Choline‐Geranate Deep Eutectic Solvent Improves Stability and Half‐Life of Glucagon‐Like Peptide‐1

Natural deep eutectic solvents (NADES) in drug delivery systems: Characteristics, applications, and future perspectives

Deep eutectic solvents (DESs) are a class of low-melting mixtures formed by the hydrogen-bond interactions between hydrogen bond acceptors (HBAs) and hydrogen bond donors (HBDs) in specific molar ratios. Their unique physicochemical properties enable DESs to significantly enhance drug solubility and permeability, while also serving as carriers to facilitate efficient drug delivery. A subclass of DESs, natural deep eutectic solvents (NADESs), is found in the metabolites of natural organisms, such as plants. With low toxicity and biodegradability, NADESs possess distinct advantages for applications in the pharmaceutical field.The therapeutic efficacy of drugs is often limited by imprecise release mechanisms, leading to the metabolism or degradation of a portion of the drug before it reaches the target site, thereby reducing its effectiveness. Moreover, many drugs exhibit poor solubility and stability, resulting in low efficiency during absorption and metabolism, which further diminishing their therapeutic impact. NADESs, with their excellent tunability and biocompatibility, have demonstrated great potential in drug delivery systems.This paper first provides an overview of the fundamental characteristics of NADESs, followed by a detailed summary of recent advancements and applications of NADESs across various administration routes, including transdermal, mucosal, and inhalation drug delivery. Finally, the paper explores the prospects of NADESs in novel drug delivery systems and proposes strategies for optimizing their performance to promote clinical applications.

Physicochemical and Biological Properties of Menthol and Thymol-Based Natural Deep Eutectic Solvents

Seven hydrophobic deep eutectic solvents (hDESs) were characterised to evaluate their potential applicability in different industries and their environmental impact. Standard physicochemical properties were determined, yielding polarity and density values that were slightly higher for thymol-based hDESs than menthol-based ones, whereas for viscosity, the trend was opposite. Regarding biologically relevant activities, the antioxidative capacity and antimicrobial activity of hDESs were determined. Thymol-based hDESs are more potent as potential antioxidants, especially the one with coumarin as a hydrogen bond acceptor, which had the highest Oxygen Radical Absorbance Capacity (ORAC) value. Antimicrobial activity was assessed on four bacterial strains and one yeast strain. Calculated minimal inhibitory concentrations (MICs) showed that all hDESs possess this activity, and even the antimycotic effect against C. albicans was observed. Furthermore, to ensure the safety of these solvents for human use, in vitro cytocompatibility was determined. hDESs were tested on three human cell lines (HaCaT, CaCo-2, and HeLa), with no cytotoxic effect observed up to 1000 mg L-1. Finally, the environmental impact by the phytotoxicity test and in vitro antioxidative assay on wheat was determined for three selected hDESs, which were found to be slightly toxic, with different effects on plant defence mechanisms against induced antioxidative stress. Overall, the tested terpene-based hDESs demonstrate potential as alternative solvents for various industries, including food production, cosmetics, and pharmaceuticals, with thymol-based variants exhibiting a slight advantage in relation to the parameters evaluated in this study.

Deep eutectic solvent enhances antibacterial activity of a modular lytic enzyme against Acinetobacter baumannii

