Au-Fe3O4 Nanoparticles Research Articles

Open-tubular Capillary Electrochromatography with Janus Structured Au-Fe3O4 Nanoparticles Coating as Stationary Phase.

A novel Au-Fe3O4 nanoparticles-based capillary column was fabricated by magnetic approach for open-tubular capillary electrochromatography (OT-CEC). The bifunctional dumbbell-like Janus Au-Fe3O4 nanoparticles (Au-Fe3O4 NPs) were prepared through a hydrothermal synthesis strategy, and the morphology was characterized by transmission electron microscopy (TEM). Multilayers Au-Fe3O4 NPs were easily coated onto the inner surface of silica capillary by an external magnetic field to generate an Au-Fe3O4 NPs-based column. Compared with a bare capillary, the modified surface exhibited more stable and suppressed electroosmotic mobility. The column showed good separation efficiency for neutral analytes in the OT-CEC separation mode, with theoretical plate numbers of up to 79705 per meter for naphthalene. The successful separation of dihydroxy benzene isomers and proteins demonstrated that the column exhibits a reasonable separation performance. The reproducibility of the Au-Fe3O4 NPs capillary was studied, with relative standard deviations (RSD) for day-to-day and column-to-column less than 1 and 1.75%, respectively.

Injectable and Quadruple-Functional Hydrogel as an Alternative to Intravenous Delivery for Enhanced Tumor Targeting.

Intravenous (IV) route is the most commonly used drug-delivery approach. However, the targeting efficiency to tumor through IV delivery is usually less than 10%. To address this limitation, we report a new systemic delivery method utilizing injectable and quadruple-functional hydrogels to improve targeting efficiency through passive, active, and magnetic targeting, and hydrogel-controlled sustained release. The hydrogels consist of a folate/polyethylenimine-conjugated poly(organophosphazene) polymer, which encapsulates small interfering RNA (siRNA) and Au-Fe3O4 nanoparticles to form a nanocapsule (NC) structure by a simple mixing. The hydrogels are localized as a long-term "drug-release depot" after a single subcutaneous injection and sol-gel phase transition. NCs released from the hydrogels enter the circulatory systems and then target the tumor through enhanced permeability and retention/folate/magnetism triple-targeting, over the course of circulation, itself prolonged by the controlled release. In vivo experiments show that 12% of NCs are successfully delivered to the tumor, which is a considerable improvement compared to most results through IV delivery. The sustained targeting of gold to tumor enables two cycles of photothermal therapy, resulting in an enhanced silencing effect of siRNA and considerable reduction of tumor volume, which we are unable to achieve via simple intravenous injection.

Preparation, Characterization and Application of Multi-Mode Imaging Functional Graphene Au-Fe3O4 Magnetic Nanocomposites.

Nanomaterials extensively studied by nanotechnology scientists have been extensively applied in biomedicine, chemistry, physics and other fields nowadays. Magnetic nanoparticles, surpassing nano applications, are found to possess many advantages over nonmagnetic nanomaterials. Graphene oxide (GO), in particular, draws growing scholarly attention due to its large surface area, good water solubility and biocompatibility, rich surface functional group and easy-to-modify property. In this paper, we modify the Polyethylene mide (PEI) molecule on the surface of GO to increase its biocompatibility. The Au-Fe3O4 nanoparticles and folic acid molecules on the ligand make the resulting composite applicable both in magnetic resonance imaging and in cancer cell targeting. In addition, the π-π accumulation of doxorubicin used to load the anticancer drug can release the drug under the acid condition of the cancer cells, detect the cancer cells by fluorescence and realize the multi-mode detection of cancer cells.

Selective Single Molecule Nanopore Sensing of microRNA Using PNA Functionalized Magnetic Core-Shell Fe3O4-Au Nanoparticles.

