Water Solubilization Capacity Research Articles

Phase behavior of multi-stimuli-responsive ionic liquids-based micro-emulsion and its application in nano silica synthesis and curcumin encapsulation

The enrichment and separation of trace compounds, as well as the preparation of nanomaterials, are all greatly facilitated by responsive micro-emulsion. A multi stimuli-responsive ionic liquids-based micro-emulsion system was established with alkyl-N-Tropine (trans) P-methoxycinnamate ([CnTr][PMCA], TILS) as a surfactant. The factors affecting the phase behavior of micro-emulsion, such as the structure of the TILS, cosurfactant, oil, temperature, pH, and salinity, were investigated by multiple research methods. Five zones were identified inside the micro-emulsion phase region as O/W, B.C., liquid crystal (L.C.), L.C.+B.C., and W/O. The TILS-based micro-emulsion displayed high stability at measured temperatures. High salinity contributed to a higher water solubilization capacity of the micro-emulsion. For the potential applications of the micro-emulsion, with sizes ranging from 20 to 70 nm, nanoscale silica particles showed persistent stability. High levels of drug loading rate (about 8.6 mg·g−1) and encapsulation efficiency (about 99%) of the micro-emulsion loaded with curcumin were attained.

Self-emulsifying drug delivery systems with atorvastatin adsorbed on solid carriers: formulation and in vitro drug release studies

Two novel self-emulsifying drug delivery systems (SEDDS) with atorvastatin calcium, an anti-hyperlipidemic drug, were obtained and adsorbed on different solid inorganic carriers. In order to determine the parameters affecting the drug release process, different physicochemical analyses were performed. Liquid SEDDS were investigated for water solubilization capacity, viscosity and surface tension. In the case of solid materials, differential scanning calorimetry and scanning electron microscopy were conducted in order to check the samples for the presence of drug crystals. The interactions between the components of the materials were analyzed with inverse gas chromatography and Flory-Huggins parameters were calculated. The drug release experiments performed for all investigated formulations revealed that after the initial quick release the drug concentration in the dissolution medium decreased slightly which might be related to the crystallization process. However, the level of the released active ingredient was maintained at 80% for most formulations. It was also shown that the results of drug dissolution studies were independent of the measured physicochemical parameters, even though some clear differences have been observed between the analyzed materials.

Formation of 1-Butyl-3-methylimidazolium Bis(2-ethyl-1-hexyl)sulfosuccinate Stabilized Water-in-1-Butyl-3-methylimidazolium Bis(trifluoromethanesulfonyl)imide Microemulsion and the Effects of Additives

A new strategy is proposed here to formulate a bis(2-ethyl-1-hexyl)sulfosuccinate (AOT−) stabilized water-in-ionic liquid microemulsion without any additives. Replacing the inorganic counter ion Na+ by the organic 1-butyl-3-methylimidazolium ([Bmim]+) ion greatly improves the solubility of AOT− in hydrophobic 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([Bmim]Tf2N) (IL) and favors the formation of water-in-IL (W/IL) microdroplets. The existence of the W/IL microdroplets has been confirmed by dynamic light scattering, Fourier transform infrared absorption spectroscopy and ultraviolet–visible absorption spectroscopy. Also, presented for the first time are the effects of salts and alcohols on the microstructure and water solubilization capacity of the ternary H2O/[Bmim]AOT/[Bmim]Tf2N system. For inorganic salts, larger concentrations of the salt and higher charge density of the cation result in smaller microdroplet size and weak water solubilization capacity. For 1-hexanol, a high concentration of this alcohol results in small microdroplet size but high water solubilization capacity. Analyses indicate that the salts compress the electric double layers of W/IL microemulsions, decrease the size of the microdroplets and consequently reduce the water solubilization capacity; the alcohol, however, facilitates the aggregation of AOT−, increases the number of W/IL microdroplets, and therefore improves the water solubilization capacity of the system.

Enhanced stability and water solubilizing capacity of water-in-oil microemulsions based on protic ionic liquids.

