Room-Temperature Ionic Liquids and Biomembranes: Setting the Stage for Applications in Pharmacology, Biomedicine, and Bionanotechnology

Impact of Ionic Liquids on the Physicochemical Behavior of Vesicles

The effects of two ionic liquids (ILs), 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim]BF4) and 1-butyl-1-methyl pyrrolidinium tetrafluoroborate ([bmp]BF4), on a mixture of phospholipids (PLs) 1,2-dipalmitoyl-sn-glycero-3-phosphatidylcholine (DPPC), 1,2-dipalmitoyl-sn-glycero-3-phosphoethanolamine (DPPE), and 1,2-dipalmitoyl-sn-glycero-3-phosphoglycerol (DPPG) (6:3:1, M/M/M, 70% PL) in combination with 30 mol % cholesterol (CHOL) were investigated in the form of a solvent-spread monolayer and bilayer (vesicle). Surface pressure (π)-area (A) isotherm studies, using a Langmuir surface balance, revealed the formation of an expanded monolayer, while the cationic moiety of the IL molecules could electrostatically and hydrophobically bind to the PLs on the palisade layer. Turbidity, dynamic light scattering (size, ζ-potential, and polydispersity index), electron microscopy, small-angle X-ray/neutron scattering, fluorescence spectroscopy, and differential scanning calorimetric studies were carried out to evaluate the effects of IL on the structural organization of bilayer in the vesicles. The ILs could induce vesicle aggregation by acting as a "glue" at lower concentrations (<1.5 mM), while at higher concentrations, the ILs disrupt the bilayer structure. Besides, ILs could result in the thinning of the bilayer, evidenced from the scattering studies. Steady-state fluorescence anisotropy and lifetime studies suggest asymmetric insertion of ILs into the lipid bilayer. MTT assay using human blood lymphocytes indicates the safe application of vesicles in the presence of ILs, with a minimal toxicity of up to 2.5 mM IL in the dispersion. These results are proposed to have applications in the field of drug delivery systems with benign environmental impact.

Mechanisms of Biological Effects of Ionic Liquids: From Single Cells to Multicellular Organisms

The review presents a detailed discussion of the evolving field studying interactions between ionic liquids (ILs) and biological systems. Originating from molten salt electrolytes to present multiapplication substances, ILs have found usage across various fields due to their exceptional physicochemical properties, including excellent tunability. However, their interactions with biological systems and potential influence on living organisms remain largely unexplored. This review examines the cytotoxic effects of ILs on cell cultures, biomolecules, and vertebrate and invertebrate organisms. Our understanding of IL toxicity, while growing in recent years, is yet nascent. The established findings include correlations between harmful effects of ILs and their ability to disturb cellular membranes, their potential to trigger oxidative stress in cells, and their ability to cause cell death via apoptosis. Future research directions proposed in the review include studying the distribution of various ILs within cellular compartments and organelles, investigating metabolic transformations of ILs in cells and organisms, detailed analysis of IL effects on proteins involved in oxidative stress and apoptosis, correlation studies between IL doses, exposure times and resulting adverse effects, and examination of effects of subtoxic concentrations of ILs on various biological objects. This review aims to serve as a critical analysis of the current body of knowledge on IL-related toxicity mechanisms. Furthermore, it can guide researchers toward the design of less toxic ILs and the informed use of ILs in drug development and medicine.

Ionic liquid-mediated ethosome for transdermal delivery of insulin

Herein, we report ethosome (ET) formulations composed of a safe amount of 1,2-dimyristoyl-sn-glycero-3-phosphatidylcholine (DMPC)-based ionic liquid with various concentrations of ethanol as a carrier for the transdermal delivery of a high molecular weight drug, insulin. The Insulin-loaded ET vesicles exhibited long-term stability compared to conventional DMPC ETs, showing significantly higher drug encapsulation efficiency and increased skin permeation ability.

Interaction and antibacterial activity of ciprofloxacin with choline based ionic liquid and CTAB: A comparative spectroscopic study

In this study, the complexation of potential chemo-therapeutic antibacterial drug, ciprofloxacin (CIP) with varying concentrations of surface active compounds (SACs) i.e., (N-(2-hydroxyethyl)-N,N-dimethyl-1-dodecanaminium bromide (12Cho.Br) and cetyltrimethylammonium bromide (CTAB) has been studied. Multispectroscopic techniques were exploited to carry out the study. The higher binding constant (Kb) value for CIP-CTAB than CIP-12Cho.Br obtained from fluorescence data revealed stronger binding of CTAB than 12Cho.Br, owing to the stronger hydrophobic-hydrophobic interaction betweeen CIP and CTAB compared to CIP and 12Cho.Br. The time resolve fluorescence decay shows changes in average lifetime (τavg) with the increasing concentration of 12Cho.Br and CTAB. The changes in τavg suggests that complex formation is taking place between CIP and 12Cho.Br / CTAB. Further, the formation of micelles by 12Cho.Br / CTAB and the effect of alkyl chain length was studied by dynamic light scattering (DLS) and zeta potential to confirm the drug complexation with 12Cho.Br and CTAB. The antibacterial activity has been performed for CIP and 12Cho.Br and CTAB. It was observed that in presence of lower concentrations of 12Cho.Br/ CTAB, the activity of the drug increased. The activity was also found cationic alkyl chain length dependent. Moreover, in-vitro cytotoxicity of CIP and its combinations with 12Cho.Br and CTAB was performed using MTT assay on HEK293 (Human embryonic kidney cells).

Ionic liquids meet lipid bilayers: a state-of-the-art review

In the past 25 years, a vast family of complex organic salts known as room-temperature ionic liquids (ILs) has received increasing attention due to their potential applications. ILs are composed by an organic cation and either an organic or inorganic anion, and possess several intriguing properties such as low vapor pressure and being liquid around room temperature. Several biological studies flagged their moderate-to-high (cyto)-toxicity. Toxicity is, however, also a synonym of affinity, and this boosted a series of biophysical and chemical-physical investigations aimed at exploiting ILs in bio-nanomedicine, drug-delivery, pharmacology, and bio-nanotechnology. Several of these investigations focused on the interaction between ILs and lipid membranes, aimed at determining the microscopic mechanisms behind their interaction. This is the focus of this review work. These studies have been carried out on a variety of different lipid bilayer systems ranging from 1-lipid to 5-lipids systems, and also on cell-extracted membranes. They have been carried out at different chemical-physical conditions and by the use of a number of different approaches, including atomic force microscopy, neutron and X-ray scattering, dynamic light scattering, differential scanning calorimetry, surface quartz microbalance, nuclear magnetic resonance, confocal fluorescence microscopy, and molecular dynamics simulations. The aim of this "2023 Michèle Auger Award" review work is to provide the reader with an up-to-date overview of this fascinating research field where "ILs meet lipid bilayers (aka biomembranes)," with the aim to boost it further and expand its cross-disciplinary edges towards novel high-impact ideas/applications in pharmacology, drug delivery, biomedicine, and bio-nanotechnology.

