Ionic liquids revolutionizing biomedicine: recent advances and emerging opportunities

CO2-switchable self-healing of ionic liquids-based hydrogels

High-performance soft materials with stimulus-responsive and self-healing properties have received a lot of attention in modern environmental and energy technologies. However, it was difficult to construct supramolecular hydrogels integrating different functionalities. In this work, we reported a novel class of supramolecular hydrogels made of ionic liquids (ILs) with CO2-responsive and self-healing properties. These ILs were found to form hydrogels with H2O. Upon bubbling with CO2, the transparent and stable IL-based hydrogels transformed into sols, which returned to their initial gel state after bubbling with N2 at 65°C. The reversible gel-sol phase transformation behavior was demonstrated by rheological, polarizing, scanning and cryogenic transmission electron microscopy measurements. Spectroscopic studies indicated that the mechanism of gel-sol transition was attributed to reversible reaction between the anions of the ILs and CO2 in the hydrogel, which destroyed the hydrogen bonding between the anions and water. Self-healing ability of the hydrogels was confirmed by rheological measurements. The self-healing mechanism was ascribed to the disruption and reconstruction of hydrogen bonds in IL-based hydrogels using temperature-dependent Fourier transform infrared spectroscopy. The CO2-responsive and self-healing ability make these novel hydrogels attractive in smart soft materials.

Property-Driven Design of Thermally Robust Organophosphorus Ionic Liquids for High-Temperature Applications

We have developed a class of organophosphorus ionic materials featuring tetraarylphosphonium cations with extended π-conjugated systems via a facile and modular approach. These mesothermal ionic liquids demonstrate exceptional thermal stability, maintaining their structural integrity when heated at 300 °C for 96 h under aerobic conditions without decomposition. Their negligible volatility and strategic exclusion of aliphatic C-(sp3)-H bonds from our molecular architecture yields materials with outstanding resistance to thermo-oxidative degradation. Our rigorous investigation using comprehensive single-crystal X-ray diffraction and thermodynamic studies validates the design principles while providing detailed insights into the structure-property relationships governing their thermal stability, melting behavior, and photophysical properties. Our studies reveal a systematic correlation between the nature of the cations and the resulting phase transitions. Additionally, detailed photophysical characterization demonstrates that select derivatives exhibit strong fluorescence with quantum yields up to 42%, suggesting potential applications in optoelectronic devices. These thermally robust organic-ion materials with tunable properties have potential applications ranging from thermally demanding environments (thermoresponsive materials, advanced nuclear reactor coolants, and thermal energy storage) to optoelectronic devices that capitalize on their unique photoluminescent characters.

Ionic liquids in C-H activation: synthesis and functionalization of heterocycles and carbocycles

This review illustrates various roles played by ionic liquids in organic transformations, such as solvents, additives, promoters, electrolytes and catalysts for the synthesis and functionalization of heterocycles and carbocycles through C-H activation reactions. Ionic liquids offer several advantages such as high stability, intrinsic conductivity, non-volatility, and recyclability, making them appealing alternatives to traditional organic solvents in sustainable organic synthesis. Their unique properties enhance reaction performance, as seen with recyclable [EMIM]BF4 in quinazolinone synthesis and [TMG][CF3COO] in amide production, direct diarylation of 6,7-benzindoles, regioselective reactions with aryl iodides, catalytic cyclopropanation with tetrabutylammonium acetate (TBAA), and propargylamine synthesis via A3 coupling reactions. The use of functionalized ionic liquids like [Bmim]PF6 with phosphine-ligated Pd(II) enhances product isolation, facilitates reactions under mild conditions, and promotes reusability, contributing to environmentally friendly pathways. Thus, this review highlights various ionic liquids used in different reactions, emphasizing their benefits in improving yields, solubility, and product separation in catalytic processes.