In an attempt to increase the stability and water uptake capacity of water-in-oil (W/O) microemulsions, here we study the physicochemical behavior of a series of protic ionic liquid based water/oil microemulsions, wherein solute amounts of biocompatible tetramethylguanidinium cation-based ionic liquids (ILs) are added to the aqueous phase of water-in-oil (W/O) microemulsions. FTIR and time-resolved fluorescence measurements showed an increased water uptake in these reverse micellar droplets, compared to conventional W/O microemulsions of similar compositions. Dynamic light scattering and differential scanning calorimetric measurements suggested greater thermal stability of the droplets in presence of the ILs. NMR and FTIR measurements and ab initio calculations explained these findings by showing an extended hydrogen bonding network between interfacial water and protic IL ions and strong electrostatic associations between the surfactant headgroups and IL anions. Our results pave the way for potential applications of protic ionic liquids in emulsion and microemulsion science and technology.

The mixing behaviour of anionic and nonionic surfactant blends in aqueous environment correlates in fatty acid ester medium

Mixtures of dissimilar surfactants can have superior properties compared to those of the individual surfactant components involved, which provide impetus for research on interactions between surfactants. It was also demonstrated that a change in the composition of external phase promotes remarkable changes in interfacial properties of reverse micelles (RMs), which are crucial to understand the system in order to use them as nanoreactors. Hence, it should be achievable to explore the influence of non-ionic Tween-85 on the properties of anionic AOT based micelle as well as RMs in fatty acid esters [e.g., ethyl myristate (EM), ethyl palmitate (EP) and ethyl oleate (EO)]. A comprehensive micellization behavior is studied at different mixed compositions (XTween-85) by surface tension method. Non-ideal mixing behaviors along with synergistic interaction between the constituent surfactants in the mixed micelles are evidenced. Mixed micelles illustrate favorable micellization behavior in terms of thermodynamic parameters. Further, fatty acid ester medium-based mixed RM shows synergism in water solubilization capacity. Microstructures of these systems are investigated by conductance, DLS, and FTIR studies. The solvation and rotational relaxation dynamics using picosecond time-resolved emission spectroscopy (TRES) is used to investigate the effect of XTween-85 as well as chemical architecture of fatty acid esters for the first time on the excited state dynamics of fluorophore. The solvation dynamics is found to be faster with an increase in XTween-85 and the average solvation time follows the order, EO<EP<EM, which collaborates well with droplet size and abundance of bulk-like water. Anisotropy studies reveal a decrease in the rotational restriction on the probe for EO based RMs. It is reasonable that this work have the potential to serve as good biomimicry models to study various processes occurring in biological molecules embedded in biomembranes.

The Formation of Rhamnolipid-Based Water-Containing Castor Oil/Diesel Microemulsions and Their Potentiality as Green Fuels

The utilization of vegetable oils as a source of renewable fuels has attracted much attention. However, the high viscosity of vegetable oils limits their long-term application. The microemulsion technique of vegetable oils has the advantages of viscosity reduction and environment-friendly properties. In this study, the phase behavior of the microemulsion and the solubilization mechanism of water and castor oil in diesel were researched to evaluate the solubilization capacity of water and castor oil in diesel under given conditions. The proper concentration of rhamnolipid (RL) was 50 g/L. N-octanol was certified as an ideal co-surfactant with the optimal co-surfactant/surfactant (C/S) mass ratio (w/w) of 0.60. The optimum castor oil/diesel (V/D) volume ratio (v/v) was 0.18. Moreover, fuel properties of water-containing castor oil/diesel (WCD) microemulsion were identified, including density, dynamic viscosity, cloud point, pour point, water content, corrosivity, heating value, and elemental composition. Th...

Formulation of Microemulsions Based on Sugar Surfactant as an Alternative Fuel

Microemulsion systems that serve as water in diesel fuel were formulated using minimum amount of sucrose laurate at 25°C. Comparative experiments were also conducted using n-heptane. It was found that in order to formulate diesel and microemulsions a cosurfactant should be added. Alcohols such as 1-butanol,1-pentanol, 1-hexanol, and 1-heptanol served as cosurfactants. The area of the one-phase microemulsion region varies depending on the cosurfactant structure and composition. A continuous microemulsion region was observed with 1-butanol and 1-pentanol. Water solubilization capacity and thermodynamics as a function of alcohol chain length was determined.