Solid-state nanopores have been employed as useful tools for single molecule analysis due to their advantages of easy fabrication and controllable diameter, but selectivity is always a big concern for complicated samples. In this work, functionalized magnetic core-shell Fe3O4-Au nanoparticles, which acted as a molecular carrier, were introduced into nanopore electrochemical system for microRNA sensing in complicated samples with high sensitivity, selectivity and signal-to-noise ratio (SNR). This strategy is based on the specific affinity between neutral peptide nucleic acids (PNA)-modified Fe3O4-Au nanoparticles and negative miRNA, and the formation of negative Fe3O4-Au-PNA-miRNA complex, which can pass through the nanopore by application of a positive potential and eliminate neutral Fe3O4-Au-PNA complex. To detect miRNA in complicated samples, a magnet has been used to separate Fe3O4-Au-PNA-miRNA complex with good selectivity. We think this is a facile and effective method for the detection of different targets at single molecular level, including nucleic acids, proteins, and other small molecules, which will open up a new approach in the nanopore sensing field.

AuPd-Fe3 O4 Nanoparticle-Catalyzed Synthesis of Furan-2,5-dimethylcarboxylate from 5-Hydroxymethylfurfural under Mild Conditions.

Efficient one-pot oxidative esterification of 5-hydroxymethylfurfural (HMF) to furan-2,5-dimethylcarboxylate (FDMC) was achieved under extremely mild reaction conditions by using AuPd alloy nanoparticles (NPs) supported on Fe3 O4 . A high yield of FDMC (92 %) was obtained at room temperature under atmospheric O2 . The reaction proceeded through the synergistic effects of the AuPd heterobimetallic catalyst system. The most effective molar ratio of noble metal contents for HMF oxidation was 1.00:1.18. If Au-Fe3 O4 NPs were used as the catalyst, selective synthesis of 5-hydroxymethylfuroic acid methyl ester (HMFE) was achieved. Additionally, the AuPd-Fe3 O4 catalyst could be successfully reused.

A Facile One-Pot Synthesis of Water-Soluble, Patchy Fe3O4-Au Nanoparticles for Application in Radiation Therapy

A facile one-pot synthesis route for the preparation of water-soluble, biocompatible patchy Fe3O4-Au nanoparticles (Fe3O4-Au pNPs) was developed. Biocompatibility was attained through surface functionalization with 1-methyl-3-(dodecylphosphonic acid) imidazolium bromide. The morphology, composition, crystal structure and magnetic properties of the Fe3O4-Au pNPs were investigated by conducting experiments with transmission electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction and superconducting quantum interference device, respectively. Internalization of the Fe3O4-Au pNPs by MCF-7 cells occurred via endocytosis. The performance of the Fe3O4-Au pNPs as X-ray radiosensitizer in tumor cells was compared with that of gold nanocluster and Fe3O4 NPs. For this reason, MCF-7, A549 and MCF-10A cells were loaded with the respective kind of nanoparticles and treated with X-rays at doses of 1, 2 or 3 Gy. The nanoparticle-induced changes of the concentration of the reactive oxygen species (ROS) were detected using specific assays, and the cell survival under X-ray exposure was assessed employing the clonogenic assay. In comparison with the gold nanocluster and Fe3O4 NPs, the Fe3O4-Au pNPs exhibited the highest catalytic capacity for ROS generation in MCF-7 and A549 cells, whereas in the X-ray-induced ROS formation in healthy MCF-10A cells was hardly enhanced by the Fe3O4 NPs and Fe3O4-Au pNPs. Moreover, the excellent performance of Fe3O4-Au pNPs as X-ray radiosensitizers was verified by the quickly decaying radiation dose survival curve of the nanoparticle-loaded MCF-7 and A549 cells and corroborated by the small values of the associated dose-modifying factors.

Synthesis of core-shell Fe3O4-Au nanoparticles by electrical exploding wire technique combined with laser pulse shooting

Fe3O4-Au core-shell nanoparticles were synthesized in two steps; electro- exploding of Au wire in Fe3O4 colloidal solution nanoparticles and then shooting these nanoparticles by laser pulses. Structural properties of these nanoparticles were examined using X-ray diffraction (XRD) and transmission electron microscopy (TEM). XRD study revealed the gradual covering of the Fe3O4 by Au nanoparticles depending on the Au exploding wire current and the laser pulse power density. TEM image analysis revealed their spherical shapes with a narrow size distribution, besides the dramatic change in the average particle size due to the variation in laser pulse power density. Furthermore, UV–Visible optical absorption spectroscopy indicated the deviation of the Au surface plasmon resonance peaks with the Au exploding wire current besides the laser pulse power density, which affected the shell thickness.