Screening of Ionic Liquids against Bamboo Mildew and Its Inhibition Mechanism

Ionic liquids are a class of organic molten salts that consist entirely of cations and anions. They are characterized by their low vapor pressure, low viscosity, low toxicity, high thermal stability, and strong antifungal potential. In this study, the inhibitory performance of ionic liquid cations against Penicillium citrinum, Trichoderma viride, and Aspergillus niger was investigated, along with the mechanism of cell membrane disruption. The Oxford cup method, SEM, and TEM were employed to examine the extent of damage and the specific site of action of ionic liquids on the mycelium and cell structure of these fungi. The results showed that 1-decyl-3-methylimidazole had a strong inhibitory effect on TV; benzyldimethyldodecylammonium chloride had a weak inhibitory effect on PC, TV, AN, and a mixed culture; while dodecylpyridinium chloride exhibited significant inhibitory effects on PC, TV, AN, and Mix, with more prominent effects observed on AN and Mix, exhibiting MIC values of 5.37 mg/mL, 5.05 mg/mL, 5.10 mg/mL, and 5.23 mg/mL, respectively. The mycelium of the mildews showed drying, partial loss, distortion, and uneven thickness. The cell structure showed separation of the plasma wall. The absorbance of the extracellular fluid of PC and TV reached the maximum after 30 min, while that of AN reached the maximum after 60 min. The pH of the extracellular fluid decreased initially and then increased within 60 min, followed by a continuous decrease. These findings provide important insights for the application of ionic liquid antifungal agents in bamboo, medicine, and food.

Photochromic and Luminescent Properties of a Salt of a Hybrid Molecule Based on C60 Fullerene and Spiropyran-A Promising Approach to the Creation of Anticancer Drugs

For the first time a pyrrolidinofullerene salt containing a spiropyran group and an ammonium group, capable of reversibly reacting to UV radiation, has been synthesized. Photoinduced reactions of the synthesized compounds were studied using absorption and luminescence spectroscopies, spectral and kinetic characteristics were measured. The hybrid molecule was found to exhibit intrinsic fluorescence even in the spirocyclic form. The C₆₀ derivative showed a higher stability and better spectral and luminescent properties than the precursor.

Synthesis, Photochromic and Luminescent Properties of Ammonium Salts of Spiropyrans

New salts of photochromic indoline spiropyrans capable of reversibly responding to UV radiation were synthesized to develop light-controlled materials. Photoinduced reactions of the synthesized compounds were studied using absorption and luminescence spectroscopies, and the quantum yields of photoisomerization and other spectral and kinetic characteristics were measured. It was shown that the light sensitivity and photostability of the synthesized compounds are considerably influenced by the length of the spacer between the indole and ammonium nitrogen atoms.

Phenylpropyl Guanidinium Magnetic Ionic Liquid for Green and Selective Extraction of RNA

A phenylpropyl guanidinium magnetic ionic liquid (PGMIL) was designed and prepared to extract RNA from complex samples. The properties of PGMIL were characterized by a vibrating sample magnetometer, Fourier transform infrared spectrometer, thermogravimetric analyzer, transmission electron microscope, and scanning electron microscope. Through single-factor analysis, the factors affecting the RNA extraction process, such as PGMIL volume, temperature, extraction time, and pH, were systematically investigated. The ability of PGMIL to selectively extract RNA was investigated by a NanoDrop. Under the optimized conditions, the extraction efficiency of RNA can reach 81.9 ± 1.9%. The proposed extraction method has been demonstrated with the extraction of RNA from a series of complex sample matrices, including a metal ion mixture and medicinal yeast. After extraction, the retained RNA could be readily recovered by simply using Tris-HCl buffer, with a recovery rate of 68.11 ± 2.45%. Regeneration studies have shown that the extraction efficiency of PGMIL did not change significantly after using 4 times. This study provides a green, rapid, and environmental friendly extraction method for the selective extraction of RNA.

Controlling Amyloid Fibril Properties Via Ionic Liquids: The Representative Case of Ethylammonium Nitrate and Tetramethylguanidinium Acetate on the Amyloidogenesis of Lysozyme

Protein aggregation into amyloid fibrils has been observed in several pathological conditions and exploited in nanotechnology. It is also key in several biochemical processes. In this work, we show that ionic liquids (ILs), a vast class of organic electrolytes, can finely tune amyloid properties, opening a new landscape in basic science and applications. The representative case of ethylammonium nitrate (EAN) and tetramethyl-guanidinium acetate (TMGA) ILs on lysozyme is considered. First, atomic force microscopy has shown that the addition of EAN and TMGA leads to thicker and thinner amyloid fibrils of greater and lower electric potential, respectively, with diameters finely tunable by IL concentration. Optical tweezers and neutron scattering have shed light on their mechanism of action. TMGA interacts with the protein hydration layer only, making the relaxation dynamics of these water molecules faster. EAN interacts directly with the protein instead, making it mechanically unstable and slowing down its relaxation dynamics.

Thermodynamics and In-Plane Viscoelasticity of Anionic Phospholipid Membranes Modulated by an Ionic Liquid

This article presents the effects of an imidazolium-based ionic liquid (IL) on the thermodynamics and in-plane viscoelastic properties of model membranes of anionic phospholipids. The negative Zeta potential of multilamellar vesicles of 14 carbon lipid 1,2-dimyristoyl-sn-glycero-3-phospho-(1'-rac-glycerol) (DMPG) is observed to reduce due to the presence of few mole % of an IL 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM][BF₄]). The effect was found to be stronger on enhancing the chain length of the lipid. The surface pressure-area isotherms of lipid monolayer formed at air-water interface are modified by the IL reducing the effective area per molecule. Further, the equilibrium elasticity of the film is altered depending upon the thermodynamic phase of the lipids. While the presence of the IL in the DMPG lipid makes it ordered in the gel phase by reducing the entropy, the effect is opposite in the fluid phase. The in-plane viscoelastic parameters of the lipid film is quantified by dilation rheology using the oscillatory barriers of a Langmuir trough. Even though the low chain lipid DMPG does not show any effect of IL on its storage and loss moduli, the longer chain lipids exhibit a prominent effect in the liquid extended (LE) phase. Further, the dynamic response of the lipid film is found to be distinctly different in the liquid condensed (LC) phase from that of the LE phase.