Water solubilization capacity of pharmaceutical microemulsions based on Peceol®, lecithin and ethanol

Biocompatible microemulsions composed of Peceol®, lecithin, ethanol and water developed for encapsulation of hydrophilic drugs were investigated. The binary mixture Peceol®/ethanol was studied first. It was shown that the addition of ethanol to pure Peceol® has a significant fluidifying and disordering effect on the Peceol® supramolecular structure with an enhancement in water solubilization. The water solubilization capacity was improved by adding lecithin as a third component. It was then demonstrated that the ethanol/lecithin weight ratio played an important role in determining the optimal composition in term of water solubilization efficiency, a necessary property for a nutraceutical or pharmaceutical application. The optimal ethanol/lecithin weight ratio in the Peceol® rich region was found to be 40/60. Combination different techniques such as SAXS, fluorimetry, rheology and conductivity, we analyzed the water uptake within the microemulsion taking into account the partitioning of ethanol between polar and apolar domains. This ethanol distribution quantified along a water dilution line has a major effect on microemulsion properties.

Effect of the alkyl chain length of a hydrophobic ionic liquid (IL) as an oil phase on the phase behavior and the microstructure of H2O/IL/nonionic polyoxyethylene surfactant ternary systems

The use of hydrophobic ionic liquids (ILs) as oil phases to formulate a H2O-in-IL (W/IL) microemulsion is of great significance to enzyme catalysis. In this report, we present the essential influence of the alkyl chain length of ILs on the phase behavior and the microstructure of H2O/IL/CnEm (polyoxyethylene alkyl ether) ternary systems. The ILs are [C4mim][PF6] (1-butyl-3-methylimidazolium hexafluorophosphate) and [C8mim][PF6] (1-octyl-3-methylimidazolium hexafluorophosphate). For a given nonionic surfactant, the alkyl chain length of ILs has an influence on the water solubilization capacity. The difference in the capacity, however, narrows and even disappears upon significant increase of the hydrophilic chain length of CnEm. FTIR spectroscopy and UV-Vis spectroscopy confirm the existence of bulk water in both [C4mim][PF6]- and [C8mim][PF6]-based C12E23-stabilized W/IL microemulsions. The catalytic activity of laccase hosted in the W/IL microemulsion and the dynamic light scattering measurement reveal that under the same conditions, the water droplet size dispersed in [C4mim][PF6] is larger than that in [C8mim][PF6]. To establish the newly developed W/IL microemulsion as an effective medium for laccase, a control study is presented, demonstrating that the W/IL microemulsion is superior to the pure ILs for the expression of the catalytic activity of laccase.

Physicochemical Characterization of Anionic and Cationic Microemulsions: Water Solubilization, Particle Size Distribution, Surface Tension, and Structural Parameters

The composition, oil type, and thermodynamic parameters influence the water solubilization capacity, particle size distribution, surface tension, and also the structural parameters of microemulsion systems. In the present study sodium lauryl sulfate (SLS) and hexadecyltrimethylammonium bromide (HTAB) have been used as surfactants and 3-methyl-1-butanol as cosurfactant to prepare microemulsions. Four n-alkanes (hexane, heptane, decane, and dodecane) were chosen as oil phases. Water solubilization capacities of anionic (SLS) and cationic (HTAB) microemulsions were investigated in both the presence and the absence of NaCl salt. A detailed study of particle size analysis for both the surfactants with different composition has been made from laser light scattering measurement. Surface tensions of microemulsions and surfactant solutions were also measured for investigation of their surface activities. Surface tensions have been reduced remarkably in the case of microemulsion systems compared to simple aqueous s...

Formation, characterization and enzyme activity in water-in-hydrophobic ionic liquid microemulsion stabilized by mixed cationic/nonionic surfactants

The phase behavior of the pseudo ternary system 1-tetradecyl-3-methylimidazolium bromide ([C14mim]Br)/Triton X-100/H2O/1-butyl-3-methylimidazolium hexafluorophosphate ([Bmim]PF6) has been studied at 35°C. With the increase in the mole fraction of Triton X-100 in the mixed surfactants, the water solubilization capacity increases and the monophasic area enlarges. The H2O-in-[Bmim]PF6 (W/IL) microemulsion was identified via electrical conductivity measurement. The existence of bulk water in the W/IL microemulsion was demonstrated based on the change of the O-D vibration frequency with content of D2O added and confirmed using UV–vis technique with CoCl2 as probe. Laccase can be solubilized in the W/IL microemulsion and exhibits a catalytic activity. The interface of the W/IL microemulsion has an inhibitory effect on the expression of the laccase activity, and the inhibitory effect is varied with the molar ratio of the mixed surfactants.

