Recent Developments on Ionic Liquids and Deep Eutectic Solvents for Drug Delivery Applications

The Use of Deep Eutectic Solvents for the Synthesis of Iron Oxides Nanoparticles: A Driving Force for Materials Properties

In this study, we explored the use of Deep Eutectic Solvents (DESs) as a green and sustainable alternative for the synthesis of Iron Oxide Nanoparticles (IONs). Six different binary mixtures of Hydrogen Bond Acceptors (HBAs) and Donors (HBDs) were prepared and thoroughly characterized to investigate how their components and physicochemical properties influence the structure, morphology, and magnetic properties of the resulting IONs. In addition, the role of DESs was assessed using ATR-MIR spectroscopy, providing insights into HBA-HBD interactions with iron precursors. The study highlights the critical role of DES constituents, particularly the interactions between HBAs and HBDs, in directing nanoparticle size, structure, and morphology. Indeed, our results demonstrate that the choice of DES significantly impacts the crystalline phase of iron oxide nanoparticles, yielding either magnetite (Fe₃O₄) or hematite (α-Fe₂O₃). These findings established a robust framework for leveraging DES in nanomaterial synthesis, paving the way for more environmentally friendly approaches in diverse industrial and scientific applications.

Deep eutectic solvents in analysis, delivery and chemistry of pharmaceuticals

Deep eutectic solvents (DES) have an emerging scientific role, assisting modern pharmaceutics. They are uniquely supporting the resolution of crucial issues, such as the effective extraction and isolation of bio-actives. They act as media and catalysts for pharmaceutical drug synthesis, and as green solvents and modifiers in pharmaceutical analysis. Their role in pharmaceutical formulation and drug delivery is also up-and-coming, for instance, as alternative drug-solubilizing agents, drug stabilizers and functional additives, as therapeutic deep eutectic solvents, deep eutectic API, and monomers and reaction media for the synthesis of biomaterials for advanced drug delivery. The DES also help transforming medicinal/pharmaceutical chemistry. Although DES were described in 1918, their first pharmaceutical use is only reported in 1960. In view of their broad applicability in pharmaceutics, it may be interesting to review their history, origin, evolution, potential advantages, limitations, and specific applications as green solvents. A chronological and comparative study of the literature showed the important role of DES in green approaches for modern pharmaceuticals. The concepts, applications, and outcomes of DES in pharmaceutical analysis, formulation/drug delivery, and pharmaceutical/medicinal chemistry are presented. A comprehensive outline of the atypical applications of DES as effective green solvents in pharmaceutical bioactive extraction was assessed. Efforts to present classifications of DES explored in pharmaceuticals were also made. The present manuscript also covers computational trend, adds on commercial aspects with potential future applications of DES in pharmaceutical sciences.

Sequential pH/GSH-responsive stealth nanoparticles for co-delivery of anti-PD-1 antibody and paclitaxel to enhance chemoimmunotherapy of lung cancer

Intravenously administered nanoparticles (NPs) often bind with plasma proteins, forming the protein corona that promotes rapid systemic clearance, a primary challenge in nanomedicine. In this study, we developed a pH- and GSH-sensitive "stealth" nanodelivery system, PTX@NPs-aPD1-IL, for sequential drug release. By using a biocompatible choline-based ionic liquid (IL) as the coating for NPs, the interaction and adsorption of NPs with serum proteins were reduced, achieving targeted delivery to the lung organ and increasing drug accumulation. In the weakly acidic extracellular tumor microenvironment (pH 6.5), the anti-PD-1 antibody (aPD-1) was first released to block the PD-1/PD-L1 pathway and restore the immunocidal function of T cells. In the highly reductive intracellular environment of tumor cells, the disulfide bonds were cleaved, causing NPs to rupture and release paclitaxel (PTX). It induced tumor cell apoptosis and triggered immunogenic cell death (ICD), promoted dendritic cells (DCs) maturation and activated T cells for chemo-immunotherapy. In the mouse orthotopic lung cancer model, PTX@NPs-aPD1-IL exhibited superior efficacy to other treatment groups at the same dose. This was due to the significantly increase in the release of immune factors, including TNF-α and IFN-γ, and the promotion of CD8+ T cells recruitment, which induced a stronger immune response, and thus enhanced the anti-lung cancer effect. In summary, PTX@NPs-aPD1-IL provided a promising strategy for effective chemo-immunotherapy for lung cancer through sequential release profile.

