Drug-loaded and superparamagnetic iron oxide nanoparticle surface-embedded amphiphilic block copolymer micelles for integrated chemotherapeutic drug delivery and MR imaging

We report on the fabrication of organic/inorganic hybrid micelles of amphiphilic block copolymers physically encapsulated with hydrophobic drugs within micellar cores and stably embedded with superparamagnetic iron oxide (SPIO) nanoparticles within hydrophilic coronas, which possess integrated functions of chemotherapeutic drug delivery and magnetic resonance (MR) imaging contrast enhancement. Poly(ε-caprolactone)-b-poly(glycerol monomethacrylate), PCL-b-PGMA, and PCL-b-P(OEGMA-co-FA) amphiphilic block copolymers were synthesized at first by combining ring-opening polymerization (ROP), atom transfer radical polymerization (ATRP), and post- modification techniques, where OEGMA and FA are oligo(ethylene glycol) monomethyl ether methacrylate and folic acid-bearing moieties, respectively. A model hydrophobic anticancer drug, paclitaxel (PTX), and 4 nm SPIO nanoparticles were then loaded into micellar cores and hydrophilic coronas, respectively, of mixed micelles fabricated from PCL-b-PGMA and PCL-b-P(OEGMA-co-FA) diblock copolymers by taking advantage of the hydrophobicity of micellar cores and strong affinity between 1,2-diol moieties in PGMA and Fe atoms at the surface of SPIO nanoparticles. The controlled and sustained release of PTX from hybrid micelles was achieved, exhibiting a cumulative release of ~61% encapsulated drugs (loading content, 8.5 w/w%) over ~130 h. Compared to that of surfactant-stabilized single SPIO nanoparticles (r(2) = 28.3 s(-1) mM(-1) Fe), the clustering of SPIO nanoparticles within micellar coronas led to considerably enhanced T(2) relaxivity (r(2) = 121.1 s(-1) mM(-1) Fe), suggesting that hybrid micelles can serve as a T(2)-weighted MR imaging contrast enhancer with improved performance. Moreover, preliminary experiments of in vivo MR imaging were also conducted. These results indicate that amphiphilic block copolymer micelles surface embedded with SPIO nanoparticles at the hydrophilic corona can act as a new generation of nanoplatform integrating targeted drug delivery, controlled release, and disease diagnostic functions.     

Hierarchical nanostructures of fluorinated and naked Ta2O5 single crystalline nanorods: hydrothermal preparation, formation mechanism and photocatalytic activity for H2 production

The hydrolysis of H(2)TaF(7) when it slowly forms via etching Ta powders with HF and H(2)O(2) under hydrothermal conditions produces hierarchical nanostructures of fluorinated and naked Ta(2)O(5) single-crystalline nanorods, which exhibit a far greater photocatalytic activity for H(2) production than commercial Ta(2)O(5) particles.     

Stereoselective synthesis of the C5-C18 fragment of halichomycin

An efficient and convergent synthesis of the C(5)-C(18) fragment of halichomycin is reported. Butanolide fragment 6 was readily prepared stereoselectively from (R)-Roche ester through catalyst control; dienylic bromide domain 7 was synthesized from (S)-serine by substrate control. C(5)-C(18) fragment 2 was rapidly assembled through a stereoselective alkylation of the butanolide with the dienylic bromide, followed by functional group transformations.     

Efficient spin-spin scalar coupling mediated C-13 homonuclear polarization transfer in biological solids without proton decoupling

We demonstrate that an efficient C′↔C polarization transfer based on J-coupling can be realized under fast magic-angle spinning (MAS) condition without ¹H decoupling. Experimental results are presented for model crystalline compounds as well as a non-crystalline 17-residue polypeptide MB(i+4)EK. Measurements on MB(i+4)EK demonstrate that 53% of the initial C′ polarization was transferred to the cross peaks at 7.05 T under 25 kHz MAS spinning.     

Colloidal CdSe nanocrystals synthesized in noncoordinating solvents with the addition of a secondary ligand: exceptional growth kinetics

The addition of a secondary ligand, trioctylphosphine oxide, in the synthesis of cadmium selenide nanocrystals performed in a system with oleic acid as the primary ligand and octadecene as the noncoordinating solvent gives rise to the improvement of nanocrystal size distribution. This phenomenon, which is more significant in the nucleation process than in the growth process, demonstrates that the existence of trioctylphosphine oxide allows for superior nucleation control and permits the facile and reproducible production of extremely small CdSe nanocrystals with narrow size distribution. A systematic study of the nanocrystal formation processes shows that the well-established colloidal nanocrystal growth mechanism, in which nucleation is followed by focusing of size distribution and ended with defocusing of size distribution, cannot be applied to our reactions. Instead, we observed an exceptional type of growth mechanism in which, after nucleation, clear defocusing instead of focusing follows; then slight focusing occurs.     

Platinum oxide catalyzed silylation of aryl halides with triethylsilane: an efficient synthetic route to functionalized aryltriethylsilanes

[STRUCTURE: SEE TEXT] The first platinum-catalyzed selective silylation of aryl halides including aryl iodides and bromides having an electron-withdrawing group is described. The reaction takes place rapidly in NMP with triethylsilane as a silicon source and sodium acetate to provide functionalized aryltriethylsilanes in moderate to good yields. Heteroaromatic halides also were found to be readily silylated with triethylsilane. The procedure is chemoselective and tolerates a wide variety of functional groups.     

The effect of the size of raw Gd(OH)3 precipitation on the crystal structure and PL properties of Gd2O3:Eu

Our experiments show that cetyltrimethylammonium bromide (CTAB) has an obvious effect on the particle size of the precipitation of Gd(OH)3. Without CTAB, the particle size of the Gd(OH)3 precipitation is about 50 nm, whereas with CTAB, the particle size is less than 5 nm. We propose a mechanism where CTAB micelles work as a catalyst for the nucleation process and result in the precipitation of 5 nm particles. These small particles, after heat treatment at 1073 K, did not result in small Gd2O3 nanoparticles of the same size, but instead, forming crystals of 30-80 nm size in both cubic and monoclinic phases. When monitoring the photoluminescence (PL) peak at 610 nm, we found that the charge transfer state (CTS) absorption amplitude of Eu-O is reduced in the mixed structures. We speculate that the mixed structures modify the surface properties of the Gd2O3:Eu nanoparticles, leading to the reduction of Eu-O CTS absorption.     

Stereoretentive Copper‐Catalyzed Directed Thioglycosylation of C(sp2)−H Bonds of Benzamides

An efficient thioglycosylation of C(sp²)?H bonds with thiosugars has been established for the first time. Using only Cu(OAc)₂?H₂O as a catalyst and Ag₂CO₃ as an additive in DMSO, the protocol proved to have broad scope, and a variety of complex thioglycosides have been prepared in good yields with exclusive β‐selectivity.     

基于安全驾驶的元胞自动机交通流模型

针对Nagel-Schreckenberg模型(NaSch模型)中存在的高速车辆可能发生追尾事故的不安全性，考虑了前车速度为零的情况，提出一种新的强调驾驶安全性的一维元胞自动机交通流模型：安全驾驶模型，并对该模型进行了数值模拟.由于安全概率的引入，使得系统在临界密度附近出现低速的同步相，而不是完全的堵塞相，减小了追尾事故发生的可能性，提高了高密度时道路的通行能力.模拟结果显示出了亚稳态、非平衡相变以及滞后效应等实际交通所具有的特性. 关键词： 交通流 安全驾驶 元胞自动机 同步流