Preparation of SiO2 /epoxy nanocomposite via reverse microemulsion in situ polymerization

Reverse water/oil (w/o) microemulsions composed of epoxy resin (EP) (the oil phase) and nonionic surfactant and ammonia aqueous solutions (the water phase) were used in the synthesis of SiO2/EP nanocomposites. The stability of reverse microemulsion was evaluated by measuring water solubilization of the microemulsion. Effects of surfactant type and content, ammonia concentration and temperature on the water solubilization were systematically investigated. Higher water solubilization capacity was obtained by nonionic surfactant TX-100 compared with other two surfactants, Span-80 and Tween-80. Ammonia concentration of 5 wt% and preparation temperature at 35°C were favorable for forming a stable microemulsion and enabling the subsequent hydrolysis and condensation reaction of inorganic precursor tetraethoxysilane (TEOS). SiO2/ epoxy nanocomposites were prepared via in situ polymerization of TEOS within the nanoscale reverse microemulsion “water pool”. FTIR, SEM, and universal testing machine were used to characterize the structural and mechanical properties of the composite. The results revealed that the optimal mechanical properties were obtained at 3 wt% TEOS content. Compared with neat epoxy resin, the tensile and flexural strength of the composite were 40% and 12% higher, respectively. The formation of the silica structure in the hybrid was investigated with FTIR. The SEM and optical observations showed a ductile fracture morphology and good miscibility between inorganic and organic phases. POLYM. COMPOS., 35:1388–1394, 2014. © 2013 Society of Plastics Engineers

Physicochemical investigation of mixed surfactant microemulsions: Water solubilization, thermodynamic properties, microstructure, and dynamics

In this contribution, we report on a systematic investigation of phase behavior and solubilization of water in water-in-heptane or decane aggregates stabilized by mixtures of polyoxyethylene (20) cetyl ether (Brij-58) and cetyltrimethylammonium bromide (CTAB) surfactants with varying compositions in conjugation with 1-pentanol (Pn) at fixed surfactant(s)/Pn ratio and temperature. Synergism in water solubilization was evidenced by the addition of CTAB to Brij-58 stabilized system in close proximity of equimolar composition in both oils. An attempt has been made to correlate composition dependent water solubilization and volume induced conductivity studies to provide insight into the solubilization mechanism of these mixed systems. Conductivity studies reveal the ascending curve in water solubilization capacity-(Brij-58:CTAB, w/w) profile as the interdroplet interaction branch indicating percolation of conductance and the descending curve is a curvature branch due to the rigidity of the interface in these systems. The microstructure of these systems as a function of surfactant composition has been determined by dynamic light scattering (DLS) and Fourier transform infrared spectroscopy (FTIR) measurements. FTIR study reveals increase and decrease in relative population of bound and bulk-like water, respectively, with increase in Brij-58:CTAB (w/w). DLS measurements showed that the droplet hydrodynamic diameter (Dh) decreases significantly with the increase in Brij-58:CTAB (w/w). Further, the interfacial composition and energetic parameters for the transfer of Pn from bulk oil to the interface were evaluated by the dilution method. Formation of temperature-insensitive microemulsions and temperature invariant droplet sizes are evidenced in the vicinity of the equimolar composition. The results are interpreted in terms of a proposed mechanism.

Preparation and characterization of cyanocobalamin (vit B12) microemulsion properties and structure for topical and transdermal application.

