Low generational polyamidoamine dendrimers to enhance the solubility of folic acid:A‘‘dendritic effect’’investigation

Low generational(G0–G2,G for generation) polyamidoamine(PAMAM) dendrimers were investigated as enhancers to improve the aqueous solubility of folic acid at pH 11 and pH 5.In these two cases,the solubility of folic acid increases with both the dendrimer concentration and generation.However,the solubilization mechanism is different.The electrostatic interaction between the primary amines of dendrimers and the ionized carboxylic groups of folic acid dominates the dissolution process at pH 11 while the increase of the solubility of folic acid at pH 5 is attributed to the hydrophobic encapsulation inside the dendrimer molecules.In addition,for comparison ethylenediamine was used as a small molecule control to examine the ‘‘dendritic effect' in the dendrimer-related solubilization process.Interestingly,PAMAM dendrimers exhibit,at pH 5,a significant superiority over ethylenediamine in enhancing solubility,whereas this ‘‘dendritic effect' cannot be observed under the basic condition.     

Copper Tetrahydrosalen Complex Encapsulated in Zeolite Y： an Effective Heterogeneous Catalyst for the Oxidation of Cycloalkanes

In the last decade, encapsulation of transition metal complexes in zeolites and related materials has been paid much attention, because this type of materials could serve as functional mimic enzymes, possessing both homogeneous-catalysis and heterogeneous…     

Synthesis of magnetic DDAB vesicles

The synthesis of magnetic vesicles is described. The vesicles are constituted by didodecyldimethylammonium bromide and have a diameter of about 1 m. An aqueous magnetic fluid, constituted by charged magnetic nanoparticles dispersed in water without surfactant, is encapsulated in the vesicle with a volume fraction in particles that may range up to 10%. The first step of the encapsulation is the synthesis of a multiple emulsion the intermediate oily phase being evaporated to obtain the DDAB bilayer. The magnetic vesicles thus synthesized align and change shape when a magnetic field is applied.     

Oxidation of dibenzothiophene catalyzed by heme-containing enzymes encapsulated in sol-gel glass

We have encapsulated several hemoproteins in the sol-gel glass to catalyze the oxidation reaction of dibenzothiophene (model for organic sulfur compounds in coal) with hydrogen peroxide. In addition to cytochrome c and myoglobin, which have previously been encapsulated in sol-gel glasses, two other hemoproteins, horseradish peroxidase and bovine blood hemoglobin, have now been successfully immobilized in sol-gel media with the retention of their spectroscopic properties. All four hemoproteins studied also demonstrate similar catalytic activities toward the oxidation of dibenzothiophene as compared with the results obtained with the proteins in solution. In the case of encapsulated cytochrome c, the more water-soluble S-oxide was obtained with much higher selectivity over the less water-soluble sulfone (S-oxide/sulfone = 7.1) as compared to what was obtained in the aqueous/organic medium (S-oxide/sulfone = 2.3). Because of the advantage of easy separation of the encapsulated proteins from the liquid reaction mixture, it is clear from these studies that the immobilization of active hemoproteins in the solid glass media could serve as more practical biocatalysts.     

Iron(III), cobalt(II) and copper(II) complexes bearing 8‐quinolinol encapsulated in zeolite?Y for the aerobic oxidation of styrene

A series of Fe(III), Co(II) and Cu(II) complexes of 8‐quinolinol were encapsulated into the supercages of zeolite? Y and characterized by X‐ray diffraction, SEM, N₂ adsorption/desorption, FT‐IR, UV–vis spectroscopy, elemental analysis, ICP‐AES and TG/DSC measurements. The encapsulation was achieved by a flexible ligand method in which the transition metal cations were first ion‐exchanged into zeolite Y and then complexed with 8‐quinolinol ligand. The metal‐exchanged zeolites, metal complexes encapsulated in zeolite–Y plus non‐encapsulated homogeneous counterparts were all screened as catalysts for the aerobic oxidation of styrene under mild conditions. It was found that the encapsulated complexes always showed better activity than their respective non‐encapsulated counterparts. Moreover, the encapsulated iron complex showed good recoverability without significant loss of activity and selectivity within successive runs. Heterogeneity test for this catalyst confirmed its high stability against leaching of active complex species into solution. Copyright © 2011 John Wiley & Sons, Ltd.     

