Paporakis Stefan, Brown Stuart J, Darmanin Connie, Seibt Susanne, Adams Patrick, Hassett Michael, Martin Andrew V, Greaves Tamar L
School of Science, College of STEM, RMIT University, 124 La Trobe Street, Melbourne VIC 3000, Australia.
La Trobe Institute for Molecular Science, Department of Mathematical and Physical Sciences, School of Computing Engineering and Mathematical Science, La Trobe University, Bundoora VIC 3086, Australia.
J Chem Phys. 2024 Jan 14;160(2). doi: 10.1063/5.0180420.
Monoolein-based liquid crystal phases are established media that are researched for various biological applications, including drug delivery. While water is the most common solvent for self-assembly, some ionic liquids (ILs) can support lipidic self-assembly. However, currently, there is limited knowledge of IL-lipid phase behavior in ILs. In this study, the lyotropic liquid crystal phase behavior of monoolein was investigated in six protic ILs known to support amphiphile self-assembly, namely ethylammonium nitrate, ethanolammonium nitrate, ethylammonium formate, ethanolammonium formate, ethylammonium acetate, and ethanolammonium acetate. These ILs were selected to identify specific ion effects on monoolein self-assembly, specifically increasing the alkyl chain length of the cation or anion, the presence of a hydroxyl group in the cation, and varying the anion. The lyotropic liquid crystal phases with 20-80 wt. % of monoolein were characterized over a temperature range from 25 to 65 °C using synchrotron small angle x-ray scattering and cross-polarized optical microscopy. These results were used to construct partial phase diagrams of monoolein in each of the six protic ILs, with inverse hexagonal, bicontinuous cubic, and lamellar phases observed. Protic ILs containing the ethylammonium cation led to monoolein forming lamellar and bicontinuous cubic phases, while those containing the ethanolammonium cation formed inverse hexagonal and bicontinuous cubic phases. Protic ILs containing formate and acetate anions favored bicontinuous cubic phases across a broader range of protic IL concentrations than those containing the nitrate anion.
基于单油酸甘油酯的液晶相是用于各种生物应用（包括药物递送）研究的成熟介质。虽然水是自组装最常用的溶剂，但一些离子液体（ILs）也能支持脂质自组装。然而，目前对于离子液体中离子液体 - 脂质相行为的了解有限。在本研究中，研究了单油酸甘油酯在六种已知能支持两亲分子自组装的质子性离子液体中的溶致液晶相行为，即硝酸乙铵、硝酸乙醇铵、甲酸乙铵、甲酸乙醇铵、乙酸乙铵和乙酸乙醇铵。选择这些离子液体是为了确定对单油酸甘油酯自组装的特定离子效应，特别是增加阳离子或阴离子的烷基链长度、阳离子中羟基的存在以及改变阴离子。使用同步加速器小角X射线散射和交叉偏振光学显微镜在25至65°C的温度范围内对单油酸甘油酯含量为20 - 80 wt.%的溶致液晶相进行了表征。这些结果用于构建单油酸甘油酯在六种质子性离子液体中的部分相图，观察到了反六角相、双连续立方相和层状相。含有乙铵阳离子的质子性离子液体导致单油酸甘油酯形成层状相和双连续立方相，而含有乙醇铵阳离子的则形成反六角相和双连续立方相。与含有硝酸根阴离子的质子性离子液体相比，含有甲酸根和乙酸根阴离子的质子性离子液体在更宽的质子性离子液体浓度范围内有利于双连续立方相的形成。