The objective of this study was to design a topical microemulsion of Vit B12 and to study the correlation between internal structure and physicochemical properties of the microemulsions. Microemulsions are thermodynamically stable mixtures of water, oil, surfactants and usually cosurfactants with several advantages for topical and transdermal drug delivery. The formulation of microemulsions for pharmaceutical use requires a clear understanding of the properties and microstructures of the microemulsions. In this study, phase behavior and microstructure of traditional and novel microemulsions of Vit B12 have been investigated by Small-angle X-ray (SAXS), differential scanning calorimetery (DSC) and measuring density, particle size, conductivity and surface tension. WO and bicontinuous microemulsion with different microstructures were found in novel and traditional formulations. In this study, amount of water, surfactant concentration, oil/ surfactant ratio and physicochemical properties of cosurfactants influenced the microstructures. In both formulations, water behavior was affected by the concentration of the surfactant. Water Solubilization capacity and enthalpy of exothermic peak of interfacial and free water of traditional formulations were more than novel ones. This means that the affinity of water to interfacial film is dependent on the surfactant properties. This study showed that both microemulsions provided good solubility of Vit B12 with a wide range of internal structure. Low water solubilization capacity is a common property of microemulsions that can affect drug release and permeability through the skin. Based on Vit B12 properties, specially, intermediate oil and water solubility, better drug partitioning into the skin may be obtained by traditional formulations with wide range of structure and high amount of free and bounded water.

Physicochemical investigation of mixed surfactant reverse micelles: Water solubilization and conductometric studies

Abstract Solubilization of water in mixed reverse micelles (RMs) comprising sodium bis(2-ethylhexyl) sulfosuccinate (AOT), and polyoxyethylene (20) sorbitan trioleate (Tween-85) or polyoxyethylene (20) sorbitan monooleate (Tween-80) or sorbitan trioleate (Span-85) has been studied at different compositions ( X nonionic = 0–1.0) at a total surfactant concentration, S T = 0.1 mol dm −3 in polar lipophilic oils of different chemical structures: viz., ethyl oleate (EO), isopropyl myristate (IPM) and isopropyl palmitate (IPP) at 303 K. The enhancement in water solubilization (i.e., synergism) has been evidenced by the addition of nonionic surfactant to AOT/oil(s)/water systems. The maximum water solubilization capacity ( ω 0,max ) and X nonionic,max (mole fraction at which synergism occurs) have been influenced by polar head group and hydrophobic moiety of nonionic surfactant. The standard free energy change of dissolution of water ( Δ G s 0 ) of these systems depends on water content, X Tween-85 and oil. Solubilization efficiency parameter ( S P water * ) has been evaluated to underline the efficacy of oils in obtaining maximum water solubilization capacity in mixed RMs. Conductance behavior of these systems in absence and presence of additives (bile salts and hydrotrope) has also been investigated under varied water content ( ω ) at 303 K. Volume-induced percolation threshold ( ω p ) depends on X Tween-85 , oil type, and additives. An attempt has been made to give an insight to the mechanism of solubilization phenomena, standard free energy change of dissolution of water, percolation in conductance and microstructures of these systems by dynamic light scattering (DLS) measurements, wherein the chemical structures of both nonionic surfactants and polar lipophilic oils played significant role.

Transdermal delivery of diclofenac using water-in-oil microemulsion: formulation and mechanistic approach of drug skin permeation

The objective of the present investigation was to enhance skin permeation of diclofenac using water-in-oil microemulsion and to elucidate its skin permeation mechanism. The w/o microemulsion formulations were selected based on constructed pseudoternary phase diagrams depending on water solubilization capacity and thermodynamic stability. These formulations were also subjected to physical characterization based on droplet size, viscosity, pH and conductivity. Permeation of diclofenac across rat skin using side-by-side permeation cells from selected w/o microemulsion formulations were evaluated and compared with control formulations. The selected w/o microemulsion formulations were thermodynamically stable, and incorporation of diclofenac sodium into microemulsion did not affect the phase behavior of system. All microemulsion formulations had very low viscosity (11–17 cps) and droplet size range of 30–160 nm. Microemulsion formulations exhibited statistically significant increase in diclofenac permeation compared to oily solution, aqueous solution and oil–Smix solution. Higher skin permeation of diclofenac was observed with low Smix concentration and smaller droplet size. Increase in diclofenac loading in aqueous phase decreased the partition of diclofenac. Diclofenac from the oil phase of microemulsion could directly partition into skin, while diclofenac from the aqueous droplets was carried through skin by carrier effect.

