Grafting of titanium dioxide microspheres with a temperature‐responsive polymer via surface‐initiated atom transfer radical polymerization without the use of silane coupling agents

Titania microspheres with narrow size distribution and diameters of about 1 µm were prepared and subsequently functionalized using surface‐initiated atom transfer radical polymerization (ATRP) of N‐isopropylacrylamide. The ATRP initiator was immobilized on the particle surface via acylation of surface hydroxyl groups with α‐bromoisobutyryl bromide. Subsequently, an established ATRP reaction system was used for the preparation of titania surface‐grafted poly(N‐isopropylacrylamide) (PNiPAAm). Characterization was performed with electron microscopies, X‐ray diffraction, infrared spectroscopy and dynamic light scattering. It was found that the particle size in aqueous dispersions changed reversibly with temperature as expected for a shell of PNiPAAm, a polymer with a lower critical solution temperature at 32 °C. This confirmed the successful preparation of functional, stimuli‐responsive TiO₂ microparticles via a straightforward controlled surface‐initiated polymerization method.     

陶瓷UO2畸形球的控制方法

研究了用于高温气冷核反应堆燃料核芯中畸形球的种类、产生机理及其控制方法。在500 ℃以下空气中进行了脱碳研究，结果发现破裂球(缺裂球、沟槽球等)的产生基本上来源于干球的不完全脱碳所致。在振动分散条件下进行了溶胶的分散研究。结果发现，孪生球和椭圆球的形成基本上来源于溶胶的不均匀分散所致。因此，为了控制和防止上述两类畸形球的形成，最重要的方法是，(1)必须在一定脱碳程序下供给必要的空气量，确保脱碳完全；(2)必须采用合理的溶胶参数下保持均匀分散，以保证球形均匀。     

Simple and Sensitive HPLC Method with Fluorescence Detection for the Measurement of Ibuprofen in Rat Plasma: Application to a Long-Lasting Dosage Form

A simple and sensitive high-performance liquid chromatography (HPLC) assay applied to the measurement of ibuprofen in rat plasma has been developed. Two parameters have been investigated to improve ibuprofen detectability using fluorescence detection: variation of mobile phase pH and the use of β-cyclodextrin (β-CD). Increasing the pH value from 2.5 to 6.5 and adding 5 mM β-CD enhanced the fluorescence signal (λ_exc = 224 nm; λ_em = 290 nm) by 2.5 and 1.3-fold, respectively, when using standards. In the case of plasma samples, only pH variation significantly lowered detection and quantification limits, down to 10 and 35 ng/mL, respectively. Full selectivity was obtained with a single step for plasma treatment, that is, protein precipitation with acidified acetonitrile. The validated method was applied to a pharmacokinetic study of ibuprofen encapsulated in microspheres and subcutaneously administered to rats.     

Ketoprofen Spray-dried Microspheres Based on Eudragit® RS and RL: Study of the Manufacturing Parameters

The preparation of ketoprofen spray-dried microspheres can be affected by the long drug recrystallization time. Polymer type and drug–polymer ratio as well as manufacturing parameters affect the preparation. The purpose of this work was to evaluate the possibility to obtain ketoprofen spray-dried microspheres using the Eudragit® RS and RL; the influence of the spray-drying parameters on morphology, dimension, and physical stability of microspheres was studied. Ketoprofen microspheres based on Eudragit® blend can be prepared by spray-drying and the nebulization parameters do not influence significantly particle properties; nevertheless, they can be affected by drying and storage methods. No effect of the container material is found.     

Preparation of monodisperse hydrophilic polymer microspheres with N,N′‐methylenediacrylamide as crosslinker by distillation precipitation polymerization

Highly crosslinked cauliflower‐like poly(N,N′‐methylenebisacrylamide) particles were prepared by distillation precipitation polymerization in neat acetonitrile with 2,2′‐azobisisobutyronitrile as initiator. Monodisperse hydrophilic polymer microspheres with various functional groups, such as amide, pyrrolidone and carboxylic acid, with a spherical shape and smooth surface in the size range 120–600 nm were prepared by distillation precipitation copolymerizations of functional comonomers including N‐isopropylacrylamide, N‐vinylpyrrolidone, methacrylic acid with N,N′‐methylenebisacrylamide as crosslinker. The polymer particles were formed and precipitated out from the reaction medium during the distillation of the solvent from the reaction system through an entropic precipitation manner. The effects of the solvent and the degree of crosslinking on the morphology and the loading capacity of the functional groups of the resultant polymer particles were investigated. The resulting polymer particles were characterized with scanning electron microscopy, transmission electron microscopy, dynamic light scattering and Fourier transform infrared spectroscopy. Copyright © 2007 Society of Chemical Industry     

