Core-shell magnetite nanoparticles surface encapsulated with smart stimuli-responsive polymer: synthesis, characterization, and LCST of viable drug-targeting delivery system

We describe here the synthesis of a novel magnetic drug-targeting carrier characterized by a core-shell structure. The core-shell carrier combines the advantages of a magnetic core and the stimuli-responsive property of the thermosensitive biodegradable polymer shell (e.g., an on-off mechanism responsive to external temperature change). The composite nanoparticles are approximately 8 nm in diameter with approximately 3 nm shell. The lower critical solution temperature (LCST) is approximately 38 degrees C as determined by UV-vis absorption spectroscopy. The carrier is composed of cross-linked dextran grafted with a poly(N-isopropylacrylamide-co-N,N-dimethylacrylamide) [dextran-g-poly(NIPAAm-co-DMAAm)] shell and superparamagnetic Fe3O4 core. Fourier transform infrared spectroscopy (FTIR) confirmed the composition of the carrier. The synthesized magnetic carrier system has potential applications in magnetic drug-targeting delivery and magnetic resonance imaging.     

A sensitive fluorimetric biosensor for detection of DNA hybridization based on Fe/Au core/shell nanoparticles

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.     

铁氧化物/金磁性核壳纳米粒子的制备及其富集与SERS研究

本文用种子生长法制备铁氧化物/金磁性核壳纳米粒子, 并利用SERS对其磁场靶向性进行了检测.     

Gold/Wüstite Core–shell Nanoparticles: Suppression of Iron Oxidation through the Electron‐Transfer Phenomenon

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.     

Fabrication of magnetic core@shell Fe oxide@Au nanoparticles for interfacial bioactivity and bio-separation

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.     

Fe3O4/Polypyrrole/Au nanocomposites with core/shell/shell structure: synthesis, characterization, and their electrochemical properties

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).     

Interfacial deposition of Ag on Au seeds leading to AucoreAgshell in organic media

A seed mediated procedure for the synthesis of hydrophobic Au(core)Ag(shell) nanoparticles in toluene is demonstrated. The reaction proceeds by way of the interfacial reduction of silver ions by 3-pentadecylphenol followed by their deposition on hydrophobized Au nanoparticles. Such a hitherto unreported interfacial seeded growth reaction leads to the formation of phase pure Au(core)Ag(shell) nanoparticles that retain the hydrophobicity of the seed particles and remain stable in toluene. Such core-shell structures are however not formed in the aqueous phase. The core-shell architecture was verified using TEM analysis and the formation process was studied by recording the UV-vis spectra of the organic phase nanoparticles as a function of time. TEM kinetics also showed gradual increase in the silver layer thickness. Conclusive evidence was however obtained on examination of the HRTEM images of the products formed. Elemental analysis using X-ray photoelectron spectroscopy of the Au(core)Ag(shell) nanostructure revealed the presence of metallic silver. Moreover changing the surface capping of the Au seed does not affect the formation of the Au(core)Ag(shell) nanostructure.     

Monodispersed core-shell Fe3O4@Au nanoparticles

The ability to synthesize and assemble monodispersed core-shell nanoparticles is important for exploring the unique properties of nanoscale core, shell, or their combinations in technological applications. This paper describes findings of an investigation of the synthesis and assembly of core (Fe(3)O(4))-shell (Au) nanoparticles with high monodispersity. Fe(3)O(4) nanoparticles of selected sizes were used as seeding materials for the reduction of gold precursors to produce gold-coated Fe(3)O(4) nanoparticles (Fe(3)O(4)@Au). Experimental data from both physical and chemical determinations of the changes in particle size, surface plasmon resonance optical band, core-shell composition, surface reactivity, and magnetic properties have confirmed the formation of the core-shell nanostructure. The interfacial reactivity of a combination of ligand-exchanging and interparticle cross-linking was exploited for molecularly mediated thin film assembly of the core-shell nanoparticles. The SQUID data reveal a decrease in magnetization and blocking temperature and an increase in coercivity for Fe(3)O(4)@Au, reflecting the decreased coupling of the magnetic moments as a result of the increased interparticle spacing by both gold and capping shells. Implications of the findings to the design of interfacial reactivities via core-shell nanocomposites for magnetic, catalytic, and biological applications are also briefly discussed.     

