Layer-by-layer assembled Fe3O4@C@CdTe core/shell microspheres as separable luminescent probe for sensitive sensing of Cu2+ ions

A novel multifunctional microsphere with a fluorescent CdTe quantum dots (QDs) shell and a magnetic core (Fe(3)O(4)) has been successfully developed and prepared by a combination of the hydrothermal method and layer-by-layer (LBL) self-assembly technique. The resulting fluorescent Fe(3)O(4)@C@CdTe core/shell microspheres are utilized as a chemosensor for ultrasensitive Cu(2+) ion detection. The fluorescence of the obtained chemosensor could be quenched effectively by Cu(2+) ions. The quenching mechanism was studied and the results showed the existence of both static and dynamic quenching processes. However, static quenching is the more prominent of the two. The modified Stern-Volmer equation showed a good linear response (R(2) = 0.9957) in the range 1-10 μM with a quenching constant (K(sv)) of 4.9 × 10(4) M(-1). Most importantly, magnetic measurements showed that the Fe(3)O(4)@C@CdTe core/shell microspheres were superparamagnetic and they could be separated and collected easily using a commercial magnet in 10 s. These results obtained not only provide a way to solve the embarrassments in practical sensing applications of QDs, but also enable the fabrication of other multifunctional nanostructure-based hybrid nanomaterials.     

Lanthanum silicate coated magnetic microspheres as a promising affinity material for phosphopeptide enrichment and identification

Novel Fe(3)O(4)@La(x)Si(y)O(5) affinity microspheres consisting of a superparamagnetic Fe(3)O(4) core and an amorphous lanthanum silicate shell have been synthesized. The core-shell-structured Fe(3)O(4)@La(x)Si(y)O(5) microspheres, with a mean size of ca. 480 nm, had rough lanthanum silicate surfaces and displayed relatively strong magnetism (47.2 emu g(-1)). This novel affinity material can be used for selective capture, rapid magnetic separation, and part dephosphorylation (which plays an important role in identifying phosphopeptides in MS) of the phosphopeptides in a peptide mixture. Its ability to selectively trap and magnetically isolate as well as label the phosphopeptides was evaluated using a standard phosphorylated protein (β-casein) and a real sample (human serum). Phosphopeptides and their corresponding label ions were detected for concentrations of β-casein as low as 1 × 10(-9) M and in mixtures of β-casein and BSA with molar ratios as low as 1:50. In addition, this affinity material, with its labeling properties, is superior to commercial TiO(2) beads in terms of interference from non-phosphopeptide molecules. These results reveal that the lanthanum silicate coated magnetic microspheres represent a promising affinity material for the rapid purification and recognition of phosphopeptides.     

Preparation of Fe3O4@SiO2@layered double hydroxide core-shell microspheres for magnetic separation of proteins

Three-component microspheres containing an SiO(2)-coated Fe(3)O(4) magnetite core and a layered double hydroxide (LDH) nanoplatelet shell have been synthesized via an in situ growth method. The resulting Fe(3)O(4)@SiO(2)@NiAl-LDH microspheres display three-dimensional core-shell architecture with flowerlike morphology, large surface area (83 m(2)/g), and uniform mesochannels (4.3 nm). The Ni(2+) cations in the NiAl-LDH shell provide docking sites for histidine and the materials exhibit excellent performance in the separation of a histidine (His)-tagged green fluorescent protein, with a binding capacity as high as 239 μg/mg. The microspheres show highly selective adsorption of the His-tagged protein from Escherichia coli lysate, demonstrating their practical applicability. Moreover, the microspheres possess superparamagnetism and high saturation magnetization (36.8 emu/g), which allows them to be easily separated from solution by means of an external magnetic field and subsequently reused. The high stability and selectivity of the Fe(3)O(4)@SiO(2)@NiAl-LDH microspheres for the His-tagged protein were retained over several separation cycles. Therefore, this work provides a promising approach for the design and synthesis of multifunctional LDH microspheres, which can be used for the practical purification of recombinant proteins, as well as having other potential applications in a variety of biomedical fields including drug delivery and biosensors.     