In this study, we evaluated the combined effect between MLE-15, a modular lytic enzyme composed of four building blocks, and reline, a natural deep eutectic solvent. The bioinformatic analysis allowed us to determine the spatial architecture of MLE-15, whose components were bactericidal peptide cecropin A connected via a flexible linker to the cell wall binding domain (CBD) of mesophilic 201ϕ2 - 1 endolysin and catalytic domain (EAD) of highly thermostable Ph2119 endolysin. The modular enzyme showed high thermostability with the melting temperature of 93.97 ± 0.38 °C, significantly higher than their natural counterparts derived from mesophilic sources. The minimum inhibitory concentration (MIC) of MLE-15 was 100 µg/mL for a panel of Gram-positive and Gram-negative bacteria, while the MIC of reline ranged from 6.25 to 25% v/v for the same strains. The addition of reline effectively reduced the MIC of MLE-15 from 100 µg/mL to 3.15-50 µg/mL. This combination displayed additive effects for most strains and synergism for extensively antibiotic-resistant Acinetobacter baumannii and Bacillus subtilis. The subsequent evaluation revealed that MLE-15 eliminated planktonic cells of A. baumannii RUH134, but was ineffective against matured biofilms. However, combined with reline, MLE-15 reduced the bacterial load in the matured biofilm by 1.39 log units. Confocal fluorescence microscopy indicated that reline damaged the structure of the biofilm, allowing MLE-15 to penetrate it. Additionally, MLE-15 and its combination with reline eradicated meropenem-persistent cells of A. baumannii RUH134. Effectiveness in lowering the MIC value of MLE-15 as well as protection against antibiotic-tolerant persister cells, indicate that MLE-15 and reline combination is a promising candidate for effective therapies in bacterial infections, which is especially important in the light of the global crisis of antimicrobial resistance.

Mechanism and performance of choline-based ionic liquids in enhancing nasal delivery of glucagon

Proteins and peptides have been increasingly developed as pharmaceuticals owing to their high potency and low side effects. However, their administration routes are confined to injections, such as intra-muscular and intra-venous injections, making patient compliance a challenge. Hence, non-injectable delivery systems are crucial to expanding the clinical use of proteins and peptides. In this context, two choline-based ionic liquids (ILs), namely, choline geranic acid ([Ch][Ger]) and choline citric acid ([Ch][Cit]), have been identified as promising agents for enhancing the permeation and prolonging the retention time of glucagon (GC) after intra-nasal administration. Notably, intra-nasal delivery of GC via ILs (GC/ILs) elicited rapid and smooth reversal of acute hypoglycaemia without leading to rebound hyperglycaemia in type 1 diabetic rats subjected to insulin induction. In addition, ILs could improve the transcellular transport of GC through electrostatic interaction. ILs could also transiently open inter-cellular tight junctions transiently to facilitate the paracellular transport of GC. Safety tests indicated that continuous intra-nasal delivery of ILs led to reversible changes, such as epithelial cell inflammation, goblet cell overgrowth, and impacts on the distribution of nasal cilia. However, these changes could be alleviated by the innate self-repair ability of mucosal epithelial cells. This study highlights the considerable potential of ILs for long-term nasal delivery of biomacromolecules.

Choline geranate (CAGE): A multifaceted ionic liquid for drug delivery

Ionic liquids, organic salts in a liquid state below 100 °C, have traditionally been associated with industrial applications. Recent research has introduced a new generation of ionic liquids, designed from biocompatible ions, to enable applications in drug delivery. Here, I provide a historical perspective, development status and applications of a leading example of biocompatible ionic liquids, a salt of Choline And Geranic acid (CAGE). Since its first report in 2014, CAGE has opened multiple drug delivery applications including transdermal, oral, buccal, sustained release, tissue ablation, periodontitis and hand hygiene, among others. CAGE-based products have been tested in more than 200 patients through multiple Phase 1 and Phase 2 clinical studies, including successful use in a Phase 2 clinical study in Atopic Dermatitis patients. CAGE became the first 'drug delivery ionic liquid' to enter into clinical trials. This article summarizes the key fundamental and translational aspects of CAGE as pertained to its use in drug delivery.

