Ionic Liquid-Like Pharmaceutical Ingredients and Applications of Ionic Liquids in Medicinal Chemistry: Development, Status and Prospects

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.

Use of ionic liquids in amidation reactions for proteolysis targeting chimera synthesis

Selective degradation of disease-causing proteins using proteolysis targeting chimeras (PROTACs) has gained great attention, thanks to its several advantages over traditional therapeutic modalities. Despite the advances made so far, the structural chemical complexity of PROTACs poses challenges in their synthetic approaches. PROTACs are typically prepared through a convergent approach, first synthesizing two fragments separately (target protein and E3 ligase ligands) and then coupling them to produce a fully assembled PROTAC. The amidation reaction represents the most common coupling exploited in PROTACs synthesis. Unfortunately, the overall isolated yields of such synthetic procedures are usually low due to one or more purification steps to obtain the final PROTAC with acceptable purity. In this work, we focused our attention on the optimization of the final amidation step for the synthesis of an anti-SARS-CoV-2 PROTAC by investigating different amidation coupling reagents and a range of alternative solvents, including ionic liquids (ILs). Among the ILs screened, [OMIM][ClO4] emerged as a successful replacement for the commonly used DMF within the HATU-mediated amidation reaction, thus allowing the synthesis of the target PROTAC under mild and sustainable conditions in very high isolated yields. With the optimised conditions in hand, we explored the scalability of the synthetic approach and the substrate scope of the reaction by employing different E3 ligase ligand (VHL and CRBN)-based intermediates containing linkers of different lengths and compositions or by using different target protein ligands. Interestingly, in all cases, we obtained high isolated yields and complete conversion in short reaction times.

Active pharmaceutical ingredients (APIs) in ionic liquids: An effective approach for API physiochemical parameter optimization

Ionic liquids (ILs) are widely used as solvents, co-solvents and permeation enhancers in the biomedical and pharmaceutical fields. There are many advantages to using active pharmaceutical ingredients (APIs) in the production of ILs for drug delivery, including the ability to tailor solubility, improve thermal stability, increase dissolution, regulate drug release, improve API permeability, and modulate cytotoxicity on tumor cells. Such an approach has shown significant potential as a tool for drug delivery. As a result, APIs converted into ILs are used as active components in solutions, emulsions, and even nanoparticles (NPs). In this review, we explore the use and physiochemical characteristics of APIs via ILs, including improvements of their physicochemical properties in preformulation and formulation development.

Biocompatible Cationic Lipoamino Acids as Counterions for Oral Administration of API-Ionic Liquids

Purpose

The use of ionic liquids (ILs) in drug delivery has focused attention on non-toxic IL counterions. Cationic lipids can be used to form ILs with weakly acidic drugs to enhance drug loading in lipid-based formulations (LBFs). However, cationic lipids are typically toxic. Here we explore the use of lipoaminoacids (LAAs) as cationic IL counterions that degrade or digest in vivo to non-toxic components.

Methods

LAAs were synthesised via esterification of amino acids with fatty alcohols to produce potentially digestible cationic LAAs. The LAAs were employed to form ILs with tolfenamic acid (Tol) and the Tol ILs loaded into LBF and examined in vitro and in vivo.

Results

Cationic LAAs complexed with Tol to generate lipophilic Tol ILs with high drug loading in LBFs. Assessment of the LAA under simulated digestion conditions revealed that they were susceptible to enzymatic degradation under intestinal conditions, forming biocompatible FAs and amino acids. In vitro dispersion and digestion studies of Tol ILs revealed that formulations containing digestible Tol ILs were able to maintain drug dispersion and solubilisation whilst the LAA were breaking down under digesting conditions. Finally, in vivo oral bioavailability studies demonstrated that oral delivery of a LBF containing a Tol IL comprising a digestible cationic lipid counterion was able to successfully support effective oral delivery of Tol.

Conclusions

Digestible LAA cationic lipids are potential IL counterions for weakly acidic drug molecules and digest in situ to form non-toxic breakdown products.

Supplementary Information

The online version contains supplementary material available at 10.1007/s11095-022-03305-y.

