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Sample records for aot microemulsion system

  1. Volumetric properties of water/AOT/isooctane microemulsions.

    PubMed

    Du, Changfei; He, Wei; Yin, Tianxiang; Shen, Weiguo

    2014-12-23

    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.

  2. Phase behavior of AOT microemulsions in compressible liquids. [AOT = bis(2-ethylhexyl) sodium sulfosuccinate

    SciTech Connect

    McFann, G.J.; Johnston, K.P. )

    1991-06-13

    The phase behavior of bis(2-ethylhexyl) sodium sulfosuccinate (AOT)-alkane-brine systems is described over a wide range of pressure, temperature, and salinity for alkanes from ethane to dodecane. The partitioning of AOT between the oil, middle, and brine phases is reported for propane in order to determine the natural curvature. This is important for understanding separation processes with water-in-oil microemulsions. For the lighter, more compressible alkanes, the pressure effect on the hydrophilicity of the surfactant is much larger and in the opposite direction as for the heavier, less compressible ones. In propane at constant temperature and salinity, water-in-oil (w/o) microemulsions have been converted to middle phase microemulsions and then to oil-in-water (o/w) microemulsions by decreasing the pressure. These phase inversions are described in terms of the immiscibilities in the binary systems, and the molecular interactions at the surfactant interface. Although temperature and salinity are used commonly to manipulate interactions primarily on the water side of the interface, these results show it is possible to control interactions on the oil side by adjusting the pressure. The well-established trends in the phase behavior and size of microemulsion drops for dodecane through hexane are not observed for the lighter alkanes. For butane through ethane, a new unusual behavior is identified and attributed to a significant decrease in the strength of the attractive interactions between the surfactant tails and the alkane.

  3. Structural evolution within the one-phase region of a three-component microemulsion system: Water-n-decane-sodium-bis-ethylhexylsulfosuccinate (AOT)

    NASA Astrophysics Data System (ADS)

    Chen, S.-H.; Chang, S.-L.; Strey, R.

    1990-08-01

    The continuous inversion from a water-in-oil (w/o) microemulsion at low temperatures to an oil-in-water (o/w) microemulsion at higher temperatures within the one-phase channel of water (0.6% NaCl)-n-decane-AOT microemulsion system is investigated by small angle neutron scattering (SANS). At constant AOT (surfactant) weight fraction γ of 12%, the structural evolution as a function of temperature takes place in different forms as the oil-to-water weight fraction α is varied from 15 to 90 %. At low o-w weight fractions (α=15 and 20 %) the microemulsions transform from a water-internal, oil-continuous structure at lower temperatures to an oil-internal, water-continuous droplet structure at higher temperatures jumping across an intermediate region of a lamellar phase (Lα). However, at higher o-w weight fractions (α=80 and 90 %) the evolution goes through a stage of percolation of the water droplets first into extended water clusters, then the structural inversion takes place probably through a transition of these water clusters into an entangled tubular structure. At equal oil-to-water volume ration (α=40%), the structure can be described as bicontinuous at both low and high temperatures. In this case we are able to extract two lengths characterizing the structure from SANS data using different models for the scattering length density fluctuation correlation function of a bicontinuous microemulsion.

  4. The influence of the structure and the composition of water/AOT-Tween 85/IPM microemulsion system on transdermal delivery of 5-fluorouracil.

    PubMed

    Yanyu, Xiao; Fang, Liu; Qineng, Ping; Hao, Cai

    2012-12-01

    The purpose of this study was to investigate the influence of the structure and the composition of water/Aerosol-OT (AOT)-Tween 85/isopropylmyristate (IPM) microemulsion system (WATI) on transdermal delivery of 5-fluorouracil (5-FU). The structure of WATI was characterized by measuring surface tension, density, viscosity, electric conductivity, and differential scanning calorimetry. The effect of the drug loading, water content, component compositions and the amount of mixed surfactant on permeation of 5-FU through mice skin was evaluated by using Franz-type diffusion cells. The results in vitro implied that WATI was W/O microemulsion when the water content was below 20 wt% at fixed 20 wt% of mixed surfactant at 25°C, then might be transformed to a bicontinuous structure, finally, formed O/W microemulsion with water content over 30 wt%. Increase of the drug loading can directly facilitate the penetration of the drug across the skin. Drug diffusion after 12 h from the bicontinuous microemulsion (795.1 ± 22.3 µg·cm(-2)) would be fastest compared to that from the W/O microemulsion (650.2 ± 11.7 µg·cm(-2)) and the O/W microemulsion (676.6 ± 14.8 µg·cm(-2)). The combination of AOT and IPM could bring about synergistic effect on the skin enhancement, however, Tween 85 in WATI decreased the cumulative permeation amount of 5-FU. The content of mixed surfactant had no effect on the permeation of 5-FU at fixed surfactant/cosurfactant ratio (K(m) = 2). Thus, the increased transdermal delivery the hydrophilic drug of 5-FU was found to be concerned with both of the structure and the composition of WATI.

  5. Spectrometric study of AOT-hydrolysis reaction in water/AOT/isooctane microemulsions using phenolphthalein as a chemical probe.

    PubMed

    Mao, Shiyan; Chen, Zhiyun; Fan, Dashuang; An, Xueqin; Shen, Weiguo

    2012-01-12

    The kinetics of the alkaline hydrolysis of sodium bis(2-ethylhexyl)sulfosuccinate (AOT) in water/AOT/isooctane microemulsions has been studied by monitoring the absorbance change of the phenolphthalein in the system with time. The apparent first-order rate constant k(obs) has been obtained and found to be dependent on both the molar ratio of water to AOT ω and the temperature. The dependences of k(obs) on ω have been analyzed by a pseudophase model which gives the true rate constants k(i) of the AOT-hydrolysis reaction on the interface and the partition coefficients K(wi) for the distribution of OH(-) between aqueous and interface pseudophases at various temperatures; the latter is almost independent of the temperature and ω. The temperature dependences of the reaction rate constants k(obs) and k(i) have been analyzed to obtain enthalpy ΔH(≠), entropy ΔS(≠), and energy E(a) of activation, which indicate that the distribution of OH(-) between aqueous and interface pseudophases increases ΔS(≠) but makes no contribution to E(a) and ΔH(≠). The influence of the overall concentration of AOT in the system on the rate constant has been examined and found to be negligible. It contradicts with what was reported by García-Río et al. (1) but confirms that the first-order reaction of the AOT-hydrolysis takes place on the surfactant interface. The study of the influence of AOT-hydrolysis on the kinetics of the alkaline fading of crystal violet or phenolphthalein in the water/AOT/isooctane microemulsions suggests that corrections for the AOT-hydrolysis in these reactions are required.

  6. The effect of water on the microstructure and properties of benzene/[bmim][AOT]/[bmim][BF4] microemulsions.

    PubMed

    Bai, Tingting; Ge, Rile; Gao, Yanan; Chai, Jinling; Slattery, John M

    2013-11-28

    In the present contribution, results concerning the role of small amounts of water in the 1-butyl-3-methylimidazolium bis 2-ethylhexyl sulfosuccinate ([bmim][AOT]) based 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF4])-in-benzene reverse microemulsions are emphasized. The microemulsion aggregates have demonstrated features in common with traditional aqueous systems, such as a normal microemulsion droplet size and decreased stability due to the addition of a polar component. Dynamic light scattering (DLS) showed that the size change of microemulsion with added water depends on the loaded [bmim][BF4] content in the microemulsion: when the [bmim][BF4] content is low, the microemulsion diameter first decreases and then increases, while the size remains about the same for microemulsions with a moderate [bmim][BF4] loading and a successive increase in size was found for high-loaded [bmim][BF4] microemulsions. (1)H NMR along with two-dimensional rotating frame nuclear Overhauser effect (NOE) experiments (ROESY) revealed that water molecules formed wide interactions with both 1-butyl-3-methylimidazolium ([bmim]) and bis 2-ethylhexyl sulfosuccinate ([AOT]), leading to a decrease in the headgroup area of [bmim][AOT], i.e. α value, which will decrease the microemulsion size. On the other hand, addition of water can simultaneously swell the microemulsions, causing an increase in the diameter. It is also deduced that the Coulomb forces between the [AOT] and [bmim] should be one of the main driving forces for the formation of [bmim][BF4]-in-benzene microemulsions.

  7. Nanoparticles synthesis of tungsten disulfide via AOT-based microemulsions

    SciTech Connect

    Ghoreishi, S.M.; Meshkat, S.S.; Ghiaci, M.; Dadkhah, A.A.

    2012-06-15

    Graphical abstract: A controlled synthesis of WS2 nanoparticles (most probably inorganic fullerene (IF)) via microemulsion was applied for the first time to prepare WS2 (7–12 nm) by acidification of the water cores of the AOT reverse microemulsion. Highlights: ► An innovative reverse microemulsion technique was developed for WS{sub 2} synthesis. ► WS{sub 2} nanoparticles were obtained with narrow size distribution in range of 7–12 nm. ► Operating cost of microemulsion was lower in contrast to quartz reactor method. ► WS{sub 2} morphology could be controlled to obtain highly active and selective catalysts. ► Lower size of WS{sub 2} in this study overcomes the shortcoming of quartz reactor method. -- Abstract: The tungsten disulfide (WS{sub 2}) nanoparticles (most probably inorganic fullerene (IF)) with a narrow size distribution were synthesized by a reverse micelle technique for the first time. The particle size was controlled by varying water-to-surfactant molar ratio (W{sub 0}), aging time and reagent concentration. The synthesized WS{sub 2} nanoparticles were characterized by zetasizer, UV–visible spectrophotometers and transmission electron microscopy (TEM). The WS{sub 2} nanoparticles with particle diameter size of 7–12 nm were obtained via 24 h aging time. The particle size was controlled by changing the aging time and molar ratio of water/surfactant. Doubling W{sub 0} increased the amount and particle size of WS{sub 2} by 22 and 26%, respectively. The effect of aging time in the range of 6–24 h was investigated and the complete disappearance of yellowish color at 24 h resulted in an optically clear solution, which was the indication of WS{sub 2} formation with 100% conversion of reactant ((NH{sub 4}){sub 2}WS{sub 4}) in the batch reactor.

  8. Electrical conductivity and permittivity of water-AOT-n-heptane microemulsions

    SciTech Connect

    Arcoleo, V.; Goffredi, M.; Liveri, V.T.

    1995-11-01

    Measurements of the electrical conductivity and of the complex permittivity of water-sodium bis(2-ethylhexyl) sulfosuccinate (AOT)-n-heptane microemulsions are reported. The experimental results are rationalized in terms of a hopping mechanism of AOT anions within clusters of reversed micelles. The dependence of the hopping rate and of the cluster dimensions upon the ratio [water]/[AOT] and temperature is discussed.

  9. Micelle and microemulsion properties of cesium di-dodecyl-dimethylsulfosuccinate, Cs-AOT

    SciTech Connect

    Sheu, E.Y.; Nostro, P.L.; Capuzzi, G.; Baglioni, P.

    1999-09-28

    Cesium di-2-ethylsulfosuccinate (Cs-AOT) micelles in aqueous solutions and Cs-AOT/water/n-decane microemulsions were investigated, at 22 {plus{underscore}minus} 0.1 C, by small angle neutron scattering (SANS). The critical micelle concentration of Cs-AOT is {approximately}2mM, comparable to that of Na-AOT. However, their solution properties and micellar structures were found to be very different. The solubility of Na-AOT in water is approximately 1 wt %, and the micelles grow from spherical (at a concentration of about 0.1 wt %) to oblate objects with eccentricity equal to about 0.8 (at a concentration of 1 wt %), whereas Cs-AOT is largely soluble in water, over 30 wt %, and its micelles are disklike at 1 wt %. As the surfactant concentration increases, micelles may go through an L{sub 3} region, and enter the lamellar phase. Cs-AOT/water/n-decane microemulsions, with a [water]/[Cs-AOT] = 29.1, form isotropic L{sub 2} phases only at very low Cs-AOT + ater volume fractions (below 0.0165), whereas Na-AOT has a large L{sub 2} region. These differences are probably due to the degree of charge condensation near the AOT polar headgroups. A theoretical description is needed to better understand this behavior.

  10. [Controllable synthesis and UV-Vis spectral analysis of silver nanoparticles in AOT microemulsion].

    PubMed

    Zhang, Wan-Zhong; Qiao, Xue-Liang; Luo, Lang-Li; Chen, Jian-Guo

    2009-03-01

    Colloidal silver nanoparticles were synthesized in water-in-oil microemulsion using silver nitrate solubilized in the water core of a microemulsion as source of silver ions, hydrazine hydrate solubilized in the water core of another one as reducing agent, cyclohexane as the continuous phase, and sodium bis(2-ethylhexyl) sulfosuccinate (AOT) as the surfactant. The main factors affecting the formation of silver nanoparticles were systematically studied. Ultraviolet-visible (UV-Vis) spectra were used for analyzing the effects of reaction parameters, including the type of reducing agents, the molar ratio of water to surfactant and the concentration of AgNO3 and AOT and so on, on the formation of silver nanoparticles. Original results for the controllable synthesis of silver nanoparticles were obtained when the synthesis proceeded in AOT-cyclohexane-AgNO3 microemulsion. The UV-Vis spectra of silver sols formed in the microemulsion with various parameters were studied systematically. The results show that the amount and average size of the obtained nanoparticles obviously depend on the above parameters. When the concentration of AgNO3 is lower, smaller silver nanoparticles are easy to form by increasing the concentration of AgNO3 appropriately. The higher W value was found to form larger numbers of silver nanoparticles with larger particle size. Compared to the solubility of NaBH4 in AOT reverse micelles, hydrazine hydrate is well soluble in these micelles, and thus it is favorable to reduce the silver ions solubilized in the water core of AOT-cyclohexane-AgNO3 microemulsion. The increase in the concentration of AOT induces an increase in the number of AOT micelles and a decrease in the molar ratio of water to surfactant. As a result, the solubilization capacity of reactants in the micelles increases and the radii of the micelles decrease. That is to say, with the increase in AOT concentration, the amount of the formed nanoparticles increases and the average size of the

  11. Modulation of volume fraction results in different kinetic effects in Belousov-Zhabotinsky reaction confined in AOT-reverse microemulsion.

    PubMed

    Álvarez, Eva Villar; Carballido-Landeira, Jorge; Guiu-Souto, Jacobo; Taboada, Pablo; Muñuzuri, Alberto P

    2011-03-07

    The effects of volume fraction modulations on a Belousov-Zhabotinsky reaction catalyzed by the photosensitive Ru(bpy)(3)(+2) confined in an AOT microemulsion system are analyzed. Kinetic observables such as the induction time or the initial oscillation period demonstrate two different types of correlation with the volume fraction depending on whether the system is below or above the microemulsion percolation threshold. Temporal evolution also demonstrates an exponential growth of the period with the number of oscillations independent of the volume fraction of the system. © 2011 American Institute of Physics.

  12. The Effect of AOT and Octanoic Acid on the Formation of Stable Water-in-diesel Microemulsion

    NASA Astrophysics Data System (ADS)

    Zhang, Yue; Misran, Misni Bin; Wang, Zhicheng; Zhang, Yu

    2017-05-01

    Sodium bis(2-ethylhexyl)sulfosuccinate (AOT) and octanoic acid (OA) were used as surfactants to prepare water-in-diesel microemulsion. The effect of mixed surfactants ratio on the phase behavior of water-in-diesel microemulsion was investigated. The R0-T plot phase diagrams for the diesel/AOT and OA/water system with different surfactant ratios were constructed at 30-80 °C. The results indicate that the largest single phase region could be obtained when OA to AOT molar ratio was 1. The temperature had a significant influence on phase transformation behavior. The single phase separated into two immiscible phases with the increase of temperature when R0 value was above 10. Compared with applying AOT alone, mixing AOT with appropriate amount of OA is benefit to form smaller nanosized W/O droplets. The determination of particle size was performed to verify the phase transformation behavior, and the results were consistent with the phase diagrams.

  13. Electrochemistry and electrocatalysis with vitamin B sub 12 in an AOT water-in-oil microemulsion

    SciTech Connect

    Owlia, Azita; Wang, Zhenghao; Rusling, J.F. )

    1989-07-05

    Vitamin B{sub 12a} solubilized in water pools of highly resistive water-in-oil (w/o) microemulsions of 0.2 M Aerosol OT (AOT, bis(2-ethylhexyl) sulfosuccinate)/4 M water/isooctane gave separate reductions of base-on cob(III)alamine to base-on cob(II)alamine (E{sub 1/2} = {minus}0.03 V vs SCE) and base-on cob(II)alamine to base-off cob(I)alamine (E{sub 1/2} = {minus} 0.87 V). Diffusion coefficients suggested that vitamin B{sub 12} induces the formation of surfactant aggregates in w/o microemulsions that are larger than in solute-free systems. Relative reactivities toward reductions of three oil-soluble alkyl vicinal dihalides by electrochemically generated cob(I) alamine were modified in the microemulsion compared to isotropic water-acetonitrile. Changes in relative reactivity are not explained by simple partition of vicinal dibromides between isooctane and water and suggest specific interactions with surfactant aggregates or significant reaction in the bulk isooctane phase.

  14. Droplet polydispersity and shape fluctuations in AOT [bis(2-ethylhexyl)sulfosuccinate sodium salt] microemulsions studied by contrast variation small-angle neutron scattering

    NASA Astrophysics Data System (ADS)

    Arleth, Lise; Pedersen, Jan Skov

    2001-06-01

    Microemulsions consisting of AOT water, and decane or iso-octane are studied in the region of the phase diagram where surfactant covered water droplets are formed. The polydispersity and shape fluctuations of the microemulsion droplets are determined and compared in the two different alkane types. Conductivity measurements show that there is a pronounced dependence of the temperature behavior of the microemulsion on the type of alkane used. In both cases the microemulsion droplets start to form larger aggregates when the temperature increases. But in the system with decane this aggregation temperature occurs at a temperature about 10 °C lower than in a similar system with iso-octane. Aggregation phenomena are avoided and the two systems are at approximately the same reduced temperature with respect to the aggregation temperature when the temperature of the AOT/D2O/decane microemulsion is 10 °C and the temperature of the AOT/D2O/iso-octane microemulsion is 20 °C. Contrast variation small-angle neutron scattering measurements are performed at these temperatures on systems with volume fractions of 5% D2O+AOT by varying the scattering length density of the alkane. The small-angle scattering for 11 different contrasts evenly distributed around the match points are studied for each sample. The scattering data for the different contrasts are analyzed using a molecular constrained model for ellipsoidal droplets of water covered by AOT, interacting as polydisperse hard spheres. All contrasts are fitted simultaneously by taking the different contrast factors into account. The analysis show that at the same reduced temperature with respect to the aggregation temperature the droplet size, polydispersity index, the size of the shape fluctuations are similar in the two systems. A polydispersity index (σ/R of the Gaussian size distribution) of 16% and an average axis ratio of the droplets of 1.56 is found in the AOT/D2O/decane microemulsion. In the AOT/D2O/iso-octane system

  15. Influence of anionic surfactants on the electric percolation of AOT/isooctane/water microemulsions.

    PubMed

    García-Río, L; Mejuto, J C; Pérez-Lorenzo, M; Rodríguez-Alvarez, A; Rodríguez-Dafonte, P

    2005-07-05

    A study was carried out concerning the influence of sodium alkyl sulfonates on the electric percolation of AOT/isooctane/water microemulsions ([AOT] = 0.5 M and W = [H2O]/[AOT] = 22.2). An important effect was observed with regard to the percolation temperature caused by the addition of small quantities of alkyl sulfonates (rho = [alkyl sulfonate]/[AOT] = 0.01). The short chain alkyl sulfonates (C3-C5) cause an increase in the percolation temperature, which in turn is reduced as we increase the chain length of the additive until we obtain a percolation temperature which is lower than that which is observed in the absence of an additive (C6-C8). For hydrocarbon chains of a greater length we can observe a new increase in the percolation temperature (C10-C18). This behavior has been explained as a consequence of (i) the incorporation of the additives at the interphase of the microemulsion and (ii) the geometric parameters of the different surfactants added to the microemulsion.

  16. Photoisomerization and reorientational mobility of symmetric carbocyanines in AOT/alkane/polar solvent microemulsions

    NASA Astrophysics Data System (ADS)

    Dandapat, Manika; Basu, Saswati; Ghosh, Deborin; Mandal, Debabrata

    2014-07-01

    Molecular motion of carbocyanine fluorophores DOCI, DODCI and DTDCI were studied in AOT/n-heptane microemulsions containing added polar solvents: water, methanol or acetonitrile. The response varied remarkably depending on the nature of the fluorophore and polar solvent. When the amount of added polar solvent was low, molecular mobility was invariably retarded, due to a combination of electrostatic and hydrophobic forces that induce the guest fluorophore to cling to the AOT molecules of the host reverse micelle. However, at high amounts of added methanol or water, these interactions diminished considerably, causing increase in the mobility of the guest fluorophores up to different extents.

  17. Rheological properties of methane hydrate slurries formed from AOT + water + oil microemulsions.

    PubMed

    Webb, Eric B; Koh, Carolyn A; Liberatore, Matthew W

    2013-09-03

    The in situ formation and flow properties of methane hydrates formed from water-in-oil microemulsions composed of water, dodecane, and aerosol OT surfactant (AOT) were studied using a unique high pressure rheometer. AOT microemulsions have high stability (order of months), well-characterized composition, and yield reproducible results compared to hydrate studies in water-in-crude oil emulsions. Viscosity increases on the order of minutes upon hydrate formation, and then decreases on the order of hours. If significant unconverted water remained after the initial formation event, then viscosity increases for a time as methane slowly dissolves and converts additional water to hydrate. In addition to transient formation measurements, yield stresses and flow curves are measured for a set of experimental conditions. Hydrate slurry viscosity and yield stress increase with increasing water volume fraction, increasing initial pressure, decreasing temperature, and decreasing formation shear rate.

  18. Characterization of water/AOT/benzene microemulsions during photoreduction to produce silver particles.

    PubMed

    Harada, Masafumi; Saijo, Kenji; Sakamoto, Naoki; Ito, Kazuki

    2010-03-15

    Colloidal dispersions of silver (Ag) particles were prepared by the photoreduction of silver perchlorate (AgClO(4)) in water/AOT/benzene water-in-oil (w/o) microemulsions consisting of sodium bis(2-ethylhexyl) sulfosuccinate (AOT), water and benzene. Formation mechanisms of Ag particles prepared in the presence of benzoin by photoreduction from Ag(+)-containing w/o microemulsions were investigated by UV-vis, transmission electron microscopy (TEM), extended X-ray absorption fine structure (EXAFS) and small-angle X-ray scattering (SAXS) measurements. By a combination of TEM and EXAFS results, Ag particles show a metallic nature after the photoreduction and the diameter of Ag particles ranges between 5 and 30 nm. In situ time-resolved SAXS measurements show that the integrated rate equation can be applied in the reduction process of Ag(+) ions to Ag(0) atoms, and the autocatalytic Ag particle growth proceeds in the association process of Ag(0) atoms during the photoreduction of Ag(+)-containing w/o microemulsions. The nanometer-sized water droplets microemulsified by AOT in benzene continuous-phase regulated the size of Ag particles, and the size and shape of water droplets were retained during the Ag particle formation. 2009 Elsevier Inc. All rights reserved.

  19. Reversible switching of electrical conductivity in an AOT-isooctane-water microemulsion via photoisomerization of azobenzene.

    PubMed

    Bufe, Markus; Wolff, Thomas

    2009-07-21

    The electrical conductivity of microemulsions composed of aerosol OT (AOT), isooctane, and water as a function of temperature was studied in the absence and presence of azobenzene, and consequences of an in situ trans-cis photoisomerization of azobenzene were investigated. A conductivity onset upon raising the temperature of a water-in-oil microemulsion indicates percolation. Small amounts (0.1-5% w/w) of solubilized azobenzene induce higher percolation temperatures T(p) (by up to 19 K), and photoisomerization of azobenzene shifts T(p) back to values that may be below T(p) in the absence of azobenzene. Consequently, the microemulsion can be switched from nonconducting to conducting by exposing samples to UV-light at lambda > 310 nm, without varying temperature or composition. The effect reverts within several minutes after turning off the irradiation lamp through thermal reisomerization. By that, reversible switching of electrical conductivity is brought about.

  20. Droplet polydispersity and shape fluctuations in AOT [bis(2-ethylhexyl)sulfosuccinate sodium salt] microemulsions studied by contrast variation small-angle neutron scattering

    SciTech Connect

    Arleth, Lise; Pedersen, Jan Skov

    2001-06-01

    Microemulsions consisting of AOT water, and decane or iso-octane are studied in the region of the phase diagram where surfactant covered water droplets are formed. The polydispersity and shape fluctuations of the microemulsion droplets are determined and compared in the two different alkane types. Conductivity measurements show that there is a pronounced dependence of the temperature behavior of the microemulsion on the type of alkane used. In both cases the microemulsion droplets start to form larger aggregates when the temperature increases. But in the system with decane this aggregation temperature occurs at a temperature about 10{degree}C lower than in a similar system with iso-octane. Aggregation phenomena are avoided and the two systems are at approximately the same reduced temperature with respect to the aggregation temperature when the temperature of the AOT/D{sub 2}O/decane microemulsion is 10{degree}C and the temperature of the AOT/D{sub 2}O/iso-octane microemulsion is 20{degree}C. Contrast variation small-angle neutron scattering measurements are performed at these temperatures on systems with volume fractions of 5% D{sub 2}O+AOT by varying the scattering length density of the alkane. The small-angle scattering for 11 different contrasts evenly distributed around the match points are studied for each sample. The scattering data for the different contrasts are analyzed using a molecular constrained model for ellipsoidal droplets of water covered by AOT, interacting as polydisperse hard spheres. All contrasts are fitted simultaneously by taking the different contrast factors into account. The analysis show that at the same reduced temperature with respect to the aggregation temperature the droplet size, polydispersity index, the size of the shape fluctuations are similar in the two systems. A polydispersity index ({sigma}/R of the Gaussian size distribution) of 16% and an average axis ratio of the droplets of 1.56 is found in the AOT/D{sub 2}O

  1. Influence of aza crown ethers on the electric percolation of AOT/isooctane/water (w/o) microemulsions.

    PubMed

    Dasilva-Carvalhal, J; Fernández-Gándara, D; García-Río, L; Mejuto, J C

    2006-09-15

    A study was carried out on the influence of different aza crown ethers on the electric percolation of AOT/isooctane/water microemulsions. A dual behavior of the aza crown ethers with regard to the percolative phenomenon was observed: low additive concentration causes an increase in the percolation temperature, whereas at high additive concentration a reduction in the percolation temperature of the system was observed. This dual behavior allowed us to define the compensation concentration, which corresponds the aza crown ether concentration at which there is no effect on the percolative phenomenon. We observed a correlation between the effect exerted by the aza crown ethers and the size of the cavity. This shows the importance of the capacity to complexate Na(+) and solubilize it in the interface and the continuous medium on the electric percolation. We also observed a correlation between the effect of the aza crown ethers on the percolation temperature and their external size. This shows the importance of their inclusion in the interface on the percolative phenomenon. Such an inclusion modifies the properties of the AOT film, facilitating the exchange of matter between droplets. A satisfactory multiparametric correlation between the compensation concentration, the distribution of the aza crown ether between water and 1-octanol, and the number of electron-donor atoms (O and N) in the crown ether was obtained. The effects have been compared with those corresponding to the crown ethers.

  2. Switching electrical conductivity in an AOT-isooctane-water microemulsion through photodimerization of solubilized N-methyl-2-quinolone.

    PubMed

    Bufe, Markus; Wolff, Thomas

    2006-09-28

    The electrical conductivity of microemulsions composed of Aerosol OT (AOT), isooctane and water as a function of temperature was studied in the absence and presence of N-methyl-2-quinolone (NMQ), and consequences of an in situ photodimerization of NMQ were investigated. A conductivity increase upon raising the temperature of a water-in-oil microemulsion indicates percolation. Percolation temperatures (Tp) can be influenced specifically by the addition of certain substances. Small amounts of solubilized N-methyl-2-quinolone induce lower Tp (by up to 9 K), and photodimerization of NMQ shifts Tp back to higher values. Consequently, the microemulsion can be switched from conducting to non-conducting without varying temperature or composition by exposing samples to UV light at lambda > 310 nm. The effect can be reverted in part by irradiation at lambda = 250 nm. Coumarin derivatives--structurally related to NMQ--show much slighter effects.

  3. Synthesis, characterization, and electrophoretic concentration of titanium dioxide nanoparticles in AOT microemulsions.

    PubMed

    Bulavchenko, Alexander I; Shaparenko, Nikita O; Demidova, Marina G

    2017-07-01

    Stable organosols of TiO2 nanoparticles were prepared by hydrolysis of titanium tetraisopropoxide (TTIP) in microemulsions of sodium bis(2-ethylhexyl)sulfoxynate (АОТ) in n-decane with increasing the content of aqueous pseudophase from 0.15 to 0.85 vol.%. As the water content increased, the hydrodynamic diameter of nanoparticles grew from 10 to 225 nm, and the  ζ-potential, from -6 to 18 mV (the surface of TiO2 nanoparticles was recharged when the water content was 0.45 vol.%). Nonaqueous electrophoresis in a capacitor-type cell made it possible to concentrate nanoparticles with a diameter of 60 to 225 nm (concentration factor was 10), separate 20 nm and 225 nm particles, and decrease the content of АОТ in organosol by an order of magnitude. Preparation of a concentrate of nanoparticles with a low content (0.015 M) of AOT included the following stages: (i) electrophoresis after synthesis; (ii) sampling of the concentrate and its twenty-fold dilution with pure n-decane; and (iii) repeated electrophoresis. In situ laser and spectrophotometric scanning of the interelectrode space showed the formation of a sharp boundary between the raffinate and the layer of moving nanoparticles during electrophoresis. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Micellar interactions in water-AOT based droplet microemulsions containing hydrophilic and amphiphilic polymers

    NASA Astrophysics Data System (ADS)

    Appel, Markus; Spehr, Tinka Luise; Wipf, Robert; Moers, Christian; Frey, Holger; Stühn, Bernd

    2013-11-01

    We investigate the influence of addition of hydrophilic and amphiphilic polymer on percolation behavior and micellar interactions in AOT-based water-in-oil droplet microemulsions. We focus on two series of samples having constant molar water to surfactant ratio W = 20 and constant droplet volume fraction Φ = 30%, respectively. From dielectric spectroscopy experiments, we extract the bending rigidity of the surfactant shell by percolation temperature measurements. Depending on droplet size, we find stabilization and destabilization of the surfactant shell upon addition of hydrophilic poly(ethylene glycol) (PEG) (Mn = 3100 g mol-1) and amphiphilic poly(styrene)-b-poly(ethylene glycol) copolymer with comparable length of the hydrophilic block. Complementary small angle X-ray scattering experiments corroborate the finding of stabilization for smaller droplets and destabilization of larger droplets. Subsequent analysis of dielectric spectra enables us to extract detailed information about micellar interactions and clustering by evaluating the dielectric high frequency shell relaxation. We interpret the observed results as a possible modification of the inter-droplet charge transfer efficiency by addition of PEG polymer, while the amphiphilic polymer shows a comparable, but dampened effect.

  5. Enzyme hyperactivity in AOT water-in-oil microemulsions is induced by 'lone' sodium counterions in the water-pool.

    PubMed

    Oldfield, Christopher; Freedman, Robert B; Robinson, Brian H

    2005-01-01

    Water-in-oil microemulsions are thermodynamically stable single-phase dispersions of water and surfactant within a continuous oil phase. The classical ternary system, based on the surfactant sodium bis(2-ethylhexyl)sulfosuccinate ('AOT'), water and an alkane such as n-heptane, is an optically transparent monodispersion of spherical water-droplets coated with a close-packed surfactant monolayer and the droplet radius is, to a good first approximation, directly proportional to the molar water: surfactant ratio, R. Enzymes dissolved in the water droplets retain activity and stability. These systems have attracted interest as media for biotransformations. Principally based upon studies in AOT-stabilized w/o microemulsions, a peculiar feature of the kinetics of enzyme-catalyzed reactions has long been apparent: the reaction rate characteristically increases from around zero at R=3, through a maximum, in the range R= 10-20, and thereafter decreases again, so that plots of rate vs. R are characteristically 'bell-shaped'. Furthermore, at optimal R, enzymes seem to be 'hyperactive', i.e., they are more active, by a modest but significant factor of 2-3-fold, than in aqueous solution. In this paper we propose the hypothesis that this kind of R-dependence arises because of the presence of freely mobile lone surfactant counterions (Na+) within the water-pool. These ions have no charge partners within the water pool and consequently have a high electrochemical potential. According to our model, lone counterions facilitate the hydrolysis of ester or amide substrates, for example, by stabilizing the tetrahedral intermediate formed during the reaction through ion-pairing with the carbonyl oxygen of the substrate, thus facilitating transfer of negative charge from the carbonyl carbon as it is attacked by the incoming nucleophile. An expression for the relationship between the concentration of free counterions in the water-pool and the compositional parameter R leads directly

  6. Synthesis of Ag and AgI quantum dots in AOT-stabilized water-in-CO2 microemulsions.

    PubMed

    Liu, Juncheng; Raveendran, Poovathinthodiyil; Shervani, Zameer; Ikushima, Yutaka; Hakuta, Yukiya

    2005-03-04

    Silver and silver iodide nanocrystals have been synthesized in the water-in-CO(2) reverse microemulsions formed by the commonly used surfactant, sodium bis(2-ethylhexyl)sulfosuccinate (AOT), in the presence of 2,2,3,3,4,4,5,5-octafluoro-1-pentanol as cosurfactant. The nanometer-sized aqueous domains in the microemulsion cores not only act as nanoreactors, but the surfactant interfacial monolayer also helps the stabilization of the metal and semiconductor nanoparticles. The transmission electron microscopy results show that silver and silver iodide nanocrystals with average diameters of 6.0 nm (standard deviation, SD=1.3 nm) and 5.7 nm (SD=1.4 nm), respectively, were formed. The results indicate that the method can be utilized as a general and economically viable approach for the synthesis of metal and semiconductor quantum dots in environmentally benign supercritical carbon dioxide.

  7. The catalytic efficiency of lipase in a novel water-in-[Bmim][PF6] microemulsion stabilized by both AOT and Triton X-100.

    PubMed

    Xue, Luyan; Li, Ying; Zou, Feixue; Lu, Lu; Zhao, Yin; Huang, Xirong; Qu, Yinbo

    2012-04-01

    In the water-in-[Bmim][PF(6)] microemulsion stabilized by both AOT and Triton X-100, the lipase-catalyzed hydrolysis of 4-nitrophenyl butyrate (p-NPB) was investigated to evaluate the catalytic efficiency of lipase in this novel microemulsion. The structural parameters of the microemulsion and the conditions of the enzymatic reaction affect the catalytic activity of lipase, especially the concentration of Tris-HCl buffer. Under optimum conditions, the catalytic activity of lipase in the present microemulsion is much higher than that in H(2)O saturated [Bmim][PF(6)]. When the partitioning of the substrate in the microemulsion is taken into account, the catalytic efficiency of lipase in this novel microemulsion is 14.3 times that in H(2)O saturated [Bmim][PF(6)] due to the significant decrease of the Michaelis constant in the microemulsion. Due to the large interface, high water activity, and probably the activating effect of the imidazolium cation in the water pool, the present microemulsion is demonstrated to be a promising medium for the lipase-catalyzed hydrolytic reaction. To demonstrate an important biocatalytic application in the IL-based microemulsion, the lipase-catalyzed synthesis of the flavoring agent benzyl acetate via transesterification of vinyl acetate with benzyl alcohol was also studied in the medium. Due to the high dispersion of lipase, large interface and removal of the byproduct, a maximum yield of 94% was obtained, indicating that the novel microemulsion is really important and useful.

  8. Ionic liquid-in-oil microemulsions composed of double chain surface active ionic liquid as a surfactant: temperature dependent solvent and rotational relaxation dynamics of coumarin-153 in [Py][TF2N]/[C4mim][AOT]/benzene microemulsions.