An Overview on the Role of Ionic Liquids and Deep Eutectic Solvents in Oral Pharmaceuticals

Over the past twenty years, ionic liquids (ILs) and deep eutectic solvents (DESs) have gained recognition across various fields, including catalysis, extraction and purification, materials science, and biotechnology. Notably, the use of ILs and DESs in pharmaceutical research, especially in drug delivery, has seen remarkable expansion over the past decade. This review offers a comprehensive analysis of ILs and DESs specifically designed for the oral administration of drugs having unfavorable biopharmaceutical properties. The classification and characteristics of ILs and DESs, along with their newer natural (Bio-ILs and NaDESs) and therapeutic subcategories (API-ILs and TheDESs) are outlined. Additionally, a further subgroup of ILs, known as surface active ionic liquids (SAILs), is described. Then, a detailed examination of the available manufacturing methods in a sustainable, time-consuming, and scalable perspective, and toxicity concerns in relation to their subdivision are evaluated. Finally, their specific applications in oral drug delivery, whether used as neat solvents or converted into administrable dosage forms, are analyzed and discussed. Despite the significant advancements in recent years regarding the use of these solvents in oral drug delivery, there are still many aspects that need further investigation. These include their interaction with biological systems (gastrointestinal fluids and mucosa), their long-term stability, and the development of effective drug delivery systems.

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.

Investigating the synergistic effects of apple vinegar and deep eutectic solvent as natural antibiotics: an experimental and COSMO-RS analysis

The present investigation examines the antimicrobial and antifungal characteristics of natural deep eutectic solvents (NADES) and apple vinegar in relation to a diverse array of bacterial and fungal strains. The clinical bacterial strains, including gram-negative and gram-positive, and the fungal pathogen Candida albicans, were subjected to solid medium diffusion to determine the inhibitory effects of these compounds. The results show that NADES has superior antimicrobial and antifungal action compared to apple vinegar. The observed inhibitory zones for apple vinegar and NADES varied in length from 16.5 to 24.2 and 16 to 52.5 mm, respectively. The results obtained indicate that no synergy is observed for this mixture (50% AV + 50% NADES). The range of values for bactericidal concentrations (MBC) and minimal inhibitory concentrations (MIC) was 0.0125 to 0.2 and 0.0125 to 0.4 µl/ml, respectively. Antibacterial and antifungal chemicals may be found in apple vinegar and NADES, with NADES offering environmentally safe substitutes for traditional antibiotics. Additional investigation is suggested to refine these compounds for a wide range of bacteria, which could create antimicrobial solutions that are both highly effective and specifically targeted, thereby offering extensive potential in medicine and the environment.

Pharmaceutical applications of therapeutic deep eutectic systems (THEDES) in maximising drug delivery

The issue of poor solubility of active pharmaceutical ingredients (APIs) has been a salient area of investigation and novel drug delivery systems are being developed to improve the solubility of drugs, enhance their permeability and thereby their efficacy. Several techniques for solubilization enhancement of poorly soluble drugs are often employed at various stages of pharmaceutical drug product development. One such delivery system is the therapeutic deep eutectic system (THEDES), which showed great potential in the enhancement of solubility and permeability of drugs and ultimately augmenting their bioavailability. THEDES are made by mixing drugs with deep eutectic solvents (DESs) in a definite molar ratio by the hit and trial method. The DESs are a new class of green solvents which are non-toxic, cheap, easy to prepare, biodegradable and have multiple applications in the pharmaceutical industry. The terminologies such as ionic liquids (ILs), DES, THEDES, and therapeutic liquid eutectic systems (THELES) have been very much in use recently, and it is important to highlight the pharmaceutical applications of these unexplored reservoirs in drug solubilization enhancement, drug delivery routes, and in the management of various diseases. This review is aimed at discussing the components, formulation strategies, and routes of administration of THEDES that are used in developing the formulation. Also, the major pharmaceutical applications of THEDES in the treatment of various metabolic and non-metabolic diseases are reviewed.

