Multifunctional Ag@Au@ phenol formaldehyde resin (PFR) particles loaded with folic acids (FA) have been designed for killing tumor cells through photothermy conversion under the irradiation of near-infrared (NIR) light. Possessing the virtue of good fluorescence, low toxicity, and good targeting, the nanocomposite consists of an Ag core, an Au layer, a PFR shell, and folic acids on the PFR shell. The Ag@PFR core-shell structure can be prepared with a simple hydrothermal method after preheating. We then filled the PFR shell with a layer of Au by heating and modified the shell with polyelectrolyte to change its surface charge state. To capture tumor cells actively, FA molecules were attached onto the surface of the Ag@Au@PFR particles in the presence of 1-ethyl-3-(3-dimethly aminopropyl) carbodiimide (EDAC) and N-hydroxysuccinimide (NHS). Owing to the excellent property of Au NPs and Ag NPs as photothermal conversion agents, the Ag@Au@ PFR@FA particles can be utilized to kill tumor cells when exposed to NIR light. 相似文献
Plasmonic Au and magnetic Fe are coupled into uniform Au@Fe core–shell nanoparticles (NPs) to confirm that electron transfer occurred from the Au core to the Fe shell. Au NPs synthesized in aqueous medium are used as seeds and coated with an Fe shell. The resulting Au@Fe NPs are characterized by using various analytical techniques. X‐ray photoelectron spectroscopy and superconducting quantum interference device measurements reveal that the Fe shell of the Au@Fe NPs mainly consists of paramagnetic Wüstite with a thin surface oxide layer consisting of maghemite or magnetite. Electron transfer from the Au core to the Fe shell effectively suppresses iron oxidation from Fe2+ to Fe3+ near the interface between the Au and the Fe. The charge‐transfer‐induced electronic modification technique enables us to control the degree of iron oxidation and the resulting magnetic properties. 相似文献
Uniform Fe3O4 nanospheres with a diameter of 100 nm were rapidly prepared using a microwave solvothermal method. Then Fe304/polypyrrole (PPy) composite nanospheres with well-defined core/shell structures were obtained through chemical oxidative polymerization of pyrrole in the presence of Fe3O4; the average thickness of the coating shell was about 25 nm. Furthermore, by means of electrostatic interactions, plentiful gold nanoparticles with a diameter of 15 nm were assembled on the surface of Fe3O4/PPy to get Fe3O4/PPy/Au core/shell/shell structure. The morphology, structure, and composition of the products were characterized by transmission electronic microscopy (TEM), scanning electronic microscopy (SEM), X-ray powder diffraction (XRD), and Fourier transform infrared (FT-IR) spectroscopy. The resultant nanocomposites not only have the magnetism of Fe3O4 nanoparticles that make the nanocomposites easily controlled by an external magnetic field but also have the good conductivity and excellent electrochemical and catalytic properties of PPy and Au nanoparticles. Furthermore, the nanocomposites showed excellent electrocatalytic activities to biospecies such as ascorbic acid (AA). 相似文献
In this paper, a sensitive and specific fluorescence resonance energy transfer (FRET) aptasensor for the detection of Ochratoxin A (OTA) was developed based on a dye-tagged ssDNA hybridized with aptamer-conjugated Au nanoparticles (Au NPs). The binding between the aptamer-Au NPs conjugate and the dye-labeled ssDNA leads to the fluorescence quenching of FAM due to its close proximity. The addition of OTA results in fluorescence recovery, attributed to the formation of a quadruplex-OTA complex, which detaches from the surface of Au NPs. Under optimal conditions, the relative fluorescence intensity (ΔI) is proportional to the concentration of the OTA in the range of 5 × 10?12 to 5 × 10?9 g/mL, with a detection limit of 2 × 10?12 g/mL. The proposed method was successfully applied to measure the concentration of OTA in naturally contaminated maize samples and validated using a commercially available enzyme-linked immunosorbent assay (ELISA) method. This work demonstrates that the combination of an aptamer that has a high binding affinity for the analyte with highly sensitive Au NPs that undergo FRET is a promising approach for the detection of small molecule toxins. 相似文献
A simple, rapid and sensitive fluorescence resonance energy transfer (FRET) method is presented for the determination of thiols. It is based on the thiol-induced enhancement effect of the surfactant sodium dodecyl sulfate (SDS) on the efficiency of fluorescence resonance energy transfer (FRET) in nanospheres consisting of a magnetic (Fe3O4) core and a phenol-formaldehyde resin (PFR) shell containing gold nanoparticles (AuNPs). The luminescence of the core-shell nanospheres at excitation/emission wavelengths of 390/445 nm, respectively, is quenched by the AuNPs which act as energy acceptors. The interaction of AuNPs with thiol compounds in the presence of SDS suppresses FRET and gives rise to a fluorescent signal whose intensity is proportional to the thiol concentration. The analytical features of seven thiols (homocysteine, thioglycolic acid, glutathione, dodecanethiol, cysteamine, cysteine and N-acetylcysteine) were studied. Detection limits are in the range from 0.14 to 0.49 μmol L−1. The precision of the method, expressed as the relative standard deviation, ranges from 0.4 to 4.9 %. The method was applied to the determination of total thiols in water samples with recovery values between 88.7 and 104.6 %.
