Multifunctional Deep Eutectic Solvent-Based Microemulsion for Transdermal Delivery of Artemisinin.

As a serious public health issue, malaria threatens the health of millions of people. Artemisinin, a gift from traditional Chinese medicine, has been used in the treatment of malaria and has shown good therapeutic efficiency. However, due to its low solubility, poor bioavailability, and short half-life time, some smart delivery strategies are still required. Herein, a multifunctional DES prepared from ibuprofen and menthol was prepared. This DES was shown to efficiently promote the solubility of artemisinin up to 400-fold. Then, it was further applied as the oil phase to construct an O/W microemulsion with the help of Tween-80 + Span-20 mixed surfactants. The prepared microemulsion displayed high efficiency in improving the permeability of artemisinin, which can be ascribed to the presence of the permeation enhancer menthol in DES and the microstructure of the O/W microemulsion. Moreover, the simultaneous permeation of artemisinin and ibuprofen further indicated the potential benefits of the presented formulation in the treatment of malaria. To sum up, the microemulsion based on multifunctional DES presented herein provided an effective method for transdermal delivery of artemisinin.

Ionic liquids as effective additives to enhance the solubility and permeation for puerarin and ferulic acid.

Ionic liquids, especially the cholinium-amino acid-based ionic liquids (CHAAILs), have recently been found to be effective ingredients in formulation of transdermal drug delivery system. In this work, we synthesized six CHAAILs, and investigated their ability to enhance the solubility and permeation of two active pharmaceutic ingredients (APIs), i.e. ferulic acid and puerarin. The solubility measurements showed that a low amount of CHAAILs can significantly increase the solubility of APIs. Moreover, the effective enhancement of permeation of APIs across a polyethersulfone (PES) membrane was achieved at low concentration (4 mg ml-1) of CHAAILs. It is more worthwhile that the presence of CHAAIL brings much less cytotoxicity as compared to traditional types of ionic liquids. Therefore, CHAAILs can be considered as great potential candidates of green and effective additives in transdermal drug delivery systems.

Amphiphilic Deep Eutectic Solvent Based on Lidocaine and Lauric Acid: Formation of Microemulsion and Gel.

Deep eutectic solvent (DES), as a new type of promising green solvent, showed great advantages of easy preparation and no need for purification after synthesis and displayed great potential applications in various fields. Herein, we have constructed a new type of therapeutic DES based on lidocaine and lauric acid. The DES displayed good surface activity in constructing a nonaqueous microemulsion with 1,2-propanediol (PG) and isopropyl myristate (IPM) being the polar phase and nonpolar phase, respectively. The obtained nonaqueous microemulsion displayed a structural transition from W/O type to O/W type via a bicontinuous structure with an increase of the PG content. The size, morphology, and microstructure of the microemulsion were explored using dynamic light scattering (DLS), transmission electron microscopy (TEM), and UV-vis absorption spectra measurements. Furthermore, this novel DES can act as a gelator to form a gel in a certain water content range. The rheological measurements suggested the presence of a strong colloidal force. Therefore, the results presented herein were expected to provide a new perspective in the applications of deep eutectic solvent as a surfactant.

[Effects of ropivacaine hydrochloride on the proliferation, invasion and apoptosis of osteosarcoma cells and its mechanism].