Colloidal ionogels: Controlled assembly and self-propulsion upon tunable swelling

Active colloids driven out of thermal equilibrium serve as building blocks for smart materials with tunable structures and functions. Using chemical energy to drive colloids is advantageous but requires precise control over chemical release. To address this, we developed colloidal ionogels-polymer microspheres infused with ionic liquids-that show controlled assembly and self-propulsion upon tunable swelling. For example, we synthesized microspheres of polymethylmethacrylate loaded with ionic liquid [Bmim][PF6], which were released from the colloidal ionogel upon swelling in alcohol-water mixtures and dissociated into cations and anions of different diffusivities. The resulting electric field leads to four types of pair-wise colloidal interactions via ionic diffusiophoresis and diffusioosmosis, giving rise to four types of self-assembled superstructures. These interactions were precisely modulated by altering the swelling conditions and the ionic liquids used. Additionally, partially blocking the ionogel's surface induces anisotropic swelling and asymmetric ion release, turning the colloidal ionogel into a self-propelled Janus colloidal motor powered by ionic self-diffusiophoresis, reaching speeds of several µm/s and lasting about 100 s. These findings indicate that colloidal ionogels are smart colloidal building blocks with highly tunable pair-wise interactions, self-assembled structures, and self-propulsion, offering potential applications in biomedical sensing, environmental monitoring, and photonics.

Functionalized carbon dots with guanidine salt ionic liquid regulate oxidative damage and amyloid aggregation

An imbalance in the brain microenvironment, involving oxidative stress and β-amyloid (Aβ) accumulation, is thought to be one of the primary characteristics of early Alzheimer's disease (AD). To address the intricate pathophysiology of AD, therapeutic approaches that can concurrently control several diseases in the AD microenvironment are desperately needed. This study created a guanidine salt ionic liquid functionalized carbon dots (CDs@TGM-IL) to mitigate Aβ aggregation-induced cytotoxicity and scavenge reactive oxygen species (ROS) simultaneously. In vitro studies have shown that CDs@TGM-IL can effectively inhibit Aβ42 protein aggregation, disaggregate mature Aβ42 fibrils, and effectively remove ROS. In vivo studies have found that CDs@TGM-IL can cross the blood-brain barrier (BBB) and improve cognitive performance in AD mice. Just as importantly, CDs@TGM-IL has been shown to have unparalleled biocompatibility. This means that CDs@TGM-IL is expected to be a possible treatment for AD.

Potential Antioxidant and Anti-inflammatory Effects of Astaxanthin Ionic Liquid Liposomes

Astaxanthin is an antioxidant with extremely high antioxidant activity. However, the stability and solubility of free astaxanthin are poor. Therefore, we prepared astaxanthin-betaine (ASTA-Bet) ionic liquid liposomes through a combination of theoretical calculations and experimental research and studied their physicochemical properties and biological effects. This liposome has good stability and skin permeability. The cumulative permeability of the ASTA-Bet ionic liquid liposome is 22.95 times that of free astaxanthin and 2.41 times that of the ASTA-Bet ionic liquid. The particle size of astaxanthin liposomes was 117.2 nm, and the particle size did not change significantly after 28 days of storage, indicating good stability. Compared with free astaxanthin, the ASTA-Bet ionic liquid liposome has good antioxidant activity and can exert antioxidant and anti-inflammatory effects by regulating the TGF-β1/smad2/smad3 pathway damaged by ultraviolet radiation, which may contribute to the resistance to ultraviolet radiation damage. Therefore, it can be used as a raw material to develop cosmetics with antiaging and anti-inflammatory functions.

Evaluation of 1-vinyl-3-alkyl imidazolium-based ionic liquid monomers towards antibacterial activity: An in-silico & in-vitro study

In this study 1-vinyl-3-alkyl imidazolium-based ionic liquid monomers (ILs) with different alkyl chain lengths {R = hexyl (A), octyl (B) and decyl (C)} have been synthesized for antibacterial applications. The prepared ILs have been characterized using UV, FT-IR and NMR spectroscopy. The antibacterial activities of the synthesized ILs against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) have been examined by measuring their minimal inhibitory concentrations (MICs) and minimum bactericidal concentrations (MBCs). The results exhibit that these ILs have admirable antibacterial activities with MIC values range from < 1.2 to 12.2 μM for S. aureus and < 2.4 to 12.2 μM for E. coli. A notable dependence of antibacterial and antibiofilm efficacy on the alkyl chain length (ILC> ILB > ILA) has been observed. From in-silico evaluation, the binding energies of β-lactamase protein of S. aureus (PDB ID: 1GHP) are found to be -4.4, -4.6, -4.7 kcal/mol for IL A, IL B, and IL C. For dihydrofolate reductase (DHFR) of S. aureus and E. coli the binding energies -4.6, -4.5, -5.3 kcal/mol and -5.3, -5.4, -5.6 kcal/mol have been noted for IL A, IL B, and IL C respectively. MD simulations (100 ns) have been performed to predict the stability and understand the binding mechanism of the docked complexes.