Magnetic nanoparticles as a support for a copper (II) complex with nuclease activity

Magnetic nanoparticles have been extensively explored for the development of platforms for drug delivery and imaging probes. In this work, we have used a modular capping strategy to produce magnetic gold-coated Fe3O4 (Fe3O4@Au) nanoparticles, which have been decorated with a copper (II) complex containing a thioether derivative of clip-phen (Fe3O4@Au@Cu), where the complex [Cu(2CP-Bz-SMe)]2+ has affinity to bind DNA and proven nuclease activity (2CP-Bz-SMe=1,3-bis((1,10-phenanthrolin-2-yl)oxy)-N-(4-(methylthio)benzylidene)propan-2-imine). The functionalization of Fe3O4@Au with the copper complex occurs through the sulfur atom of the thioether moiety, as indicated by Raman scattering on surface. The magnetic measurements showed the nanomaterial Fe3O4@Au@Cu is still magnetic although the gold shell and the functionalization with the copper complex have diminished the magnetization due to the dilution of the magnetic core. The nuclease assays performed with Fe3O4@Au@Cu indicate that the nuclease activity of the nanomaterial toward the plasmid DNA involves an oxidative pathway in which H2O2 species is involved as intermediate in a Fenton-like reaction. Based on the electron paramagnetic resonance spectra (aN = 15.07 G, aH = 14.99 G), such nuclease activity is assigned, essentially, to the HO species indicating that the radical production property of [Cu(2CP-Bz-SMe)]2+ is successfully transferred to the core-shell gold-coated Fe3O4 magnetic nanoparticles. To the best of our knowledge, this is the first study reporting nuclease activity due to the reactive oxygen species generated by a copper complex immobilized on a gold-coated magnetic nanoparticle.

Structure, magnetic and cytotoxic behaviour of solvothermally grown Fe3O4@Au core-shell nanoparticles

Magnetic nanoparticles (MNPs) have demonstrated their potential in a wide variety of biomedical applications including in tumour hyperthermia. However, highly reactive nature and aggregation affinity of these nanostructures are the principal limitations for such applications. To overcome these limitations, those MNPs should be covered with an inert shell in order to protect the magnetic core against chemical alterations. Considering the noble, chemically inert nature of gold, which also has good biocompatibility, we fabricated chemically stable gold-coated Fe3O4 (Fe3O4@Au) nanoparticles of 20–50 nm size range with considerable saturation magnetization, though a simple one-pot solvothermal method. The morphology, elemental distribution and the structure of the core-shell nanoparticles were characterized using aberration-corrected (Cs) Scanning transmission electron microscopy (STEM), and compared with their simulated images. Cytotoxicity assay in MDCK cell line was performed to evaluate the biocompatibility of the nanoparticles. The results showed higher cell viability for the Fe3O4@Au nanoparticles, suggesting their good biocompatibility and potentials for biomedical applications.

Synthesis of nanocomposites of iron oxide/gold (Fe3O4/Au) loaded on activated carbon and their application in water treatment by using sonochemistry: Optimization study

This paper focuses on the finding best operational conditions using response surface methodology (RSM) for Rhodamine123 (R123) and Disulfine blue (DSB) dyes removal by ultrasound assisted adsorption onto Au-Fe3O4 nanoparticles loaded on activated carbon (Au-Fe3O4 NPs-AC). The influences of variables such as initial R123 (X1) and DSB concentration (X2), pH (X3), adsorbent mass (X4) and sonication time (X5) on their removal were investigated by small central composite design (CCD) under response surface methodology. The significant variables and the possible interactions among variables were investigated and estimated accordingly. The best conditions were set as: 4min, 4.0, 0.025g, 13.5 and 26.5mgL−1 for sonication time, pH, adsorbent weight, initial R123 and DSB concentration, respectively. At above conditions, the adsorption equilibrium and kinetic follow the Langmuir isotherm and pseudo-second-order kinetic model, respectively. The maximum monolayer capacity (Qmax) of 71.46 and 76.38mgg−1 for R123 and DSB show sufficiency of model for well presentation of experimental data.

