多羧基小分子化合物诱导阳离子囊泡聚集的研究

研究了由阳离子型肽脂质溴化N,N-二-十六烷基-Na-6-三甲胺基己酰基-L-丙氨酰胺(N+C5Ala2C16)形成的阳离子囊泡,在加入含羧基小分子化合物后形成的聚集。考察了乙二胺四乙酸(EDTA)加入到囊泡中后吸光值随时间的变化。结果表明:当EDTA增加到一定浓度时可以引起由阳离子囊泡的聚集;在加入Ca2+后,阳离子囊泡聚集体得到分散;借助电子显微镜观察到了囊泡的聚集和分散。超滤后,用高效液相色谱法确定了囊泡结合的EDTA量。考察了不同pH条件下EDTA对囊泡聚集的影响,当EDTA等含多羧基小分子化合物羧基解离数为三个或以上时能够引起囊泡的聚集,而少于三个时囊泡不能发生聚集。     

温度调控表面活性剂溶液有序结构转变研究新进展

总结了近年来在温度调控表面活性剂有序结构转变研究方面的新进展. 主要介绍了囊泡的相转变, 温度诱导的胶束/囊泡转化, 离子表面活性剂胶束体系中的浊点现象, 温度控制的囊泡聚集以及温度诱导液晶相的形成与转化等五个方面的相关工作.     

稀土离子对肌醇磷脂囊泡的作用--结合、诱导聚集和促进水解

肌醇磷脂在细胞信号转导系统中起重要作用, 其水解反应是信号转导过程中的关键环节. 应用荧光淬灭滴定, 光散射以及高压液相技术, 研究了La3 和Tb3 对肌醇磷脂囊泡的作用, 包括结合常数的测定, 和对囊泡的诱导聚集作用以及促进肌醇磷脂水解的作用, 发现稀土离子与肌醇磷脂间具有较高的亲和力, 同时这种结合也诱导了肌醇磷脂囊泡的聚集和水解, 其程度与稀土离子和肌醇磷脂的结合常数有关.     

聚合诱导自组装制备多腔室囊泡以及成核链段中亲溶剂片段的影响

聚合物纳米材料的形貌对于其性能具有重要的影响, 其中囊泡(特别是多腔室囊泡)由于其具备空心结构备受关注. 聚合诱导自组装(PISA)是一种高效的制备聚合物纳米材料的方法. 然而, 目前利用PISA高效制备多腔室囊泡的报道则相对较少. 本工作中, 以聚乙二醇为大分子可逆加成-断裂链转移(RAFT)试剂(PEG₄₅-PETTC)调控苯乙烯(St)在混合溶剂乙醇/水(质量比7/3)中的RAFT聚合诱导自组装, 成功制备了多腔室囊泡. 同时开展了St和寡聚乙二醇甲醚甲基丙烯酸酯(OEGMA)的RAFT共聚合诱导自组装, 探索在成核链段中引入亲溶剂基元OEGMA对所得纳米材料形貌的影响. 由于聚苯乙烯的链刚性较强, 在聚苯乙烯链段中引入亲溶剂链段来增加成核链段的柔顺性是一种已报道的促进形貌转变的方法. 然而St和OEGMA在混合溶剂乙醇/水(质量比7/3)的聚合诱导自组装体系中, 发现亲溶剂基元(OEGMA)的引入, 导致所得纳米材料的形貌退化. 随着成核链段中亲溶剂基元的增加, 所得纳米材料逐渐由多腔室囊泡转变为单腔室囊泡和球形胶束.     

三维宏观网络状囊泡薄膜的分级自组装研究

分别合成以疏水性超支化聚醚(HBPO)为核,以亲水性聚环氧乙烷(EO)和聚甲基丙烯酸N,N-二甲氨基乙酯(DMAEMA)为臂的两亲性超支化多臂共聚物HBPO-star-PEO和HBPO-star-PDMAEMA.通过两者在水溶液中的复合自组装制备得到具有pH响应性的巨型聚合物囊泡(1~10μm),并用zeta电位仪,激光共聚焦显微镜及光学显微镜对囊泡的自组装行为进行了研究.结果表明,在等电点以前,复合囊泡始终以单个囊泡形式存在;随着溶液pH的升高,囊泡逐步线型缔合成串珠结构;在更高的pH下,囊泡进一步二次聚集形成具有宏观尺度的三维蜘蛛网状超分子结构,这是一类新的自组装体.     