Objective: To investigate the effects and molecular mechanism of ropivacaine hydrochloride on osteosarcoma cell proliferation, invasion, and apoptosis. Methods: The osteosarcoma doxorubicin-resistant cell line (U2OS/DOX) was established by gradually increasing the drug doses. U2OS/DOX cells were treated with ropivacaine hydrochloride at the concentrations of 0, 20, 50 and 100 µg/ml, respectively; as different concentrations treatment groups of ropivacaine hydrochloride. pcDNA3.1 and pcDNA3.1-Livin were transfected into U2OS/DOX cells and then treated with 100 µg/ml ropivacaine hydrochloride, which were defined as ropivacaine hydrochloride 100 µg/ml+pcDNA3.1 group, ropivacaine hydrochloride 100 µg/ml+pcDNA3.1-Livin group. MTT was used to detect the cell proliferation inhibition rate and inhibitory concentration (IC50). Western blot was used to detect the expressions of cyclin-dependent kinase inhibitor 1A (P21) and activated cysteine aspartic protease-3 (Cleaved Caspase-3), E-cadherin, matrix metalloproteinase 2 (MMP-2) and Livin; clone formation experiments were used to detect the number of cell clones formed; flow cytometry was used to detect apoptosis; Transwell was used to detect cell migration and invasion; real-time fluorescent quantitative PCR (RT-qPCR) was used to detect Livin mRNA expression. Results: When the concentration of doxorubicin was more than 1 µg/ml, the proliferation inhibition rate of osteosarcoma cells U2OS was significantly increased in a concentration-dependent manner (P＜0.05); when the concentration of doxorubicin was more than 10 µg/ml, the proliferation inhibition rate of osteosarcoma resistant cell U2OS/DOX was significantly increased, and it was dose-dependent (P＜0.05). In U2OS/DOX cells treated with ropivacaine hydrochloride, the expressions of P21, Cleaved Caspase-3, and E-cadherin were increased significantly, the expression of MMP-2 was decreased significantly, the cell proliferation inhibition rate was increased significantly, the number of colony formation was decreased significantly, and the cells apoptosis rate was increased significantly, the number of cell migration and invasion was decreased significantly, and the expression of Livin was significantly reduced, in a concentration-dependent manner (P＜0.05). Overexpression of Livin partially reversed the inhibitory effect of ropivacaine hydrochloride on proliferation, migration, invasion, and promotion effect on apoptosis of cell U2OS/DOX. Conclusion: Ropivacaine hydrochloride can significantly inhibit the proliferation, migration and invasion of doxorubicin-resistant osteosarcoma cells, and significantly promote osteoma cell apoptosis. The mechanism may be related to Livin.

Eutectic-based liposome as a potential delivery system of paeonol.

Deep eutectic solvents (DESs), as a new type of green solvent, show great advantages of easy preparation and no need of purification after synthesis and have great potential applications in various fields. Moreover, when combining active pharmaceutical ingredients (APIs) with DESs, a new type of drug delivery system called a therapeutic deep eutectic solvent (THEDES) can be developed to increase the solubility of the APIs and/or their permeation ability as well as bioactivity. Herein, we have designed a new THEDES based on paeonol and lauric acid with a molar ratio of 1 : 1. The physicochemical properties as well as the bioactivity were investigated by a series of techniques. The THEDES showed better solubility in water and similar bioactivities as compared to the pure APIs. Besides, we further prepared a THEDES liposome, which possessed an average size of about 120 nm with an encapsulation efficiency of 84%. The obtained liposome showed good stability during the experimental period, which indicated a potential application for the delivery of paeonol. The results presented herein suggested that THEDES may be regarded as a new strategy for the effective delivery of APIs.

Influence of amphiphilic molecules on the peroxidase-like behavior of nanoparticles in an aqueous solution.

Carbon dots (CDs) have drawn considerable attention in recent decades due to their outstanding biocompatibility and environmental friendliness. In this study, we synthesized ionic liquid (1-aminopropyl-3-methyl-imidazolium bromide)-modified carbon dots (IL-CDs) showing good peroxidase-like activity. Furthermore, we investigated their enzymic behavior in the presence of two different amphiphilic molecules, namely tert-butanol (TBA, a typical hydrotrope) and sodium bis (2-ethylhexyl) sulfosuccinate (AOT, a typical anionic surfactant). In an aqueous solution of TBA, a microscopic heterogeneous structure was formed in a certain concentration range of TBA, which resulted in an anomaly in the reaction process. However, in the AOT aqueous solution, the situation became more complicated. IL-CDs formed vesicles or precipitation at different concentrations of AOT, which led to different enzymic activities of IL-CDs due to the variance in the structure and the surface electronic density.

Effect of surface modification on the peroxidase-like behaviors of carbon dots.

Carbon dots (CDs) have drawn much attention in recent decades due to their outstanding biocompatibility and environmental friendliness. In this work, the surface modifications of peroxidase-like carbon dots were carried out to show the influence of surface structure on the catalytic activity. Poly(ethyleneimine) and citric acid modified CDs, i.e. PEI-CDs and CA-CDs, were obtained and used in the catalytic oxidation of two different substrates 3,3',5,5'-tetramethylbenzidine (TMB) and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS). The catalytic activity of CA-CDs for TMB is greater than that of unmodified CDs while the catalytic activity of PEI-CDs for ABTS is greater than that of unmodified CDs. These results may be ascribed to that TMB shows stronger affinity to negatively charged CA-CDs and ABTS shows stronger affinity to positively charged PEI-CDs. These results clearly suggested that the surface charge plays an important role in the catalytic activity of nanoenzyme. Furthermore, the mechanism of peroxidase-like activity of all CDs was investigated and both the generation of hydroxyl radical and enhanced electron transfer were involved in the catalytic process.

Liquid-liquid phase equilibrium and the effect of a water-soluble polymer on the interaction between droplets in water-in-oil microemulsions.