In this study, we reported a sensitive fluorescent biosensor for detection of DNA hybridization based on Fe/Au core/shell (Fe@Au) nanoparticles (NPs). First, Fe@Au NPs were synthesized using a reverse micelle method, with gold as the shell and iron as the core. The nanoparticle size was confirmed by transmission electron microscopy (TEM). Scanning electron microscopy (SEM) was performed in order to elucidate the morphology of the Fe@Au NPs. Then probe DNA with -SH at the 5'-phosphate end was covalently immobilized onto the surface of the Fe@Au NPs. The DNA hybridization event can be detected by a fluorescent method and methylene blue (MB) as the fluorescent probe. The decline of the fluorescence intensity of MB (ΔF) was linear with the concentration of the complementary DNA from 3.0 × 10(-13) to 1.0 × 10(-9) M with a detection limit of 1.0 × 10(-13) M (S/N = 3). In addition, this approach of DNA detection exhibited excellent selectivity, even for single-mismatched DNA detection. 相似文献
Monodispersed cobalt nanoparticles (NPs) with controllable size (8–14 nm) have been synthesized using thermal decomposition of dicobaltoctacarbonyl in organic solvent. The as-synthesized high magnetic moment (125 emu/g) Co NPs are dispersible in various organic solvents, and can be easily transferred into aqueous phase by surface modification using phospholipids. However, the modified hydrophilic Co NPs are not stable as they are quickly oxidized, agglomerated in buffer. Co NPs are stabilized by coating the MFe2O4 (M=Fe, Mn) ferrite shell. Core/shell structured bimagnetic Co/MFe2O4 nanocomposites are prepared with tunable shell thickness (1–5 nm). The Co/MFe2O4 nanocomposites retain the high magnetic moment density from the Co core, while gaining chemical and magnetic stability from the ferrite shell. Compared to Co NPs, the nanocomposites show much enhanced stability in buffer solution at elevated temperatures, making them promising for biomedical applications. 相似文献
A method for synthesizing composite nanoparticles with a gold shell, an Fe3O4 inner shell, and a silica core has been developed. The approach utilizes positively charged amino-modified SiO2 particles as templates for the assembly of negatively charged 15 nm superparamagnetic water-soluble Fe3O4 nanoparticles. The SiO2-Fe3O4 particles electrostatically attract 1-3 nm Au nanoparticle seeds that act in a subsequent step as nucleation sites for the formation of a continuous gold shell around the SiO2-Fe3O4 particles upon HAuCl4 reduction. The three-layer magnetic nanoparticles, when functionalized with oligonucleotides, exhibit the surface chemistry, optical properties, and cooperative DNA binding properties of gold nanoparticle probes, but the magnetic properties of the Fe3O4 inner shell. 相似文献
Herein, we prepared four samples, namely gold/poly(sodium-p-styrenesulfonate) (Au/PSS), gold/silicon dioxide (Au/SiO2), gold/titanium dioxide (Au/TiO2), and gold/cuprous oxide (Au/Cu2O) core/shell nanocomposites, to investigate how the surrounding medium affects the ultrafast plasmon dynamics of Au nanoparticles (NPs). We recorded femtosecond transient absorption spectra of Au NPs in Au/PSS, Au/SiO2, Au/TiO2, and Au/Cu2O core/shell nanocomposites at various time delays. We found that the spectral features in the femtosecond transient absorption spectra of Au NPs in Au/TiO2 and Au/Cu2O core/shell nanocomposites were dramatically different from those of Au NPs in Au/PSS and Au/SiO2 core/shell nanocomposites. A comprehensive analysis of the ultrafast plasmon dynamics of Au NPs in the core/shell nanocomposites revealed that following excitation of the resonance plasmon band of Au NPs, the exited electrons could be efficiently transferred into the conduction bands of TiO2 and Cu2O in Au/TiO2 and Au/Cu2O core/shell nanocomposites. 相似文献
