Photochromism of spirobenzopyran in the membrane of surfactant vesicle and in the cavity of cyclodextrins

Photochromic reaction of water insoluble 1,3,3-trimethyl-6-nitrospiro[2H-1-benzopyran-2,2-indoline] (SP) was studied in water with the aid of vesicles and -cyclodextrin (-CD). In both systems, the photochromic reaction of SP was observable in spite of the low solubility of SP in water. In order to examine the microenvironment around the SP and the reaction product, photomerocyanin (MC), in those systems, the spectrum of MC was measured in various organic solvent of various polarity. Decreasing the polarity of the solvent decreased the peak absorbance and shifted the peak wavelength to the long wavelengths. When the vesicles were used, the reactant, SP, and the product, MC, were solubilized in different regions of different polarity. The reaction substrate was then supposed to have moved from the hydrophobic region of the membrane to the hydrophilic one after the photoisomerzation. The photochromic reaction of SP in the presence of -CD was slower than in the vesicles and faster than that in methanol. The polarity in the vesicular membrane and the limited rotation of the reactant in the cavity of -CD may have influenced the reaction rate. The prolonged light irradiation period resulted in a simultaneous photoreaction and polymerization, producing some unknown side reaction.     

可控组装方法制备脂质体

利用可控组装方法制备了单仓脂质体。这种制备方法分为两个步骤: (a)利用超声振荡形成油包水(W/O)的微乳液, (b)微乳中小水滴在离心作用下通过油水界面的单分子膜并被其包裹, 在水相中形成脂质体。脂质体直径在50-200nm。脂质体的双分子膜间基本没有残留有机溶剂存在, 并且在制备过程中包封的试剂没有泄漏。可控组装方法制备脂质体具有操作简单、生成脂质体一般不需进一步分离、包封效率较高(57%)等特点。     

Phase evolution,structural characteristics and mechanism of vesicle formation from a synthetic amphiphile: Controlled morphology by tuning solution phase parameters

We report herein, the aggregation behavior of 3, 4-di(dodecyloxy)benzoic acid-4-hydroxy phenyl ester (DDBE), a synthetic amphiphile and a true non-ionic surfactant system as per the geometrical considerations. The true surfactant nature of the system stems from its hydrophilic-lipophilic-balance (HLB?=?4.7), comparable to that of Span-60, also a true non-ionic surfactant. This compound undergoes spontaneous vesicle formation in THF:water binary solvent mixtures which further underwent fission at lower DDBE concentrations and fusion at higher concentrations, leading to giant vesicles of the order of 3000?nm. These vesicles are sensitive to the polarity of their environment. The predominant mode of interaction as observed from the molecular dynamics simulations were found to be π-π stacking with the phenyl rings of the molecule. Further, the system, upon complete extraction into water, formed spherical aggregates of size 50?nm based on the good solvent-poor solvent combination as the necessary condition for the vesicle formation.GRAPHICAL ABSTRACT     

正负离子表面活性剂混合体系中高稳定性囊泡的形成

对总浓度为0.01 mol/L，摩尔比为2：1的十二烷基硫酸钠/溴化十二烷基三乙 铵的正负离子表面活性剂混合体系形成的囊泡的稳定性进行了研究。发现这一体系 形成的囊泡在长放置（5个月）后依然存在。在加入较大量的无机盐（0.15 mol/L NaBr）、较大幅度pH变化（pH = 2～12）、温度变化（从80 ℃到-22 ℃）情况下 体系中的囊泡依然呈现出优异的稳定性。在非水溶剂乙醇（100%）中这类正负离子 表面活性剂仍然可以形成囊泡。     

Formation and coexistence of the micelles and vesicles in mixed solution of cationic and anionic surfactant

In the aqueous mixtures of sodium alkylcarboxylate and alkyltrimethylammonium bromide, large unilamelar vesicles can be formed spontaneously or by sonication as the total carbon number in the HC chains is 19 (or larger). Vesicle formation can be influenced by changes of pH, molar ratio of the two surfactant components, and the polar head group of cationic surfactant. Micelles may coexist with the vesicles in these mixed systems. The larger hydrodynamic radius (200 nm) and aggregation number (800) illustrate that the shape of the micelle in 1:1 C₉H₁₉COONa–C₁₀H₂₁N(CH₃)₃Br is rod-like. In some mixed systems, the micelles can be transformed into stable vesicles by sonication — a phenomenon revealed for the first time. The surface-chemical properties of these catanionic surfactant solutions and the stabilities of vesicle have been studied systematically.     