Etidronate-based organic salts and ionic liquids: In vitro effects on bone metabolism

Bisphosphonates are a class of drugs widely used for the treatment of several pathologies associated with increased bone resorption. Although displaying low oral bioavailability, these drugs have the ability to accumulate in bone matrix, where the biological effects are exerted. In the present work, four mono- and dianionic Etidronate-based Organic Salts and Ionic Liquids (Eti-OSILs) were developed by combination of this drug with the superbases 1,1,3,3-tetramethylguanidine (TMG) and 1,5-diazabicyclo(4.3.0)non-5-ene (DBN) as cations, aiming to improve not only the physicochemical properties of this seminal bisphosphonate, but also its efficacy in the modulation of cellular behavior, particularly on human osteoclasts and osteoblasts. It was observed that some of the developed compounds, in particular the dianionic ones, presented very high water solubility and diminished or absent polymorphism. Also, several of them appeared to be more cytotoxic against human breast and osteosarcoma cancer cell lines while retaining low toxicity to normal cells. Regarding bone cells, a promotion of an anabolic state was observed for all Eti-OSILs, primarily for the dianionic ones, which leads to an inhibition of osteoclastogenesis and an increase in osteoblastogenesis. The observed effects resulted from differential modulation of intracellular signaling pathways by the Eti-OSILs in comparison with Etidronate. Hence, these results pave the way for the development of more efficient and bioavailable ionic formulations of bisphosphonates aiming to effectively modulate bone metabolism, particularly in the case of increased bone resorption.

Natural deep eutectic solvents as tailored and sustainable media for the extraction of five compounds from compound liquorice tablets and their comparison with conventional organic solvents

An efficient and environmentally friendly ultrasound-assisted (UAE) natural deep eutectic solvent (NADES) extraction method was applied for the extraction of five bioactive compounds (liquiritin, isoliquiritin, liquiritigenin, glycyrrhizic acid and isoliquiritigenin) from compound liquorice tablets (CPLTs), and the antioxidant activities of these compounds were evaluated. In this study, eighteen different NADES systems based on either two or three components were tested and a 1,4-butanediol–levulinic acid system (1 : 3 molar ratio) was selected as a topgallant solvent for maximizing analyte extraction yields. Various extraction parameters, such as water content, liquid/solid ratio, extraction time and temperature, were systematically optimized by single-factor and response surface methodology (RSM) experiments. The results indicated that the optimum extraction conditions for the analytes featured a water content of 17%, a liquid/solid ratio of 42 mL g⁻¹ and an extraction time of 30 min. The extracted amounts of liquiritin, isoliquiritin, liquiritigenin, glycyrrhizic acid and isoliquiritigenin reached 5.60, 3.17, 1.27, 74.62 and 1.34 mg g⁻¹, respectively, under optimized conditions, which were much higher than those extracted using conventional organic solvents. In addition, antioxidant tests revealed that the NADES extracts showed higher DPPH and hydroxyl radical-scavenging capacity than the conventional solvent extracts used for comparison. This study provides a suitable approach for efficiently extracting the bioactive compounds of CPLTs. Meanwhile, NADESs can be extended to other natural products as green extraction media.

A 1,4-butanediol–levulinic acid system was selected as a topgallant solvent and extraction parameters were optimized. NADES extracts exhibited higher extraction efficiency and in vitro antioxidant activities than conventional solvent extracts.

Ionic liquids as a useful tool for tailoring active pharmaceutical ingredients

Ionic liquids (ILs) have been widely used in biomedical and pharmaceutical fields as solvents or permeation enhancers. Recently, more and more researchers focused on optimizing the physicochemical properties of active pharmaceutical ingredient (API) by ILs technology. Converting APIs into ILs (API-ILs) has shown great potential for drug delivery by eliminating polymorphism, tailoring solubility, improving thermal stability, increasing dissolution, controlling drug release, modulating the surfactant properties, enhancing permeability of APIs and modulating cytotoxicity on tumor cells. In addition, API-ILs are also used in various formulations as active ingredients, such as solutions, emulsions, even tablets or nanoparticles. This paper aims to review current status of API-ILs, including the rational and design, preparation and characterization, the improvement on the physicochemical characteristics of APIs, the compatibility of API-ILs with various formulations, and the future prospects of API-ILs in biomedical and pharmaceutical fields.