The Fe(3)O(4)/(sodium oleic acid/ethyltrimethyl ammonium bromide)(n)/4-aminobenzoic acid (Fe(3)O(4)/(NaOL/CTAB)(n)/PABA) nanocomposites have been prepared by a layer-by-layer self-assembly approach. This kind of nanocomposites have fluorescent, magnetic and water-soluble properties. Taking advantage of the magnetic property of nanocomposites, we can separated them from solution easily by using a permanent magnet. By using their strong fluorescence, we can detect proteins. At pH 6.98, the fluorescence of Fe(3)O(4)/(NaOL/CTAB)(n)/PABA nanocomposites can be enhanced by the proteins. Under optimal conditions, the linear ranges of calibration curves were 0.2-20, 0.2-13, 0.2-10 microg mL(-1) for gamma-globulin (gamma-IgG), human serum albumin (HSA), and bovine serum albumin (BSA), respectively. The detection limits were 0.02, 0.01, 0.02 for gamma-IgG, HSA and BSA, respectively. The method has been applied to analyze the total proteins in human samples and the results were in good agreement with those reported by the hospital. This method is sensitive, simple and potential in many areas. 相似文献
In this study, we used photoluminescence (PL) quenching and transmission electron microscopy (TEM) to study the morphological behavior of hydrogen-bonded (H-bonded) supramolecular assemblies of luminescent H-acceptor polymers and H-donor gold nanoparticles (Au NPs). In fluorescence titration experiments, the lateral Me and MeO substituents on the fluorescent H-acceptor side-chain polymers PBOT1–PBOT3 and PBT1–PBT3 exhibited different electron-donating capabilities, thereby inducing different degrees of H-bonding and dipole–dipole interactions, as evidenced by effective fluorescence quenching upon the addition of surface-modified Au NPs bearing acid and acid-free surfactants (AuSCOOH and AuSC10, respectively). Among all of our tested nanocomposites, the highest Stern–Volmer quenching constant (KSV) was that obtained from the assembly of AuSCOOH with the homopolymer PBOT1. In addition, we developed fittable exponential equations to predict the values of KSV of other fluorescent polymers (containing various molar ratios of pyridyl conjugated units) when titrated with these NP quenchers. The morphologies observed in the TEM images confirmed that fluorescence quenching resulted from the self-assembly of the supramolecular nanocomposites, mediated by H-bonds between the fluorescent H-acceptors of the polymers and the H-donors of the Au NPs presenting acid-modified surfactants. 相似文献
The immobilization of proteins on gold-coated magnetic nanoparticles and the subsequent recognition of the targeted proteins provide an effective means for the separation of proteins via application of a magnetic filed. A key challenge is the ability to fabricate such nanoparticles with the desired core-shell nanostructure. In this article, we report findings of the fabrication and characterization of gold-coated iron oxide (Fe2O3 and Fe3O4) core@shell nanoparticles (Fe oxide@Au) toward novel functional biomaterials. A hetero-interparticle coalescence strategy has been demonstrated for fabricating Fe oxide@Au nanoparticles that exhibit controllable sizes ranging from 5 to 100 nm and high monodispersity. Composition and surface analyses have proven that the resulting nanoparticles consist of the Fe2O3 core and the Au shell. The magnetically active Fe oxide core and thiolate-active Au shell were shown to be viable for exploiting the Au surface protein-binding reactivity for bioassay and the Fe oxide core magnetism for magnetic bioseparation. These findings are entirely new and could form the basis for fabricating magnetic nanoparticles as biomaterials with tunable size, magnetism, and surface binding properties. 相似文献
