Hayakawa Eri H, Mochizuki Eiko, Tsuda Tetsuya, Akiyoshi Kazunari, Matsuoka Hiroyuki, Kuwabata Susumu
Laboratory of Medical Zoology and Parasitology, Department of Infection and Immunity, Jichi Medical University, Shimotsuke, Tochigi, Japan.
Department of Applied Chemistry, Graduate School of Engineering, Osaka University, Suita, Osaka, Japan.
PLoS One. 2013 Dec 31;8(12):e85467. doi: 10.1371/journal.pone.0085467. eCollection 2013.
Ionic liquids (ILs) are room-temperature molten salts that have applications in both physical sciences and more recently in the purification of proteins and lipids, gene transfection and sample preparation for electron microscopy (EM) studies. Transfection of genes into cells requires membrane fusion between the cell membrane and the transfection reagent, thus, ILs may be induce a membrane fusion event. To clarify the behavior of ILs with cell membranes the effect of ILs on model membranes, i.e., liposomes, were investigated. We used two standard ILs, 1-ethyl-3-methylimidazolium lactate ([EMI][Lac]) and choline lactate ([Ch][Lac]), and focused on whether these ILs can induce lipid vesicle fusion. Fluorescence resonance energy transfer and dynamic light scattering were employed to determine whether the ILs induced vesicle fusion. Vesicle solutions at low IL concentrations showed negligible fusion when compared with the controls in the absence of ILs. At concentrations of 30% (v/v), both types of ILs induced vesicle fusion up to 1.3 and 1.6 times the fluorescence intensity of the control in the presence of [Ch][Lac] and [EMI][Lac], respectively. This is the first demonstration that [EMI][Lac] and [Ch][Lac] induce vesicle fusion at high IL concentrations and this observation should have a significant influence on basic biophysical studies. Conversely, the ability to avoid vesicle fusion at low IL concentrations is clearly advantageous for EM studies of lipid samples and cells. This new information describing IL-lipid membrane interactions should impact EM observations examining cell morphology.
离子液体（ILs）是室温熔融盐，在物理科学领域以及最近在蛋白质和脂质的纯化、基因转染和电子显微镜（EM）研究的样品制备中都有应用。将基因转染到细胞中需要细胞膜与转染试剂之间发生膜融合，因此，离子液体可能会引发膜融合事件。为了阐明离子液体与细胞膜的相互作用，研究了离子液体对模型膜即脂质体的影响。我们使用了两种标准离子液体，1-乙基-3-甲基咪唑鎓乳酸盐（[EMI][Lac]）和胆碱乳酸盐（[Ch][Lac]），并着重研究这些离子液体是否能诱导脂质囊泡融合。采用荧光共振能量转移和动态光散射来确定离子液体是否诱导囊泡融合。与不存在离子液体的对照组相比，低离子液体浓度下的囊泡溶液显示出可忽略不计的融合。在30%（v/v）的浓度下，两种类型的离子液体都能诱导囊泡融合，在存在[Ch][Lac]和[EMI][Lac]时，荧光强度分别达到对照组的1.3倍和1.6倍。这是首次证明[EMI][Lac]和[Ch][Lac]在高离子液体浓度下能诱导囊泡融合，这一观察结果对基础生物物理研究应具有重大影响。相反，在低离子液体浓度下避免囊泡融合的能力对于脂质样品和细胞的电子显微镜研究显然是有利的。这一描述离子液体与脂质膜相互作用的新信息应该会影响对细胞形态的电子显微镜观察。