Block copolymer conjugated Au-coated Fe3O4 nanoparticles as vectors for enhancing colloidal stability and cellular uptake

BackgroundPolymer surface-modified inorganic nanoparticles (NPs) provide a multifunctional platform for assisting gene delivery. Rational structure design for enhancing colloidal stability and cellular uptake is an important strategy in the development of safe and highly efficient gene vectors.ResultsHeterogeneous Au-coated Fe3O4 (Fe3O4@Au) NPs capped by polyethylene glycol-b-poly1-(3-aminopropyl)-3-(2-methacryloyloxy propylimidazolium bromine) (PEG-b-PAMPImB-Fe3O4@Au) were prepared for DNA loading and magnetofection assays. The Au outer shell of the NPs is an effective platform for maintaining the superparamagnetism of Fe3O4 and for PEG-b-PAMPImB binding via Au–S covalent bonds. By forming an electrostatic complex with DNA at the inner PAMPImB shell, the magnetic nanoplexes offer steric protection from the outer corona PEG, thereby promoting high colloidal stability. Transfection efficiency assays in human esophageal cancer cells (EC109) show that the nanoplexes have high transfection efficiency at a short incubation time in the presence of an external magnetic field, due to increased cellular internalization via magnetic acceleration. Finally, after transfection with the magnetic nanoplexes EC109 cells acquire magnetic properties, thus allowing for selective separation of transfected cells.ConclusionPrecisely engineered architectures based on neutral-cationic block copolymer-conjugated heterogeneous NPs provide a valuable strategy for improving the applicability and efficacy of synthesized vectors.

Photo-controlled aptamers delivery by dual surface gold-magnetic nanoparticles for targeted cancer therapy

Dual surfaced dumbbell-like gold magnetic nanoparticles (Au-Fe3O4) were synthesized for targeted aptamers delivery. Their unique biological properties were characterized as a smart photo-controlled drug carrier. DNA aptamers targeting vascular endothelial growth factor (VEGF) were assembled onto the surface of Au-Fe3O4 by electrostatic absorption. The binding capacity of the nanoparticles with VEGF aptamers was confirmed by gel electrophoresis. The targeted recognization of ovarian cancer cells by the aptamers-functionalized Au-Fe3O4 nanoparticles (Apt-Au-Fe3O4 NPs) was observed by confocal microscopy. Apt-Au-Fe3O4 was found to bind with SKOV-3 ovarian cancer cells specifically, leading to marked intracellular release of aptamers upon plasmon-resonant light (605nm) radiation, and to enhance the in vitro inhibition against tumor cell proliferation. The results show high potential of Apt-Au-Fe3O4as a targeted cancer hyperthermia carrier by remote control with high spatial/temporal resolution.

Solvothermal Synthesis of Surface-Modified Graphene/C and Au-Fe3O4 Nanomaterials for Antibacterial Applications

We have investigated synthesis of simultaneously surface-modified Graphene/C, and Au-Fe3O4 nanomaterials by using the simple solvothermal method: synthesis was carried out inside stainless steel autoclave, under temperatures 150°C - 170°C and pressure 1.5-1.8 MPa. No gas was used, and no pollutants were produced during synthesis. Varied synthesis conditions (temperature, time and concentration of initial reagents) allow us control and achieving nanomaterials with different structure and properties. Solvothermal synthesis mechanism of above nanoparticles have been described and explained in this work. Structure, morphology and phase compositions of as-synthesized nanoparticles were thoroughly characterized and analyzed by X-ray photoelectron, Raman, high resolution transmission electron microscopy and energy dispersive X-ray analyses. ATR-FTIR spectra observed peaks at 1310-1335 cm-1, characterizing Va asymmetric, and peaks at 1130-1160 cm-1 for Vs symmetric valence vibrations for alkyl sulfone (-SO2) functional groups, released from SLS (sodium lauryl sulfate) surfactant and modified the Graphene surface. Distinct antibacterial activity of Au-Fe3O4 nanoparticles, increasing by increase in Au-Fe3O4 NPs concentration was established by 3M E.coli Pertifilm count plates.