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.     

Electroformation in a flow chamber with solution exchange as a means of preparation of flaccid giant vesicles

A recently described technique [Estes and Mayer, Biochim. Biophys. Acta 1712 (2005) 152-160] for the preparation of giant unilamellar vesicles (GUVs) in solutions with high ionic strength is examined. By observing a series of osmotic swellings followed by vesicle bursts upon a micropipette transfer of a single POPC GUV from a sucrose solution into an iso-osmolar glycerol solution, a value for the permeability of POPC membrane for glycerol, P=(2.09+/-0.82) x 10(-8)m/s, has been obtained. Based on this result, an alternative mechanism is proposed for the observed exchange of vesicle interior. With modifications, the method of Estes and Mayer is then applied to preparation of flaccid GUVs.     

光交联固化的聚合物囊泡用于降温触发的药物释放

The stability of nanocarriers in physiological environments is of importance for biomedical applications. Among the existing crosslinking approaches for enhancing the structural integrity and stability, photocrosslinking has been considered to be an ideal crosslinking chemistry, as it is non-toxic and cost-effective, and does not require an additional crosslinker or generate by-products. Meanwhile, most current temperature-responsive nanocarriers are designed and synthesized for drug release by increasing temperature. However, heating may induce cell damage during triggered drug release. Therefore, lowering temperature-triggered nanocarriers need to be developed for drug delivery and safe drug release during therapeutic hypothermia. In this study, we prepared an amphiphilic block copolymer, poly(ethylene oxide)-block-poly[N-isopropyl acrylamide-stat-7-(2-methacryloyloxyethoxy)-4-methylcoumarin]-block-poly(acrylic acid) [PEO₄₃-b-P(NIPAM₇₁-stat-CMA₈)-b-PAA₁₃], by reversible addition fragmentation chain transfer (RAFT) polymerization. Successful synthesis of the polymer was verified by proton nuclear magnetic resonance (¹H NMR) and size exclusion chromatography (SEC). The copolymers self-assembled into vesicles in aqueous solution, with the P(NIPAM-stat-CMA) block forming an inhomogeneous membrane and the PEO chains and PAA chains forming mixed coronas. The cavity of this vesicle could be utilized to load hydrophilic drugs. The CMA groups could undergo photocrosslinking and enhance the stability of vesicles in biological applications, and the PNIPAM moiety endowed the vesicle with temperature-responsive properties. Upon decreasing the temperature, the vesicles swelled and released the loaded drugs. The size distribution and morphology of the vesicles were characterized by dynamic light scattering (DLS), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) experiments. After staining with phosphotungstic acid, the hollow morphology of the vesicles with a phase-separated inhomogeneous membrane was observed by TEM and SEM. The DLS results showed that the hydrodynamic diameter of the vesicles was 208 nm and the polydispersity was 0.075. The size of the vesicles observed by TEM was between 180 and 200 nm, which was in accordance with that measured by DLS. To verify the drug loading capacity and controlled release ability of the vesicle, a water-soluble antibiotic was encapsulated in the vesicles. The experimental results showed that the drug loading content was 10.4% relative to the vesicles and the drug loading efficiency was approximately 32.7%. For vesicles containing the same amount of antibiotics, the release rate at 25 ℃ was 35% higher than that at 37 ℃ after 12 h in aqueous solution. Overall, this photocrosslinked vesicle with temperature-responsive properties facilitates lowering temperature-triggered drug release during therapeutic hypothermia.     

Synthesis and characterization of PISOZ-PDMS-PISOZ triblock polymer vesicles

In this project, we synthesized poly(2-isopropyl-2-oxazoline)-block- poly(dimethyl-siloxane)-block-poly(2-isopropyl-2-oxazoline) (PISOZ-PDMS-PISOZ) triblock polymer, which has been prepared as vesicles. The triblock polymer was characterized by ¹H-NMR, F-NMR, LS and TEM. The size of the empty vesicle is about 60 nm. When curcumin was encapsulated into PISOZ-PDMS-PISOZ triblock polymer, formed well defined vesicles in a size about 70 nm.