pH非敏感型自交联共轭亚油酸囊泡的构建和表征

以共轭亚油酸(Conjugated linoleic acid, CLA)为构造pH非敏感型脂肪酸囊泡(Fatty acid vesicle, FAV)的分子砌块, 通过碱异构化法从亚油酸半合成CLA, 然后采用pH刺激响应自组装法获得CLA的不饱和脂肪酸囊泡(Ufasome), 采用紫外辐照诱导方式对CLA-ufasome实施囊泡内化学绑定, 获得一种新的pH非敏感型FAV. 通过酸碱滴定和表面张力实验确定CLA-ufasome形成的适宜pH范围和浓度, 利用透射电子显微镜(TEM)表征了自交联CLA的FAV的形貌, 并通过动态光散射(DLS)法测定了自交联CLA的FAV的稳定性. 结果表明, 以CLA为分子砌块, 当浓度为3 mmol/L时在pH=8.6条件下构建CLA-ufasome, 紫外辐照2.5 h后得到粒径为10~20 nm, 壁厚为2.0 nm的自交联CLA的FAV, 并具有pH非敏感的特性. 以抗癌药物五氟尿嘧啶为目标包覆药物, 体外释放实验结果表明, 自交联CLA的FAV对五氟尿嘧啶具有良好的缓释效果.     

利用烷基糖苷迁移和扩张共轭亚油酸囊泡pH窗口

脂肪酸囊泡(FAV)具有与脂质体类似的中空核壳结构, 且原料来源广泛, 绿色安全, 在包埋/缓释方面有重要意义. 但FAV对pH值依赖性强, pH窗口很窄并偏离生命体系适应pH范围, 限制了其作为包埋/缓释体在日用化学品及外用药等中的应用. 本文用绿色安全非离子表面活性剂烷基糖苷(APG)使共轭亚油酸(CLA)形成FAV的pH窗口从原先的8.0-9.0 迁移并扩张至6.0-8.0, 从而与生命体系适应pH值范围相匹配, 并探讨了改善FAV的pH值依赖性和敏感性的原理.     

共轭亚油酸与海藻酸钠囊泡化自组装纳米容器及其药物缓释性能

脂肪酸囊泡(FAV)是一类重要的纳米容器,然而其形成pH范围较窄且偏碱性环境,限制了其应用。 本文将共轭亚油酸(CLA)与海藻酸钠(SA)在近中性环境下共同自组装囊泡化纳米容器并提高其膜稳定性。动态激光光散射(DLS)和透射电子显微镜(TEM)结果表明,当SA质量分数为25%~50%时复合体系可在近中性条件下自组装形成50~250 nm尺寸的囊泡化纳米容器,且pH=7.4时随着质量分数增加囊泡化纳米容器直径增大。 根据SA和CLA在中性环境的物种存在形式推测,二者通过氢键作用驱动形成囊泡化纳米容器。 体外模拟释放实验表明,囊泡化纳米容器具有较高包覆率和较优缓释效果,有望应用于药物传输领域。     

单糖/双糖对近中性pH下共轭亚油酸囊泡影响的比较

比较了乳糖等3种双糖或核糖等3种单糖及其复配物对近中性范围共轭亚油酸(CLA)形成脂肪酸囊泡(FAV)的影响. 用激光丁达尔效应确定FAV的pH窗口及各相区, 用透射电子显微镜及动态光散射表征其形貌和尺寸, 用浊度法研究了其稳定性, 用等温滴定量热证明各种糖及其复配物与FAV表面的弱非共价键合作用, 并经理论计算获得结合能. 实验和计算结果表明, 各种糖及其复配物均可以双向拓宽CLA形成FAV的pH窗口, 且拓宽其近中性pH窗口的能力按照双糖<单糖≈双糖/单糖≤单糖/单糖的顺序依次增强. 主要归结为单糖在FAV表面的强竞争吸附, 以及双糖可能因多结合位点吸附而减少其自由羟基与环境水分子的缔合作用, 从而影响多羟基小分子依靠自由羟基增强囊泡表面亲水性的效果.     

单十二烷基磷酸酯辅助共轭亚油酸的囊泡化研究

以共轭亚油酸(CLA)为模型脂肪酸,与安全、温和的阴离子表面活性剂单十二烷基磷酸酯(MLP)进行复配,动态激光光散射和透射电镜表征结果表明,CLA在中性至弱酸性环境中仍然能够囊泡化.通过pH滴定曲线研究了CLA和MLP 2种分子的荷电物种随pH值的变化规律,据此分析各物种间的相互作用,并推断经MLP辅助CLA能够在中性至弱酸性环境中囊泡化的动因是CLA-MLP间的氢键或离子-偶极作用.     