Comparison of the Antibacterial Activity of Selected Deep Eutectic Solvents (DESs) and Deep Eutectic Solvents Comprising Organic Acids (OA-DESs) Toward Gram-Positive and Gram-Negative Species

Deep eutectic solvents (DESs) have been intensively investigated in recent years for their antibacterial properties, with DESs that comprise organic acids (OA-DESs) showing promising antibacterial action. However a majority of the reports focused only on a limited number strains and techniques, which is not enough to determine the antibacterial potential of a substance. To bridge this gap, the antibacterial activity of classical DESs and OA-DESs is assessed on twelve Gram-negative and Gram-positive bacteria strains, with some of them exhibiting specific resistance toward antibiotics. The investigated formulations of OA-DESs comprise glycolic, malic, malonic, and oxalic acids as representatives of this group. Using a range of microbiological assays as well as physicochemical characterization methods, a major difference of the effectiveness between the two groups is demonstrated, with OA-DESs exhibiting, as expected, greater antibacterial effectiveness than classical DESs. Most interestingly, slight differences in the minimum inhibitory and bactericidal concentration values as well as time-kill kinetics profiles are observed between Gram-positive and Gram-negative strains. Transmission electron microscopy analysis reveals the effect of the treatment of the bacteria with the representatives of both groups of DESs, which allows us to better understand the possible mechanism-of-action of these novel materials.

Ionic liquids and deep eutectic solvents for the stabilization of biopharmaceuticals: A review

Biopharmaceuticals have allowed the control of previously untreatable diseases. However, their low solubility and stability still hinder their application, transport, and storage. Hence, researchers have applied different compounds to preserve and enhance the delivery of biopharmaceuticals, such as ionic liquids (ILs) and deep eutectic solvents (DESs). Although the biopharmaceutical industry can employ various substances for enhancing formulations, their effect will change depending on the properties of the target biomolecule and environmental conditions. Hence, this review organized the current state-of-the-art on the application of ILs and DESs to stabilize biopharmaceuticals, considering the properties of the biomolecules, ILs, and DESs classes, concentration range, types of stability, and effect. We also provided a critical discussion regarding the potential utilization of ILs and DESs in pharmaceutical formulations, considering the restrictions in this field, as well as the advantages and drawbacks of these substances for medical applications. Overall, the most applied IL and DES classes for stabilizing biopharmaceuticals were cholinium-, imidazolium-, and ammonium-based, with cholinium ILs also employed to improve their delivery. Interestingly, dilute and concentrated ILs and DESs solutions presented similar results regarding the stabilization of biopharmaceuticals. With additional investigation, ILs and DESs have the potential to overcome current challenges in biopharmaceutical formulation.

Potentials of ionic liquids to overcome physical and biological barriers

Over the last decades, ionic liquids (IL) have shown great potential in non-invasive delivery starting from synthetic small molecules to biological large molecules. ILs are emerging as a particular class of drug delivery systems due to their unique physiochemical properties, simple surface modification, and functionalization. These features of IL help achieve specific design principles that are essential for a non-invasive drug delivery system. In this review, we have discussed IL and their applications in non-invasive drug delivery systems. We evaluated state-of-the-art development and advances of IL aiming to mitigate the biological and physical barriers to improve transdermal and oral delivery, summarized in this review. We also provided an overview of the various factors determining the systemic transportation of IL-based formulation. Additionally, we have emphasized how the ILs facilitate the transportation of therapeutic molecules by overcoming biological barriers.

Ligand-Independent Activation of Aryl Hydrocarbon Receptor and Attenuation of Glutamine Levels by Natural Deep Eutectic Solvent