    PubMed

    Rao, Vishal Govind; Mandal, Sarthak; Ghosh, Surajit; Banerjee, Chiranjib; Sarkar, Nilmoni

    2012-07-19

    In the recent past, nonaqueous microemulsions containing ionic liquids (ILs) have been utilized for performing chemical reactions, preparation of nanomaterials, and synthesis of nanostructured polymers and in drug delivery systems. The most promising fact about IL-in-oil microemulsions is their high thermal stability compared to that of aqueous microemulsions. In our earlier publication (Rao, V. G.; Ghosh, S.; Ghatak, C.; Mandal, S.; Brahmachari, U.; Sarkar, N. J. Phys. Chem. B 2012, 116, 2850-2855), we presented for the first time the possibility of creating huge number of IL-in-oil microemulsions, just by replacing the inorganic cation, Na(+), of NaAOT by any organic cation and using different ionic liquids as the polar core. In this manuscript we are interested in exploring the effect of temperature on such systems. We have characterized the phase diagram of the [Py][TF2N]/[C4mim][AOT]/benzene ternary system at 298 K. We have shown that in the experimental temperature range employed in this study, the microemulsions remain stable and a slight decrease in the size of the microemulsions is observed with increasing temperature. We have reported the detailed study of solvent and rotational relaxation of coumarin 153 (C-153) in neat IL, N-methyl-N-propylpyrrolidinium bis((trifluoromethyl)sulfonyl)imide ([Py][TF2N]), and in [Py][TF2N]/[C4mim][AOT]/benzene microemulsions using steady state and picosecond time-resolved spectroscopy. We have monitored the effect of (i) varying the [Py][TF2N]/[C4mim][AOT] molar ratio (R value) and (ii) temperature on solvent and rotational relaxation of C-153. The features observed in absorption and emission spectra clearly indicate that (i) the probe molecules reside at the polar interfacial region of the [Py][TF2N]/[C4mim][AOT]/benzene microemulsions and (ii) with increasing R value the probe molecules move toward the polar IL-pool of the microemulsion. We have shown that the increase in solvation time on going from neat [Py][TF2N] to

  9. Spraying enzymes in microemulsions of AOT in nonpolar organic solvents for fabrication of enzyme electrodes.

    PubMed

    Shipovskov, Stepan; Trofimova, Daria; Saprykin, Eduard; Christenson, Andreas; Ruzgas, Tautgirdas; Levashov, Andrey V; Ferapontova, Elena E

    2005-11-01

    A new technique suitable for automated, large-scale fabrication of enzyme electrodes by air-spraying enzymes in organic inks is presented. Model oxidoreductases, tyrosinase (Tyr) and glucose oxidase (GOx), were adapted to octane-based ink by entrapment in a system of reverse micelles (RM) of surfactant AOT in octane to separate and stabilize the catalytically active forms of the enzymes in nonpolar organic media. Nonpolar caoutchouk polymer was also used to create a kind of "dry micelles" at the electrode/solution interface. Enzyme/RM/polymer-containing organic inks were air-brushed onto conductive supports and were subsequently covered by sprayed Nafion membranes. The air-brushed enzyme electrodes exhibited relevant bioelectrocatalytic activity toward catechol and glucose, with a linear detection range of 0.1-100 microM catechol and 0.5-7 mM glucose; the sensitivities were 2.41 A M(-1) cm(-2) and 2.98 mA M(-1) cm(-2) for Tyr and GOx electrodes, respectively. The proposed technique of air-brushing enzymes in organic inks enables automated construction of disposable enzyme electrodes of various designs on a mass-production scale.

  10. Temperature control of pattern formation in the Ru(bpy)(3)(2+)-catalyzed BZ-AOT system.

    PubMed

    McIlwaine, Rachel; Vanag, Vladimir K; Epstein, Irving R

    2009-03-14

    Using temperature as a control parameter, we observe a transition from stationary Turing patterns at T = 15-20 degrees C to traveling waves at T = 50 degrees C (and above) in the Ru(bpy)(3)(2+)-catalyzed Belousov-Zhabotinsky (BZ) reaction incorporated into the water nanodroplets of a water-in-oil aerosol OT (AOT) microemulsion. At constant chemical composition, molar ratio and droplet fraction, the transition takes place via a series of stable patterns, including oscillatory Turing patterns (at 35-40 degrees C) and reversed oscillatory Turing patterns (at 50 degrees C). We attribute the pattern transitions to a temperature-induced percolation transition of the BZ-AOT microemulsion, implying a change from isolated water nanodroplets to a system-spanning network of water channels.

  11. Effect of added alpha-lactalbumin protein on the phase behavior of AOT-brine-isooctane systems.

    PubMed

    Rohloff, Catherine M; Shimek, Justin W; Dungan, Stephanie R

    2003-05-15

    We have found that the presence of <1 wt% of the globular protein alpha-lactalbumin has a significant impact on the equilibrium phase behavior of dilute sodium bis(ethylhexyl) sulfosuccinate (AOT)/brine/isooctane systems. Nuclear magnetic resonance (NMR), Karl Fischer titration, and ultraviolet spectroscopy were used to determine the surfactant, oil, water, and protein content of the organic and aqueous phases as a function of the total surfactant and protein present. As a small amount of alpha-lactalbumin is added to the mixture, there is a substantial increase (up to 80%) in the maximum water solubility in the water-in-oil microemulsion phase. Dynamic light scattering measurements indicate that this increase is due to a decrease in the magnitude of the (negative) spontaneous curvature of the surfactant monolayer, as droplets swell in size. As the molar ratio of alpha-lactalbumin to AOT surpasses approximately 1:300, the partitioning of water, protein, and surfactant shifts to the excess aqueous phase, where soluble assemblies with positive curvature are detected by dynamic light scattering. Significant amounts of isooctane are solubilized in these aggregates, consistent with the formation of oil-in-water microemulsion droplets. Circular dichroism studies showed that the tertiary structure of the protein in the microemulsion is disrupted while the secondary structure is increased. In light of these findings, the protein most likely expands to a molten-globule type conformation in the AOT interfacial environment, but does not substantially unfold to become an extended chain.

  12. Processes for microemulsion polymerization employing novel microemulsion systems

    DOEpatents

    Beckman, Eric J.; Smith, Richard D.; Fulton, John L.

    1990-06-12

    This invention is directed to a microemulsion system comprising a first phase including a low-polarity fluid material which is a gas at standard temperature and pressure, and which has a cloud-point density. It also includes a second phase including a polar fluid, typically water, a monomer, preferably a monomer soluble in the polar fluid, and a microemulsion promoter for facilitating the formation of micelles including the monomer in the system. In the subject process, micelles including the monomer are formed in the first phase. A polymerization initiator is introduced into the micelles in the microemulsion system. The monomer is then polymerized in the micelles, preferably in the core of the micelle, to produce a polymeric material having a relatively high molecular weight.

  13. A theoretical approach for estimation of ultimate size of bimetallic nanocomposites synthesized in microemulsion systems

    NASA Astrophysics Data System (ADS)

    Salabat, Alireza; Saydi, Hassan

    2012-12-01

    In this research a new idea for prediction of ultimate sizes of bimetallic nanocomposites synthesized in water-in-oil microemulsion system is proposed. In this method, by modifying Tabor Winterton approximation equation, an effective Hamaker constant was introduced. This effective Hamaker constant was applied in the van der Waals attractive interaction energy. The obtained effective van der Waals interaction energy was used as attractive contribution in the total interaction energy. The modified interaction energy was applied successfully to predict some bimetallic nanoparticles, at different mass fraction, synthesized in microemulsion system of dioctyl sodium sulfosuccinate (AOT)/isooctane.

  14. Microemulsions based transdermal drug delivery systems.

    PubMed

    Vadlamudi, Harini C; Narendran, Hyndavi; Nagaswaram, Tejeswari; Yaga, Gowri; Thanniru, Jyotsna; Yalavarthi, Prasanna R

    2014-01-01

    Since the discovery of microemulsions by Jack H Schulman, there has been huge progress made in applying microemulsion systems in plethora of research and industrial process. Microemulsions are optically isotropic systems consisting of water, oil and amphiphile. These systems are beneficial due to their thermodynamic stability, optical clarity, ease of preparation, higher diffusion and absorption rates. Moreover, it has been reported that the ingredients of microemulsion can effectively overcome the diffusion barrier and penetrate through the stratum corneum of the skin. Hence it becomes promising for both transdermal and dermal drug delivery. However, low viscosity of microemulsion restrains its applicability in pharmaceutical industry. To overcome the above drawback, the low viscous microemulsions were added to viscous gel bases to potentiate its applications as topical drug delivery systems so that various drug related toxic effects and erratic drug absorption can be avoided. The present review deals with the microemulsions, various techniques involved in the development of organic nanoparticles. The review emphasized on microemulsion based systems such as hydrogels and organogels. The physicochemical characteristics, mechanical properties, rheological and stability principles involved in microemulsion based viscous gels were also explored.

  15. Interactions and phase transitions in micellar and microemulsion systems studied by small angle neutron scattering

    NASA Astrophysics Data System (ADS)

    Chen, Sow-Hsin

    1986-03-01

    Owing to their amphiphilic nature, surfactant molecules spontaneously self-assemble into various forms of aggregates in aqueous and hydrocarbon solvents. These aggregates are often so well defined and sufficiently uniform in size that the suspension can be treated effectively as one- or two-component supramolecular liquids. Ionic surfactants such as sodium dodecyl sulfate (SDS) form normal micelles in water. These micelles together with their counterions can be regarded as a strongly coupled two-component coulomb fluid. On the other hand sodium di-2-ethylhexylsulfosuccinate (AOT) forms reverse micelles in hydrocarbons (oils). These reverse micelles can solubilize large amounts of water and become microemulsions. These microemulsion droplets bear no net charge and interact with each other via Van der Waals forces analogous to atoms in simple liquids. Thus, AOT microemulsion system shows a gas-liquid type phase transition. By exploiting the existing liquid theories the SANS spectra can be satisfactorily analysed in terms of wel-defined interparticle interactions. For ionic micelles one can obtain the surface charge and aggregation number at arbitrary concentrations and for microemulsions one obtains the range and depth of the attractive interaction near the critical point.

  16. Time-dependent solubilization of IgG in AOT-brine-isooctane microemulsions: role of cluster formation.

    PubMed

    Gerhardt, N I; Dungan, S R

    2002-04-05

    The stability and structure of protein-containing water-in-oil (w/o) microemulsions were investigated by using the large protein immunoglobulin G (IgG, MW 155,000) in a mixture comprised of brine, sulfosuccinic acid bis [2-ethylhexyl]ester (sodium salt), and isooctane. We explored factors affecting the initial uptake of IgG into the w/o microemulsion and its subsequent release to a solid (precipitate) phase, and the kinetics of the latter process. Influences of such parameters as pH, ionic strength, and protein concentration on the solubilization and precipitation of bovine IgG in the organic phase are described. The structure and dynamics in microemulsions containing bovine IgG were probed by using dynamic light scattering, and it was found that the presence of IgG in the microemulsion induced strong attractive forces between the droplets. Based on results obtained by using these various experimental approaches, a model for protein solubilization and release is proposed. In this model, we propose the formation of clusters within which bovine IgG resides and which substantially slow the kinetics of protein release from the droplets to the precipitate phase.

  17. Determination of kinetic and thermochemical parameters of a substitution reaction at a square-planar palladium(II) complex in water/AOT/n-heptane microemulsions by flow microcalorimetry

    SciTech Connect

    Liveri, M.L.T.; Liveri, V.T.

    1995-12-01

    The substitution reaction [Pd(bipy)(e)]{sup 2+} + en {yields} [Pd(en){sub 2}]{sup 2+} + bipy (where bipy = 2,2{prime}-bipyridine and en=ethylenediamine) has been studied in water and water/AOT/n-heptane microemulsions at various values of the molar ratio R (R=[water]/[AOT]) by flow microcalorimetry. From calorimetric data, molar enthalpies of reaction and rate constants were obtained. These quantities indicate that, by increasing R, the reaction becomes less exothermic and its rate constant decreases, trending to the value observed in water. These features can be reasonably rationalized in terms of the peculiar solvation state of reactants inside the AOT reversed micelles and/or the peculiar physicochemical properties of micellar core.

  18. Determination of ultra trace amounts of protein by 4-chlorosulfo-(2'-hyaroxylphenylazo)-rhodanine-Ti(IV) complex [ClSARP-Ti(IV)] as the fluorescence spectral probe in AOT microemulsion

    NASA Astrophysics Data System (ADS)

    Chen, Xin; Wei, Qin; Cai, Yanyan; Han, Yanyan; Zhao, Yanfang; Du, Bin

    2009-06-01

    Experiments indicated that protein can enhance the fluorescence of the 4-chlorosulfo-(2'-hydroxylophenylazo)-rhodanine-Ti(IV) complex [ClSARP-Ti(IV)] in the presence of bis(2-ethylhexyl)sulfosuccinate sodium salt (AOT) microemulsion. Based on this, a sensitive and reproducible fluorometric method for the determination of micro amount protein was developed. The calibration curves of four proteins were given. Under the optimum experimental conditions, the enhanced fluorescence intensity of the system was in proportional to the concentration of protein in the range of 0.1-11 μg mL -1 for bovine serum albumin (BSA), 1.0-10 μg mL -1 for human serum albumin (HSA), 1.0-50 μg mL -1 for ovalbumin (Ova) and 2.5-18 μg mL -1 for γ-globulins (γ-G). Their detection limits were 0.070, 0.071, 0.33 and 0.22 μg mL -1, respectively. The ClSARP-Ti(IV) complex as a spectral probe can be used to the determination of protein in milk powder and oatmeal yielding with satisfactory results. Therefore, the proposed method is one of the most sensitive methods available. In addition, the interaction mechanism of this system is studied by multi-techniques.

  19. Size and diffusion phenomena of AOT/alcohol/water system in the presence of morin by dynamic light scattering.

    PubMed

    Bhattarai, Ajaya; Wilczura-Wachnik, Hanna

    2015-01-30

    Presented paper is a continuation of our studies on morin interaction with AOT (sodium bis(2-ethylhexyl) sulfosuccinate) reversed micelles solutions in two solvents: ethanol and n-decanol. Now we focused on morin influence on size and diffusion phenomena in the system morin/solvent/AOT/water. In this paper precise measurements of dynamic light scattering (DLS) of the effects of temperature, solvents (alcohols), water on the size and diffusion of AOT reversed micelles in the morin/AOT/alcohol/water system are reported. The concentrations of AOT were varied from 0.51 to 0.78mol/L. Morin concentration in during auto-correlation function registration was not the same in each solvent because of its different solubility depending on the solvent. Water concentration in the studied systems was defined by R parameter according to relation: R=(H2O)/(AOT) and was equal 0 and 30 in ethanol, and 0 in n-decanol. DLS measurements were done at 298.15 and 308.15K. DLS experiment involved on detection two relaxation modes (fast and slow) in the systems containing AOT reversed micelles, water, morin and solvents (ethanol and n-decanol). The DLS data clearly show the solvent influence as well as morin presence on AOT reversed micelles size and consequently their diffusion coefficients. Contrary to n-decanol strong competition between morin and ethanol molecules in AOT reversed micelles palisade layer has been found. It suggests that morin molecules replaced ethanol in AOT reversed micelles and locate in their palisade layer strongly increasing AOT reversed micelles size. Furthermore, it was found a sharp increase in correlation radii of slow modes of AOT reversed micelles containing morin molecules and their diffusion coefficients diminishing. Copyright © 2014 Elsevier B.V. All rights reserved.

  20. Designing a new strategy for the formation of IL-in-oil microemulsions.

    PubMed

    Rao, Vishal Govind; Ghosh, Surajit; Ghatak, Chiranjib; Mandal, Sarthak; Brahmachari, Udita; Sarkar, Nilmoni

    2012-03-08

    Due to the increasing applicability of ionic liquids (ILs) as different components of microemulsions (as the polar liquid, the oil phase, and the surfactant), it would be advantageous to devise a strategy by which we can formulate a microemulsion of our own interest. In this paper, we have shown how we can replace water from water-in-oil microemulsions by ILs to produce IL-in-oil microemulsions. We have synthesized AOT-derived surface-active ionic liquids (SAILs) which can be used to produce a large number of IL-in-oil microemulsions. In particular, we have characterized the phase diagram of the [C(4)mim][BF(4)]/[C(4)mim][AOT]/benzene ternary system at 298 K. We have shown the formation of IL-in-oil microemulsions using the dynamic light scattering (DLS) technique and using methyl orange (MO), betaine 30, and coumarin-480 (C-480) as probe molecules.

  1. Physicochemical investigations of microemulsification of eucalyptus oil and water using mixed surfactants (AOT+Brij-35) and butanol.

    PubMed

    Mitra, Rajib K; Paul, Bidyut K

    2005-03-15

    Microemulsification of a vegetable oil (eucalyptus) with single and mixed surfactants (AOT and Brij-35), cosurfactant of different lipophilicities (isomers of butanol), and water were studied at different surfactant and cosurfactant mixing ratios. The phase diagrams of the quaternary systems were constructed using unfolded and folded tetrahedron, wherein the phase characteristics of different ternary systems can be underlined. The microemulsion zone was found to be dependent upon the mixing ratios of surfactant and cosurfactant; the largest microemulsion zone was formed with 1:1 (w/w) S:CS. The effects of temperature and additives (NaCl, urea, glucose, and bile salts of different concentrations) on the phase behavior were examined. The mixed microemulsion system showed temperature insensitivity, whereas the Brij-35 (single) stabilized system exhibited a smaller microemulsion zone at elevated temperature. NaCl and glucose increased the microemulsion zone up to a certain concentration, beyond which the microemulsion zones were decreased. These additives decreased the microemulsion zones as temperature was increased. The effect of urea on microemulsion zone was found to be insignificant even at the concentration 3.0 mol dm(-3). Little effect on microemulsion zone was shown by NaC (sodium cholate) at 0.25 and 0.5 mol dm(-3) at different temperatures. The conductance of the single (AOT) and mixed microemulsion system (AOT+Brij-35) depends upon the water content and mixing ratios of the surfactants, and a steep rise in conductance was observed at equal weight percentages of oil and water. Viscosities for both single (AOT) and mixed (AOT+Brij-35) surfactant systems passed through maxima at equal oil and water regions showing structural transition. The viscosities for microemulsion systems increased with increasing Brij-35 content in the AOT+Brij-35 blend. Conductances and viscosities of different monophasic compositions in the absence and presence of additives (NaCl and

  2. Experimental and molecular dynamics characterization of dense microemulsion systems: morphology, conductivity and SAXS.

    PubMed

    Negro, E; Latsuzbaia, R; de Vries, A H; Koper, G J M

    2014-11-21

    Microemulsions are exciting systems that are promising as tuneable self-assembling templating reaction vessels at the nanoscale. Determination of the nano-structure of microemulsions is, however, not trivial, and there are fundamental questions regarding their design. We were able to reproduce experimental data for an important microemulsion system, sodium-AOT-n-heptane-water, using coarse-grained simulations involving relatively limited computational costs. The simulation allows visualization and deeper investigation of controversial phenomena such as bicontinuity and ion mobility. Simulations were performed using the Martini coarse-grained force field. AOT bonded parameters were fine-tuned by matching the geometry obtained from atomistic simulations. We investigated several compositions with a constant ratio of surfactant to oil while the water content was varied from 10 to 60% in weight. From mean square displacement calculation of all species, it was possible to quantify caging effects and ion mobility. Average diffusion coefficients were calculated for all charged species and trends in the diffusion coefficients were used to rationalize experimental conductivity data. Especially, the diffusion coefficient of charged species qualitatively matched the variation in conductivity as a function of water content. The scattering function was calculated for the hydrophilic species and up to 40% water content quantitatively matched the experimental data obtained from small angle X-ray scattering measurements. For higher water contents, discrepancies were observed and attributed to a nearby phase separation. In particular, bicontinuity of water and oil was computationally visualized by plotting the coordinates of hydrophilic beads. Equilibrated coarse-grained simulations were reversed to atomistic models in order both to compare ion mobility and to catch finer simulation details. Especially, it was possible to capture the intimate ion pair interaction between the sodium

  3. Microcalorimetric investigation of the solubilization of water in reversed micelles and water-in-oil microemulsions

    SciTech Connect

    Haandrikman, G.; Daane, G.J.R.; Kerkhof, F.J.M.; Os, N.M. van; Rupert, L.A.M.

    1992-10-29

    Microcalorimetry has been used to study the solubilization of water in reversed micelles and water-in-oil (w/o) microemulsions. The systems were based on Aerosol OT (AOT) and two isomerically pure sodium alkylarenesulfonates as surfactants. The solubilization of water can be described in terms of hydration of the head group (ca. three H{sub 2}O molecules per AOT), swelling of the water droplet, and phase separation. All steps are endothermic, indicating that a gain in entropy is the driving forcing for solubilization. Above 60 {degrees}C the hydration energy for AOT is strongly affected by temperature. The swelling of alkylarenesulfonate w/o microemulsions droplets in n-heptane is more endothermic than that of AOT w/o microemulsion droplets in n-heptane, indicating a significant influence of surfactant structure. 57 refs., 7 figs., 1 tab.

  4. The synthesis of silica and silica-ceria, core-shell nanoparticles in a water-in-oil (W/O) microemulsion composed of heptane and water with the binary surfactants AOT and NP-5.

    PubMed

    Chung, Sang-Ho; Lee, Dae-Won; Kim, Min-Sung; Lee, Kwan-Young

    2011-03-01

    In this study, a strategy was developed for the synthesis of nano-sized, silica-ceria, core-shell composites in a water-oil (W/O) microemulsion consisting of water, heptane and the binary surfactants AOT (sulfosuccinic acid bis (2-ethylhexyl) ester sodium salt) and NP-5 (polyoxyethylene (5) nonylphenyl ether). The core-shell, silica-ceria particles were prepared in a stepwise procedure: (1) the precipitation of the core-silica particles in a W/O microemulsion and (2) the surface precipitation of ceria on the core silica dispersed over the microemulsion. The composition of the binary surfactant greatly influenced the growth rate of the core-silica particles. The virial coefficient of diffusion was utilized to estimate the effect of the surfactant composition on the degree of intermicellar interaction that is important for the growth rate of the silica along with the flexibility of the micellar interface and the structure of the water domain. The deposition of the ceria on the core silica was not straightforward because the bulk and surface precipitation competed with each other. The promotion of surface precipitation was attempted by: (1) chemically modifying the silica surface with an organoamine group and (2) slowing down the precipitation rate of the ceria in a semi-batch operation. These attempts successfully produced the nano-sized silica-ceria, core-shell particles, which were evidenced through the TEM, XPS and zeta potential analysis.

  5. Design and evaluation of microemulsion gel system of nadifloxacin.

    PubMed

    Shinde, Ujwala; Pokharkar, Sharda; Modani, Sheela

    2012-05-01

    Topical microemulsion systems for the antiacne agent, nadifloxacin were designed and developed to overcome the problems associated with the cutaneous delivery due to poor water solubility. The solubility of nadifloxacin in oils, surfactants and cosurfactants was evaluated to screen the components of the microemulsion. Various surfactants and cosurfactants were screened for their ability to emulsify the selected oily phase. The pseudoternary diagrams were constructed to identify the area of microemulsion existence. The influence of k(m) (surfactant/cosurfactant) ratio on the microemulsion existence region was determined and optimum systems were designed. The systems were assessed for drug-loading efficiency and characterised for optical birefringence, pH and refractive index, robustness to dilution, globule size, drug content and thermodynamic stability. Optimised microemulsion systems were formulated into gel form and evaluated for viscosity, spreadability, drug content, ex vivo skin permeation and antibacterial activity. The maximum solubility of nadifloxacin in the microemulsion system was found to be 0.25%. The nadifloxacin microemulsions had a small and uniform globule size (67.3-121.23 nm). The stability results revealed that all formulations showed a stable globule size and the polydispersity index under stress conditions. Incorporation of nadifloxacin in microemulsion gel increased the ex vivo skin permeation and antibacterial activity when compared to marketed cream.

  6. Cytarabine-AOT catanionic vesicle-loaded biodegradable thermosensitive hydrogel as an efficient cytarabine delivery system.

    PubMed

    Liu, Jing; Jiang, Yue; Cui, Yuting; Xu, Chuanshan; Ji, Xiaoqing; Luan, Yuxia

    2014-10-01

    Carrier with high drug loading content is one of the most important issues in drug delivery system. In the present work, an ion-pair amphiphilic molecule composed of anticancer drug cation and surfactant anion is used for straightforward fabricating vesicles for cancer therapy. Anticancer drug (cytarabine hydrochloride) and anionic surfactant (AOT) are selected for the fabrication of ion-pair amphiphilic molecule. One amphiphilic molecule contains one drug cation, thus the drug loading content is 50% (mol/mol) in theory. The in vitro drug release study shows that the release time of cytarabine is about 3 times of the pure cytarabine solution and the permeability of cytarabine has been improved about 160 times tested by parallel artificial membrane permeability assay model. However, the hemolytic toxicity is largely decreased in the studied concentration range. The in vitro cytotoxicity results show that cytarabine-AOT amphiphiles have a much lower IC50 (drug concentration resulting in 50% cell death) value and a higher cell inhibition rate comparing with their respective components, indicating its effective therapy for leukemic cells. To obtain a longer and a convenient drug release system, the prepared vesicles are further incorporated into the thermosensitive PLGA-PEG-PLGA hydrogel to prepare a subcutaneous administration. The in vivo drug release results indicate that cytarabine-AOT vesicle-loaded hydrogel is a good injectable delivery system for controlled release of cytarabine for cancer therapy.

  7. Interface of AOT/Brij mixed reverse micellar systems: conductometric and spectrophotometric investigations.

    PubMed

    Chatterjee, Sujan; Mitra, Rajib Kumar; Paul, Bidyut Kumar; Bhattacharya, Subhash Chandra

    2006-06-15

    Solubilization and conductivity studies are carried out with AOT/Brijs (Brij-30, Brij-35, Brij-52, Brij-56, Brij-58, Brij-72, Brij-76, Brij-78)/isooctane/water mixed reverse micellar systems. Replacement of AOT molecules with large head group Brij molecules (Brij-30, Brij-35, Brij-56, Brij-58, Brij-76, Brij-78) decreases the solubilization capacity, whereas those with smaller polar head groups (Brij-52 and Brij-72) increases it. The former blends assist the conductance percolation whereas the latter retard it. An attempt has been taken to obtain more insight on the interfacial composition of the mixed interface with the help of spectrophotometric studies using 7-hydroxycoumarin as the fluorophore. The results obtained from the solubilization and conductometric studies have been correlated with those obtained from the spectroscopic studies.

  8. Physicochemical characterization of rutaecarpine-loaded microemulsion system.

    PubMed

    Choi, Han-Gon; Park, Byung-Joo; Kim, Jong Oh; Park, Young-Joon; Kim, Jin-Ki; Yoo, Bong-Kyu; Rhee, Jong-Dal; Jahng, Yurngdong; Yong, Chul Soon

    2005-08-01

    To develop an o/w microemulsion system containing poorly water-soluble rutaecarpine, the solubility of rutaecarpine in water, ethanol, various oils, and surfactants were investigated. Among the surfactants and oils tested, Tween 20/PEG 400 and castor oil were chosen as the surfactant system and oil phase of the microemulsion, as rutaecarpine was most soluble in them, respectively. Pseudoternary phase diagrams were constructed to obtain the concentration range of oil, surfactant, and cosurfactant for microemulsion formation, and the stability test of rutaecarpine delivered by microemulsion formation was then evaluated. Pseudoternary phase diagrams show that the areas of microemulsion appeared at those with 0-20% Smix (PEG 400/Tween80 = 60/40), 64-81% water, and 10-20% oil. The rutaecarpine (300 microg/g)-loaded microemulsion composed of 10.8% PEG 400, 7.2% Tween 80, 20% caster oil, and 72% water was physically and chemically stable for at least 6 months. Thus, the microemulsion system composed of castor oil, PEG 400, Tween 80, and water could be a stable dosage form for rutaecarpine.

  9. Self-Organization Induced by Self-Assembly in Microheterogeneous Reaction-Diffusion System.

    PubMed

    Cherkashin, Alexander A; Vanag, Vladimir K

    2017-03-09

    When acrylamide (AA) monomers are added to the Belousov-Zhabotinsky (BZ) reaction incorporated into nanodroplets of water-in-oil aerosol OT (AOT) microemulsion (the BZ-AOT system), free radicals produced in the BZ reaction initiate polymerization of AA monomers and polyacrylamide particles are formed. These particles change the microstructure of the AOT microemulsion thus inducing the transition from Turing patterns to new dissipative patterns which can be either stationary "black" spots or waves.

  10. Microemulsion systems for fiber deconstruction into cellulose nanofibrils.

    PubMed

    Carrillo, Carlos A; Laine, Janne; Rojas, Orlando J

    2014-12-24

    A new method to produce cellulose nanofibrils (CNF) is proposed to reduce the energy demand during deconstruction of precursor fibers suspended in aqueous media. Microemulsions were formulated with aqueous solutions of urea or ethylenediamine and applied to disrupt interfibril hydrogen bonding. Compared to typical fibrillation of lignin-containing and lignin-free fibers, pretreatment with microemulsion systems allowed energy savings during microfluidization of 55 and 32%, respectively. Moreover, microemulsion processing facilitated smaller-scale CNF structures (higher degrees of deconstruction), with higher water retention value (WRV) and surface area. Urea-containing microemulsions were found to be most effective in reducing energy consumption and in weakening the cellulosic matrix. Films prepared from CNF processed after pretreatment with urea-containing microemulsions presented a more uniform fiber network and produced films with smoother surfaces compared to those based on ethylenediamine. The lignin-containing CNF (LCNF) produced denser films than those obtained from lignin-free CNF. The mechanical properties of films obtained after application of microemulsion pretreatment were compared, and the benefits of the proposed approach were further confirmed. Overall, fiber deconstruction after microemulsion treatment is a step toward energy-efficient production of nanocellulose.

  11. Cross-diffusion in a water-in-oil microemulsion loaded with malonic acid or ferroin. Taylor dispersion method for four-component systems.

    PubMed

    Vanag, Vladimir K; Rossi, Federico; Cherkashin, Alexander; Epstein, Irving R

    2008-07-31

    We describe an improved Taylor dispersion method for four-component systems, which we apply to measure the main- and cross-diffusion coefficients in an Aerosol OT water-in-oil microemulsion loaded with one of the reactants of the Belousov-Zhabotinsky (BZ) reaction, water(1)/AOT(2)/R(3)/octane(4) system, where R is malonic acid or ferroin. With [H(2)O]/[AOT] = 11.8 and volume droplet fraction phi d = 0.18, when the microemulsion is below the percolation transition, the cross-diffusion coefficients D(13) and D(23) are large and positive ( D(13)/ D(33) congruent with 14, D(23)/ D(33) congruent with 3) for malonic acid and large and negative for ferroin ( D(13)/ D(33) congruent with -112, D(23)/ D(33) congruent with -30) while coefficients D(31) and D(32) are small and negative for malonic acid ( D(31)/ D(33) congruent with -0.01, D(32)/ D(33) congruent with -0.14) and small and positive for ferroin ( D(31)/ D(33) congruent with 5 x 10(-4), D(32)/ D(33) congruent with 8 x 10(-3)). These data represent the first direct determination of cross-diffusion effects in a pattern-forming system and of the full matrix of diffusion coefficients for a four-component system. The results should provide a basis for modeling pattern formation in the BZ-AOT system.

  12. A reliable and reproducible method for the lipase assay in an AOT/isooctane reversed micellar system: modification of the copper-soap colorimetric method.

    PubMed

    Kwon, Chang Woo; Park, Kyung-Min; Choi, Seung Jun; Chang, Pahn-Shick

    2015-09-01

    The copper-soap method, which is based on the absorbance of a fatty acid-copper complex at 715 nm, is a widely used colorimetric assay to determine the lipase activity in reversed micellar system. However, the absorbance of the bis(2-ethylhexyl) sodium sulfosuccinate (AOT)-copper complex prevents the use of an AOT/isooctane reversed micellar system. An extraction step was added to the original procedure to remove AOT and eliminate interference from the AOT-copper complex. Among the solvents tested, acetonitrile was determined to be the most suitable because it allows for the generation of a reproducible calibration curve with oleic acid that is independent of the AOT concentrations. Based on the validation data, the modified method, which does not experience interference from the AOT-copper complex, could be a useful method with enhanced accuracy and reproducibility for the lipase assay.

  13. [The lipase/lipoxygenase bienzyme system in AOT reversed micelles in octane].

    PubMed

    Pavlenko, I M; Kuptsova, O S; Kliachko, N L; Levashov, A V

    2002-01-01

    In this work it is shown that the bienzyme lipase/lipoxygenase system can function in reversed micelles of bis(2-ethyl)hexyl sulfosuccinate (AOT) in octane. As a lipase substrate, a fish fat preparation (fat of sea mammals) with a high content of polyunsaturated fatty acids was used. It was demonstrated that the bienzyme reaction proceeded in a stationary mode and had a rate-limiting step catalyzed by lipase. Under optimal conditions, the efficacy of functioning of the bienzyme system was by an order of magnitude higher than that in water. The lipase/lipoxygenase bienzyme system can be used as a new method of spectrophotometric determination of lipase activity. The English version of the paper.

  14. Characteristics of spontaneously formed nanoemulsions in octane/AOT/brine systems.

    PubMed

    Kini, Gautam C; Biswal, Sibani Lisa; Wong, Michael S; Miller, Clarence A

    2012-11-01

    Nanoemulsions were formed spontaneously by diluting water-in-oil (W/O) or brine-in-oil (B/O) microemulsions of a hydrocarbon (octane), anionic surfactant (Aerosol-OT or AOT) and water or NaCl brine in varying levels of excess brine. The water-continuous nanoemulsions were characterized by interfacial tension, dynamic light scattering, electrophoresis, optical microscopy and phase-behavior studies. The mechanism of emulsification was local supersaturation and resulting nucleation of oil during inversion. For nanoemulsions formed at low salinities with Winsor I phase behavior, octane drops grew from initial diameters of 150-250 nm to 480-1000 nm over 24h, depending on salinity. Growth was caused by mass transfer but seemed to approach the asymptotic stage of Ostwald ripening described by the Lifshitz-Slyozov-Wagner (LSW) theory only for dilution with salt-free water. Near the higher cross-over salinity (Winsor III), the nanoemulsions showed much slower growth with droplet size consistently remaining below 200 nm over 24h and reaching 250 nm after 1 week. Birefringence indicated the presence of liquid crystal for these conditions, which could have contributed to the slow growth rate. At even higher salinity levels in the Winsor II domain, W/O/W multiple emulsions having drops greater than 1 μm in diameter were consistently recorded for the first 5-7h, after which size decreased to values below 1 μm. The number and size of internal water droplets in multiple emulsion drops was found to decrease over time, suggesting coalescence of internal droplets with the continuous water phase and mass transfer of water from internal droplets to continuous phase as possible mechanisms of the observed drop shrinkage. Electrophoresis studies showed the nanoemulsions to be highly negatively charged (zeta potentials of -60 mV to -120 mV). The high charge on octane droplets helped assure stability to flocculation and coalescence, thereby allowing mass transfer to control growth in the

  15. Microemulsions: Structure and dynamics

    SciTech Connect

    Friberg, S.E.; Bothorel, P.

    1987-01-01

    This book covers the state-of-the-art in stability, structure, applications, and dynamics representation of microemulsion systems. An international group of reviewers discuss the introductory investigations into macroemulsions and interfacial free energy, the derivation of the microemulsion systems from micellar solutions, and the correlation between structure and dynamics. Future developments in this area are also considered. The book presents following: contents; phase diagrams and pseudophase assumption; phase diagram and critical behavior of a quaternary microemulsion system; non-aqueous microemulsions; nonionics; molecular diffusion in microemulsions; dynamics of microemulsions; low interfacial tensions in microemulsion systems; oil recovery and microemulsions.

  16. Viscoelastic behavior of dense microemulsions

    NASA Astrophysics Data System (ADS)

    Cametti, C.; Codastefano, P.; D'arrigo, G.; Tartaglia, P.; Rouch, J.; Chen, S. H.

    1990-09-01

    We have performed extensive measurements of shear viscosity, ultrasonic absorption, and sound velocity in a ternary system consisting of water-decane-sodium di(2-ethylhexyl)sulfo- succinate(AOT), in the one-phase region where it forms a water-in-oil microemulsion. We observe a rapid increase of the static shear viscosity in the dense microemulsion region. Correspondingly the sound absorption shows unambiguous evidence of a viscoelastic behavior. The absorption data for various volume fractions and temperatures can be reduced to a universal curve by scaling both the absorption and the frequency by the measured static shear viscosity. The sound absorption can be interpreted as coming from the high-frequency tail of the viscoelastic relaxation, describable by a Cole-Cole relaxation formula with unusually small elastic moduli.

  17. Synthesizing metallic to superconducting ceramic nanoparticles using optimized microemulsion systems

    NASA Astrophysics Data System (ADS)

    Li, Fang

    A microemulsion system with cetyltrimethylammonium bromide (CTAB) as surfactant, 1-butanol as cosurfactant and n-octane as the oil phase was optimized to produce nanoparticles. Based on the results of conductivity and droplet size, oil/surfactant weight ratio of 1.5 was chosen to perform the study due to its higher solubilization and droplet stability. Nanoparticles of monometallic Fe, bimetallic Fe/Ni, oxide Y2O3, complex oxide Y 2BaCuO5 (Y211) and YBa2Cu3O7-x (Y123) have been successfully synthesized using the water-in-oil microemulsion method. The size of amorphous Fe, Fe/Ni nanoparticles were about 10 nm and 5 nm respectively. The reduction rate of trichloroethylene (TCE, a model contaminant) by the Fe produced from the microemulsion system was the highest compared to the solution product and the commercial product. In the case of Fe/Ni nanoparticles, the initial degradation rate is four times faster than for Fe nanoparticles. Nanocrystalline Y2O3 particles were flake shaped with dimension in the range of 16--30 nm. Y2BaCuO5 and YBa2Cu3O7-x nanoparticles (˜110 nm) produced using the microemulsion method had lower processing temperature than other processing methods due to their smaller particle size. As the reaction time was shortened, the Y211 particle size reduced from larger than 100 nm to the 30--100 nm range. Superconductivity of Y123 nanoparticles was verified using magnetic measurements and the critical transition temperature was 91 K. In the melt-textured Y123 disk, a single domain with a maximum trapped field of 0.14 T was successfully fabricated with the addition of 30% Y211 nanoparticles produced by the microemulsion method. The JC and size distribution of Y211 grain in the Y123 matrix were slightly better than in conventional samples.