低聚反应诱导碱性环境下共轭亚油酸钠囊泡化

通过控制紫外辐照共轭亚油酸钠(SCL)水溶液的双键平均交联度,以低聚反应诱导碱性环境下SCL自组装成脂肪酸囊泡(FAV),经透射电子显微镜观察到FAV大小为10～20 nm.性能实验结果表明,与SCL胶束相比,低聚SCL在碱性条件下自组装FAV溶液的低温溶解性更佳、耐酸性更好、抗钙皂能力更强,其粒径变化显示一定的钙离子响应性,因此其具有较大的FAV自组装理论研究价值,并在洗涤护理产品中显示出了更大的应用前景.     

自交联共轭亚油酸囊泡的温敏膨胀行为

采用紫外辐照引发共轭亚油酸(CLA)囊泡内聚合反应,获得自交联CLA囊泡.用动态激光光散射(DLS)和冷冻透射电子显微镜(cryo-TEM)等观察自交联CLA囊泡的粒径和形貌变化,结果表明,自交联CLA囊泡的囊泡结构不仅不随温度变化解体,而且表现出明显的温敏膨胀性.自交联CLA囊泡体外释放5-氟尿嘧啶的实验表明其具有温度响应的缓释和控释特性.     

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.     

自交联共轭亚油酸囊泡基荧光纳米点的构筑及其荧光特性

提出了一种生物质碳源借助自组装和自交联手段“构筑”碳基荧光纳米点(FNDs)的新策略,不同于经历裂解、脱水、缩聚和碳化等复杂且不可控反应的“合成”途径。本文以共轭亚油酸(CLA)为碳源,利用其表面活性和聚合活性制得呈蓝绿光发射的自交联共轭亚油酸囊泡基荧光纳米点(SCU-FNDs),粒径易控(平均粒径为17 nm)且具有良好水分散性,FNDs产率高达73.9%。该法简便温和、绿色经济、有利于大规模制备。荧光实验结果显示SCU-FNDs的荧光强度随囊泡表面羧酸基团减少而减弱,随自交联度增大而增大; 同时其荧光强度具有良好的温度线性响应性,升/降温过程均符合I/I₀ = -0.00977T+ 1.229 (T = 25-85 ℃, R² = 0.99)。这些荧光特性皆可以用SCU-FNDs的自组装和自交联结构特性予以解释。     

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.     

油酸囊泡尺度多分散性及二元醇对其pH窗口的影响

以油酸(OA)为模型脂肪酸, 依据目测激光丁达尔现象在pH滴定曲线上划分相区, 确定OA囊泡化pH窗口为8.2~10.1. 利用光学显微镜、 激光共聚焦显微镜和冷冻刻蚀-透射电子显微镜共同表征了OA囊泡的形貌及粒径, 发现体系中微米和亚微米级的多层囊泡以及纳米级的单层囊泡共存, 呈现尺度多分散性. 用不同链长的短链二元醇辅助OA形成囊泡, 结果表明, 短链二元醇有助于脂肪酸囊泡(FAV)的pH窗口拓宽, 拓宽的方向取决于表面氢键作用方式或疏水插入方式. 在酸性条件下二元醇与FAV相互作用后, 在囊泡表面残留的自由羟基越多, 越有助于拓宽其酸性pH窗口.     

共轭亚油酸修饰Fe3O4纳米颗粒的刺激响应性

采用少量天然不饱和脂肪酸共轭亚油酸(CLA)代替常用油酸对Fe₃O₄纳米颗粒进行表面修饰. 通过引发CLA中共轭双键自交联增强表面修饰牢度, 并利用该修饰层为修饰后的Fe₃O₄纳米颗粒提供第二重pH响应性. 分别通过透射电子显微镜(TEM)表征粒径和形貌、 全反射傅里叶变换红外光谱(ATR-FTIR)表征配位模式、 热重(TG)分析修饰量、 θ角表征表面润湿性、 超景深三维显微技术表征修饰后颗粒稳定的Pickering乳液的粒径及分布等. 结果表明, 修饰后颗粒具有分散性好、 修饰层薄而稳定、 表面疏水性增强及具有明显的pH/磁双重响应性等特征. 修饰后颗粒稳定的Pickering乳液具有乳化剂用量(质量分数0.05%)少、 乳液为高内(油)相(体积分数80%)类型、 pH响应能够开关乳液、 外磁场驱使乳液定向移动等特征, 且模拟实验显示借助该乳液可以有效实现水相有机污染物的萃取与分离.     

