As a low molecular weight protein with the ability of binding metal ions and high inducibility, metallothionein (MT) is often regarded as an important biomarker for assessment of heavy metal pollution in water environment. In the light of that the traditional process of enrichment and identification is time-consuming and complicated, we prepared a core-shell nanoparticle, gold-coated iron oxide nanoparticles (Fe3O4@Au NPs) herein. It possessed the advantages of fast response to magnetic fields and optical properties attributing to Fe3O4 and Au nanoparticles, respectively. The Fe3O4@Au nanoparticles could be used to enrich MT simply through Au–S interaction, and the purified proteins were determined by matrix assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF/MS). The results showed that the Fe3O4@Au nanoparticles could directly enrich MT from complex solutions and the detection limit could be as low as 10 fg mL?1. 相似文献
Several methods and materials have been explored for the sensitive and practicable detection of polycyclic aromatic hydrocarbons (PAHs). However, it is still a challenge to develop simple and cost-effective sensing techniques for PAHs. Herein we report the synthesis and construction of Fe3O4@Au SERS substrate. This magnetic substrate was composed by Fe3O4 microspheres and Au NPs. The size, morphology, and surface composition of Fe3O4@Au were characterized by multiple complimentary techniques including scanning electron microscopy, X-ray photoelectron spectroscopy, and X-ray powder diffraction. The spatial distributions of electro-magnetic field enhancement around Fe3O4@Au was calculated using finite difference time domain (FDTD) simulations. As a result of its remarkable sensitivity, the Fe3O4@Au-based SERS assay has been applied to detect the 16 EPA priority PAHs. The LODs achieved by our method (100–5 nM, 16.6–1.01 μg L−1) make it promising for the rapid screening of highly contaminated cases. As a proof-of-concept study, the substrate was applied in SERS sensing of PAHs in river matrix. The 16 PAHs could be differentiated based upon their characteristic SERS peaks. Most importantly, the detection was successfully conducted using a portable Raman spectrometer, which could be used for on-site monitoring of PAHs. 相似文献
Hierarchical Fe3O4@poly(4‐vinylpyridine‐co‐divinylbenzene)@Au (Fe3O4@P(4‐VP–DVB)@Au) nanostructures were fabricated successfully by means of a facile two‐step synthesis process. In this study, well‐defined core–shell Fe3O4@P(4‐VP–DVB) microspheres were first prepared with a simple polymerization method, in which 4‐VP was easily polymerized on the surface of Fe3O4 nanoparticles by means of strong hydrogen‐bond interactions between ? COOH groups on poly(acrylic acid)‐modified Fe3O4 nanoparticles and a 4‐VP monomer. HAuCl4 was adsorbed on the chains of a P(4‐VP) shell and then reduced to Au nanoparticles by NaBH4, which were embedded into the P(4‐VP) shell of the composite microspheres to finally form the Fe3O4@P(4‐VP–DVB)@Au nanostructures. The obtained Fe3O4@P(4‐VP–DVB)@Au catalysts with different Au loadings were applied in the reduction of 4‐nitrophenol (4‐NP) and exhibited excellent catalytic activity (up to 3025 h?1 of turnover frequency), facile magnetic separation (up to 31.9 emu g?1 of specific saturation magnetization), and good durability (over 98 % of conversion of 4‐NP after ten runs of recyclable catalysis and almost negligible leaching of Au). 相似文献
