagonal amino-functionalized magnetite nanoparticles were successfully produced by two-step method: initially, bare Fe3O4 nanoparticles were obtained by partial oxidation of ferrous ions in alkaline conditions, followed by hydroxyl groups interchanging with (3-aminopropyl) triethoxysilane (APTES) moieties. The products were evaluated for possible water repellent applications. Hybrid ternary films were prepared by spray coating in a layer-by-layer configuration: the hybrid polymeric matrix first, followed by modified iron oxide nanoparticle dispersion, both mixed with the third component, pre-hydrolyzed/precondensed sol–gel solution of hexadecyltrimethoxy silane (HSi). The found results demonstrate the ability of the hexagonal amino-functionalized magnetite nanoparticles to self-assembly and generate hierarchical roughness.

Optimization of Magneto-thermally Controlled Release Kinetics by Tuning of Magnetoliposome Composition and Structure

Stealth (PEGylated) liposomes have taken a central role in drug formulation and delivery combining efficient transport with low nonspecific interactions. Controlling rapid release at a certain location and time remains a challenge dependent on environmental factors. We demonstrate a highly efficient and scalable way to produce liposomes of any lipid composition containing homogeneously dispersed monodisperse superparamagnetic iron oxide nanoparticles in the membrane interior. We investigate the effect of lipid composition, particle concentration and magnetic field actuation on colloidal stability, magneto-thermally actuated release and passive release rates. We show that the rate and amount of encapsulated hydrophilic compound released by actuation using alternating magnetic fields can be precisely controlled from stealth liposomes with high membrane melting temperature. Extraordinarily low passive release and temperature sensitivity at body temperature makes this a promising encapsulation and external-trigger-on-demand release system. The introduced feature can be used as an add-on to existing stealth liposome drug delivery technology.

Retention of ferrofluid aggregates at the target site during magnetic drug targeting

The present study reports the retention dynamics of a ferrofluid aggregate localized at the target site inside a glass capillary (500×500µm2 square cross section) against a bulk flow of DI water (Re=0.16 and 0.016) during the process of magnetic drug targeting (MDT). The dispersion dynamics of iron oxide nanoparticles (IONPs) into bulk flow for different initial size of aggregate at the target site is reported using the brightfield visualization technique. The flow field around the aggregate during the retention is evaluated using the µPIV technique. IONPs at the outer boundary experience a higher shear force as compared to the magnetic force, resulting in dispersion of IONPs into the bulk flow downstream to the aggregate. The blockage effect and the roughness of the outer boundary of the aggregate resulting from chain like clustering of IONPs contribute to the flow recirculation at the downstream region of the aggregate. The entrapment of seeding particles inside the chain like clusters of IONPs at the outer boundary of the aggregate reduces the degree of roughness resulting in a streamlined aggregate at the target site at later time. The effect of blockage, structure of the aggregate, and disturbed flow such as recirculation around the aggregate are the primary factors, which must be investigated for the effectiveness of the MDT process for in vivo applications.

Electroactive nanofluids with high solid loading and low viscosity for rechargeable redox flow batteries

A typical dispersion of iron oxide nanoparticles in alkali electrolyte is limited to 20 wt% solids, above which it has a paste-like consistency (>370 cP), incompatible with flow applications. The formulation of stable electrochemically active colloids of nanoscale iron oxide (30–50 nm) with up to 70 wt% solids, low viscosity ( 2 weeks at rest), and 55% enhancement in thermal conductivity is reported herein. A thin surface coating allows for good particle dispersion, which is shown to be crucial for these enhanced features. These suspensions of electrochemically active nanoparticles (nanoelectrofuels) can undergo electrochemical charge and discharge in fluidized format through particle–electrode impact events with potential for application in redox flow batteries. The surface coating is found to partially suppress electrochemical access to the nanoparticle in a fluidized format but has no detrimental effects on discharge capacity in the solid state. This approach is also shown to suppress a parasitic nanoparticle agglomeration process, which is otherwise dominant during electrochemical cycling of pristine iron oxide. A dissolution re-precipitation mechanism is proposed to offer insight into this auxiliary benefit. This study provides the first insight into the feasibility of adopting electrochemically active nanofluids as high energy density redox flow battery electrolytes.

