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。     

聚硼酸酯表面活性剂囊泡自发形成

通过直接引发聚合, 以偶氮二异丁腈为引发剂, 用N-羟甲基丙烯酰胺、硼酸三乙酯和N,N-二羟乙基十二烷基胺制备了聚硼酸酯(PMBE)表面活性剂, 用红外光谱、核磁共振谱和凝胶色谱对其结构进行了表征; 用透射电镜(TEM)研究了PMBE在纯水和0.1 mol/L NaCl水溶液中的自组装形态. 结果表明, PMBE在水和0.1 mol/L NaCl溶液中皆可自发形成聚合囊泡; 在水溶液中PMBE囊泡粒径约为20 nm, 而NaCl溶液中囊泡直径增大, 在150~250 nm之间, 分布较为均匀; 结合两亲性分子排列参数理论和一定的近似处理方法对PMBE聚合囊泡的形成机理进行了初步探讨.     

盐引发阴离子/非离子表面活性剂复配体系中囊泡自发形成

在无盐时, 阴离子表面活性剂十二烷基苯磺酸钠(SDBS)与非离子表面活性剂壬基酚聚氧乙烯(10)醚(TX-100)的复配体系中只有混合胶束存在, 而盐的加入即可以引发体系中囊泡的自发形成, 这使得囊泡的形成变得更加简单. 引发机理可以归因于盐对离子表面活性剂的极性头双电层的压缩作用, 减少了极性头的面积, 加上非离子表面活性剂的参与使得堆积参数P增加, 导致了半径更大的聚集体的形成. 制作了SDBS/TX-100/盐水拟三元相图, 通过目测和表面张力的变化确定了囊泡形成的带状区域, 并用负染色电镜(TEM)对囊泡进行了表征, 同时测定了盐度以及相同盐度下表面活性剂浓度对囊泡粒径的影响, 发现囊泡的粒径随着盐度的增加而增加, 而在同一盐度下, 囊泡的粒径基本不受表面活性剂浓度的影响.     

石英纳米通道单磷脂囊泡的电阻-脉冲分析方法（英文）

本文报告了用于检测单囊泡及其粒径分析的石英纳米通道电阻-脉冲分析方法.采用圆柱形石英纳米通道可检测粒径为100~300 nm的单磷脂囊泡和直径为170~400 nm的聚苯乙烯纳米颗粒.单囊泡和纳米颗粒的迁移可通过检测各自产生的方波电流脉冲信号,并由此确定颗粒尺寸.结果表明,采用石英纳米通道电阻-脉冲分析方法得到的颗粒/囊泡粒径与采用动态光散射法和扫描电子显微法得到的结果完全一致.这种基于电子的分析方法具有快速简单的特点,所用的自制微传感器廉价耐用.石英通道的应用还可与其它分析方法如电流分析法和荧光显微法联用,以获得生物囊泡及人工囊泡更完全的信息.     

石英纳米通道单磷脂囊泡的电阻-脉冲分析方法

本文报告了用于检测单囊泡及其粒径分析的石英纳米通道电阻-脉冲分析方法. 采用圆柱形石英纳米通道可检测粒径为100~300 nm的单磷脂囊泡和直径为170~400 nm的聚苯乙烯纳米颗粒. 单囊泡和纳米颗粒的迁移可通过检测各自产生的方波电流脉冲信号, 并由此确定颗粒尺寸. 结果表明,采用石英纳米通道电阻-脉冲分析方法得到的颗粒/囊泡粒径与采用动态光散射法和扫描电子显微法得到的结果完全一致. 这种基于电子的分析方法具有快速简单的特点,所用的自制微传感器廉价耐用. 石英通道的应用还可与其它分析方法如电流分析法和荧光显微法联用,以获得生物囊泡及人工囊泡更完全的信息.     

两亲性聚氨基酸三嵌段共聚物构筑pH/溶剂可控多级纳米结构

通过开环聚合（ROP）和原子转移自由基聚合（ATRP）合成了一种pH响应性三嵌段共聚物聚乙二醇-b-聚赖氨酸-b-聚苯乙烯（PEG-b-PLL-b-PS），在水-有机溶剂混合溶液中进行组装，并采用透射电子显微镜（TEM）、原子力显微镜（AFM）和衰减全反射红外光谱法（ATR-IR）表征.该三嵌段共聚物在四氢呋喃（THF）与水的混合溶剂（V：V=1：1）中可组装成疏水性聚苯乙烯为核、亲水性聚赖氨酸和聚乙二醇分别为内壳和外壳的球状胶束.采用TEM和AFM发现该球状胶束在四氢呋喃（THF）水溶液中退火7 d后可进一步转变为纤维状结构.进一步除去THF后，可恢复至粒径略小的冻结球状胶束.另外，球状胶束的粒径随着pH的增加而增加，当pH为13时，聚赖氨酸的二级结构由无规卷曲构象过渡到α-螺旋构象，聚集体由球形结构过渡到空心囊泡.溶液经透析后可使囊泡恢复至球状胶束.     

