Thermal Properties of Copoly(L‐lactic acid/glycolic acid) by Direct Melt Polycondensation

Poly(L‐lactic acid‐co‐glycolic acid) (PLGA) was prepared from hydroxy‐acids with melt polymerization. In this way, the copoly(L‐LA/GA) (PLGA) was synthesized directly using a binary catalyst (tin chloride dihydrate/p‐toluenesulfonic acid). The thermal properties of PLGA were studied by differential scanning calorimetry (DSC) and nuclear magnetic resonance (NMR). The results show that the melting point of PLGA decreases with increasing mole fraction of GA units in the copolymer. In addition, the melting point of polymer also decreases with increasing degree of racemization of the polymer.     

A UFLC‐MS/MS method with a switching ionization mode for simultaneous quantitation of polygalaxanthone III,four ginsenosides and tumulosic acid in rat plasma: application to a comparative pharmacokinetic study in normal and Alzheimer's disease rats

A fast, sensitive and reliable ultra fast liquid chromatography‐tandem mass spectrometry (UFLC‐MS/MS) method has been developed and validated for simultaneous quantitation of polygalaxanthone III (POL), ginsenoside Rb1 (GRb1), ginsenoside Rd (GRd), ginsenoside Re (GRe), ginsenoside Rg1 (GRg1) and tumulosic acid (TUM) in rat plasma after oral administration of Kai‐Xin‐San, which plays an important role for the treatment of Alzheimer's disease (AD). The plasma samples were extracted by liquid–liquid extraction using ethyl acetate–isopropanol (1:1, v/v) with salidrdoside as internal standard (IS). Good chromatographic separation was achieved using gradient elution with the mobile phase consisting of methanol and 0.01% acetic acid in water. The tandem mass spectrometric detection was performed in multiple reaction monitoring mode on 4000Q UFLC‐MS/MS system with turbo ion spray source in a negative and positive switching ionization mode. The lower limits of quantification were 0.2–1.5 ng/ml for all the analytes. Both intra‐day and inter‐day precision and accuracy of analytes were well within acceptance criteria (±15%). The mean absolute extraction recoveries of analytes and IS from rat plasma were all more than 60.0%. The validated method has been successfully applied to comparing pharmacokinetic profiles of analytes in normal and AD rat plasma. The results indicated that no significant differences in pharmacokinetic parameters of GRe, GRg1 and TUM were observed between the two groups, while the absorption of POL and GRd in AD group were significantly higher than those in normal group; moreover, the GRb1 absorbed more rapidly in model group. The different characters of pharmacokinetics might be caused by pharmacological effects of the analytes. Copyright © 2013 John Wiley & Sons, Ltd.     

Synthesis and biological evaluation of novel triazole derivatives as antifungal agents

A series of 1-(benzylamino)-2-(2,4-difluorophenyl)-3-(1H-1,2,4-triazol-l-yl)propan-2-ols compounds were synthesized and evaluated for their antifungal activities in vitro.The results showed that compounds 6A and 6B exhibited good antifungal activity.Compound 6A8 showed the strongest antifungal activity,which was significantly higher than that of the lead compounds and positive-control drugs Fluconazole and Itraconazole.In particular,the antifungal activity of compound 6A8 against Candida albicans and Candida krusei(MIC80 both at 0.00097μg/mL) was 515 and 64 times that of Fluconazole,respectively.The structure-activity relationships of the synthesized compounds were discussed,and the docking model of the target compounds with fungal lanosterol 14α-demethylase (CYP51) was analyzed.     