  18. Effects of temperature and pressure on phase transitions in a ternary microemulsion system

    NASA Astrophysics Data System (ADS)

    Nagao, Michihiro; Seto, Hideki; Takeda, Takayoshi; Kawabata, Youhei

    2001-12-01

    Temperature variation experiments of small angle neutron scattering (SANS) and neutron spin echo (NSE) were carried out in order to compare effects of temperature and pressure on a structural formation in a ternary microemulsion system composed of AOT (Aerosol-OT; dioctyl sulfosuccinate sodium salt), D2O, and n-decane. From SANS measurements, a phase transition from one-phase dense water-in-oil droplet to two-phase coexistence with a lamellar and a disordered structure was observed with increasing temperature, similar to the case of pressure variation. Another phase transition was observed at a higher temperature above the lamellar phase, although such a subsequent phase transition has not been observed at higher pressure. The characteristic features of structural phase transitions by temperature and by pressure were compared by introducing a reduced temperature and pressure. The dynamical property observed from the NSE measurement was different between the high-temperature phase and the high-pressure phase. These results indicate that the mechanism of the phase transition induced by temperature is different from that by pressure.

  19. A novel water-in-ionic liquid microemulsion and its interfacial effect on the activity of laccase.

    PubMed

    Xue, Luyan; Qiu, Huajun; Li, Ying; Lu, Lu; Huang, Xirong; Qu, Yinbo

    2011-02-01

    It is of great significance to develop an appropriate water-in-ionic liquid (W/IL) microemulsion suitable for the expression of the catalytic activity of a given enzyme. In this paper, the phase diagram of a new AOT/Triton X-100/H(2)O/[Bmim][PF(6)] pseudo ternary system is presented. With the aid of nonionic surfactant Triton X-100, AOT could be dissolved in hydrophobic ionic liquid [Bmim][PF(6)], forming a large single phase microemulsion region. The water-in-[Bmim][PF(6)] (W/IL) microemulsion domain was identified electrochemically by using K(3)Fe(CN)(6) as a probe. The existence of W/IL microemulsions was demonstrated spectrophotometrically by using CoCl(2) as a probe. New evidences from the FTIR spectroscopic study, which was first introduced to the W/IL microemulsion by substituting D(2)O for H(2)O to eliminate the spectral interference, demonstrated that there existed bulk water at larger ω(0) values (ω(0) was defined as the molar ratio of water to the total surfactant) in the W/IL microemulsion, which had remained unclear before. In addition to the inorganic salts, biomacromolecule laccase could be solubilized in the W/IL microemulsion. The laccase hosted in the microemulsion exhibited a catalytic activity and the activity could be regulated by the composition of the interfacial membrane.

  20. Kinetics and mechanism of the cutinase-catalyzed transesterification of oils in AOT reversed micellar system.

    PubMed

    Badenes, Sara M; Lemos, Francisco; Cabral, Joaquim M S

    2011-11-01

    The kinetics of the enzymatic transesterification between a mixture of triglycerides (oils) and methanol for biodiesel production in a bis(2-ethylhexyl) sodium sulfosuccinate (AOT)/isooctane reversed micellar system, using recombinant cutinase from Fusarium solani pisi as a catalyst, was investigated. In order to describe the results that were obtained, a mechanistic scheme was proposed, based on the literature and on the experimental data. This scheme includes the following reaction steps: the formation of the active enzyme-substrate complex, the addition of an alcohol molecule to the complex followed by the separation of a molecule of the fatty acid alkyl ester and a glycerol moiety, and release of the active enzyme. Enzyme inhibition and deactivation effects due to methanol and glycerol were incorporated in the model. This kinetic model was fitted to the concentration profiles of the fatty acid methyl esters (the components of biodiesel), tri-, di- and monoglycerides, obtained for a 24 h transesterification reaction performed in a stirred batch reactor under different reaction conditions of enzyme and initial substrates concentration.

  1. Some characteristics of microemulsions in sodium dioleyl phosphate/n-heptane/brine system

    SciTech Connect

    Nonaka, Gen; Harada, Makoto; Shioi, Akihisa; Goto, Masahiro; Nakashio, Fumiyuki

    1995-12-01

    The behavior of microemulsions in the sodium dioleyl phosphate (SDOLP)/n-heptane system was investigated. This system provided a water-in-oil microemulsion without using a cosurfactant. The phase diagram of the WinsorII was determined. Along the phase boundary between the microemulsion and the excess brine solution, the small angle X-ray scattering, the viscosity, and the electric conductivity of the microemulsions were measured. SDOLP provided the spherical aggregates, which were highly isolated from each other even in the concentrated region of the aggregates. These characteristics were estimated to be attributed to peculiar packing of the hydrocarbon chain tails of SDOLP due to cis-double bonds.

  2. Analysis and antibacterial activity of Nigella sativa essential oil formulated in microemulsion system.

    PubMed

    Shaaban, Hamdy A; Sadek, Zainab; Edris, Amr E; Saad-Hussein, Amal

    2015-01-01

    The Essential oil (EO) of Nigella sativa (black cumin) was extracted from the crude oil and the volatile constituents were characterized using gas chromatographic analysis. The EO was formulated in water-based microemulsion system and its antibacterial activity against six pathogenic bacteria was evaluated using the agar well diffusion method. This activity was compared with two other well known biologically active natural and synthetic antimicrobials namely eugenol and Ceftriaxone(®). Results showed that N. sativa EO microemulsion was highly effective against S. aureus, B. cereus and S. typhimurium even at the lowest tested concentration of that EO in the microemulsion (100.0 μg/well). Interestingly, the EO microemulsion showed higher antibacterial activity than Ceftriaxone solution against S. typhimurium at 400.0 μg/well and almost comparable activity against E. coli at 500.0 μg/well. No activity was detected for the EO microemulsion against L. monocytogenes and P. aeruginosa. Eugenol which was also formulated in microemulsion was less effective than N. sativa EO microemulsion except against P. aeruginosa. The synthetic antibiotic (Ceftriaxone) was effective against most of the six tested bacterial strains. This work is the first report revealing the formulation of N. sativa EO in microemulsion system and investigating its antibacterial activity. The results may offer potential application of that water-based microemulsion in controlling the prevalence of some pathogenic bacteria.

  3. Illuminating microemulsions: ionic liquid-CdS quantum dots hybrid materials as potential white light harvesting systems.

    PubMed

    Damarla, Krishnaiah; Bharmoria, Pankaj; Rao, K Srinivasa; Gehlot, Praveen Singh; Kumar, Arvind

    2016-05-07

    Microemulsions (MEs) comprising of 2-hydroxyethylammonium formate, (HO-EAF), isooctane and dioctylsulfosuccinate proliniumisopropylester ([ProC3]AOT) have been constructed and used to prepare and stabilize CdS Quantum Dots (QDs) at room temperature. Such hybrid materials exhibited tunable light emission wherein the photoluminescence chromaticity could be precisely adjusted to pure white with a quantum efficiency (QE) of ∼43%, by adjusting the droplet size of MEs.

  4. Process of forming compounds using reverse micelle or reverse microemulsion systems

    DOEpatents

    Linehan, John C.; Fulton, John L.; Bean, Roger M.

    1998-01-01

    The present invention is directed to a process for producing a nanometer-sized metal compound. The process comprises forming a reverse micelle or reverse microemulsion system comprising a polar fluid in a non-polar or low-polarity fluid. A first reactant comprising a multi-component, water-soluble metal compound is introduced into the polar fluid in a non-polar or low-polarity fluid. This first reactant can be introduced into the reverse micelle or reverse microemulsion system during formation thereof or subsequent to the formation of the reverse micelle or microemulsion system. The water-soluble metal compound is then reacted in the reverse micelle or reverse microemulsion system to form the nanometer-sized metal compound. The nanometer-sized metal compound is then precipitated from the reverse micelle or reverse microemulsion system.

  5. Percolation phenomenon of calcium bis(2-ethylhexyl) sulfosuccinate water-in-oil microemulsions by conductivity and dielectric spectroscopy measurements.

    PubMed

    Capuzzi, G; Baglioni, P; Gambi, C M; Sheu, E Y

    1999-07-01

    The sodium counterion (Na+) of the sodium bis(2-ethylhexyl) sulfosuccinate (AOT) surfactant was exchanged with calcium Ca2+ to investigate the counterion charge effect on the structure of water in normal decane microemulsions. Ohmic conductivity and dielectric permittivity measurements were performed on samples at constant water to surfactant mole ratio [water]/[Ca(AOT)(2)]=26.6. Increasing the volume fraction of the dispersed phase phi, a percolation phenomenon was observed at the constant temperature of 25 degrees C. The percolation threshold was found at phi approximately 15% by Ohmic conductivity and static dielectric permittivity studied as a function of phi, and by the frequency dependence of the complex permittivity. Critical exponents typical of the static percolation mechanism (formation of bicontinuous microemulsions) were found below and above threshold. The comparison of these results obtained for the two different counterions, Ca2+ and Na+, in AOT surfactant water in normal decane microemulsions allows detection of an important difference. The percolation below threshold is dynamic for the sodium-based microemulsions, accounting for the formation of clusters of droplets, whereas calcium-based microemulsions show a static percolation. For this system, the coalescence of droplets begins to occur below threshold at phi approximately 12%.

  6. Preparation and evaluation of topical microemulsion system containing metronidazole for remission in rosacea.

    PubMed

    Tirnaksiz, Figen; Kayiş, Ayşegül; Çelebi, Nevin; Adişen, Esra; Erel, Arzu

    2012-01-01

    The aim of this study was to prepare a topical water-in-oil type microemulsion containing metronidazole and to compare its effectiveness with a commercial gel product in the treatment of rosacea. A pseudo-ternary phase diagram (K(m)=2:1) was constructed using lecithin/butanol/isopropyl myristate/water. The microemulsion was chosen from the microemulsion region in the phase diagram. The formulation was a water-in-oil type microemulsion (droplet size: 11.6 nm, viscosity: 457.3 mPa·s, conductivity: 1.5 µs/cm, turbidity: 6.89 NTU) and the addition of the metronidazole did not alter the properties of the system. The release experiment showed that the release rate of metronidazole from the commercial gel product was higher than that of the microemulsion. Stability experiments showed that the metronidazole microemulsion remained stable for at least 6 months; none of the characteristic properties of the microemulsion had changed, the system retained its clarity and there was no sign that crystallization of metronidazole has occurred. Microemulsion was compared to a gel product in a randomized, double-blind, baseline-controlled, split-face clinical trial for the treatment of patients. After the 6-week treatment period there was a statistically significant difference in reduction of the main symptoms of rosacea. Of the patients treated with the microemulsion, 17% experienced complete relief from inflammatory lesions, and 50% from erythema. The microemulsion resulted in complete relief in 38% of the patients with telangiectasia while the commercial product did not provide any relief of telangiectasia symptoms. In conclusion, the microemulsion containing metronidazole was found to be more effective in reducing the symptoms of rosacea compared to the commercial gel product.

  7. Microemulsions in supercritical hydrochlorofluorocarbons

    SciTech Connect

    Jackson, K.; Fulton, J.L.

    1996-10-30

    We report the properties of sodium bis(2-ethylhexyl) sulfosuccinate (AOT) microemulsions formed in supercritical hydrochlorofluorocarbons (HCFCs), hydrofluorocarbons, and flourocarbons. The fluids used in this study include compounds that are of low toxicity and flammability and that are expected to remain environmentally acceptable well into the next century (e.g., 1,1,1, 2-tetrafluoroethane (R134a) and chlorodifluoromethane (R22)). We show that it is possible to form a water-in-oil type of microemulsion in a low molecular weight HCFC (R22). In addition to these HCFCs, We also review the ability to form microemulsions in 14 other fluids (ethane, propene, propane, n-butane, n-pentane, n-haxane, isobutane, isooctane, difluoromethane, trifluoromethane, hexafluoroethane, sulfur haxafluoride, xenon, and carbon dioxide) at conditions just above or below the critical point (0.75 < T/T{sub c} <1.1) of the solvent. We report extensively the phase behavior of AOT and didodecyldimethylammonium bromide microemulsions formed in a supercritical HCFC, R22. We show that microemulsions in HCFCs are practical alternatives to other fluids, such as supercritical carbon dioxide. 56 refs., 7 figs., 1 tab.

  8. Short communication: in vivo evaluation of microemulsion system for oral and parenteral delivery of rutaecarpine to rats.

    PubMed

    Yong, Chul-Soon; Park, Byung-Joo; Kim, Dong-Hyun; Yoo, Bong-Kyu; Woo, Jong Soo; Bhamdari, Krisna; Jahng, Yurngdong; Choi, Han-Gon; Lee, Mann Hyung

    2007-05-01

    Rutaecarpine-loaded microemulsion composed of 10.8% polyethylene glycol 400, 7.2% Tween 80, 20% caster oil, and 62% water were previously reported to be physically and chemically stable for at least 6 months. For the development of a Rutaecarpine-loaded microemulsion, here we studied the pharmacokinetic profiles of rutaecarpine after oral and intravenous administration of rutaecarpine-loaded microemulsion compared to suspension. The AUC of rutaecarpine from microemulsion after oral and intravenous administration increased about three-fold compared with that from suspension. Furthermore, the rutaecarpine-loaded microemulsion gave significantly higher AUC and Cmax than did suspension, suggesting that the oral bioavailability of rutaecarpine in this microemulsion system could be enhanced due to the enhanced solubility of rutaecarpine by microemulsion. Thus, our results indicated that the microemulsion system composed of castor oil, polyethylene glycol 400, Tween 80, and water could be a more effective oral and parenteral dosage form for rutaecarpine.

  9. Molecular characterization of water and surfactant AOT at nanoemulsion surfaces.

    PubMed

    Hensel, Jennifer K; Carpenter, Andrew P; Ciszewski, Regina K; Schabes, Brandon K; Kittredge, Clive T; Moore, Fred G; Richmond, Geraldine L

    2017-07-31

    Nanoemulsions and microemulsions are environments where oil and water can be solubilized in one another to provide a unique platform for many different biological and industrial applications. Nanoemulsions, unlike microemulsions, have seen little work done to characterize molecular interactions at their surfaces. This study provides a detailed investigation of the near-surface molecular structure of regular (oil in water) and reverse (water in oil) nanoemulsions stabilized with the surfactant dioctyl sodium sulfosuccinate (AOT). Vibrational sum-frequency scattering spectroscopy (VSFSS) is used to measure the vibrational spectroscopy of these AOT stabilized regular and reverse nanoemulsions. Complementary studies of AOT adsorbed at the planar oil-water interface are conducted with vibrational sum-frequency spectroscopy (VSFS). Jointly, these give comparative insights into the orientation of interfacial water and the molecular characterization of the hydrophobic and hydrophilic regions of AOT at the different oil-water interfaces. Whereas the polar region of AOT and surrounding interfacial water molecules display nearly identical behavior at both the planar and droplet interface, there is a clear difference in hydrophobic chain ordering even when possible surface concentration differences are taken into account. This chain ordering is found to be invariant as the nanodroplets grow by Ostwald ripening and also with substitution of different counterions (Na:AOT, K:AOT, and Mg:AOT) that consequently also result in different sized nanoparticles. The results paint a compelling picture of surfactant assembly at these relatively large nanoemulsion surfaces and allow for an important comparison of AOT at smaller micellar (curved) and planar oil-water interfaces.

  10. Small-angle neutron scattering study of a dense microemulsion system formed with an ionic liquid.

    PubMed

    Kang, T; Qian, S; Smith, G S; Do, C; Heller, W T

    2017-09-12

    Mixtures of water, octane and 1-octanol with 1-tetradecyl-3-methylimidazolium chloride (C14MIM·Cl), often referred to as a surface active ionic liquid (SAIL), form water-in-oil microemulsions that have potential application as extraction media for various metal ions. Here, we present a structural study by small-angle neutron scattering (SANS) of dense microemulsions formed by surfactant-rich mixtures of these four compounds to understand how the SAIL can be used to tune the structures and properties of the microemulsions. The SANS experiments revealed that the microemulsions formed are composed of two phases, a water-in-oil microemulsion and a bicontinuous microemulsion, which becomes the dominant phase at high surfactant concentration. In this concentration regime, the surfactant film becomes more rigid, having a higher bending modulus that results from the parallel stacking of the imidazolium ring of the SAIL. At lower surfactant concentrations, the molecular packing of the SAIL does not change with the water content of the microemulsion. The results presented here correlate well with previously observed changes in the interaction between the IL cation and metal ions (Y. Tong, L. Han and Y. Yang, Ind. Eng. Chem. Res., 2012, 51, 16438-16443), while the capacity of the microemulsion system for water remains high enough for using the system as an extraction medium.

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

    PubMed

    Yin, Tianxiang; Wang, Mingjie; Tao, Xiaoyi; Shen, Weiguo

    2016-12-20

    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 β 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.

  12. Design and Characterization of Microemulsion Systems for Naproxen

    PubMed Central

    Moghimipour, Eskandar; Salimi, Anayatollah; Eftekhari, Soroosh

    2013-01-01

    Purpose: This research was aimed to formulate and characterize a microemolsion systems as a topical delivery system of naproxen for relief of symptoms of rheumatoid arthritis, osteoarthritis and treatment of dysmenorrheal. Methods: ME formulations prepared by mixing of appropriate amount of surfactant including Tween 80 and Span 80, co-surfactant such as propylene glycol (PG) and oil phase including Labrafac PG – transcutol P (10:1 ratio). The prepared microemolsions were evaluated regarding their particle size, zeta potential, conductivity, stability, viscosity, differential scanning calorimetry (DSC), scanning electron microscopy (SEM), refractory index (RI) and pH. Results: The mean droplets size of microemulsion formulation were in the range of 7.03 to 79.8 nm, and its refractory index (RI) and pH were 1.45 and 6.75, respectively. Viscosity range was 253.73- 802.63cps. Drug release profile showed that 26.15% of the drug released in the first 24 hours of experiment. Also, Hexagonal and bicontinuous structures were seen in the SEM photograph of the microemulsions. Conclusion: characterization, physicochemical properties and in vitro release were dependent upon the contents of S/C ratio, water and, oil phase percentage in formulations. Also, ME-6 may be preferable for topical naproxen formulation. PMID:24312814

  13. Effect of Protein Incorporation on the Nanostructure of the Bicontinuous Microemulsion Phase of Winsor-III Systems: A Small-Angle Neutron Scattering Study

    DOE PAGES

    Hayes, Douglas G.; Gomez del Rio, Javier A.; Ye, Ran; ...

    2015-01-20

    Small-angle neutron scattering (SANS) analysis using the Teubner₋Strey model has been employed to evaluate the effect of protein incorporation into the middle, bicontinuous microemulsion (BμE) phase of Winsor-III (WIII) systems formed by an aerosol-OT (AOT)/alkyl ethoxylate mixed surfactant system to understand better the extraction of proteins into and out of BμEs and to study the effect of proteins on a system that serves as a biomimetic analog of cell membranes. Under conditions of high salinity, the incorporation of positively charged proteins cytochrome c, lysozyme, and α-chymotrypsin, near their solubilization limit in the BμEs promoted the release of water and oilmore » from the BμEs, a decrease in the quasi-periodic repeat distance (d), an increase in ordering (a decrease in the amphiphilicity factor, fa) for the surfactant monolayers, and a decrease in the surface area per surfactant headgroup, suggesting that the proteins affected the self-assembly of components in the BμE phase and produced Debye shielding of AOTs sulfonate headgroup. For WIII systems possessing lower salinity, cytochrome c reduced the efficiency of surfactant in the BμE phase, noted by increases in d and fa, suggesting that the enzyme and AOT underwent ion pairing. We find that the results of this study demonstrate the importance of ionic strength to modulate proteinsurfactant interactions, which in turn will control the release of proteins encapsulated in the BμEs, relevant to WIII-based protein extraction and controlled release from BμE delivery systems, and demonstrate the utility of BμEs as a model system to understand the effect of proteins on biomembranes.« less

  14. Effect of Protein Incorporation on the Nanostructure of the Bicontinuous Microemulsion Phase of Winsor-III Systems: A Small-Angle Neutron Scattering Study

    SciTech Connect

    Hayes, Douglas G.; Gomez del Rio, Javier A.; Ye, Ran; Urban, Volker S.; Pingali, Sai Venkatesh; O’Neill, Hugh M.

    2015-01-20

    Small-angle neutron scattering (SANS) analysis using the Teubner₋Strey model has been employed to evaluate the effect of protein incorporation into the middle, bicontinuous microemulsion (BμE) phase of Winsor-III (WIII) systems formed by an aerosol-OT (AOT)/alkyl ethoxylate mixed surfactant system to understand better the extraction of proteins into and out of BμEs and to study the effect of proteins on a system that serves as a biomimetic analog of cell membranes. Under conditions of high salinity, the incorporation of positively charged proteins cytochrome c, lysozyme, and α-chymotrypsin, near their solubilization limit in the BμEs promoted the release of water and oil from the BμEs, a decrease in the quasi-periodic repeat distance (d), an increase in ordering (a decrease in the amphiphilicity factor, fa) for the surfactant monolayers, and a decrease in the surface area per surfactant headgroup, suggesting that the proteins affected the self-assembly of components in the BμE phase and produced Debye shielding of AOTs sulfonate headgroup. For WIII systems possessing lower salinity, cytochrome c reduced the efficiency of surfactant in the BμE phase, noted by increases in d and fa, suggesting that the enzyme and AOT underwent ion pairing. We find that the results of this study demonstrate the importance of ionic strength to modulate proteinsurfactant interactions, which in turn will control the release of proteins encapsulated in the BμEs, relevant to WIII-based protein extraction and controlled release from BμE delivery systems, and demonstrate the utility of BμEs as a model system to understand the effect of proteins on biomembranes.

  15. Microemulsion based intranasal delivery system for treatment of insomnia.

    PubMed

    Porecha, Sheetal; shah, Tapan; Jogani, Viral; Naik, Sachin; Misra, Ambikanandan

    2009-04-01

    The aim of this investigation was to prepare and characterize microemulsions/mucoadhesive microemulsions of Diazepam (D), Lorazepam (L) and Alprazolam (A), evaluate their pharmacodynamic performances by performing comparative sleep induction studies in male albino rats to assess their role in effective management of insomnia patients. Microemulsions of Diazepam (DME), Lorazepam (LME) and Alprazolam (AME) were prepared by titration method and characterized for drug content, globule size distribution and zeta potential, nasal toxicity and sleep induction. DME, LME and AME were transparent and stable with mean globule size and zeta potential in the range of 95.6 nm to 141.7 nm and -2.205 to -0.111 mV respectively. The prepared microemulsions exhibited reversible nasal toxicity. Onset of sleep and duration of sleep were observed in the following order: Lorazepam > Alprazolam>Diazepam. Faster onset of sleep following intranasal administration of microemulsions (<20 min) compared to oral administration (29-33 min) and control group (>45 min) for all three drugs suggested selective nose-to-brain transport of drug(s). Intranasal administration of microemulsion based formulations resulted in even faster onset of sleep (<12 min) with intranasal mucoadhesive microemulsion(s) resulting in fastest onset of sleep (<9 min). Duration of sleep was longest with the intranasal mucoadhesive microemulsions. These results are suggestive of larger extent of distribution of drug(s) to brain after intranasal administration of mucoadhesive microemulsion(s). These results are further corroborated with by loss or rightening reflex and startle reflex at earlier time points (within 10 min and 15 min respectively) with mucoadhesive microemulsions. Thus, the results of this investigation indicated rapid and larger extent of drug transport to the rat brain resulting in rapid induction of sleep followed by prolonged duration of sleep in rats following intranasal administration of mucoadhesive

  16. Biocatalysis in water-in-ionic liquid microemulsions: a case study with horseradish peroxidase.

    PubMed

    Moniruzzaman, M; Kamiya, N; Goto, M

    2009-01-20

    In this article we report the first results on the enzymatic activity of horseradish peroxidase (HRP) microencapsulated in water-in-ionic liquid (w/IL) microemulsions using pyrogallol as the substrate. Toward this goal, the system used in this study was composed of anionic surfactant AOT (sodium bis(2-ethyl-1-hexyl)sulfosuccinate)/hydrophobic IL [C(8)mim][Tf(2)N] (1-octyl-3-methyl imidazolium bis(trifluoromethylsulfonyl)amide)/water/1-hexanol. In this system, the catalytic activity of HRP was measured as a function of substrate concentrations, W(0) (molar ratio of water to surfactant), pH, and 1-hexanol content. The curve of the activity-W(0) profile was found to be hyperbolic for the new microemulsion. The apparent Michaelis-Menten kinetic parameters (k(cat) and K(m)) were estimated and compared to those obtained from a conventional microemulsion. Apparently, it was found that HRP-catalyzed oxidation of pyrogallol by hydrogen peroxide in IL microemulsuions is much more effective than in a conventional AOT/water/isooctane microemulsion. The stability of HRP solubilized in the newly developed w/IL microemulsions was examined, and it was found that HRP retained almost 70% of its initial activity after incubation at 28 degrees C for 30 h.

  17. Solubility dynamic of methyl yellow and carbon black in microemulsions and lamellar liquid crystal of water, non ionic surfactants and cyclohexane system

    NASA Astrophysics Data System (ADS)

    Amran, A.; Harfianto, R.; Dewi, W. Y.; Beri, D.; Putra, A.

    2016-02-01

    Solubility dynamics of methyl yellow and carbon black in microemulsions and liquid crystals of water, non-ionic surfactants and cyclohexane system, have been investigated. Actually, solubility dynamics of these dyes both in microemulsion (w/o microemulsions) and the lamellar liquid crystal (LLC) were strongly related to the chemical composition, nature and characteristics of microemulsions and the lamellar liquid crystals.

  18. Microemulsion of babassu oil as a natural product to improve human immune system function

    PubMed Central

    Pessoa, Rafael Souza; França, Eduardo Luzia; Ribeiro, Elton Brito; Lanes, Patrícia Kelly Dias; Chaud, Natalina Galdeano Abud; Moraes, Lucélia Campelo Albuquerque; Honorio-França, Adenilda Cristina

    2015-01-01

    Background The aim of this study was to develop and characterize a babassu oil microemulsion system and determine the effect of this microemulsion on the functional activity of phagocytes. Methods The microemulsion was formulated using distilled water, babassu as the oil phase component, Sorbitan monooleate-Span 80® (SP), Polysorbate 80-Tween 80® (TW), and 1-butanol (BT). Pseudoternary diagrams were prepared, and microemulsion diagram regions were preselected. Rheological characterization and preliminary and accelerated stability tests were performed. The effect of the microemulsion on the interactions between leukocytes and bacteria was determined by superoxide release, phagocytosis, and microbicidal activity. Results The developed formulation SP/TW/BT (4.2/4.8/1.0) was classified as oil/water, showed a Newtonian profile, and had linear viscosity. When we assessed the interaction of the microemulsion or babassu oil with phagocytes, we observed an increase in superoxide, phagocytosis, and microbicidal activity. Conclusion The babassu oil microemulsion system is an option for future applications, including for vaccine delivery systems. Babassu oil is a natural product, so is an alternative for future immunotherapy strategies, in particular for infectious diseases. PMID:25565770

  19. Novel microemulsions: ionic liquid-in-ionic liquid.

    PubMed

    Cheng, Siqing; Zhang, Jianling; Zhang, Zhaofu; Han, Buxing

    2007-06-28

    The hydrophobic IL 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim][PF(6)]) can be dispersed in hydrophilic IL propylammonium formate (PAF) with the aid of surfactant AOT, and [bmim][PF(6)]-in-PAF microemulsions are formed.

  20. Solubilization of simvastatin and phytosterols in a dilutable microemulsion system.

    PubMed

    Fisher, Sarah; Wachtel, Ellen J; Aserin, Abraham; Garti, Nissim

    2013-07-01

    The usual treatment of hypercholesterolemia includes a class of drugs known as statins (simvastatin among them), which inhibit the production of cholesterol. Another way of reducing cholesterol levels is with the use of phytosterols, which reduce the transport of exogenic cholesterol from the intestine into the blood stream. The two treatments can be combined, achieving an additive effect. However, both simvastatin and phytosterols are practically insoluble in water, and therefore their absorption and activity are low. Nanosized self-assembled structured liquid systems are modified microemulsions that present an alternative pathway for improving the bioavailability of poorly water-soluble drugs. The goal of this study was to solubilize the maximal quantity of both simvastatin and phytosterols in a single, fully dilutable microemulsion system. We constructed a water-dilutable liquid drug delivery system that includes sucrose monolaurate, propylene glycol, and oleyl lactate. This system exhibits high solubilization capacity for both simvastatin (7.0 wt%) and phytosterols (3.5 wt%) when each is solubilized separately in a water-free concentrate. When simvastatin and phytosterols were solubilized together at a wt ratio of 2.5:1, maximum solubilization was obtained with 4.7 wt% simvastatin and 1.9 wt% phytosterols. Structural and analytical methods were applied including rheology, DSC, SD-NMR, SAXS, and cryo-TEM. The water-free "concentrate" consisted of direct micelles for which propylene glycol served as the hydrophilic phase. Upon water dilution, the direct micelles appear to form "lipophilic compounds dispersed in hydrophilic continuous phase". The solubilizates are located in the droplet core and/or at the interface.

  1. Microemulsion system with improved loading of piroxicam: a study of microstructure.

    PubMed

    Nazar, Muhammad Faizan; Khan, Asad Muhammad; Shah, Syed Sakhawat

    2009-01-01

    Formulation of a new oil-in-water (o/w) microemulsion composed of castor oil/Tween 80/ethanol/phosphate buffer for enhancing the loading capacity of an anti-inflammatory drug piroxicam has been accomplished. The pseudo-ternary phase diagram has been delineated at constant surfactant/cosurfactant ratio (1:2). The internal structure of so created four-component system was elucidated by means of an analysis of isotropic area magnitudes in the phase diagram. Conductivity (sigma), kinematic viscosity (keta), and surface tension (gamma) studies with the variation in Phiw (weight fraction of aqueous phase) show the occurrence of structural changes from water-in-oil (w/o) microemulsion to oil-in-water (o/w). Along with the solubility and partition studies of piroxicam in microemulsion components, the changes in the microstructure of the microemulsion after incorporation of drug have been evaluated using pH, sigma, gamma, keta, and density studies. Piroxicam, a poorly water-soluble drug displayed high solubility (1.0%) in an optimum microemulsion formulation using ethanol (55.0%), Tween 80 (26.5%), castor oil (7.5%), and phosphate buffer (11.0%). The results have shown that the microemulsion remained stable after the incorporation of piroxicam. Fluorescence spectra analysis taking pyrene as fluorescent probe was performed, and the results showed that pyrene was completely solubilized in the oil phases of the bicontinuous microemulsions. The fluorescence spectrum of the model drug piroxicam was used to probe the intramicellar region of nonionic microemulsion. The results showed that the piroxicam was localized in the interfacial film of microemulsion systems more deeply in the palisade layer with ethanol as the cosurfactant.

  2. Physicochemical characterization and evaluation of a microemulsion system for antimicrobial activity of glycerol monolaurate.

    PubMed

    Fu, Xiaowei; Feng, Fengqin; Huang, Bin

    2006-09-14

    The purpose of this study was to improve the depression, enhance the bioavailability, hence strengthen the antimicrobial ability of poorly water-soluble glycerol monolaurate (GML) by loading it in microemulsion system. Microemulsions were prepared with GML as oil, tweens as surfactant, and medium-and-short chain alcohols at different ratio as cosurfactants. The effect of the ratio of surfactant to cosurfactant on the stability of microemulsion was tested. And the effect of the composition and ratio of cosurfactant and the effect of potassium sorbate dissolved in water at different concentration on the area of O/W microemulsion region in pseudo-ternary phase diagrams were also investigated. The results showed that the microemulsion is most stable when the ratio of surfactant to cosurfactant was 3:2, the suitable cosurfactant is pentanol to dodecane at 2:1, the area of O/W microemulsion region in pseudo-ternary phase diagram increased with increasing content of potassium sorbate. The conclusion of this study was that GML loaded in microemulsion had much higher anti-microbial activity than GML alone.

  3. Partitioning behavior of an acid-cleavable, 1,3-dioxolane alkyl ethoxylate, surfactant in single and binary surfactant mixtures for 2- and 3-phase microemulsion systems according to ethoxylate head group size

    SciTech Connect

    Gomez Del Rio, Javier A; Hayes, Douglas G; Urban, Volker S

    2010-01-01

    Partition coefficients for a pH-degradable 1,3-dioxolane alkyl ethoxylate surfactant, 4-CH{sub 3}O (CH{sub 2}CH{sub 2}O){sub 5.6}-CH{sub 2}, 2,2-(CH{sub 2}){sub 12}CH{sub 3}, 2-(CH{sub 2}) CH{sub 3}, 1,3-dioxolane or ''cyclic ketal'' surfactant, CK-2,13-E{sub 5.6,ave}, between isooctane- and water-rich phases of 2- and 3-phase microemulsion systems (K{sub n}) were determined as functions of the ethoxylate size, n, and temperature for the neat surfactant and its binary surfactant mixtures, to understand the partitioning of alkyl ethoxylates possessing a broad distribution of ethoxylate size and to determine conditions required for formation of 3-phase microemulsion systems at an optimal temperature where phase separation occurs rapidly, important for protein purification via proteins selective partitioning to the middle phase, driven by affinity to the second surfactant of the binary mixture. A semi-empirical thermodynamic mathematical model described the partitioning data well, provided optimal temperature values consistent with phase diagrams and theory, and demonstrated that the tail region of CK-2,13-E{sub 5.6,ave} is more polar than the hydrophobes of fatty alcohol ethoxylates. The addition of Aerosol-OT (AOT) removed the temperature sensitivity of CK-2,13-E{sub 5.6,ave}s partitioning, producing 3-phase microemulsion systems between 20 C and 40 C. Analysis of the bottom phases of the 2- and 3-phase microemulsion systems formed by CK-2,13-E{sub 5.6,ave} via small-angle neutron scattering demonstrated the presence of spherical, monodisperse oil-in-water microemulsions.

  4. Partitioning behavior of an acid-cleavable, 1,3-dioxolane alkyl ethoxylate, surfactant in single and binary surfactant mixtures for 2- and 3-phase microemulsion systems according to ethoxylate head group size.

    PubMed

    Gomez del Rio, Javier; Hayes, Douglas G; Urban, Volker S

    2010-12-15

    Partition coefficients for a pH-degradable 1,3-dioxolane alkyl ethoxylate surfactant, 4-CH(3)O (CH(2)CH(2)O)(5.6)-CH(2), 2,2-(CH(2))(12)CH(3), 2-(CH(2)) CH(3), 1,3-dioxolane or "cyclic ketal" surfactant, CK-2,13-E(5.6,ave), between isooctane- and water-rich phases of 2- and 3-phase microemulsion systems (K(n)) were determined as functions of the ethoxylate size, n, and temperature for the neat surfactant and its binary surfactant mixtures, to understand the partitioning of alkyl ethoxylates possessing a broad distribution of ethoxylate size and to determine conditions required for formation of 3-phase microemulsion systems at an optimal temperature where phase separation occurs rapidly, important for protein purification via proteins' selective partitioning to the middle phase, driven by affinity to the second surfactant of the binary mixture. A semi-empirical thermodynamic mathematical model described the partitioning data well, provided optimal temperature values consistent with phase diagrams and theory, and demonstrated that the tail region of CK-2,13-E(5.6,ave) is more polar than the hydrophobes of fatty alcohol ethoxylates. The addition of Aerosol-OT (AOT) removed the temperature sensitivity of CK-2,13-E(5.6,ave)s partitioning, producing 3-phase microemulsion systems between 20 °C and 40 °C. Analysis of the bottom phases of the 2- and 3-phase microemulsion systems formed by CK-2,13-E(5.6,ave) via small-angle neutron scattering demonstrated the presence of spherical, monodisperse oil-in-water microemulsions.

  5. "Black spots" in a surfactant-rich Belousov-Zhabotinsky reaction dispersed in a water-in-oil microemulsion system.

    PubMed

    Kaminaga, Akiko; Vanag, Vladimir K; Epstein, Irving R

    2005-05-01

    The Belousov-Zhabotinsky (BZ) reaction dispersed in water-in-oil aerosol OT (AOT) microemulsion has been studied at small radius R(d) of water nanodroplets (R(d) (nm) congruent with0.17omega,omega = [H(2)O][AOT] = 9). Stationary spotlike and labyrinthine Turing patterns are found close to the fully oxidized state. These patterns, islands of high concentration of the reduced state of the Ru(bpy)(3) (2+) catalyst, can coexist either with "black" reduction waves or, under other conditions, with the "white" oxidation waves usually observed in the BZ reaction. The experimental observations are analyzed with the aid of a new Oregonator-like model and qualitatively reproduced in computer simulations.