Neutron reflectometry as a powerful tool to elucidate membrane interactions of drug delivery systems

The last couple of decades have seen an explosion of novel colloidal drug delivery systems, which have been demonstrated to increase drug efficacy, reduce side-effects, and provide various other advantages for both small-molecule and biomacromolecular drugs. The interactions of delivery systems with biomembranes are increasingly recognized to play a key role for efficient eradication of pathogens and cancer cells, as well as for intracellular delivery of protein and nucleic acid drugs. In parallel, there has been a broadening of methodologies for investigating such systems. For example, advanced microscopy, mass-spectroscopic "omic"-techniques, as well as small-angle X-ray and neutron scattering techniques, which only a few years ago were largely restricted to rather specialized areas within basic research, are currently seeing increased interest from researchers within wide application fields. In the present discussion, focus is placed on the use of neutron reflectometry to investigate membrane interactions of colloidal drug delivery systems. Although the technique is still less extensively employed for investigations of drug delivery systems than, e.g., X-ray scattering, such studies may provide key mechanistic information regarding membrane binding, re-modelling, translocation, and permeation, of key importance for efficacy and toxicity of antimicrobial, cancer, and other therapeutics. In the following, examples of this are discussed and gaps/opportunities in the research field identified.

Piperacillin/Tazobactam Co-Delivery by Micellar Ionic Conjugate Systems Carrying Pharmaceutical Anions and Encapsulated Drug

Previously obtained amphiphilic graft copolymers based on [2-(methacryloyloxy)ethyl]trimethylammonium chloride (TMAMA) ionic liquid were used as the matrices of three types of nanocarriers, i.e., conjugates with ionic piperacillin (PIP) and micelles with tazobactam (TAZ), which represented single systems, and dual systems bearing PIP anions and encapsulated TAZ for co-delivery. The exchange of Cl anions in TMAMA units with PIP ones resulted in a yield of 45.6-72.7 mol.%. The self-assembling properties were confirmed by the critical micelle concentration (CMC), which, after ion exchange, increased significantly (from 0.011-0.020 mg/mL to 0.041-0.073 mg/mL). The amphiphilic properties were beneficial for TAZ encapsulation to reach drug loading contents (DLCs) in the ranges of 37.2-69.5 mol.% and 50.4-80.4 mol.% and to form particles with sizes of 97-319 nm and 24-192 nm in the single and dual systems, respectively. In vitro studies indicated that the ionically conjugated drug (PIP) was released in quantities of 66-81% (7.8-15.0 μg/mL) from single-drug systems and 21-25% (2.6-3.9 μg/mL) from dual-drug systems. The release of encapsulated TAZ was more efficient, achieving 47-98% (7.5-9.0 μg/mL) release from the single systems and 47-69% (9.6-10.4 μg/mL) release from the dual ones. Basic cytotoxicity studies showed non-toxicity of the polymer matrices, while the introduction of the selected drugs induced cytotoxicity against normal human bronchial epithelial cells (BEAS-2B) with the increase in concentration.

Natural Deep Eutectic Solvents as Rust Removal Agents from Lithic and Cellulosic Substrates

The peculiar physicochemical features of deep eutectic solvents (DESs), in particular their tunability, make them ideal media for various applications. Despite their ability to solubilize metal oxides, their use as rust removers from valuable substrates has not yet been thoroughly investigated. In this study, we chose three known DESs, consisting of choline chloride and acetic, oxalic or citric acid for evaluating their ability to remove corrosion products from a cellulose-based material as linen fabric and two different lithotypes, as travertine and granite. The artificial staining was achieved by placing a rusty iron grid on their surfaces. The DESs were applied by means of cellulose poultice on the linen fabrics, while on the rusted stone surfaces with a cotton swab. Macro- and microscopic observations, colorimetry and SEM/EDS analysis were employed to ascertain the cleaning effectiveness and the absence of side effects on the samples after treatment. Oxalic acid-based DES was capable of removing rust stains from both stone and cellulose-based samples, while choline chloride/citric acid DES was effective only on stone specimens. The results suggest a new practical application of DESs for the elimination of rust from lithic and cellulosic substrates of precious and artistic value.