We report the synthesis and characterization of a group of carboxyl-functionalized poly(amidoamine) (PAMAM) dendrimers of generation 3 (G3) that were used for the stabilization of superparamagnetic iron oxide (Fe(3)O(4)) nanoparticles (NPs). Folic acid (FA) molecules were conjugated onto the dendrimer surfaces in an attempt to achieve specific targeted imaging of tumor cells that overexpress FA receptors using dendrimer-stabilized Fe(3)O(4) NPs. Fe(3)O(4) NPs were synthesized using controlled co-precipitation of Fe(ii) and Fe(iii) ions and the formed dendrimer-stabilized Fe(3)O(4) NPs were characterized using transmission electron microscopy (TEM) and polyacrylamide gel electrophoresis (PAGE). The intracellular uptake of dendrimer-stabilized Fe(3)O(4) NPs was tested in vitro using KB cells (a human epithelial carcinoma cell line) that overexpress FA receptors. It appears that carboxyl-terminated PAMAM dendrimer-stabilized Fe(3)O(4) NPs can be uptaken by KB cells regardless of the repelling force between the negatively charged cells and the negatively charged particles. In the presence of a large amount of carboxyl terminal groups on the dendrimer surface, the receptor-mediated endocytosis of Fe(3)O(4) NPs stabilized by FA-modified dendrimers was not facilitated. It implies that the surface charge of dendrimer-stabilized magnetic iron oxide NPs in biological medium is an important factor influencing their biological performance. 相似文献
A novel luminescent and magnetic Fe(3)O(4)/pyrene/polyacrylamide (Fe(3)O(4)/Py/PAM) nanocomposite has been prepared under ultrasonic radiation. This magnetic nanocomposite combined with pyrene would lead to a special functional magnetic luminescent composite that enjoys both the advantages of magnetic nanoparticles of Fe(3)O(4) and fluorescence nanoparticles of pyrene. Taking advantage of the magnetic property of Fe(3)O(4) nanocomposites, we can separate Fe(3)O(4)/Py/PAM nanocomposites from solution easily just by using a permanent magnet. Based on the fluorescence quenching of Fe(3)O(4)/Py/PAM nanocomposites by Cr(VI), a method for the selective determination of Cr(VI), without separation of Cr(III) in water, was developed. Under optimal experimental conditions, a limit of detection of 0.01 microg mL(-1) was achieved. The calibration curve was linear over the concentration range of 0.1-14.0 microg mL(-1) with a correlation coefficient of 0.9975. The proposed method has been applied to the selective quantification of Cr(VI) in synthetic samples and wastewater samples with the satisfactory results. 相似文献
Research on Chemical Intermediates - Fe3O4@SiO2–TiCl3 NPs, a novel core shell catalyst, was synthesized via preparing Fe3O4@SiO2 as a magnetic support followed by treatment with titanium... 相似文献
The incorporation of gold nanoparticles (Au NPs) as quencher modules in fluorescent probes for DNA damage caused by intracellular hydroxyl radicals (HO*) is reported. Au NPs of 15 nm diameter were decorated with DNA oligomers terminating in thiol functions in their 3' positions and possessing 5' fluorophore modifications. The Au NPs, which have high extinction coefficients, functioned as excellent fluorescent quenchers in the fluorophore-Au NP composites. FRET is switched off as a factor of HO*-induced strand breakage in the single-stranded DNAs, restoring the fluorescence of the quenched fluorophores, which can be followed by spectrofluorimetry. In vitro assays with HO*-generating Fenton reagent demonstrated increases in fluorescence intensity with a linear range from 8.0 nM to 1.0 microM and a detection limit as low as 2.4 nM. Confocal microscopic imaging of macrophages and HepG2 revealed that the probe is cell-permeable and intracellular HO*-responsive. The unique combination of good selectivity and high sensitivity establishes the potential value of the probe for facilitating investigations of HO*-mediated cellular homeostasis and injury. 相似文献