人工纳米材料与植物的相互作用:植物毒性、吸收和传输

近十几年来纳米科技取得了突飞猛进的发展,人工纳米材料的应用日益广泛,势必导致大量纳米材料进入生态环境中,因此纳米材料可能带来的环境污染和生态效应也受到了高度关注。越来越多的研究表明,纳米材料对微生物、水生和陆生动物和植物都具有一定的毒性效应。植物是生态系统的重要组成部分,一方面纳米材料可能影响植物的发育与生长;另一方面,植物的代谢活动会影响纳米材料在环境中的迁移转化行为及其在食物网中的传递。但是,目前关于纳米材料与植物相互作用的研究还十分匮乏,多数研究只局限于相互作用导致的表观现象,例如:毒性的研究多关注于纳米材料对植物或植物细胞的表观毒性效应,缺乏对致毒机制的探讨;纳米材料的植物吸收和传输研究也仅停留在现象观察阶段,缺乏对吸收与传输机理的深入研究。而且很多研究结论还存在较大的争议,因此非常有必要对相关的研究进展与结论做全面梳理。本文综述了近年来关于纳米材料与植物相互作用的研究,从植株到植物细胞水平讨论了不同纳米材料对植物的毒性效应以及纳米材料的植物吸收和传输过程。     

ZSM-5高硅分子筛硅烷化疏水改性的研究

以甲苯为溶剂,正辛基三乙氧基硅烷(OTS)为改性剂,进行了ZSM-5高硅分子筛疏水改性研究。通过傅立叶红外(FT-IR)、X射线粉末衍射(XRD)、N2吸附-解吸附、静态水接触角、水与正己烷的静态吸附,以及水热稳定性试验等测试了改性前后样品结构与性能。结果表明,通过硅烷化改性在ZSM-5上接枝了-Si(CH2)7CH3基团,并实现了超疏水性。当0.8g ZSM-5使用0.24g改性剂时,改性后分子筛的接触角达152°,水吸附量下降了1.49%,比表面积、孔容、孔径分别减小了62.7m2/g、0.0329cm3/g、0.42nm,孔道长程有序性有所降低,且具有较高的水热稳定性。     

Polypeptide/Doxorubicin Hydrochloride Polymersomes Prepared Through Organic Solvent‐free Technique as a Smart Drug Delivery Platform

Rapid and efficient side‐chain functionalization of polypeptide with neighboring carboxylgroups is achieved via the combination of ring‐opening polymerization and subsequent thiol‐yne click chemistry. The spontaneous formation of polymersomes with uniform size is found to occur in aqueous medium via electrostatic interaction between the anionic polypeptide and cationic doxorubicin hydrochloride (DOX·HCl). The polymersomes are taken up by A549 cells via endocytosis, with a slightly lower cytotoxicity compared with free DOX ·HCl. Moreover, the drug‐loaded polymersomes exhibit the enhanced therapeutic efficacy, increase apoptosis in tumor tissues, and reduce systemic toxicity in nude mice bearing A549 lung cancer xenograft, in comparison with free DOX ·HCl.     

Highly porous magnetite/graphene nanocomposites for a solid-state electrochemiluminescence sensor on paper-based chips

Graphene-nanosheet-based highly porous magnetite nanocomposites (GN-HPMNs) have been prepared using a simple solvothermal method and used as an immobilization matrix for the fabrication of a solid-state electrochemiluminescence (ECL) sensor on paper-based chips. Highly porous Fe₃O₄ nanocrystal clusters were coated with acrylate and wrapped tightly on the skeleton of graphene nanosheets. The structures and sizes of the GN-HPMNs could be tuned by varying the proportions of the solvents ethylene glycol and diethylene glycol. Then, the relatively highly porous ones with an average diameter of about 65 nm were combined with Nafion to form composite films on an electrode surface for immobilization of Ru(bpy)₃ ²⁺ (bpy is 2,2′-bipyridine). Because of their porosity, negatively charged surface, and cooperative characteristics of magnetic nanomaterials and graphene, under an external magnetic field, the GN-HPMNs ensured effective immobilization, excellent electron transfer, and long-term stability of Ru(bpy)₃ ²⁺ in the composite film. The sensor developed exhibited excellent reproducibility with a relative standard deviation of 0.65 % for 30 continuous cycles. It was found to be much more favorable for detecting compounds containing tertiary amino groups and DNAs with guanine and adenine. A detection limit (signal-to-noise ratio of 3) of 5.0 nM was obtained for tripropylamine. As an application example, 0.5 nM single-nucleotide mismatch could be detected. This was the first attempt to introduce magnetic nanomaterials and an external magnetic field into paper-based chips. The sensor developed has the advantages of high sensitivity, good stability, and wide potential applicability as well as simplicity, low cost, and good disposability.