In Vivo Imaging of Local Gene Expression Induced by Magnetic Hyperthermia.

The present work aims to demonstrate that colloidal dispersions of magnetic iron oxide nanoparticles stabilized with dextran macromolecules placed in an alternating magnetic field can not only produce heat, but also that these particles could be used in vivo for local and noninvasive deposition of a thermal dose sufficient to trigger thermo-induced gene expression. Iron oxide nanoparticles were first characterized in vitro on a bio-inspired setup, and then they were assayed in vivo using a transgenic mouse strain expressing the luciferase reporter gene under transcriptional control of a thermosensitive promoter. Iron oxide nanoparticles dispersions were applied topically on the mouse skin or injected subcutaneously with Matrigel™ to generate so-called pseudotumors. Temperature was monitored continuously with a feedback loop to control the power of the magnetic field generator and to avoid overheating. Thermo-induced luciferase expression was followed by bioluminescence imaging 6 h after heating. We showed that dextran-coated magnetic iron oxide nanoparticle dispersions were able to induce in vivo mild hyperthermia compatible with thermo-induced gene expression in surrounding tissues and without impairing cell viability. These data open new therapeutic perspectives for using mild magnetic hyperthermia as noninvasive modulation of tumor microenvironment by local thermo-induced gene expression or drug release.

Synthesis of stable iron oxide nanoparticle dispersions in high ionic media

A novel one-pot method was developed in this work to synthesize and disperse nanoparticles in a binary base fluid. As an example, stable magnetite iron oxide (Fe3O4) dispersions, i.e., nanofluids, were produced in a high ionic media of binary lithium bromide-water using a microemulsion-mediated method. The effects of temperature and precursor concentration on morphology and size distribution of produced nanoparticles were evaluated. An effective steric repulsion force was provided by the surface functionalization of nanoparticles during the phase transfer, supported by the Derjaguin–Landau–Verwey–Overbeek (DLVO) theory. The formed nanoparticles exhibited a superior stability against agglomeration in the presence of high concentrations of lithium bromide, i.e., from 20 to 50 wt.%, which make them good candidates for a range of novel applications.

One pot synthesis of amine-functionalized and angular-shaped superparamagnetic iron oxide nanoparticles for MR/fluorescence bimodal imaging application

Herein, we report the simple preparation of water dispersible angular-shaped amine-functionalized super-paramagnetic iron oxide nanoparticles (A-SPIONs).

Amine-functionalized magnetic nanoparticles as robust support for immobilization of Lipase

Preparation of magnetic nanoparticles with controlled size and shape along with modulation of their surface properties via introduction of functional groups holds great prospect in the field of nanotechnology. Superparamagnetic, aqueous dispersible iron oxide nanoparticles (Fe3O4) with amine-functionalized surface were prepared through solvothermal method, using poly(ethylene imine) (PEI), ethanolamine (EA), and 2,2 ′-(ethylenedioxy)bis(ethylamine) (EDBE) as amine precursors. These aminated nanoparticles were used as support for the immobilization of lipase, an important industrial enzyme. Lipase was immobilized via glutaraldehyde coupling agent. These functionalized nanoparticles were characterized by XRD, FTIR, TEM, FESEM and VSM analysis. The maximum activity was obtained for the lipase immobilized on EDBE modified Fe3O4 nanoparticles. The lipase immobilized on EDBE-Fe3O4 depicted 83.9% relative activity with respect to the same amount of free lipase. Moreover, lipase immobilized on EDBE-Fe3O4 nanoparticles demonstrated good thermal and storage stability, and easy reusability. The kinetic parameters of lipase immobilized on EDBE-Fe3O4 were compared with those of free lipase and the apparent Michaelis-Menten constant of immobilized lipase was found to be nearly same as that of free lipase.