Ultrafast hydrothermal synthesis of high quality magnetic core phenol-formaldehyde shell composite microspheres using the microwave method

An ultrafast, facile, and efficient microwave hydrothermal approach was designed to fabricate magnetic Fe(3)O(4)/phenol-formaldehyde (PF) core-shell microspheres for the first time. The structure of the Fe(3)O(4)/PF core-shell microspheres could be well controlled by the in situ polycondensation of phenol and formaldehyde with magnetic Fe(3)O(4) clusters as the seeds in an aqueous solution without any surfactants. The effect of synthetic parameters, such as the feeding amounts of phenol, the dosages of formaldehyde, the reaction temperatures, and the microwave heating time, on the morphologies and sizes of the Fe(3)O(4)/PF microspheres were investigated in details. The phenol-formaldehyde shell is found to be evenly coated on Fe(3)O(4) clusters within 10 min of the irradiation. The as-prepared microspheres were highly uniform in morphology, and the method was found to allow the shell thickness to be finely controlled in the range of 10-200 nm. The properties of the composite microspheres were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), thermogravimetic analysis (TGA), Fourier transform infrared (FT-IR) spectra, X-ray diffraction (XRD), and vibrating sample magnetometer (VSM). The as-prepared Fe(3)O(4)/PF microspheres were monodisperse and highly dispersible in water, ethanol, N,N-dimethyformamide, and acetone, a beneficial quality for the further functionalization and applications of the Fe(3)O(4)/PF microspheres.     

Fe3O4@Al2O3 magnetic core-shell microspheres for rapid and highly specific capture of phosphopeptides with mass spectrometry analysis

Selective detection of phosphopeptides from complex biological samples is a challenging and highly relevant task in many proteomics applications. In this study, a novel phosphopeptide enrichment approach based on the strong interaction of Fe(3)O(4)@Al(2)O(3) magnetic core-shell microspheres with phosphopeptides has been developed. With a well-defined core-shell structure, the Fe(3)O(4)@Al(2)O(3) magnetic core-shell microspheres not only have a shell of aluminum oxide, giving them a high-trapping capacity for the phosphopeptides, but also have magnetic property that enables easy isolation by positioning an external magnetic field. The prepared Fe(3)O(4)@Al(2)O(3) magnetic core-shell microspheres have been successfully applied to the enrichment of phosphopeptides from the tryptic digest of standard phosphoproteins beta-casein and ovalbumin. The excellent selectivity of this approach was demonstrated by analyzing phosphopeptides in the digest mixture of beta-casein and bovine serum albumin with molar ratio of 1:50 as well as tryptic digest product of casein and five protein mixtures. The results also proved a stronger selective ability of Fe(3)O(4)@Al(2)O(3) magnetic core-shell microspheres over Fe(3+)-immobilized magnetic silica microspheres, commercial Fe(3+)-IMAC (immobilized metal affinity chromatography) resin, and TiO(2) beads. Finally, the Al(2)O(3) coated Fe(3)O(4) microspheres were successfully utilized for enrichment of phosphopeptides from digestion products of rat liver extract. These results show that Fe(3)O(4)@Al(2)O(3) magnetic core-shell microspheres are very good materials for rapid and selective separation and enrichment of phosphopeptides.     

Preparation of Fe3O4@C@PANI magnetic microspheres for the extraction and analysis of phenolic compounds in water samples by gas chromatography-mass spectrometry

