Highly biocompatible and water-dispersible, amine functionalized magnetite nanoparticles, prepared by a low temperature, air-assisted polyol process: a new platform for bio-separation and diagnostics

A low temperature polyol process, based on glycolaldehyde mediated partial reduction of FeCl3 center dot 6H(2)O at 120 degrees C in the presence of sodium acetate as an alkali source and 2,2'-(ethylenedioxy)-bis-(ethylamine) as an electrostatic stabilizer has been used for the gram-scale preparation of biocompatible, water-dispersible, amine functionalized magnetite nanoparticles (MNPs) with an average diameter of 6 +/- 0.75 nm. With a reasonably high magnetization (37.8 e.m.u.) and amine groups on the outer surface of the nanoparticles, we demonstrated the magnetic separation and concentration implications of these ultrasmall particles in immunoassay. MRI studies indicated that these nanoparticles had the desired relaxivity for T-2 contrast enhancement in vivo. In vitro biocompatibility, cell uptake and MR imaging studies established that these nanoparticles were safe in clinical dosages and by virtue of their ultrasmall sizes and positively charged surfaces could be easily internalized by cancer cells. All these positive attributes make these functional nanoparticles a promising platform for further in vitro and in vivo evaluations.

``Clickable'', Trifunctional Magnetite Nanoparticles and Their Chemoselective Biofunctionalization

A multifunctional iron oxide based nanoformulation for combined cancer-targeted therapy and multimodal imaging has been meticulously designed and synthesized using a chemoselective ligation approach. Novel superparamagnetic magnetite nanoparticles simultaneously functionalized with amine, carboxyl, and azide groups were fabricated through a sequence of stoichiometrically controllable partial succinylation and Cu (II) catalyzed diazo transfer on the reactive amine termini of 2-aminoethylphosphonate grafted magnetite nanoparticles (MNPs). Functional moieties associated with MNP surface were chemoselectively conjugated with rhodamine B isothiocyanate (RITC), propargyl folate (FA), and paclitaxel (PTX) via tandem nucleophic addition of amine to isothithiocyanates, Cu (I) catalyzed azide-alkyne click chemistry and carbodiimide-promoted esterification. An extensive in vitro study established that the bioactives chemoselectively appended to the magnetite core bequeathed multifunctionality to the nanoparticles without any loss of activity of the functional molecules. Multifunctional nanoparticles, developed in the course of the study, could selectively target and induce apoptosis to folate-receptor (FR) overexpressing cancer cells with enhanced efficacy as compared to the free drug. In addition, the dual optical and magnetic properties of the synthesized nanoparticles aided in the real-time tracking of their intracellular pathways also as apoptotic events through dual fluorescence and MR-based imaging.

Magnetic properties of tin-doped magnetite nanoparticles

Structural and magnetic characteristics of Fe3-xSnxO4 (x < 0.3) nanoparticles synthesized using the precipitation exchange method have been investigated by X-ray diffraction, transmission electron microscope, Mossbauer spectra, X-ray photoelectron spectroscopy and magnetization measurement. The mean particle dimension decreases from 8 to 6 nm, the lattice parameters enlarge, the saturation magnetization decreases, as well as the magnetization and the coercive field increase, with increasing tin-content. The paramagnetic property of the specimens indicates that the replacement of Fe3+ by Sn4+ on the octahedral sites of Fe3O4 causes a progressive lowering of the Curie temperature and the Curie temperatures of the materials are all lower than that of crystallite tin-doped magnetite. This striking debasing is due to the lessening of the grain size. This is the smallest size reported thus far for paramagnetic tin-doped magnetite particles. (c) 2006 Elsevier B.V. All rights reserved.

On the chemical synthesis and drug delivery response of folate receptor-activated, polyethylene glycol-functionalized magnetite nanoparticles

We describe here the chemical synthesis and in vitro drug delivery response of polyethylene glycol (PEG)-functionalized magnetite (Fe3O4) nanoparticles, which were activated with a stable ligand, folic acid, and conjugated with an anticancer drug, doxorubicin. The functionalization and conjugation steps in the chemical synthesis were confirmed using Fourier transform infrared spectroscopy. The drug-release behavior of PEG-functionalized and folic acid-doxorubicin-conjugated magnetic nanoparticles was characterized by two stages involving an initial rapid release, followed by a controlled release. (C) 2007 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Monodisperse mesoporous superparamagnetic single-crystal magnetite nanoparticles for drug delivery