中间嵌段为亲水性的BAB型三嵌段共聚物水溶液中初级聚集体的二次聚集行为研究

采用TEM和AFM研究了PS(聚苯乙烯)₄₃-b-PEO(聚氧乙烯)₄₅-b-PS₄₃和PS₃₉-b-P4VP(聚4-乙烯基吡啶)₉₈-b-PS₃₉三嵌段共聚物在水介质中的球形胶束、囊泡和蠕虫状胶束之间的二次聚集行为.实验发现,初级聚集体的二次聚集具有不同的复杂程度.对称性的初级聚集体,如球形胶束和囊泡,其二次聚集表现出球形对称性;而非对称性初级聚集体(如蠕虫状胶束)二次聚集开始倾向于非对称性.BAB型的嵌段设计有利于初级聚集体的二次聚集发生.     

生物医用高分子囊泡

高分子囊泡由于其独特的腔-膜-冠结构,在生物医用等领域具有重要应用前景.本专论从自组装新机理/新方法和新的生物医学应用两方面总结和评述了近期生物医用高分子囊泡领域的研究进展.前者包括构建高效包载生物大分子的囊泡的“酸诱导吸附”和“亲和强化吸引”原理、构建完全非对称冠囊泡的“胶束-囊泡转变法”、构建高级囊泡结构的“融合诱导粒子自组装”方法、可宏量制备囊泡的氨基酸环内酸酐开环聚合诱导自组装方法;后者主要介绍“以糖控糖”囊泡、治疗糖尿病溃疡囊泡、抗菌囊泡、抗癌囊泡、靶向治疗骨质疏松症囊泡和护肾血管造影囊泡.最后,对高分子囊泡的未来发展方向进行了展望.     

油酸囊泡层状液晶作为模板电化学合成银纳米颗粒

在油酸囊泡的层状液晶中利用电化学沉积法成功地制备了银纳米颗粒。并用扫描隧道显微镜(STM)和透射电子显微镜(TEM)对银纳米颗粒进行了表征，发现银纳米颗粒能够均匀地分散在油酸囊泡中，并且油酸囊泡能够有效地阻止产生的银纳米颗粒发生聚集反应。此外，我们还提出了银纳米颗粒形成的机理。     

类水滑石诱导囊泡的自发形成

报道了一种新的囊泡合成方法——荷电固体纳米颗粒诱导囊泡的自发形成. 研究发现, 将5.0 g/L带结构正电荷的Mg₃Al类水滑石(HTlc)溶胶和0.02 mol/L由两性表面活性剂十二烷基甜菜碱(C₁₂BE)和阴离子表面活性剂双(2-乙基己基)琥珀酸磺酸钠(AOT)组成的溶液(C₁₂BE与AOT物质的量比为3∶2)混合, 当HTlc溶胶与表面活性剂溶液的体积比在1∶9～4∶6范围内, 在HTlc纳米颗粒的诱导下可自发形成囊泡, 并获得稳定的HTlc-囊泡复合分散体系.     

CTAB/SDBS囊泡的自发形成与聚合

讨论了CTAB/SDBS复配比例、体系浓度对其囊泡自发形成的影响和不同制备方法与放置时间对囊泡尺寸的影响,同时用TEM考察了囊泡的结构与形态。通过TEM发现囊泡之间有相互聚集融合变大的趋势,粒径分析也发现随放置时间延长囊泡尺寸增大。所以这里采用聚合法来改善囊泡的稳定性。经粒径分析证实经聚合法处理的囊泡其尺寸明显比未处理的稳定。     