Absorption of the [bmim][Cl] Ionic Liquid in DMPC Lipid Bilayers across Their Gel, Ripple, and Fluid Phases

Lipid bilayers are a key component of cell membranes and play a crucial role in life and in bio-nanotechnology. As a result, controlling their physicochemical properties holds the promise of effective therapeutic strategies. Ionic liquids (ILs)—a vast class of complex organic electrolytes—have shown a high degree of affinity with lipid bilayers and can be exploited in this context. However, the chemical physics of IL absorption and partitioning into lipid bilayers is yet to be fully understood. This work focuses on the absorption of the model IL [bmim][Cl] into 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) lipid bilayers across their gel, ripple, and fluid phases. Here, by small-angle neutron scattering, we show that (i) the IL cations are absorbed in the lipid bilayer in all its thermodynamic phases and (ii) the amount of IL inserted into the lipid phase increased with increasing temperature, changing from three to four IL cations per 10 lipids with increasing temperature from 10 °C in the gel phase to 40 °C in the liquid phase, respectively. An explicative hypothesis, based on the entropy gain coming from the IL hydration water, is presented to explain the observed temperature trend. The ability to control IL absorption with temperature can be used as a handle to tune the effect of ILs on biomembranes and can be exploited in bio-nanotechnological applications.

Interactions between a dsDNA Oligonucleotide and Imidazolium Chloride Ionic Liquids: Effect of Alkyl Chain Length, Part I

Ionic liquids (ILs) have become nearly ubiquitous solvents and their interactions with biomolecules has been a focus of study. Here, we used the fluorescence emission of DAPI, a groove binding fluorophore, coupled with molecular dynamics (MD) simulations to report on interactions between imidazolium chloride ([Im_n,1]⁺) ionic liquids and a synthetic DNA oligonucleotide composed entirely of T/A bases (7(TA)) to elucidate the effects ILs on a model DNA duplex. Spectral shifts on the order of 500–1000 cm⁻¹, spectral broadening (~1000 cm⁻¹), and excitation and emission intensity ratio changes combine to give evidence of an increased DAPI environment heterogeneity on added IL. Fluorescence lifetimes for DAPI/IL solutions yielded two time constants 0.15 ns (~80% to 60% contribution) and 2.36–2.71 ns for IL up to 250 mM. With DNA, three time constants were required that varied with added IL (0.33–0.15 ns (1–58% contribution), ~1.7–1.0 ns (~5% contribution), and 3.8–3.6 ns (94–39% contribution)). MD radial distribution functions revealed that π-π stacking interactions between the imidazolium ring were dominant at lower IL concentration and that electrostatic and hydrophobic interactions become more prominent as IL concentration increased. Alkyl chain alignment with DNA and IL-IL interactions also varied with IL. Collectively, our data showed that, at low IL concentration, IL was primarily bound to the DNA minor groove and with increased IL concentration the phosphate regions and major groove binding sites were also important contributors to the complete set of IL-DNA duplex interactions.

Mechanistic Insight on BioIL-Induced Structural Alterations in DMPC Lipid Bilayer

The emerging application risks of traditional ionic liquids (ILs) toward the ecosystem have changed the perception regarding their greenness. This resulted in the exploration of their more biocompatible alternatives known as biocompatible ILs (BioILs). Here, we have investigated the impact of two such biocompatible cholinium amino acid-based ILs on the structural behavior of model homogeneous DMPC (1,2-dimyristoyl-sn-glycero-3-phosphocholine) lipid bilayer using all-atom molecular dynamics simulation technique. Two classic cholinium-amino acid-based ILs, cholinium glycinate ([Ch][Gly]) and cholinium phenylalaninate ([Ch][Phe]), which differ only by the side chain lengths and hydrophobicity of the anions, have been utilized in the present work. Simultaneous analysis of the bilayer structural properties reveals that the existence of [Ch][Gly] BioIL above a particular concentration induces phase transition from fluid phase to gel phase in the DMPC lipid bilayer. Such a freezing of lipid bilayer upon the exposure to concentrated aqueous solution of [Ch][Gly] BioIL indicates the harmfulness of this BioIL toward the cell membranes majorly containing DMPC lipids, as the cell freezing can negatively affect its stability and functionality. Despite having a more hydrophobic amino acid side chain of [Phe]^- anion in [Ch][Phe], in the case of bilayer-[Ch][Phe] systems we observe the minimal impact of [Ch][Phe] BioIL on the DMPC bilayer properties up to 10 mol % concentration. In the presence of these BioIL, we observe the thickening of the bilayer and accumulation of the cations and anions of the BioILs at the interface of DMPC lipid heads and tails. The transfer free-energy profile of a [Phe]^- anion from aqueous phase to membrane center also indicates the anion partitioning at lipid head-tail interface and its inability to penetrate in the lipid membrane tail region. In contrast, the free-energy profile for a [Gly]^- anion offers a very high energy barrier to the insertion of [Gly]^- into the membrane interior, leading to accumulation of [Gly]^- anions at the lipid head-water region.

Thermodynamical Origin of Nonmonotonic Inserting Behavior of Imidazole Ionic Liquids into the Lipid Bilayer

The GPU-accelerated molecular dynamics simulations are performed to explore the dynamical inserting process of ionic liquids (ILs) into the lipid bilayer. We found that the free ions and clusters coexist in the system, but only the cation can insert into the lipid bilayer. In specific, after a microsecond-scale simulation (up to 1.16 μs), the inserting rate increases first and then decreases nonmonotonic as side chain of cation (n_chain) elongates, peaking at n_chain = 10. However, the inserting free energy decreases with n_chain, indicating the inserting process is easier for the larger n_chain. Such contrary originates from the formation of cluster, where the cluster dissociating energy shows that only cluster for n_chain ≤ 10 can dissociate spontaneously. Hence, the inserting rate is determined by the balance between n_chain and cluster stability. These quantitative competition mechanisms shed light to the rational design of the biocompatible ILs toward their applications in the biochemical-related fields.

