Functionalization of Fe3O4 magnetic nanoparticles with RGD peptide derivatives

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Synthesis of orientedly bioconjugated core/shell Fe3O4@Au magnetic nanoparticles for cell separation

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.     

Preparation and cell response of bio-mineralized Fe3O4 nanoparticles

Silk fibroin (SF)-coated Fe(3)O(4) nanoparticles (NPs) with good superparamagnetism were successfully prepared via a bio-mineralization process at room temperature. Two cell tests revealed that mineralized SF-coated Fe(3)O(4) NPs presented good cytocompatibility for L929 and osteoblast cells and higher cell density after 5 d with high concentrations of SF-coated Fe(3)O(4) NPs (up to 0.5 mg/mL). These resulted from SF surface coating on NPs, nano-surface morphology and iron ion release of Fe(3)O(4) NPs. The mineralized SF-coated Fe(3)O(4) NPs could be envisioned for various bone orthopedic and therapeutic applications, in which SF-coated NPs location is controlled through an external magnetic field to promoted bone growth.     

Preparation of carbon coated Fe3O4 nanoparticles for magnetic separation of uranium

Uranium(VI) was removed from aqueous solutions using carbon coated Fe₃O₄ nanoparticles (Fe₃O₄@C). Batch experiments were conducted to study the effects of initial pH, shaking time and temperature on uranium sorption efficiency. It was found that the maximum adsorption capacity of the Fe₃O₄@C toward uranium(VI) was ∼120.20 mg g⁻¹ when the initial uranium(VI) concentration was 100 mg L⁻¹, displaying a high efficiency for the removal of uranium(VI) ions. Kinetics of the uranium(VI) removal is found to follow pseudo-second-order rate equation. In addition, the uranium(VI)-loaded Fe₃O₄@C nanoparticles can be recovered easily from aqueous solution by magnetic separation and regenerated by acid treatment. Present study suggested that magnetic Fe₃O₄@C composite particles can be used as an effective and recyclable adsorbent for the removal of uranium(VI) from aqueous solutions.     

Vast magnetic monolayer film with surfactant-stabilized Fe3O4 nanoparticles using Langmuir-Blodgett technique

Although several methods (e.g., self-assembly, spin coating, etc.) have been explored for making a monolayer film of nanoparticles, the monolayer on a substrate is typically smaller than 1 micromx1 microm in certain regions. The approach is not ideally suitable for generating a highly ordered and close-packed homogeneous vast monolayer of nanoparticles, which is potentially important for applications. In this report, the preparation of the vast monolayer films of Fe3O4 nanoparticles with a wide range such as that over 3.25 micromx3.95 microm is reported. Their TEM images showed a two-dimensional assembly of Fe3O4 nanoparticles, demonstrating the uniformity of these nanoparticles. The formation of a Langmuir monolayer of the oleic acid-coated Fe3O4 nanoparticles mixed with stearic acid molecules at the air/water interface and its stability were studied with a pressure-area isotherm curve. TEM and BAM studies demonstrated that increasing surface pressure resulted in a transition from well-separated domains of nanoparticles complex to well-compressed, monoparticulate layers.     

Fe3O4/ZnMg(Al)O magnetic nanoparticles for efficient biodiesel production

Fe₃O₄/ZnMg(Al)O solid base catalyst was prepared by calcining ZnMgAl‐LDHs grown on the surface of magnetic Fe₃O₄ synthesized by chemical coprecipitation. The magnetic property of the catalyst was studied by vibrating sample magnetometer. The results showed that the catalyst possessed excellent magnetic responsivity, and it could be recovered by external magnetic field. The magnetic catalyst was also characterized by ICP, TG‐DTG, XRD, SEM, EDS, TEM and N₂ absorption‐desorption. It was found that the catalyst showed a unique porous structure. The reaction conditions affecting biodiesel yield were investigated, the biodiesel yield reached 94% was obtained under the optimal conditions. The biodiesel yield was still above 82% after 7 times of regeneration, and the catalyst can be easily separated and recycled.     

Highly ordered self-assembly with large area of Fe3O4 nanoparticles and the magnetic properties

Monodisperse Fe3O4 nanoparticles (NPs) with narrow size distribution are synthesized by a high-temperature solution-phase method. The diameter of the as-synthesized NPs is tuned from 2 to 14 nm by varying the reaction conditions. Highly ordered superlattice structures of the Fe3O4 NPs with areas extending over 0.8 microm x 0.7 microm have been successfully obtained. The magnetic properties are investigated in their different states, such as in the solid state and diluted in wax with different concentrations. Some magnetic properties enhanced by increasing interparticle distances, such as the remanent magnetization and coercive field at low temperature, were noticed. Furthermore, we also observed that the saturation magnetization changed with temperature as expected. The preliminary explanation for the properties mentioned above is proposed.     

Fe3O4纳米颗粒的表面改性

通过实验对Fe3O4纳米颗粒表面改性的最佳条件进行了摸索.并根据表面改性的包覆机理对不同酸度,温度和表面活性剂的用量对Fe3O4纳米颗粒的尺寸,磁性和稳定性的影响进行了理论上的分析.     