Subpixel position measurement using 1D, 2D and 3D centroid algorithms with emphasis on applications in confocal microscopy

The accuracy with which centroid algorithms in 1D, 2D and 3D can estimate an object's position has been investigated. Three factors that can influence the method's accuracy have been investigated: systematic error of the algorithm, influence of photon noise and the influence of perturbations such as scanning nonlinearity. The variation of the accuracy with parameters that are relevant for confocal microscopy, such as object diameter and photon noise/pixel, has been considered. Theory and simulations presented show that the variation of the accuracy with respect to such parameters can differ drastically between the 1D, 2D and 3D cases. Experiments performed using microspheres show that the magnitudes of the three types of error can be approximately the same under normal operating conditions and that it is therefore necessary to take all three into account when assessing the total error.     

Magnetite‐coated polystyrene hybrid microspheres prepared by miniemulsion polymerization

Hybrid microspheres with a polystyrene core coated with magnetite nanoparticles were prepared by miniemulsion polymerization. Acrylic acid was used as a comonomer to promote the anchoring of the magnetite nanoparticles onto the polymeric surface. The addition of a hydrophobic agent prevents effectively the monomer from diffusing into the aqueous phase. Magnetite was treated with a silane coupling agent in order to introduce some interactions with the polymers. The morphology and the structure of the hybrid microspheres were characterized using X‐ray diffraction, infrared spectroscopy, transmission electron microscopy and thermogravimetric analysis. The results show that the morphology of the hybrid microspheres was influenced by the concentrations of acrylic acid, hydrophobic agent and surfactant, and that the degree of coating can be tuned by changing these parameters. The miniemulsion polymerization technique is adaptable to the synthesis of magnetite‐coated polymer particles, and the synthesis can be scaled up. Copyright © 2008 Society of Chemical Industry     

喷雾干燥法制备亚微米鞣酸铁/硝胺炸药复合微球及其催化性能

为了研究鞣酸铁催化剂对固体推进剂中常见组分热分解性能的影响,采用超声喷雾干燥法制得三种亚微米复合微球(鞣酸铁(Ta-Fe)/六硝基六氮杂异伍兹烷(CL-20)、鞣酸铁/黑索今(RDX)、鞣酸铁/奥克托今(HMX))。利用扫描电镜(SEM)和粒度分析等方法分别对复合微球的形貌、粒度和组分进行表征。采用差示扫描量热法(DSC)研究复合微球中鞣酸铁对CL-20、RDX、HMX热分解的催化过程及动力学参数的影响。结果表明,鞣酸铁分布均匀,样品均呈球状颗粒,且流散性好,粒度为500~1000 nm;鞣酸铁能有效促进CL-20、RDX、HMX的热分解,使得CL-20、RDX、HMX的热分解峰温分别提前了17.2,8.2,11.5℃,其中鞣酸铁对CL-20的热分解催化效果最佳,Ta-Fe/CL-20复合微球的活化能与原料CL-20相比降低了9.6 kJ·mol……-1。     

Fe_3O_4/羧甲基壳聚糖磁性载药微球的制备及释药性能

通过乳化交联法制备了负载有抗癌药物5-氟尿嘧啶的Fe3O4/羧甲基壳聚糖磁性载药微球。利用红外光谱(IR)和扫描电镜(SEM)对载药微球的结构与形貌进行了表征,研究了影响载药微球载药和释药性能的因素。IR测试显示载药微球中含有磁性Fe3O4;SEM照片显示载药微球尺寸均一,表面光滑。确定制备磁性载药微球的最佳条件为:5-氟尿嘧啶0.5g、磁性Fe3O40.2g、戊二醛8mL;磁性载药微球在温度为35~40℃、pH值为5.2的缓冲溶液中释药量达到峰值,适用于人体十二指肠肿瘤的治疗。     

一种合成PS/Ag复合微球的简便方法

本文提出一种制备具有高金属覆载率及良好均匀性的PS/Ag复合微球的简便方法,可以避免PS微球的表面修饰。首先通过多元醇法制备具有良好单分散性的PVP覆盖的Ag纳米颗粒, 然后通过溶胀-异质凝聚法将这些Ag纳米颗粒负载于PS球上。对Ag纳米颗粒的尺寸分布及PS/Ag复合微球的表面形貌进行了研究,结果表明这种方法制得的PS/Ag复合微球具有良好的分散性与均一性,并且Ag颗粒的负载率可以通过Ag溶胶的加入量来调控。