pH-dependent release from ethylcellulose microparticles containing alginate and calcium carbonate

Ethylcellulose microparticles containing alginate and calcium carbonate nanoparticles were prepared by spray drying water-in-oil emulsion. Alginate solution (3%) in distilled water was used as an aqueous phase, ethylcellulose solution (5%) in dichloromethane as an oil phase, and sorbitan sesquioleate as an emulsifier. The nanoparticles of calcium carbonate were dispersed into the emulsion. By spray-drying the emulsion, ethylcellulose microparticles containing alginate and calcium carbonate were obtained. When the ratios of alginate to calcium carbonate were 4:1 and 2:1, the pH dependency of the release was marked and the degree of release was suppressed in acidic conditions. When the ratio increased to 1:2, the degree of release increased while the pH-dependent release profiles were maintained. Cavities created by the dissolution of calcium carbonate could account for the increased release.     

Development and validation of polymerized high internal phase emulsion monoliths coupled with HPLC and fluorescence detection for the determination of trace tetracycline antibiotics in environmental water samples

A polymerized high internal phase emulsion monolith was used as a novel sorbent for solid‐phase extraction coupled with high‐performance liquid chromatography and fluorescence detection for the determination of oxytetracycline, tetracycline, doxycycline, and chlorotetracycline in environmental water samples. The polymerized high internal phase emulsion monolithic column was prepared by the in situ polymerization of the continuous phase of a high internal phase emulsion containing glycidyl methacrylate, styrene, and divinylbenzene in pipette tips, and then functionalized with iminodiacetic acid. The resulting monolith exhibited highly interconnected porosity and large surface areas, making it an excellent candidate as an solid‐phase extraction sorbent for the enrichment of trace tetracycline antibiotics. Several factors affecting the extraction performance of polymerized high internal phase emulsion monoliths, including the pH of sample solution, the eluting solvents, the sample loading flow rate and volume, were investigated, respectively. Under the optimized conditions, the mean recoveries of oxytetracycline, tetracycline, doxycycline, and chlorotetracycline spiked in pond and farm wastewater samples ranged from 78.1 to 119.3% with relative standard deviation less than 15%. The detection limits (S/N = 3) of the proposed method were in the range of 51–137 pg/mL. This study demonstrated that the monolithic polymerized high internal phase emulsion would be promising solid‐phase extraction sorbents in the extraction and proconcentration of trace analytes from complex samples.     

Fabrication of macroporous foam and microspheres of polystyrene by Pickering emulsion polymerization

Poly(styrene-co-methacrylic acid) (PS-co-MAA) particles were synthesized via surfactant-free emulsion polymerization and then used as particulate emulsifiers for preparation of Pickering emulsions. Our results showed that adjusting the solution pH can tune the wettability of PS-co-MAA particles to stabilize either water-in-oil (W/O) or oil-in-water (O/W) Pickering emulsions. Stable W/O emulsions were obtained with PS-co-MAA particles at low pH values due to their better affinity to the dispersed oil phase. In contrast, increasing the pH value significantly changed the stabilizing behavior of the PS-co-MAA particles, leading to the phase inversion and formation of stable O/W emulsions. We found that the oil/water ratio had a significant influence on pH value of the phase inversion. It decreased with decreasing the oil/water ratio, and no phase inversion occurred when the styrene volume fraction reduced to 10 %. Additionally, macroporous polystyrene (PS) foam and PS microspheres were obtained via polymerization of Pickering high internal phase emulsion (Pickering HIPE) and O/W Pickering emulsion, respectively.     

Thermal properties of poly(methyl methacrylate) prepared by emulsifier-free emulsion polymerization

Emulsifier-free emulsion polymerization of methyl methacrylate in the presence of potassium persulfate initiator, taken in several different concentrations, at various pH values was studied with the aim to obtain colloidal crystals. The thermal properties of poly(methyl methacrylate) prepared by emulsifier-free emulsion polymerization, as the starting material for fabrication of photonic crystals, were examined in relation to the synthesis conditions.