Polydiacetylene‐Based Electrospun Fibers for Detection of HCl Gas

Polydiacetylenes (PDAs), a family of conjugated polymers, are very intriguing materials in several aspects. Especially, the stimulus‐induced apparent blue‐to‐red transition of the PDAs has led to the development of a variety of PDA‐based chemosensors. In the current work, we synthesized PDA monomers bearing trimethyl amine (PCDA‐DMEDA) and incorporated them with Poly(ethylene oxide) (PEO) into electrospun fibers. For the first time, we successfully demonstrated that PDA‐based electrospun fibers can be used for the naked‐eye detection of HCl gas by simple color change (blue to red).     

季铵盐型Gemini表面活性剂诱导囊泡结构改变机理研究

用动态光散射技术以及荧光探针方法, 研究了不同连接基长度的季铵盐型Gemini表面活性剂对卵磷脂囊泡结构改变的影响, 并借助理论模型和临界堆积参数理论探索了Gemini表面活性剂诱导囊泡结构改变的机理. 实验结果表明, 表面活性剂诱导囊泡结构改变的主要原因是表面活性剂嵌入到囊泡的双分子层中, 从而改变了囊泡的表面电荷强度以及嵌入后的表面活性剂在囊泡双分子层中分布的不均匀性. 此外, 表面活性剂分子的结构也会对其产生影响, 不同连接基长度的季铵盐型Gemini表面活性剂对囊泡结构改变的影响不完全相同, 但会呈现出一定的规律性.     

Dissipative particle dynamics simulation study of the bilayer-vesicle transition

A bilayer structure is an important immediate for the vesicle formation. However,the mechanism for the bilayer-vesicle transition remains unclear. In this work,a dissipative particle dynamics(DPD) simulation method was employed to study the mechanism of the bilayer-vesicle transition. A coarse-grained model was built based on a lipid molecule termed dimyristoylphosphatidylcholine(DMPC). Simulations were performed from two different initial configurations:a random dispersed solution and a tensionless bilayer. It was found that the bilayer-vesicle transition was driven by the minimization of the water-tail hydrophobic interaction energy,and was accompanied with the increase of the position entropy due to the redistribution of water molecules. The bulk pressure was reduced during the bilayer-vesicle transition,suggesting the evolved vesicle morphology was at the relatively low free energy state. The membrane in the product vesicle was a two-dimensional fluid. It can be concluded that the membrane of a vesicle is not interdigitated and most of the bonds in lipid chains are inclined to orient along the radical axis of the vesicle.     

可聚合囊泡体系(烯丙基-二甲基-十二烷基溴化胺和十二烷基硫酸钠)在溶液中的盐效应

高稳定的囊泡广泛用于制作生物模型、药物输送以及合成纳米材料的模板。获得高稳定囊泡结构的重要方法之一是用聚合反应固定囊泡结构。作为可聚合囊泡制备的前期基础工作,研究了一种可聚合的囊泡体系：1-丙烯基－2,2,二甲基－十二烷基溴化胺（ADDB）和ADDB与十二烷基磺酸钠（SDS）的等摩尔比混合体系。该囊泡体系即使在高浓度盐水中也能够自发地形成均相的囊泡溶液。在聚合之前,采用动态激光光散射（DLS）、冷冻蚀刻透射电镜（FF-TEM）技术研究了可聚合囊泡的盐效应。DLS测试发现没有盐存在时,囊泡大小为83 nm,盐的浓度增加到250 mmol/L时,囊泡尺寸增大到250 nm。然而继续增大盐浓度到1000 mmol/L, 囊泡尺寸减小到180nm. FF-TEM结果发现盐浓度小于150 mM时, 单个囊泡为70 nm左右,然而明显存在囊泡的絮凝与融合;当盐浓度增加到400 mM时,单个囊泡尺寸减小到20 nm. 因此DLS 观测到囊泡尺寸增大的原因是由于囊泡的絮凝与融合;而尺寸减小的原因是由于在高盐浓度下,盐屏蔽了带电颗粒之间的静电相互作用,在熵增的驱使下,大囊泡变成小囊泡。     

Electron microscopic and light scattering observation on a system with two iridescent phases

Electron microscopic observations and classical light-scattering measurements have been carried out for dodecyldimethylaminoxide/hexanol/water mixtures in the concentration range where iridescent colors occur. This system has two different iridescent phases. The iridescent phase with more hexanol forms quickly, and the phase with less hexanol forms very slowly. Three different isotropic phases which show strong flow birefringence are found near both iridescent phases. The electron microscopic pictures show clearly that only one of these isotropic phases with strong flow birefringence is a bicontinuous sponge phase (L_3h -phase). This is the phase which comes out by adding some alkanol to the upper lamellar phase. The flow birefringent phase below the lower lamellar phase forms unilamellar vesicles. The flow birefringent phase which occurs between both iridescent phases contains multilamellar vesicles and is shown to be a precursor of a lamellar phase.     