Synthesis of Fe3O4@phenol formaldehyde resin core-shell nanospheres loaded with Au nanoparticles as magnetic FRET nanoprobes for detection of thiols in living cells

A magnetic, sensitive, and selective fluorescence resonance energy transfer (FRET) probe for detection of thiols in living cells was designed and prepared. The FRET probe consists of an Fe(3)O(4) core, a green-luminescent phenol formaldehyde resin (PFR) shell, and Au nanoparticles (NPs) as FRET quenching agent on the surface of the PFR shell. The Fe(3)O(4) NPs were used as the core and coated with green-luminescent PFR nanoshells by a simple hydrothermal approach. Au NPs were then loaded onto the surface of the PFR shell by electric charge absorption between Fe(3)O(4)@PFR and Au NPs after modifying the Fe(3)O(4)@PFR nanocomposites with polymers to alter the charge of the PFR shell. Thus, a FRET probe can be designed on the basis of the quenching effect of Au NPs on the fluorescence of Fe(3)O(4)@PFR nanocomposites. This magnetic and sensitive FRET probe was used to detect three kinds of primary biological thiols (glutathione, homocysteine, and cysteine) in cells. Such a multifunctional fluorescent probe shows advantages of strong magnetism for sample separation, sensitive response for sample detection, and low toxicity without injury to cellular components.     

Three-layer composite magnetic nanoparticle probes for DNA

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.     

聚乙烯吡咯烷酮包裹核壳型Fe_3O_4/Au纳米粒子的制备

采用改进的Polyol合成法,以聚乙烯吡咯烷酮（PVP）为表面活性剂制备PVP包裹的单分散的Fe3O4/Au纳米粒子.透射电镜（TEM）和X射线衍射（XRD）分析证实了Fe3O4/Au的核壳型纳米结构,并确定了纳米粒子的尺寸大小和分布.UV-Vis测定显示了所制备的纳米粒子具有光学活性,而振动样品磁强计（VSM）测量显示纳米粒子具有优异的磁化率.     

Fabrication of nanorattles with passive shell

This investigation describes the formation of a metal nanorattle with a pure metal shell by varying experimental parameters. The galvanic replacement reaction between silver and chloroauric acid was adopted to prepare hollow metal nanoparticles. This approach is extended to produce nanorattles of Au cores and Au shells by starting with Au(core)Ag(shell) nanoparticles as templates. The effect of temperature on the nanostructure of the final product is also considered. The composition of the shell in nanorattles can be controlled by varying the reaction temperature (to form pure gold or gold-silver alloy, for example). X-ray absorption fine structure spectroscopy is conducted to elucidate the fine structure of these nanoparticles. Partial alloying between the Au core and the Ag shell is observed by extended X-ray absorption fine structure (EXAFS).     

Microwave assisted green synthesis of Fe@Au core–shell NPs magnetic to enhance olive oil efficiency on eradication of helicobacter pylori (life preserver)

Eco friendly and green synthetic approach for the synthesis of metallic nanoparticles gained much importance in the recent era. In the present study, an environmental friendly and plant mediated synthetic approach was used for the synthesis of gold coated iron (Fe@Au) nanoparticles using extract solution of olive oil, licorice root (Glycyrrhiza glabra) and coconut oil (OLC). These extracts were acted as a reducing agent during the formation of core–shell nanoparticles that provides long-time stability, lower toxicity and higher permeability to specific target cells. In order to achieve the small sized, regular spherical shaped, and homogeneous nanoparticles optimum conditions were ensured. In fact, the use of microwave irradiation was offered higher reaction rate and better product. The Fe@AuNPs have been characterized by UV–Visible spectroscopy, Energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), High resolution Transmission electron microscope (HR-TEM), Fourier Transform Infrared Spectroscopy (FT-IR), high-performance liquid chromatography (HPLC), High angle annular dark-field scanning transmission electron microscopy (HAADF-STEM), Particle-Size Distribution (PSD), and Magnetic hysteresis loops. The synthesized gold coated iron nanoparticles showed significant antioxidant potential with maximum inhibition rates, the biosynthesized nanoparticles were also found effective against Helicobacter pylori (H. pylori) and ulcer.     