Stable magnetic nanocomposite of gold nanoparticles (Au‐NPs) decorating Fe3O4 core was successfully synthesized by the linker of Boc‐L‐cysteine. Transmission electron microscope (TEM), energy dispersive X‐ray spectroscopy (EDX) and cyclic voltammograms (CV) were performed to characterize the as‐prepared Fe3O4@Au‐Nps. The results indicated that Au‐Nps dispersed homogeneously around Fe3O4 with the ratio of Au to Fe3O4 nanoparticles as 5–10/1 and the apparent electrochemical area as 0.121 cm2. After self‐assembly of hemoglobin (Hb) on Fe3O4@Au‐Nps by electrostatic interaction, a hydrogen peroxide biosensor was developed. The Fe3O4@Au‐Nps/Hb modified GCE exhibited fast direct electron transfer between heme center and electrode surface with the heterogeneous electron transfer rate constant (Ks ) of 3.35 s−1. Importantly, it showed excellent electrocatalytic activity towards hydrogen peroxide reduction with low detection limit of 0.133 μM (S /D =3) and high sensitivity of 0.163 μA μM−1, respectively. At the concentration evaluated, the interfering species of glucose, dopamine, uric acid and ascorbic acid did not affect the determination of hydrogen peroxide. These results demonstrated that the introduction of Au‐Nps on Fe3O4 not only stabilized the immobilized enzyme but also provided large surface area, fast electron transfer and excellent biocompatibility. This facile nanoassembly protocol can be extended to immobilize various enzymes, proteins and biomolecules to develop robust biosensors. 相似文献
Orientedly bioconjugated core/shell Fe3O4@Au magnetic nanoparticles were synthesized for cell separation. The Fe3O4@Au magnetic nanoparticles were synthesized by reducing HAuCl4 on the surfaces of Fe3O4 nanoparticles, which were further characterized in detail by TEM, XRD and UV-vis spectra. Anti-CD3 monoclonal antibody was orientedly bioconjugated to the surface of Fe3O4@Au nanoparticles through affinity binding between the Fc portion of the antibody and protein A that covalently immobilized on the nanoparticles. The oriented immobilization method was performed to compare its efficiency for cell separation with the non-oriented one, in which the antibody was directly immobilized onto the carboxylated nanoparticle surface. Results showed that the orientedly bioconjugated Fe3O4@Au MNPs successfully pulled down CD3+ T cells from the whole splenocytes with high efficiency of up to 98.4%, showing a more effective cell-capture nanostructure than that obtained by non-oriented strategy. This developed strategy for the synthesis and oriented bioconjugation of Fe3O4@Au MNPs provides an efficient tool for cell separation, and may be further applied to various fields of bioanalytical chemistry for diagnosis, affinity extraction and biosensor. 相似文献
A new two-step synthesis of Fe3O4@Au core–shell nanoparticles stabilized in polyethylene glycol is described. The nanoparticles were characterized by transmission electron microscopy, X-ray powder diffraction, UV and Mössbauer spectroscopy. Fe3O4@Au nanoparticles featured both optical properties (they featured a plasmon resonance band) and magnetic properties (they responded to an external magnetic field), typical of individual gold and magnetite nanoparticles, respectively. 相似文献
An ethanol biosensor based on alcohol dehydrogenase (ADH) attached to Au seeds decorated on magnetic nanoparticles (Fe3O4@Au NPs) is presented. ADH was immobilized on Fe3O4@Au NPs, which were subsequently fixed by a magnet on a carbon paste electrode modified with 5 % (m : m) MnO2. Optimum conditions for the amperometric determination of ethanol with the biosensor were as follows: working potential +0.1 V (vs. Ag/AgCl); supporting electrolyte: 0.1 M phosphate buffer solution at pH 6.8 containing 0.25 mM of the coenzyme (NAD+); working electrode: carbon paste with magnetically attached Fe3O4@Au NPs (0.012 mg ? cm?2 electrode area) with immobilized alcohol dehydrogenase (120 units per cm2 of electrode area). Linearity between signal and concentration was found for the range from 0.1 to 2.0 M ethanol (r2=0.995) with a detection limit of 0.07 M, a sensitivity of 0.02 µA ? mM?1 ? cm?2, a reproducibility of 4.0 % RSD, and a repeatability of 2.7 % RSD. The results for the determination of ethanol in alcoholic beverages showed good agreement with gas chromatography (GC) with recovery of 96.0 – 108.8 %. 相似文献