Guanidinium Hydrophobic Magnetic Ionic Liquid-Based Dispersive Droplet Extraction for the Selective Extraction of DNA

Six hydrophobic magnetic guanidinium ionic liquids (HMILs) were designed and prepared for the extraction of DNA. The physical and thermal properties of the HMILs were characterized using vibrating sample magnetometry, density meter, rotational rheometer, Karl Fischer moisture, Fourier transform infrared spectrometry, and thermogravimetric analysis. Single-stranded DNA and duplex DNA extracted by HMILs can be rapidly collected by a magnet. Three assisted extraction methods, including vortex extraction, mechanical shaking extraction, and ultrasonic extraction, were introduced to extract DNA with HMILs and the extraction efficiencies were evaluated using NanoDrop. Influencing factors of the DNA extraction were comprehensively evaluated, involving the HMIL volume, extraction time, pH, and extraction temperature. The HMIL-based extraction method can well extract DNA from complex matrices and Escherichia coli cell lysates.

Synthesis of Poly(ionic Liquid)s-block-poly(methyl Methacrylate) Copolymer-Grafted Silica Particle Brushes with Enhanced CO2 Permeability and Mechanical Performance

Poly(ionic liquid) (PIL)-based block copolymers are of particular interest as they combine the specific properties of PILs with the self-assembling behaviors of block copolymers, broadening the range of potential applications for PIL-based materials. In this work, three particle brushes: SiO₂-g-poly(methyl methacrylate) (PMMA), SiO₂-g-PIL, and SiO₂-g-PMMA-b-PIL were prepared through surface-initiated atom transfer radical polymerization. Unlike the homogeneous homopolymer particle brushes, the block copolymer particle brush SiO₂-g-PMMA-b-PIL exhibited a bimodal chain architecture and unique phase-separated morphology, which were confirmed by size-exclusion chromatography and transmission electron microscopy. In addition, the influence of the introduction of the PMMA segment on the gas separation and mechanical performance of the PIL-containing block copolymer particle brushes were investigated. A significant improvement of Young's modulus was observed in the SiO₂-g-PMMA-b-PIL compared to the SiO₂-g-PIL bulk films; meanwhile, their gas separation performances (CO₂ permeability and CO₂/N₂ selectivity) were the same, which demonstrates the possibility of improving the mechanical properties of PIL-based particle brushes without compromising their gas separation performance.

Recent Advances in Ionic Liquids in Biomedicine

The use of ionic liquids and deep eutectic solvents in biomedical applications has grown dramatically in recent years due to their unique properties and their inherent tunability. This review will introduce ionic liquids and deep eutectics and discuss their biomedical applications, namely solubilization of drugs, creation of active pharmaceutical ingredients, delivery of pharmaceuticals through biological barriers, stabilization of proteins and other nucleic acids, antibacterial agents, and development of new biosensors. Current challenges and future outlooks are discussed, including biocompatibility, the potential impact of the presence of impurities, and the importance of understanding the microscopic interactions in ionic liquids in order to design task-specific solvents.

Stiffening Effect of the [Bmim][Cl] Ionic Liquid on the Bending Dynamics of DMPC Lipid Vesicles

The elastic properties of the cellular lipid membrane play a crucial role for life. Their alteration can lead to cell malfunction, and in turn, being able to control them holds the promise of effective therapeutic and diagnostic approaches. In this context, due to their proven strong interaction with lipid bilayers, ionic liquids (ILs)-a vast class of organic electrolytes-may play an important role. This work focuses on the effect of the model imidazolium-IL [bmim][Cl] on the bending modulus of DMPC lipid vesicles, a basic model of cellular lipid membranes. Here, by combining small-angle neutron scattering and neutron spin-echo spectroscopy, we show that the IL, dispersed at low concentrations at the bilayer-water interface, (i) diffuses into the lipid region, accounting for five IL-cations for every 11 lipids, and (ii) causes an increase of the lipid bilayer bending modulus, up to 60% compared to the neat lipid bilayer at 40 °C.

Discerning perturbed assembly of lipids in a model membrane in presence of violacein

Violacein is a naturally found pigment that is used by some gram negative bacteria to defend themselves from various gram positive bacteria. As a result, this molecule has caught attention for its potential biomedical applications and has already shown promising outcomes as an antiviral, an antibacterial, and an anti-tumor agent. Understanding the interaction of this molecule with a cellular membrane is an essential step to extend its use in the pharmaceutical paradigm. Here, the interaction of violacein with a lipid monolayer formed at the air-water interface is found to depend on electrostatic nature of lipids. In presence of violacein, the two dimensional (2D) pressure-area isotherms of lipids have exhibited changes in their phase transition pressure and in-plane elasticity. To gain insights into the out-of-plane structural organization of lipids in a membrane, X-ray reflectivity (XRR) study on a solid supported lipid monolayer on a hydrophilic substrate has been performed. It has revealed that the increase in membrane thickness is more pronounced in the zwitterionic and positively charged lipids compared to the negatively charged one. Further, the lipid molecules are observed to decrease their tilt angle made with the normal of lipid membrane along with an alteration in their in-plane ordering. This has been quantified by grazing incidence X-ray diffraction (GIXD) experiments on the multilayer membrane formed in an environment with controlled humidity. The structural reorganization of lipid molecules in presence of violacein can be utilized to provide a detailed mechanism of the interaction of this molecule with cellular membrane.

Present and Future Perspectives on Therapeutic Options for Carbapenemase-Producing Enterobacterales Infections

Carbapenem-resistant Enterobacterales (CRE) are included in the list of the most threatening antibiotic resistance microorganisms, being responsible for often insurmountable therapeutic issues, especially in hospitalized patients and immunocompromised individuals and patients in intensive care units. The enzymatic resistance to carbapenems is encoded by different β-lactamases belonging to A, B or D Ambler class. Besides compromising the activity of last-resort antibiotics, CRE have spread from the clinical to the environmental sectors, in all geographic regions. The purpose of this review is to present present and future perspectives on CRE-associated infections treatment.