In this work, core-shell structure Fe(3)O(4)@C@polyaniline magnetic microspheres were synthesized using simple hydrothermal reactions. The carbon-coated magnetic microspheres (Fe(3)O(4)@C) were first synthesized by a hydrothermal reaction, and then aniline was polymerized on the magnetic core via another hydrothermal reaction. Then, the obtained Fe(3)O(4)@C@polyaniline magnetic microspheres were applied as magnetic adsorbents for the extraction of aromatic molecules due to π-π interactions between polyaniline shell and aromatic compounds. In our study, five kinds of phenols including phenol, 2,4-dichlorophenol (DCP), 2,4,5-trichlorophenol (TCP), pentachlorophenol (PCP) and bisphenol A (BPA) were selected as the model analytes to verify the extraction ability of Fe(3)O(4)@C@PANI microspheres. After derivatization, the phenols were detected using gas chromatography-mass spectrometry (GC-MS). The dominant parameters affecting enrichment efficiency were investigated and optimized. Under the optimal conditions, the proposed method was evaluated, and applied to the analysis of phenols in real water samples. The results demonstrated that our proposed method based on Fe(3)O(4)@C@polyaniline magnetic microspheres had good linearity (r(2)>0.991), and limits of quantification (2.52-29.7 ng/mL), high repeatability (RSD<13.1%) and good recovery (85.3-110.6%).     

Fe_3O_4/CdTe/聚氨酯纳米复合物的制备及其性能研究

由共沉淀法和Stober法制备了伯胺基功能化SiO2稳定的Fe3O4磁性纳米粒子Fe3O4@SiO2-NH2;Fe3O4@SiO2-NH2与二异氰酸酯及咪唑阳离子二醇、聚乙二醇的反应使其表面形成阳离子型聚氨酯稳定层;通过阳离子型聚氨酯与CdTe量子点表面修饰的巯基乙酸间的电荷相互作用,制备得到了Fe3O4/CdTe/聚氨酯纳米复合物.用X射线衍射(XRD)、红外吸收光谱(FTIR)、热重分析(TGA)、透射电子显微镜(TEM)、磁强计(VSM)、紫外吸收光谱(UV)、荧光发射光谱(PL)表征了该纳米复合物的结构与性能.结果表明,CdTe量子点均匀地分散在Fe3O4@SiO2磁性纳米粒子周围,所得纳米复合物在溶剂中分散均匀,不团聚,且具有超顺磁性,并保持了CdTe量子点的荧光性能.     

Synthesis and characterization of magnetic and luminescent Fe_3O_4/CdTe nanocomposites using aspartic acid as linker

In this study,the preparation of a new kind of magnetic and luminescent Fe₃O₄/CdTe nanocomposites was demonstrated. Superparamagnetic Fe₃O₄ nanoparticles were first synthesized by hydrothermal coprecipitation of ferric and ferrous ions,followed by the modification of their surfaces with tetramethylammonium hydroxide（TMAOH） and the chemical activation with aspartic acid.The surface-modified Fe₃O₄ nanoparticles were then covalently coated with CdTe quantum dots（QDs）,which were modified with mercaptoacetic acid（MPA）,to form the Fe₃O₄/CdTe magnetic and luminescent nanocomposites through the coordination of the amino groups on the surfaces of Fe₃O₄ and the carboxyl groups on CdTe QDs.The structure and properties of as-synthesized nanocomposites were characterized.It was indicated that the nanocomposites possessed structure with an average diameter of 40- 50 nm,yellow-green emission feature and room temperature ferro-magnetism.Both the fluorescence and UV-vis absorption spectra of the nanocomposites showed a blue shift comparing with those of CdTe QDs.The mechanism of the blue shift was presented.The nanocomposites retained the ferromagnetic property with a saturation magnetization of 8.9 emu/g.     

Preparation and mechanism of Fe_3O_4/Au core/shell super-paramagnetic microspheres

In the presence of Fe3O4 nano-particles, a new type of super-paramagnetic Fe3O4/Au microspheres with core/shell structures was prepared by reduction of Au3+ with hydroxylamine. The formation mechanism of the core/shell microspheres was studied in some detail. It was shown that the formation of the complex microspheres can be divided into two periods, that is, surface reaction-controlled process and diffusion-controlled process. The relative time lasted by either process depends upon the amount of Fe3O4 added and the initial concentration of Au3+. XPS analysis revealed that along with increasing in coating amount, the strength of the characteristic peaks of Au increased, and the Auger peaks of Fe weakened and even disappeared. Size distribution analysis showed that the core/shell microspheres are of an average diameter of 180 nm, a little bit larger than those before coating.     