A General and High‐Yield Galvanic Displacement Approach to Au?M (M=Au,Pd, and Pt) Core–Shell Nanostructures with Porous Shells and Enhanced Electrocatalytic Performances

In this work, we utilize the galvanic displacement synthesis and make it a general and efficient method for the preparation of Au? M (M=Au, Pd, and Pt) core–shell nanostructures with porous shells, which consist of multilayer nanoparticles. The method is generally applicable to the preparation of Au? Au, Au? Pd, and Au? Pt core–shell nanostructures with typical porous shells. Moreover, the Au? Au isomeric core–shell nanostructure is reported for the first time. The lower oxidation states of Au^I, Pd^II, and Pt^II are supposed to contribute to the formation of porous core–shell nanostructures instead of yolk‐shell nanostructures. The electrocatalytic ethanol oxidation and oxygen reduction reaction (ORR) performance of porous Au? Pd core–shell nanostructures are assessed as a typical example for the investigation of the advantages of the obtained core–shell nanostructures. As expected, the Au? Pd core–shell nanostructure indeed exhibits a significantly reduced overpotential (the peak potential is shifted in the positive direction by 44 mV and 32 mV), a much improved CO tolerance (I_f/I_b is 3.6 and 1.63 times higher), and an enhanced catalytic stability in comparison with Pd nanoparticles and Pt/C catalysts. Thus, porous Au? M (M=Au, Pd, and Pt) core–shell nanostructures may provide many opportunities in the fields of organic catalysis, direct alcohol fuel cells, surface‐enhanced Raman scattering, and so forth.     

Synthesis and characterization of multifunctional Fe3O4/poly(fluorescein O-methacrylate) core/shell nanoparticles

Multifunctional fluorescent and superparamagnetic Fe(3)O(4)/poly(fluorescein O-methacrylate) [Fe(3)O(4)/poly(FMA)] nanoparticles with core/shell structure were synthesized via surface-initiated polymerization. First, polymerizable double bonds were introduced onto the surface of Fe(3)O(4) nanoparticles via ligand exchange and a condensation reaction. A fluorescent monomer, FMA, was then polymerized to the double bonds at the surface via free-radical polymerization, leading to form a fluorescent polymer shell around the superparamagnetic Fe(3)O(4) core. The resultant Fe(3)O(4)/poly(FMA) nanoparticles were characterized by Fourier transform infrared, nuclear magnetic resonance, and X-ray diffraction spectroscopy to confirm the reactions. Transmission electron microscopy images showed that the Fe(3)O(4)/poly(FMA) nanoparticles have a spherical and monodisperse core/shell morphology. Photoluminescence spectroscopy and superconducting quantum interference device magnetometer analyses confirmed that the Fe(3)O(4)/poly(FMA) nanoparticles exhibited fluorescent and superparamagnetic properties, respectively. In addition, we demonstrated the potential bioimaging application of the Fe(3)O(4)/poly(FMA) nanoparticles by visualizing the cellular uptake of the nanoparticles into A549 lung cancer cells.     

Preparation and Characterization of Pt/Co‐Core Au‐Shell Magnetic Nanoparticles

Pt/Co‐core Au‐shell nanoparticles were synthesized via a two‐step route using NaBH₄ as a reducing agent. The nanoparticles are characterized by UV‐vis spectroscopy, transmission electron microscopy (TEM) and powder X‐ray diffraction (XRD). The results indicate that the as‐synthesized Pt/Co‐core Au‐shell nanoparticles have a disordered face centered cubic (fcc) structure, whereas the annealed Pt/Co‐core Au‐shell nanoparticles exhibit an ordered face centered tetragonal (fct) structure. Superconducting quantum interference device (SQUID) studies reveal that the coercivity of the annealed Pt/Co‐core Au‐shell nanoparticles increases to 510 Oe after heat treatment at 500 °C for 2 h.     