Computational analysis of the effect of [Tea][Ms] and [Tea][H2PO4] ionic liquids on the structure and stability of Aβ(17-42) amyloid fibrils

Experimental studies have reported the possibility of affecting the growth/dissolution of amyloid fibres by the addition of organic salts of the room-temperature ionic-liquid family, raising the tantalizing prospect of controlling these processes under physiological conditions. The effect of [Tea][Ms] and [Tea][H₂PO₄] at various concentrations on the structure and stability of a simple model of Aβ42 fibrils has been investigated by computational means. Free energy computations show that both [Tea][Ms] and [Tea][H₂PO₄] decrease the stability of fibrils with respect to isolated peptides in solution, and the effect is significantly stronger for [Tea][Ms]. The secondary structure of fibrils is not much affected, but single peptides in solution show a marked decrease in their β-strand character and an increase in α-propensity, again especially for [Tea][Ms]. These observations, consistent with the experimental picture, can be traced to two primary effects, i.e., the difference in the ionicity of the [Tea][Ms] and [Tea][H₂PO₄] water solutions and the remarkable affinity of peptides for [Ms]^- anions, due to the multiplicity of H-bonds.

Order-disorder in room-temperature ionic liquids probed via methyl quantum tunneling

Room-temperature ionic liquids are promising candidates for applications ranging from electrolytes for energy storage devices to lubricants for food and cellulose processing to compounds for pharmaceutics, biotransformation, and biopreservation. Due to the ion complexity, many room-temperature ionic liquids readily form amorphous phases upon cooling, even at modest rates. Here, we investigate two commonly studied imidazolium-based room-temperature ionic liquids, 1-ethyl-3-methylimidazolium tetrafluoroborate and 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, as well as their mixtures, to demonstrate how the complex interplay between the crystalline and amorphous phases is affected by the processing conditions, such as thermal history, liquid mixing, and applied pressure. We show that quantum tunneling in the cation methyl groups, measured by high-resolution inelastic neutron scattering, can be used to probe the order-disorder in room-temperature ionic liquids (crystalline vs amorphous state) that develops as a result of variable processing conditions.

Thermodynamics and structure of model bio-membrane of liver lipids in presence of imidazolium-based ionic liquids

Ionic liquids (ILs) are the attractions of researchers today due to their vast area of potential applications. For biomedical uses, it becomes essential to understand their interactions with cellular membrane. Here, the membrane is mimicked with lipid bilayer and monolayer composed of liver lipids extract. Three archetypal imidazolium based ILs, 1-decyl-3-methylimidazolium tetrafluoroborate ([DMIM][BF4] or [C10MIM][BF4]), 1-octyl-3-methylimidazolium tetrafluoroborate, ([OMIM][BF4] or [C8MIM][BF4]) and 1-ethyl-3-methylimidazolium tetrafluoroborate ([EMIM][BF4] or [C2MIM][BF4]) having different alkyl chain lengths are used in the present study. The isothermal titration calorimetry (ITC) measurements showed that [DMIM][BF4] interacts strongest with the liver lipid membrane compared to other two ILs which have relatively shorter alkyl chain length. The low values of stoichiometry ratio of ILs indicates that ILs penetrate within the core of the lipid bilayer. The interaction of ILs with the liver lipid membrane is found to be mainly driven by entropy which could be due to the change in the structure of the lipid membrane at local or global scales. Dynamic light scattering (DLS) measurements indicate that there are no changes in the size of vesicles due to addition of [DMIM][BF4] indicating stability of the vesicles. On the other hand, x-ray reflectivity (XRR) measurements showed a concentration dependent change in the monolayer structure. At low concentration of the IL, the monolayer thickness decreases, exhibiting an increase in the electron density of the layer. However, at higher concentrations, the monolayer thickness increases proving a concentration dependent effects of the IL on the arrangement of the molecules.

Ionic Liquid-Induced Phase-Separated Domains in Lipid Multilayers Probed by X-ray Scattering Studies

A cellular membrane, primarily a lipid bilayer, surrounds the internal components of a biological cell from the external components. This self-assembled bilayer is known to be perturbed by ionic liquids (ILs) causing malfunctioning of a cellular organism. In the present study, surface-sensitive X-ray scattering techniques have been employed to understand this structural perturbation in a lipid multilayer system formed by a zwitterionic phospholipid, 1,2-dipalmitoyl-sn-glycero-3-phosphocholine. The ammonium and phosphonium-based ILs with methanesulfonate anions are observed to induce phase-separated domains in the plane of a bilayer. The lamellar X-ray diffraction peaks suggest these domains to correlate across the bilayers in a smectic liquid crystalline phase. This induced IL-rich lamellar phase has a very low lamellar repeat distance, suggesting the formation of an interdigitated bilayer. The IL-poor phase closely related to the pristine lipid phase shows a decrement in the in-plane chain lattice parameters with a reduced tilt angle. The ammonium and phosphonium-based ILs with a relatively bulky anion, p-toluenemethanesulfonate, have shown a similar effect.

Biofilm control by ionic liquids

Ionic liquids (ILs) are remarkable chemical compounds with applications in many areas of modern science. They are increasingly recognized as promising compounds to fight microorganisms in both planktonic and biofilm states, contributing to reinvent the antimicrobial pipeline. Biofilm-related infections are particularly challenging given that the scientific community has not yet identified a reliable control strategy. Understanding of the action of ILs in biofilm control is is still in a very early stage. However, given the highly tunable nature and exceptional properties of ILs, they are excellent candidates for biofilm control. Here, we review the major advances in, and challenges tothe use of ILs for effective biofilm control.

New Functionalized Ionic Liquids Based on POSS for the Detection of Fe3+ Ion

This study reports a novel series of imidazolium ionic liquids (ILs) based on polyhedral oligomeric silsesquioxanes (POSS) towards effective detection of metal ions, especially Fe3+ ion. 1H, 13C, 29Si NMR, high resolution mass spectra (HRMS) and Fourier transform infrared spectra (FTIR) were applied to confirm the structures of the ILs based on POSS (ILs-POSS). The three ILs-POSS were synthesized via a green chemistry approach-a thiol-ene "click" reaction without metal ions as catalysts. Furthermore, the spherical vesicle structures of the ILs-POSS were observed and caused by self-assembly behaviors. Through comprehensive characterizations, these ILs-POSS have performed excellent thermal stabilities and low glass transition temperatures. In addition, we found it very meaningful that the limits of detection (LODs) of the three ILs-POSS for the detection of the Fe3+ ion were 7.91 × 10-8 M, 1.2 × 10-7 M, and 1.2 × 10-7 M, respectively. These data illustrate that these ILs-POSS have great potential for the detection of the Fe3+ ion. In conclusion, this study not only prepared novel ILs-POSS, but also provided new materials as fluorescent sensors in the detection of Fe3+.