热敏性高分子包裹的磁性微球的合成

磁性高分子微球由于其在外加磁场作用下简单、快速易行的磁分离特性，其在细胞分离、固定化酶、靶向药物等领域的应用研究日益活跃，并显示出较好的应用前景［１］．有关文献报道了制备磁性微球的不同方法［２］．Ｎ 异丙基丙烯酰胺（Ｎ ｉｓｏｐｒｏｐｙｌａｃｒｙｌａ...     

Facile method for synthesis of hollow porous magnetic microspheres with controllable structure

Hollow porous magnetic microspheres with strong magnetization and controllable structure were prepared via a facile electrostatic self-assembly of the positively charged Fe(3)O(4) nanoparticles onto the surface of the negatively charged poly(N,N'-methylenebisacrylamide-co-methacrylic acid) (P(MBAAm-co-MAA)) microspheres with subsequent removal of the polymer core through calcination at high temperature. The shell thickness was facilely tuned through the ratio between Fe(3)O(4) and polymer, and the void space was conveniently changed through the size of polymer microspheres. The hollow magnetic microspheres possessed high saturation magnetization value (51.38 emu/g) and porous structure with high specific surface area (108.04 m(2)/g). Based on these properties, the drug loading and release behaviors were investigated, which indicated that the hollow magnetic microspheres exhibited a controlled release process.     

Superparamagnetic high-magnetization microspheres with an Fe3O4@SiO2 core and perpendicularly aligned mesoporous SiO2 shell for removal of microcystins

Superparamagnetic microspheres with an Fe3O4@SiO2 core and a perpendicularly aligned mesoporous SiO2 shell were synthesized through a surfactant-templating sol-gel approach. The microspheres possess high magnetization (53.3 emu/g), high surface area (365 m2/g), large pore volume (0.29 cm3/g), and uniform mesopore (2.3 nm). By using the unique core-shell microspheres with accessible large pores and excellent magnetic property, a fast removal of microcystins with high efficiency (>95%) can be achieved.     

亲/疏水不对称空心聚合物微球制备及磁性粒子装载研究

首先将(马来酸酐-醋酸乙烯酯共聚物)核/(马来酸酐-二乙烯基苯共聚物)壳微球的壳层外表面酐基烷基溴化,然后将核溶蚀、壳层内表面酐基水解,制得内表面含亲水羧基、外表面含烷基溴、具有微孔(Barrett-Joyner-Halenda平均孔径14.9nm)的空心聚合物微球.以此空心微球为微反应器,使Fe2+和Fe3+通过球壁...     

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.     

Synthesis of novel Fe3O4@SiO2@CeO2 microspheres with mesoporous shell for phosphopeptide capturing and labeling

Fe(3)O(4)@SiO(2)@CeO(2) microspheres with magnetic core and mesoporous shell were synthesized, and the multifunctional materials were utilized to capture phosphopeptides and catalyze the dephosphorylation simultaneously, thereby labeling the phosphopeptides for rapid identification.     

P(St-GMA)/Fe3O4磁性聚合物微球的制备及表征

采用沉淀法制备了Fe3O4纳米粒子, 以苯乙烯(St)、甲基丙烯酸缩水甘油酯(GMA)为聚合单体, 使用分散聚合法制备了P(St-GMA)/Fe3O4磁性聚合物微球. 分析了Fe3O4粒子的形貌和结构. 研究了制备条件对磁性聚合物微球磁含量的影响. 采用FTIR, XRD, TG及TEM等手段对磁性聚合物微球的微观结构及形貌、磁含量等进行了分析表征. 研究结果表明, 制备的磁性聚合物微球粒径均一, 磁含量高达74%.     

