Preparation and surface modification of magnetic poly(methyl methacrylate) microspheres

~~Preparation and surface modification of magnetic poly(methyl methacrylate) microspheres~~     

Extraction and Detection of mRNA from a Single K562 Cell Based on the Functionalized Superparamagnetic Nanoparticles

A novel and promising method was developed to extract mRNA from a single cell based on the functionalized superparamagnetic nanoparticles. The oligo(dT)‐coupled magnetite nanobeads were synthesized by the reaction of oligo(dT) and thiol‐modified γ‐Fe₂O₃ nanoparticles. The single cell was isolated from the massive cultivation according to a semi‐quantum approaching technique and then lysed before mRNA separation. The oligo(dT)‐coupled magnetite nanobeads were added to the crude lysates and then magnetic separation was preformed to get mRNA. The mRNA amplification through a two‐step RT‐PCR method was achieved. The agarose gel electrophoresis of PCR products after amplification shows that mRNA could be extracted from a single cell successfully.     

Hydrothermal preparation and characterization of ZnFe2O4 magnetic nanoparticles as an efficient heterogeneous catalyst for the synthesis of multi‐substituted imidazoles and study of their anti‐inflammatory activity

Nanoparticles are key focus of research for a wide range of novel applications. As such, ZnFe₂O₄ magnetic nanoparticles were synthesized hydrothermally and characterized via scanning and transmission electron microscopies, powder X‐ray diffraction, energy‐dispersive X‐ray and infrared spectroscopies, thermogravimetric analysis and magnetic measurements. They were used as a robust catalyst for the synthesis of a series of biologically active multi‐substituted imidazoles using a multicomponent reaction by the reaction of benzil with various aromatic aldehydes, ammonium acetate and aliphatic amines (N,N‐dimethyl‐1,3‐propanediamine and 1‐amino‐2‐propanol) under solvent‐free conditions. The key advantages of this method are shorter reaction times, very high yield and ease of operation. The thermally and chemically stable, benign and economical catalyst was easily recovered using an external magnet and reused in at least five successive runs without an appreciable loss of activity. All of these novel synthesized compounds were characterized from spectral data and their purities were checked using thin‐layer chromatography, giving one spot. Furthermore, the prepared compounds were tested for their anti‐inflammatory activity.     

Design and FESEM/EDX investigation of functional magnetic nanocomposite particles

Recently, magnetic nanoparticles and nanocomposite microspheres have attracted great interest for biomedical and technical application. Magnetic metal nanoparticles are of special interest due to their beneficial, size‐dependent magnetic properties. Superparamagnetic metal nanoparticles and mesoscale nanocomposite particles (viz. Co nanoparticles, Co@SiO₂, and Co@SiO₂@TiO₂ particles) were obtained by a three‐step synthesis, involving consecutive steps of thermolysis and sol–gel procedures. A high‐resolution Schottky‐type field emission scanning electron microscope (FESEM) equipped with an energy dispersive X‐ray spectrometer was used to characterize intermediate and final products at the successive stages of synthesis. The samples were deposited on carbon‐coated transmission electron microscopy (TEM) grids (thin film technique) which afforded enhanced specimen contrast and reduced X‐ray background contribution in microanalysis. The FESEM was equipped with a special mounting device for these grids with an appropriate detector beneath. By this method, the samples, covering sizes from the nanometer to micron scale, could be characterized and analyzed by several imaging modes, viz. with standard SE and BSE detection mode and supplementary with low‐voltage scanning transmission mode (STEM‐in‐SEM) and fundamental information about particle size, morphology, and elemental distribution was obtained. Copyright © 2012 John Wiley & Sons, Ltd.     

Monodisperse superparamagnetic pH‐sensitive single‐layer chitosan hollow microspheres with controllable structure

Facile strategy was developed for the fabrication of the monodisperse superparamagnetic pH‐sensitive single‐layer chitosan (CS) hollow microspheres with controllable structure. The carboxyl group‐functionalized polystyrene microspheres prepared by soap‐free emulsion polymerization were used as the templates. After the Fe₃O₄ nanoparticles were in situ formed onto the surface of the templates, the single‐layer CS was self‐assembled and cross‐linked with glutaraldehyde subsequently. Then, the magnetic single‐layer CS hollow microspheres were obtained after the templates were removed. It was found that the feeding ratio of the monomer acrylic acid in the soap‐free emulsion polymerization had played an important role on the particle size and surface carboxyl group content of the templates, which determined the particle size and shell thickness of the magnetic single‐layer CS hollow microspheres in the proposed strategy. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Quadruple‐Responsive Nanocomposite Based on Dextran–PMAA–PNIPAM,Iron Oxide Nanoparticles,and Gold Nanorods