The transition from salt-in-water to water-in-salt nanostructures in water solutions of organic ionic liquids relevant for biological applications

Computer simulations show how nano-structural motifs in organic salts/water solutions change with salt content increasing from dilute to highly concentrated.

Surface Active Ionic Liquids Based Coatings as Subaerial Anti-Biofilms for Stone Built Cultural Heritage

New surface active ionic liquids (SAILs), based on cholinium cations and dodecylbenzenesulfonate as anion, have been synthesized and their potential application as antimicrobial colonization agents on cultural heritage (CH)stone materials investigated. The biocidal activity and antifouling capabilities were, preliminarily, evaluated by a screening on pure Gram (+) and Gram (−) bacteria strain cultures, yeasts, hyphomycetes and single-celled algae. Tests on stone materials (marble and tufa) vs. a stabilized community, constituted by a mixture of microbial strains, revealed that some SAILs display both antimicrobial and preventive antibiofilm action against new colonization. Analogous tests have been performed on the cholinium@halide precursors.

An Imidazolium-Based Lipid Analogue as a Gene Transfer Agent

A dicationic imidazolium salt is described and investigated towards its application for gene transfer. The polar head group and the long alkyl chains in the backbone contribute to a lipid-like behavior, while an alkyl ammonium group provides the ability for crucial electrostatic interaction for the transfection process. Detailed biophysical studies regarding its impact on biological membrane models and the propensity of vesicle fusion are presented. Fluorescence spectroscopy, atomic force microscopy and confocal fluorescence microscopy show that the imidazolium salt leads to negligible changes in lipid packing, while displaying distinct vesicle fusion properties. Cell culture experiments reveal that mixed liposomes containing the novel imidazolium salt can serve as plasmid DNA delivery vehicles. In contrast, a structurally similar imidazolium salt without a second positive charge showed no ability to support DNA transfection into cultured cells. Thus, we introduce a novel and variable structural motif for cationic lipids, expanding the field of lipofection agents.

Mechanisms of action of ionic liquids on living cells: the state of the art

Ionic liquids (ILs) are a relatively new class of organic electrolytes composed of an organic cation and either an organic or inorganic anion, whose melting temperature falls around room-temperature. In the last 20 years, the toxicity of ILs towards cells and micro-organisms has been heavily investigated with the main aim to assess the risks associated with their potential use in (industrial) applications, and to develop strategies to design greener ILs. Toxicity, however, is synonym with affinity, and this has stimulated, in turn, a series of biophysical and chemical-physical investigations as well as few biochemical studies focused on the mechanisms of action (MoAs) of ILs, key step in the development of applications in bio-nanomedicine and bio-nanotechnology. This review has the intent to present an overview of the state of the art of the MoAs of ILs, which have been the focus of a limited number of studies but still sufficient enough to provide a first glimpse on the subject. The overall picture that emerges is quite intriguing and shows that ILs interact with cells in a variety of different mechanisms, including alteration of lipid distribution and cell membrane viscoelasticity, disruption of cell and nuclear membranes, mitochondrial permeabilization and dysfunction, generation of reactive oxygen species, chloroplast damage (in plants), alteration of transmembrane and cytoplasmatic proteins/enzyme functions, alteration of signaling pathways, and DNA fragmentation. Together with our earlier review work on the biophysics and chemical-physics of IL-cell membrane interactions (Biophys. Rev. 9:309, 2017), we hope that the present review, focused instead on the biochemical aspects, will stimulate a series of new investigations and discoveries in the still new and interdisciplinary field of "ILs, biomolecules, and cells."

Present and Future Perspectives for Biocides and Antifouling Products for Stone-Built Cultural Heritage: Ionic Liquids as a Challenging Alternative

This review offers an overview of the most recent research activities on counteracting the biodeterioration process of stone monuments, underlining all those aspects regarding eventual procedural drawbacks and compliance with sustainable criteria. For this purpose, the definition of “green conservation of cultural heritage” has been proposed. Its basics have been utilized in the text to highlight the issues arising from the most common conservative procedures as well as guidelines for the development of innovative technologies. The review then deals with the most innovative antimicrobial approaches, among which nano- and bio-technologies play a main role. Ionic liquids are a special class of salts, which can be prepared by applying Safe by Design concepts, to meet the Green Conservation criteria.

From protein and its hydration water dynamics to controlling mechano-elasticity of cellular lipid membranes and cell migration via ionic liquids

In this invited Commentary, as requested, I will walk the reader through my research path starting from my first works on proteins and their hydration water dynamics to my most recent activity on the use of ionic liquids (ILs) as molecular handles to control and manipulate cell membrane mechano-elasticity and cell migration. In doing so I will comment on my research activity on polymers, proteins, natural bioprotectants, phospholipid bilayers, amyloids and cells, which I have carried out by combining several different experimental and computational approaches including neutron scattering, atomic force microscopy, classical molecular dynamics and ab initio calculations, used in tandem with several biological assays and a palette of complementary techniques ranging from calorimetry to static and dynamic light scattering. In parallel to this biophysical/chemical-physical core activity, a smaller portion of my interest and effort has been-I may say always-dedicated to the development of a new neutron scattering method/spectroscopy for dynamics based on "elastic" scattering. I will comment on this instrumental side of my research as well and show its relationship with the biophysical core of my activity. The overall picture that emerges is, from my personal prospective, of a coherent 13-year research path based on curiosity and a problem-solving approach, in which the fundamental importance of inter- and trans-disciplinary approaches and collaborations is emerging on the way, forecasting a prosper and intriguing future for physics in biology and in nanomedicine and bionanotechnology applications.

Sub-Toxic Concentrations of Ionic Liquids Enhance Cell Migration by Reducing the Elasticity of the Cellular Lipid Membrane

Cell migration is a universal and crucial mechanism for life. It is required in a series of physiological processes, in wound repair and immune response and is involved in several pathological conditions, including cancer and virus dissemination. Among the several biochemical and biophysical routes, changing cell membrane elasticity holds the promise to be a universal strategy to alter cell mobility. Due to their affinity with cell membranes, ionic liquids (ILs) may play an important role. This work focuses on the effect of subtoxic amounts of imidazolium-ILs on the migration of the model cancer cell line MDA-MB-231. Here we show that ILs are able to enhance cell mobility by reducing the elasticity of the cellular lipid membrane, and that both mobility and elasticity can be tuned by IL-concentration and IL-cation chain length. This biochemical-physical mechanism is potentially valid for all mammalian cells, and its impact in bionanomedicine and bionanotechnology is discussed.