In this time researchers make a great efforts to develop new hybrid nanoparticles for medical and pharmaceutical applications. Fe3O4‐Au hybrid heterodimers have been prepared with superior properties for various claims. Unfortunately, Fe3O4‐Au heterodimers are not stable in the physiological medium. In this study, we employed the albumin macromolecules as a stabilizer of Fe3O4‐Au hybrid nanoparticles (noted as Fe3O4‐Au‐BSA hybrid nanoparticles). After characterization of synthesized nanoparticles by FTIR, UV–Vis, TEM, DLS, DSC, VSM and XRD techniques, the in vitro and in vivo biocompatibility of these nanoparticles were also evaluated. We encountered with an amazing result which confirmed nanoparticles could be stabilized by linking the BSA on the surface of Fe3O4‐Au heterodimers. Also, intravenous injection of Fe3O4‐Au‐BSA hybrid nanoparticles up to 400 mg/kg to Balb C mice show that these nanoparticles were non‐toxic. The biocompatibility and stereological study had been performed for more than 30 days after nanoparticles administration, using hystomorphometric analysis. Remarkably, to the best of our knowledge, it was the first time the biocompatibility and biodegradability of Fe3O4‐Au were studied and evaluated by stereological technique. Further promotion and biomedical usage of this type of hybrid nanoparticles are underway in our laboratory. 相似文献
A synthetic method developed for preparation of sulfate- and carboxyl-functionalized magnetite/polystyrene (Fe3O4/PS) spheres that can be further decorated with gold (Au) nanoparticles is reported. By using emulsifier-free emulsion polymerization
based on potassium persulfate (KPS)/methyl acrylic acid (MAA)/water system in the presence of Fe3O4/PS spheres used as the seeds, PMAA-coated magnetic Fe3O4-PS spheres were readily obtained. The sulfate group is inherent in KPS for initiating the polymerization of PMAA, and eventually
it acts as the reducing agent for the deposition of Au nanoparticles. The carboxyl group, on the other hand, could seemingly
contribute to immobilize Au nanoparticles precipitated. The morphologies, magnetic properties, and characteristics of oleate-stabilized
Fe3O4 nanoparticles, Fe3O4/PS spheres, PMAA-coated Fe3O4/PS spheres, and Au-decorated resultant spheres were respectively studied using transmission electron microscopy, X-ray diffraction,
Fourier transform infrared, and superconducting quantum interference device magnetometer. 相似文献
A pseudo-homogeneous immunoextraction method based on gold-coated magnetic nanoparticles (MNPs) for the specific extraction and quantitative analysis of epitestosterone (17α-hydroxy-4-androsten-3-one, abbreviated as “ET”) from human urine samples by high-performance liquid chromatography (HPLC) has been developed. Half-IgG of anti-ET monoclonal antibodies were covalently immobilized onto (Fe3O4)core-Aushell (Fe3O4@Au) MNPs. An external magnetic field was applied to collect the MNPs which were then rinsed with distilled water followed by elution with absolute methanol to obtain ET as the analyte. The obtained extraction solution was analyzed by HPLC with UV detection (244 nm) within 12 min. The standard calibration curve for ET showed good linearity in the range of 20-200 ng mL−1 in phosphate-buffered saline (PBS) solutions with acceptable accuracy and precision. Limit of detection for ET was 0.06 ng mL−1 due to an enrichment factor of 100-fold was achieved. The results obtained by the present method for spiked human urine samples were in agreement with those from indirect competitive enzyme-linked immunoadsorbent assays (ELISAs). The antibody-conjugated Fe3O4@Au MNPs are novel materials for immunoaffinity extraction. Compared with the conventional technique using immunoaffinity column, the method described here for sample pretreatment was fast, highly specific, and easy to operate. 相似文献