In this contribution, we report a facile, gram-scale, low-cost route to prepare monodisperse superparamagnetic single-crystal magnetite NPs with mesoporous structure (MSSMN) via a very simple solvothermal method. The formation mechanism of MSSMN is also discussed and we think that Ostwald ripening probably plays an important role in this synthesis process. It is also interestingly found that the size and morphology of mesoporous Fe3O4 NPs can be easily controlled by changing the amount of NaOH and 1,2-ethylenediamine (ETH). Most importantly, the MSSMN can be used as an effective drug delivery carrier. A typical anticancer drug, doxorubicin (Dox), is used for drug loading, and the release behaviors of Dox in two different pH solutions are studied. The results indicate that the MSSMN has a high drug loading capacity and favorable release property for Dox; thus, it is very promising for the application in drug delivery.

Facile coprecipitation to synthesize water-soluble amine-capped magnetite nanoparticles

Water solubility and surface functionalization of magnetic nanoparticles are crucial for bioapplication.[1]In this study,we presented a facile coprecipitation approach to synthesize lysine stabilized Fe3O4 nanoparticles.Lysine functionalized magnetite nanoparticles show an excellent colloidal stability of ＞20h.The as-synthesized magnetite nanoparticles have abundant amine groups on their surface which provide convenient sites for covalent linking of biological macromolecules.We believe that these amine-functionalized magnetic nanoparticles can be potentially used in fields such as magnetic bio-separation,immunoassay,MRI,and targeted drug delivery.

Synthesis and functionalization of magnetite nanoparticles with different amino-functional alkoxysilanes

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Synthesis and electrochemical behavior of single-crystal magnetite nanoparticles

Water-dispersed magnetite nanoparticle synthesis from iron(II) chloride in dimethyl sulfoxide (DMSO)-water solution at different DMSO-water ratios in alkaline medium was reported. TEM and XRD results suggest a single-crystal formation with mean particle size in the range 4-27 nm. Magnetic nanoparticles are formed by the oxidative hydrolysis reaction from green rust species that leads to FeOOH formation, followed by autocatalysis of the adsorbed available Fe(II) on the FeOOH surfaces. The available hydroxyl groups seem to be dependent on the DMSO-water ratio due to strong molecular interactions presented by the solvent mixture. Goethite phase on the magnetite surface was observed by XRD data only for sample synthesized in the absence of DMSO. In addition, cyclic voltammetry with carbon paste electroactive electrode (CV-CPEE) results reveal two reduction peaks near 0 and +400 mV associated with the presence of iron(III) in different chemical environments related to the surface composition of magnetite nanoparticles. The peak near +400 mV is related to a passivate thin layer surface such as goethite on the magnetite nanoparticle, assigned to the intensive hydrolysis reaction due to strong interactions between DMSO-water molecules in the initial solvent mixture that result in a hydroxyl group excess in the medium. Pure magnetite phase was only observed in the samples prepared at 30% (30W) and 80% (80W) water in DMSO in agreement with the structured molecular solvent cluster formation. The goethite phase present on the, magnetite nanoparticle surface like a thin passivate layer only was detectable using CV-CPEE, which is a very efficient, cheap, and powerful tool for surface characterization, and it is able to determine the passivate oxyhydroxide or oxide thin layer presence on the nanoparticle surface.

Microwave-assisted hydrothermal synthesis of magnetite nanoparticles with potential use as anode in lithium ion batteries

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Stabilization of polyaniline by the incorporation of magnetite nanoparticles

Nanocomposites obtained from the polymerization of aniline in the presence of nanoparticles of magnetite (Fe3O4) have been investigated in previous studies. However, there is a lack of information available on the redox interaction of the nanoparticle/conductive polymer couple and the stability that such an oxide can give to the organic phase. In this work, Fe3O4 nanoparticles were incorporated into a PANi matrix by the in-situ oxidative polymerization method. A combination of X-ray diffraction, Mossbauer spectroscopy, transmission electronic microscopy, UV-visible spectroscopy as well as the cyclic voltammetric and Raman spectroscopy techniques, was used to understand the redox effect that the partially oxidized nanoparticles produced on the polymer. It was found that magnetite greatly stabilised PANi, mainly by enhancing the Leucoemeraldine/Emeraldine redox couple and also by reducing the bipolaronic state. (C) 2011 Elsevier B.V. All rights reserved.