  6. Protein transduction domain-containing microemulsions as cutaneous delivery systems for an anticancer agent.

    PubMed

    Pepe, Dominique; McCall, Melissa; Zheng, Haian; Lopes, Luciana B

    2013-05-01

    In this study, we developed cationic microemulsions containing a protein transduction domain (penetratin) for optimizing paclitaxel localization within the skin. Microemulsions were prepared by mixing a surfactant blend (BRIJ:ethanol:propylene glycol 2:1:1, w/w/w) with monocaprylin (oil phase) at 1.3:1 ratio, and adding water at 30% (ME-30), 43% (ME-43), and 50% (ME-50). Electrical conductivity and viscosity measurements indicated that ME-30 is most likely a bicontinuous system, whereas ME-43 and ME-50 are water continuous. Their irritation potential, studied in bioengineered skin equivalents, decreased as aqueous content increased. Because ME-50 was not stable in the presence of paclitaxel (0.5%), ME-43 was selected for penetratin incorporation (0.4%). The microemulsion containing penetratin (ME-P) displayed zeta potential of +5.2 mV, and promoted a 1.8-fold increase in paclitaxel cutaneous (but not transdermal) delivery compared with the plain ME-43, whereas the enhancement promoted by another cationic microemulsion containing phytosphingosine was 1.3-fold. Compared with myvacet oil, ME-P promoted a larger increase on transepidermal water loss (twofold) than the plain or the phytosphingosine-containing microemulsions (1.5-fold), suggesting that penetratin addition increases the barrier-disrupting and penetration-enhancing effects of microemulsions. The ratio Δcutaneous/Δtransdermal delivery promoted by ME-P was the highest among the formulations, suggesting its potential for drug localization within cutaneous tumor lesions.

  7. Enhancement of the skin permeation of clindamycin phosphate by Aerosol OT/1-butanol microemulsions.

    PubMed

    Junyaprasert, Varaporn Buraphacheep; Boonsaner, Panee; Leatwimonlak, Sujitra; Boonme, Prapaporn

    2007-08-01

    Microemulsions of water/isopropyl palmitate (IPP)/Aerosol OT (AOT)/1-butanol were developed as alternative formulations for topical delivery of clindamycin phosphate. Effect of AOT:1-butanol ratios on microemulsion region existence in the pseudoternary phase diagrams was investigated. The 2:1 AOT:1-butanol provided the largest microemulsion region. Five microemulsions of 1% w/w clindamycin phosphate were prepared and characterized. The permeation through human epidermis of the microemulsions was evaluated and compared with the 70% isopropanol solution using modified Franz diffusion cells. The drug permeation from all microemulsions was found to be significantly greater than that from the solution, indicating the enhancement of the skin permeation by the microemulsions. Within the same microemulsion type, the drug permeation increased with increasing the amount of AOT:1-butanol. The drug permeation from oil-in-water (o/w) microemulsions was relatively higher than that from water-in-oil (w/o) microemulsions. In addition, all microemulsions were stable for at least three months at 30 +/- 1 degrees C.

  8. Stability and comparative analysis of AOT/water/isooctane reverse micelle system using dynamic light scattering and molecular dynamics.

    PubMed

    Vasquez, V R; Williams, B C; Graeve, O A

    2011-03-31

    We use molecular dynamics (MD) and dynamic light scattering (DLS) measurements to analyze the size of reverse micellar structures in the AOT-water-isooctane system at different water-to-surfactant ratios at ambient temperature and pressure. We find good qualitative agreement for the size and morphology behavior of the reverse micelle structures between molecular dynamics calculations and DLS measurements; however, the average values for the reverse micelle size distributions are systematically larger for the DLS measurements. The latter tends to capture the average hydrodynamic size of the structures based on self-diffusion rather than the average physical size as measured in MD simulations, explaining the systematic deviations observed. The combination of MD with DLS allows a better interpretation of the experimental results, in particular for conditions where the structures are nonspherical, commonly observed at lower water-to-surfactant ratios. We also present and analyze the effect of zirconyl chloride on the micellar size distributions in this system. These type of salts are common for reverse micellar synthesis processes. We find that zirconyl chloride affects significantly the size distributions.

  9. Optimized microemulsions and solid microemulsion systems of simvastatin: characterization and in vivo evaluation.

    PubMed

    Dixit, Rahul P; Nagarsenker, Mangal S

    2010-12-01

    The study describes development of solid microemulsions (SME) for improved delivery of simvastatin (SMV). Pseudo-ternary phase diagrams were constructed and MEs were optimized for oil and drug content. SMEs were prepared using colloidal silicon dioxide to adsorb the liquid ME. MEs were characterized for mean globule size in aqueous medium and the SMEs were evaluated for powder characteristics, mean globule size after dilution with water, dissolution profile and for in vivo efficacy in rats. X-ray diffraction studies indicated complete amorphization and/or solubilization of SMV in the SMEs. It was supported by scanning electronic microscopic studies, which did not show evidence of precipitation of the drug on the surface of the carrier. Dissolution studies revealed remarkable increase in dissolution of the drug as compared to plain drug. All the formulations provided significant reduction in the total cholesterol levels in hyperlipidemic rats with reference to rats of control group (p < 0.05). The proposed SMEs have potential to deliver water insoluble drugs like SMV by oral route for better efficacy.

  10. Pentanary cross-diffusion in water-in-oil microemulsions loaded with two components of the Belousov-Zhabotinsky reaction.

    PubMed

    Rossi, Federico; Vanag, Vladimir K; Epstein, Irving R

    2011-02-11

    We measure cross-diffusion coefficients in a five-component system, an aerosol OT (AOT) water-in-oil microemulsion loaded with two constituents of the Belousov-Zhabotinsky (BZ) reaction (H(2) O/AOT/BZ1/BZ2/octane). The species BZ1 is either NaBr, an inhibitor of the BZ reaction, or ferroin, a catalyst for the reaction. As species BZ2, we choose Br(2) , an intermediate in the reaction. The cross-diffusion coefficients between BZ1 and BZ2 are found to be negative, which can be understood in terms of complexation between these species. Using a four-variable model for the BZ reaction, we find that the cross-diffusion coefficients measured here can lead to a noticeable shift in the onset of Turing instability in the BZ-AOT system. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. Phase boundaries, structural characteristics, and NMR spectra of ionic liquid-in-oil microemulsions containing double chain surface active ionic liquid: a comparative study.

    PubMed

    Rao, Vishal Govind; Mandal, Sarthak; Ghosh, Surajit; Banerjee, Chiranjib; Sarkar, Nilmoni

    2013-02-07

    A method developed for the first time, to create a huge number of ionic liquid (IL)-in-oil microemulsions has been discussed in our earlier publication (Rao, V. G.; Ghosh, S.; Ghatak, C.; Mandal, S.; Brahmachari, U.; Sarkar, N. J. Phys. Chem. B 2012, 116, 2850-2855). Here, we present facile methods to adjust the structural parameters of microemulsions using different ionic liquids (ILs) as additives (polar phase). We have characterized ILs/[C(4)mim][AOT]/benzene ternary system by performing a phase behavior study, dynamic light scattering (DLS) measurements, and (1)H NMR measurements. The IL loading capacity of microemulsions (area of single phase region) (i) increases with increase in alkyl chain length of cation of ILs and follows the trend [C(6)mim][TF(2)N] > [C(4)mim][TF(2)N] > [C(2)mim][TF(2)N], (ii) increases with decrease in cation anion interaction strength of added ILs and follows the trend [C(4)mim][TF(2)N] > [C(4)mim][PF(6)] > [C(4)mim][BF(4)]. So depending on the IL used, the amount of IL within the core of microemulsions can be easily manipulated to directly affect the size of aggregates in microemulsions. The size increase with increasing R value (R value is defined as the molar ratio of RTILs to [C(4)mim][AOT]) was found to be maximum in the case of [C(2)mim][TF(2)N]/[C(4)mim][AOT]/benzene microemulsions and follows the trend [C(2)mim][TF(2)N] > [C(4)mim][TF(2)N] > [C(6)mim][TF(2)N]. However, the size increase was almost the same with increase in R value in the case of ILs with different anions. The most promising fact about IL-in-oil microemulsions is their high thermal stability compared to that of aqueous microemulsions, so we investigated the effect of temperature on size of aggregates in microemulsions at R = 1.0. It is evident from dynamic light scattering measurements that the aggregates in microemulsions remain monodisperse in nature with increasing temperature, and in all the cases, the size of aggregates in microemulsions decreases with

  12. Patterns in the Belousov-Zhabotinsky reaction in water-in-oil microemulsion induced by a temperature gradient.

    PubMed

    Carballido-Landeira, Jorge; Vanag, Vladimir K; Epstein, Irving R

    2010-04-21

    We investigate the effect of changing temperature in the ferroin-catalysed Belousov-Zhabotinsky (BZ) reaction dispersed in the water nanodroplets of a water-in-oil aerosol OT (AOT) microemulsion, which undergoes a temperature-induced percolation transition at about 38 degrees C. We observe stationary Turing patterns at temperatures in the range 15-35 degrees C and bulk oscillations at T = 40-55 degrees C. When a temperature gradient DeltaT is applied normal to a thin layer of the BZ-AOT reaction mixture, the range of patterns observed is dramatically expanded. Anti-phase oscillatory Turing patterns, leaping waves, and chaotic waves emerge, depending on the temperature gradient and the average temperature. These new patterns originate from the coupling between a low temperature Turing mode and a high temperature Hopf mode. Simulations with a simple model of the BZ-AOT system give good agreement with our experimental results.

  13. Collagen and hyaluronic acid hydrogel in water-in-oil microemulsion delivery systems.

    PubMed

    Kupper, Sylwia; Kłosowska-Chomiczewska, Ilona; Szumała, Patrycja

    2017-11-01

    The increase in skin related health issues has promoted interest in research on the efficacy of microemulsion in dermal and transdermal delivery of active ingredients. Here, we assessed the water-in-oil microemulsion capacity to incorporate two natural polymers, i.e. collagen and hyaluronic acid with low and high molecular weight. Systems were extensively characterized in terms of conductivity, phase inversion studies, droplet diameter, polydispersity index and rheological properties. The results of this research indicate that the structure and extent of water phase in microemulsions is governed by ratio and amount of surfactant mixture (sorbitan ester derivatives). However, results have also shown that collagen, depending upon the weight of the molecule and its surface activity, influence the droplet size of the microemulsions. While the hyaluronic acid, especially with high molecular weight, due to the water-binding ability and hydrogel formation alters the rheological properties of the microemulsion, thus providing viscous consistency of the formulation. Copyright © 2017 Elsevier Ltd. All rights reserved.

  14. Structure-Activity Relationship of a U-Type Antimicrobial Microemulsion System

    PubMed Central

    Zhang, Hui; Taxipalati, Maierhaba; Yu, Liyi; Que, Fei; Feng, Fengqin

    2013-01-01

    The structure-activity relationship of a U-type antimicrobial microemulsion system containing glycerol monolaurate and ethanol at a 1∶1 mass ratio as oil phase and Tween 20 as surfactant were investigated along a water dilution line at a ratio of 80∶20 mass% surfactant/oil phase, based on a pseudo-ternary phase diagram. The differential scanning calorimetry results showed that in the region of up to 33% water, all water molecules are confined to the hydrophilic core of the reverse micelles, leading to the formation of w/o microemulsion. As the water content increases, the water gains mobility, and transforms into bicontinuous in the region of 33–39% water, and finally the microemulsion become o/w in the region of above 39% water. The microstructure characterization was confirmed by the dynamic light scattering measurements and freeze-fracture transmission electron microscope observation. The antimicrobial activity assay using kinetics of killing analysis demonstrated that the microemulsions in w/o regions exhibited relatively high antimicrobial activity against Escherichia coli and Staphylococcus aureus due to the antimicrobial oil phase as the continuous phase, while the antimicrobial activity started to decrease when the microemulsions entered the bicontinuous region, and decreased rapidly as the water content increased in the o/w region, as a result of the dilution of antimicrobial oil droplets in the aqueous continuous phase. PMID:24204605

  15. Structure-activity relationship of a u-type antimicrobial microemulsion system.

    PubMed

    Zhang, Hui; Taxipalati, Maierhaba; Yu, Liyi; Que, Fei; Feng, Fengqin

    2013-01-01

    The structure-activity relationship of a U-type antimicrobial microemulsion system containing glycerol monolaurate and ethanol at a 1∶1 mass ratio as oil phase and Tween 20 as surfactant were investigated along a water dilution line at a ratio of 80∶20 mass% surfactant/oil phase, based on a pseudo-ternary phase diagram. The differential scanning calorimetry results showed that in the region of up to 33% water, all water molecules are confined to the hydrophilic core of the reverse micelles, leading to the formation of w/o microemulsion. As the water content increases, the water gains mobility, and transforms into bicontinuous in the region of 33-39% water, and finally the microemulsion become o/w in the region of above 39% water. The microstructure characterization was confirmed by the dynamic light scattering measurements and freeze-fracture transmission electron microscope observation. The antimicrobial activity assay using kinetics of killing analysis demonstrated that the microemulsions in w/o regions exhibited relatively high antimicrobial activity against Escherichia coli and Staphylococcus aureus due to the antimicrobial oil phase as the continuous phase, while the antimicrobial activity started to decrease when the microemulsions entered the bicontinuous region, and decreased rapidly as the water content increased in the o/w region, as a result of the dilution of antimicrobial oil droplets in the aqueous continuous phase.

  16. Three-component ionic microemulsions

    SciTech Connect

    Angel, L.R.; Evans, D.F.; Ninham, B.W.

    1983-02-17

    Necessary design features of microemulsions formed from cationic surfactant without any requirement for cosurfactant are illustrated by a study of microemulsions formed from didodecyldimethylammonium bromide in various oils. Ease of purification, preparation, and manipulation give this and related systems a considerable advantage over conventional systems in enhancing the understanding of microemulsions and emulsion behavior. 21 references.

  17. Water Solubilization Using Nonionic Surfactants from Renewable Sources in Microemulsion Systems.

    PubMed

    Szumała, Patrycja; Szeląg, Halina

    2012-07-01

    In this study the effect of temperature, NaCl and oils (hydrocarbons: C(8)-C(16)) on the formation and solubilization capacity of the systems of oil/monoacylglycerols (MAG):ethoxylated fatty alcohols (CEO(20))/propylene glycol (PG)/water was investigated. The effects of the surfactant mixture on the phase behavior and the concentration of water or oil in the systems were studied at three temperatures (50, 55, 60 °C) and with varied NaCl solutions (0.5; 2; 11%). Electrical conductivity measurement, FTIR spectroscopy and the DSC method were applied to determine the structure and type of the microemulsions formed. The dimension of the microemulsion droplets was characterized by dynamic light scattering. It has been stated that the concentration of CEO(20) has a strong influence on the shape and extent of the microemulsion areas. Addition of a nonionic surfactant to the mixture with MAG promotes an increase in the area of microemulsion formation in the phase diagrams, and these areas of isotropic region did not change considerably depending on the temperature, NaCl solution and oil type. It was found that, depending on the concentration of the surfactant mixture, it was possible to obtain U-type microemulsions with dispersed particles size distribution ranging from 25 to 50 nm and consisting of about 30-32% of the water phase in the systems. The conditions under which the microemulsion region was found (electrolyte and temperature-insensitive, comparatively low oil and surfactant concentration) could be highly useful in detergency.

  18. Theory for dynamical self arrest and gelation in microemulsions and the block copolymer systems

    SciTech Connect

    Wu, Sangwook

    2005-01-01

    The main purpose of this work is to investigate the glassy behavior of microemulsions and block copolymers. The origin of glassy behavior in microemulsions and block copolymers is frustration due to a competition between short-range interaction and long range interaction. According to the charge frustrated Ising model, the competition between ferromagnetic interaction and antiferromagnetic interaction is the origin of frustration in microemulsions. The competition between entropic effects and stoichiometric constraints responsible for the formation of micelles in microemulsions can lead to the emergence of a self generated glassy behavior in these systems. In the block copolymer, the competition between the repulsive short range interaction between monomers in polymer chains and the long range interaction by chemical bonds can lead to the emergence of a self generated glassy behavior. The criteria for the fluctuation induced first order transition and our microemulsion and block copolymer glasses are essentially the same. Both are a consequence of the large phase space of low energy excitations (14) (62) (all states with momenta q which fulfill |q| = qm) and are of at the most a moderate supercooling of the liquid state is required. This is strongly supported by the observation in Ref. (14) that the metastable states which are first to appear at a fluctuation induced first order transition are the ones build by a superposition of large amplitude waves of wavenumber qm, but with random orientations and phases, i.e. just the ones which form the metastable states of our microemulsion and block copolymer glass. (38)

  19. In vitro immunomodulatory effects of microemulsions with levamisole delivery systems on blood phagocytes interacting with Giardia lamblia.

    PubMed

    Hernandes, Mara Rosa Gil; Moraes, Lucélia Campelo Albuquerque; Ribeiro, Elton Brito; Fagundes, Danny Laura Gomes; Honorio-França, Adenilda Cristina; França, Eduardo Luzía

    2017-06-01

    Giardiasis is one of the main parasites that infect the gastrointestinal tract of humans, affecting hundreds of millions of people worldwide, particularly in developing countries. Antiparasitics administered to treat giardiasis are inefficient in 20% of the cases, usually because of parasite resistance and side effects. In this scenario, microemulsions are a promising pharmaceutical alternative as carriers of molecules with therapeutic action that stimulate the immune system. The study evaluated the effects of a microemulsion delivery system with levamisole hydrochloride on the functional activity of MN phagocytes incubated with G. lamblia. The microemulsion formulated was incorporated with levamisole hydrochloride using distilled water, caprylic/capric triglyceride-Polymol 812®, Sorbitan Oleate-Span 80®, Polysorbate 80 - Tween 80® and 1-butanol. The activity of the microemulsion was analyzed by phagocytosis rate, microbicidal activity, apoptosis rate and intracellular calcium concentration. Phagocytosis rate, microbicidal activity and apoptosis index increased in the microemulsion treatment. The results suggest that the microemulsion improves the therapeutic efficacy of levamisole, increasing the functional activity of phagocytes. The microemulsion with a levamisole delivery system is therefore an efficient alternative for treating giardiasis, acting as an immunomodulator that probably causes fewer side effects than conventional drugs. Copyright © 2017 Elsevier B.V. All rights reserved.

  20. Integral physicochemical properties of reverse micelles of sodium bis(2-ethylhexyl) sulfosuccinate (AOT)

    NASA Astrophysics Data System (ADS)

    Fedyaeva, O. A.; Shubenkova, E. G.; Poshelyuzhnaya, E. G.; Lutaeva, I. A.

    2016-08-01

    The effect the degree of hydration has on optical and electrophysical properties of water/AOT/ n-hexane system is studied. It is found that AOT reverse micelles form aggregates whose dimensions grow along with the degree of hydration and temperature. Aggregation enhances their electrical conductivity and shifts the UV spectrum of AOT reverse emulsions to the red region. Four states of water are found in the structure of AOT reverse micelles.

  1. Correlation of insulin-enhancing properties of vanadium-dipicolinate complexes in model membrane systems: phospholipid langmuir monolayers and AOT reverse micelles.

    PubMed

    Sostarecz, Audra G; Gaidamauskas, Ernestas; Distin, Steve; Bonetti, Sandra J; Levinger, Nancy E; Crans, Debbie C

    2014-04-22

    We explore the interactions of V(III) -, V(IV) -, and V(V) -2,6-pyridinedicarboxylic acid (dipic) complexes with model membrane systems and whether these interactions correlate with the blood-glucose-lowering effects of these compounds on STZ-induced diabetic rats. Two model systems, dipalmitoylphosphatidylcholine (DPPC) Langmuir monolayers and AOT (sodium bis(2-ethylhexyl)sulfosuccinate) reverse micelles present controlled environments for the systematic study of these vanadium complexes interacting with self-assembled lipids. Results from the Langmuir monolayer studies show that vanadium complexes in all three oxidation states interact with the DPPC monolayer; the V(III) -phospholipid interactions result in a slight decrease in DPPC molecular area, whereas V(IV) and V(V) -phospholipid interactions appear to increase the DPPC molecular area, an observation consistent with penetration into the interface of this complex. Investigations also examined the interactions of V(III) - and V(IV) -dipic complexes with polar interfaces in AOT reverse micelles. Electron paramagnetic resonance spectroscopic studies of V(IV) complexes in reverse micelles indicate that the neutral and smaller 1:1 V(IV) -dipic complex penetrates the interface, whereas the larger 1:2 V(IV) complex does not. UV/Vis spectroscopy studies of the anionic V(III) -dipic complex show only minor interactions. These results are in contrast to behavior of the V(V) -dipic complex, [VO2 (dipic)](-) , which penetrates the AOT/isooctane reverse micellar interface. These model membrane studies indicate that V(III) -, V(IV) -, and V(V) -dipic complexes interact with and penetrate the lipid interfaces differently, an effect that agrees with the compounds' efficacy at lowering elevated blood glucose levels in diabetic rats.

  2. Formation of microemulsions for using as cosmeceutical delivery systems: effects of various components and characteristics of some formulations.

    PubMed

    Wuttikul, Krisada; Boonme, Prapaporn

    2016-06-01

    Microemulsions are interesting formulations for cosmeceutical applications due to their good appearance, high solubilization power, thermodynamic stability, and enhancement of skin penetration. In addition, they can spontaneously form when suitable types and amounts of components are simply mixed. In this study, the phase behavior of the nonionic systems with various parameters was studied by construction of phase diagrams using titration method. Natural oils, i.e., coconut oil (CO), rice bran oil (RBO), and palm oil (PO), were analyzed for their fatty acid compositions and then mixed with blends of nonionic surfactants (Tween80: Span80) and water or mixtures of water and a cosolvent, propylene glycol (PG), to find the microemulsion regions. Subsequently, some microemulsions were selected for physical characterization. The largest microemulsion regions which were obtained from CO, RBO, and PO covered the sizes of 11.65, 9.84, and 9.24 %, respectively. The surfactant mixture at weight ratio of 1:1 was the most suitable for CO and PO, but for RBO, it was 2:1. PG could increase the microemulsion regions of PO from 9.24 to 15.33 %, depending on PG concentrations. Hence, the sizes of the microemulsion regions were related to oil types, surfactant mixtures, and ratios between water and PG. The studied microemulsions were water-in-oil (w/o) type, and their internal droplets were in the nanosize range. They exhibited Newtonian flow behavior and their mean viscosity values were from 247.53 to 690.35 cP which were correlated with the types and concentrations of the components in the formulations. In conclusion, natural oils could form w/o microemulsions with nonionic surfactants. The microemulsion formation and characteristics were related to many parameters of the components.

  3. Micelles and reverse micelles in the nickel bis(2-ethylhexyl) sulfosuccinate/water/isooctane microemulsion.

    PubMed

    Garza, Cristina; Carbajal-Tinoco, Mauricio D; Castillo, Rolando

    2004-12-01

    The ternary system Ni(2+)(AOT)(2) (nickel 2-bis[2-ethylhexyl] sulfosuccinate)/water/isooctane presents w/o and o/w microemulsions with a Winsor progression (2Phi-3Phi-2Phi), without the addition of salt; the "fish diagram" was obtained for alpha=0.5 and gamma=0.02-0.22. Using static and dynamic light scattering the micellar size, the ratio of water to surfactant, and the density of micelles for this system were estimated. In addition, the mean interfacial curvature as a function of temperature was obtained.

  4. Formulation and evaluation of microemulsion-based in situ ion-sensitive gelling systems for intranasal administration of curcumin.

    PubMed

    Wang, Shuang; Chen, Ping; Zhang, Lin; Yang, Chunfen; Zhai, Guangxi

    2012-12-01

    The purpose of our study was to develop a microemulsion-based in situ ion-sensitive gelling system for intranasal administration of curcumin. A new microemulsion composition for curcumin was optimized with the simple lattice design. And the microemulsion-based in situ ion-sensitive gelling system consisted of Capryol 90 as oil phase, Solutol HS15 as surfactant, Transcutol HP as cosurfactant and 0.3% DGG solution as water phase. The physicochemical properties such as morphology, droplet size distribution, zeta value and the in vitro release were investigated. In addition, the histological section studies on the reaction between the obtained formulation and nasal mucosa showed that the microemulsion-based in situ ion-sensitive gelling system could not produce obvious damage to nasal mucosa. The pharmacokinetics results showed that the absolute bioavailability of curcumin in the microemulsion-based in situ ion-sensitive gelling system was 55.82% by intranasal administration. And the brain targeting index (BTI) was 6.50, and in the tissue distribution experiment, the value of (AUC(brain)/AUC(blood)) following intranasal administration was higher than that following intravenous administration, suggesting that the obvious brain targeting property by nasal delivery be attributed to a direct nose-to-brain drug transport. It can be concluded that the microemulsion-based in situ gelling as an effective and safe vehicle could greatly enhance the in vivo absorption and facilitate the delivery of curcumin to brain by intranasal administration.

  5. Microemulsion system for topical delivery of thai mango seed kernel extract: development, physicochemical characterisation and ex vivo skin permeation studies.

    PubMed

    Leanpolchareanchai, Jiraporn; Padois, Karine; Falson, Françoise; Bavovada, Rapepol; Pithayanukul, Pimolpan

    2014-10-24

    A microemulsion system containing Thai mango seed kernel extract (MSKE, cultivar "Fahlun") was developed and characterised for the purpose of topical skin delivery. The MSKE-loaded microemulsions were prepared by using the spontaneous emulsification method. Isopropyl myristate (IPM) was selected as the oil phase. A polyoxyethylene sorbitan monooleate and sorbitan monododecanoate (1:1, w/w) system was used as the surfactant phase; an aqueous mixture of different cosurfactants (absolute ethanol, 96.3% v/v ethanol, 1-propanol, 2-propanol or 1,2-propanediol) at a weight ratio of 1:1 was used as the aqueous phase. Among the cosurfactants studied, the 1-propanol aqueous mixture had the largest microemulsion region (48.93%) in the pseudo-ternary phase diagram. Microemulsions containing 1% MSKE demonstrated good physicochemical stability during a six-month study period at 25 ± 2 °C/60% ± 5% RH. The ex vivo skin permeation study demonstrated that the microemulsions exhibited a potent skin enhancement effect allowing MSKE to penetrate skin layers up to 60-fold higher compared with the control. Neither skin irritation nor skin corrosion was observed in ex vivo studies. The present study revealed that IPM-based microemulsion systems may be promising carriers to enhance skin penetration and delivering MSKE for topical treatment.

  6. Enhancement of dissolution rate of mitotane and warfarin prepared by using microemulsion systems.

    PubMed

    Lin, Yu-Hsin; Chen, Yu-Shao; Wu, Tzu-Chin; Chen, Li-Jen

    2011-07-01

    Micronization is the most effective way to enhance the dissolution rate of poorly water-soluble drugs and bioavailability in human body. Microemulsion systems were applied to micronize mitotane and warfarin by cooling method and solvent diffusion process. The triangle phase diagram of the ternary benzyl alcohol+sodium dodecyl sulfate (SDS)+water system was investigated at six different temperatures to determine an appropriate operational microemulsion regime for crystallization. The particle sizes of mitotane and warfarin re-crystallized from microemulsion systems were greatly reduced (to ∼1 μm) compared with that of the commercial ones. Consequently, the dissolution rate coefficients of re-crystallized mitotane and warfarin were significantly improved by, respectively, 7.5 and 13.3 times larger than that of the commercial ones. The crystal structures of re-crystallized mitotane and warfarin were the same as the commercial ones based on the XRD and DSC measurements. In addition, it is interesting to observe the variation of morphology of re-crystallized mitotane as a function of the composition of the SDS and the drug concentrations.

  7. Phase behavior of TXs/toluene/water microemulsion systems for solubilization absorption of toluene.

    PubMed

    Liu, Lian; Tian, Senlin; Ning, Ping

    2010-01-01

    Triton Xs (TXs) surfactants/cosurfactant/water/oil (toluene) microemulsion systems for enhancing toluene solubilization were proposed and its potential was investigated for toluene removal from gas stream. The results indicated that TX-100 was superior to other TXs surfactants in removing toluene without cosurfactant. The efficiency of cosurfactants for improving toluene solubilization capacity follows the order: amine > alcohol > acid. According to the factor analysis, the linear cosurfactants are better than the branched ones. The effects of hydrophile-lipophile balance (HLB), salt (NaCl) concentration and temperature on the formation of microemulsion system were also discussed. The results suggested that the optimum value of HLB was 15, the effect of NaCl concentration on the system was inconspicuous and the lower temperature enhanced the solubilization capacity. Nonionic surfactant-based microemulsions had a significant absorption enhancement for toluene, indicated by as much as 82.72% of toluene in phase composition diagram, which will have a great prospect in air pollution treatment.

  8. Efficacy of Different Block Copolymers in Facilitating Microemulsion Phases in Polymer Blend Systems

    NASA Astrophysics Data System (ADS)

    Pandav, Gunja; Ganesan, Venkat

    2014-03-01

    Polymeric microemulsions are formed in a narrow range of phase diagram when a blend of immiscible homopolymers is compatibilized by copolymers. In this study, we consider the ternary blend system of A and B homopolymers mixed with block copolymers containing A and B segments, and probe the efficacy of different copolymer configurations in promoting the formation of microemulsion phases. Specifically, we consider: (a) Monodisperse diblock copolymers; (b) Diblock copolymers with bidisperse molecular weights (MW); (c) Block copolymers having MW polydispersity in one of the blocks; (d) Diblock copolymers having monodisperse MW but bidispersity in average composition; and (e) Gradient copolymers exhibiting a linear variation in the average composition. Using single chain in mean field simulations effected in two dimensions, we probe the onset of formation and the width of the bicontinuous microemulsion channel in the ternary phase diagram of homopolymer blended with compatibilizer. We rationalize our results by explicitly quantifying the interfacial activity and the influence of fluctuation effects in the respective copolymer systems.

  9. Nanostructured diffusion-limited-aggregation crystal pattern formation in a reactive microemulsion system

    NASA Astrophysics Data System (ADS)

    Srivastava, Rohit; Srivastava, P. K.

    2014-03-01

    Nanostructured diffusion-limited-aggregation (DLA) crystal pattern formation in microemulsion consisting of water, styrene, cetyltrimethylammonium chloride (CTACl), potassium persulphate and an oscillating Belousov-Zhabotinsky (BZ) reactant is reported. A variety of spatiotemporal patterns like concentric wave, spatial (stripe) and chaotic patterns appear. A colloidal phase composed of numerous nano-sized particles has been observed. The solid phase nucleation has been found to occur in the colloidal phase and has been found to grow in a symmetric crystal pattern with the progress of the reaction finally exhibiting DLA structures. We show that the formation of a nanostructured DLA crystal pattern is governed by spatial structures emerging in the BZ microemulsion system. Without any spatial structure in the microemulsion system only hydrogel of high viscosity is formed. A nano-sized branched crystal pattern was formed with a particle diameter in the range of 60-100 nm, as evident by transmission electron microscope, powder x-ray diffraction and particle size analyser studies.

  10. Morphological evolution of copper nanoparticles: Microemulsion reactor system versus batch reactor system

    NASA Astrophysics Data System (ADS)

    Xia, Ming; Tang, Zengmin; Kim, Woo-Sik; Yu, Taekyung; Park, Bum Jun

    2017-07-01

    In the synthesis of nanoparticles, the reaction rate is important to determine the morphology of nanoparticles. We investigated morphology evolution of Cu nanoparticles in this two different reactors, microemulsion reactor and batch reactor. In comparison with the batch reactor system, the enhanced mass and heat transfers in the emulsion system likely led to the relatively short nucleation time and the highly homogeneous environment in the reaction mixture, resulting in suppressing one or two dimensional growth of the nanoparticles. We believe that this work can offer a good model system to quantitatively understand the crystal growth mechanism that depends strongly on the local monomer concentration, the efficiency of heat transfer, and the relative contribution of the counter ions (Br- and Cl-) as capping agents.

  11. Characterization of Microemulsion Systems Formed by a Mixed 1,3-Dioxolane Ethoxylate / Octyl Glucoside Surfactant System

    SciTech Connect

    Alkhatib, Mayson H; Hayes, Douglas G; Urban, Volker S

    2009-01-01

    The phase behavior of microemulsion systems containing water (or 1.0 wt% NaCl{sub aq}), isooctane, and the binary surfactant system consisting of n-octyl-{beta}-D-glucopyranoside, C{sub 8}{beta}G{sub 1}, and the acid-cleavable alkyl ethoxylate, 4-CH{sub 3}O (CH{sub 2}CH{sub 2}O){sub 7.2}, 2-(CH{sub 2}){sub 12}CH{sub 3}, 2-(CH{sub 2})CH{sub 3}, 1,3-dioxolane, or 'cyclic ketal' ('CK-2,13'), was determined. Large temperature-insensitive one, two, and three-phase microemulsion-phase regions were obtained when equal masses of the two surfactants were employed, suggesting that C{sub 8}{beta}G{sub 1} reduces the temperature sensitivity of CK-2,13's ethoxylate group. Addition of C{sub 8}{beta}G{sub 1} to CK-2,13 greatly improves the latter's low efficiency, evidenced by the formation of a three-phase microemulsion system for surfactant concentrations at low fractions of total surfactants for systems with equal mass ratios of water to oil and CK-2,13 to C{sub 8}{beta}G{sub 1}. Analysis of the phase diagrams also suggests that CK-2,13 and C{sub 8}{beta}G{sub 1} impart hydrophobic and hydrophilic character, respectively, to the surfactant mixture, and that addition of salt further increases the hydrophilicity of C{sub 8}{beta}G{sub 1}, presumably because of the salting-in of the latter. Analysis of small-angle neutron scattering data revealed that the mixed surfactant system formed spherical oil-in-water microemulsions, and that increasing the CK-2,13 fraction among the surfactants reduced the critical microemulsion concentration but slightly increased the nanodroplet size.

  12. Microemulsions as colloidal vehicle systems for dermal drug delivery. Part IV: Investigation of microemulsion systems based on a eutectic mixture of lidocaine and prilocaine as the colloidal phase by dynamic light scattering.

    PubMed

    Shukla, Anuj; Krause, Annett; Neubert, Reinhard H H

    2003-06-01

    Stable oil-in-water (o/w) microemulsions used as vehicles for dermal drug delivery have been developed using lidocaine (lignocaine) and prilocaine in oil form (eutectic mixture), a blend of a high (Tween 80, hydrophilic-lipophilic balance (HLB) = 15.0) and a low (Poloxamer 331, HLB = 1.0) HLB surfactant and propylene glycol-water as hydrophilic phase. These microemulsions were able to solubilize up to 20% eutectic mixture of lidocaine and prilocaine without phase separation. The dispersity of the oil phase was investigated by dynamic light scattering. Small colloidal droplets for stable microemulsions of 5~10 nm were observed. At constant surfactant and hydrophilic phase concentration, increasing the total drug concentration in the microemulsion resulted in an increase in the droplet size of the dispersed, colloidal phase. It was observed that a monolayer of surfactant surrounds the oil (eutectic mixture) core. Colloidal droplets of the microemulsion interact via hard sphere with supplementary attractive interaction. This observed interparticle attractive interaction could explain the observed phase behaviour with respect to change in the basicity of the hydrophilic phase as well as the increase in volume fraction of the dispersed, colloidal phase. It was also observed that the stability and size of this dispersed phase depends on the pH of the composition. Because these microemulsions formed stable, isotropic systems in the range of pH 9.5 to 10.4 with alkali buffer or NaOH solution instead of water as hydrophilic phase, so one can produce microemulsions in this pH area.

  13. The Gaussian curvature of the oil-water interface in an isometric bicontinuous microemulsion

    NASA Astrophysics Data System (ADS)

    Chen, Sow-Hsin; Choi, Sung-Min

    1997-02-01

    Small-angle neutron scattering (SANS) measurements are made on a three-component isometric (equal volume fractions of water and oil) microemulsion system, composed of AOT/water (0.4% NaCl)/D-octane, in the one-phase channel near the three-phase region at and around the hydrophile-lipophile balance temperature. A previous SANS contrast variation experiment indicated that the microstructure of this type of isometric microemulsion is bicontinuous in water and oil with the surfactant film at the interface having a zero mean curvature. We analyze SANS data taken with an oil-water contrast in terms of a modified Berk's random wave model. We choose a spectral function which is an inverse sixth-order polynomial, with three parameters a, b and c, as introduced by Lee and Chen earlier. This three-parameter spectral function is then used in conjunction with Cahn's clipping scheme to obtain the Debye correlation function appropriate for the microemulsion system. The model analysis results in good agreement with the intensity data in an absolute scale. We then use the three parameters so obtained to calculate the average Gaussian curvature of the interface. We discuss the variation of the average Gaussian curvature as a function of the surfactant volume fraction and its implication on the degree of local order of the bicontinuous structure. We also show a 3-D reconstructed morphology of the most disordered microemulsion.

  14. Formation of middle-phase microemulsions in multicomponent systems containing petrostep-465 and ethoxylated tall oils

    SciTech Connect

    Magid, L.J.

    1982-06-01

    The range of salinities over which certain Petrostep-465/ethoxylated tall oil/cosurfactant/hydrocarbon/brine systems form middle-phase microemulsions was determined. The presence of the nonionic surfactant, in cases where n-decane is the hydrocarbon and 2-butanol is the cosurfactant, increases the optimal salinity of the system. Some broadening of the salinity range over which low interfacial tensions are observed is also found. Phase behavior for systems containing P-465 as the only surfactant shows order of mixing effects.