核壳型Fe_3O_4/Au粒子的制备及其在表面等离子体子共振传感器中的应用

合成了核壳型Fe3O4/Au复合粒子,并对其形貌、光学性质进行了表征.通过外加磁场将Fe3O4/Au复合粒子与兔抗人IgG的偶联体固定于表面等离子体子共振(SPR)传感器的金基底膜上,形成了Fe3O4/Au/抗IgG敏感膜.与传统的通过巯基丙酸连接蛋白的方式相比,磁场作用固定的Fe3O4/Au/抗IgG敏感膜制备简单,易洗脱,具有良好的再生性,且在一定程度上提高了传感器的灵敏度.并对人IgG进行了测定,结果表明,传感器对于浓度范围在1.25～20.00μg·mL-1的人IgG有良好的信号响应.     

憎水性三金属纳米粒子的合成、表征及磁性

以磺基琥珀酸二辛酯钠盐(AOT)为表面活性剂,采用反胶束法合成了憎水性CoFe/Au纳米粒子, 利用配体交换、水洗等去除AOT并使纳米粒子分级.采用紫外-可见光谱(UV-Vis)、透射电镜(TEM)、X射线衍射(XRD)、X射线电子能量散射(EDX)及等离子发射光谱 (ICP)等对产物进行了表征,通过超导量子干涉仪(SQIUD)研究了纳米粒子的磁性质.结果表明,反胶束法合成的CoFe/Au三金属纳米粒子具有较好的单分散性和稳定性,平均粒径约为4 nm.当外磁场强度为1.5×10⁴ A/m时,阻塞温度T_b为65 K,温度高于T_b时纳米粒子显示出超顺磁性,低于T_b时呈铁磁性,在5 K时其矫顽力(Hc)达4.67×10⁴ A/m.     

Gold nanoparticles with perfluorothiolate ligands

Two syntheses of gold nanoparticles with fluorinated alkyl and aryl thiolate ligands are reported. The fluorous Au nanoparticles are smaller than previous gold fluor-capped examples, and are in the 44-75 Au atom size range. Fluoroalkyl thiolate-protected (1H,1H,2H,2H-perfluorodecanethiolate) nanoparticles synthesized by a Brust reaction are a mixture of (mainly) approximately 8.5 kDa (ca. 44 core atoms) and approximately 14 kDa (ca. 75 core atoms) species, by MALDI-mass spectrometry. This composition is consistent with thermogravimetric analysis (TGA) results of the ligand shell composition. 19F NMR spectra display a progressive line broadening of resonances for fluorine sites closer to the Au core. A second synthetic route used a (ligand replacement) reaction of pentafluorobenzenethiol with Au55(PPh3)12Cl6. The exchange is (as previously observed for nonfluorinated thiols) accompanied by nanoparticle core size changes to produce a polydisperse mixture within which a Au75 core species could be electrochemically discerned by its characteristic 0.74 V electrochemical energy gap. Further characterization of the polydisperse nanoparticle product was done by HPLC, TEM, TGA, optical spectroscopy, and NMR data. Both varieties of fluorous nanoparticles exhibit solubilities typical of perfluorinated materials, as opposed to proteo versions.     

Synthesis and Optical Properties of Fe@Au,Ni@Au Bimetallic Core–Shell Nanoparticles

Fe@Au and Ni@Au core–shell nanoparticles (NPs) were synthesized by liquid-phase reduction of iron and nickel compounds by sodium borohydride in an aqueous medium. Transmission electron microscopy, X-ray powder diffraction, and spectrophotometry were used to confirm the structure of the NPs and to determine their shape and the average core and shell size.