Fabrication of mixed matrix poly(phenylene ether-ether sulfone)-based nanofiltration membrane modified by Fe3O4 nanoparticles for water desalination

Abstract In the current research, poly(phenylene ether-ether sulfone) (PEES)-co-poly vinyl pyrrolidone (PVP) nanofiltration membranes were prepared by a casting solution technique using N-methyl-2-pyrrolidone (NMP) as a solvent. The ethanol was used as fixed additive for better dispersion of iron oxide nanoparticles into the membranes structure. The effect of iron oxide nanoparticle concentration in the casting solution on the membrane performance/properties was studied. The membrane pure water flux, permeated flux, salt rejection, water content, tensile strength and membrane porosity were studied. Scanning electron microscopy (SEM) analysis was also used for the membrane morphology characterization. The results revealed that water content increased from 70.25% for bare PEES to about 83.25% for the membrane filled with 0.05 wt.% nanoparticles. SEM images showed that the membrane structure changed and turned from sponge shape to finger like. The results showed that porosity was increased from 55.92% for PEES one to 69.65% for M3. Additionally, the maximum value of flux was obtained for M3. Moreover, rejection was improved by the addition of nanoparticles into the casting solution compared to the unfilled one. Obtained results showed more appropriate performance for the modified membrane filled with 0.05 wt.% iron oxide nanoparticles compared to other prepared membranes.

Control of magnetite primary particle size in aqueous dispersions of nanoclusters for high magnetic susceptibilities

Aqueous dispersions of iron oxide nanoparticles with a high initial magnetic susceptibility (χi) are of interest as contrast agents in electromagnetic tomography. Nanoclusters composed of iron oxide primary particles were formed by co-precipitation of Fe(II) and Fe(III) chlorides at alkaline conditions and high temperature of 95°C. Two-step addition of citrate was used to produce large primary particles and then stabilize the nanoclusters. The size of the primary particles was tuned from 5nm to 15nm by varying the citrate/iron precursor ratio during the normal phase hydrolysis reaction, while the second iteration of citrate stabilized the nanoclusters with hydrodynamic diameters of 30–75nm. The crystallinity of the iron oxide nanoparticles was promoted by annealing at 95°C and systematically studied with Superconducting Quantum Interference Device (SQUID), Vibrating Sample Magnetometer (VSM), Transmission Electron Microscopy (TEM) and X-ray Diffraction (XRD). The dependence of χi was examined over a range of low volume fractions (0.005<θ<0.02) to understand the magnetic behavior of dispersions. The χi of the dispersions increased markedly with the size and concentration of the constituent primary particles, reaching an unusually high value of 0.85 at 1.6% v/v for 15nm primary particles, which is 2–3 times higher than that for typical commercial ferrofluids. The high χi values are favored by the high crystallinity and the large magnetic diameter of 9.3nm, indicating a relatively thin surface nonmagnetic layer where the spin orientations are disordered.

Synthesis and characterization of stable aqueous dispersion of functionalized double-coated iron oxide nanoparticles

Stable water dispersed iron oxide nanoparticles, double-coated by a first layer of oleic acid followed by a second layer of the reactive surfactant dodec-1-ene-1-sodium sulfonate (Rhodacal®A-246L) were synthesized. Dynamic light scattering (DLS) analysis revealed an average particles size and polydispersity of 48nm and 0.2, respectively. The particles size and zeta potential were dependent on the pH. The product was also characterized by X-ray diffraction, FTIR, thermogravimetric analysis (TGA) and saturation magnetization, which confirmed the modification of the nanoparticles surface by the double layer of stabilizing agents. Transmission electron microscopy (TEM) confirmed the formation of particles aggregates.

Magnetically Controlled Release of Dispersed Iron Oxide Nanoparticles from Imprinted Organic Thin Films

Iron oxide nanoparticles (Fe3O4-NP) were compressed together with oleic acid (OA) in a Langmuir-Blodgett trough. Optimized dilution of the NP allowed the transfer of two-dimensional nanocomposites of Fe3O4-NP and OA to gold substrates. The characterization of the two-dimensional composite by scanning force microscopy (SFM) showed the existence of a sub-monolayer coverage with a few NP being pushed into the second layer. Polarization modulation infrared reflection absorption spectra (PM IRRAS) showed the presence of oleic acid. The nanoparticles could be removed in an external magnetic field of a permanent magnet as evidenced by SFM while the OA monolayer was left on the gold substrate as shown by PM IRRAS. Such composite layers can be used for the controlled release of specified small amount of intact NP.