  15. Solubilization of a dendrimer into a microemulsion.

    PubMed

    Nir, Ido; Aserin, Abraham; Libster, Dima; Garti, Nissim

    2010-12-23

    The present work investigates, for the first time, a system comprising a dendrimer incorporated into the water core of water-in-oil (W/O) microemulsion (ME). A second generation (G-2) poly(propyleneimine) dendrimer (PPI) was solubilized into W/O ME composed of AOT (sodium bis(2-ethylhexyl)sulfosuccinate), heptane, and water. Such a model system possessing the benefits of both dendrimers and ME, can potentially offer superior control of drug administration. The localization of PPI within the system, its specific interactions with the components of the carrier, and its effect on the ME structure was explored by SAXS, DSC, ATR-FTIR, and electrical conductivity measurements. Considerable water binding by PPI, accompanied by partial dehydration of AOT polar heads, was detected by ATR-FTIR and DSC analysis, suggesting that PPI acted as a "water pump". In addition, SAXS measurements showed periodicity increase and disordering of the droplets. Hence, localization of PPI within the core and interfacial regions of the droplets was assumed. Direct electrostatic interactions between PPI and the sulfonate group were not noticed, since the dendrimer molecules were mostly not protonated in the current basic environment at pH 12. However, slight hydrogen bonding between PPI and the S=O groups allowed the dendrimer to behave as a "spacer" between sodium and sulfonate ions. This affected the electrical conductivity behavior of the system, revealing that PPI favored the percolation process. Most likely, PPI decreased the rigidity of the interfacial layer, facilitating the diffusion of sodium ions through the channels. The characterized model system can be advantageously utilized to design specific delivery vehicles, allowing administration of dendrimers as a therapeutic agent from host MEs.

  16. Fluorescent behavior of B-phycoerythrin in microemulsions of aerosol OT/water/isooctane.

    PubMed

    Bermejo, Ruperto; Tobaruela, Diego J; Talavera, Eva M; Orte, Angel; Alvarez-Pez, Jose M

    2003-07-15

    Taking advantage of its unusual fluorescent properties, the incorporation of B-phycoerythrin (B-PE) in aerosol OT (AOT, sodium bis-(2-ethylhexyl) sulphosuccinate)/water/isooctane microemulsions was investigated by following their steady-state and time-resolved fluorescence as a function of the water-to-surfactant molar ratio, w(0). The fluorescent intensity at 575 nm increased continuously with increasing water content, saturating at a w(0) around 35 and staying practically constant at w(0)> or =40. The steady-state anisotropy showed an initial increase with increasing water content until w(0)=23 and then decreased strongly, staying practically constant when w(0)> or =40. The values of the fluorescent parameters, anisotropy and fluorescent intensity, were unchanged when the water content of the system increased in the range between w(0)=40 to 50. This implies the effective incorporation of B-PE in the microemulsion droplets with w(0)> or =40, as well as the equilibrium of the dispersion at these water/surfactant ratios, since higher water content does not affect the main surrounding microenvironment of the protein. The overall incorporation in the microemulsion droplets caused minor spectroscopic changes with respect to biliprotein in aqueous solution of 20 mM sodium phosphate buffer, pH 7.0, such as a blue absorption shift of 3 nm and an emission shift of 1.5 nm, as well as a slight increase in excitation anisotropy spectrum mainly caused by a decrease in protein mobility. Therefore, there are no important interactions between the chromophores and the AOT sulfonate head groups. Emission intensity decays followed complex kinetics in both aqueous and dispersion media. The stability with time and temperature of the biliprotein in the microemulsion was higher than in the aqueous solution. All the results can be explained in terms of B-PE inclusion in the water droplets of AOT microemulsions where the protein has similar configuration and conformation to that in

  17. Chloride ion effects on synthesis and directed assembly of copper nanoparticles in liquid and compressed alkane microemulsions.

    PubMed

    Kitchens, Christopher L; McLeod, M Chandler; Roberts, Christopher B

    2005-05-24

    Microemulsions are effective media for solution-based synthesis of metallic nanoparticles where surfactants and other ionic species influence the directed assembly of the nanomaterials with specific sizes, geometries, and compositions. This study demonstrates the effects of chloride ion on the synthesis of copper nanoparticles within the sodium bis(2-ethylhexyl)sulfosuccinate (AOT) reverse micelle system utilizing both liquid isooctane and compressed propane as the bulk solvent. Copper nanoparticle synthesis can be achieved in the presence of HCl in the micelle core, taking advantage of the buffering action of the AOT surfactant. The concentration of chloride ions influence the particle growth rate and dispersion in liquid isooctane. The presence of chloride ions during particle synthesis in compressed propane has a significant effect on the geometry and structure of the copper nanomaterials produced. Chloride ion addition to the compressed propane/Cu(AOT)(2)-AOT/water reverse micelle system at 20 degrees C and 310 bar results in the formation of diamond-shaped copper nanoparticle assemblies. The copper nanoparticle assemblies exhibit unique structure and retain this structure through repeated solvent processing steps, allowing separation and recovery of the assembled diamond-shaped copper nanoparticle structures.

  18. Microemulsion-based synergistic dual-drug codelivery system for enhanced apoptosis of tumor cells

    PubMed Central

    Qu, Ding; Ma, Yihua; Sun, Wenjie; Chen, Yan; Zhou, Jing; Liu, Congyan; Huang, Mengmeng

    2015-01-01

    A microemulsion-based synergistic dual-drug codelivery system was developed for enhanced cell apoptosis by transporting coix seed oil and etoposide into A549 (human lung carcinoma) cells simultaneously. Results obtained by dynamic light scattering showed that an etoposide (VP16)-loaded coix seed oil microemulsion (EC-ME) delivery system had a small size around 35 nm, a narrow polydispersity index, and a slightly negative surface charge. The encapsulating efficiency and total drug loading rate were 97.01% and 45.48%, respectively, by high-performance liquid chromatography. The release profiles at various pH values showed an obvious pH-responsive difference, with the accumulated amount of VP16 released at pH 4.5 (and pH 5.5) being 2.7-fold higher relative to that at pH 7.4. Morphologic alteration (particle swelling) associated with a mildly acidic pH environment was found on transmission electron microscopy. In the cell study, the EC-ME system showed a significantly greater antiproliferative effect toward A549 cells in comparison with free VP16 and the mixture of VP16 and coix seed oil. The half-maximal inhibitory concentration of the EC-ME system was 3.9-fold and 10.4-fold lower relative to that of free VP16 and a mixture of VP16 and coix seed oil, respectively. Moreover, fluorescein isothiocyanate and VP16 (the green fluorescent probe and entrapped drug, respectively) were efficiently internalized into the cells by means of coix seed oil microemulsion through intuitive observation and quantitative measurement. Importantly, an EC-ME system containing 20 μg/mL of VP16 showed a 3.3-fold and 3.5-fold improvement in induction of cell apoptosis compared with the VP-16-loaded microemulsion and free VP16, respectively. The EC-ME combination strategy holds promise as an efficient drug delivery system for induction of apoptosis and treatment of lung cancer. PMID:25709440

  19. Optical Properties of Silica-Encapsulated ZnSe Nanocrystals Prepared with Water-in-Oil Microemulsions

    NASA Astrophysics Data System (ADS)

    Liu, Kang; Kim, Ji Hyeon; Park, Sang Joon

    2013-01-01

    Silica-encapsulated ZnSe nanocrystals (NCs) were prepared by a safe and simple synthesis method, utilizing a sodium bis (2-ethylhexyl) sulfosuccinate (AOT)/water/cyclohexane microemulsion system and characterized by UV-vis analysis, photoluminescence (PL) spectroscopy, and transmission electron microscopy (TEM). For the encapsulations, two reverse micellar solutions [one for tetraethyl orthosilicate (TEOS) and the other for ZnSe] containing different water volumes were employed. The size of silica particles containing ZnSe NCs could be controlled from 13-37 nm by varying the water content W (W=[H2O]/[AOT]). On the other hand, the size of encapsulated ZnSe NCs was almost unchanged (about 2.5 nm) even though the size of the silica particles was increased. At W = 7, the maximum PL efficiency of 6% was obtained and the photostability was increased markedly after ZnSe NCs were encapsulated by silica.

  20. Quaternary cross-diffusion in water-in-oil microemulsions loaded with a component of the Belousov-Zhabotinsky reaction.

    PubMed

    Rossi, Federico; Vanag, Vladimir K; Tiezzi, Enzo; Epstein, Irving R

    2010-06-24

    We obtain the diffusion matrix, D, consisting of the main and cross-diffusion coefficients for a loaded AOT microemulsion, a quaternary system containing water (1)/AOT (2)/species (3)/octane (4). Here "species" is a component of the Belousov-Zhabotinsky reaction: NaBr, NaBrO(3), bathoferroin, ferroin, or Br(2). The main and cross-diffusion coefficients of each species depend crucially on its solubility. For water-soluble species (the salts), D(13) and D(23) are large (much larger than the main diffusion coefficients) and positive. For species located mainly in the surfactant shell (bathoferroin or ferroin), D(13) and D(23) are large and negative. For oil-soluble Br(2), D(13) and D(23) are larger and more negative, whereas D(33) > D(11), D(22). The coefficients D(31) and D(32) are small for all species studied.

  1. Microemulsion systems containing bioactive natural oils: an overview on the state of the art.

    PubMed

    Xavier-Junior, F H; Vauthier, C; Morais, A R V; Alencar, E N; Egito, E S T

    2017-05-01

    Natural oils are extremely complex mixtures containing compounds of different chemical nature. Some of them have physiological or therapeutic activities that may act either alone or in synergy. Therefore, they are used in the pharmaceutical, agronomic, food, sanitary and cosmetic industries. Today, the interest in bioactive natural oils is growing due to their immense potential to prevent and treat numerous human diseases. Formulation in microemulsions (MEs) containing natural oils appeared suitable to improve pharmaceutical and biopharmaceutical properties of bioactive compound derivatives from these oils. Microemulsion systems are thermodynamically stable, transparent, and are isotropic dispersions consisting of oil and water stabilized by an interfacial film of surfactants, typically in combination with a cosurfactant. They can protect labile compounds from premature degradation, control release, increase solubility and hence enhance the bioavailability of poorly bioavailable compounds. The aim of this work was to review the various advantages of bioactive compounds presented in natural oil loaded ME systems to be used as delivery systems. First, the state of the art of the parameters involved in the ME formation, including the basic concepts of the physicochemical formulation of the ME systems, and the main aspects of production and the energy responsible for their formation were reported. The second section describes the use of ME systems and reviews the recent applications of natural oil-loaded in the ME systems as the bioactive compound in the formulation.

  2. Characterization of microemulsion liquid chromatography systems by solvation parameter model and comparison with other physicochemical and biological processes.

    PubMed

    Liu, Jianfang; Sun, Jin; Wang, Yongjun; Liu, Xiaohong; Sun, Yinghua; Xu, Huan; He, Zhonggui

    2007-09-14

    The solvation parameter model has been applied to characterize four microemulsion liquid chromatography (MELC) systems and two micellar liquid chromatography (MLC) systems, and utilized to compare the above systems with other physicochemical and biological processes in this study. The microemulsion mobile phases were composed of sodium dodecyl sulfate (SDS), polyoxyethylene (23) lauryl ether (Brij 35), butanol, heptane and phosphate buffer (pH 7.0) at the designated ratios. The results showed the main difference between the concerned MELC and MLC systems was the decrease of hydrogen-bond basicity of stationary phase with the addition of heptane in microemulsion. Principal component analysis with normalized coefficients can provide consistent results involving the similarities among various systems with that obtained by distance parameter d. Except for some proven similarities of chromatographic systems to octanol-water partition coefficients (logP) and human skin permeation (logK(p)), a microemulsion HPLC system, the mobile phase being 3.3% SDS-6.6% butanol-1.6% heptane-88.5% buffer, was found very similar to drug penetration across blood-brain barrier and its predictive capability for this biological process was originally evaluated in this study.

  3. Conductivity in nonpolar media: experimental and numerical studies on sodium AOT-hexadecane, lecithin-hexadecane and aluminum(III)-3,5-diisopropyl salicylate-hexadecane systems.

    PubMed

    Schmidt, Jochen; Prignitz, Rodolphe; Peschka, Dirk; Münch, Andreas; Wagner, Barbara; Bänsch, Eberhard; Peukert, Wolfgang

    2012-11-15

    The conductivity behavior of doped hydrocarbon systems is studied by applying impedance spectroscopy. In the case of 3,5-diisopropyl salicylato aluminum (III) the charge carriers are formed by dissociation of the compound and their concentration is proportional to the square root of the solute concentration. In hydrocarbon systems that consist of micelle forming compounds (sodium AOT/ lecithin) a linear dependence of charge carrier concentration on solute concentration is observed in the concentration regime where micelles are present. The conduction mechanisms are studied by numerical solution of a Poisson-Nernst-Planck system that describes the charge transport. We follow two different approaches to extract the degree of micelle dissociation from the impedance data. Firstly, by computing the response of a linear approximation of the Poisson-Nernst-Planck model, and secondly by computing the fully nonlinear response from direct numerical simulations using finite elements. For high and moderate frequencies both approaches agree very well with the experimental data. For small frequencies the response becomes nonlinear and the concept of impedance fails. Furthermore, the numerically computed values for the degree of dissociation are of the same order of magnitude as the values obtained with classical formulas, but still differ by a factor of about 1/3. The direct numerical simulation allows new insight into the conduction mechanisms for different frequency regimes. Copyright © 2012 Elsevier Inc. All rights reserved.

  4. Improvement of effect of water-in-oil microemulsion as an oral delivery system for fexofenadine: in vitro and in vivo studies

    PubMed Central

    Gundogdu, E; Alvarez, I Gonzalez; Karasulu, E

    2011-01-01

    Fexofenadine (FEX) has high solubility and low permeability (BCS, Class III). In this work, novel FEX loaded water in oil microemulsion (w/o) was designed to improve bioavailability and compared with Fexofen® syrup in in vitro and in vivo studies. In addition, pharmacokinetic parameters in permeability studies were estimated by using WinNonLin software program. w/o microemulsion system was optimized using a pseudoternary phase diagram, composed of span 80/lutrol F 68 (9.5:0.5 w/w), oleic acide, isopropyl alcohol and water as surfactant mixture; oil and cosurfactant was developed for oral drug delivery. w/o microemulsion systems were characterized by phase behavior, particle size, viscosity and solubilization capacity. In vitro studies were studied using Caco-2 cell monolayer. Pharmacokinetic parameters of w/o microemulsion were investigated in rabbits and compared to Fexofen® syrup. Fexofen® syrup and microemulsion were administered by oral gavage at 6 mg/kg of the same concentration. The experimental results indicated that microemulsion (HLB = 5.53) formed nanometer sized droplets (33.29 ± 1.76) and had good physical stability. This microemulsion increased the oral bioavailability of FEX which was highly water-soluble but fairly impermeable. The relative bioavailability of FEX microemulsion was about 376.76% compared with commercial syrup in rabbits. In vitro experiments were further employed for the enhanced effect of the microemulsion for FEX. These results suggest that novel w/o microemulsion plays an important role in enhancing oral bioavailability of low permeability drugs. PMID:21904453

  5. Preparation of iron oxide nanoparticles from FeCl3 solid powder using microemulsions

    NASA Astrophysics Data System (ADS)

    Nassar, Nashaat; Husein, Maen

    2006-05-01

    Nanoparticles of iron oxide were prepared by subjecting iron chloride powder to (w/o) microemulsions consisting of sodium bis(2-ethylhexyl) sulfosuccinate (AOT), isooctane and water. FeCl3 was first dissolved in the water pools of the microemulsion, and then reacted with NaOH added as an aqueous solution to form iron oxide. The amount of NaOH solution was limited so that single microemulsion phase is obtained. This technique serves as an in-situ nanoparticle preparation technique aimed at minimizing particle aggregation associated with particle transportation to required sites. In this study, the effects of AOT concentration and water to AOT mole ratio on the nanoparticle size were investigated. UV/Vis spectrophotometry and transmission electron microscopy (TEM) were used to measure the particle size distribution.

  6. alpha-lactalbumin-AOT charge interactions tune phase structures in isooctane/brine mixtures.

    PubMed

    Kim, Jun Y; Dungan, Stephanie R

    2009-07-21

    Self-assembly of the anionic surfactant AOT with the protein alpha-lactalbumin in isooctane/brine mixtures results in phase structures whose type, size, and shape differ considerably from those formed by the surfactant alone. Small-angle X-ray scattering was used to determine the size and shape of these structures for 5.4 < pH < 11.2 and 0.25, 0.33, and 0.4 wt % NaCl. All pH values were above the reported isoelectric point for the protein. The composition of the system (except for salt) was fixed, with 2.5 wt % surfactant in equivolume mixtures of oil and water and either 0 or 0.4 wt % protein. Under these conditions, AOT in the absence of protein always formed spherical, water-in-oil (w/o) microemulsion droplets in the organic phase with no self-assembly in the aqueous phase. In the presence of alpha-lactalbumin, self-assembled structures were formed in both aqueous and organic phases, and the size and shape of these was tuned by both pH and [NaCl]. Protein-surfactant interaction was weakest at the most alkaline pH, with protein-free, spherical droplets forming in the organic phase and surfactant-decorated soluble protein clusters forming in the aqueous phase. As pH was decreased, protein increasingly partitioned to the organic phase and droplets became ellipsoidal and much larger in volume, with these effects enhanced at lower salt concentration. Aqueous structures were also strongly affected by pH, shifting from prolate protein/surfactant aggregates at alkaline pH to oil-in-water, oblate microemulsion droplets at neutral pH. At acidic pH and higher salt concentration, self-assembly shifted toward a third, anisotropic aqueous phase, which contained discoid bilayer structures. It is proposed that hydrophobic attraction causes association of the protein with the surfactant monolayer, and pH and [salt] tune the system via the protein by modifying electrostatic repulsion and monolayer curvature.

  7. Fluorescence resonance energy transfer in microemulsions composed of tripled-chain surface active ionic liquids, RTILs, and biological solvent: an excitation wavelength dependence study.

    PubMed

    Banerjee, Chiranjib; Kundu, Niloy; Ghosh, Surajit; Mandal, Sarthak; Kuchlyan, Jagannath; Sarkar, Nilmoni

    2013-08-15

    In this article we have reported the fluorescence resonance energy transfer (FRET) study in our earlier characterized surface active ionic liquids (SAILs)-containing microemulsion, i.e., N-methyl-N-propylpyrrolidinium bis(trifluoromethanesulfonyl)imide ([P13][Tf2N])/[CTA][AOT]/isopropyl myristate ([IPM]) and N,N,N-trimethyl-N-propylammonium bis(trifluoromethanesulfonyl)imide ([N3111][Tf2N])/[CTA][AOT]/[IPM] microemulsions (Banerjee, C.; Mandal, S.; Ghosh, S.; Kuchlyan, J.; Kundu, N.; Sarkar, N. J. Phys. Chem. B 2013, 117, 3927-3934). The occurrence of effective FRET from the donor, coumarin-153 (C-153) to the acceptor rhodamine 6G (R6G) is evident from the decrease in the steady state fluorescence intensity of the donor with addition of acceptor and subsequent increase in the fluorescence intensity of the acceptor in the presence of donor. The excitation wavelength dependent FRET from C-153 to R6G has also been performed to assess the dynamic heterogeneity of these confined systems. In time-resolved experiments, the significant rise time of the acceptor in the presence of the donor further confirms the occurrence of FRET. The multiple donor-acceptor (D-A) distances, for various microemulsions, obtained from the rise times of the acceptor emission in the presence of a donor can be rationalized from the varying distribution of the donor, C-153, in the different regions of the microemulsion. Time-resolved measurement reveals that with increasing excitation wavelength from 408 to 440 nm, the contribution of the faster rise component of FRET increases significantly due to the close proximity of the C-153 and R6G in the polar region of the microemulsion where occurrence of FRET is very high. Moreover, we have also studied the FRET with variation of R (R = [room temperature ionic liquids (RTILs)]/[surfactant]) and shown that the effect of excitation wavelength on FRET is similar irrespective of R values.

  8. Microemulsions in technical processes

    SciTech Connect

    Schwuger, M.J.; Stickdorn, K.; Schomaecker, R.

    1995-06-01

    The aim of this review is to present once again the basic properties of microemulsions and to relate them to some already established applications and also to show further potential fields of application. This review will survey this area, focusing mainly on the last decade. Earlier publications on the technical relevance of microemulsions and reverse micelles were reviewed by Langevin in 1982. The most important properties of these systems, which are of significance for technical applications, will be described. The applications discussed are: enhanced oil recovery; liquid-liquid extraction; extraction from chemically contaminated soils; lubricants and cutting oils; pharmaceuticals and cosmetics; washing; impregnation and textile finishing; and chemical reactions in microemulsions. 143 refs.

  9. Evaluation of steady-state kinetic parameters for enzymes solubilized in water-in-oil microemulsion systems.

    PubMed Central

    Oldfield, C

    1990-01-01

    1. Equations are derived for the steady-state kinetics of substrate conversion by enzymes confined within the water-droplets of water-in-oil microemulsion systems. 2. Water-soluble substrates initially confined within droplets that do not contain enzyme are assumed to be converted into product only after they enter enzyme-containing droplets via the inter-droplet exchange process. 3. Hyperbolic (Michaelis-Menten) kinetics are predicted when the substrate concentration is varied in microemulsions of fixed composition. Both kcat. and Km are predicted to be dependent on the size and concentration of the water-droplets in the microemulsion. 4. The predicted behaviour is shown to be supported by published experimental data. A physical interpretation of the form of the rate equation is presented. 5. The rate equation for an oil-soluble substrate was derived assuming a pseudo-two-phase (oil & water) model for the microemulsion. Both kcat. and Km are shown to be independent of phi aq. Km is larger than the aqueous solution value by a factor approximately equal to the oil/water partition coefficient of the substrate. The validity of the rate equation is confirmed by published data. PMID:2264819

  10. Gallium extraction by microemulsions.

    PubMed

    de Castro Dantas, T N; de Lucena Neto, M H; Dantas Neto, A A

    2002-04-08

    In this work, the use of microemulsion in the extraction of gallium, with Bayer process, has been studied. The studied microemulsion systems were: systems I and II, with saponified coconut oil (SCO) and 4-ethyl,1-methyl,7-octyl,8-hydroxyquinoleine (Kelex-100) as extractants. The extraction essays by microemulsion were carried out by applying an experimental planning method whose microemulsion points were prepared within an experimental domain favorable to the extraction. Gallium and aluminum extraction percentages, in each point, were evaluated via a statistical treatment of the data, with the use of variance analysis and mathematical models. In system I (SCO), percentages of extraction of 85.5% for gallium and 35.4% for aluminum were achieved; in system II (Kelex-100), the yields were 100% for gallium and 99.9% for aluminum. The reextraction study with sulfuric acid presented the same behavior for both systems, with efficiency depending upon the concentration of the acid, and allowing for a selective reextraction of gallium and aluminum.

  11. Temperature and Pressure Effects on the Bending Modulus of Monolayers in a Ternary Microemulsion

    NASA Astrophysics Data System (ADS)

    Kawabata, Y.; Nagao, M.; Seto, H.; Komura, S.; Takeda, T.; Schwahn, D.; Yamada, N. L.; Nobutou, H.

    2004-02-01

    We performed small-angle neutron scattering and neutron spin echo experiments on a ternary microemulsion composed of ionic surfactant AOT, water, and decane. Thermal fluctuations of monolayers have been investigated as a function of temperature and pressure. The amphiphilic monolayers become more flexible with increasing temperature and more rigid with increasing pressure. These results are consistent with the microscopic picture that the head-head repulsion of the AOT molecules is enhanced at high temperature while an attractive interaction between the hydrophobic tails of the AOT molecules increases at high pressure.

  12. Design and control of patterns in reaction-diffusion systems

    SciTech Connect

    Vanag, Vladimir K.; Epstein, Irving R.

    2008-06-15

    We discuss the design of reaction-diffusion systems that display a variety of spatiotemporal patterns. We also consider how these patterns may be controlled by external perturbation, typically using photochemistry or temperature. Systems treated include the Belousov-Zhabotinsky (BZ) reaction, the chlorite-iodide-malonic acid and chlorine dioxide-malonic acid-iodine reactions, and the BZ-AOT system, i.e., the BZ reaction in a water-in-oil reverse microemulsion stabilized by the surfactant sodium bis(2-ethylhexyl) sulfosuccinate (AOT)

  13. Dielectric depolarisation and concerted collective dynamics in AOT reverse micelles with and without ubiquitin.

    PubMed

    Schmollngruber, Michael; Braun, Daniel; Oser, Daniel; Steinhauser, Othmar

    2016-02-07

    In this computational study we present molecular dynamics (MD) simulations of reverse micelles, i.e. nano-scale water pools encapsulated by sodium bis(2-ethylhexyl) sulfosuccinate (AOT) and dissolved in isooctane. Although consisting of highly polar components, such micro-emulsions exhibit surprisingly low dielectric permittivity, both static and frequency-dependent. This finding is well supported by experimental dielectric measurements. Furthermore, the computational dielectric spectra of reverse micelles with and without the polar protein ubiquitin are almost identical. A detailed component analysis of our simulated systems reveals the underlying mechanism of the observed dielectric depolarisation. While each component by itself would make a remarkable contribution to the static dielectric permittivity, mutual compensation leads to the observed marginal net result. This compensatory behavior is maintained for all but the highest frequencies. Dielectric model theory adapted to the peculiarities of reverse micelles provides an explanation: embedding a system in a cavity engulfed by a low dielectric medium automatically leads to depolarization. In this sense experiment, simulation and theory are in accordance.

  14. Curcumin Protects Skin against UVB-Induced Cytotoxicity via the Keap1-Nrf2 Pathway: The Use of a Microemulsion Delivery System

    PubMed Central

    Ben Yehuda Greenwald, Maya; Frušić-Zlotkin, Marina; Soroka, Yoram; Ben Sasson, Shmuel; Bitton, Ronit; Bianco-Peled, Havazelet

    2017-01-01

    Curcumin was found to be beneficial in treating several skin pathologies and diseases, providing antioxidant protection due to its reducing properties and its electrophilic properties (the ability to activate the Nrf2 pathway and induce phase II cytoprotective enzymes). Nevertheless, clinical applications of curcumin are being hampered by its insufficient solubility, chemical instability, and poor absorption, leading to low efficacy in preventing skin pathologies. These limitations can be overcome by using a nanotechnology-based delivery system. Here, we elucidated the possibility of using curcumin encapsulated in a microemulsion preserving its unique chemical structure. We also examined whether curcumin microemulsion would reduce UVB-induced toxicity in skin. A significant curcumin concentration was found in the human skin dermis following topical application of a curcumin microemulsion. Moreover, curcumin microemulsion enhanced the reduction of UV-induced cytotoxicity in epidermal cells, paving the way for other incorporated electrophiles in encapsulated form protecting skin against stress-related diseases. PMID:28757910

  15. USPIO assisting degradation of MXC by host/guest-type immobilized laccase in AOT reverse micelle system.

    PubMed

    Yang, Yu-Xiang; Pi, Na; Zhang, Jian-Bo; Huang, Yan; Yao, Ping-Ping; Xi, Yan-Jie; Yuan, Hong-Ming

    2016-07-01

    The laccase and ultrasmall superparamagnetic iron oxide nanoparticles (USPIO) have been assembled inside the tubular mesoporous silica via co-adsorption technology to prepare host/guest-type immobilized laccase, which is applied to degrade methoxychlor (MXC) in aqueous and reverse micelle environments. The effects of various parameters on degradation of MXC were studied. Under the optimum conditions, the degradation rate could reach maximum value of 45.6 % and remain at 20.8 % after seven cycles. Moreover, the addition of small molecular compound 2, 2'-azinobis-(3-ethylbenzthiazoline-6-sulphonate) to the system could greatly improve the degradation efficiency. The MXC degradation process is a first-order reaction, and the activation energy of MXC degradation catalyzed by immobilized laccase (41.46 kJ mol(-1)) is relatively lower than that catalyzed by free laccase (44.91 kJ mol(-1)). Based on the degradation products measured by gas chromatograph-mass spectrometer (GC-MS) and nuclear magnetic resonance (NMR), the degradation mechanism of MXC has also been proposed.

  16. Effect of Mannosylerythritol lipid-A on light scattering of AOT/D2O/Octane

    NASA Astrophysics Data System (ADS)

    Sharifi, Soheil

    2016-09-01

    The light scattering technique is used for the study of interaction of Mannosylerythritol lipid-A on AOT/D2O/Octane. The collective diffusion of AOT/D2O droplets soluble in Octane mixed with lipid is founded from a correlation function of light scattering. We focus on the variation of the dynamic behavior of droplets as a function of the lipid concentrations and the size of droplets. The increase of concentration of Mannosylerythritol lipid-A on microemulsion decreases the dynamic of droplets. The SAXS experiment shows the size and the interaction of the droplets change by increase of Mannosylerythritol lipid-A concentration. A hard sphere model can describe the interaction of lipid with AOT/D2O droplets.

  17. Influence of microemulsion-mucin interaction on the fate of microemulsions diffusing through pig gastric mucin solutions.

    PubMed

    Zhang, Jianbin; Lv, Yan; Wang, Bing; Zhao, Shan; Tan, Mingqian; Lv, Guojun; Ma, Xiaojun

    2015-03-02

    Mucus layer, a selective diffusion barrier, has an important effect on the fate of drug delivery systems in the gastrointestinal tract. To study the fate of microemulsions in the mucus layer, four microemulsion formulations with different particle sizes and lipid compositions were prepared. The microemulsion-mucin interaction was demonstrated by the fluorescence resonance energy transfer (FRET) method. Moreover, the microemulsions were observed aggregated into micron-sized emulsions by laser confocal microscopy. We concluded the microemulsion-mucin interaction not only led to microemulsions closely adhered to mucins but also destroyed the structure of microemulsions. At last, the diffusion of blank microemulsions and microemulsion-carried drugs (resveratrol and hymecromone) through mucin solutions was determined by the fluorescence recovery after photobleaching (FRAP) method and the Franz diffusion cell method. The results demonstrated the diffusion of microemulsions was significantly hindered by mucin solutions. The particle size of microemulsions had a negligible effect on the diffusion coefficients. However, the type of lipid played an important role, which could form hydrophobic interactions with mucins. Interestingly, microemulsion-carried drugs with different core/shell locations seemed to suffer different fates in the mucin solutions. The drug incorporated in the oil core of microemulsions, resveratrol, was transported through the mucus layer by the carriers, while the drug incorporated in the surfactant shell of microemulsions, hymecromone, was separated from the carriers and diffused toward the epithelium in the form of free molecules.

  18. Preferential solubilization behaviours and stability of some phenolic-bearing essential oils formulated in different microemulsion systems.

    PubMed

    Edris, A E; Malone, C F R

    2012-10-01

    The solubilization behaviour of a number of essential oils (EOs) containing volatile phenolic constituents was investigated in five different micellar solutions. These oils include clove bud (Eugenia caryophyllata), thyme (Thymus serpyllum) and oregano (Thymus capitatus). Ternary and pseudo-ternary phase diagrams were constructed to assess the ability for microemulsion formation and dilutability of each system using non-ionic surfactants. Results showed that Tween 20 (T20) was more suitable to solubilize these oils compared with Tween 80 (T80). Clove EO was found to be easily microemulsifiable compared with the other EOs, whereas oregano showed the least tendency to form a microemulsion. Particle sizes measured at different dilution lines ranged between 5.9 and 16.9 nm. The chemical composition of each EO was revealed by gas chromatography and was correlated with the observed solubilization behaviour. The presence of solubilization enhancers like poly-ols and short-chain alcohols improved solubilization of all EOs; however, establishment of new dilution lines was controlled by EO type. Physical stability assessment showed that all microemulsions were stable against alternate freeze/thaw cycles which extended for 1 week. On the contrary, each system showed different temperature sensitivity in the thermal stress assessment. The results of this investigation can be useful in fabrication of thermodynamically stable aqueous system carrying aromatic and bioactive phenolics for different applications in personal hygiene, cosmetic, fragrance and pharmaceutical products.

  19. Microemulsions as drug delivery systems to improve the solubility and the bioavailability of poorly water-soluble drugs.

    PubMed

    He, Cai-Xia; He, Zhong-Gui; Gao, Jian-Qing

    2010-04-01

    Microemulsions have been studied extensively as potential drug delivery vehicles for poorly water-soluble drugs. An understanding of the physicochemical and biopharmaceutical characteristics of the microemulsions according to administration routes will provide guidance for designing the formulations of microemulsions. In this paper, the use and the characteristics of microemulsions as drug delivery vehicles are reviewed. As the formulations of the microemulsion always include a great amount of surfactant and co-surfactant, which may cause hemolysis or histopathological alterations of the tissue, the potential toxicity or the irritancy of microemulsions is also discussed in this paper. Developments of microemulsions for poorly water-soluble drugs in recent years are included in this review. Several factors limiting the commercial or clinical use of microemulsions are also discussed. Considering the potential in enhanced drug uptake/permeation and facing the limitations, their unique properties make microemulsions a promising vehicle for poorly water-soluble drugs.

  20. Fourier transform infrared study on microemulsion system of potassium salt of bis(2-ethylhexyl) phosphinic acid (HA)

    NASA Astrophysics Data System (ADS)

    Zhou, Weijin; Shi, Nai; Wang, Yi; Chang, Zhiyuan; Wu, JinGuang

    1994-01-01

    To study microemulsion formation in a solvent extraction system is to probe into some basic principles of extraction chemistry in the light of combining extraction chemistry with surface chemistry. In our previous investigations, the microemulsions of the salts of HDEHP and PC88A have been studied systematically by FT-IR. In the experiment, we observed the change of peak positions and intensities of P equals O, P-O-C and P-O-H groups during saponification and hydration, and discovered that the peak of P-O-C splits apart into 1045 and 1075 cm-1. The vibration frequency of the P-O-C group in HDEHP and PC88A is quite close to the symmetric stretching frequency of the POO- group, and thus causes difficulties in the study of their peak position and absorbance variation. For this reason we synthesized bis(2-ethylhexyl) phosphinic acid without the P-O-C group. Infrared spectra in the range of 800 - 4000 cm-1 of this microemulsion system was studied.

  1. Temperature-sensitive microemulsion gel: an effective topical delivery system for simultaneous delivery of vitamins C and E.

    PubMed

    Rozman, Branka; Zvonar, Alenka; Falson, Francoise; Gasperlin, Mirjana

    2009-01-01

    Microemulsions (ME)--nanostructured systems composed of water, oil, and surfactants--have frequently been used in attempts to increase cutaneous drug delivery. The primary objective addressed in this work has been the development of temperature-sensitive microemulsion gel (called gel-like ME), as an effective and safe delivery system suitable for simultaneous topical application of a hydrophilic vitamin C and a lipophilic vitamin E. By changing water content of liquid o/w ME (o/w ME), a gel-like ME with temperature-sensitive rheological properties was formed. The temperature-driven changes in its microstructure were confirmed by rotational rheometry, viscosity measurements, and droplet size determination. The release studies have shown that the vitamins' release at skin temperature from gel-like ME were comparable to those from o/w ME and were much faster and more complete than from o/w ME conventionally thickened with polymer (o/w ME carbomer). According to effectiveness in skin delivery of both vitamins, o/w ME was found the most appropriate, followed by gel-like ME and by o/w ME carbomer, indicating that no simple correlation between vitamins release and skin absorption could be found. The cytotoxicity studies revealed good cell viability after exposure to ME and confirmed all tested microemulsions as nonirritant.

  2. Transdermal drug delivery using microemulsion and aqueous systems: influence of skin storage conditions on the in vitro permeability of diclofenac from aqueous vehicle systems.

    PubMed

    Sintov, Amnon C; Botner, Shafir

    2006-03-27

    The objective of this study was to evaluate the transdermal delivery potential of diclofenac-containing microemulsion system in vivo and in vitro. It was found that the transdermal administration of the microemulsion to rats resulted in 8-fold higher drug plasma levels than those obtained after application of Voltaren Emulgel. After s.c. administration (3.5 mg/kg), the plasma levels of diclofenac reached a peak of 0.94 microg/ml at t=1 h and decreased rapidly to 0.19 microg/ml at t=6 h, while transdermal administration of the drug in microemulsion maintained constant levels of 0.7-0.9 microg/ml for at least 8 h. The transdermal fluxes of diclofenac were measured in vitro using skin excised from different animal species. In three rodent species, penetration fluxes of 53.35+/-8.19 (furry mouse), 31.70+/-3.83 (hairless mouse), 31.66+/-4.45 (rat), and 22.89+/-6.23 microg/cm(2)/h (hairless guinea pig) were obtained following the application of the microemulsion. These fluxes were significantly higher than those obtained by application of the drug in aqueous solution. In contrast to these results, a 'flip-flop' phenomenon was observed when frozen porcine skin (but not fresh skin) was significantly more permeable to diclofenac-in-water than to the drug-in-microemulsion. In fact, the drug penetration from the microemulsion was not affected by the skin storage conditions, but it was increased when an aqueous solution was applied. However, this unusual phenomenon observed in non-freshly used porcine skin places a question mark on its relevancy for in vitro penetration studies involving aqueous vehicle systems.

  3. Microstructure characterization of a food-grade U-type microemulsion system by differential scanning calorimetry and electrical conductivity techniques.

    PubMed

    Zhang, Hui; Taxipalati, Maierhaba; Que, Fei; Feng, Fengqin

    2013-12-01

    The microstructure transitions of a food-grade U-type microemulsion system containing glycerol monolaurate and propionic acid at a 1:1 mass ratio as oil phase and Tween 80 as surfactant were investigated along a water dilution line at a ratio of 80:20 mass% surfactant/oil phase, based on a previously studied phase diagram. From the water thermal behaviours detected by differential scanning calorimetry, three structural regions are identified along the dilution line. In the first region, all water molecules are confined to the water core of the reverse micelles, leading to the formation of w/o microemulsion. As the water content increases, the water gains mobility, transforms into bicontinuous in the second region, and finally the microemulsion become o/w in the third region. The thermal transition points coincide with the structural phase transitions by electrical conductivity measurements, indicating that the structural transitions occur at 35 and 65 mass% of water along the dilution line.