无皂乳液聚合法制备聚甲基丙烯酸甲酯包覆厚度可控的纳米核-壳二氧化硅微球

用改进的Stöber法和无皂乳液聚合法制备窄分布的二氧化硅/PMMA核-壳纳米微球. 用改进的Stöber法将3-乙氧基甲基丙烯酸丙基硅烷(MPS)修饰在纳米的二氧化硅表面后, 用无皂乳液聚合法制备核-壳纳米微球. 该法简单有效且得到厚度均匀的聚合物包覆层. 随着单体MMA用量的增加, 用动态光散射法测量, PMMA壳层的厚度从6.4 nm增加到96.3 nm. 热重分析表明, PMMA的含量从22.25%增加到93.41%. 扫描电子显微镜和透射电子显微镜结果表明, 得到的是包覆良好、表面光滑的核-壳无机/聚合物纳米微球.     

淀粉基荧光微球的制备及其布洛芬包载和释药性能

以淀粉为原料,用乙酸酐酰化后,将异硫氰酸荧光素（FITC）接枝到淀粉醋酸酯大分子链上,以自组装的方法制备出包载布洛芬的淀粉基荧光微球,同时考察了淀粉基荧光纳米微球对布洛芬的控制释放性能。 荧光淀粉酯的用量、布洛芬的加入量及丙酮与水的体积比可影响载药微球的包封率和药物释放速度。 研究结果表明,当荧光淀粉酯用量为200 mg、布洛芬的量为60 mg、水和丙酮体积分别为50和20 mL时所合成的载药微球包封率最高,为69.5%,其药物体外释放也最快,48 h可释放62.7%。 用扫描电子显微镜和激光共聚焦显微镜(CLSM)对包药微球的体外释放过程进行了表征。     

Nitrile Oxide‐Norbornene Cycloaddition as a Bioorthogonal Crosslinking Reaction for the Preparation of Hydrogels

This communication describes the first application of cycloaddition between an in situ generated nitrile oxide with norbornene leading to a polymer crosslinking reaction for the preparation of poly(ethylene glycol) hydrogels under physiological conditions. Hydrogels with high water content and robust physical strength are readily formed within 2–5 min by a simple two‐solution mixing method which allows 3D encapsulation of neuronal cells. This bioorthogonal crosslinking reaction provides a simple yet highly effective method for preparation of hydrogels to be used in bioengineering.

     

Comparison of Loading Efficiency between Hyperbranched Polymers and Cross‐Linked Nanogels at Various Branching Densities

The effect of branching point structures and densities is studied between azido‐containing hyperbranched polymers and cross‐linked nanogels on their loading efficiency of alkynyl‐containing dendron molecules. Hyperbranched polymers that contained “T”‐shaped branching linkage from which three chains radiated out and cross‐linked nanogels that contained “X”‐shaped branching linkage with four radiating chains are synthesized in microemulsion using either atom transfer radical polymerization (ATRP) or conventional radical polymerization (RP) technique. Both polymers have similar density of azido groups in the structure and exhibit similar hydrodynamic diameter in latexes before purification. Subsequent copper‐catalyzed azide–alkyne cycloaddition reactions between these polymers and alkynyl‐containing dendrons in various sizes (G1–G3) demonstrate an order of dendron loading efficiencies (i.e., final conversion of alkynyl‐containing dendron) as hyperbranched polymers > nanogels synthesized by ATRP > nanogels synthesized by RP. Decreasing the branching density or using smaller dendron molecules increases the click efficiency of both polymers. When G2 dendrons with a molecular weight of 627 Da are used to click with the hyperbranched polymers composed of 100% inimer, a maximum loading efficiency of G2 in the loaded hyperbranched polymer is 58% of G2 by weight. These results represent the first comparison between hyperbranched polymers and cross‐linked nanogels to explore the effect of branching structures on their loading efficiencies.