A quadruple‐responsive nanocomposite that responds to temperature, pH, magnetic field, and NIR is obtained by incorporating superparamagnetic iron oxide nanoparticles (SPIONs) and gold nanorods (AuNRs) into a dextran‐based smart copolymer network. The dual‐sensitive copolymer is prepared by sequential RAFT polymerization of methacrylic acid and N‐isopropylacrylamide from trithiocarbonate groups linked to dextran in one pot. These functionalized nanocomposites with superior stability can respond to the four stimuli mentioned above well. As evidenced by UV–vis and TEM measurements, the temperature‐induced unusual blue‐shift in the longitudinal plasmon band is possibly due to the side‐to‐side assembly of AuNRs.     

Kinetics of Magnetic Field‐Induced Orientational Ordering in Block Copolymer/Superparamagnetic Nanoparticle Composites

The combination of external potential dynamics and Brownian dynamics is introduced to study the kinetics of orientational ordering in block copolymer/superparamagnetic nanoparticle composites where the particles are smaller than the domain spacing and preferentially segregate into one block of the copolymer. This simulation method accounts for both excluded volume interactions and dipolar interactions between particles to quantify alignment kinetics. Two‐dimensional simulations reveal that higher dipolar interaction strengths lead to faster alignment of the block copolymer, where the orientation kinetics obeys an exponential rate law. The observed rate of alignment increases with increasing dipolar interaction strength and is dependent on the initial state of the block copolymer. The primary mechanism of orientational ordering is found to be the redistribution of monomer segments leading to bridging and growth of the block copolymer domains around the nanoparticles.

     

H2O2氧化法制备Fe3O4纳米颗粒及与共沉淀法制备该样品的比较

在近中性条件下，利用H₂Ｏ₂氧化Fe(OH)2胶体成功制备了Fe₃ Ｏ₄纳米颗粒.分别利用透射电镜(TEM)，x射线衍射仪(XRD)，振动样品磁强计(VSM)和超导量子干涉仪（SQUI D）对样品的形貌，结构，宏观磁性进行了表征和测量.TEM图像表明样品为球形颗粒，直径 大小约18nm，且分布较均匀.XRD结果表明样品为立方尖晶石结构.穆斯堡尔谱测量表明样品 室温下对应两套六线谱，样品的晶体结构存在缺陷，内磁场略小于块体Fe₃Ｏ4的值. 宏观磁测量表明样品的饱和磁化强度可达67×10^-3A·m²/g，在20 K出现了Verw ey转变.选择该法制备的Fe₃Ｏ₄纳米颗粒与共沉淀法得到的样品作 了磁性比较.宏观磁 测量表明共沉淀法制备的样品在外磁场为1T时仍未饱和，磁化强度仅为46×10^-3A·m²/g，在178K出现了超顺磁转变温度，且在测量温度范围内没有发现Verwe y转变. 关键词： 亚铁磁 超顺磁 穆斯堡尔谱     

Engineering the Internal Structure of Magnetic Silica Nanoparticles by Thermal Control

Calcination of hydrated iron salts in the pores of both spherical and rod‐shaped mesoporous silica nanoparticles (NPs) changes the internal structure from an ordered 2D hexagonal structure into a smaller number of large voids in the particles with sizes ranging from large hollow cores down to ten nanometer voids. The voids only form when the heating rate is rapid at a rate of 30 °C min^?1. The sizes of the voids are controlled reproducibly by the final calcination temperature; as the temperature is decreased the number of voids decreases as their size increases. The phase of the iron oxide NPs is α‐Fe₂O₃ when annealed at 500 °C, and Fe₃O₄ when annealed at lower temperatures. The water molecules in the hydrated iron (III) chloride precursor salts appear to play important roles by hydrolyzing Si? O? Si bonding, and the resulting silanol is mobile enough to affect the reconstruction into the framed hollow structures at high temperature. Along with hexahydrates, trivalent Fe³⁺ ions are assumed to contribute to the structure disruption of mesoporous silica by replacing tetrahedral Si⁴⁺ ions and making Fe? O? Si bonding. Volume fraction tomography images generated from transmission electron microscopy (TEM) images enable precise visualization of the structures. These results provide a controllable method of engineering the internal shapes in silica matrices containing superparamagnetic NPs.