Temperature-controlled vesicle aggregation in the mixed system of sodium n-dodecyl sulfate/n-dodecyltributylammonium bromide

Temperature-controlled vesicle aggregation was investigated in a catanionic surfactant system of sodium n-dodecyl sulfate/n-dodecyltributylammonium bromide. Vesicle aggregation took place as the temperature reached the critical value (Tc). Tc can be adjusted by the variations of the total surfactant concentration and the mixed molar ratio. It was also found that the temperature variation above Tc can greatly influence the vesicle aggregation rate. The vesicle aggregation process was irreversible as long as T >/= Tc, whereas the vesicle disaggregation process occurred only below Tc.     

Aggregation Behavior of Nonionic Clycolipid Vesicles in Acidic Region

Large unilamellar vesicles composed of a nonionic synthetic glycotipid, 1,3 - di- 0 - phylanyl -2-0-(β- maltotriosyl ) glycerol show pH-dependent aggregation - dissocialion process, that is, vesicle aggregation occurs in the lower pH region and vesicle dissociation occurs in the higher pH region. This process is almost reversible and the aggregation threshold pH is dependent on NaCl concentration. Fluorescence technique has been applied to study whether the vesicle fusion occurs or not during the aggregation-dissociation process. It is concluded pH can only induce the aggregation of this nonionic glycoltpid vesicle.     

Vesicle aggregation in aqueous mixtures of negatively charged polyelectrolyte and conventional cationic surfactant

Vesicle aggregation induced by different environmental factors, including the addition of divalent metal ions, decrease of pH, and increase of temperature--was investigated through turbidity measurement, fluorescence measurement, and transmission electron microscope observation in aqueous solutions of hydrolyzed styrene-maleic anhydride copolymer (HSMA) mixed with dodecyltriethylammonium bromide (C(12)Et(3)). The vesicle aggregation can be explained by the dehydration of the vesicle surface through cations addition or temperature increase based on an analysis of the interaction between vesicles. Moreover, the steric repulsion was introduced to the system and the control of vesicle aggregation was achieved.     

Construction of macroscopic cytomimetic vesicle aggregates based on click chemistry: controllable vesicle fusion and phase separation

Vesicle-vesicle aggregation to mimic cell-cell aggregation has attracted much attention. Here, hyperbranched polymer vesicles (branched-polymersomes, BPs) with a cell-like size were selected as model membranes, and the vesicle aggregation process, triggered by click chemistry of the copper-catalysed azide-alkyne cycloaddition reaction, was systematically studied. For this purpose, azide and alkynyl groups were loaded on the membranes of BPs through the co-assembly method to obtain N(3)-BPs and Alk-BPs, respectively. Subsequently, macroscopic vesicle aggregates were obtained when these two kinds of functional BPs were mixed together with the ratio of azide to alkynyl groups of about 1:1. Both the vesicle fusion events and lateral phase separation on the vesicle membrane occurred during such a vesicle aggregation process, and the fusion rate and phase-separation degree could be controlled by adjusting the clickable group content. The vesicle aggregation process with N(3) -micelles as desmosome mimics to connect with Alk-BPs through click-chemistry reaction was also studied, and large-scale vesicle aggregates without vesicle fusion were obtained in this process. The present work has extended the controllable cytomimetic vesicle aggregation process with the use of covalent bonds, instead of noncovalent bonds, as the driving force.     

Directed aggregation and fusion of lipid vesicles induced by DNA-surfactants

We investigated DNA-directed aggregation of vesicles using DNA-surfactants. Following tethering of single-stranded DNA oligonucleotides to vesicles using DNA-surfactant, the tethered vesicles were assembled with other vesicles bearing complementary strands. The vesicle aggregation was strongly affected by the salt concentration and by temperature according to the characteristics of DNA hybridization. Restriction enzyme, which can hydrolyze the double-stranded DNA used in the present study, dissociated the vesicle aggregates. Exploration using fluorescently labeled vesicles suggested that the DNA-directed vesicle aggregation took place in a sequence-specific manner through DNA-duplex formation. Interestingly, the DNA-directed aggregation using short DNA-surfactant induced the fusion of vesicles to produce giant vesicles, resulting in an enzymatic reaction in the giant vesicle.     