The liquid-liquid phase equilibria of {water/PEG200/sodium bis(2-ethylhexyl)sulfosuccinate (AOT)/n-decane} with the molar ratio of water to AOT being 37.9 and various concentrations cPEG of PEG in water were measured in this study. The critical exponent ß corresponding to the width of the coexistence curve was determined, which showed good agreement with the 3D-Ising value and supported the proposal of the pseudo binary droplet solution for these multiple microemulsions. A previously developed thermodynamic approach based on the Carnahan-Starling-van der Waals type equation was improved and used to analyze the coexistence curve data of {water/PEG200/AOT/n-decane} microemulsions to deduce the interaction properties between droplets and further to investigate the effect of the additive PEG200 on these interactions. It was found that the addition of PEG200 into the {water/AOT/n-decane} microemulsion resulted in the decrease in the critical temperature and the interaction enthalpy and entropy. Both the interaction enthalpy and entropy decreased first, then increased with an increase of cPEG and had minimum values at cPEG = 25 g L-1, which showed the same tendency as the isothermal titration microcalorimetric results for the {water/PEG200/AOT/isooctane} microemulsion we reported very recently. The effects of the interaction enthalpy and the entropy on the phase separation and their dependences on cPEG were discussed and related to the effects of the additive on the rigidity of the interface layer of the microemulion droplet.

The heat capacities and critical behaviors of binary ionic solutions.

The heat capacities of nine binary room temperature ionic solutions {[C4mim][BF4] + 1,2-butandiol}, {[C8mim][BF4] + 1-pentanol}, {[C8mim][BF4] + 2-pentanol}, {[C8mim][BF4] + 1-hexanol}, {[C8mim][BF4] + 1-heptanol}, {[C8mim][PF6] + 1-propanol}, {[C8mim][PF6] + 1-butanol}, {[C8mim][PF6] + 2-butanol} and {[C8mim][PF6] + tert-butanol} are reported herein. The combination of the data obtained with the corresponding measured coexistence curves infers that the critical asymmetry parameter of the coexistence curves linearly varies with the molar volume ratio of the two components for each of the studied binary ionic solutions after the heat capacity contribution is considered. This indicates the importance of the heat capacity contribution to the critical asymmetry. For further analysis of the critical characteristics of the ionic solutions, a large amount of experimental data was collected and systematically discussed in detail regarding which critical character is important in the binary ionic solutions. A general increasing tendency for the RPM (restricted primitive model)-rescaled critical parameters with the relative permittivity εr,c of the solvent at the critical temperature of the corresponding system was found. This is attributed not only to the screening effect of the solvent medium, but also to solvophobic interactions, which both increase with εr,c. This study also demonstrates that the critical amplitudes increased, while the relative contribution of the heat capacity to the asymmetry of the coexistence curve decreased with an increase in εr,c.

Critical universality and asymmetry of ionic solution {iodobenzene + 1-decyl-3-methyl-imidazolium bis(trifluorosulfonyl)imide}.

The liquid-liquid coexistence curve, heat capacity in the critical and noncritical regions, and the turbidity in critical one-phase and two-phase regions of the binary solution {iodobenzene + 1-decyl-3-methylimidazolium bis(trifluorosulfonyl)imide ([C10mim][NTf2])} have been precisely measured. From the data collected in the critical region, the critical exponents α, ß, γ and ν, as well as the universal critical amplitude ratios RB and X were obtained and were shown to agree well with their theoretical values for the 3D-Ising universality class, which further confirmed the 3D-Ising criticality of ionic solutions even in a very low relative permittivity solvent. The coulombic character of the studied system was suggested by the small values of the RPM reduced critical temperature and density. Furthermore, it was found that both the asymmetric behaviors of the diameter of the coexistence curve and the osmotic compressibility could be well described using the complete scaling theory.

Liquid-Liquid Phase Equilibria and Interactions between Droplets in Water-in-Oil Microemulsions.

