title: The effect of hydrophilic ionic liquids 1-ethyl-3-methylimidazolium lactate and choline lactate on lipid vesicle fusion.
abstract: 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.
authors.affiliation: Laboratory of Medical Zoology and Parasitology, Department of Infection and Immunity, Jichi Medical University, Shimotsuke, Tochigi, Japan.
authors.forename: Eri H
authors.initials: EH
authors.lastname: Hayakawa
authors.affiliation: Department of Applied Chemistry, Graduate School of Engineering, Osaka University, Suita, Osaka, Japan.
authors.forename: Eiko
authors.initials: E
authors.lastname: Mochizuki
authors.affiliation: Department of Applied Chemistry, Graduate School of Engineering, Osaka University, Suita, Osaka, Japan.
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Tsuda
authors.affiliation: Department of Polymer Chemistry, Graduate School of Engineering, Kyoto University, Kyoto, Kyoto, Japan ; Japan Science and Technology Agency, ERATO, Kawaguchi, Saitama, Japan.
authors.forename: Kazunari
authors.initials: K
authors.lastname: Akiyoshi
authors.affiliation: Laboratory of Medical Zoology and Parasitology, Department of Infection and Immunity, Jichi Medical University, Shimotsuke, Tochigi, Japan.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Matsuoka
authors.affiliation: Department of Applied Chemistry, Graduate School of Engineering, Osaka University, Suita, Osaka, Japan ; Japan Science and Technology Agency, CREST, Kawaguchi, Saitama, Japan.
authors.forename: Susumu
authors.initials: S
authors.lastname: Kuwabata
mesh_terms: D002794:Choline / Q000737:chemistry / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D057927:Hydrophobic and Hydrophilic Interactions; D007093:Imidazoles / Q000737:chemistry / Q000494:pharmacology*; D052578:Ionic Liquids / Q000737:chemistry / Q000494:pharmacology*; D019344:Lactic Acid / Q000737:chemistry / Q000494:pharmacology*; D008561:Membrane Fusion / Q000187:drug effects*; D053835:Unilamellar Liposomes / Q000378:metabolism*
chemical_list: D007093:Imidazoles; D052578:Ionic Liquids; D053835:Unilamellar Liposomes; D019344:Lactic Acid; D002794:Choline; C518739:1-ethyl-3-methylimidazolium