双分子膜上染料的吸附性质及对膜结构的影响

系统地研究了染料甲基橙和达旦黄在含席夫碱基囊泡双分子膜阳离子表面上的吸附和聚集，以及由此产生的对膜聚集结构的影响，染料的吸附和聚集可经电子吸收光谱的因吸附产生的沉淀证实，并且ＭＯ的聚集结构的Ｈ－聚集，ＴＹ的聚集结构为Ｊ－聚集。改变ｐＨ的研究表明ＭＯ在变色ｐＨ值以及因形成阳离子而解聚，ＴＹ在酸性条件下亦因离子化程度减弱和部分质子化而使聚集被削弱，但在碱性条件下其聚集产生更大的红移。温度变化的结果显示     

Interaction and aggregation of lipid vesicles (DLVO theory versus modified DLVO theory)

Interaction and aggregation of acidic phospholipid (phosphatidylserine) vesicles were studied with variation of cation species and their concentrations in vesicle suspensions, and of vesicle sizes. Aggregation was determined by measuring turbidity of vesicle suspension. The experimental results of aggregation of vesicles induced by monovalent cations (Na⁺, K⁺, Cs⁺ and TMA⁺) were explained well in terms of the interaction energy of two interacting vesicles using the ordinary Derjaguin–Landau–Verwey–Overbeek (DLVO) theory for both small and large lipid vesicles. However, the experimental results of aggregation of vesicles induced by divalent cations (Ca²⁺, Mg²⁺ and Ba²⁺) were not explained by the ordinary DLVO theory. In order to explain the experimental results of these vesicle aggregation phenomena, it was necessary to modify the theory by including hydration interaction energies which are due to hydrated water at membrane surfaces, and their magnitude and sign depend upon the nature (hydrophobicity) of the membrane surface.     

Interglycolipid Membrane Interactions: pH-Dependent Aggregation of Nonionic Synthetic Glycolipid Vesicles

Large unilamellar vesicles composed of a nonionic synthetic glycolipid, 1,3-di-O-phytanyl-2-O-(beta-D-maltotriosyl)glycerol exhibited a pH-dependent aggregation-disaggregation process; vesicle aggregation occurred in a lower pH region and vesicle disaggregation occurred in a higher pH region. This process was almost reversible and the aggregation threshold pH increased as NaCl concentration increased. Electrophoretic mobility measurements revealed that the glycolipid vesicles are negatively charged in the range pH 1.6-13. The change in zeta-potentials as functions of pH and NaCl concentration could be well described by the Gouy-Chapman expression of the surface charges with an assumption that the interfacial charges arise from the "adsorption" of OH(-) at the vesicle-water interface and the dissociation of hydroxyl groups of the sugar headgroup in a higher pH regime (>pH 10). The pH-dependent aggregation process was reasonably well described by the classical DLVO theory. Thus, the double-layer repulsive forces appear to be a major factor in stabilizing the glycolipid vesicle suspension. Copyright 2000 Academic Press.     

动、静态光散射在线跟踪DPPC/PA脂质体的聚集和融合过程

结合动、静激光光散射在线跟踪了经低温培养的二棕榈酰基磷脂酰胆碱/棕榈酸(摩尔比为1:2)脂质体在25-41℃温度范围内的聚集和融合过程.在升温过程中,脂质体的尺寸和相对分子质量明显增大,表明有聚集或融合发生.另外,尺寸分布出现角度依赖性,证明囊泡结构遭到破坏.而在接下来的降温过程中,粒径和相对分子质量继续增大,没有回到初始状态.根据光散射结果,我们认为脂质体富集脂肪酸分子的区域随温度升高会发生黏合而形成聚集,该聚集体形态类似反六方柱状相.融合发生的比例较小.降温过程中的变化表明囊泡是动力学稳定态,一旦聚集发生,会自发继续进行聚集或融合.