Review of advances in the development of laccases for the valorization of lignin to enable the production of lignocellulosic biofuels and bioproducts

Development and deployment of commercial biorefineries based on conversion of lignocellulosic biomass into biofuels and bioproducts faces many challenges that must be addressed before they are commercially viable. One of the biggest challenges faced is the efficient and scalable valorization of lignin, one of the three major components of the plant cell wall. Lignin is the most abundant aromatic biopolymer on earth, and its presence hinders the extraction of cellulose and hemicellulose that is essential to biochemical conversion of lignocellulose to fuels and chemicals. There has been a significant amount of work over the past 20 years that has sought to develop innovative processes designed to extract and recycle lignin into valuable compounds and help reduce the overall costs of the biorefinery process. Due to the complex matrix of lignin, which is essential for plant survival, the development of a reliable and efficient lignin conversion technology has been difficult to achieve. One approach that has received significant interest relies on the use of enzymes, notably laccases, a class of multi‑copper green oxidative enzymes that catalyze bond breaking in lignin to produce smaller oligomers. In this review, we first assess the different innovations of lignin valorization using laccases within the context of a biorefinery process, and then assess the latest economical advances that these innovations offered. Finally, we review laccase characterization and optimization, as well as the prospects and bottlenecks of this class of enzymes within the industrial and biorefining sectors.

A computational approach for the screening of potential antiviral compounds against SARS-CoV-2 protease: Ionic liquid vs herbal and natural compounds

The current scenario across the globe shows unprecedented healthcare and an economic crisis due to the Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2). Recently, the World Health Organization (WHO) has declared a pandemic stage worldwide because of the high mortality and morbidity rate caused by novel infection disease. There have been several clinical trials and identification underway to find a treatment of this novel virus. For the treatment of severe infection involves the blocking of the replication of its CoV-2 protein. Hydroxychloroquine and remdesivir has been used on an emergency basis for its treatment. The uncontrolled infection and increasing death rate underline the emergence to develop the antiviral drug. In our study, the blind docking of various classes of compounds including control antiviral drugs (abacavir, acyclovir, quinoline, hydroxyquinoline), antimicrobial drugs (levofloxacin, amoxicillin, cloxacin, ofloxacin), natural compounds (lycorine, saikosaponins, myricetin, amentaflavone), herbal compounds (silymarin, palmatine, curcumin, eugenin) available in Indian Ayurveda was done. Besides, we have also performed the blind docking of various ionic liquids (ILs) such as pyrrolidinium, piperidinium, pyridinium, imidazolium based ILs against CoV-2 protease as they have recently emerged as a potential antimicrobial agent. Further, the pharmacokinetic properties and cytotoxicity of the compounds were determined computationally. The docking results showed successful binding to the active site or near a crucial site. The present computational approach was found helpful to predict the best possible inhibitor of protease and may result in an effective therapeutic agent against COVID-19.

Ionic liquids containing ketoconazole improving topical treatment of T. Interdigitale infection by synergistic action

This study aimed to exert the synergistic action of ketoconazole (KCZ) and ionic liquids (ILs) for improving antifungal effect. Various ILs were engineered and demonstrated different solubilization capacity for KCZ. Among them, the IL formed by choline and geranic acid ([Ch][Ger]) was the optimal one and able to imporve the solubility of KCZ by around 100-fold. The in vitro antifungal test revealed the [Ch][Ger] significantly inhibited the activity of T. Interdigitale and exerted the synergistic action with KCZ. Compared to Daktarin®, the [Ch][Ger] not only promoted KCZ to penetrate into deep skin layer but also improved in vivo anti-T. Interdigitale activity significantly. Besides, the [Ch][Ger] was able to strip the skin of the lesion site in a flaky manner to remove fungi more thoroughly. However, the skin can recover to be normal state after treatment and there was no evident skin irritation found in [Ch][Ger] group. The ILs may offer promising opportunities to deliver anti-fungal drugs to treat inner skin fungal infections by synergistic action.

An advanced molecularly imprinted electrochemical sensor for the highly sensitive and selective detection and determination of Human IgG

An advanced molecularly imprinted electrochemical sensor with high sensitivity and selectivity for the detection of Human immunoglobulin G (IgG) was successfully constructed. With acrylamide imprinting systems, surface imprinting on the nanoparticles CuFe₂O₄ targeted at IgG was employed to prepare molecularly imprinted polymer, which served as recognition element for the electrochemical sensor. Furthermore, the sensor harnessed a molybdenum disulfide (MoS₂)@nitrogen doped graphene quantum dots (N-GQDs) with ionic liquid (IL) nanocomposite for signal amplification. Under optimized experimental conditions, the sensor shortened the response time to less than 8 min, and the response was linear at the IgG concentration of 0.1-50 ng·mL^-1 with a low detection limit of 0.02 ng·mL^-1 (S/N = 3). Our findings suggested that, the sensor exhibited high detectability and long-time stability. The satisfactory results of human serum sample analysis showed that the developed IgG sensor had promising potential clinical applications in detecting IgG content.