Fabrication of nanoporous nanocomposites entrapping Fe3O4 magnetic nanoparticles and oxidases for colorimetric biosensing

A nanostructured multicatalyst system consisting of Fe(3)O(4) magnetic nanoparticles (MNPs) as peroxidase mimetics and an oxidative enzyme entrapped in large-pore-sized mesoporous silica has been developed for convenient colorimetric detection of biologically important target molecules. The construction of the nanocomposites begins with the incorporation of MNPs on the walls of mesocellular silica pores by impregnating Fe(NO(3))(3)·9H(2)O, followed by the immobilization of oxidative enzymes. Glutaraldehyde crosslinking was employed to prevent enzymes leaching from the pores and led to over 20 wt% loading of the enzyme. The oxidase in the nanocomposite generates H(2)O(2) through its catalytic action for target molecules and subsequently activates MNPs to convert selected substrates into colored products. Using this strategy, two different biosensing systems were constructed employing glucose oxidase and cholesterol oxidase and their analytical capabilities were successfully verified by colorimetrically detecting the corresponding target molecules with excellent selectivity, sensitivity, reusability, and stability. Future potential applications of this technology range from biosensors to multicatalyst reactors.     

Study on the adsorption of DNA on Fe3O4 nanoparticles and on ionic liquid-modified Fe3O4 nanoparticles

We have investigated the adsorption of herring sperm DNA on Fe₃O₄ magnetic nanoparticles (NPs) before and after modification with the ionic liquid 1-hexyl-3-methylimidazolium bromide. Experiments were performed in a batch mode, and the effects of DNA concentration, pH of the sample solution, ionic strength, temperature, and contact time between reagents were optimized. An evaluation of the adsorption isotherm revealed that the Langmuir model better fits the equilibrium data than the Freundlich model. The maximum adsorption capacities of the unmodified and modified NPs, respectively, were found to be 11.8 and 19.8 mg DNA per gram of adsorbent. The adsorption of DNA onto the modified NPs was endothermic, while it was exothermic in the case of the unmodified NPs. The DNA can be desorbed from the modified surfaces of the NPs by using EDTA as the eluent. The NPs were able to adsorb about 90?±?1.5 % of DNA after being recycled for three times. The method is simple, fast, robust, and does not require organic solvents or sophisticated equipment.

α-Glucosidase immobilization on functionalized Fe3O4 magnetic nanoparticles for screening of enzyme inhibitors

α-Glucosidase was stereoscopically immobilized on the surface of Fe₃O₄ magnetic nanoparticles, which was modified with APTES, using GA as a cross-linker. This established method had a broad application prospect for screening of enzyme inhibitors.     

Synthesis of Fe3O4, Fe2O3, Ag/Fe3O4 and Ag/Fe2O3 nanoparticles and their electrocatalytic properties

Two important iron oxides:Fe3O4 and Fe2O3,as well as Fe3O4 and Fe2O3 nanoparticles mingling with Ag were successfully synthesized via a hydrothermal procedure.The samples were confirmed and characterized by X-ray diffraction(XRD),and X-ray photoelectron spectroscopy(XPS).The morphology of the samples was observed by transmission electron microscopy(TEM).The results indicated Fe3O4,Fe2O3,Ag/Fe3O4 and Ag/Fe2O3 samples all were nanoparticles with smaller sizes.The samples were modified on a glassy carbon electrode and their elctrocatalytic properties for p-nitrophenol in a basic solution were investigated.The results revealed all the samples showed enhanced catalytic performances by comparison with a bare glassy carbon electrode.Furthermore,p-nitrophenol could be reduced at a lower peak potential or a higher peak current on a glassy carbon electrode modified with Ag/Fe3O4 or Ag/Fe2O3 composite nanoparticles.     

Immobilization of fluorescent protein TagGFP2 on Fe3O4-based magnetic nanoparticles

Russian Chemical Bulletin - The immobilization of fluorescent protein TagGFP2 on Fe3O4-based magnetic nano particles (MNPs), preliminarily functionalized with 3-aminopropylsilane and...     

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.     

A sensitive choline biosensor using Fe3O4 magnetic nanoparticles as peroxidase mimics

A sensitive choline biosensor using Fe(3)O(4) magnetic nanoparticles and a choline oxidase modified gold electrode was developed. Fe(3)O(4) magnetic nanoparticles as peroxidase mimics used in the choline biosensor can not only improve the sensitivity of the response signal, but also possess the favorable properties of stability, magnetic separation and easy preparation, etc. When using the reduction currents of square wave voltammetry as the detection signals, the interferences of ascorbic acid and uric acid to the choline biosensor can be reduced effectively. The reduction currents of the square wave voltammetry were increased with the logarithm values of the choline chloride concentration (from 10(-9) to 10(-2) M), the detection limit was estimated to be 0.1 nM (S/N = 3). This choline biosensor also exhibited favorable selectivity and stability in the determination of choline chloride.     