Morphological and Interaction Characteristics of Surface-Active Ionic Liquids and Palmitic Acid in Mixed Monolayers

A series of water soluble, surface-active ionic liquids (SAILs), namely, 1-alkyl-3-methyl imidazolium chlorides ([C_n -mim]Cl) and their mixtures with palmitic acid (PA) are investigated in Langmuir monolayers and Langmuir-Blodgett films. It is inferred from the surface pressure-area isotherms that C₁₆ -mim-IL mixes non-ideally with PA and stabilizes the binary mixed films. In addition, the residence of mim-IL at the water surface is enhanced as a function of the increasing alkyl side chain length. Generally, the compressional moduli values decrease upon increasing the content of the mim-ILs over a wide range of compositions. Furthermore, film relaxation measurements indicate that the IL component is selectively excluded from the mixed films upon achieving a certain target pressure. Brewster angle microscope images demonstrate minimal changes on the PA domains in the presence of either C₄ - and C₈ -mim-ILs, whereas presence of the hexadecyl counterpart results in the formation of condensed sheets. Atomic force microscopy imaging of deposited films show the formation of propeller-like aggregates when C₈ - or C₁₆ -mim-IL is present in the mixed films.

Insight into the structure-antibacterial activity of amino cation-based and acetate anion-based ionic liquids from computational interactions with the POPC phospholipid bilayer

Investigations relevant to ionic liquids (ILs) as antibacterial agents have drawn considerable attention. However, the high cost and potential toxicity of ILs have severely limited their extensive applications, which has motivated researchers to design inexpensive and health-benign ILs. In this work, the interactions between the hydrated zwitterionic phospholipid (POPC) bilayer and a series of hypothetical amino cation-based and acetate anion-based ILs with different counterparts were investigated using molecular dynamics (MD) simulations to predict their antibacterial abilities. The cations of the ILs were found to insert into the lipid bilayer spontaneously, especially amino cations. Reorientation of the inserted imidazolium-based cations was observed, while the inserted amino cations showed no obvious reorientation phenomena, probably because of the strong charge interactions between the positive NH₃ groups of the amino cation and the negative PO₄ groups of the lipid bilayer. Due to their strong affinity with water, acetate-based anions disperse better in water solution, which weakens the insertion of the cations into the lipid bilayer to some extent. The structure and dynamic properties of the lipid bilayer, such as electrostatic potential, local ordering, area per lipid, volume per lipid, bilayer thickness, and lateral diffusion, are significantly influenced by the insertion of the cations, which results in disorder of the lipid bilayer and further disruption of the activity of the cell membrane. The insights into the relationship between the structures of ILs and their antibacterial activity in this work will provide a good reference for the screening and design of less expensive, safer, and greener IL candidates as antibacterial agents.

Surface Activities of a Lipid Analogue Room-Temperature Ionic Liquid and Its Effects on Phospholipid Membrane

There are great efforts of synthesizing imidazolium-based ionic liquids (ILs) for developing new antibiotics as these molecules have shown strong antibacterial activities. Compared to a single-hydrocarbon-chained IL, the lipid analogues (LAs) with two chains are more effective. In the present study, the LA molecule ^MeIm(COOH)^Me(Oleylamine)Iodide has been synthesized and its surface activities along with the effectiveness in restructuring of a model cellular membrane have been quantified. The molecule is found to be highly surface active as estimated from the area-pressure isotherm of a monolayer of the molecules formed at the air-water interface. The X-ray reflectivity (XRR) studies of a monolayer dip-coated on a hydrophilic substrate have shown the structural properties of the layer which resembles to those of unsaturated phospholipids. The LA molecules are observed to fluidize a phospholipid bilayer formed by the saturated lipid 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC). At a lower surface pressure, the lipid monolayer of DPPC has exhibited a thickening effect at a low concentration of added LA and a thinning effect at higher concentration. However, at a high surface pressure of the monolayer, the thickness is found to decrease monotonically. The in-plane pressure-dependent interaction of LA molecules with model cellular membrane and the corresponding perturbation in the structure and physical properties of the membrane may be linked to the strong lysing effect of these types of molecules.

Dynamic Landscape in Self-Assembled Surfactant Aggregates

A process in which a disordered system of pre-existing molecules generates an organized structure through specific, local interactions among the molecules themselves is termed molecular self-assembly. Micelles, microemulsions, and vesicles are examples of such self-assembled systems where amphiphilic molecules are involved. As the functional properties of these systems (such as wetting and emulsification, release of solubilized drugs, etc.) are dictated by the dynamic behavior of the surfactants at the molecular level, it is of immense interest to investigate these systems for the same. The dynamics in soft matter systems is quite complex, involving different time and length scales. We used a combination of neutron scattering and molecular dynamics simulation studies in probing the dynamic landscape in various self-assembled surfactant aggregates. Neutron scattering experiments were carried out using several spectrometers covering a wide dynamic range to probe motions on different time scales. The interaction between the surfactants can be varied by changing the molecular architecture, counterion concentration, temperature, and so forth. It is important to study the effect of these parameters on the dynamics of surfactants in these aggregates. We have carried out experiments on various ionic (anionic as well as cationic) micelles with varied counterion concentrations, vesicles, and lipid bilayers to unravel the complex dynamic features present in these systems. In this feature article, we will discuss some important results of our recent work on dynamics in these self-assembled surfactant aggregates.

