In situ fabrication of paclitaxel‐loaded core‐crosslinked micelles via thiol‐ene “click” chemistry for reduction‐responsive drug release

In this study, a facile method to fabricate reduction‐responsive core‐crosslinked micelles via in situ thiol‐ene “click” reaction was reported. A series of biodegradable poly(ether‐ester)s with multiple pendent mercapto groups were first synthesized by melt polycondensation of diol poly(ethylene glycol), 1,4‐butanediol, and mercaptosuccinic acid using scandium trifluoromethanesulfonate [Sc(OTf)₃] as the catalyst. Then paclitaxel (PTX)‐loaded core‐crosslinked (CCL) micelles were successfully prepared by in situ crosslinking hydrophobic polyester blocks in aqueous media via thiol‐ene “click” chemistry using 2,2′‐dithiodiethanol diacrylate as the crosslinker. These PTX‐loaded CCL micelles with disulfide bonds exhibited reduction‐responsive behaviors in the presence of dithiothreitol (DTT). The drug release profile of the PTX‐loaded CCL micelles revealed that only a small amount of loaded PTX was released slowly in phosphate buffer solution (PBS) without DTT, while quick release was observed in the presence of 10.0 mM DTT. Cell count kit (CCK‐8) assays revealed that the reduction‐sensitive PTX‐loaded CCL micelles showed high antitumor activity toward HeLa cells, which was significantly higher than that of reduction‐insensitive counterparts and free PTX. This kind of biodegradable and biocompatible CCL micelles could serve as a bioreducible nanocarrier for the controlled antitumor drug release. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 99–107     

Mass and isotopic concentrations of water-insoluble refractory carbon in total suspended particulates at Mt.Waliguan Observatory(China)

Mass concentration and isotopic values δ¹³C and ¹⁴C are presented for the water-insoluble refractory carbon（WIRC） component of total suspended particulates（TSP）,collected weekly during 2003,as well as from October 2005 to May 2006 at the WMO-GAW Mt.Waliguan（WLG） site.The overall average WIRC mass concentration was（1183±120）ng/m³（n = 79）,while seasonal averages were 2081 ±1707（spring）,454±205（summer）,650±411（autumn）,and 1019±703（winter） ng/m3.Seasonal variations in WIRC mass concentrations were consistent with black carbon measurements from an aethalometer,although WIRC concentrations were typically higher,especially in winter and spring.The δ¹³C PDB value（-25.3 ± 0.8）%.determined for WIRC suggests that its sources are C₃ biomass or fossil fuel combustion.No seasonal change in δ¹³C PDB was evident.The average percent Modern Carbon（pMC） for ¹⁴C in WIRC for winter and spring was（67.2 ± 7.7）%（n = 29）.Lower pMC values were associated with air masses transported from the area east of WLG,while higher pMC values were associated with air masses from the Tibetan Plateau,southwest of WLG.Elevated pMC values with abnormally high mass concentrations of TSP and WIRC were measured during a dust storm event.     

Stereoselective Preparation of Polyfunctional Alkenylindium(III) Halides and Their Cross‐Coupling with Unsaturated Halides

The direct insertion of indium powder to cycloalkenyl iodides in the presence of LiCl in THF allows the preparation of new highly functionalized cycloalkenylindium(III) derivatives. In addition, we discovered that, in contrast to many metal insertions to alkenyl iodides which proceed with a loss of stereochemistry, the insertion of In/LiCl to stereodefined (Z)‐ and (E)‐styryl iodides in THF proceeded with high retention of stereochemistry. After a palladium‐catalyzed cross‐coupling, various polyfunctionalized (Z)‐ and (E)‐stilbenes were obtained with high stereoselectivity.     