Adhesive micro-liquid for efficient removal of bacterial biofilm infection

Bacteria are common infectious pathogens that can cause invasive and potentially life-threatening infections. Ionic liquids have emerged as a novel class of alternatives to antibiotics, however their inherent hydrophobicity and immiscible in water exhibits poor adhesion to bacteria and diminishes its utilization and bioavailability for infection control. Herein, an adhesive metal phenolic encapsulated ionic liquid choline and geranate (CAGE@MPN) microcapsules is designed to address the aforementioned challenges and remove bacterial biofilm infections. The CAGE@MPN microcapsules are prepared through self-assembly of quercetin and ferrous ions on the interface of CAGE and water via metal-phenolic coordination. The MPN interface can stabilize the micro liquid and effectively adhere to bacterial surfaces. The microcapsules can disrupt bacterial cell walls to facilitate the release of cellular contents and destruct the biofilm, thereby exerting a pronounced bactericidal effect. The in vivo bactericidal effect of CAGE@MPN microcapsules is demonstrated in a murine model of Staphylococcus aureus (S. aureus) skin infection. The proposed adhesive micro-liquid system offers a promising strategy for noninvasive and efficient removal of bacterial biofilm infection.

Unravelling the optical properties and self-assembly behavior of ciprofloxacin in ionic liquid environments: probing the role of cationic residues and counter anions

This study investigated the interaction of ciprofloxacin (CIP) with three different ionic liquids (ILs) featuring distinct cationic residues (pyrrolidinium, IL1, vs. imidazolium, IL2, with bis(trifluoromethylsulfonyl)imide as the counter anion) and counter anions bis(trifluoromethylsulfonyl)imide, IL2, vs. hexafluorophosphate, IL3, with imidazolium as the cationic residue) in an aqueous environment. A series of spectroscopic studies have been performed to elucidate the role of ILs in the optical properties as well as aggregation behavior of CIP. The fluorescence quenching experiment indicated that the IL with a pyrrolidinium residue showed stronger binding with CIP, while bis(trifluoromethylsulfonyl)imide was the preferred anion. These quenching effects might be attributed to complex formation mediated by charge-pair and cation-π interactions, along with hydrogen bonding. The Stern-Volmer analysis confirmed a static quenching mechanism, with binding constants (Kb) reflecting the stronger affinity of IL1 due to the hydrophobic butyl group and the flexible pyrrolidinium cation, resulting in the formation of larger aggregates. In contrast, the imidazolium residue in IL2 facilitated π-π and hydrogen-bond interactions, disrupting CIP aggregation and resulting in smaller clusters. The polarizable nature of bis(trifluoromethylsulfonyl)imide along with its hydrogen bond-accepting ability enabled stronger binding of ILs containing this anion to CIP compared to hexafluorophosphate-containing ILs. Further studies indicated that pH 6 is optimum for CIP-IL interactions, where CIP remained in its zwitterionic form. Increased temperature and ionic strength diminished the quenching efficiency, consistent with the reduced stability of CIP-IL complexes under such conditions.

Metal Oxide Nanoparticles Synthesized in Ionic Liquids: Characterization and Photodegradation of Methyl Orange

Dye residues from the textile industry significantly contribute to water pollution, necessitating effective wastewater treatment methods. This study reports the successful synthesis of zinc oxide (ZnO) nanoparticles using various ionic liquids (ILs), [BMIM]-BF4, [BMIM]-PF6, and [BMIM]-Cl, as mediators. The synthesized nanomaterials were characterized using various techniques, including X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), and photoluminescence (PL) spectroscopy. Their photocatalytic activity in degrading methyl orange (MO) dye under UV-vis and sunlight irradiation was investigated. The results demonstrated that ILs significantly influenced the structural and optical properties of ZnO, resulting in smaller crystallite sizes, modified morphologies, and reduced band gap energies compared to unmodified ZnO. The ZnO-[BMIM]-BF4 (1%) exhibited superior photocatalytic efficiency, achieving complete MO degradation within 30 min under UV-vis irradiation, attributed to its enhanced light absorption and reduced electron-hole recombination. The ZnO-BMIM-PF6 (1%) demonstrated exceptional stability, maintaining high degradation efficiency over multiple cycles. These findings highlight the potential of IL-mediated synthesis in tailoring ZnO nanomaterials for efficient photocatalytic degradation of organic pollutants, offering a promising approach for wastewater treatment.