赖氨酸在甘草次酸弹性囊泡形成过程中的作用机制

制备和评价含赖氨酸的甘草次酸弹性囊泡, 并考察赖氨酸在囊泡形成过程中的作用机制. 在水合介质中加入赖氨酸, 利用薄膜-高压均质法制备甘草次酸弹性囊泡. 并合成了甘草次酸赖氨酸盐及其弹性囊泡作为对比制剂. 通过对粒径、zeta电位、包封率、相转变温度、变形性和体外经皮渗透性的测试, 考察赖氨酸在甘草次酸弹性囊泡中的存在形式及作用. 结果显示加入赖氨酸后, 甘草次酸弹性囊泡的粒径略有降低, 膜相转变温度降低, 包封率和囊泡变形性显著提高, 载药量提高近30倍(1.5 mg·mL-1), 并显著高于其赖氨酸盐所形成囊泡的载药量和弹性. 此外, 赖氨酸的加入使弹性囊泡的变形能力增加, 8 h累积透过量和皮肤驻留量分别提高4.3倍和9.2倍. 表明赖氨酸与甘草次酸形成离子缔合物, 促进甘草次酸参与膜的形成, 使膜的流动性增加, 赖氨酸与弹性囊泡对提高囊泡载药量起协同作用.     

盐浓度及磷脂分子结构对多组分带电膜弯曲刚性的影响

磷脂膜弯曲刚性模量很难直接测量, 本实验用循环冻融法制备尺寸大小与膜弯曲刚性相关的熵稳定单层囊泡. 粒度仪测量发现, 囊泡尺寸随盐浓度增加呈现先剧烈减小然后缓慢增加的分段变化规律. 但当组分中含有头部带电同时尾链带有不饱和键的二油酰磷脂酰甘油酯时, 囊泡尺寸却在较大的盐浓度范围内不出现回升. 囊泡膜的负Zeta-电势绝对值均表现为先急剧减小然后趋于平稳的变化规律, 数值大小只与带电组分的含量有关. 而对直接水合法制备的多层囊泡的统计发现, 囊泡尺寸随盐浓度增加急剧减小, 随后趋于稳定值, 均不随分子组合变化而回升. 结果表明在不同的盐浓度范围里, 主导磷脂膜弯曲刚性模量的因素不同. 低盐浓度的体系, 静电屏蔽效应为主导因素; 高盐浓度的体系, 膜双电层中反离子的分布起主导作用. 磷脂分子头部与尾部的不同结构组合会影响膜双电层, 使膜的弯曲刚性不同. 多层囊泡体系中, 高盐浓度下膜的热涨落掩盖了分子结构及双电层分布差异对膜弯曲刚性的影响.     

基于多肽和温敏聚合物的光交联囊泡的制备及表征（英文）

解决聚合物囊泡降解性和稳定性的矛盾是一个重要问题。本文通过可逆加成断裂链转移(RAFT)聚合和开环聚合(ROP)合成了一种聚[(N-异丙基丙烯酰胺-无规-7-(2-甲基丙烯酰氧基乙氧基)-4-甲基香豆素)-嵌段-(L-谷氨酸)][P(NIPAM_(45)-stat-CMA_5)-b-PGA_(42)]的两亲嵌段共聚物。囊泡膜由温敏性的聚N-异丙基丙烯酰胺(PNIPAM)和可光交联聚7-(2-甲基丙烯酰氧基乙氧基)-4-甲基香豆素(PCMA)组成。由囊泡膜向内外舒展的聚谷氨酸(PGA)链使囊泡稳定分散在水中,并且可进一步官能化。透射电子显微镜(TEM)和动态光散射(DLS)表征证实了囊泡的形貌和尺寸分布。本研究为制备基于多肽共聚物的可降解温敏囊泡提供了一个范例,并有望在纳米生物医药领域得到应用。     

剪切流场对ABA三嵌段共聚物囊泡形貌的影响

通过同轴圆筒剪切仪和磁子搅拌方式提供的剪切流场,研究了均匀和非均匀流场对ABA两亲性三嵌段共聚物囊泡的影响.研究发现,非均匀流场下囊泡尺寸及其分散度随剪切速率的增加呈现先增大后减小的规律.与搅拌形成的非均匀流场相比,在同轴剪切仪提供的均匀流场下形成的囊泡尺寸更加均匀.结果表明,剪切流场是影响囊泡形貌的重要因素,流场的不均匀性是导致组装体形貌结构多分散性的重要原因之一.     

