Chemotherapeutic cytotoxic agents such as paclitaxel (PTX) are considered essential for the treatment of various cancers. However, PTX injection is associated with severe systemic side effects and high rates of patient noncompliance. Micelle formulations (MFs) are nano-drug delivery systems that offer a solution to these problems. Herein, we report an advantageous carrier for the transdermal delivery of PTX comprising a new MF that consists of two biocompatible surfactants: cholinium oleate ([Cho][Ole]), which is a surface-active ionic liquid (SAIL), and sorbitan monolaurate (Span-20). A solubility assessment confirmed that PTX was readily solubilized in the SAIL-based micelles via multipoint hydrogen bonding and cation-π and π-π interactions between PTX and SAIL[Cho][Ole]. Dynamic light scattering (DLS) and transmission electron microscopy revealed that in the presence of PTX, the MF formed spherical PTX-loaded micelles that were well-distributed in the range 8.7-25.3 nm. According to DLS, the sizes and size distributions of the micelle droplets did not change significantly over the entire storage period, attesting to their physical stability. In vitro transdermal assessments using a Franz diffusion cell revealed that the MF absorbed PTX 4 times more effectively than a Tween 80-based formulation and 6 times more effectively than an ethanol-based formulation. In vitro and in vivo skin irritation tests revealed that the new carrier had a negligible toxicity profile compared with a conventional ionic liquid-based carrier. Based on these findings, we believe that the SAIL[Cho][Ole]-based MF has potential as a biocompatible nanocarrier for the effective transdermal delivery of poorly soluble chemotherapeutics such as PTX.
Coronavirus disease 2019 (COVID-19) has spread across the world, and no specific antiviral drugs have yet been approved to combat this disease. Favipiravir (FAV) is an antiviral drug that is currently in clinical trials for use against COVID-19. However, the delivery of FAV is challenging because of its limited solubility, and its formulation is difficult with common organic solvents and water. To address these issues, four FAV ionic liquids (FAV-ILs) were synthesized as potent antiviral prodrugs and were fully characterized by nuclear magnetic resonance (NMR) spectroscopy, Fourier-transform infrared (FT-IR) spectrometry, powder X-ray diffraction (PXRD), thermogravimetric analysis (TGA), derivative thermogravimetry (DTG), and differential scanning calorimetry (DSC). The aqueous solubility and in vivo pharmacokinetic properties of the FAV-ILs were also evaluated. The FAV-ILs exhibited improved aqueous solubility by 78 to 125 orders of magnitude when compared with that of free FAV. Upon oral dosing in mice, the absolute bioavailability of the β-alanine ethyl ester FAV formulation was increased 1.9-fold compared with that of the control FAV formulation. The peak blood concentration, elimination half-life, and mean absorption time of FAV were also increased by 1.5-, 2.0-, and 1.5-fold, respectively, compared with the control. Furthermore, the FAV in the FAV-ILs exhibited significantly different biodistribution compared with the control FAV formulation. Interestingly, drug accumulation in the lungs and liver was improved 1.5-fold and 1.3-fold, respectively, compared with the control FAV formulation. These results indicate that the use of ILs exhibits potential as a simple, scalable strategy to improve the solubility and oral absorption of hydrophobic drugs, such as FAV.
Human skin contains numerous antigen-presenting cells that are a potential target for several immune-based therapies, including vaccination and cancer immunotherapy. However, the outermost layer of the skin-the stratum corneum-acts as a major physical barrier against the permeation of antigens that have a molecular weight > 500 Da. In this study, an ionic liquid-assisted delivery system (ILDS) was developed, which enabled the successful transdermal delivery of an antigenic protein, ovalbumin (OVA), with a toll-like receptor agonist, imiquimod, as an adjuvant, to stimulate a specific immune response. Both the ionic liquids and ILDS were completely biocompatible for topical or transdermal application for therapeutic purposes. The skin permeation of the antigenic protein and adjuvant was found to be significantly enhanced because of the incorporation of a surface-active ionic liquid in the ILDS. An in vivo immunization study showed that there was a high level of OVA-specific IgG antibody production because of the enhanced permeation of the antigen and adjuvant across and into the skin. In a preclusive anticancer study, vaccination through ILDS showed stronger tumor-growth inhibition compared to control group. These results indicated that the ILDS could be a promising strategy for transdermal immunization as future therapeutics.
Oral delivery of the sparingly soluble drug methotrexate (MTX) is challenging owing to its poor bioavailability and low solubility. To address this challenge, the present study reports the conversion of MTX into a series of five ionic liquids (ILs) comprising a cationic component-i.e., cholinium (Cho), tetramethylammonium (TMA), tetrabutylphosphonium (TBP), or an amino acid ester-and an anionic component-i.e., MTX. The biocompatibility, pharmacokinetics, tissue distribution, and antitumor efficacy of each MTX-based IL were investigated to determine its usefulness as a pharmaceutical. Oral administration to mice revealed that proline ethyl ester MTX (IL[ProEt][MTX]) had 4.6-fold higher oral bioavailability than MTX sodium, followed by aspartic diethyl ester MTX, IL[TBP][MTX], IL[Cho][MTX], and IL[TMA][MTX]. The peak plasma concentration, elimination half-life, area under the plasma concentration, mean absorption time, and body clearance of IL[ProEt][MTX] were significantly (p
Paclitaxel (PTX) injection (i.e., Taxol) has been used as an effective chemotherapeutic treatment for various cancers. However, the current Taxol formulation contains Cremophor EL, which causes hypersensitivity reactions during intravenous administration and precipitation by aqueous dilution. This communication reports the preliminary results on the ionic liquid (IL)-based PTX formulations developed to address the aforementioned issues. The formulations were composed of PTX/cholinium amino acid ILs/ethanol/Tween-80/water. A significant enhancement in the solubility of PTX was observed with considerable correlation with the density and viscosity of the ILs, and with the side chain of the amino acids used as anions in the ILs. Moreover, the formulations were stable for up to 3 months. The driving force for the stability of the formulation was hypothesized to be the involvement of different types of interactions between the IL and PTX. In vitro cytotoxicity and antitumor activity of the IL-based formulations were evaluated on HeLa cells. The IL vehicles without PTX were found to be less cytotoxic than Taxol, while both the IL-based PTX formulation and Taxol exhibited similar antitumor activity. Finally, in vitro hypersensitivity reactions were evaluated on THP-1 cells and found to be significantly lower with the IL-based formulation than Taxol. This study demonstrated that specially designed ILs could provide a potentially safer alternative to Cremophor EL as an effective PTX formulation for cancer treatment giving fewer hypersensitivity reactions.