  4. Evaluation of Microemulsion and Lamellar Liquid Crystalline Systems for Transdermal Zidovudine Delivery.

    PubMed

    Carvalho, André Luis Menezes; Silva, José Alexsandro da; Lira, Ana Amélia Moreira; Conceição, Tamara Matos Freire; Nunes, Rogéria de Souza; de Albuquerque Junior, Ricardo Luiz Cavalcanti; Sarmento, Victor Hugo Vitorino; Leal, Leila Bastos; de Santana, Davi Pereira

    2016-07-01

    This study proposed to investigate and to compare colloidal carrier systems containing Zidovudine (3'-azido-3'-deoxythymidine) (AZT) for transdermal administration and optimization of antiretroviral therapy. Microemulsion (ME) and lamellar phase (LP) liquid crystal were obtained and selected from pseudoternary diagrams previously developed. Small-angle X-ray scattering and rheology analysis confirmed the presence of typical ME and liquid crystalline structures with lamellar arrangement, respectively. Both colloidal carrier systems, ME, and LP remained stable, homogeneous, and isotropic after AZT addition. In vitro permeation study (using pig ear skin) showed that the amount of permeated drug was higher for ME compared to the control and LP, obtaining a permeation enhancing effect on the order of approximately 2-fold (p < 0.05). Microscopic examination after in vivo skin irritation studies using mice suggested few histological changes in the skin of animals treated with the ME compared to the control group (hydrogel). Thus, ME proved to be adequate and have promising effects, being able to promote the drug permeation without causing apparent skin irritation. On the order hand, LP functioned as a drug reservoir reducing AZT partitioning into the skin.

  5. Alternative approach to percolation in microemulsions

    SciTech Connect

    Skaf, M.S.; Stell, G. )

    1992-09-15

    An approach to study correlated percolation in lattice models of microemulsions is presented. Mean-field-like equations for the percolation locus for each of the molecular species are obtained, whose only input are the structure functions of the microemulsion model. Using a spin-1 Hamiltonian considered by Gompper and Schick (Phys. Rev. B 41, 9148 (1990)) as a model for microemulsions, we find that the water-percolation threshold increases as the surfactant becomes more lipophilic. This is in qualitative agreement with the behavior found in real microemulsions as salt is added to the system.

  6. Influence of microemulsion structure on cystine reactivity with keratin fibres.

    PubMed

    Solans, C; Parra, J L; Erra, P; Azemar, N; Clausse, M; Touraud, D

    1987-10-01

    Summary The activity of thioglycolic acid, incorporated in a microemulsion, towards cystine residues present in keratin proteins has been investigated. In an attempt to relate the structural state of the microemulsions to cystine reactivity, an appropriate model system showing a large microemulsion domain with diverse structures was chosen. The realm of preferentially hydrocarbon-continuous microemulsion-type media was found to induce the highest activity.

  7. Solvolysis of benzoyl halides in water/NH4DEHP/isooctane microemulsions.

    PubMed

    García-Río, L; Hervella, P; Rodríguez-Dafonte, P

    2006-08-29

    A study was carried out on the solvolysis reactions of different benzoyl halides in microemulsions of water/NH4DEHP/isooctane, where NH4DEHP is ammonium bis(2-ethylhexyl) phosphate. Because of the low solubility of benzoyl halides in water, they are distributed between the continuous medium and the interface of the microemulsion, where the reaction takes place. The application of the pseudophase model has allowed us to obtain the distribution constants and the rate constants at the interface for the benzoyl halides. Reaction mechanisms and the changes in these mechanisms in terms of the water content of the microemulsion have been determined on the basis of kinetic data. The influence of the substituent and the leaving group on the reaction rate has been investigated. A comparison of kinetic results with those previously obtained in water/AOT/isooctane microemulsions allows a kinetic evaluation of the change in the microemulsion properties with the surfactant.

  8. Microemulsion of Molten Salts

    DTIC Science & Technology

    1991-02-01

    seen similar behavior in other systems. Shinoda ( Shinoda 1983; Shinoda and Lindman 1987) referred to the microemulsion phase as a surfactant or...483, 1971. Shinoda , K. Prog. Colloid and Polymer Sci. Vol. 68, p. 1, 1983. Shinoda , K., and B. Lindman. Langmuir. Vol. 3, p. 135, 1987. Talmon, Y...Office ATTN: SMCAR-AEE, ATTN: Chemistry Division Mike Joyce P.O. Box 12211 Charles Capussino Research Triangle Park, NC Picatinny Arsenal, NJ 07801-5001

  9. Formulation of ascorbic acid microemulsions with alkyl polyglycosides.

    PubMed

    Pakpayat, N; Nielloud, F; Fortuné, R; Tourne-Peteilh, C; Villarreal, A; Grillo, I; Bataille, B

    2009-06-01

    Ascorbic acid microemulsions for topical application were developed. In this study, microemulsions were prepared using HLD (hydrophilic lipophilic deviation) concept to optimise the formulation. From this optimal formulation, the realisation of dilution ternary diagrams leads to obtain microemulsion zones. In addition, the effects of composition variable on the physicochemical characteristics of each system were investigated. After optimisation of the microemulsion systems, ascorbic acid was loaded in the formulations. Surface tension and small angle neutron scattering were used to characterise the surface properties and the structure of the microemulsions. Bicontinuous structure microemulsions were identified, and the influence of ascorbic acid localisation at the interface leading to modifications of the microemulsion structure was pointed out. The solubilisation of ascorbic acid, the stabilisation and in vitro transdermal penetration "Frantz cells" of ascorbic acid microemulsions were studied. Three different microemulsions were envisaged. The results confirmed that these microemulsion systems present a real interest for formulation and protection of ascorbic acid. Regarding their transcutaneous penetration behaviour, the different microemulsions studied could be useful for different topical applications. A major location of ascorbic acid found in the epidermis where the decomposition of melanin occurred indicates that microemulsion could be considered as a suitable carrier system for application of ascorbic acid as a whitening agent. In addition, a good passage of the drug in the dermis could be interesting for the relative oxygen matrix damage.

  10. Nonlinear effects of electric fields in the Belousov-Zhabotinsky reaction dissolved in a microemulsion

    NASA Astrophysics Data System (ADS)

    Dähmlow, Patricia; Müller, Stefan C.

    2015-04-01

    Labyrinth-like Turing patterns are investigated under the influence of an electric field. The patterns form in the ferroin-catalyzed Belousov-Zhabotinsky reaction embedded in the sodium-bis (2-ethylhexyl) sulfosuccinate (AOT) water-in-oil microemulsion. For two different values of the droplet fraction above and below the percolation transition of the system, the electric field induced drift of the patterns is different. Above the percolation transition, a linear increase of the drift velocity with increasing electric field strength is found. However, below the percolation transition, this increase shows an exponential behavior. The patterns are also observed to reorient under high electrical field strength, such that they are arranged perpendicular with respect to the field lines.

  11. Nonlinear effects of electric fields in the Belousov-Zhabotinsky reaction dissolved in a microemulsion.

    PubMed

    Dähmlow, Patricia; Müller, Stefan C

    2015-04-01

    Labyrinth-like Turing patterns are investigated under the influence of an electric field. The patterns form in the ferroin-catalyzed Belousov-Zhabotinsky reaction embedded in the sodium-bis (2-ethylhexyl) sulfosuccinate (AOT) water-in-oil microemulsion. For two different values of the droplet fraction above and below the percolation transition of the system, the electric field induced drift of the patterns is different. Above the percolation transition, a linear increase of the drift velocity with increasing electric field strength is found. However, below the percolation transition, this increase shows an exponential behavior. The patterns are also observed to reorient under high electrical field strength, such that they are arranged perpendicular with respect to the field lines.

  12. Preparation of ZnSe Nanocrystals Using Water-in-Oil Microemulsions

    NASA Astrophysics Data System (ADS)

    Hyun Soo Kim,; Jong Sung Kim,; Sang Joon Park,

    2010-06-01

    ZnSe nanocrystals were prepared using a safe and simple synthetic method by employing a sodium bis(2-ethylhexyl) sulfosuccinate (AOT)/water/oil microemulsion system with aqueous ZnSO4 and Se2- solutions, and characterized by X-ray diffraction (XRD) analysis, photoluminescence (PL) spectroscopy, and transmission electron microscopy (TEM). To control the diameter of nanocrystals in the quantum confinement region, the synthesis was performed with different oil phases (heptane and cyclohexane) and various water-to-surfactant ratios, W ([H2O]/[surfactant]). Cubic zinc blende ZnSe nanocrystals were synthesized and their size was controlled in the range from 2.5 to 17 nm. The maximum PL efficiency was 14% for the smallest ZnSe nanocrystal.

  13. Activity of alkaline phosphatase in water-in-oil microemulsions containing vegetable oil.

    PubMed

    Gupta, S; Mukhopadhyay, L; Moulik, S P

    1995-10-01

    The hydrolysis of p-nitrophenyl phosphate by the enzyme alkaline phosphatase has been studied in vegetable oil containing water-in-oil (W/O) microemulsions of six different compositions at four different (water)/(surfactant) mole ratios of 10, 17.6, 24.7 and 37. The vegetable oils used are ricebran oil (RO) and clove oil (CO) and the amphiphiles used are Aerosol OT (AOT), cinnamic alcohol (CA) and Tween-20 (T-20). The hydrolytic process does not follow conventional Michaelis Menten equation normally observed for enzymatic process. In the water/vegetable oil microemulsions, the enzyme seems to lose its activity when AOT is the amphiphile. The amount of p-nitrophenol generated as a result of hydrolysis is independent of the presence of the enzyme. With Tween-20 as the amphiphile, the microemulsion produces an initial retarding effect which ultimately gets appreciably compensated.

  14. Phospholipid structured microemulsion as effective carrier system with potential in methicillin sensitive Staphylococcus aureus (MSSA) involved burn wound infection.

    PubMed

    Chhibber, Tanya; Wadhwa, Sheetu; Chadha, Parul; Sharma, Gajanand; Katare, Om Prakash

    2015-12-01

    Burn wounds are foremost site for bacterial colonization and multiplication. Staphylococcus aureus is one of the most predominant pathogen found in burn wounds. Fusidic acid (FA) is widely employed in the treatment of complicated skin infections caused by Staphylococcus aureus. Hence, the aim of this study was to investigate the usefulness and efficacy of topical FA (2% w/w) loaded biocompatible microemulsion-based-system (FA-ME) in eradicating MSSA bacterial infections which otherwise was less effective when dealt with conventional formulations. For construction of pseudoternary phase diagram, ratio of oil (IPM):water:Smix is 20:30:50% w/w and proportion of Smix (Phospholipid:Tween 80 (T80):Ethanol) is in the ratio of 1:2:1, respectively. The hypothesis relates here to the role of phospholipids as part of the nano-scale structure of microemulsion systems to overcome the hurdles of drug delivery. The prepared FA-ME system was evaluated for its therapeutic efficacy and carrier-specific characteristics such as globule size, % transmittance, transmission electron microscopy, drug content and stability. Selected microemulsion system was incorporated into gel form and evaluated for texture analysis, drug permeation in 24 h and treatment of burn wounds. Burn wound infection was established with MSSA ATCC 25923 in BALB/c mice and the process of wound healing as well as bacterial loading in the wound was estimated. The developed nanosized FA-ME system demonstrated improved wound healing, better spreadability and enhanced therapeutic efficacy due to the changes in the behavior of the drug molecules by way of carrier-characteristics.

  15. Preparation of starch nanoparticles in water in oil microemulsion system and their drug delivery properties.

    PubMed

    Wang, Xinge; Chen, Haiming; Luo, Zhigang; Fu, Xiong

    2016-03-15

    In this research, 1-hexadecyl-3-methylimidazolium bromide C16mimBr/butan-1-ol/cyclohexane/water ionic liquid microemulsion was prepared. The effects of n-alkyl alcohols, alkanes, water content and temperature on the properties of microemulsion were studied by dilution experiment. The microregion of microemulsion was identified by pseudo-ternary phase diagram and conductivity measurement. Then starch nanoparticles were prepared by water in oil (W/O) microemulsion-cross-linking methods with C16mimBr as surfactant. Starch nanoparticles with a mean diameter of 94.3nm and narrow size distribution (SD=3.3) were confirmed by dynamic light scattering (DLS). Scanning electron microscope (SEM) data revealed that starch nanoparticles were spherical granules with the size about 60nm. Moreover the results of Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) demonstrated the formation of cross-linking bonds in starch molecules. Finally, the drug loading and releasing properties of starch nanoparticles were investigated with methylene blue (MB) as drug model. This work may provide an efficient pathway to synthesis starch nanoparticles.

  16. Microemulsions as novel drug carriers: the formation, stability, applications and toxicity.

    PubMed

    Karasulu, H Yesim

    2008-01-01

    A microemulsion, made from water, oil, surfactants and cosurfactant is a thermodynamically stable system. The presence of the cosurfactant is often required in order to lower the interfacial tension of this interface, because a low interfacial tension is essential for the formation of microemulsions. The transparency of microemulsions arises from their small droplet diameter. The droplet diameter in stable microemulsions is usually within the range of 10 - 140 nm. Microemulsions are graphically represented as stability areas in triangular phase diagrams where each triangular corner designates a certain component. Microemulsions are actually quaternary (pseudoternary) systems. In pharmaceutical fields, the interest in microemulsions is increasing and, thus, they are applied to various administration routes.

  17. Temperature-, electric field- and solute-induced percolation in water-in-oil microemulsions.

    PubMed

    Schlicht, L; Spilgies, J H; Runge, F; Lipgens, S; Boye, S; Schübel, D; Ilgenfritz, G

    1996-01-16

    We report investigations on the percolation of the aqueous phase in water-in-oil microemulsions, comparing systems stabilized by ionic AOT and non-ionic Igepal amphiphiles. First, we briefly review the opposite effect of temperature on the two systems and compare electric conductivity with viscosity data. In the second part, we show that percolation can be induced by high electric fields resulting in a shift of the percolation curve. The electric field measurements allow to investigate the dynamics of clustering of the water droplets to form a network of percolating channels. We examine the slow build-up and the fast decay of the percolating structure, monitoring simultaneously electric conductivity and electric birefringence. In the third part we discuss the effect of some solutes on the percolation curve, especially of small molecules which act as protein denaturants and of native and denatured proteins like methemoglobin, chymotrypsin and gelatin. The spectroscopic determination of the dimerization of hemin, released from denatured hemoglobin, reflects the incorporation of the hemin monomers in the surfactant monolayer. In the gelatin system time resolved electric birefringence shows that even at low concentrations it is the macromolecule which determines the structure of the aqueous domain. In the appendix, a simple estimate of the intrinsic Kerr-constant is given for microemulsion droplets deformed in an electric field.

  18. Ionic liquid tunes microemulsion curvature.

    PubMed

    Liu, Liping; Bauduin, Pierre; Zemb, Thomas; Eastoe, Julian; Hao, Jingcheng

    2009-02-17

    Middle-phase microemulsions formed from cationic dioctadecyldimethylammonium chloride (DODMAC), anionic sodium dodecylsulfate (SDS), n-butanol, and n-heptane were studied. An ionic liquid (IL), 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF4]), was employed as the electrolyte in the aqueous media instead of inorganic salts usually used in microemulsion formulation. Studies have been carried out as a function of the concentrations of [bmim][BF4], n-butanol, total surfactant (cDODMAC+SDS), and temperature on the phase behavior and the ultralow interfacial tensions in which the anionic component is present in excess in the catanionic film. Ultralow interfacial tension measurements confirmed the formation of middle-phase microemulsions and the necessary conditions for stabilizing middle-phase microemulsions. Electrical conductivity, small-angle X-ray scattering (SAXS), and small-angle neutron scattering (SANS) experiments were also performed, indicating that the typical heptane domain size has an average radius of 360 A and the ionic liquid induces softening of the charged catanionic film. Most interestingly, the IL concentration (cIL) is shown to act as an effective interfacial curvature-control parameter, representing a new approach to tuning the formulation of microemulsions and emulsions. The results expand the potential uses of ILs but also point to the design of new ILs that may achieve superefficient control over interfacial and self-assembly systems.

  19. Pore Scale Dynamics of Microemulsion Formation.

    PubMed

    Unsal, Evren; Broens, Marc; Armstrong, Ryan T

    2016-07-19

    Experiments in various porous media have shown that multiple parameters come into play when an oleic phase is displaced by an aqueous solution of surfactant. In general, the displacement efficiency is improved when the fluids become quasi-miscible. Understanding the phase behavior oil/water/surfactant systems is important because microemulsion has the ability to generate ultralow interfacial tension (<10(-2) mN m(-1)) that is required for miscibility to occur. Many studies focus on microemulsion formation and the resulting properties under equilibrium conditions. However, the majority of applications where microemulsion is present also involve flow, which has received relatively less attention. It is commonly assumed that the characteristics of an oil/water/surfactant system under flowing conditions are identical to the one under equilibrium conditions. Here, we show that this is not necessarily the case. We studied the equilibrium phase behavior of a model system consisting of n-decane and an aqueous solution of olefin sulfonate surfactant, which has practical applications for enhanced oil recovery. The salt content of the aqueous solution was varied to provide a range of different microemulsion compositions and oil-water interfacial tensions. We then performed microfluidic flow experiments to study the dynamic in situ formation of microemulsion by coinjecting bulk fluids of n-decane and surfactant solution into a T-junction capillary geometry. A solvatochromatic fluorescent dye was used to obtain spatially resolved compositional information. In this way, we visualized the microemulsion formation and the flow of it along with the excess phases. A complex interaction between the flow patterns and the microemulsion properties was observed. The formation of microemulsion influenced the flow regimes, and the flow regimes affected the characteristics of the microemulsion formation. In particular, at low flow rates, slug flow was observed, which had profound

  20. Development of Microemulsion Delivery System of Essential Oil from Zingiber cassumunar Roxb. Rhizome for Improvement of Stability and Anti-Inflammatory Activity.

    PubMed

    Chaiyana, Wantida; Anuchapreeda, Songyot; Leelapornpisid, Pimporn; Phongpradist, Rungsinee; Viernstein, Helmut; Mueller, Monika

    2016-08-08

    The present study aims to investigate the major constituents of the essential oil from Zingiber cassumunar rhizome (EO) and to develop microemulsions with enhanced chemical stability and anti-inflammatory activity of EO. The major constituents of EO were terpinen-4-ol (40.5 ± 6.6%) and sabinene (17.4 ± 1.4%) as determined by gas chromatography-mass spectrometry. These compounds were responsible for the anti-inflammatory activities of EO. Sabinene and terpinen-4-ol significantly reduced nuclear factor-kappa B (NF-kB) expression by 47 ± 5 and 78 ± 8%, respectively (p < 0.001) and significantly reduced the interleukin-6 (IL-6) secretion levels to 64 ± 4% (p < 0.05) and 50 ± 1% (p < 0.001), respectively. EO microemulsions, developed using the system of EO/Tween 20 and propylene glycol (2:1)/water, showed the internal droplet size in the range of 211.5 ± 63.3 to 366.7 ± 77.8 nm. Both EO and EO microemulsions were shown to be safe for human use since there was no apparent toxic effect on human peripheral blood mononuclear cells. Interestingly, EO microemulsion could significantly protect sabinene from the evaporation after heating-cooling stability test, which leads to a good stability and high efficacy. Moreover, EO microemulsions significantly enhanced the anti-inflammatory effect comparing to the native EO. Therefore, microemulsions were attractive delivery system for natural anti-inflammatory compounds since they could enhance both efficacy and stability of EO.

  1. Luminescence probe study of the conditions affecting colloidal semiconductor growth in reverse micelles and water-in-oil microemulsions

    SciTech Connect

    Modes, S.; Lianos, P. )

    1989-07-27

    A series or reverse AOT micelles and w/o microemulsions have been studied by analyzing the luminescence decay of ruthenium tri(2,2{prime}-bipyridine) in the presence of quencher. The analysis was based both on the established model for luminescence decay in micelles and on the recently developed fractal model of microemulsions. Colloidal cadmium sulfide has then been produced in the microemulsions and the conditions for the particle size growth and size polydispersity have been related with the data of the luminescence decay analysis.

  2. Stability and disperse composition of water-in-oil microemulsions in a tributyl phosphate-nitric acid system

    SciTech Connect

    Vinogradov, I.V.; Zakharkin, V.S.; Shepel'kov, S.V.

    1988-05-01

    An investigation has been made of the influence of the concentrations of tributyl phosphate (TBP) and nitric acid on the surface and bulk distribution, the stability, and the disperse composition of water-in-oil microemulsions. A correlation has been established between the interphase tension and the time for complete stratification of the microemulsions. The process of forming stable microemulsions is interpreted on the basis of views on the surfactant properties of TBP hydratosolvates.

  3. Heavy metals extraction by microemulsions.

    PubMed

    Dantas, T N Castro; Dantas Neto, A A; Moura, M C P A; Barros Neto, E L; Forte, K R; Leite, R H L

    2003-06-01

    The objective of this study is the heavy metal extraction by microemulsion, using regional vegetable oils as surfactants. Firstly, the main parameters, which have influence in the microemulsion region, such as: nature of cosurfactant, influence of cosurfactant (C)/surfactant (S) ratio and salinity were studied, with the objective of choosing the best extraction system. The extraction/reextraction process by microemulsion consists of two stages. In the first one, the heavy metal ion present in the aqueous phase is extracted by the microemulsion. In a second step, the reextraction process occurs: the microemulsion phase, rich in metal, is acidified and the metal is recovered in a new aqueous phase, with higher concentration. The used system had the following parameters: surfactant-saponified coconut oil; cosurfactant-n-butanol; oil phase-kerosene; C/S ratio=4; salinity-2% (NaCl); temperature of 27+/-1 degrees C; water phase-aqueous solution that varied according to the heavy metal in study (Cr, Cu, Fe, Mn, Ni and Pb). A methodology of experimental planning was used (Scheffé Net) to study the behavior of the extraction in a chosen domain. The extraction was accomplished in one step and yielded extraction percentage higher than 98% for all metals. In the reextraction HCl-8M was used as reextraction agent and the influence of the pH and time were verified. This work showed the great efficiency of the microemulsion, indicating that it is possible to extract selectively the heavy metals from the aqueous phase.

  4. Fourier transform infrared spectroscopy of azide and cyanate ion pairs in AOT reverse micelles

    NASA Astrophysics Data System (ADS)

    Owrutsky, Jeffrey C.; Pomfret, Michael B.; Barton, David J.; Kidwell, David A.

    2008-07-01

    Evidence for ion pair formation in aqueous bis(2-ethylhexyl) sulfosuccinate (AOT) reverse micelles (RMs) was obtained from infrared spectra of azide and cyanate with Li+, Na+, K+, and NH4+ counterions. The anions' antisymmetric stretching bands near 2000 cm-1 are shifted to higher frequency (blueshifted) in LiAOT and to a lesser extent in NaAOT, but they are very similar to those in bulk water with K+ and NH4+ as the counterions. The shifts are largest for low values of wo=[water]/[AOT] and approach the bulk value with increasing wo. The blueshifts are attributed to ion pairing between the anions and the counterions. This interpretation is reinforced by the similar trend (Li+>Na+>K+) for producing contact ion pairs with the metal cations in bulk dimethyl sulfoxide (DMSO) solutions. We find no evidence of ion pairs being formed in NH4AOT RMs, whereas ammonium does form ion pairs with azide and cyanate in bulk DMSO. Studies are also reported for the anions in formamide-containing AOT RMs, in which blueshifts and ion pair formation are observed more than in the aqueous RMs. Ion pairs are preferentially formed in confined RM systems, consistent with the well established ideas that RMs exhibit reduced polarity and a disrupted hydrogen bonding network compared to bulk water and that ion-specific effects are involved in mediating the structure of species at interfaces.

  5. Enhanced insulin absorption from sublingual microemulsions: effect of permeation enhancers.

    PubMed

    Patil, Nilam H; Devarajan, Padma V

    2014-12-01

    Microemulsions of insulin (50 IU/mL) comprising permeation enhancers were formulated for sublingual delivery. Circular dichroism (CD) spectra indicated conformational stability, while chemical stability was confirmed by high-performance liquid chromatography (HPLC). CD spectra of insulin in combination with permeation enhancers revealed attenuation of molar ellipticity at 274 nm in the order TCTP > TC-AOT > TC > TC-NMT > Sol P > insulin solution. The molar ellipticity ratios at 208/222 nm confirmed dissociation of insulin in the microemulsions with the same rank order. Matrix-assisted laser diffraction ionization mass spectra (MALDI) revealed a significant shift in intensity signals towards monomer and dimers with a substantially high ratio of monomers, especially in the presence of the TCTP and TC-AOT. Permeation through porcine sublingual mucosa correlated with the dissociation data. A high correlation between the ratio of molar ellipticity at 208/222 nm and serum glucose levels (r (2) > 0.958) and serum insulin levels (r (2) > 0.952) strongly suggests the role of dissociation of insulin on enhanced absorption. While all microemulsions revealed a reduction in serum glucose levels and increase in serum insulin levels, significant differences were observed with the TCTP and TC-AOT microemulsions. High pharmacological availability >60 % and bioavailability >55 % compared to subcutaneous insulin at a low dose of 2 IU/kg appears highly promising. The data clearly suggests the additional role of the permeation enhancers on dissociation of insulin on enhanced sublingual absorption from the microemulsions.

  6. Water-in-ionic liquid microemulsion formation in solvent mixture of aprotic and protic imidazolium-based ionic liquids.

    PubMed

    Kusano, Takumi; Fujii, Kenta; Hashimoto, Kei; Shibayama, Mitsuhiro

    2014-10-14

    We report that water-in-ionic liquid microemulsions (MEs) are stably formed in an organic solvent-free system, i.e., a mixture of aprotic (aIL) and protic (pIL) imidazolium-based ionic liquids (ILs) containing the anionic surfactant dioctyl sulfosuccinate sodium salt (AOT). Structural investigations using dynamic light, small-angle X-ray, and small-angle neutron scatterings were performed for MEs formed in mixtures of aprotic 1-octyl-3-methylimidazolium ([C8mIm(+)]) and protic 1-alkylimidazolium ([CnImH(+)], n = 4 or 8) IL with a common anion, bis(trifluoromethanesulfonyl)amide ([TFSA(-)]). It was found that the ME structure strongly depends on the mixing composition of the aIL/pIL in the medium. The ME size appreciably increases with increasing pIL content in both [C8mIm(+)][TFSA(-)]/[C8ImH(+)][TFSA(-)] and [C8mIm(+)][TFSA(-)]/[C4ImH(+)][TFSA(-)] mixtures. The size is larger for the n = 8 system than that for the n = 4 system. These results indicate that the shell part of MEs is composed of both AOT and pIL cation, and the ME size can be tuned by pIL content in the aIL/pIL mixtures.

  7. Effect of alpha-lactalbumin on the phase behavior of AOT-brine-isooctane mixtures: role of charge interactions.

    PubMed

    Shimek, Justin W; Rohloff, Catherine M; Goldberg, Jessica; Dungan, Stephanie R

    2005-06-21

    We have found that both electrostatic and hydrophobic interactions are involved in the ability of the protein alpha-lactalbumin (alpha-LA) to affect the self-assembly of the anionic surfactant sodium bis(ethylhexyl) sulfosuccinate (AOT, 3.5 wt %) in equivolume mixtures of organic and aqueous solutions. The composition and size of AOT phase structures that form in the presence of 0.35 wt % protein were evaluated as a function of pH and ionic strength. In the absence of protein, AOT forms water-in-oil microemulsion droplets for all pH and salt concentrations studied here. The presence of the protein in the water-in-oil microemulsion phase boosts water solubilization and droplet size, as the spontaneous curvature of the surfactant interface becomes less negative. Aggregates of protein, surfactant, and oil also form in the water-continuous phase. The size and composition of structures in both phases can be tuned in the presence of protein by varying the pH and ionic strength. alpha-LA induces the appearance of an anisotropic surfactant phase at pH <5.8. At intermediate salt concentrations, a third isotropic, viscous aqueous phase appears that contains 55-60% of the protein, 10-14% of the surfactant, and significant amounts of oil. Circular dichroism and fluorescence spectroscopy indicate that the protein contains enhanced alpha-helical secondary structure when self-assembling with surfactant, and has a loosened tertiary structure. The protein does not interact with the surfactant as an unfolded random coil. Although the conformation of alpha-LA in aqueous salt solutions is known to depend on pH, when self-assembling with AOT the protein adopts a structure whose features are quite pH insensitive, and likely reflect an intrinsic interaction with the interface.

  8. Dielectric relaxation and percolation phenomena in ternary microemulsions

    NASA Astrophysics Data System (ADS)

    Peyrelasse, J.; Moha-Ouchane, M.; Boned, C.

    1988-07-01

    Dielectric relaxation of water/AOT/oil (iso-octane, undecane, dodecane, cyclohexane) microemulsions was studied by means of time-domain spectroscopy. [Here AOT is an abbreviation for sodium bis(2-ethylhexyl)sulfosuccinate.] The experiments were carried out for several values of the volume fraction φ (water + AOT) and of the molar ratio n= [water]/[AOT]. They showed the presence of a maximum of static permittivity ɛs associated with a minimum of the relaxation frequency νR and a maximum of the frequency-spread parameter α. The influence of the salt content was also considered. The results are discussed with reference to the theory of percolation, and were found to be in close agreement with the theoretical predictions. By analogy with previous results on conductivity [M. Moha-Ouchane, J. Peyrelasse, and C. Boned, Phys. Rev. A 35, 3027 (1987)], the influence of temperature is discussed. The important part played by interactions and the phenomenon of ``hopping'' are demonstrated in connection with an already existing model (an off-lattice simulation). Finally, the results show the importance of the notion of ``percolation threshold lines'' introduced previously (Moha-Ouchane, Peyrelasse, and Boned).

  9. Dynamic and spectroscopic studies of nano-micelles comprising dye in water/ dioctyl sodium sulfosuccinate /decane droplet microemulsion at constant water content

    NASA Astrophysics Data System (ADS)

    Rahdar, Abbas; Almasi-Kashi, Mohammad

    2017-01-01

    In the present work, the dynamic and spectroscopic properties of water-in-decane dioctyl sodium sulfosuccinate (AOT) microemulsions comprising dye, Rhodamine B (RB), were studied by varying content of decane at the constant water content (W = 20), by using dynamic light scattering (DLS), UV/visible, and fluorescence techniques. The characterization results of DLS of AOT micelles showed that by decreasing concentration of Rhodamine B in the water/AOT/decane microemulsion, the inter-droplet interactions changed from attractive to repulsive as the mass fraction of nano-droplets (MFD) increased. A deviation in the absorption spectra of Rhodamine B from the Beer's law at the high Rhodamine B concentration (0.001) was observed in the AOT reversed micelles. The Quenching in the emission intensity of AOT droplets comprising Rhodamine B and red shift in λmax of fluorescence of dye was observed as a function of concentration of RB in AOT RMs. The Stokes shift of AOT droplets containing the high concentration of RB, increased with mass fraction of nano-droplet (MFD), whereas at the low Rhodamine B concentration, its variation remained constant up to MFD = 0.07, and then increased.

  10. Microemulsion-based drug delivery system for transnasal delivery of Carbamazepine: preliminary brain-targeting study.

    PubMed

    Patel, Rashmin Bharatbhai; Patel, Mrunali Rashmin; Bhatt, Kashyap K; Patel, Bharat G; Gaikwad, Rajiv V

    2016-01-01

    This study reports the development and evaluation of Carbamazepine (CMP)-loaded microemulsions (CMPME) for intranasal delivery in the treatment of epilepsy. The CMPME was prepared by the spontaneous emulsification method and characterized for physicochemical parameters. All formulations were radiolabeled with (99m)Tc (technetium) and biodistribution of CMP in the brain was investigated using Swiss albino rats. Brain scintigraphy imaging in rats was also performed to determine the uptake of the CMP into the brain. CMPME were found crystal clear and stable with average globule size of 34.11 ± 1.41 nm. (99m)Tc-labeled CMP solution (CMPS)/CMPME/CMP mucoadhesive microemulsion (CMPMME) were found to be stable and suitable for in vivo studies. Brain/blood ratio at all sampling points up to 8 h following intranasal administration of CMPMME compared to intravenous CMPME was found to be 2- to 3-fold higher signifying larger extent of distribution of the CMP in brain. Drug targeting efficiency and direct drug transport were found to be highest for CMPMME post-intranasal administration compared to intravenous CMP. Rat brain scintigraphy also demonstrated higher intranasal uptake of the CMP into the brain. This investigation demonstrates a prompt and larger extent of transport of CMP into the brain through intranasal CMPMME, which may prove beneficial for treatment of epilepsy.

  11. Solubilization of water in water-in-oil microemulsions of kerosene

    SciTech Connect

    Andheria, A.P.; Bhagwat, S.S.

    1995-04-01

    The incorporation of water into fuels formulated as microemulsions can offer several advantages such as fire resistance, increased flash point, and improved air-fuel contact. To this end, phase equilibria of kerosene microemulsions employing ionic and nonionic surfactants such as sodium di-(2-ethylhexyl) sulfosuccinate (AOT), lauryl diethanolamide (LDEA), nonylphenol EO-4.5 (NPEO-4.5), sorbitan monolaurate (Span-20), and cetyltrimethylammonium bromide (CTAB), as well as cosurfactants such as n-pentanol, n-hexanol, and n-heptanol, were studied. The effect of the aromaticity of the oil phase on the solubilization of water was also investigated.

  12. Nose to brain microemulsion-based drug delivery system of rivastigmine: formulation and ex-vivo characterization.

    PubMed

    Shah, Brijesh M; Misra, Manju; Shishoo, Chamanlal J; Padh, Harish

    2015-01-01

    Alzheimer's disease (AD) is a progressive neurodegenerative disorder leading to irreversible loss of neurons, cognition and formation of abnormal protein aggregates. Rivastigmine, a reversible cholinesterase inhibitor used for the treatment of AD, undergoes extensive first-pass metabolism, thus limiting its absolute bioavailability to only 36% after 3-mg dose. Due to extreme aqueous solubility, rivastigmine shows poor penetration and lesser concentration in the brain thus requiring frequent oral dosing. This investigation was aimed to formulate microemulsion (ME) and mucoadhesive microemulsions (MMEs) of rivastigmine for nose to brain delivery and to compare percentage drug diffused for both systems using in-vitro and ex-vivo study. Rivastigmine-loaded ME and MMEs were prepared by titration method and characterized for drug content, globule size distribution, zeta potential, pH, viscosity and nasal ciliotoxicity study. Rivastigmine-loaded ME system containing 8% w/w Capmul MCM EP, 44% w/w Labrasol:Transcutol-P (1:1) and 48% w/w distilled water was formulated, whereas 0.3% w/w chitosan (CH) and cetyl trimethyl ammonium bromide (as mucoadhesive agents) were used to formulate MMEs, respectively. ME and MMEs formulations were transparent with drug content, globule size and zeta potential in the range of 98.59% to 99.43%, 53.8 nm to 55.4 nm and -2.73 mV to 6.52 mV, respectively. MME containing 0.3% w/w CH followed Higuchi model (r(2) = 0.9773) and showed highest diffusion coefficient. It was free from nasal ciliotoxicity and stable for three months. However, the potential of developed CH-based MME for nose to brain delivery of rivastigmine can only be established after in-vivo and biodistribution study.

  13. Risk-based evaluation of Allowed Outage Times (AOTs) considering risk of shutdown

    SciTech Connect

    Mankamo, T. ); Kim, I.S.; Samanta, P.K. )

    1992-01-01

    When safety systems fail during power operation, Technical Specifications (TS) usually limit the repair within Allowed Outage Time (AOT). If the repair cannot be completed within the AOT, or no AOT is allowed, the plant is required to be shut down for the repair. However, if the capability to remove decay heat is degraded, shutting down the plant with the need to operate the affected decay-heat removal systems may impose a substantial risk compared to continued power operation over a usual repair time. Thus, defining a proper AOT in such situations can be considered as a risk-comparison between the repair in frill power state with a temporarily increased level of risk, and the altemative of shutting down the plant for the repair in zero power state with a specific associated risk. The methodology of the risk-comparison approach, with a due consideration of the shutdown risk, has been further developed and applied to the AOT considerations of residual heat removal and standby service water systems of a boiling water reactor (BWR) plant. Based on the completed work, several improvements to the TS requirements for the systems studied can be suggested.

  14. Risk-based evaluation of Allowed Outage Times (AOTs) considering risk of shutdown

    SciTech Connect

    Mankamo, T.; Kim, I.S.; Samanta, P.K.

    1992-12-31

    When safety systems fail during power operation, Technical Specifications (TS) usually limit the repair within Allowed Outage Time (AOT). If the repair cannot be completed within the AOT, or no AOT is allowed, the plant is required to be shut down for the repair. However, if the capability to remove decay heat is degraded, shutting down the plant with the need to operate the affected decay-heat removal systems may impose a substantial risk compared to continued power operation over a usual repair time. Thus, defining a proper AOT in such situations can be considered as a risk-comparison between the repair in frill power state with a temporarily increased level of risk, and the altemative of shutting down the plant for the repair in zero power state with a specific associated risk. The methodology of the risk-comparison approach, with a due consideration of the shutdown risk, has been further developed and applied to the AOT considerations of residual heat removal and standby service water systems of a boiling water reactor (BWR) plant. Based on the completed work, several improvements to the TS requirements for the systems studied can be suggested.