The processing of polyelectrolyte-covered magnetite nanoparticles in the form of nanostructured thin films

Magnetic nanoparticles are promising for a variety of applications, such as biomedical devices, spin electronics, magnetic data storage media, to name a few. However, these goals may only be reached if stable and organized structures are fabricated. In this article, we report on a single-step synthetic route with the coprecipitation method, in which iron oxide magnetic nanoparticles (Fe3O4 NPs) were stabilized in aqueous media using the poly(diallyldimethylammonium chloride) (PDAC) polyelectrolyte. The Fe3O4 NPs had a diameter of ca. 5 nm, according to transmission electron microscopy (TEM) images, being arranged in an inverse spinel structure typical of magnetite. An investigation with infrared spectroscopy indicated that the mechanisms of stabilization in the polymer matrix were based on the interaction between quaternary amide groups from PDAC and the nanoparticle surface. The Fe3O4-PDAC NPs exhibited considerable magnetic susceptibility, with a monotonic increase in the magnetization with decreasing temperature. These Fe3O4-PDAC NPs were immobilized in layer-by-layer (LbL) films, being alternated with layers of poly(vinylsulfonic acid) (PVS). The LbL films were much rougher than typical films made with polyelectrolytes, and Fe3O4-PDAC NPs have been responsible for the high electrocatalytic activity toward H2O2 reduction, with an overpotential shift of 0.69 V. Overall, the stability, magnetic properties and film-forming ability indicate that the Fe3O4-PDAC NPs may be used for nanoelectronics and bioelectrochemical devices requiring reversible and magnetic redox materials.

Application of the Z-scan technique to determine the optical Kerr coefficient and two-photon absorption coefficient of magnetite nanoparticles colloidal suspension

We investigate the occurrence of the optical Kerr effect and two-photon absorption when an oil-based magnetic Fe3O4 nanoparticles colloidal suspension is illuminated with high intensity femtosecond laser pulses. The frequency of the pulses is controlled and the Z-scan technique is employed in our measurements of the nonlinear optical Kerr coefficient (n(2)) and two-photon absorption coefficient (beta). From these values it was possible to calculate the real and imaginary parts of the third-order susceptibility. We observed that increasing the pulse frequency, additional physical processes take place, increasing artificially the absolute values of n(2) and beta. The experimental conditions are discussed to assure the obtention of reliable values of these nonlinear optical parameters, which may be useful in all-optical switching and optical power limiting applications. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4723829]

Analysis of biogenic magnetite nanoparticles

Cobalt doped magnetite (CoxFe3-xO4) nanoparticles have been produced through the microbial reduction of cobalt-iron oxyhydroxide by the bacterium Geobacter sulfurreducens. The materials produced, as measured by SQUID, x-ray magnetic circular dichroism, Mössbauer spectroscopy, etc., show dramatic increases in coercivity with increasing cobalt content without a major decrease in overall saturation magnetization. Structural and magnetization analyses reveal a reduction in particle size to <4 nm at the highest Co content, combined with an increase in the effective anisotropy of the magnetic nanoparticles. The potential use of these biogenic nanoparticles in aqueous suspensions for magnetic hyperthermia applications is demonstrated. Further analysis of the distribution of cations within the ferrite spinel indicates that the cobalt is predominantly incorporated in octahedral coordination, achieved by the substitution of Fe2+ site with Co2+, with up to 17 per cent Co substituted into tetrahedral sites.

Scaling up the production of biogenic magnetite nanoparticles

Although there are numerous examples of large-scale commercial microbial synthesis routes for organic bioproducts, few studies have addressed the obvious potential for microbial systems to produce inorganic functional biomaterials at scale. Here we address this by focusing on the production of nano-scale biomagnetite particles by the Fe(III)-reducing bacterium Geobacter sulfurreducens, which was scaled-up successfully from lab-scale to pilot plant-scale production, whilst maintaining the surface reactivity and magnetic properties which make this material well suited to commercial exploitation. At the largest scale tested, the bacterium was grown in a 50 L bioreactor, harvested and then inoculated into a buffer solution containing Fe(III)-oxyhydroxide and an electron donor and mediator, which promoted the formation of magnetite in under 24 hours. This procedure was capable of producing up to 120 g biomagnetite. The particle size distribution was maintained between 10 and 15 nm during scale-up of this second step from 10 ml to 10 L, with conserved magnetic properties and surface reactivity; the latter demonstrated by the reduction of Cr(VI). The process presented provides an environmentally benign route to magnetite production and serves as an alternative to harsher synthetic techniques, with the clear potential to be used to produce kg to tonne quantities.