Highly Dispersed Iron Oxide Nanoparticles Synthesized by Solvothermal Method Adding Electrostatic Stabilizers

Magnetite nanoparticles (Fe3O4) in the range of submicrometer in diameters were prepared by modified solvothermal process adding electrostatic stabilizers to be applied for biomedical applications. Added electrostatic stabilizers could prevent the magnetic particles from agglomerating and slow down the reaction rate so that the size of Fe3O4 nanoparticles could be controlled. The average diameter of magnetic nanoparticles synthesized in the presence of different electrostatic stabilizers (citrate, didodecyldimethylammonium bromide, and polyethylene glycol) was in the range of 150–350 nm. All of the prepared samples exhibited sufficiently high saturation magnetization ${\boldsymbol M_{\boldsymbol s}}$ value of 60–73 emu/g showing superparamagnetic behavior. They could also be easily redispersed in water after magnetic collection.

Ce doping effect on performance of the Fe/β catalyst for NOx reduction by NH3

The Ce doping Fe/β catalysts were prepared by an easy incipient wetness impregnation method and characterized using various analytical techniques, including H2-TPR, XRD, UV–vis and XPS. The results demonstrated that the addition of cerium effectively improved the deNOx performance, hydrothermal stability and SO2 resistance of the Fe/β catalyst for the selective catalytic reduction (SCR) of NOx by NH3. The finely dispersed iron oxide nanoparticles on the surface of Ce–Fe/β catalysts and the compensative effect of cerium are dominating reasons for high catalytic performance. The Ce doping enhanced the hydrothermal stability of the Fe/β catalyst because it could control the growth of iron oxides and stabilize the dispersed iron species. Suppressing the deposition of sulfates by Ce addition made the Fe/β catalyst a great SO2 tolerance. It was speculated that the outstanding performance of Ce doping Fe/β catalysts made them attractive for practical application.

PREPARATION OF AN ANTIBACTERIAL NANO-BIOCOMPOSITE BY DISPERSION OF IRONOXIDE NANOPARTICLES INTO CMC

In recent years, new materials with advanced properties has attracted great interest in technological applications. The main reason for this is because of the increasing number of people who is dependent of technology-based consumption. Some of the important advanced properties for these new materials are mechanical, barrier and thermal stability. To be successful in preparing a new material with advanced properties, the size of the nanoparticles and its dispersion into the host matrix is extremely important [1-3]. In this study, Carboxymethyl Cellulose (CMC)/silica nano-biocomposite is prepared with a simple chemical method. As a nanofiller silica is used. Iron oxide nanoparticles are embedded into CMC. To reach, well distribution in nano scale of both silica and iron oxide, different amounts of inorganic phase are studied. Distribution of both silica and iron oxide are determined by Scanning Electron Microscopy (SEM) technique. To establish the crystal structure of iron oxide nanoparticles X-Ray Diffraction (XRD) technique is used. Homogenous distribution and The particles appeared dispersed uniformly in CMC. The antibacterial property of the new surface is examined against the gram-negative Escherichia coli. The antibacterial activity of the surface is largely dependent both on the dimension and the dispersion of iron oxide nanoparticles.

Magnetic ELISA of aflatoxin B1 – pre-concentration without elution

This study proposes an ELISA variant based on the application of highly dispersed (average diameter – 10 nm) magnetic iron oxide nanoparticles as carriers for the adsorbable antibodies.

SiO2 versus chelating agent@ iron oxide nanoparticles: interactions effect in nanoparticles assemblies at low magnetic field

Hydrophilic magnetic nanoparticles present many interest for various medical applications due to their unique properties: immunoassays, imaging and hyperthermia. With regards to their applicability in the biomedical field, colloidal stability is a key parameter related to nanoparticle surface functionalization. In this paper, we report the water transfer of hydrophobic oleic acid coated iron oxide nanoparticles comparing two methodologies to obtain water dispersible iron oxide nanoparticles: exchange ligands with small strong chelating agent (caffeic acid) and SiO2 shell passivation. Both strategies are leading to stable aqueous ferrofluid but differing by their interactions. The non linear magnetic behavior at high and low magnetic field and second derivative signature of water dispersed superparamagnetic Fe304 nanoparticles samples are studied using conventional SQUID equipment and miniaturized detector MIAplex® device. We demonstrated those samples differing only by their interparticle interactions present different magnetic behavior at very low magnetic field whereas at high magnetic field both samples are very similar.