Triclosan is broadly utilized as preservative or antiseptic in various cosmetic and personal care products. It becomes hazardous for environmental safety and human health more than a certain concentration. In this research, graphene oxide (GO) nanosheets were prepared by composing Fe3O4@Au nanostructure decorated GO together with polypyrrole (PPy) (Fe3O4@Au‐PPy/GO nanocomposite) in a facile way. The composite excellent increased the electrochemical response, presenting a high sensitive electrochemical method for triclosan detection. The synthesized Fe3O4@Au‐PPy/GO nanocomposite was characterized for its morphological, magnetically and structural properties by FESEM‐mapping, TEM, and XRD. The Fe3O4@Au‐PPy/GO nanocomposites modified glassy carbon electrodes (GCE), Fe3O4@Au‐PPy/GO GCE, showed a higher sensitivity good stability, reproducibility, lower LOD (2.5×10?9 M) and potential practical application in electrochemical detection of triclosan under optimized experimental conditions. 相似文献
Core-shell nanostructures of silicon oxide@noble metal have drawn a lot of interest due to their distinctive characteristics and minimal toxicity with remarkable biocompatibility. Due to the unique property of localized surface plasmon resonance (LSPR), plasmonic nanoparticles are being used as surface-enhanced Raman scattering (SERS) based detection of pollutants and photothermal (PT) agents in cancer therapy. Herein, we demonstrate the synthesis of multifunctional silica core – Au nanostars shell (SiO2@Au NSs) nanostructures using surfactant free aqueous phase method. The SERS performance of the as-synthesized anisotropic core-shell NSs was examined using Rhodamine B (RhB) dye as a Raman probe and resulted in strong enhancement factor of 1.37×106. Furthermore, SiO2@Au NSs were also employed for PT killing of breast cancer cells and they exhibited a concentration-dependent increase in the photothermal effect. The SiO2@Au NSs show remarkable photothermal conversion efficiency of up to 72 % which is unprecedented. As an outcome, our synthesized NIR active SiO2@Au NSs are of pivotal importance to have their dual applications in SERS enhancement and PT effect. 相似文献
In this paper, a kind of splat-shaped Fe3O4/Au nanocomposites was synthesized. The magnetic resonance imaging/surface-enhanced Raman scattering (MRI/SERS) studies demonstrated that as-synthesized Fe3O4/Au nanocomposites may be a promising MRI/SERS dual probe for the tumor detection. 相似文献
The authors describe a sensitive surface-enhanced Raman scattering (SERS)-based aptasensor for the detection of the food pathogen Vibrio parahaemolyticus. Nanostructures consisting of Fe3O4@Au particles wrapped with graphene oxide (GO) were used both as SERS substrates and separation tools. A first aptamer (apt 1) was immobilized on the Fe3O4@Au/GO nanostructures to act as a capture probe via the affinity binding of aptamer and V. parahaemolyticus. A second aptamer (apt-2) was modified with the Raman reporter molecule TAMRA to act as a SERS sensing probes that binds to the target the same way as the Fe3O4@Au/GO-apt 1. The sandwich formed between Fe3O4@Au/GO-apt 1/V. parahaemolyticus and apt 2-TAMRA can be separated with the aid of a magnet. The concentration of V. parahaemolyticus can be quantified by measurement of the SERS intensity of TAMRA. Under optimal conditions, the signal is linearly related to the V. parahaemolyticus concentration in the range between 1.4 × 102 to 1.4 × 106 cfu·mL?1, with a detection limit of 14 cfu·mL?1. Recoveries ranging from 98.5% to 105% are found when analyzing spiked salmon samples. In our perception, the assay described here is a useful tool for quantitation of V. parahaemolyticus in real samples.
Graphical abstract GO wrapped Fe3O4@Au nanostructures were synthesized as the substrate and modified with with a first aptamer (apt 1) to capture V. parahaemolyticus. TAMRA labelled aptamer 2 was then used as signal probe. The V. parahaemolyticus concentrations are closely related to the Raman intensity of TAMRA.