The liquid-liquid phase equilibria of [water/sodium bis(2-ethylhexyl)sulfosuccinate (AOT)/n-decane] with the molar ratio w0 of water to AOT being 37.9 and [water/AOT/ethoxylated-2,5,8,11-tetramethyl-6-dodecyne-5,8-diol(Dynol-604)/n-decane] with w0 = 37.9 and the mole fraction α of Dynol-604 in the total surfactants being 0.158 were measured in this study. From the data collected in the critical region, the critical exponent ß corresponding to the width of the coexistence curve was determined, which showed good agreement with the 3D-Ising value. A thermodynamic approach based on the Carnahan-Starling-van der Waals type equation was proposed to describe the coexistence curves and to deduce the interaction properties between droplets in the microemulsions. The interaction enthalpies were found to be positive for the studied systems, which evidenced that the entropy effect dominated the phase separations as the temperature increased. The addition of Dynol-604 into the (water/AOT/n-decane) microemulsion resulted in the decrease in the critical temperature and the interaction enthalpy. Combining the liquid-liquid equilibrium data for (water/AOT/n-decane) microemulsions with various w0 values determined previously, it was shown that the interaction enthalpy decreased with w0 and tended to change its sign at low w0, which coincided with the results from the isothermal titration calorimetry investigation. All of these behaviors were interpreted by the effects of entropy and enthalpy and their competition, which resulted from the release of solvent molecules entrapped in the interface of microemulsion droplets and were dependent on the rigidity of the surfactant layers and the size of the droplet.

Structural rearrangement in the aqueous solution of surface active ionic liquid 1-butyl-3-methylimidazolium bis(2-ethylhexyl) sulfosuccinate.

The aggregation behaviors of surface active ionic liquid 1-butyl-3-methylimidazolium bis(2-ethylhexyl) sulfosuccinate in aqueous solutions were investigated by conductometry, densimetry, fluorimetry, (1)H nuclear magnetic resonance ((1)H NMR) spectroscopy, dynamic light scattering (DLS), and transmission electron microscopy (TEM), which confirmed two distinguished critical concentrations. The first critical concentration was believed to be the critical aggregation concentration (CAC), where two different types of aggregates were formed, namely, micelles with the size of 10 nm and vesicles with the size of 100 nm. The second critical concentration at two-fold CAC was suggested to be resulting from the insertion of the imidazolium cations into aggregates.

Effects of water content and chain length of n-alkane on the interaction enthalpy between the droplets in water/sodium bis(2-ethylhexyl)-sulfosuccinate/n-alkane microemulsions.

The concentration-dependent enthalpies of mixing for water/sodium bis(2-ethylhexyl)-sulfosuccinate (AOT)/n-alkane microemulsions with different water contents ω0 and chain lengths n of n-alkane were determined by isothermal titration microcalorimetry (ITC) and flow-mixing microcalorimetry at 298.15 K and used to calculate the interaction enthalpies (-ΔH(C)) between the droplets. It was found that -ΔH(C) increased with ω0, and changed from negative to positive at about ω0 = 10. The investigation of the dependence of -ΔH(C) on n revealed that the values of -ΔH(C) were negative and had a minimum for ω0 = 5; while they were positive and had a maximum for ω0 = 15. These phenomena were discussed based on the competition of the overlapping contribution of the surfactant tails between two neighbouring droplets and the penetration contribution of the solvent molecules into the surfactant tails. These results indicated the important role of entropy in the stability of the microemulsion systems.

Volumetric properties of water/AOT/isooctane microemulsions.

The densities of AOT/isooctane micelles and water/AOT/isooctane microemulsions with the molar ratios R of water to AOT being 2, 8, 10, 12, 16, 18, 20, 25, 30, and 40 were measured at 303.15 K. The apparent specific volumes of AOT and the quasi-component water/AOT at various concentrations were calculated and used to estimate the volumetric properties of AOT and water in the droplets and in the continuous oil phase, to discuss the interaction between the droplets, and to determine the critical micelle concentration and the critical microemulsion concentrations. A thermodynamic model was proposed to analysis the stability boundary of the microemulsion droplets, which confirms the maximum value of R being about 65 for the stable AOT/water/isooctane microemulsion droplets.

Solvent dependent interactions between droplets in water-in-oil microemulsions.

In this paper, we investigated the dilution enthalpies of the droplets in water/AOT/oil microemulsions with oil being isooctane, decane, or cyclohexane by isothermal titration microcalorimetry (ITC). Combining with the results obtained from the study of the water/AOT/toluene system in our previous work, it was found that the enthalpy interactions between droplets for isooctane and decane systems were repulsive, while the enthalpy interactions were attractive for cyclohexane and toluene systems. The repulsive droplet interaction for the isooctane system was also confirmed by static light scattering. The solvents appear to play important roles in varying the droplet enthalpy interactions from positive to negative, and the entropy contribution seems to be dominant for the stability of these microemulsion droplet systems.

Asymmetric criticality of binary ionic solutions containing 1-butyl-3-methylimidazolium tetrafluoroborate and alcohol.