Octahedral Chiral‐at‐Metal Iridium Catalysts: Versatile Chiral Lewis Acids for Asymmetric Conjugate Additions

Octahedral iridium(III) complexes containing two bidentate cyclometalating 5‐tert‐butyl‐2‐phenylbenzoxazole ( IrO ) or 5‐tert‐butyl‐2‐phenylbenzothiazole ( IrS ) ligands in addition to two labile acetonitrile ligands are demonstrated to constitute a highly versatile class of asymmetric Lewis acid catalysts. These complexes feature the metal center as the exclusive source of chirality and serve as effective asymmetric catalysts (0.5–5.0 mol % catalyst loading) for a variety of reactions with α,β‐unsaturated carbonyl compounds, namely Friedel–Crafts alkylations (94–99 % ee), Michael additions with CH‐acidic compounds (81–97 % ee), and a variety of cycloadditions (92–99 % ee with high d.r.). Mechanistic investigations and crystal structures of an iridium‐coordinated substrates and iridium‐coordinated products are consistent with a mechanistic picture in which the α,β‐unsaturated carbonyl compounds are activated by two‐point binding (bidentate coordination) to the chiral Lewis acid.     

Gold‐Catalyzed Tandem Cycloisomerization–Halogenation of Chiral Homopropargyl Sulfonamides

Two new gold‐catalyzed tandem cycloisomerization–halogenation reactions of chiral homopropargyl sulfonamides have been developed. Various enantioenriched 3,3‐diiodopyrrolidin‐2‐ols and 3‐fluoropyrrolidin‐2‐ols were obtained in moderate‐to‐good yields with excellent enantio‐ and diastereoselectivity.     

Ni–Al composite hydroxides fabricated by cation–anion double hydrolysis method for high-performance supercapacitor

Chemical doping of nickel hydroxide with other cations(e.g. Al~(3+)) is an efficient way to enhance its electrochemical capacitive performances. Herein, a simple cation–anion(Ni~(2+)and AlO_2) double hydrolysis method was developed toward the synthesis of nickel–aluminum(Ni–Al) composite hydroxides. The obtained composite hydroxides possesses a porous structure, large surface area(121 m~2/g) and homogeneous element distribution. The electrochemical test shows that the obtained composite hydroxides exhibits a superior supercapacitive performances(specific capacitance of 1670F/g and rate capability of 87% from 0.5 A/g to 20 A/g) to doping-free nickel hydroxide(specific capacitance of 1227 F/g and rate capability of 47% from 0.5 A/g to 20 A/g). Moreover, the galvanostatic charge/discharge test displays that after 2000 cycles at large current density of 10 A/g, the composite hydroxides achieves a high capacitance retention of 98%, indicative of an excellent electrochemical cycleability.     

One‐Pot Synthesis of Pomegranate‐Structured Fe3O4/Carbon Nanospheres‐Doped Graphene Aerogel for High‐Rate Lithium Ion Batteries

A unique hierarchically nanostructured composite of iron oxide/carbon (Fe₃O₄/C) nanospheres‐doped three‐dimensional (3D) graphene aerogel has been fabricated by a one‐pot hydrothermal strategy. In this novel nanostructured composite aerogel, uniform Fe₃O₄ nanocrystals (5–10 nm) are individually embedded in carbon nanospheres (ca. 50 nm) forming a pomegranate‐like structure. The carbon matrix suppresses the aggregation of Fe₃O₄ nanocrystals, avoids direct exposure of the encapsulated Fe₃O₄ to the electrolyte, and buffers the volume expansion. Meanwhile, the interconnected 3D graphene aerogel further serves to reinforce the structure of the Fe₃O₄/C nanospheres and enhances the electrical conductivity of the overall electrode. Therefore, the carbon matrix and the interconnected graphene network entrap the Fe₃O₄ nanocrystals such that their electrochemical function is retained even after fracture. This novel hierarchical aerogel structure delivers a long‐term stability of 634 mA h g^?1 over 1000 cycles at a high current density of 6 A g^?1 (7 C), and an excellent rate capability of 413 mA h g^?1 at 10 A g^?1 (11 C), thus exhibiting great potential as an anode composite structure for durable high‐rate lithium‐ion batteries.