  15. Block-copolymer-induced structure formation in microemulsions

    SciTech Connect

    Hilfiker, R.; Eicke, H.F.; Steeb, C.; Hofmeier, U. )

    1991-02-07

    Transient electric birefringence measurements were performed on water/AOT (sodium bis(2-ethylhexyl) sulfosuccinate)/isooctane microemulsions with various amounts of block-copoly(oxyethylene/isoprene/oxyethylene) added. The authors could show that addition of the copolymer leads to a formation of nanodroplet (ND)-copolymer-aggregates. The contributions of NDs and aggregates to the induced birefringence could easily be separated because the NDs exhibited a negative and the aggregates a positive induced birefringence and because the time scales corresponding to the two processes were different.

  16. Interfacial hydrodynamic instabilities driven by cross-diffusion in reverse microemulsions

    NASA Astrophysics Data System (ADS)

    Budroni, M. A.; Carballido-Landeira, J.; Intiso, A.; De Wit, A.; Rossi, F.

    2015-06-01

    When two microemulsions are put in contact in the gravity field along a horizontal contact line, cross-diffusion can trigger the transport of one species in the presence of a gradient in concentration of another species. We show here theoretically that such cross-diffusion effects can induce buoyancy-driven convective instabilities at the interface between two solutions of different compositions even when initially the less dense solution lies on top of the denser one. Two different sources of convective modes are identified depending whether positive or negative cross-diffusion is involved. We evidence the two predicted cross-diffusion driven instabilities experimentally using a two-layer stratification of Aerosol-OT (AOT) water-in-oil microemulsions solutions with different water or AOT composition.

  17. Conductive microemulsions for template CoNi electrodeposition.

    PubMed

    Serrà, Albert; Gómez, Elvira; Calderó, Gabriela; Esquena, Jordi; Solans, Conxita; Vallés, Elisa

    2013-09-21

    Microemulsions have been revealed as feasible templates to grow magnetic nanostructures using an electrodeposition method. Reducing agents are not required and the applied potential has been used as driving force of the nanostructure growth. A systematic study of conductive microemulsion systems to allow the CoNi electrodeposition process has been performed. Different surfactants and organic components have been tested to form microemulsions with a CoNi electrolytic bath as an aqueous component in order to define the microemulsions showing enough conductivity to perform an electrodeposition process from the aqueous component. By using microemulsions of the aqueous electrolyte solution-Triton X-100-diisopropyl adipate system, CoNi electrodeposition has been achieved, the structure of the deposits being dependent on the composition and structure of the microemulsion, which can act as a soft-template to obtain different discontinuous deposits. The magnetic properties of the CoNi deposits vary with their structure.

  18. Preparation of hollow silica nanospheres in O/W microemulsion system by hydrothermal temperature changes

    NASA Astrophysics Data System (ADS)

    Wang, Dandan; Li, Xiuyan; Liu, Zuohua; Shi, Xue; Zhou, Guowei

    2017-01-01

    Hollow silica nanospheres with wrinkled or smooth surfaces were successfully fabricated through a hydrothermal method. In this method, oil-in-water microemulsion (composed of cyclohexane, water, ethanol, and cetyltrimethylammonium bromide), and polyvinylpyrrolidone were utilized as template and capping agent, respectively. In such a facile synthesis, we can well realize the morphological transformation of spheres with radially oriented mesochannels to hollow structures of silica nanoparticle only by regulating the hydrothermal temperature from 100 °C to 200 °C. Synthesized samples with different mesostructures were then used as supports to immobilize Candida rugosa lipase (CRL). The immobilized CRL was employed as a new biocatalyst for biodiesel production through the esterification of heptanoic acid with ethanol. The conversion ratio of heptanoic acid with ethanol catalyzed by the immobilized CRL was also evaluated. Results of this study suggest that the prepared samples have potential applications in biocatalysis.

  19. Equilibria and structures of microemulsions and liquid crystals in water-surfactant-oil systems

    SciTech Connect

    Danielsson, I.; Friman, R.; Sjoblom, J.

    1982-02-01

    Microemulsions and lyotropic mesophases in aqueous solutions of association colloids are closely related. The ionic groups are always completely hydrated in micelles and mesoaggregates. Strong evidence of this is provided by the fact that the heat of solution of solid sodium octanoate both in a moderately concentrated micellar aqueous solution and in a reversed micellar solution of sodium octanoate in decanol containing solubilized water is ca 1.8 kJ mole/sup -1/. These results are in agreement with the hypothesis that the electric contributions to the energy of the interfaces are decisive for the formation of different aggregates. Accordingly, the equilibrium between 2 different aggregates should be characterized by an equal number of ionized groups per unit area of the micellar surfaces and equal effects of counterions. 22 references.

  20. Microregion detection of ionic liquid microemulsions.

    PubMed

    Gao, Yanan; Wang, Suqing; Zheng, Liqiang; Han, Shuaibing; Zhang, Xuan; Lu, Deming; Yu, Li; Ji, Yongqiang; Zhang, Gaoyong

    2006-09-15

    Nonaqueous ionic liquid (IL) microemulsion consisting of IL, 1-butyl-3-methylimidazolium tetrafluoroborate (bmimBF(4)), surfactant TX-100, and toluene was prepared and the phase behavior of the ternary system was investigated. Electrical conductivity measurement was used for investigating the microregions of the nonaqueous IL microemulsions. On the basis of the percolation theory, the bmimBF(4)-in-toluene (IL/O), bicontinuous, and toluene-in-bmimBF(4) (O/IL) microregions of the microemulsions were successfully identified using insulative toluene as the titration phase. However, this method was invalid when conductive bmimBF(4) acted as the titration phase. The microregions obtained by conductivity measurements were further proved by electrochemical cyclic voltammetry experiments. The results indicated that the conductivity method was feasible for identifying microstructures of the nonaqueous IL microemulsions.

  1. FT-IR Spectroscopic Evidence Of Phase Transition For NaA-ROH-Kerosine-H2O Microemulsion System Containing Nd3+ Ions

    NASA Astrophysics Data System (ADS)

    Liao, Hua; Xu, Zhen-Hua; Shi, Nai; Wu, Jin-Guang; Xu, Guang-Xian

    1989-12-01

    In the previous investigation, the saponification of naphthenic acid extractant system has been proved to be a process of the formation of a microemulsion of 14/0 type, and its full extraction of rare earths is a process of destruction of the W/O microemulsion[1]. When NdCl3 is partially extracted with NaA (sodium naphthenate) secoctylalcohol-- kerosine-- water microemulsion system (ME), both the NdA3 and the NaA co-exist in the same organic phase. However,the formation mechanism of microemulsion containing neodymium has not been much studied. In this paper, 10 aliquots of fully saponificated extractants were equilibrated with various amounts of NdC13 solutions respectively, then ten organic phases with different extraction efficiencies of neodymium from 094 to 9094 were obtained. After extraction,the volume of neodymium containing organic phase increased by 5 to 4594, because of the transfer of water molecules. The appearance of these organic phase still remained clear and transparent. The average hydrodynamic radius of the drops were found to be 100-300 Angstrom by using light scattering techniques. The results give a direct evidence of the microemulsion formation in the organic phase. Their FT-IR spectra were measured with CaFa liquid cells utilizing a Nicolet 7199B FT-IR spectrometer. The presence of various amounts of water in the organic phases was clearly detected from the relative intensity changes of 1644 cm-I, which is assigned to the bending mode of 1110 molecules. Fig.1 shows the change of water contents to the percent extraction of neodymium. Comparsion with the FT-IR spectra, it is seen that the 1560 cm-1 peak of the full saponificated extractant is attributed to the asym. stretching vibration of COO''' group, it shifted to 1536 for 100% extration of Nd ions, indicating the formation of neodymium naphthenate (NdA ) from ionic sodium naphthenate. The sym. strethching vibration of COO''' located at 1406 cm-1, it shifted to 1408 cm in 45% Nd extration

  2. Polymeric bicontinuous microemulsions

    NASA Astrophysics Data System (ADS)

    Krishnan, Kasiraman

    Rheology of complex fluids has been a topic of considerable interest recently. Bicontinuous microemulsions (BmuE), made by mixing appropriate amounts of oil, water and a surfactant, form a unique class of complex fluids. They possess a characteristic nanostructure consisting of undulating surfaces with vanishingly small interfacial curvature. BmuEs can also be generated in polymers by mixing appropriate amounts of two homopolymers and their corresponding diblock copolymer. The main objective of the present research is to study effects of shear on a model polymeric BmuE. Scattering is used as a predominant tool with in situ flow devices, along with optical microscopy and rheology. The model BmuE consists of a ternary blend of poly(ethyl ethylene) (PEE), poly(dimethyl siloxane) (PDMS) and a PEE-PDMS diblock copolymer. Steady shear experiments reveal four regimes as a function of shear rate. At low shear rates (regime I), Newtonian behavior is observed; there is onset of shear thinning at higher rates (regime II). In regime III, the stress is independent of shear rate, whereas it increases with shear rate once again in regime IV. Morphological characterization was carried out for each of these four regimes using scattering and microscopy, the key result being the evidence for flow-induced phase separation in regime III. Transient rheological measurements were conducted for startup and step changes in shear rate, and the BmuE exhibits features similar to worm-like micellar colloidal systems. Time-resolved light scattering and microscopy also reveal interesting characteristics. Dynamic mechanical spectroscopy indicates similarities with neat block copolymers near the order-disorder transition. The equilibrium rheological behavior is intriguing and detailed comparisons are made with Landau-Ginzburg theoretical models. Other areas of research as a part of this thesis include study of structural dynamics of BmuEs with dynamic light scattering, and the rheological

  3. Paliperidone microemulsion for nose-to-brain targeted drug delivery system: pharmacodynamic and pharmacokinetic evaluation.

    PubMed

    Patel, Mrunali R; Patel, Rashmin B; Bhatt, Kashyap K; Patel, Bharat G; Gaikwad, Rajiv V

    2016-01-01

    The objective of present study was to develop and evaluate paliperidone (PALI) loaded microemulsion (PALI-ME) for intranasal delivery in the treatment of schizophrenia. The PALI-ME was formulated by the spontaneous microemulsification method and characterized for physicochemical parameters. Pharmacodynamic assessments (apomorphine-induced compulsive behavior and spontaneous motor activity) were performed using mice. All formulations were tagged with (99m)Tc (technetium). Pharmacokinetic evaluation of PALI in the brain was investigated using Swiss albino rats. Brain scintigraphy imaging was performed in rabbits. PALI-ME was found stable with average droplet size of 20.01 ± 1.28 nm. In pharmacodynamic studies, significant (p < 0.05) deference in parameters estimated, were found between the treated and control groups. (99m)Tc-tagged PALI solution (PALI-SOL)/PALI-ME/PALI muco-adhesive ME (PALI-MME) was found to be stable and suitable for in vivo studies. Brain-to-blood ratio at all sampling points up to 8 h following intranasal administration of PALI-MME compared to intravenous PALI-ME was found to be 6-8 times higher signifying greater extent of distribution of the PALI in brain. Rabbit brain scintigraphy demonstrated higher intranasal uptake of the PALI into the brain. This investigation demonstrates a prompt and larger extent of transport of PALI into the brain through intranasal PALI-MME, which may prove beneficial for treatment of schizophrenia.

  4. Microemulsion utility in pharmaceuticals: Implications for multi-drug delivery.

    PubMed

    Callender, Shannon P; Mathews, Jessica A; Kobernyk, Katherine; Wettig, Shawn D

    2017-06-30

    Emulsion technology has been utilized extensively in the pharmaceutical industry. This article presents a comprehensive review of the literature on an important subcategory of emulsions, microemulsions. Microemulsions are optically transparent, thermodynamically stable colloidal systems, 10-100nm diameter, that form spontaneously upon mixing of oil, water and emulsifier. This review is the first to address advantages and disadvantages, as well as considerations and challenges in multi-drug delivery. For the period 1 January 2011-30 April 2016, 431 publications related to microemulsion drug delivery were identified and screened according to microemulsion, drug classification, and surfactant types. Results indicate the use of microemulsions predominantly in lipophilic drug delivery (79.4%) via oil-in-water microemulsions and non-ionic surfactants (90%) for oral or topical administration. Cancer is the disease state most targeted followed by inflammatory diseases, microbial infections and cardiovascular disease. Key generalizations from this analysis include: 1) microemulsion formulation is largely based on trial-and-error despite over 1200 publications related to microemulsion drug delivery since their discovery in 1943; 2) characterization using methods including interfacial tension, droplet size, electrical conductivity, turbidity and viscosity may provide additional information for greater predictability; 3) microemulsion drug delivery publications arise primarily from China (27%) and India (21%) suggesting additional research opportunities elsewhere. Copyright © 2017 Elsevier B.V. All rights reserved.

  5. Development and in vivo evaluation of self-microemulsion as delivery system for α-mangostin.

    PubMed

    Xu, Wen-Ke; Jiang, Hui; Yang, Kui; Wang, Ya-Qin; Zhang, Qian; Zuo, Jian

    2017-03-01

    α-Mangostin (MG) is a versatile bioactive compound isolated from mangosteen and possesses significant pharmacokinetic shortages. To augment the potential clinical efficacy, MG-loaded self-microemulsion (MG-SME) was designed and prepared in this study, and its potential as a drug loading system was evaluated based on the pharmacokinetic performance and tissue distribution feature. The formula of MG-SME was optimized by an orthogonal test under the guidance of ternary phase diagram, and the prepared MG-SME was characterized by encapsulation efficiency, size distribution, and morphology. Optimized high performance liquid chromatography method was employed to determine concentrations of MG and characterize the pharmacokinetic and tissue distribution features of MG in rodents. It was found that diluted MG-SME was characterized as spherical particles with a mean diameter of 24.6 nm and an encapsulation efficiency of 87.26%. The delivery system enhanced the area under the curve of MG by 4.75 times and increased the distribution in lymphatic organs. These findings suggested that SME as a nano-sized delivery system efficiently promoted the digestive tract absorption of MG and modified its distribution in tissues. The targeting feature and high oral bioavailability of MG-SME promised a good clinical efficacy, especially for immune diseases.

  6. Electrocatalysis with vitamin B sub 12 in water-in-oil microemulsions at carbon-fiber microelectrodes

    SciTech Connect

    Owlia, A.

    1989-01-01

    Microemulsions are clear, thermodynamically stable dispersions containing oil, surfactant and water. They are crude models of biological membranes and can be used to investigate some of the organizational influence of membranes in lipid and protein synthesis, energy transduction, ion and group transport, etc. This thesis concerns the investigation of microemulsion properties as media in which catalytic reduction of vicinal dibromides can take place with the electrochemically generated Co(I) form of Vitamin B{sub 12}. Methods to study fundamental properties of resistive w/o AOT/H{sub 2}O/isoctane were developed. Microelectrodes of approximate radius of 6 {mu}m were prepared and characterized. Nonlinear regression was applied to the analysis of steady state voltammograms obtained at carbon-fiber microelectrodes. Reversible regression models were used to analyze data for oxidation of ferrocene in acetonitrile with and without added electrolyte. An estimate of cell resistance in highly resistive media was obtained by including ohmic drop in the model for reversible electron transfer. The electrocatalytic reduction of 1,2-dibromoethane (EDB), 1,2-dibromobutane (DBB), and trans-1,2-dibromocyclohexane (DBCH) with Vitamin B{sub 12} in pH {le} 3 water MeCN and w/o microemulsions of AOT/H{sub 2}O/isoctane at carbon fiber microelectrode was investigated. The microviscosity of w/o microemulsions were estimated from the Stokes-Einstein equation using ferrocene as a probe. Results show that the diffusion of molecules in the microemulsions are similar to their diffusion in organic phase (isoctane). Nonlinear regression analysis of the data for AOT w/o microemulsions describing the dependence of D{prime} on C{sub x} enables an estimate of micelle diffusion coefficients.

  7. Pressure effects on bending elasticities of surfactant monolayers in a ternary microemulsion composed of aerosol-OT /D2O/decane

    NASA Astrophysics Data System (ADS)

    Kawabata, Youhei; Seto, Hideki; Nagao, Michihiro; Takeda, Takayoshi

    2007-07-01

    Pressure effects on the bending elasticities of surfactant monolayers have been investigated in a microemulsion system composed of aerosol-OT (AOT), D2O, and deuterated decane by means of small angle neutron scattering, neutron spin echo (NSE), and dynamic light scattering (DLS). In this system, a water-in-oil droplet structure, at ambient temperature and pressure, decomposes into two phases, under both increasing temperature and pressure. The authors' previous study showed that the bending modulus κ of monolayers slightly decreased with increasing temperature, while it increased with increasing pressure. Temperature and pressure dependencies of κ were explained in terms of a microscopic model, which takes into account the interactions between surfactant molecules. In this paper, the authors present the temperature and pressure dependencies of κ obtained by the analysis combined with DLS and NSE experiments. The values of the bending modulus and mean displacement of the second-order droplet deformation are reasonable. It was further confirmed that an increase in the attractive interaction between hydrocarbon tails of AOT molecules with increasing pressure could be the origin of the pressure-induced phase transition.

  8. Ethylammonium nitrate in high temperature stable microemulsions.

    PubMed

    Zech, Oliver; Thomaier, Stefan; Kolodziejski, Agnes; Touraud, Didier; Grillo, Isabelle; Kunz, Werner

    2010-07-15

    The increasing number of publications reflects the still growing interest in nonaqueous microemulsions containing room-temperature ionic liquids. Recently, we characterized microemulsions composed of the room-temperature ionic liquid ethylammonium nitrate (EAN) as polar phase, dodecane as continuous phase and 1-hexadecyl-3-methyl imidazolium chloride ([C(16)mim][Cl]), an IL that exhibits surfactant properties, and decanol as cosurfactant at ambient temperature. We demonstrate here the high thermal stability of these microemulsions. Along an experimental path, no phase change could be observed visually within a temperature range between 30 degrees C and 150 degrees C. The microemulsions are characterized with quasi-elastic light scattering measurements at ambient temperature and temperature dependent small angle neutron scattering (SANS) experiments between 30 degrees C and 150 degrees C. DLS measurements at ambient temperature indicate a swelling of the formed structures with increasing amount of EAN up to a certain threshold. The SANS experiments were performed below this threshold. The data evaluation of such concentrated systems like microemulsions is possible with the "generalized indirect Fourier transformation" method (GIFT). We evaluated the small angle scattering data via the GIFT method, for comparison we also applied the model of Teubner and Strey (TS) which was often used to describe scattering curves of microemulsions. The GIFT method gives good fits throughout the experimental path, while the TS model gives relatively poor fits. Both, light scattering and SANS results are in agreement with the existence of EAN droplets stabilized by surfactant with dodecane as continuous phase along the whole investigated temperature range. Moreover, these results clearly demonstrate the possibility to formulate high temperature stable microemulsions with ionic liquids at ambient pressure. Copyright 2010 Elsevier Inc. All rights reserved.

  9. Overcoming the Cutaneous Barrier with Microemulsions

    PubMed Central

    Lopes, Luciana B.

    2014-01-01

    Microemulsions are fluid and isotropic formulations that have been widely studied as delivery systems for a variety of routes, including the skin. In spite of what the name suggests, microemulsions are nanocarriers, and their use as topical delivery systems derives from their multiple advantages compared to other dermatological formulations, such as ease of preparation, thermodynamic stability and penetration-enhancing properties. Composition, charge and internal structure have been reported as determinant factors for the modulation of drug release and cutaneous and transdermal transport. This manuscript aims at reviewing how these and other characteristics affect delivery and make microemulsions appealing for topical and transdermal administration, as well as how they can be modulated during the formulation design to improve the potential and efficacy of the final system. PMID:24590260

  10. Solvation dynamics of 4-(dicyanomethylene)-2-methyl-6-( p-dimethylaminostyryl)-4H-pyran (DCM) in a microemulsion

    NASA Astrophysics Data System (ADS)

    Pal, Samir Kumar; Mandal, Debabrata; Sukul, Dipankar; Bhattacharyya, Kankan

    1999-10-01

    The photophysical process of the laser dye 4-(dicyanomethylene)-2-methyl-6-( p-dimethylaminostyryl)-4H-pyran (DCM) is studied in aerosol-OT (AOT) microemulsions in n-heptane using picosecond spectroscopy. When AOT and water are added to a solution of DCM in n-heptane, some of the DCM molecules migrate from bulk n-heptane to the water pool. The absorption and emission peaks of the DCM molecules in the polar water pool are markedly red shifted from those in the bulk n-heptane and the emission intensity in the water pool is nearly 40 times higher. Dual emission is not observed in the microemulsions. DCM exhibits slow solvation dynamics in the water pool with an average solvation time of 1.23 ns.

  11. The novel formulation design of self-emulsifying drug delivery systems (SEDDS) type O/W microemulsion I: enhancing effects on oral bioavailability of poorly water soluble compounds in rats and beagle dogs.

    PubMed

    Araya, Hiroshi; Nagao, Shunsuke; Tomita, Mikio; Hayashi, Masahiro

    2005-08-01

    We examined the design of the versatile novel self-emulsifying drug delivery systems (SEDDS) type O/W microemulsion formulation which enhances the oral bioavailability by raising the solubility of poorly water soluble compounds. Namely, seven kinds of poorly water soluble compounds such as disopyramide, ibuprofen, ketoprofen, tolbutamide, and other new compounds, as the model compounds were used to compare the plasma concentration profile of the compound following single oral administration of each compound to rats and beagle dogs as a solution, an oily solution, a suspension (or a powder), an O/W microemulsion, and a SEDDS type O/W microemulsion. And the enhancing effect of the SEDDS type O/W microemulsion on the gastrointestinal absorption of these compounds was evaluated. In the components of the SEDDS type O/W microemulsion, medium chain fatty acid triglyceride (MCT), diglyceryl monooleate (DGMO-C), polyoxyethylene hydrogenated castor oil 40 (HCO-40), and ethanol were used as an oil, a lipophilic surfactant, a hydrophilic surfactant, and a solubilizer, at the mixture ratio of 25/5/45/25 (w/w%), respectively. Thereby, to six kinds of the model compounds except disopyramide, the solubility was from 340 to 98,000 times that in water, and the AUCs in plasma concentration of the compound were equivalent to that of solution or O/W microemulsion administration, or was increased by 1.5 to 78 times that of suspension administration. Accordingly, this novel SEDDS type O/W microemulsion is the versatile, useful formulation which enhances the oral bioavailability by raising the solubility of poorly water soluble compounds.

  12. Polarity of the interface in ionic liquid in oil microemulsions.

    PubMed

    Andújar-Matalobos, María; García-Río, Luis; López-García, Susana; Rodríguez-Dafonte, Pedro

    2011-11-01

    Ionic liquid based microemulsions were characterized by absorption solvatochromic shifts, (1)H NMR and kinetic measurements in order to investigate the properties of the ionic liquid within the restricted geometry provided by microemulsions and the interactions of the ionic liquid with the interface. Experimental results show a significant difference between the interfaces of normal water and the new ionic liquid microemulsions. Absorption solvatochromic shift experiments and kinetic studies on the aminolysis of 4-nitrophenyl laurate by n-decylamine show that the polarity at the interface of the ionic liquid in oil microemulsions (IL/O) is higher than at the interface of water in oil microemulsions (W/O) despite the fact that the polarity of [bmim][BF(4)(-)] is lower than the polarity of water. (1)H NMR experiments showed that an increase in the ionic liquid content of the microemulsion led to an increase in the interaction between [bmim][BF(4)(-)] and TX-100. The reason for the higher polarity of the microemulsions with the ionic liquid can be explained in terms of the incorporation of higher levels of the ionic liquid at the interface of the microemulsions, as compared to water in the traditional systems. Copyright © 2011 Elsevier Inc. All rights reserved.

  13. Natural microemulsions: formulation design and skin interaction.

    PubMed

    Schwarz, Julia C; Klang, Victoria; Hoppel, Magdalena; Mahrhauser, Denise; Valenta, Claudia

    2012-08-01

    Microemulsions are thermodynamically stable, colloidal drug delivery systems. This study presents the first substantiated comparison of natural, skin-compatible and biodegradable surfactants in terms of their suitability to form isotropic microemulsions and their skin interaction. Pseudoternery phase diagrams were constructed for lecithin, sucrose laurate and alkylpolyglycoside as single surfactants. Moreover, also mixed surfactant films of lecithin and alkylpolyglycoside as well as lecithin and sucrose laurate were tested. Large isotropic areas could be identified for lecithin, sucrose laurate and lecithin-sucrose laurate. One defined composition was chosen from the pseudoternery phase diagram, prepared with all investigated surfactants and 1:1 surfactant mixtures, respectively, and analysed for their effect on the stratum corneum on a molecular level by ATR-FTIR. Significantly higher frequency values of the symmetric and asymmetric CH(2)-stretching bands compared to the control were recorded for all microemulsions, indicating a hexagonal arrangement of the lipid chains. A similar trend was observed for the lateral packing of the alkyl chains as suggested by the shift of the CH(2)-scissoring bands. Moreover, diffusion cell experiments using porcine skin were performed with the two model drugs flufenamic acid and fluconazole. In both cases, the lecithin-based microemulsions showed the highest permeation rates followed by the alkylpolyglycoside-lecithin microemulsions.

  14. Magnetic microemulsions based on magnetic ionic liquids.

    PubMed

    Klee, Andreas; Prevost, Sylvain; Kunz, Werner; Schweins, Ralf; Kiefer, Klaus; Gradzielski, Michael

    2012-11-28

    Microemulsions with magnetic properties were formed by employing a magnetic room temperature ionic liquid (MRTIL) as polar phase, cyclohexane as oil, and an appropriate mixture of ionic surfactant and decanol as a cosurfactant. By means of small-angle neutron scattering (SANS) and electric conductivity the microemulsion structure could be confirmed, where the classical structural sequence of oil-continuous-bicontinuous-polar phase continuous is observed with increasing ratio [polar phase]/[oil]. Accordingly a maximum of the structural size is observed at about equal volumes of oil and MRTIL contained. Therefore this system is structurally the same as normal microemulsions but with the magnetic properties added to it by the incorporation into the systems formulation.

  15. Development of clinical dosage forms for a poorly water-soluble drug II: formulation and characterization of a novel solid microemulsion preconcentrate system for oral delivery of a poorly water-soluble drug.

    PubMed

    Li, Ping; Hynes, Sara R; Haefele, Thomas F; Pudipeddi, Madhu; Royce, Alan E; Serajuddin, Abu T M

    2009-05-01

    The solution of a poorly water-soluble drug in a liquid lipid-surfactant mixture, which served as a microemulsion preconcentrate, was converted into a solid form by incorporating it in a solid polyethylene glycol (PEG) matrix. The solid microemulsion preconcentrates thus formed consisted of Capmul PG8 (propylene glycol monocaprylate) as oil, Cremophor EL (polyoxyl 35 castor oil) as surfactant, and hydrophilic polymer PEG 3350 as solid matrix. The drug (aqueous solubility: 0.17 microg/mL at pH 1-8 and 25 degrees C) was dissolved in a melt of the mixture at 65-70 degrees C and then the hot solution was filled into hard gelatin capsules; the liquid gradually solidified upon cooling below 55 degrees C. The solid system was characterized by differential scanning calorimetry (DSC), scanning electron microscopy (SEM), confocal Raman microscopy (CRM), and the dispersion testing in water. It was confirmed that a solid microemulsion preconcentrate is a two-phase system, where clusters of crystalline PEG 3350 formed the solid structure (m.p. 55-60 degrees C) and the liquid microemulsion preconcentrate dispersed in between PEG 3350 crystals as a separate phase. The drug remained dissolved in the liquid phase. In vitro release testing showed that the preconcentrate dispersed readily in water forming a microemulsion with the drug dissolved in the oil particles (<150 nm) and the presence of PEG 3350 did not interfere with the process of self-microemulsification.

  16. Structural and dynamical transformations between neighboring dense microemulsion phases

    NASA Astrophysics Data System (ADS)

    Kotlarchyk, M.; Sheu, E. Y.; Capel, M.

    1992-07-01

    A small-angle x-ray scattering (SAXS) study of dense AOT-water-decane microemulsions [AOT denotes sodium bis(2-ethylhexyl) sulfosuccinate] was undertaken in order to delineate clearly the phase behavior and corresponding structural transitions for AOT-plus-water volume fractions ranging from φ=0.60 to 0.95. Spectra were collected for temperatures between T=3 and 65 °C. The resulting T-vs-φ phase diagram indicates three distinct structural domains when the water-to-AOT molar ratio is fixed at W=40.8, namely, the previously investigated L2 droplet phase, a high-temperature Lα lamellar phase, and a low-temperature L3 phase consisting of randomly connected lamellar sheets. A significantly wide coexistence region accompanies the droplet-to-lamellar phase transition, which is demonstrated to be first order. For W between 15 and 40, an analysis of the lamellar structure using a one-dimensional paracrystal model produces a Hosemann g factor indicative of an approximately constant variation in the lamellar spacing of about 8%. The SAXS study was supplemented by dielectric-relaxation, shear-viscosity, and quasielastic light-scattering measurements in order to substantiate the observed phase transitions and further our understanding of the structural and dynamical properties of the L3 phase. It was found that the L3 phase exhibits Newtonian behavior up to a shear rate of 790 s-1, in contradiction to previous theoretical considerations. The phase exhibits two distinct relaxation modes. A relaxation time of ~1 ms characterizes the Brownian motion of a single lamellar sheet, while the motion of the entire interconnected sheet assembly has a relaxation time on the order of 1 s.

  17. Synthesis of tin monosulfide (SnS) nanoparticles using surfactant free microemulsion (SFME) with the single microemulsion scheme

    NASA Astrophysics Data System (ADS)

    Tarkas, Hemant S.; Marathe, Deepak M.; Mahajan, Mrunal S.; Muntaser, Faisal; Patil, Mahendra B.; Tak, Swapnil R.; Sali, Jaydeep V.

    2017-02-01

    Synthesis of monomorphic, SnS nanoparticles without using a capping agent is a difficult task with chemical route of synthesis. This paper reports on synthesis of tin monosulfide (SnS) nanopartilces with dimension in the quantum-dot regime using surfactant free microemulsion with single microemulsion scheme. This has been achieved by reaction in microreactors in the CME (C: chlorobenzene, M: methanol and E: ethylene glycol) microemulsion system. This is an easy and controllable chemical route for synthesis of SnS nanoparticles. Nanoparticle diameter showed prominent dependence on microemulsion concentration and marginal dependence on microemulsion temperature in the temperature range studied. The SnS nanoparticles formed with this method form stable dispersion in Tolune.

  18. Reactivity of hair cystine in microemulsion media.

    PubMed

    Erra, P; Solans, C; Azemar, N; Parra, J L; Touraud, D; Clausse, M

    1990-04-01

    Synopsis Reduction of keratin cystine by thioglycolic acid incorporated in microemulsions of the water/sodium dodecilsulphate/n-pentanol/n-dodecane system has been determined. The results obtained have been interpreted in relation to the properties of the reaction media. Microemulsions with constant oil-to-surface active mixture weight ratios (R(o/s)) and different concentrations of water were chosen as reaction media. At low water concentrations a steep increase in reactivity with the increase of water was observed at all values of R(o/s). However it was more pronounced the higher the oil content. A relation between maximum cysteine formation and percolative behaviour of the microemulsion was found at high R(o/s) values.

  19. Crystallization from microemulsions ? a novel method for the preparation of new crystal forms of aspartame

    NASA Astrophysics Data System (ADS)

    Füredi-Milhofer, Helga; Garti, N.; Kamyshny, A.

    1999-03-01

    Solubilization and crystallization of the artificial sweetener aspartame (APM), in water/isooctane microemulsions stabilized with sodium diisooctyl sulfosuccinate (AOT) has been investigated. The amount of aspartame that could be solubilized depended primarily on the amount of surfactant and on the temperature. The maximum AOT/aspartame molar ratio at the w/o interface is shown to be 6.2 at 25°C. It was concluded that the dipeptide is located at the w/o interface interspersed between surfactant molecules and that it acts as a cosurfactant. A new crystal form, APM III, was obtained by cooling of hot w/isooctane/AOT microemulsions containing solubilized aspartame. The new crystal form exhibits a distinct X-ray diffraction powder pattern, as well as changes in the FTIR spectra, thermogravimetric and DSC patterns. H-NMR spectra of APM III dissolved in D 2O were identical to the spectrum of commercial aspartame recorded under the same conditions. The new crystal form has greatly improved dissolution kinetics.

  20. The effect of component of microemulsions on transdermal delivery of buspirone hydrochloride.

    PubMed

    Tsai, Yi-Hung; Chang, Jung Tzu; Chang, Jui-Sheng; Huang, Chi-Te; Huang, Yaw-Bin; Wu, Pao-Chu

    2011-06-01

    The aim of this study was to evaluate the influence of components such as type, level, and hydrophilic-lipophilic balance (HLB) value of surfactant, type and amount of cosurfactant, and drug concentration on the permeability of buspirone hydrochloride microemulsions through rat skin. The cumulative amount at 24 h ranged from 502.2 ± 57.8 to 1754.3 ± 616.6 μg/cm(2), flux ranged from 23.03 ± 1.84 to 83.36 ± 25.08 μg/(cm(2)/h), and lag time ranged from 3.0 to 4.7 h, indicating that the permeation parameters of buspirone from microemulsions were markedly influenced by the composition of microemulsions. In comparison with the effect of composition of microemulsions on the buspirone permeation capacity, it was found that microemulsions containing surfactant with HLB value of 11.16 possessed higher flux. The viscosity of microemulsions increased, flux decreased, and lag time was prolonged when amount of surfactant in microemulsions increased. The various cosurfactants can also influence the microemulsion formation and drug permeability. The microemulsion with ethanol as cosurfactant had higher permeation rate. However, the buspirone microemulsion with higher flux can provide the therapeutic minimum effective concentration, at workable administrated area about 3.3-5.8 cm(2), demonstrating microemulsions could be a promising drug carrier for transdermal delivery systems. Copyright © 2011 Wiley-Liss, Inc.

  1. Transdermal delivery of curcumin via microemulsion.

    PubMed

    Sintov, Amnon C

    2015-03-15

    The objective of this study was to evaluate the transdermal delivery potential of a new curcumin-containing microemulsion system. Three series of experiments were carried out to comprehend the system characteristics: (a) examining the influence of water content on curcumin permeation, (b) studying the effect of curcumin loading on its permeability, and (c) assessing the contribution of the vesicular nature of the microemulsion on permeability. The skin permeability of curcumin from microemulsions, which contained 5%, 10%, and 20% of water content (1% curcumin), was measured in vitro using excised rat skin. It has been shown that the permeability coefficient of CUR in a formulation containing 10% aqueous phase (ME-10) was twofold higher than the values obtained for formulations with 5% and 20% water (Papp=0.116 × 10(-3)± 0.052 × 10(-3)vs. 0.043 × 10(-3)± 0.022 × 10(-3) and 0.047 × 10(-3)± 0.025 × 10(-3)cm/h, respectively. A reasonable explanation for this phenomenon may be the reduction of both droplet size and droplets' concentration in the microemulsion as the aqueous phase decreased from 20% to 5%. It has also been shown that a linear correlation exists between the decrease in droplet size and the increase of curcumin loading in the microemulsion. In addition, it has been demonstrated that a micellar system, S/O-mix, and a plain solution of curcumin resulted in a significantly lower curcumin permeation relative to that presented by the microemulsion, Papp=0.018 × 10(-3)± 0.011 × 10(-3), 0.005 × 10(-3)± 0.002 × 10(-3), and 0.002 × 10(-3)± 0.000 × 10(-3)cm/h, respectively, vs. 0.110 × 10(-3)± 0.021 × 10(-3)cm/h for the microemulsion. The enhancement ratio (ER=Jss-ME/Jss-solution) of CUR permeated via 1% loaded microemulsion was 55.

  2. Pain on injection with microemulsion propofol

    PubMed Central

    Sim, Ji-Yeon; Lee, Soo-Han; Park, Do-Yang; Jung, Jin-Ah; Ki, Kyoung-Ho; Lee, Dong-Ho; Noh, Gyu-Jeong

    2009-01-01

    AIMS To evaluate the incidence and severity of injection pain caused by microemulsion propofol and lipid emulsion propofol in relation to plasma bradykinin generation and aqueous free propofol concentrations. METHODS Injection pain was evaluated in 147 patients. Aqueous free propofol concentrations in each formulation, and in formulation mixtures containing agents that reduce propofol-induced pain, were measured by high-performance liquid chromatography. Plasma bradykinin concentrations in both formulations and in their components mixed with blood sampled from six volunteers were measured by radioimmunoassays. Injection pain caused by 8% polyethylene glycol 660 hydroxystearate (PEG660 HS) was evaluated in another 10 volunteers. RESULTS The incidence of injection pain [visual analogue scale (VAS) >30 mm] caused by microemulsion and lipid emulsion propofol was 69.7 and 42.3% (P < 0.001), respectively. The median VAS scores for microemulsion and lipid emulsion propofol were 59 and 24 mm, respectively (95% confidence interval for the difference 12.5, 40.0). The aqueous free propofol concentration of microemulsion propofol was seven times higher than that of lipid emulsion propofol. Agents that reduce injection pain did not affect aqueous free propofol concentrations. Microemulsion propofol and 8% PEG660 HS enhanced plasma bradykinin generation, whereas lipid emulsion propofol and lipid solvent did not. PEG660 HS did not cause injection pain. CONCLUSIONS Higher aqueous free propofol concentrations of microemulsion propofol produce more frequent and severe pain. The plasma kallikrein–kinin system may not be involved, and the agents that reduce injection pain may not act by decreasing aqueous free propofol concentrations. PMID:19220277

  3. Parenteral microemulsions: an overview.

    PubMed

    Date, Abhijit A; Nagarsenker, M S

    2008-05-01

    Parenteral delivery of the hydrophobic drugs is a very challenging task. The conventional approaches such as use of co-solvents, oily vehicles and modern approaches such as mixed micelles, liposomes, complexation with cyclodextrins and emulsions have several limitations. Microemulsions have evolved as a novel vehicle for parenteral delivery of the hydrophobic drugs. Their interesting features such as spontaneity of formation, ease of manufacture, high solubilization capacity and self-preserving property make them the vehicle of choice. The review focuses on the excipients available for formulation of the parenteral microemulsions and describes the investigations reported for the various classes of therapeutic agents.