Antibacterial and Antioxidant Study of New Pharmaceutical Formulation of Didecyldimethylammonium Bromide Via Pharmaceutical Deep Eutectic Solvents (PDESs) Principle

Combination therapies have been studied by many researchers using different techniques and methods to solve some solid drug problems and improve more effective treatments for humans and animals. One of the more significant findings to emerge from this study is that the combination of pharmaceutical agents by using pharmaceutical deep eutectic solvents (PDESs) in order to produce dual action drugs and reduce the drug resistance. The major objective of this study was to investigate the dual functionality of drugs (antioxidant and antibacterial activity) via the principle of PDESs. The produced PDESs were characterized via different techniques, namely differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR), and UV-Vis spectrophotometry. We herein tested a panel of novel liquid formulations of didecyldimethylammonium bromide (DDMAB) against a selection of pathogenic bacteria, classifying their spectrum of activity against Gram-positive and Gram-negative bacteria. The current study found that the PDESs can be used to produce drugs with dual functionalities. The produced PDES from (ascorbic acid: DDMAB) exhibits stronger antibacterial activity against Gram-positive Staphyloccocus aureus and Staphyloccocus epidermidis than gram negatives. One of the most interesting PDESs studied in this research was that of DDMAB and ascorbic acid. This forms a eutectic which is far from the solid drugs issues and shows dual functionality like antibacterial and antioxidant activity. This study has found that there is a correlation between the molecular docking study and the biological activities of the combined drugs.

Using mandelic acid as an extraction solvent in the extraction of Cu(II) and Cd(II) from soil samples

In this study, an efficient, green, and rapid sample preparation method based on mandelic acid dimer was proposed for the extraction of Cu(II) and Cd(II) from soil samples followed by flame atomic absorption spectrometry. In this research, for the first time, the liquid dimer was prepared by heating solid mandelic acid. Then the mixture of soil and a complexing agent was added into it. The mixture was transferred into a microwave oven. Diluted nitric acid solution as a dilution solvent was added. After centrifugation, two aliquots of the collected phase were removed and injected into the instrument. The relevant optimization parameters such as dimer volume, microwave exposure time, amount of complexing agent, and the type and volume of dilution solvent were investigated and optimized. Under the optimum conditions, detection limits were obtained 0.17 and 0.16 mg Kg-1 for Cu(II) and Cd(II), respectively. The linear ranges were 0.50-50 mg Kg-1 with coefficient of determination ≥ 0.9981. The developed method along with a reference method was applied for the analysis of the selected heavy metal ions in different soil samples and comparable results were obtained. Also, the method was performed on a certified reference material and the obtained concentrations compared with the certificated concentrations to assess accuracy of the proposed method.

Oxymatrine-fatty acid deep eutectic solvents as novel penetration enhancers for transdermal drug delivery: formation mechanism and enhancing effect

Transdermal delivery of drugs is commonly limited by low skin permeability. The aim of the study was to synthesize deep eutectic solvents (DESs) based on oxymatrine (OMT) and fatty acids with various alkyl chain lengths (LCFAs) as novel vehicles, to solubilize the water-insoluble drug and enhance percutaneous penetration. Quercetin (QUE) was selected as a model drug. Combining differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR), and molecular simulations demonstrated that the formation of DESs was mediated by charge-assisted hydrogen bonding. Physicochemical properties including stability, viscosity, and solubilization capacity were also studied. Subsequently, the effect of three stable DESs on drug release and skin permeability was evaluated. The results showed that QUE was solubilized well and presented a different sustained release behavior in DESs. Meanwhile, DESs enhanced the skin permeation of OMT and QUE, which was influenced by alkyl chain lengths of LCFAs, whereas DES consisting of lauric acid (LA) exhibited the highest enhancing effect. FTIR, DSC, and molecular docking further demonstrated consistency between micro molecular mechanism and macro penetration behavior. Additionally, HaCaT cells treated with DESs showed high cell viability, suggesting their good skin safety. Taken together, OMT-LCFA DESs would be a promising penetration enhancer for transdermal drug delivery, which also provides guidance for the design of new DESs.