Surface of Half-Neutralized Diamine Triflate Ionic Liquids. A Molecular Dynamics Study of Structure, Thermodynamics, and Kinetics of Water Absorption and Evaporation

Surface properties of room temperature ionic liquids (RTILs) consisting of half neutralized diamine cations (H₂N-(CH₂)_n-NH₃⁺, n = 2, 4) and triflate anions have been investigated by molecular dynamics simulations, based on an empirical atomistic force field. Planar slabs periodically repeated in 2D have been considered, and the temperature range 260 ≤ T ≤ 360 K has been covered, extending from below the melting and glass point to the equilibrium liquid range of the diamine compounds under investigation. Addition of water at 1% weight concentration allowed us to investigate the kinetics of water absorption through the RTIL surface, and to characterize the structural and dynamical properties of subsurface water. Animations of the simulation trajectory highlight the quick absorption of water molecules, progressing downhill in free energy and taking place without apparent intermediate kinetic stages. To verify and quantify these observations, a variant of the umbrella sampling algorithm has been applied to compute the variation of excess free energy upon displacing a water molecule along the normal to the surface, from the center of the slab to the vapor phase. The results provide a comprehensive picture of the thermodynamic properties underlying the kinetics of water absorption and evaporation through the surface, and they also provide the ratio of the equilibrium density of water in the vapor and liquid phase at the average concentration considered by simulations. A variety of properties such as the surface energy, the 90-10% width of the profile, the layering of different species at the interface, and the electrostatic double layer at the surface are computed and discussed, focusing on the effect of water contamination on all of them.

Surface Plasmon Resonance for Biomarker Detection: Advances in Non-invasive Cancer Diagnosis

Biomarker-based cancer analysis has great potential to lead to a better understanding of disease at the molecular level and to improve early diagnosis and monitoring. Unlike conventional tissue biopsy, liquid biopsy allows the detection of a large variety of circulating biomarkers, such as microRNA (miRNA), exosomes, circulating tumor DNA (ctDNA), circulating tumor cells (CTCs), and proteins, in an easily accessible and minimally invasive way. In this review, we describe and evaluate the relevance and applicability of surface plasmon resonance (SPR) and localized SPR (LSPR)-based platforms for the detection of different classes of cancer biomarkers in liquid biopsy samples. Firstly, we critically discuss unsolved problems and issues in capturing and analyzing biomarkers. Secondly, we highlight current challenges which need to be resolved in applying SPR biosensors into clinical practice. Then, we mainly focus on applications of SPR-based platforms that process a patient sample aiming to detect and quantify biomarkers as a minimally invasive liquid biopsy tool for cancer patients appearing over the last 5 years. Finally, we describe the analytical performances of selected SPR biosensor assays and their significant advantages in terms of high sensitivity and specificity as well as accuracy and workflow simplicity.

Nonfunctionalized Cation of an Ionic Liquid as a Ligand in the Synthesis of a New Coordination Compound and Assessment of Its Biological Activity

Literature evidences reveal the affinity of ionic liquids for biomembranes that they are readily absorbed into the cell, resulting in a variety of biological effects, including broad antibacterial potential and anticancer activity. Recent research directions considered the ions of this class of compounds as a new choice of ligands in the synthesis of transition metal complexes for various applications. Based on this, the present work reports the synthesis, structural characterization, and in vitro antibacterial activities of a tetrahedral hexacationic Co(II) complex formed by coordinating with the cation of an ionic liquid, N-butyl-4,4-bipyridinium bis(trifluoromethylsulfonyl)amide ([C₄Bip][Tf₂N]). It has been demonstrated by the isolation and characterization of tetrakis-(N-butyl-4,4′-bipyridinium)cobalt(II)dichloride-tetrakis-(bis(trifluoromethylsulfonyl)amide, ([(C₄Bip)₄Co]Cl₂(Tf₂N)₄). The ligand and complex are characterized spectroscopically (¹H, ¹³C, and ¹⁹F NMR, ESI MS, ICP OES), and by CHNS elemental analysis, halide estimation, and conductivity studies. The antibacterial activities of the compounds against two bacteria, Klebsiella pneumoniae (K. pneumoniae) and Staphylococcus aureus (S. aureus), are screened using the agar well-diffusion method and were compared with a reference (gentamicin). The metal complex demonstrated better inhibition than the ionic liquid and the reference.

Self-assembled systems based on novel hydroxyethylated imidazolium-containing amphiphiles: Interaction with DNA decamer, protein and lipid

The study on aggregation capacity of novel imidazolium-containing amphiphiles of 1-(2-hydroxyethyl)alkylimidazolium bromide series and their interaction with bio-objects (DNA decamer, bovine serum albumin, phospholipid) was performed. It was revealed that introduction of hydroxyethyl moiety into the surfactant molecule resulted in 1.5-2-fold decrease of critical micelle concentration. These modified amphiphiles quantitatively bind DNA decamer due to intercalation and hydrophobic interactions with lipoplex formation. The evaluation of membranotropic properties of these surfactants exhibited that initiation of disordering and compression of the model cell wall consisting of dipalmitoyl phosphocholine (regulation of permeability for various compounds) could be achieved by variation of the length of hydrophobic tail of imidazolium-containing amphiphiles. Transition from individual surfactants solutions to their mixtures with protein (bovine serum albumin) is accompanied by 8-fold decrease of aggregation thresholds and characterized by the presence of two critical points. The binding of components of surfactant/BSA binary systems took place through tryptophan amino acid residue of peptide macromolecule.

Effect of Imidazolium-Based Ionic Liquids on the Structure and Phase Behavior of Palmitoyl-oleoyl-phosphatidylethanolamine

Among various applications, ionic liquids (ILs) have been used as antimicrobial agents in laboratories, possibly through induction of the leakage of bacteria. A molecular-level understanding of the mechanism that describes how ILs enhance the permeation of membranes is still lacking. In this study, the effects of imidazolium-based ILs with different alky chain lengths on the structure and phase behavior of 1-palmitoyl-2-oleoyl-phosphatidylethanolamine (POPE), which is a representative bacteria-membrane-rich lipid, have been investigated. By employing differential scanning calorimetry and synchrotron small- and wide-angle X-ray scattering techniques, we found that ILs with longer alkyl chains influenced the phase behavior more effectively, and lower IL concentrations are needed to induce phase separation for both lamellar liquid crystalline phase and nonlamellar inverted hexagonal phase of POPE. Interestingly, the IL with an alkyl chain of 12 carbon atoms ([C₁₂mim]Cl) shows a difference. It exhibits a stronger disturbing effect on the POPE bilayer structure than [C₁₆mim]Cl, indicating that the ability of ILs to influence the membrane structures is dependent not only on the alkyl chain length of ILs, but also on the degree of matching of the alkyl chain lengths of ILs and lipids. The new lamellar and nonlamellar structures induced by ILs both have smaller repeat distances than that of pure POPE, implying thinner membrane structures. Data of the fluorescence-based vesicle dye leakage assay are consistent with these results, particularly the defects caused by IL-induced phase separation can enhance the membrane permeability markedly. The present work may shed light on our understanding of the antimicrobial mechanism of ILs.