高分子微泡体系中光解水的研究：（Ⅱ）聚卵磷脂微泡在光解水中的应用

本文研究以卵磷脂为单体形成的微泡体系,以Co~(60)辐照为聚合方式,通过超声波作用将联吡啶钌和EDTA,甲基紫精和铂溶胶等光解水的试剂置于微泡的不同区域,从而获得不同的光解水效果。     

Quadrupolar ordering of phospholipid molecules in narrow necks of phospholipid vesicles

Shapes of phospholipid vesicles that involve narrow neck(s) were studied theoretically. It is taken into account that phospholipid molecules are intrinsically anisotropic with respect to the membrane normal and that they exhibit quadrupolar orientational ordering according to the difference between the local principal membrane curvatures. Direct interactions between oriented molecules were considered within a linear approximation of the energy coupling with the deviatoric field. The equilibrium shapes of axisymmetric closed vesicles were studied by minimization of the free energy of the phospholipid bilayer membrane under relevant geometrical constraints. The variational problem was stated by a system of Euler-Lagrange differential equations that revealed a singularity in the derivative of the meridian curvature at points where the effect of the orientational ordering exactly counterbalances the effect of the isotropic bending. The system of Euler-Lagrange differential equations was solved numerically to yield consistently related equilibrium orientational distribution of the phospholipid molecules and vesicle shape. According to our estimation of the model constants the formation of the neck is promoted if direct interactions between the oriented molecules are taken into account. It was shown that the energy of the equilibrium shapes is considerably affected by the quadrupolar ordering of phospholipid molecules.     

模拟囊泡形变动力学的新方法离散空间变分法

提出了全新的离散空间变分法研究二维囊泡形变动力学过程，克服了原先解析或数值解囊泡形状方程遇到的困难，结果表明动力学终态与已有理论方法的计算结果完全一致；说明这一方法正确而且解法稳定有效，这一方法可进一步推广至研究三维无对称性的囊泡形状以及膜与膜之间有长程相互作用的情形，这为囊泡形状的研究提供了新的理论手段. 关键词： 离散空间变分法 囊泡 动力学 Helfrich方程     

Encapsulation and Releasing of Calcein by Spontaneously Formed Zwitterionic/Anionic Vesicle without Separation

The encapsulation and releasing of fluorescence dye calcein by spontaneously formed vesicle, from the mixtures of anionic surfactant (sodium dodecyl benzene sulfonate) and zwitterionic surfactant (Lauryl sulfonate betaine), was characterized with a simple but sensitive and accurate fluorescence method, using cobalt chloride as a quenching agent. Different from the separation method, the whole process proceeded in the same solution without removing the free calcein. After cobalt chloride quenching the outer calcein, the releasing of the calcein from the vesicle to bulk solution starts and finally reaches a steady value depending on the equilibrium between the osmotic pressure and resistance of membrane. The entrapment quantity of the SDBS/LSB vesicles to the calcein could then be deduced according to the difference of fluorescence intensity before and after the quenching, which varies with the mixing ratios of the two kinds of surfactants. The addition of additives such as salt and especially the polymer (polyvinylpyrrolidone) reduces the releasing velocity by strengthening the bilayers, and increases the encapsulation quantity, even 3times at the most.     

Unique incorporation behavior of amino acid-type surfactant into phospholipid vesicle membrane

The incorporation behavior of some anionic surfactants, including amino acid-type surfactants, on phospholipid vesicles was investigated. This was done by measuring the release of a vesicle-entrapped fluorescence probe and the scattered light intensities of vesicle particles in the surfactant solution as a function of surfactant concentration and time. Sodium dodecyl sulfate, sodium dodecanesulfonate, sodium dodecanoyl sarcosinate, and sodium dodecanoyl glutamate were employed in this study. All surfactants ruptured the phospholipid vesicle at around each critical micelle concentration by mixed micelle formation with phospholipid. While leakage of the fluorescence probe took place at a very low concentration in the sulfate- or sulfonate-type surfactant systems, it occurred at the concentration just below the CMC in the amino acid-type surfactant systems. Kinetic analysis of the release of the probe from the vesicles showed that the former surfactants adsorbed independently and homogeneously onto the phospholipid vesicles, while the latter surfactants were cooperatively incorporated.