Preparation of Magnetic Nanoparticles for Biomedical Applications.

Magnetic nanoparticles have obtained great attention in the field of biomedicine in recent years owing to their excellent biocompatibility, unique magnetic properties, and ease of functionalization. Potential applications for functionalized magnetic nanoparticles span biomedical imaging, treatment via magnetic hyperthermia, drug delivery, and biosensing. This chapter provides detailed procedures for the synthesis, PEGylation, and bioconjugation of monodispersed Fe3O4 nanoparticles, hollow Fe3O4 nanoparticles, porous hollow Fe3O4 nanoparticles, and dumbbell-like Au-Fe3O4 nanoparticles. We hope this article can help readers design and reproducibly prepare high-quality magnetic nanoparticles with their specific goals in mind.

Targeted chimera delivery to ovarian cancer cells by heterogeneous gold magnetic nanoparticle

Efficient delivery of small interfering RNAs (siRNAs) to the targeted cells has remained a significant challenge in clinical applications. In the present study, we developed a novel aptamer–siRNA chimera delivery system mediated by cationic Au-Fe3O4 nanoparticles (NPs). The chimera constructed by VEGF RNA aptamer and Notch3 siRNA was bonded with heterogeneous Au-Fe3O4 nanoparticles by electrostatic interaction. The obtained complex exhibited much higher silencing efficiency against Notch3 gene compared with chimera alone and lipofectamine-siRNA complex, and improved the antitumor effects of the loaded chimera. Moreover, the efficient delivery of the chimera by Au-Fe3O4 NPs could reverse multi-drug resistance (MDR) of ovarian cancer cells against the chemotherapeutic drug cisplatin, indicating its potential capability for future targeted cancer therapy while overcoming MDR.

Preparation and catalytic properties of magnetic rectorite-chitosan-Au composites

A novel composite was assembled by introducing magnetic Fe3O4 nanoparticles, chitosan and Au nanoparticles (AuNPs) on rectorite (REC) surfaces. The obtained REC-Fe3O4-CTS-Au composite was characterized and used as the catalyst to remove 4-nitrophenol (4-NP) and methyl orange (MO) from water in the presence of NaBH4. The large surface of REC and the abundant hydroxyl group of chitosan on REC surface could restrain the agglomeration of AuNPs. REC-Fe3O4-CTS-Au exhibited the superiority in catalytic efficiency. At the catalyst dosage of 150 mg/L, it took only 15 min for 0.2 mM 4-NP solution to reach complete reduction, and 30 min for 1.0 mM 4-NP solution. This catalyst had the higher catalytic activity for 4-NP than MO reduction. Moreover, the catalyst could be conveniently separated and recycled from the reaction mixtures using an external magnetic field, and reused for 4-NP (or MO) reduction in fourteen cycles with retaining the original 99% (or 95%) conversion efficiency. This work indicates that REC-Fe3O4-CTS-Au can be a promising catalyst for the highly efficient degradation of organic dyes.

Magnetic chitosan-functionalized Fe3O4@Au nanoparticles: Synthesis and characterization