Water solubilization capacity, interfacial compositions and thermodynamic parameters of anionic and cationic microemulsions

The water solubilization capacity of a particular microemulsion depends upon the partitioning of cosurfactants among water, oil and interfaces, chain length and nature of oil and cosurfactant, and their interaction with surfactant. Maximal water solubilization of microemulsion systems has been investigated by titration method. The interfacial compositions and associated thermodynamic parameters of the formation of microemulsion droplets have been studied by dilution method. The Bansal, Shah, O’Connell (BSO) equation has been verified by determination of solubilization capacity of microemulsion. Among the alkanes (C6–C18) employed in this work, maximal water solubilization for sodium dodecyl sulfate (SDS) and cetyl trimethylammonium bromide (CTAB) microemulsion systems with cosurfactant (pentan-1-ol, and 3-methyl-1-butanol) have been found in case of heptane and undecane respectively. A correlation between the change in free energy of cosurfactant transfer at the interface and the alkane carbon number was examined. With increase in oil chain length, the negative value of the change in Gibbs free energy of cosurfactant transfer decreases.

The Studies of Phase Equilibria and Efficiency Assessment for Self-Emulsifying Lipid-Based Formulations

The study was designed to build up a database for the evaluation of the self-emulsifying lipid formulations performance. A standard assessment method was constructed to evaluate the self-emulsifying efficiency of the formulations based on five parameters including excipients miscibility, spontaneity, dispersibility, homogeneity, and physical appearance. Equilibrium phase studies were conducted to investigate the phase changes of the anhydrous formulation in response to aqueous dilution. Droplet size studies were carried out to assess the influence of lipid and surfactant portions on the resulted droplet size upon aqueous dilution. Formulations containing mixed glycerides showed enhanced self-emulsification with both lipophilic and hydrophilic surfactants. Increasing the polarity of the lipid portion in the formulation leaded to progressive water solubilization capacity. In addition, formulations containing medium chain mixed glycerides and hydrophilic surfactants showed lower droplet size compared with their long chain and lipophilic counterparts. The inclusion of mixed glycerides in the lipid formulations enormously enhances the formulation efficiency.

Water Solubilization Capacity and Volume-Induced Percolation of Sodium Bis(2-ethylhexyl)sulfosuccinate Microemulsions in the Presence of 1-Alkyl-3-Methylimidazolium Chloride Ionic Liquids

The water solubilization capacity of sodium bis(2-ethylhexyl)sulfosuccinate (AOT) in isooctane microemulsions in the presence of chloride anion-based ionic liquids (ILs), such as 1-ethyl-3-methylimidazolium chloride (emimCl), 1-butyl-3-methylimidazolium chloride (bmimCl), and 1-octyl-3-methylimidazolium chloride (omimCl), was investigated. The water solubilization capacity is enhanced at low IL concentrations but decreases at high concentrations of IL. Meanwhile, the water solubilization capacity increases with the increase of chain length of ILs at low IL concentrations. The effect of ILs on the volume-induced percolation of AOT microemulsions was also studied. For the microemulsions, with an increasing volume fraction of dispersed phase (Φ), no percolation phenomena can be observed at high concentrations of IL, whereas the percolation conductance occurs at low IL concentrations and the percolation threshold (Φp) increases with the increase of IL concentrations. For the IL-containing microemulsions, the ...

Water Solubilization Capacity and Conductance Behaviors of Anionic and Cationic Microemulsion Systems

One of the most important tools in enhanced oil recovery (EOR) is microemulsion flooding to recover residual oil trapped in the reservoir after water flooding. The solubilization and phase equilibria of oil–water microemulsion have been studied with special attention on the role of alkane carbon number (ACN) of hydrocarbon, surfactant, and cosurfactant concentration on the formation of microemulsion. The ability of anionic and cationic microemulsion systems to solubilize alcohol has been investigated for different hydrocarbons. The effect of additives (NaCl salt with different concentrations) on electrical conductivity was studied by dropwise addition of brine in different concentrations to justify percolation of the microemulsion systems. The temperature effect on conductivity of microemulsions was also studied. Different aliphatic hydrocarbons (C6 to C12) and aromatic hydrocarbons such as benzene and toluene were used as synthetic oils. For the preparation of microemulsions, propan-2-ol and 3-methyl-1-b...