Improved magnetic properties of self-composite SrFe12O19 powder prepared by Fe3O4 nanoparticles

Sintered polycrystalline strontium hexaferrite, which is one of the most widely used permanent magnetic materials, has been applied in many areas such as electrical and mechanical transductor devices. Improving the coercivity (H_cJ) of M-type strontium hexaferrite with a nominal composition SrFe₁₂O₁₉ (SrM) plays an essential role to adapt to many modern applications, but is limited by the process and purity of raw materials. In this work, we prepared SrM powders with different iron resources, sintering temperatures, and Fe/Sr atom ratios. It was found that using Fe₃O₄ nanoparticles with a Fe/Sr atom ratio of 12 at 1100 °C performed the self-composites with 70% nano-size and 30% micro-size, which had the best performance. The coercivity reaches 348.9 kA/m, which is improved compared to pure SrM obtained by other iron resources in the solid-state method. This process shows a unique formation mechanism and the resulting self-composite microstructure eventually causes enhancement in the properties, which provides a new way for high-performance hexaferrites.     

Colorimetric determination of radical scavenging activity of antioxidants using Fe3O4 magnetic nanoparticles

We report the first use of iron oxide magnetic nanoparticles (Fe₃O₄ MNPs) as a novel, alternative, simple and reliable agents for colorimetric measurement of radical scavenging activity of the antioxidants. In the presence of H₂O₂ and the peroxidase colorimetric substrate, Fe₃O₄ MNPs catalyzed the oxidation of colorless peroxidase substrate to form colorimetric products via the generation of hydroxyl radicals. After adding antioxidants, the catalytic activity of Fe₃O₄ MNPs was inhibited due to scavenging of hydroxyl radicals by the antioxidants, producing less colorimetric products resulting in the reduction of color intensity. Two model antioxidant standards including gallic acid (GA) and epigallocatechin gallate (EGCG) were successfully evaluated for their hydroxyl radical scavenging activity using the developed assay. The performance of the developed method was validated against traditional antioxidant assays for 9 tea samples. Using the Spearman rank correlation coefficient method, the antioxidant activity of tea samples obtained from the Fe₃O₄ MNP assay correlated well with the traditional assays at the 95% confidence level. Furthermore, the developed assay was successfully carried out on a paper-based device to provide for high throughput analysis with low amounts of reagents and sample consumption and low analysis cost for screening of radical scavenging activity of the antioxidants. The results from the analysis of antioxidant activity in tea samples obtained from the Fe₃O₄ MNP paper-based assay were not significantly different to those obtained from the developed Fe₃O₄ MNP spectrophotometric assay indicating that the developed assay was also applicable in a low-cost analysis platform.     

Silica supported Fe3O4 magnetic nanoparticles for magnetic solid-phase extraction and magnetic in-tube solid-phase microextraction: application to organophosphorous compounds

This work demonstrates the application of silica supported Fe₃O₄ nanoparticles as sorbent phase for magnetic solid-phase extraction (MSPE) and magnetic on-line in-tube solid-phase microextraction (Magnetic-IT-SPME) combined with capillary liquid chromatography–diode array detection (CapLC-DAD) to determine organophosphorous compounds (OPs) at trace level. In MSPE, magnetism is used as separation tool while in Magnetic-IT-SPME, the application of an external magnetic field gave rise to a significant improvement of the adsorption of OPs on the sorbent phase. Extraction efficiency, analysis time, reproducibility and sensitivity have been compared. This work showed that Magnetic-IT-SPME can be extended to OPs with successful results in terms of simplicity, speed, extraction efficiency and limit of detection. Finally, wastewater samples were analysed to determine OPs at nanograms per litre.     

正癸酸修饰磁性纳米Fe3O4对溶菌酶的吸附研究

以沉淀法制备了正癸酸修饰磁性纳米Fe3O4,采用XRD、TEM和FT-IR对修饰前后的磁性纳米粒子的形态、结构进行了表征。将修饰后的磁性纳米粒子用于对溶菌酶蛋白进行吸附分离,研究了溶液的pH、温度、时间、溶菌酶初始浓度、离子强度等因素对吸附过程的影响。结果表明:pH=10.7,吸附温度为25℃,吸附时间为2.0 h,溶菌酶初始浓度为0.30 mg·mL-1,最大吸附容量为35.0 mg·g-1。修饰后的磁性纳米粒子用于从鸡蛋清中提取溶菌酶,纯化倍数为30.9,酶活力收得率为73.0%。     

Preparation, structure, and magnetic properties of polystyrene coated by Fe3O4 nanoparticles

A novel method of fabricating core-shell structure particles, comprising nearly monodisperse polystyrene (PS) spheres as cores and Fe3O4 as shells, is submitted. In this research, the magnetite (Fe3O4) shell was prepared by seeded growth from the reaction of FeCl2 with diethylene glycol (DEG) in aqueous solutions. The thickness of the shell were controlled in the range of 0-60 nm by using slow injection. The composition and the structure of the shell were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), thermogravimetric analysis (TG), and vibrating-sample magnetometry (VSM). It is found that there are some differences between the magnetic composite spheres shelled with Fe3O4 and pure Fe3O4 particles, such as the size of the magnetites and the ferromagnetic property. Furthermore, the spheres exhibited the superparamagnetic characterization when the thickness of the Fe3O4 shell was less than 15 nm.