Preparation of dual supramolecular EGCG-carboxymethyl chitosan: Structure, antioxidant and anti-inflammatory properties

In the field of cosmetics, epigallocatechin gallate (EGCG) is highly valued for its multiple effects such as delaying photoaging, whitening, anti-allergy, acne removal, astringency, and moisturizing. However, due to the active chemical properties of EGCG, there are challenges in terms of stability and transdermal absorption, which limits its widespread application in cosmetics. Therefore, we utilized supramolecular modification technology to form supramolecular carboxymethyl chitosan-EGCG-trehalose (CC-EGCG) by combining EGCG with carboxymethyl chitosan and trehalose, enhancing its stability. Then, we encapsulated the supramolecular CC-EGCG with hydroxypropyl cyclodextrin to obtain a dual supramolecular CC-EGCG, which not only further enhanced the stability of the raw material and reduced its irritation to the skin but also improved skin permeability (compared with single EGCG, the dual supramolecular CC-EGCG increased by 3.51 times). The bioavailability of EGCG was significantly improved, making it play a better role in antioxidant, whitening, soothing, and oil control acne removal.

An ionic liquid-based delivery system of small interfering RNA targeting Bcl-2 for melanoma therapy

Melanoma, characterized by rapid tumour progression and a strong tendency to metastasize, poses significant challenges in clinical treatment. Given the vital role of B-cell lymphoma 2 (Bcl-2) protein overexpression in inhibiting apoptosis in tumour cells, the suppression of Bcl-2 has emerged as a promising anticancer therapy. Here, we have developed a straightforward and effective delivery system that combines small interfering RNA (siRNA) targeting Bcl-2 (siBcl-2) with ionic liquids (ILs) for treating melanoma. The unique properties of ILs including structural tunability, inherent charge, and chemical stability have garnered significant attention in the biomedical fields; however, their application in siRNA delivery remains nascent. Rather than the weak function of free siBcl-2, our delivery system (1-hexyl-3-methylimidazolium-siBcl-2, designated as C6-siBcl-2) demonstrated an outstanding capacity to improve the cellular uptake and lysosomal escape, resulting in robust apoptosis and cytotoxicity in melanoma cells. In addition to exhibiting superior gene silencing activity in vitro, such events were also evident in mice bearing melanoma tumours. In particular, this IL-based delivery system showed advantages in suppressing tumour growth, preventing metastasis, and enhancing the survival time of mice with melanoma tumours. Therefore, our study offered a novel and powerful nanoplatform that integrated ILs and RNA interference therapy, presenting new strategies for cancer treatment.

Solubilization techniques used for poorly water-soluble drugs

About 40% of approved drugs and nearly 90% of drug candidates are poorly water-soluble drugs. Low solubility reduces the drugability. Effectively improving the solubility and bioavailability of poorly water-soluble drugs is a critical issue that needs to be urgently addressed in drug development and application. This review briefly introduces the conventional solubilization techniques such as solubilizers, hydrotropes, cosolvents, prodrugs, salt modification, micronization, cyclodextrin inclusion, solid dispersions, and details the crystallization strategies, ionic liquids, and polymer-based, lipid-based, and inorganic-based carriers in improving solubility and bioavailability. Some of the most commonly used approved carrier materials for solubilization techniques are presented. Several approved poorly water-soluble drugs using solubilization techniques are summarized. Furthermore, this review summarizes the solubilization mechanism of each solubilization technique, reviews the latest research advances and challenges, and evaluates the potential for clinical translation. This review could guide the selection of a solubilization approach, dosage form, and administration route for poorly water-soluble drugs. Moreover, we discuss several promising solubilization techniques attracting increasing attention worldwide.