The liquid-liquid coexistence curves for binary solutions {1-butyl-3-methylimidazolium tetrafluoroborate ([C4mim][BF4]) + 1-propanol} and {1-butyl-3-methylimidazolium tetrafluoroborate ([C4mim][BF4]) + 2-propanol} have been precisely measured. The values of the critical exponents ß obtained from the liquid-liquid equilibrium data in the critical region confirmed the 3D-Ising universality. The isobaric heat capacities per unit volume were measured for {[C4mim][BF4] + 1-propanol (or 2-propanol, 1,3-propanediol, 1,4-butanediol)} in both critical and non-critical regions. The experimental results indicate a major solvophobic contribution to the criticality for the studied ionic solutions. The complete scaling theory was applied to well represent the asymmetric behavior of the diameter of the coexistence curves with the consideration of the heat capacity contribution. It was found that the contribution of the heat capacity related term in the ionic solution decreased with the increase of the permittivity of alcohol and was more important in the description of the asymmetry of the coexistence curve of the ionic solutions than that of the molecular solutions.

The interactions of ι-carrageenan with cationic surfactants in aqueous solutions.

The interactions between the anionic polymer ι-carrageenan (IC) and the cationic surfactants 1-dodecyl-3-methylimidazolium bromide (C12mimBr), dodecyltrimethylammonium bromide (DTAB) and ethyl-α,ω-bis(dodecyldimethylammonium)dibromide (12-2-12) have been studied by fluorimetry and isothermal titration calorimetry. Our experimental results showed that at a low surfactant concentration, the monomers adsorbed on the IC chains through the electrostatic attraction, followed by the formation of induced micelles on the IC chains through the hydrophobic interaction until the IC chains are saturated by surfactant molecules; after that the added surfactant formed free micelles in the solution. A pseudo-phase-equilibrium thermodynamic model was proposed to explain the experimental results and to understand the mechanisms of the interactions in these three systems. Moreover, the salt effect on the interactions was investigated and found that it changed the critical concentrations but not the interaction mechanism.

Thermodynamics of mixed surfactant solutions of N,N'-bis(dimethyldodecyl)-1,2-ethanediammoniumdibromide with 1-dodecyl-3-methylimidazolium bromide.

Mixed surfactant solutions are studied to understand their synergistic effects. Here we report the micellization properties of mixed surfactant solutions of the gemini surfactant N,N'-bis(dimethyldodecyl)-1,2-ethanediammoniumdibromide (12-2-12) with the imidazolium ionic liquid 1-dodecyl-3-methylimidazolium bromide (C12mimBr) investigated by isothermal titration calorimetry (ITC), conductometry, fluorimetry, and dynamic light scattering (DLS). A two-parameter Margules model was successfully used to correlate the cmc values and calculate the compositions and activity coefficients of the two components in the mixed micelle phase for 12-2-12/C12mimBr aqueous solutions with different overall surfactant compositions. The dissociation degree of counterion, the thermodynamic quantities of micellization, and the excess thermodynamic quantities for the mixed micelle were calculated and discussed. The ITC experiment in the low overall surfactant composition region showed a second phase transition. A thermodynamic model was proposed to explore phase behaviors of two different types of micelle and their solution, which was further confirmed by fluorescence and DLS studies.

Asymmetric criticality of the osmotic compressibility in binary mixtures.

Heat capacities in the critical and the non-critical regions for {benzonitrile + tridecane} and {benzonitrile + pentadecane}, and light scattering for {benzonitrile + undecane}, {benzonitrile + dodecane}, {benzonitrile + tridecane}, {benzonitrile + tetradecane}, {benzonitrile + pentadecane}, and {benzonitrile + hexadecane} in the critical two-phase region were measured. Light scattering measurements confirmed the existence of the asymmetry for the osmotic compressibility while no such asymmetry was observed for the correlation length. An analysis of the osmotic compressibility asymmetry suggested the dominance of the singular term |ΔT[circumflex]|(ß), which supports the complete scaling theory. The consistency of the complete scaling theory in descriptions of different asymmetry behaviors was also discussed. Moreover, it was found that the contribution of the heat capacity-related term is also important in describing the asymmetry of the osmotic compressibility as it was observed in studies of the diameters of the coexistence curves.

Determination of the interaction enthalpy between microemulsion droplets by isothermal titration microcalorimetry.

A new experimental design for the measurement of the real heat of dilution of the microemulsion droplets by isothermal titration microcalorimetry (ITC) has been reported and used to study the interaction enthalpies of the droplets for the system of water/sodium bis(2-ethylhexyl)-sulfosuccinate (AOT)/toluene. The results are in good agreement with those determined from light-scattering experiments.