Fluorescence resonance energy transfer inhibition assay for α-fetoprotein excreted during cancer cell growth using functionalized persistent luminescence nanoparticles

Persistent-luminescence nanoparticles (PLNPs) are promising as a new generation of photoluminescent probes for detection of biomolecules and bioimaging. Here we report a fluorescence resonance energy transfer (FRET) inhibition assay for α-fetoprotein (AFP) excreted during cancer cell growth using water-soluble functionalized PLNPs based on Eu2+- and Dy3+-doped Ca1.86Mg0.14ZnSi2O7. Polyethyleneimine-coated PLNPs were conjugated with AFP-antibody-coated gold nanoparticles as a sensitive and specific persistent photoluminescence probe for detection of AFP in serum samples and imaging of AFP excreted during cancer cell growth. Such PLNPs do not contain toxic heavy metals. Their long-lasting afterglow nature allows detection and imaging without external illumination, thereby eliminating the autofluorescence and scattering light from biological matrixes encountered under in situ excitation.     

Fabrication of one-dimensional Fe3O4/P(GMA-DVB) nanochains by magnetic-field-induced precipitation polymerization

One-dimensional (1D) magnetic Fe(3)O(4)/P(GMA-DVB) peapod-like nanochains have been successfully synthesized by magnetic-field-induced precipitation polymerization using Fe(3)O(4) as building blocks and P(GMA-DVB) as linker. The Fe(3)O(4) microspheres without surface modification can be arranged with the direction of the external magnetic field in a line via the dipolar interaction between Fe(3)O(4) microspheres and linked permanently via P(GMA-DVB) coating during precipitation polymerization. The length of peapod-like nanochains can be controlled by magnetic field intensity, and the thickness of polymer shell can be tuned by the amount of monomers. Magnetic measurement revealed that these 1D peapod-like nanochains showed highly magnetic sensitivity. In the presence of magnetic field, 1D magnetic Fe(3)O(4)/P(GMA-DVB) peapod-like nanochains can be oriented and aligned along the direction of external magnetic field.     

Ultrasound-triggered smart drug release from multifunctional core-shell capsules one-step fabricated by coaxial electrospray method

Multifunctional core-shell capsules that triggered release by ultrasound stimulus were one-step fabricated by the coaxial electrospray method. The TiO(2) shell suppressed the initial burst release of the paclitaxel. Fe(3)O(4) and graphene quantum dots inside the oil core functioned successfully for magnetic targeting and fluorescence imaging, respectively. Paclitaxel was trigger released when the dual layer of titania shell cracked under the ultrasound stimulation, and the releasing profile could be controlled by the length of applied ultrasound time.     

γ-Fe(2)O(3) and Fe(3)O(4) magnetic hierarchically nanostructured hollow microspheres: Preparation, formation mechanism, magnetic property, and application in water treatment

In this paper, we report the preparation of γ-Fe(2)O(3) and Fe(3)O(4) magnetic hierarchically nanostructured hollow microspheres by a solvothermal combined with precursor thermal conversion method. These γ-Fe(2)O(3) and Fe(3)O(4) magnetic hierarchically nanostructured hollow microspheres were constructed by three-dimensional self-assembly of nanosheets, forming porous nanostructures. The effects of experimental parameters including molar ratio of reactants and reaction temperature on the precursors were studied. The time-dependent experiments indicated that the Ostwald ripening was responsible for the formation of the hierarchically nanostructured hollow microspheres of the precursors. γ-Fe(2)O(3) and Fe(3)O(4) magnetic hierarchically nanostructured hollow microspheres were obtained by the thermal transformation of the precursor hollow microspheres. Both γ-Fe(2)O(3) and Fe(3)O(4) hierarchically nanostructured hollow microspheres exhibited a superparamagnetic property at room temperature and had the saturation magnetization of 44.2 and 55.4emu/g, respectively, in the applied magnetic field of 20 KOe. Several kinds of organic pollutants including salicylic acid (SA), methylene blue (MB), and basic fuchsin (BF) were chosen as the model water pollutants to evaluate the removal abilities of γ-Fe(2)O(3) and Fe(3)O(4) magnetic hierarchically nanostructured hollow microspheres. It was found that γ-Fe(2)O(3) hierarchically nanostructured hollow microspheres showed a better adsorption ability over SA than MB and BF. However, Fe(3)O(4) hierarchically nanostructured hollow microspheres had the best performance for adsorbing MB.