Polysaccharides from Lonicera japonica Thunb.: Extraction, purification, structural features and biological activities-A review

Lonicera japonica Thunb.,commonly referred to as Caprifolium japonicum (Thunb.) Dum. Cours.,is a perennial herb classified under the caprifoliaceae family. It is utilized worldwide as a medicinal plant and also serves as food source and an ornamental plant. Lonicera japonica Thunb. polysaccharides (LJP) constitute one of its primary components, demonstrating a wide range of biological activities including anti-inflammatory, antioxidant, immunomodulatory, anti-Alzheimer's, anti-diabetic, and anti-cancer effects. This paper reviews and summarizes recent research advancements on the extraction, purification, structural characteristics, and biological activities of LJP, offering a valuable foundation and up-to-date insights for the continued development and application of LJP in pharmaceutical and functional food sectors.

Design Principles and Applications of Ionic Liquids for Transdermal Drug Delivery

Ionic liquids (ILs) are salts with melting points typically <100 °C, composed of specific anions and cations. Recently, IL application has expanded into material engineering and biomedicine. Due to their unique properties, ILs have garnered significant interest in pharmacological research as solubilizers, transdermal absorption enhancers, antibacterial agents, and stabilizers of insoluble pharmaceutical active ingredients. The improvement of skin permeability by ILs is closely associated with their specific physicochemical characteristics, which are identified by their ionic composition. However, the existing literature on transdermal medication administration is insufficient in terms of a comprehensive knowledge base. This review provides a comprehensive assessment of the design principles involved in IL synthesis. Additionally, it discusses the methods utilized to assess skin permeability and provides a focused outline of IL application in transdermal drug administration.

Ionic liquid-based formulation approaches for enhanced transmucosal drug delivery

The utilization of ionic liquids (ILs) in pharmaceutical drug delivery applications has seen significant expansion in recent years, owing to their distinctive characteristics and inherent adjustability. These innovative compounds can be used to tackle challenges associated with traditional dosage forms, such as polymorphism, inadequate solubility, permeability, and efficacy in topical drug delivery systems. Here, we provide a brief classification of ILs, and their effectiveness in augmenting transmucosal drug delivery approaches by improving the solubility and permeability of active pharmaceutical ingredients (APIs) by temporary mucus modulation aiding the paracellular transport of APIs, prolonging drug retention, and, thus, aiding controlled drug release across various mucosal surfaces. We also highlight potential advances in, and future perspectives of, IL-based formulations in mucosal drug delivery.

Review of ionic liquid and ionogel-based biomaterials for advanced drug delivery

Ionic liquids (ILs) play a crucial role in the design of novel materials. The ionic nature of ILs provides numerous advantages in drug delivery, acting as a green solvent or active ingredient to enhance the solubility, permeability, and binding efficiency of drugs. They could also function as a structuring agent in the development of nano/micro particles for drug delivery, including micelles, vesicles, gels, emulsion, and more. This review summarize the ILs and IL-based gel structures with their advanced drug delivery applications. The first part of review focuses on the role of ILs in drug formulation and the applications of ILs in drug delivery. The second part of review offers a comprehensive overview of recent drug delivery applications of IL-based gel. It aims to offer new perspectives and attract more attention to open up new avenues in the biomedical applications of ILs and IL-based gels.

The Physics of Antimicrobial Activity of Ionic Liquids

The bactericidal potency of ionic liquids (ILs) is well-established, yet their precise mechanism of action remains elusive. Here, we show evidence that the bactericidal action of ILs primarily involves the permeabilization of the bacterial cell membrane. Our findings reveal that ILs exert their effects by directly interacting with the lipid bilayer and enhancing the membrane dynamics. Lateral lipid diffusion is accelerated, which in turn augments membrane permeability, ultimately leading to bacterial death. Furthermore, our results establish a significant connection: an increase in the alkyl chain length of ILs correlates with a notable enhancement in both lipid lateral diffusion and antimicrobial potency. This underscores a compelling correlation between membrane dynamics and antimicrobial effectiveness, providing valuable insights for the rational design and optimization of IL-based antimicrobial agents in healthcare applications.