A simple synthesis method of chitosan functionalized Fe3O4-Au (Chit-Fe2O3@Au) nanoparticles (NPs) was developed. This method first prepared oleic acid-coated Fe3O4 (OA-Fe2O3) NPs as a precursor, followed by functionalization of chitosan to obtain Chit-Fe2O3@Au NPs. Structural and magnetic properties of both synthesized nanomaterials were examined by surface and spectroscopic techniques. An X-ray diffraction (XRD) study showed that the phases of Fe3O4 and Au had sizes of 5.9 and 11.2 nm, respectively. High resolution transmission electron microscopy (HRTEM) images demonstrated the formation of nearly spherical shaped composites in Chit-Fe3O4@Au nanostructures. Energy dispersive X-ray (EDX) spectroscopy measurements confirmed the presence of Au and Fe3O4 in the prepared nanomaterials. The capping of chitosan on Au and Fe3O4 surface was established using Fourier transform infrared (FTIR) spectroscopy measurements. Mössbauer spectra at 300 K showed an increase in superparamagnetic components. At 80 K, the Fe3O4@Au nanomaterials preserved 11% of superparamagnetic phase. Magnetization measurements revealed that the Fe3O4@Au nanomaterials had a saturation magnetization of 28 emu/g at 300 K and a blocking temperature of 117 K. The synthesized nanomaterials have potential in biomedical applications because of their high magnetic property with suitable binding sites for delivering drugs.

A bifunctional sensor based on Au-Fe3O4 nanoparticle for the detection of Cd2+

A bifunctional sensor based on Au-Fe3O4 nanoparticles (NPs) modified by ethyl 1-(2-(3′,4′-dihydroxyphenyl)-2-oxoethyl)-1H-1,2,3-triazole-4-carboxylate (ETC) was developed. Due to the coordination interaction between cadmium (Cd2+) and ETC, Cd2+ induced the aggregation of Au-Fe3O4 NPs from dispersion, concomitant with a change in UV–vis spectra and transverse relaxation time (T2). The combined signals provided high selectively for Cd2+ ions.

Synthesis and application of strawberry-like Fe3O4-Au nanoparticles as CT-MR dual-modality contrast agents in accurate detection of the progressive liver disease

Development of non-invasive assay for the accurate diagnosis of progressive liver diseases (e.g., fatty liver and hepatocellular carcinoma (HCC)) is of great clinical significance and remains to be a big challenge. Herein, we reported the synthesis of strawberry-like Fe3O4-Au hybrid nanoparticles at room temperature that simultaneously exhibited fluorescence, enhanced X-ray attenuation, and magnetic properties. The results of in vitro fluorescence assay showed that the nanoparticles had significant photo-stability and could avoid the endosome degradation in cells. The in vivo imaging of normal mice demonstrated that the Fe3O4-Au nanoparticles provided 34.61-fold contrast enhancement under magnetic resonance (MR) guidance 15 min post the administration. Computed tomography (CT) measurements showed that the highest Hounsfield Unit (HU) was 174 at 30 min post the injection of Fe3O4-Au nanoparticles. In vivo performance of the Fe3O4-Au nanoparticles was further evaluated in rat models bearing three different liver diseases. For the fatty liver model, nearly homogeneous contrast enhancement was observed under both MR (highest contrast ratio 47.33) and CT (from 19 HU to 72 HU) guidances without the occurrences of focal nodules or dysfunction. For the cirrhotic liver and HCC, pronounced enhancement under MR and CT guidance could be seen in liver parenchyma with highlighted lesions after Fe3O4-Au injection. Furthermore, pathological, hematological and biochemical analysis revealed the absence of acute and chronic toxicity, confirming the biocompatibility of our platform for in vivo applications. Collectively, These Fe3O4-Au nanoparticles showed great promise as a candidate for multi-modality bio-imaging.

Dumbbell-like Au-Fe3O4 nanoparticles: a new nanostructure for supercapacitors.

Monodispersed dumbbell-like Au-Fe3O4 nanoparticles (NPs) were synthesized and studied for use in supercapacitors. These dumbbell NPs show Au/Fe3O4-size dependent capacitive behaviors and the 7-14 nm Au-Fe3O4 NPs have the best specific capacitance of 464 F g(-1) at 1 A g(-1) and capacity retention of 86.4% after 1000 cycles, much larger than pure Fe3O4 NPs (160 F g(-1) and 72.8% retention). This capacitive enhancement is believed to arise from the Au-induced increase in electron transfer across the dumbbell-like NPs. Thise report demonstrates a new strategy to enhance oxide NP capacitance for applications in high performance supercapacitors.