New progesterone esters as 5alpha-reductase inhibitors

The pharmacological activity of four new progesterone derivatives: 4-bromo-17alpha-(p-fluorobenzoyloxy)-4-pregnene-3,20-dione (7), 4-bromo-17alpha-(p-bromobenzoyloxy)-4-pregnene-3,20-dione (8), 4-bromo-17alpha-(p-chlorobenzoyloxy)-pregnene-3,20-dione (9) and 4-bromo-17alpha-(p-toluoyloxy)-4-pregnene-3,20-dione (10) was determined. These compounds were evaluated as 5alpha-reductase inhibitors on gonadectomized hamster seminal vesicles and flank organs. The pharmacological data of this study indicate that compounds 7 and 9 having at C-17 p-fluorobenzoyloxy and p-chlorobenzoyloxy ester functions respectively showed the highest antiandrogenic effect as measured by the reduction of the weight of the seminal vesicles. In the flank organ model, the same compounds 7 and 9 exhibited a smaller diameter, 1.8 and 1.0 mm, respectively, than the commercially available finasteride 3 (2.3 mm), thus indicating a higher inhibitory effect on 5alpha-reductase enzyme. Steroid 7 showed a higher inhibitory activity on the conversion of T to DHT (Fig. 3) than the presently used finasteride, thus indicating a higher antiandrogenic effect. The nonsubstituted benzoyloxy ester (compound 15) showed a lower antiandrogenic activity as measured in the seminal vesicles model than the p-substituted benzoyloxy compounds.     

Application of mean field boundary potentials in simulations of lipid vesicles

A method is presented to enhance the efficiency of simulations of lipid vesicles. The method increases computational speed by eliminating water molecules that either surround the vesicle or reside in the interior of the vesicle, without altering the properties of the water at the membrane interface. Specifically, mean field force approximation (MFFA) boundary potentials are used to replace both the internal and external excess bulk solvent. In addition to reducing the cost of simulating preformed vesicles, the molding effect of the boundary potentials also enhances the formation and equilibration of vesicles from random solutions of lipid in water. Vesicles with diameters in the range from 20 to 60 nm were obtained on a nanosecond time scale, without any noticeable effect of the boundary potentials on their structure.     

Effect of poly(acrylic acid) block length distribution on polystyrene-b-poly(acrylic acid) block copolymer aggregates in solution. 2. A partial phase diagram

The first paper of the series, which focused on the effect of polydispersity on the self-assembly of block copolymer vesicles, showed that an increase in the width of the poly(acrylic acid) (PAA) block length distribution resulted in a decrease in the size of the vesicles formed. In this paper, the rest of the phase diagram is explored. For the present study, a series of polystyrene-b-poly(acrylic acid) copolymers of an identical polystyrene length of 325 units but of varying degrees of polymerization of PAA was synthesized. Mixtures of the copolymers were made to artificially broaden the molecular weight distribution of PAA at a constant number average of 48 in the polydispersity index (PDI) range of 1.1-3.3. The mixtures were dissolved in dioxane, and water was added slowly to predetermined amounts. Transmission electron microscopy was used to observe aggregate morphologies at different water contents and PAA PDIs. At low water contents, dynamic light scattering was also used to measure the sizes of the aggregates. A partial phase diagram as a function of the water content and PAA PDI was obtained. Large compound micelles and spherical micelles (average diameter of 40 nm) were found at low water contents; however, at a water content of 12% (w/w), a continuum of morphologies from spheres to rods to vesicles was found with increasing PAA PDI. In addition, each copolymer was investigated by itself under identical conditions to those used for the mixtures to determine if there was any segregation of the individual polymers into separate aggregates. No evidence for such segregation was found.     

Effect of block length, polydispersity, and salt concentration on PEO-PDEAMA block copolymer structures in dilute solution

A series of poly(ethylene oxide)-block-poly(N,N-diethylaminoethyl methacrylate) (PEO-PDEAMA) block copolymers with relatively high polydispersity (1.36 < PDI < 1.96) have been prepared to determine the effect that polydispersity has on the self-assembly of amphiphilic block copolymers in dilute solution. Because monodisperse macroinitiators were used for the ATRP reactions, the polydispersity resides within the hydrophobic block. By adjusting the relative block lengths, spherical micelles, wormlike micelles, vesicles, or a precipitate is formed. Here, we show that relatively high polydispersity in the block copolymer does not preclude efficient self-assembly. We also discuss the effect of increasing the concentration of NaCl in the systems and show that this can result in a shift from one morphology to another. These shifts are reversible in some cases, but for PEO12-PDEAMA39, this method allows access to giant vesicles of between 500 nm and 1 microm in diameter.     

