Tanner Eden E L, Piston Kathryn M, Ma Huilin, Ibsen Kelly N, Nangia Shikha, Mitragotri Samir
John A. Paulson School of Engineering and Applied Sciences, Harvard University, 29 Oxford Street, Cambridge, Massachusetts 02138, United States.
Department of Biomedical and Chemical Engineering, Syracuse University, 223 Link Hall, Syracuse, New York 13244, United States.
ACS Biomater Sci Eng. 2019 Jul 8;5(7):3645-3653. doi: 10.1021/acsbiomaterials.9b00243. Epub 2019 May 31.
Choline and geranic acid (CAGE)-based ionic liquids have been recently developed for applications in drug delivery. Understanding the microscopic structures of CAGE in the presence of water is critical for its continued use in biomedical applications as it will undoubtedly come into contact with water in physiological fluids. Water can drastically impact the physicochemical properties of the ionic liquids, including CAGE. Computational and experimental characterization, namely viscosity, conductivity, and self-diffusion coefficient, were employed here to understand the properties of equimolar CAGE (1:1 choline/geranic acid) in the presence of varying amounts of water. It was found that under stored conditions, 1:1 CAGE contained up to 0.20 mole fraction water. Experimental and computational studies indicate that microscopic intraionic interactions within CAGE are not substantially changed until the water content exceeds 0.65 mole fraction. At this point, we theorize that the geranate ions undergo reorganization to minimize contact between the hydrophobic tails and the water molecules. This is evidenced by the plateau in viscosity at this mole fraction, and the increased interactions between the tails of the anions. This suggests that CAGE could be used without predrying in most applications and can be diluted to induce the organization of the anions where desired.
基于胆碱和香叶酸（CAGE）的离子液体最近已被开发用于药物递送应用。了解CAGE在有水存在时的微观结构对于其在生物医学应用中的持续使用至关重要，因为它无疑会在生理流体中与水接触。水会极大地影响离子液体的物理化学性质，包括CAGE。这里采用了计算和实验表征，即粘度、电导率和自扩散系数，来了解在不同水量存在下等摩尔CAGE（1:1胆碱/香叶酸）的性质。发现在储存条件下，1:1 CAGE含有高达0.20摩尔分数的水。实验和计算研究表明，在水含量超过0.65摩尔分数之前，CAGE内的微观离子间相互作用没有实质性变化。在这一点上，我们推测香叶酸根离子会进行重组，以尽量减少疏水尾部与水分子之间的接触。这在该摩尔分数下粘度的平稳期以及阴离子尾部之间增加的相互作用中得到了证明。这表明在大多数应用中CAGE无需预先干燥即可使用，并且可以稀释以在需要时诱导阴离子的有序排列。