Enhancement of Fe3O4 /Au nanoparticles (Fe3O4 /Au NPs ) catalyst was observed in the oxidative degradation of methyl orange by employing H2O2 as oxidant. To evaluate the catalytic activity of Fe3O4 /Au nanoparticles, different degradation conditions were investigated such as the amounts of catalyst, H2O2 concentration and pH value. Based on our data, methyl orange was degraded completely in a short time. The enhanced catalytic activity and increased oxidation rate constant may be ascribed to synergistic catalyst‐activated decomposition of H2O2 to •OH radical, which was one of the strong oxidizing species. Besides, Fe3O4 /Au nanoparticles have exhibited satisfying recycle performance for potential industrial application. 相似文献
Small molecules or analytes present at low concentrations are difficult to detect directly using conventional surface plasmon resonance (SPR) techniques because only small changes in the refractive index of the medium are typically induced by the binding of these analytes. Here, we present an amplification technique using core–shell Fe3O4@Au magnetic nanoparticles (MNPs) for an SPR bioassay. To evaluate this amplification effect, a novel SPR sensor based on a sandwich immunoassay was developed to detect α-fetoprotein (AFP) by immobilizing a primary AFP antibody (Ab1) on the surface of a 3-mercapto-1-propanesulfonate/chitosan-ferrocene/Au NP (MPS/CS-Fc/Au NP) film employing Fe3O4@Au–AFP secondary antibody conjugates (Fe3O4@Au–Ab2) as the amplification reagent. The stepwise fabrication of the biosensor was characterized using UV-vis spectroscopy, electrochemical impedance spectroscopy, and cyclic voltammetry. A calibration curve of Fe3O4@Au–Ab2 conjugates amplification for AFP detection was obtained to yield a correlation in the range of 1.0–200.0 ng mL−1 with a detection limit of 0.65 ng mL−1, and a significant increase in sensitivity was therefore afforded through the use of Fe3O4@Au–Ab2 conjugates as an amplifier. This magnetic separation and amplification strategy has great potential for the detection of other biomolecules of interest with low interference and high sensitivity by changing the antibody label used in the Fe3O4@Au–antibody conjugates. 相似文献
Multifunctional materials have become the development trend of current material preparation. We reported a typical layer-by-layer method for the fabrication of multifunctional Fe3O4@mTiO2@noble metal triplex core-shell composite nanoparticle (NP), which is composed of a magnetic Fe3O4 particle as the core, a mesoporous TiO2 interlayer and a layer of Ag nanoparticles or Au nanorods as the shell. The obtained Fe3O4@mTiO2@noble metal composite NPs have shown excellent surface enhanced Raman scattering (SERS) sensitivity. Raman results present that the limit of detection (LOD) for crystal violet (CV), p-aminothiophnol (p-ATP) and p-mercaptobenzoic acid (p-MBA) of the Fe3O4@mTiO2@noble metal composite NPs substrates are as low as 1.0 × 10−9 M, 1.0 × 10−12 M and 1.0 × 10−9 M, respectively. In addition, the composite NPs also show high reproducibility and stability across the entire area with relative standard deviations (RSD) less than 15.00%. These highly sensitivity with good reproducibility can be attributed to the presence of plentiful “hot spots” produced by magnetic aggregation and target molecules enrichment by mesoporous TiO2 adsorption for practical application. Fe3O4@mTiO2@Ag composite NPs were used for thiram detection and the detection limit can reach to 5.0 × 10−8 M (about 0.012 ppm), which is lower than the maximal residue limit of 7 ppm in fruit prescribed by the U.S. Environmental Protection Agency. These multifunctional composite NPs provide easy separation, enrichment and trace detection of the analyte, exhibiting a great prospect as a potential SERS sensor in complex environments. 相似文献
Au‐Fe3O4 nanoparticles were widely used as nanoplatforms for biologic applications through readily further functionalization. Dopamine (DA)‐coated superparamagnetic iron oxide (SPIO) nanoparticles (DA@Fe3O4) have been successfully synthesized using a one‐step process by modified coprecipitation method. Then 2–3 nm gold nanoparticles were easily conjugated to DA@Fe3O4 nanoparticles by the electrostatic force between gold nanoparticles and amino groups of dopamine to afford water‐soluble Au‐Fe3O4 hybrid nanoparticles. A detailed investigation by dynamic light scatting (DLS), transmission electron microscopy (TEM), fourier transform infrared (FT‐IR) and X‐ray diffraction (XRD) were performed in order to characterize the physicochemical properties of the hybrid nanoparticles. The hybrid nanoparticles were easily functionalized with a targeted small peptide A54 (AGKGTPSLETTP) and fluorescence probe fluorescein isothiocyanate (FITC) for liver cancer cell BEL‐7402 imaging. This simple approach to prepare hybrid nanoparticles provides a facile nanoplatform for muti‐functional derivations and may be extended to the immobilization of other metals or bimolecular on SPIO surface. 相似文献