Ionic liquid (IL) surfactants have attracted great interest as promising substitutes for conventional surfactants owing to their exceptional and favorable physico-chemical properties. However, most IL surfactants are not eco-friendly and form unstable micelles, even when using a high concentration of the surfactant. In this study, we prepared a series of halogen-free and biocompatible choline-fatty-acid-based ILs with different chain lengths and degrees of saturation, and we then investigated their micellar properties in aqueous solutions. Characterization of the synthesized surface-active ILs (SAILs) was performed by 1H and 13C nuclear magnetic resonance spectroscopy, Fourier transform infrared spectroscopy, differential scanning calorimetry, and elemental analysis. The surface-active properties of the SAILs were investigated by tensiometry, conductometry, and dynamic light scattering measurements. The critical micelle concentration of the SAILs was found to be 2-4 times lower than those of conventional surfactants. The thermodynamic properties of micellization (ΔG0m, ΔH0m, and ΔS0m) indicate that the micellization process of the SAILs is spontaneous, stable, and entropy-driven at room temperature. The cytotoxicity of the SAILs was evaluated using mammalian cell line NIH 3T3. Importantly, [Cho][Ole] shows lower toxicity than the analogous ILs with conventional surfactants. These results clearly suggest that these environmentally friendly SAILs can be used as a potential alternative to conventional ILs for various purposes, including biological applications.
We report a one-step emulsification and rapid freeze-drying process to develop a curcumin-ionic liquid (CCM-IL) complex that could be readily dispersed in water with a significantly enhanced solubility of ∼8 mg mL-1 and half-life (t1/2) of ∼260 min compared with free CCM (solubility ∼30 nM and t1/2 ∼ 20 min). This process using an IL consisting of a long chain carbon backbone as a surfactant, may provide an alternative way of enhancing the solubility of poorly water-soluble drugs.
In order to prevent common hypersensitivity reactions to paclitaxel injections (Taxol), we previously reported an ionic liquid-mediated paclitaxel (IL-PTX) formulation with small particle size and narrow size distribution. The preliminary work showed high PTX solubility in the IL, and the formulation demonstrated similar antitumor activity to Taxol, while inducing a smaller hypersensitivity effect in in vitro cell experiments. In this study, the stability of the IL-PTX formulation was monitored by quantitative HPLC analysis, which showed that IL-PTX was more stable at 4 °C than at room temperature. The in vivo study showed that the IL-PTX formulation could be used in a therapeutic application as a biocompatible component of a drug delivery system. To assess the in-vivo biocompatibility, IL or IL-mediated formulations were administered intravenously by maintaining physiological buffered conditions (neutral pH and isotonic salt concentration). From in vivo pharmacokinetics data, the IL-PTX formulation was found to have a similar systemic circulation time and slower elimination rate compared to cremophor EL mediated paclitaxel (CrEL-PTX). Furthermore, in vivo antitumor and hypersensitivity experiments in C57BL/6 mice revealed that IL-PTX had similar antitumor activity to CrEL-PTX, but a significantly smaller hypersensitivity effect compared with CrEL-PTX. Therefore, the IL-mediated formulation has potential to be an effective and safe drug delivery system for PTX.
The technological utility of active pharmaceutical ingredients (APIs) is greatly enhanced when they are transformed into ionic liquids (ILs). API-ILs have better solubility, thermal stability, and the efficacy in topical delivery than solid or crystalline drugs. However, toxicological issue of API-ILs is the main challenge for their application in drug delivery. To address this issue, 11 amino acid esters (AAEs) were synthesized and investigated as biocompatible counter cations for the poorly water-soluble drug salicylic acid (Sal) to form Sal-ILs. The AAEs were characterized using 1H and 13C NMR, FTIR, elemental, and thermogravimetric analyses. The cytotoxicities of the AAE cations, Sal-ILs, and free Sal were investigated using mammalian cell lines (L929 and HeLa). The toxicities of the AAE cations greatly increased with inclusion of long alkyl chains, sulfur, and aromatic rings in the side groups of the cations. Ethyl esters of alanine, aspartic acid, and proline were selected as a low cytotoxic AAE. The cytotoxicities of the Sal-ILs drastically increased compared with the AAEs on incorporation of Sal into the cations, and were comparable to that of free Sal. Interestingly, the water miscibilities of the Sal-ILs were higher than that of free Sal, and the Sal-ILs were miscible with water at any ratio. A skin permeation study showed that the Sal-ILs penetrated through skin faster than the Sal sodium salt. These results suggest that AAEs could be used in biomedical applications to eliminate the use of traditional toxic solvents for transdermal delivery of poorly water-soluble drugs.