Self-assembly and morphology control of new L-glutamic acid-based amphiphilic random copolymers: giant vesicles, vesicles, spheres, and honeycomb film

New amphiphilic random copolymers containing hydrophobic dodecyl (C12) chain and hydrophilic L-glutamic acid were synthesized, and their self-assembly in solution as well as on the solid surfaces was investigated. The self-assembly behavior of these polymers are largely dependent on their hydrophilic and hydrophobic balances. The copolymer with a more hydrophobic alkyl chain (～90%) self-assembled into giant vesicles with a diameter of several micrometers in a mixed solvent of ethanol and water. When the hydrophobic ratio decreased to ca. 76%, the polymer self-assembled into conventional vesicles with several hundred nanometers. The giant vesicles could be fused in certain conditions, while the conventional vesicles were stable. When the content of the hydrophilic part was further increased, no organized structures were formed. On the other hand, when the copolymer solutions were directly cast on solid substrates such as silicon plates, films with organized nanostructures could also be obtained, the morphology of which depended on solvent selection. When ethanol or methanol was used, spheres were obtained. When dichloromethane was used as the solvent, honeycomb-like morphologies were obtained. These results showed that through appropriate molecular design, random copolymer could self-assemble into various organized structures, which could be regulated through the hydrophobic/hydrophilic balance and the solvents.     

Effective form of sulfoquinovosyldiacyglycerol (SQDG) vesicles for DNA polymerase inhibition

Sulfoquinovosyldiacyglycerol (SQDG) has a wide range of biological activities that make it an attractive compound for the development of new drugs. Chemically synthesized beta-SQDG-C(18:0) (1,2-di-O-stearoyl-3-O-(6-deoxy-6-sulfo-beta-d-glucopyranosyl)-sn-glycerol), for example, has a potent inhibitory effect on DNA polymerases. We investigated the properties of the vesicle form of beta-SQDG-C(18:0) as the monomer has low solubility in water. The structure of the beta-SQDG-C(18:0) vesicles are highly influenced by NaCl concentration in preparation process. At low NaCl concentrations, the beta-SQDG-C(18:0) vesicles have high surface curvature and form small unilamellar vesicles. Increases in NaCl concentration, resulted in decreased surface curvature and a tendency for beta-SQDG-C(18:0) to form large multilamellar vesicles. The small unilamellar vesicles showed a potent inhibitory effect on DNA polymerase beta, whereas the large multilamellar vesicles had no such effect. We investigated further the relationship between vesicle size and activity by preparing smaller vesicles (262, 99 and 43 nm in diameter) using an extrusion technique. These smaller vesicles had a greater inhibitory effect on DNA polymerase beta activity than non-extruded vesicles. beta-SQDG-C(18:0) vesicles, especially those of small size, were effective in DNA polymerase inhibition and are expected to have high applicability in DNA polymerase study.     

Giant vesicles formed by gentle hydration and electroformation: a comparison by fluorescence microscopy

Giant unilamellar vesicles (diameter of a few tens of micrometers) are commonly produced by hydration of a dried lipidic film. After addition of the aqueous solution, two major protocols are used: (i) the gentle hydration method where the vesicles spontaneously form and (ii) the electroformation method where an ac electric field is applied. Electroformation is known to improve the rate of unilamellarity of the vesicles though it imposes more restricting conditions for the lipidic composition of the vesicles. Here we further characterize these methods by using fluorescence microscopy. It enables not only a sensitive detection of the defects but also an evaluation of the quantity of lipids in these defects. A classification of the defects is proposed and statistics of their relative importance in regard to both methods and lipid composition are presented: it shows for example that 80% of the vesicles obtained by electroformation from 98% 1,2-dioleoyl-sn-glycero-3-phosphocholine are devoid of significant defects against only 40% of the vesicles with the gentle hydration method. It is also shown that the presence of too many negatively charged lipids does not favor the formation of unilamellar vesicles with both methods. For the gentle hydration, we checked if the negatively charged lipids were inserted in the vesicles membrane in the same proportion as that of the lipid mixture from which they are formed. The constant incorporation of a negatively charged labeled lipid despite an increasing presence of negatively charged 1,2-dioleoyl-sn-glycero-3-[phospho-l-serine] tends to confirm that the composition of vesicles is indeed close to that of the initial mixture.     

两亲性线性-超支化多臂共聚物在水溶液中自组装为阳离子囊泡的研究

利用两亲性线性-超支化多臂共聚物聚乙二醇-聚乙烯亚胺-聚谷氨酸苄酯(PEG-PEI-PBLG)在水溶液中自组装为阳离子囊泡. 利用透射电镜、动态光散射、静态光散射和zeta电位仪对囊泡结构进行了表征. PEG-PEI-PBLG囊泡具有双分子层结构, 壁厚5~10 nm, 直径在100 nm左右. 由于PEI在水溶液中的质子化作用, 囊泡表面携带有正电荷, 其表面电势为＋25。2 mV, 因此PEG-PEI-PBLG阳离子囊泡具有担载负电性蛋白的能力.