A New 2-Aminospiropyrazolylammonium Cation with Possible Uses in the Topical Areas of Ionic Liquids

Based on the fact that 2-aminospiropyrazolinium compounds and structurally related azoniaspiro compounds belong, in a broad sense, to the class of ionic liquids, we have reviewed them and studied their practical applications. To search for possible uses of a new 2-aminospiropyrazolinium compounds, it is necessary to undertake a comparison with the related class of azoniaspiro compounds based on available information. The structures of the well-studied class of azoniaspiro compounds and the related but little-studied class of 2-aminospiropyrazolinium have rigid frameworks, limited conformational freedom, and a salt nature. These properties give them the ability to organize the nearby molecular space and enable the structure-forming ability of azoniaspiro compounds in the synthesis of zeolites, as well as the ability to act as phase-transfer catalysts and have selective biological effects. Additionally, these characteristics enable their ability to act as electrolytes and serve as materials for anion exchange membranes in fuel cells and water electrolyzers. Thus, the well-studied properties of azoniaspiro compounds as phase-transfer catalysts, structure-directing agents, electrolytes, and materials for membranes in power sources would encourage the study of the similar properties of 2-aminospiropyrazolinium compounds, which we have studied in relation to in vitro antitubercular, antidiabetic, and antimicrobial activities.

Bulk Nanostructure of Mixtures of Choline Arginate, Choline Lysinate, and Water

Neutron diffraction with empirical potential structure refinement was used to investigate the bulk liquid nanostructure of mixtures of choline arginate (Ch[Arg]), choline lysinate (Ch[Lys]), and water at mole ratios of 1Ch[Arg]:1Ch[Lys]:6H2O (balanced), 1Ch[Arg]:1Ch[Lys]:20H2O (balanced dilute), 3Ch[Arg]:1Ch[Lys]:12H2O (Arg- rich), and 1Ch[Arg]:3Ch[Lys]:12H2O (Lys- rich). The Arg- and Lys- anions tend not to associate due to electrostatic repulsion between charge groups and weak anion-anion attractions. This means that the local ion structures around the anions in these mixtures resemble the parent single-component systems. The bulk liquid nanostructure varies with the Arg-:Lys- ratio. In the Lys--rich mixture (1Ch[Arg]:3Ch[Lys]:12H2O), Lys- side chains cluster into a continuous apolar domain separated from a charged domain of polar groups. In the balanced mixture (1Ch[Arg]:1Ch[Lys]:6H2O), Lys- side chains form discrete apolar aggregates within a continuous polar domain of Arg-, Ch+, and water, and in the Arg--rich mixture (3Ch[Arg]:1Ch[Lys]:12H2O), the distribution of Lys- and Arg- is nearly homogeneous. Finally, in the balance dilute system (1Ch[Arg]:1Ch[Lys]:20H2O), a percolating water domain forms.

Development of Cholinium-Based API Ionic Liquids with Enhanced Drug Solubility: Biological Evaluation and Interfacial Properties

We report an efficient sustainable two-step anion exchange synthetic procedure for the preparation of choline API ionic liquids (Cho-API-ILs) that contain active pharmaceutical ingredients (APIs) as anions combined with choline-based cations. We have evaluated the in vitro cytotoxicity for the synthesized compounds using three different cells lines, namely, HEK293 (normal kidney cell line), SW480, and HCT 116 (colon carcinoma cells). The solubility of APIs and Cho-API-ILs was evaluated in water/buffer solutions and was found higher for Cho-API-ILs. Further, we have investigated the antimicrobial potential of the pure APIs, ILs, and Cho-API-ILs against clinically relevant microorganisms, and the results demonstrated the promise of Cho-API-ILs as potent antimicrobial agents to treat bacterial infections. Moreover, the aggregation and adsorption properties of the Cho-API-ILs were observed by using a surface tension technique. The aggregation behavior of these Cho-API-ILs was further supported by conductivity and pyrene probe fluorescence. The thermodynamics of aggregation for Cho-API-ILs has been assessed from the temperature dependence of surface tension. The micellar size and their stability have been studied by dynamic light scattering, transmission electron microscopy, and zeta potential. Therefore, the duality in the nature of Cho-API-ILs has been explored with the upgradation of their physical, chemical, and biopharmaceutical properties, which enhance the opportunities for advances in pharmaceutical sciences.

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.