Natural deep eutectic solvents (NADESs) are emerging sustainable alternatives to conventional organic solvents. Beyond their role as laboratory solvents, NADESs are increasingly explored in drug delivery and as therapeutics. Their increasing applications notwithstanding, our understanding of how they interact with biomolecules at multiple levels - metabolome, proteome, and transcriptome - within human cell remain poor. Here, we deploy integrated metabolomics, proteomics, and transcriptomics to probe how NADESs perturb the molecular landscape of human cells. In a human cell line model, we found that an archetypal NADES derived from choline and geranic acid (CAGE) significantly altered the metabolome, proteome, and transcriptome. CAGE upregulated indole-3-lactic acid and 4-hydroxyphenyllactic acid levels, resulting in ligand-independent activation of aryl hydrocarbon receptor to signal the transcription of genes with implications for inflammation, immunomodulation, cell development, and chemical detoxification. Further, treating the cell line with CAGE downregulated glutamine biosynthesis, a nutrient rapidly proliferating cancer cells require. CAGE's ability to attenuate glutamine levels is potentially relevant for cancer treatment. These findings suggest that NADESs, even when derived from natural components like choline, can indirectly modulate cell biology at multiple levels, expanding their applications beyond chemistry to biomedicine and biotechnology.

Unusual photophysics of geranic acid deep eutectic solvents

The photophysics of natural deep eutectic solvents (NADESs) remains unexplored. Here, we report that a class of NADESs aggregates in water, enabling through-space interaction as evidenced by an unusual emission and redshifted UV absorption band. The NADESs enhanced fluorescence excitation and emission of fluorogenic proteins for improved bioimaging.

Enabling Sustainable Chemistry with Ionic Liquids and Deep Eutectic Solvents: A Fad or the Future?

Ionic liquids (ILs) and deep eutectic solvents (DESs) debuted with a promise of a superior sustainability footprint due to their low vapor pressure. However, their toxicity and high cost compromise this footprint, impeding their real-world applications. Fortunately, their property tunability through a rational selection of precursors, including bioderived ones, provides a strategy to ameliorate toxicity, lower cost, and endow new functions. This Review discusses whether ILs and DESs are sustainable solvents and how they contribute to sustainable chemical processes.

An overview of biomedical applications of choline geranate (CAGE): a major breakthrough in drug delivery

A number of studies are on the way to advancing the field of biomedical sciences using ionic liquids (ILs) and deep eutectic solvents (DESs) in view of their unique properties and inherent tunability. These significant solvents tend to enhance the physical properties of the drug, increase their bioavailability and promote the delivery of recalcitrant drugs to the body. One such widely investigated tempting multipurpose IL/DES system is choline geranate (CAGE), which has gained significant interest due to its biocompatible and highly potent antiseptic behavior, which also facilitates its sanitizing ability to combat the coronavirus. This review focuses on total advancements in biomedical applications of CAGE. This biocompatible IL/DES has made facile the solubilization of hydrophobic and hydrophilic drugs and delivery of intractable drugs through physiological barriers by stabilizing proteins and nucleic acids. Therefore, it has been used as a transdermal, subcutaneous, and oral delivery carrier and as an antimicrobial agent to treat infectious diseases and wounds as approved by laboratory and clinical translations. Moreover, current challenges and future outlooks are also highlighted to explore them more purposefully.

Ionic Liquids: Promising Approach for Oral Drug Delivery

Oral administration is the most preferred route for drug administration in clinic. However, due to unsatisfactory physicochemical properties of drugs and various physiological barriers, the oral bioavailability of most poorly water-soluble and macromolecules drugs is low and the therapeutic effect is unsatisfactory. Ionic liquids (ILs), molten salts with unique properties, show amazing potential for oral delivery. In addition to being able to form active pharmaceutical ingredients based ILs (API-ILs) to overcome drug solubility and polymorphism issues, ILs have also been used to enhance the solubility of poorly soluble drugs, enhance drug stability in the gastrointestinal environment, improve drug permeability in intestinal mucus, and facilitate drug penetration across the intestinal epithelial barrier. Furthermore, ILs were attempted as formulation components to develop novel oral drug delivery systems. This review focus on the application progress of ILs in oral drug delivery and the mechanisms. The challenges and perspectives of the development of ILs-based oral delivery systems are also discussed. This article reviews the latest advances of ionic liquids for oral drug delivery, focusing on the application and related mechanisms of ionic liquids in improving the drug physicochemical properties and enhancing drug delivery across physiological barriers.