Polyphenol Iongel Patches with Antimicrobial, Antioxidant and Anti-Inflammatory Properties

There is an actual need for developing materials for wound healing applications with anti-inflammatory, antioxidant, or antibacterial properties in order to improve the healing performance. In this work, we report the preparation and characterization of soft and bioactive iongel materials for patches, based on polymeric poly(vinyl alcohol) (PVA) and four ionic liquids containing the cholinium cation and different phenolic acid anions, namely cholinium salicylate ([Ch][Sal]), cholinium gallate ([Ch][Ga]), cholinium vanillate ([Ch][Van]), and cholinium caffeate ([Ch][Caff]). Within the iongels, the phenolic motif in the ionic liquids plays a dual role, acting as a PVA crosslinker and a bioactive compound. The obtained iongels are flexible, elastic, ionic conducting, and thermoreversible materials. Moreover, the iongels demonstrated high biocompatibility, non-hemolytic activity, and non-agglutination in mice blood, which are key-sought material specifications in wound healing applications. All the iongels have shown antibacterial properties, being PVA-[Ch][Sal], the one with higher inhibition halo for Escherichia Coli. The iongels also revealed high values of antioxidant activity due to the presence of the polyphenol, with the PVA-[Ch][Van] iongel having the highest activity. Finally, the iongels show a decrease in NO production in LPS-stimulated macrophages, with the PVA-[Ch][Sal] iongel displaying the best anti-inflammatory activity (>63% at 200 µg/mL).

Influence of Metal Salts Addition on Physical and Electrochemical Properties of Ethyl and Propylammonium Nitrate

In this work, we deepen in the characterization of two protic ionic liquids (PILs), ethylammonium nitrate (EAN) and propylammonium nitrate (PAN). With this aim, we determined the influence of inorganic nitrate salts addition on their physical properties and their electrochemical potential window (EPW). Thus, experimental measurements of electrical conductivity, density, viscosity, refractive index and surface tension of mixtures of {EAN or PAN + LiNO₃, Ca(NO₃)₂, Mg(NO₃)₂ or Al(NO₃)₃} at a temperature range between 5 and 95 °C are presented first, except for the last two properties which were measured at 25 °C. In the second part, the corresponding EPWs were determined at 25 °C by linear sweep voltammetry using three different electrochemical cells. Effect of the salt addition was associated mainly with the metal cation characteristics, so, generally, LiNO₃ showed the lower influence, followed by Ca(NO₃)₂, Mg(NO₃)₂ or Al(NO₃)₃. The results obtained for the EAN + LiNO₃ mixtures, along with those from a previous work, allowed us to develop novel predictive equations for most of the presented physical properties as functions of the lithium salt concentration, the temperature and the water content. Electrochemical results showed that a general order of EPW can be established for both PILs, although exceptions related to measurement conditions and the properties of the mixtures were found.

Deep Eutectic Systems as Novel Vehicles for Assisting Drug Transdermal Delivery

In recent years, deep eutectic systems (DES) emerged as novel vehicles for facilitating the transdermal delivery of various drugs, including polysaccharides, proteins, insulin, vaccine, nanoparticles, and herb extracts. The objective of this study is to conduct a comprehensive review of the application of DES to transdermal drug delivery, based on previous work and the reported references. Following a brief overview, the roles of DES in TDDS, the modes of action, as well as the structure-activity relationship of DES are discussed. Particularly, the skin permeation of active macromolecules and rigid nanoparticles, which are the defining characteristics of DES, are extensively discussed. The objective is to provide a comprehensive understanding of the current investigation and development of DES-based transdermal delivery systems, as well as a framework for the construction of novel DES-TDDS in the future.

Ionic Liquids-Based Drug Delivery: a Perspective

Ionic liquids (ILs) recently draw attention for addressing unmet needs in biomedicines. By converting solids into liquids, ILs are emerging as novel platforms to overcome some critical drawbacks associated with the application of solid or crystalline active pharmaceutical ingredients (APIs). ILs have shown promise in liquidizing or solubilizing APIs, or as green solvents, novel permeation enhancers or active ingredients, alone or synergistically with APIs. Meanwhile, challenges turn up in company with the deepening understanding of ILs as drug delivery carrier systems. This perspective aims to provide a sketchy overview on the status quo with specific attention paid to new problems arising from the utilization of ILs-based technologies in drug delivery.