  4. Dendrimer-templated Pd nanoparticles and Pd nanoparticles synthesized by reverse microemulsions as efficient nanocatalysts for the Heck reaction: A comparative study.

    PubMed

    Noh, Ji-Hyang; Meijboom, Reinout

    2014-02-01

    Palladium nanoparticles (NPs) were prepared using a dendrimer-templated method using G4, G5 and G6 PAMAM-OH dendrimers as well as a reverse microemulsion method using the water/dioctyl sulfosuccinate sodium salt (aerosol-OT, AOT) surfactant/isooctane system with water to surfactant ratios (ω0) of 5, 10 and 13. These 6 catalysts were characterized by UV-Vis spectroscopy, TEM, EDX, and XRD. TEM micrographs showed that the average sizes of 2.74-3.32nm with narrower size distribution were achieved by using dendrimer-templated synthetic methods, whereas the reverse microemulsion method resulted in broad size distribution with an average size of 3.87-5.06nm. The influence of various reaction parameters such as base, catalyst dosing, alkene, aryl halide and temperature on the Heck C-C coupling reaction was evaluated. The activation parameters were derived from the reaction rate of each catalyst obtained at various temperatures. A correlation of catalytic activity, enthalpy of activation and particle size is discussed. Particle size changes of each catalyst were investigated after the catalytic reaction. Overall results indicated that dendrimer-templated Pd NP catalysts showed superior activity as compared to the Pd NPs synthesized by reverse microemulsions, with the dendrimer-templated G5-OH(Pd80) showing the best activity. These catalysts were also reusable for 3 cycles, retaining high yield and showing excellent yields under mild conditions. Therefore, the dendrimer-templated Pd NPs are efficient catalyst systems for the ligand-free Heck C-C coupling reaction.

  5. Pressure-induced hexagonal phase in a ternary microemulsion system composed of a nonionic surfactant, water, and oil

    NASA Astrophysics Data System (ADS)

    Nagao, Michihiro; Seto, Hideki; Ihara, Daisuke; Shibayama, Mitsuhiro; Takeda, Takayoshi

    2005-08-01

    The pressure-induced phase transition in a microemulsion, consisting of pentaethylene glycol mono-n-dodecyl ether, water, and n-octane, was investigated by means of small-angle neutron scattering. A pressure-induced phase transition from a lamellar structure to a hexagonal structure was observed. The temperature-pressure phase boundary shows a positive slope with dT /dP˜0.09K/MPa. The structure unit of the high-pressure hexagonal phase was an oil-in-water cylinder with the membrane thickness of 15.5 Å, identical to the low-temperature hexagonal phase. Pressurizing was found to have the same effect by decreasing temperature. This behavior was satisfactorily explained with the pressure dependence of the spontaneous curvature of surfactant membranes. That is, the volume change of surfactant tails plays a dominant role in the structure change of the microemulsion with applying pressure.

  6. Analysis of the phase diagram and microstructural transitions in phospholipid microemulsion systems using high-resolution ultrasonic spectroscopy.

    PubMed

    Hickey, Sinead; Lawrence, M Jayne; Hagan, Sue A; Buckin, Vitaly

    2006-06-20

    In the present work, high-resolution ultrasonic spectroscopy was applied to analyze a pseudoternary phase diagram for mixtures consisting of water/isopropyl myristate/Epikuron 200 and a cosurfactant (n-propanol). Changes in the ultrasonic velocity and attenuation in the megahertz frequency range were measured in the course of titration of the oil/surfactant/cosurfactant mixture with water at 25 degrees C. The ultrasonic titration profiles showed several phase transitions in the samples, which allowed the construction of an "ultrasonic" phase diagram. Quantitative analysis of the ultrasonic parameters enabled the characterization of various phases (swollen micelles, microemulsion, coarse emulsion, and pseudo-bicontinuous) as well as the evaluation of the state of the water and the particle size. The particle size obtained for the microemulsion region ranged from 5 to 14 nm over the measured concentrations of water/isopropyl myristate/Epikuron 200 and n-propanol, which agreed well with the previous literature data.

  7. Formulation and evaluation of microemulsion-based hydrogel for topical delivery

    PubMed Central

    Sabale, Vidya; Vora, Sejal

    2012-01-01

    Background: The purpose of this study was to develop microemulsion-based hydrogel formulation for topical delivery of bifonazole with an objective to increase the solubility and skin permeability of the drug. Materials and Methods: Oleic acid was screened as the oil phase of microemulsions, due to a good solubilizing capacity of the microemulison systems. The pseudo-ternary phase diagrams for microemulsion regions were constructed using oleic acid as the oil, Tween 80 as the surfactant and isopropyl alcohol (IPA) as the cosurfactant. Various microemulsion formulations were prepared and optimized by 32 factorial design on the basis of percentage (%) transmittance, globule size, zeta potential, drug release, and skin permeability. The abilities of various microemulsions to deliver bifonazole through the skin were evaluated ex vivo using Franz diffusion cells fitted with rat skins. The Hydroxy Propyl Methyl Cellulose (HPMC) K100 M as a gel matrix was used to construct the microemulsion-based hydrogel for improving the viscosity of microemulsion for topical administration. The optimized microemulsion-based hydrogel was evaluated for viscosity, spreadability, skin irritancy, skin permeability, stability, and antifungal activity by comparing it with marketed bifonazole cream. Results: The mechanism of drug release from microemulsion-based hydrogel was observed to follow zero order kinetics. The studied optimized microemulsion-based hydrogel showed a good stability over the period of 3 months. Average globule size of optimized microemulsion (F5) was found to be 18.98 nm, zeta potential was found to be -5.56 mv, and permeability of drug from microemulsion within 8 h was observed 84%. The antifungal activity of microemulsion-based hydrogel was found to be comparable with marketed cream. Conclusion: The results indicate that the studied microemulsion-based hydrogel (F5) has a potential for sustained action of drug release and it may act as promising vehicle for topical

  8. Interaction between morin and AOT reversed micelles--studies with UV-vis at 25 °C.

    PubMed

    Bhattarai, Ajaya; Wilczura-Wachnik, H

    2014-01-30

    The precise measurements of morin absorbance in presence of surfactant/solvent/water systems at 25 °C by UV-vis technique are reported. The surfactant used in presented study was sodium bis(2-ethylhexyl) sulfosuccinate called Aerosol-OT or AOT. The solvents selected were: ethanol, ethylene glycol, and n-decanol. The concentrations of AOT were varied between 0.001 and 0.4 mol/kg. Morin concentration in quvette during UV-vis registration was not equals in all solvent because of its different solubility and absorption intensity depending on the solvent. Water concentration in the studied systems was defined by R parameter according to relation: R=[H2O]/[AOT] and was equal 0, 30 and 40 in ethanol; 0, 10, 20 and 30 in ethylene glycol and 0, 10, 20, 30, and 40 in n-decanol. In presented work a Nernstian distribution of morin between the organic and micellar phases was assumed. The intensity of morin absorbance as a function of AOT concentration was analyzed. Using Non-linear Regression Procedure (NLREG) morin binding constant (K' [mol/kg]), and morin distribution constant (K) between organic phase and AOT micellar phase have been calculated. The experimental results have shown a significant influence of solvent, surfactant and water presence on morin UV-vis spectrum. Calculated data pointed out on different transfer of morin molecules from the organic to micellar phase depending on the solvent. Moreover, results of calculations indicate on competition between morin and water molecules interacting with AOT polar heads. Morin molecules privileged location in AOT reversed micelles strongly depends on the solvent. In case of systems with ethylene glycol as solvent is possible morin molecules location in polar cores of AOT reversed micelles as results of strong interaction between AOT polar heads and morin hydroxyl groups, whereas in case of ethanol and n-decanol morin molecules are located in palisade layer. Copyright © 2013 Elsevier B.V. All rights reserved.

  9. Microemulsions as reaction media for the synthesis of mixed oxide nanoparticles: relationships between microemulsion structure, reactivity, and nanoparticle characteristics.

    PubMed

    Aubery, Carolina; Solans, Conxita; Prevost, Sylvain; Gradzielski, Michael; Sanchez-Dominguez, Margarita

    2013-02-12

    Phase behavior, dynamics, and structure of W/O microemulsions of the system aqueous solution/Synperonic 13_6.5/1-hexanol/isooctane were studied, with the goal of determining their effect on Mn-Zn ferrite nanoparticle formation, kinetics and characteristics. Microemulsion structure and dynamics were studied systematically by conductivity, dynamic light scattering (DLS), differential scanning calorimetry (DSC), and small-angle neutron scattering (SANS). The main effect of cosurfactant 1-hexanol was a decrease in microemulsion regions as compared to the systems without cosurfactant; nevertheless, overlap of microemulsion regions in the systems with precursor salts (PS) and precipitating agent (PA) was achieved at lower S/O ratios, compared to the system without cosurfactant. At 50 °C, PA microemulsions are nonpercolated, while PS microemulsions are percolated. SANS indicates small prolate ellipsoidal micelles with the absence of free water up to 18 wt % PS solution; DSC studies confirm the absence of free water in this composition range. Kinetic studies show an increase in the reaction rate with increasing concentration of the aqueous solution; but the most significant effect in reaction kinetics was noted when cosurfactant was used, regardless of microemulsion dynamics and structure. On the other hand, the main difference regarding the characteristics of the obtained nanoparticles was observed when bicontinuous microemulsions were used as reaction media which resulted in 8 nm nanoparticles, versus a constant size of ~4 nm obtained with all other microemulsions regardless of aqueous solution content, dynamics, and presence or absence of cosurfactant. The latter effect of constant size is attributed to the fact that the water present is dominantly bound to the EO units of the surfactant.

  10. Evaluation of nicotinamide microemulsion on the skin penetration enhancement.

    PubMed

    Boonme, Prapaporn; Boonthongchuay, Chalida; Wongpoowarak, Wibul; Amnuaikit, Thanaporn

    2016-01-01

    This study purposed to evaluate a microemulsion containing nicotinamide for its characteristics, stability, and skin penetration and retention comparing with a solution of nicotinamide in 2:1 mixture of water and isopropyl alcohol (IPA). The microemulsion system was composed of 1:1 mixture of Span80 and Tween80 as a surfactant mixture, isopropyl palmitate (IPP) as an oil phase, and 2:1 mixture of water and IPA as an aqueous phase. Nicotinamide microemulsion was prepared by dissolving the active in the aqueous phase before simply mixing with the other components. It was determined for its characteristics and stability under various conditions. The skin penetration and retention studies of nicotinamide microemulsion and solution were performed by modified Franz diffusion cells, using newborn pig skin as the membrane. The results showed that nicotinamide microemulsion could be obtained as clear yellowish liquid, was water-in-oil (w/o) type, possessed Newtonian flow, and exhibited physicochemical stability when kept at 4 °C and room temperature (≈30 ± 2 °C) during 3 months. From the skin penetration data, the microemulsion could enhance the skin penetration of nicotinamide comparing with the solution. Additionally, nicotinamide microemulsion could provide much higher amount of skin retention than that of skin penetration, resulting in suitability for a cosmeceutical product.

  11. Deposition of metal nanoparticles on carbon nanotubes via hexane modified water-in-CO2 microemulsion at room temperature.

    PubMed

    Wang, Joanna Shaofen; Pan, Horng-Bin; Wai, Chien M

    2006-07-01

    Carbon nanotube-supported metallic nanoparticles (Pd, Rh, and bimetallic Pd-Rh) with diameters in the range 2-10 nm can be synthesized by hydrogen reduction of metal ions dissolved in the water core of a CO2 microemulsion in liquid CO2 at room temperature. The microemulsion is stabilized by sodium bis(2-ethylhexyl)sulfosuccinate (AOT) and dissolved in liquid CO2 with the aid of hexane as a modifier. The metal nanoparticles synthesized in the microemulsion can be deposited on surfaces of multi-walled carbon nanotubes (MWCNTs) by stirring in the liquid CO2 phase. This simple method produces uniformly distributed metal nanoparticles on surfaces of the MWCNTs with high yields. The carbon nanotube-supported Pd/Rh bimetallic nanoparticles exhibit high catalytic activities for hydrogenation of aromatic compounds and can be reused without losing catalytic activity.

  12. Microemulsions, micelles, and vesicles as media for membrane mimetic photochemistry

    SciTech Connect

    Fendler, J.H.

    1980-06-12

    Microemulsions, micelles, and vesicles are compared as media for membrane mimetic photochemistry. These systems solubilize, concentrate, compartmentalize, organize, and localize reactants; maintain proton and/or reactant gradients; alter quantum efficiencies; lower ionization potentials; change oxidation and reduction properties; change dissociation constants; affect vectorial electron displacements; alter photophysical pathways and rates; alter chemical pathways and rates; stabilize reactants, intermediates, and products; and separate products (charges). Formation of structures of microemulsions, micelles, and vesicles as well as substrate solubilization therein are summarized. Attention is focused on the utilization of microemulsions as reaction media. 72 references.

  13. Factors affecting the phase behavior and antimicrobial activity of carvacrol microemulsions.

    PubMed

    Shaaban, Hamdy A; Edris, Amr E

    2015-01-01

    The aim of this study was to investigate some factors that can contribute to the formulation of aqueous-based carvacrol microemulsion that can potentially be used in food preservation or disinfection. For this purpose the capacity of formation of carvacrol microemulsion was first revealed by studying the phase behavior of that compound in five different non-ionic microemulsion systems. Factors affecting that phase behavior like the type of non-ionic surfactant and presence of solubilization enhancers were also studied. The fully dilutable microemulsion system that can incorporate high carvacrol amount, as revealed from the phase diagrams, was chosen for the antibacterial evaluation study. The same microemulsion system was re-formulated in a cationic form by substituting the non-ionic surfactant, Tween 20 (T20) with the cationic cetylpyridinium chloride (CPC). The disc diffusion method was used to evaluate the activity of these microemulsion systems against different pathogenic bacteria. Results of the phase behavior study showed that carvacrol is a challenging phenolic compound which did not lend itself easily for solubilization in a fully dilutable non-ionic microemulsion. Incorporation of some solubilization enhancers like propylene glycol (PG) or short chain alcohols can fulfill this purpose however high surfactant/carvacrol ratio (9:1) was still required to solubilize only 1.0 wt% carvacrol in dilutable microemulsion. The antibacterial evaluation study at that concentration revealed that non-ionic carvacrol microemulsion formulated with T20 and a solubilization enhancer did not exhibit better antimicrobial activity than the same concentration of carvacrol formulated in surfactant-free aqueous solution composed of water/PG (1:1). On the other hand, the CPC-formulated carvacrol microemulsion showed significantly higher antibacterial activity than T20-formulated microemulsion. Results of the current investigation shed the light on the solubilization capacity and

  14. Chemical and Photochemical Reactivity in Microemulsions and Waterless Microemulsions

    DTIC Science & Technology

    1989-05-07

    compounds solubilized in microemulsions containing hydroperoxides, such as hydrogen peroxide and tert- butyl hydroperoxide or sodium perborate . We did...microemulsions based on cationic or anionic surfactants and containing hydrogen peroxide, tert-butyl hydroperoxide or perborate , and the study of the effect of...Microemulsions containing sodium perborate Sodium perborate is a cheap, non-toxic, large scale industrial chemical. It is a stable and easy to handle oxidant

  15. Development and characterization of eucalyptol microemulsions for topic delivery of curcumin.

    PubMed

    Liu, Chi-Hsien; Chang, Fu-Yen

    2011-01-01

    Microemulsions have received great attention for applications in transdermal drug delivery. The use of curcumin for treating various skin diseases like scleroderma, psoriasis, and skin cancer was extensively reported. The solubility of curcumin in various oils, surfactants, and cosurfactants was studied herein in order to find the optimal components for a transdermal delivery vehicle. Microemulsion systems composed of eucalyptol, polysorbate 80, ethanol, and water were developed as transdermal delivery vehicles for curcumin. Effects of the microemulsion composition on transdermal curcumin delivery were studied using Franz diffusion cells. The transdermal curcumin flux, permeability coefficient, and enhancement ratio were analyzed to evaluate the effects of eucalyptol/water ratios in the microemulsions. Pseudo-ternary phase diagrams of the eucalyptol microemulsions with various surfactant/cosurfactant ratios (1:1-1:3) were constructed to investigate their phase behaviors. Conductivity, interfacial tension, size, and viscosity data of the microemulsions were used to characterize the physicochemical properties of transdermal vehicles. The influence of the microemulsions on skin histology and on the delivery route was analyzed using hematoxylin/eosin staining and confocal laser scanning microscopy. In conclusion, microemulsions were successfully developed for transdermal curcumin delivery after screening various components and adjusting the oil/water ratios. The curcumin permeation rate of the microemulsion developed was 15.7-fold higher than that of the control (eucalyptol only). These results indicate that an eucalyptol microemulsion system is a promising tool for the percutaneous delivery of curcumin. © 2011 Pharmaceutical Society of Japan

  16. Formation of microemulsion: Effect of temperature and polyacrylamide

    SciTech Connect

    John, A.C.; Rakshit, A.K. )

    1993-03-01

    The pseudoternary phase diagram of the system involving cyclohexane, sodium dodecyl sulphate, propanol, and water was constructed for an SDS-to-propanol mass ratio 1:2. The area of the monophasic microemulsion region was computed. The effects of change of temperature and change of concentration of water-soluble polyacrylamide (PAA) on the microemulsion zone as well as the conductance, viscosity, and adiabatic compressibility of the microemulsion systems were studied. It was observed that for the water system there is a critical temperature below which the microemulsion zone increases with temperature, though at higher temperature the zone decreases within the range studied. The effects of presence of polyacrylamide above and below 0.003%(w/v)also are different from each other.

  17. Quantitative characterization of the viscosity of a microemulsion

    NASA Technical Reports Server (NTRS)

    Berg, Robert F.; Moldover, Michael R.; Huang, John S.

    1987-01-01

    The viscosity of the three-component microemulsion water/decane/AOT has been measured as a function of temperature and droplet volume fraction. At temperatures well below the phase-separation temperature the viscosity is described by treating the droplets as hard spheres suspended in decane. Upon approaching the two-phase region from low temperature, there is a large (as much as a factor of four) smooth increase of the viscosity which may be related to the percolation-like transition observed in the electrical conductivity. This increase in viscosity is not completely consistent with either a naive electroviscous model or a simple clustering model. The divergence of the viscosity near the critical point (39 C) is superimposed upon the smooth increase. The magnitude and temperature dependence of the critical divergence are similar to that seen near the critical points of binary liquid mixtures.

  18. Quantitative characterization of the viscosity of a microemulsion

    NASA Technical Reports Server (NTRS)

    Berg, Robert F.; Moldover, Michael R.; Huang, John S.

    1987-01-01

    The viscosity of the three-component microemulsion water/decane/AOT has been measured as a function of temperature and droplet volume fraction. At temperatures well below the phase-separation temperature the viscosity is described by treating the droplets as hard spheres suspended in decane. Upon approaching the two-phase region from low temperature, there is a large (as much as a factor of four) smooth increase of the viscosity which may be related to the percolation-like transition observed in the electrical conductivity. This increase in viscosity is not completely consistent with either a naive electroviscous model or a simple clustering model. The divergence of the viscosity near the critical point (39 C) is superimposed upon the smooth increase. The magnitude and temperature dependence of the critical divergence are similar to that seen near the critical points of binary liquid mixtures.

  19. [Study on the solubilization of O/W microemulsion for volatile oil].

    PubMed

    Yi, Hong; Yang, Hua; Deng, Mao

    2008-06-01

    To study the solubilization of O/W microemulsion system for volatile oil. Pseudo-ternary phase diagrams were prepared by using the method of titration, then investigating the solubilization of microemulsion system for different kind of volatile oil was investigated with the diagrams, and the effect of the formulation of microemulsion on the solubilization of Citrus sinensis oil were studied. Kinds of volatile oil have an accelerated solubility in the microemulsion system. The species and dosage of oil phase and surfactant could influence the solubilization of microemulsion on Citrus sinensis oil. It is recommended to select a new method to solve the stabilization of volatile oil in the liquid preparation by the solubilization of suitable formulation of microemulsion.

  20. Influence of the composition of monoacyl phosphatidylcholine based microemulsions on the dermal delivery of flufenamic acid.

    PubMed

    Hoppel, Magdalena; Ettl, Hanna; Holper, Evelyn; Valenta, Claudia

    2014-11-20

    Although microemulsions are one of the most promising dermal carrier systems, their clinical use is limited due to their skin irritation potential. Therefore, microemulsions based on naturally derived monoacyl phosphatidylcholine (MAPL) were developed. The influence of the water, oil and surfactant content on dermal delivery of flufenamic acid was systematically investigated for the first time. A water-rich microemulsion led to significantly higher in vitro skin penetration of flufenamic acid compared to other microemulsions. The superiority of the water-rich microemulsion over a marketed flufenamic acid containing formulation was additionally confirmed. Differences in drug delivery could be explained by alterations of the microemulsions after application. Evaporation of isopropanol led to crystal-like structures of MAPL on the skin surface from the surfactant- or oleic acid-rich microemulsions. In contrast, the formation of this additional barrier was hindered in case of the water-rich microemulsion. The skin penetration of MAPL was additionally analyzed by combined ATR-FTIR and tape stripping experiments, where MAPL itself penetrated only into the initial layers of the stratum corneum, independent of the microemulsion composition. Since a surfactant must penetrate the skin to cause irritation, MAPL can be presumed as a skin-friendly emulsifier with the ability to stabilize pharmaceutically acceptable microemulsions. Copyright © 2014 Elsevier B.V. All rights reserved.

  1. Low-pressure lipase-catalyzed production of mono- and diglycerides with and without N-butane and AOT surfactant.

    PubMed

    Valério, Alexsandra; Fiametti, Karina G; Rovani, Suzimara; Treichel, Helen; de Oliveira, Débora; Oliveira, J Vladimir

    2010-03-01

    The aim of this work is to report the production of mono- and diglycerides from olive oil at ambient condition and in pressurized n-butane as solvent medium. For this purpose, a commercial immobilized lipase (Novozym 435) was employed as catalyst and sodium (bis-2-ethyl-hexyl) sulfosuccinate (Aerosol-OT or AOT) as surfactant. The experiments were conducted in batch mode varying the temperature, pressure, and AOT concentration. Results showed that lipase-catalyzed glycerolysis either with compressed n-butane or in solvent-free system with AOT as surfactant might be a potential alternative route to conventional methods, as high contents of reaction products, especially monoglycerides ( approximately 60 wt.%), were achieved at mild temperature and pressure with a relatively low solvent to substrates mass ratio (4:1) in short reaction times (2 h).

  2. Form fluctuations of polymer loaded spherical microemulsions studied by neutron scattering and dielectric spectroscopy

    NASA Astrophysics Data System (ADS)

    Kuttich, B.; Falus, P.; Grillo, I.; Stühn, B.

    2014-08-01

    We investigate the structure and shell dynamics of the droplet phase in water/AOT/octane microemulsions with polyethyleneglycol (MW = 1500) molecules loaded in the droplets. Size and polydispersity of the droplets is determined with small angle X-ray scattering and small angle neutron scattering experiments. Shell fluctuations are measured with neutron spin echo spectroscopy and related to the dynamic percolation seen in dielectric spectroscopy. Shell fluctuations are found to be well described by the bending modulus of the shell and the viscosities inside and outside the droplets. Addition of the polymer decreases the modulus for small droplets. For large droplets the opposite is found as percolation temperature shifts to higher values.

  3. Assimilation of AERONET and MODIS AOT observations using variational and ensemble data assimilation methods and its impact on aerosol forecasting skill

    NASA Astrophysics Data System (ADS)

    Rubin, Juli I.; Reid, Jeffrey S.; Hansen, James A.; Anderson, Jeffrey L.; Holben, Brent N.; Xian, Peng; Westphal, Douglas L.; Zhang, Jianglong

    2017-05-01

    Data assimilation of Aerosol Robotic Network (AERONET) and Moderate Resolution Imaging Spectroradiometer (MODIS) aerosol optical thickness (AOT) for aerosol forecasting was tested within the Navy Aerosol Analysis Prediction System (NAAPS) framework, using variational and ensemble data assimilation methods. Navy aerosol forecasting currently makes use of a deterministic NAAPS simulation coupled to Navy Variational Data Assimilation System for aerosol optical depth, a two-dimensional variational data assimilation system, for MODIS AOT assimilation. An ensemble version of NAAPS (ENAAPS) coupled to an ensemble adjustment Kalman filter (EAKF) from the Data Assimilation Research Testbed was recently developed, allowing for a range of data assimilation and forecasting experiments to be run with deterministic NAAPS and ENAAPS. The main findings are that the EAKF, with its flow-dependent error covariances, makes better use of sparse observations such as AERONET AOT. Assimilating individual AERONET observations in the two-dimensional variational system can increase the analysis errors when observations are located in high AOT gradient regions. By including AERONET with MODIS AOT assimilation, the magnitudes of peak aerosol events (AOT > 1) were better captured with improved temporal variability, especially in India and Asia where aerosol prediction is a challenge. Assimilating AERONET AOT with MODIS had little impact on the 24 h forecast skill compared to MODIS assimilation only, but differences were found downwind of AERONET sites. The 24 h forecast skill was approximately the same for forecasts initialized with analyses from AERONET AOT assimilation alone compared to MODIS assimilation, particularly in regions where the AERONET network is dense; including the United States and Europe, indicating that AERONET could serve as a backup observation network for over-land synoptic-scale aerosol events.

  4. Transdermal delivery of betahistine hydrochloride using microemulsions: physical characterization, biophysical assessment, confocal imaging and permeation studies.

    PubMed

    Hathout, Rania M; Nasr, Maha

    2013-10-01

    Transdermal delivery of betahistine hydrochloride encapsulated in various ethyl oleate, Capryol 90(®), Transcutol(®) and water microemulsion formulations was studied. Two different kinds of phase diagrams were constructed for the investigated microemulsion system. Pseudoplastic flow that is preferable for skin delivery was recorded for the investigated microemulsions. A balanced and bicontinuous microemulsion formulation was suggested and showed the highest permeation flux (0.50±0.030mgcm(-2)h(-1)). The effect of the investigated microemulsions on the skin electrical resistance was used to explain the high permeation fluxes obtained. Confocal laser scanning microscopy was used to confirm the permeation enhancement and to reveal the penetration pathways. The results obtained suggest that the proposed microemulsion system highlighted in the current work can serve as a promising alternative delivery means for betahistine hydrochloride.

  5. The synthesis of fluorescent polymers in the microstructured environment of water-in-oil microemulsions

    SciTech Connect

    Premchandran, R.; Banerjee, S.; John, V.T.

    1996-10-01

    The synthesis of highly conjugated 2-naphthol polymer, and its copolymers with 4-ethyl phenol is reported. The polymers are prepared in AOT/isooctane water-in-oil microemulsions by using an oxidative enzyme, horseradish peroxidase, solubilized within the aqueous core of the microemulsion droplets. The resulting polymers and copolymers are all fluorescent, have low molecular weights ranging from 600-1100, and are highly soluble in polar organic solvents. The fluorescence and UV-vis spectra indicate the presence of highly conjugated structures within the polymer. These conjugated moieties are of the quinonoid and diquinone type, as identified by FTIR and NMR studies. The polymer fluorescence can be tuned by varying the polymer composition.

  6. A facile construction strategy of stable lipid nanoparticles for drug delivery using a hydrogel-thickened microemulsion system

    NASA Astrophysics Data System (ADS)

    Chen, Huabing; Xiao, Ling; Du, Danrong; Mou, Dongsheng; Xu, Huibi; Yang, Xiangliang

    2010-01-01

    We report a novel facile method for preparing stable nanoparticles with inner spherical solid spheres and an outer hydrogel matrix using a hot O/W hydrogel-thickened microemulsion with spontaneous stability. The nanoparticles with average diameters of about 30.0 nm and 100.0 nm were constructed by cooling the hot hydrogel-thickened microemulsion at different temperatures, respectively. We explained the application of these nanoparticles by actualizing the cutaneous delivery of drug-loaded nanoparticles. The in vitro skin permeation studies showed that the nanoparticles could significantly reduce the penetration of model drugs through skin and resulted in their dermal uptakes in skin. The sol-gel process of TEOS was furthermore used in the template of HTM to regulate the particle size of nanoparticles. The coating of silica on the surface of nanoparticles could regulate the penetration of drug into skin from dermal delivery to transdermal delivery. This strategy provides a facile method to produce nanoparticles with long-term stability and ease of manufacture, which might have a promising application in drug delivery.

  7. Dielectric properties of anionic and nonionic surfactant microemulsions

    SciTech Connect

    Middleton, M.A. ); Schechter, R.S.; Johnston, K.P. )

    1990-05-01

    The dielectric permittivities of anionic and nonionic oil-continuous microemulsions have been measured with varying water content, temperature, alkane carbon number, and electrolyte concentration. The data confirm the hypothesis that underlying phase behavior and consequent morphology have a profound effect on the dielectric properties of microemulsions. The results make it abundantly evident that it is not possible to understand permittivity by use of a simple drop model for microemulsions. It is proposed that water-in-oil domains coexist with oil-in-water domains even at low water concentrations and low electrical conductivities and that the dielectric constant is sensitive to the fraction of each type of domain present in a system. A mean field approximation is used to evaluate the fraction of water-in-oil domains that coexist with oil-continuous domains in these predominately oil-in-water microemulsions.

  8. Evaluation of proton activity in microemulsions by a kinetic probe.

    PubMed

    Peñacoba, Indalecio A; García, Begoña; Navarro, Ana M; Hoyuelos, F Javier; Leal, José M

    2010-12-15

    The decomposition reaction of the purple dye murexide in acidic media is used as a probe indicator for protons in nonionic microemulsions. The reaction kinetics primarily rely on the proton concentration and permit assessment of the proton activity in the nonionic microemulsions of water/cyclohexane/Igepal and water/heptane/Igepal. The experiments performed in the two microemulsions covered a wide range of water-to-oil mass fraction for the two systems. The kinetic runs were monitored under pseudo-first order conditions by the stopped-flow technique. The equilibrium constants for the formation of purpuric acid and the kinetic constants for the ensuing decomposition reaction fulfill a trend consistent with the micro compartmentalized nature of the multicomponent medium, and support the use of murexide as an indicator of the proton activity in microemulsions.

  9. Development and antifungal evaluation of a food-grade U-type microemulsion.

    PubMed

    Zhang, H; Lu, Z; Wang, S; Shen, Y; Feng, F; Zheng, X

    2008-10-01

    Food-grade microemulsions have been of increasing interest to researchers as potential delivery systems for bioactive compounds. However, food-grade microemulsions are difficult to formulate and no microemulsion has been documented for antifungal purpose. The physicochemical characterization of a food-grade glycerol monolaurate (GML)/ethanol (EtOH)/Tween 80/potassium sorbate (PS)/water microemulsion system and the antifungal activities against Aspergillus niger and Penicillium italicum have been studied in this paper. The influence of EtOH and PS on oil solubilization capability was clearly reflected in the phase behaviour of U-type microemulsion systems. One dilution-stable formulation ME (GML/EtOH/Tween 80/PS/water = 3 : 3 : 3.5 : 10.5 : 16) was selected. After 4 days of incubation, ME showed 80%A. niger growth inhibition at 0.2% and 72%P. italicum growth inhibition at 0.1%, respectively, and a delay of conidiation of 2 days compared with the control. In the antifungal activities of the microemulsion, GML and PS made major contributions with similar antifungal activities at a GML/PS weight ratio of 1: 3.5. Food-grade dilution-stable microemulsions prepared with GML as oil phase for antifungal purpose are feasible and solubilization of a hydrotrope contributes to the formation of microemulsions and enhanced antifungal activities. The present report represents the first to develop a food-grade microemulsion system for antifugal purpose.

  10. Microemulsion liquid membranes. I. Application to acetic acid removal from water

    SciTech Connect

    Wiencek, J.M.; Qutubuddin, S. )

    1992-08-01

    A separation technique utilizing nonionic microemulsions as emulsion liquid membranes has been successfully applied to the removal of acetic acid from an aqueous feed phase. The surfactant systems were carefully characterized in order to assure that they were truly microemulsions. The effects of mixing intensity, feed concentration, treat ratio, and microemulsion viscosity on the separation kinetics were investigated. The microemulsions did not typically display leakage and had negligible swell over 5-minute duration. The reversible phase behavior of the microemulsion was utilized to demulsify the liquid membrane phase and recover the acetate ion via a temperature change of approximately 40 C. Material balances closed to within 10% and rates of separation were faster than the sampling rates when the microemulsion was fully dispersed in the aqueous feed phase.

  11. Structure and Solvent Properties of Microemulsions

    ERIC Educational Resources Information Center

    Katz, Civia A.; Calzola, Zachary J.; Mbindyo, Jeremiah K. N.

    2008-01-01

    A microscale laboratory experiment to investigate the formation and utility of microemulsions is described. Microemulsions are technologically important fluids that can reduce the use of toxic organic solvents. In the experiment, students prepare a microemulsion and compare the solubility of sudan III dye in the microemulsion and in dodecane. They…

  12. Structure and Solvent Properties of Microemulsions

    ERIC Educational Resources Information Center

    Katz, Civia A.; Calzola, Zachary J.; Mbindyo, Jeremiah K. N.

    2008-01-01

    A microscale laboratory experiment to investigate the formation and utility of microemulsions is described. Microemulsions are technologically important fluids that can reduce the use of toxic organic solvents. In the experiment, students prepare a microemulsion and compare the solubility of sudan III dye in the microemulsion and in dodecane. They…

  13. Nucleation and growth mechanism of Pd/Pt bimetallic clusters in sodium bis(2-ethylhexyl)sulfosuccinate (AOT) reverse micelles as studied by in situ X-ray absorption spectroscopy.

    PubMed

    Chen, Ching-Hsiang; Hwang, Bing-Joe; Wang, Guo-Rung; Sarma, Loka Subramanyam; Tang, Mau-Tsu; Liu, Din-Goa; Lee, Jyh-Fu

    2005-11-24

    We report in situ X-ray absorption spectroscopy (XAS) investigations on the formation of palladium-platinum (Pd/Pt) bimetallic clusters at the early stage within the water-in-oil microemulsion system of water/AOT/n-heptane. The reduction of palladium and platinum ions and the formation of corresponding clusters are monitored as a function of dosage of reducing agent, hydrazine (N(2)H(5)OH). Upon successive addition of the reducing agent, hydrazine (N(2)H(5)OH), five distinguishable steps are observed in the formation process of Pd/Pt clusters at the early stage. Both in situ X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) analysis for both the Pd K-edge and Pt L(III)-edge revealed the formation of Pd/Pt bimetallic clusters. A corresponding structural model is proposed for each step to provide a detailed insight into the nucleation and growth mechanism of Pd/Pt bimetallic clusters. We also discussed the atomic distribution of Pd and Pt atoms in Pd/Pt bimetallic clusters based on the calculated XAS structural parameters.

  14. Characterization and antimicrobial activity of a pharmaceutical microemulsion.

    PubMed

    Zhang, Hui; Cui, Yinan; Zhu, Songming; Feng, Fengqin; Zheng, Xiaodong

    2010-08-16

    The characterization of a pharmaceutical microemulsion system with glycerol monolaurate as oil, ethanol as cosurfactant, Tween 40 as surfactant, sodium diacetate and water, and the antimicrobial activities against Escherichia coli, Staphylococcus aureus, Bacillus subtilis, Candida albicans, Aspergillus niger and Penicillium expansum have been studied. The influence of ethanol and sodium diacetate on oil solubilization capability was clearly reflected in the phase behavior of these systems. One microemulsion formulation was obtained and remained stable by physical stability studies. The antimicrobial assay using solid medium diffusion method showed that the prepared microemulsion was comparable to the commonly used antimicrobials as positive controls. The kinetics of killing experiments demonstrated that the microemulsion caused a complete loss of viability of bacterial cells (E. coli, S. aureus and B. subtilis) in 1 min, killed over 99% A. niger and P. expansum spores and 99.9% C. albicans cells rapidly within 2 min and resulted in a complete loss of fungal viability in 5 min. The fast killing kinetics of the microemulsion was in good agreement with the transmission electron microscopy observations, indicating the antimembrane activity of the microemulsion on bacterial and fungal cells due to the disruption and dysfunction of biological membranes and cell walls. Copyright (c) 2010 Elsevier B.V. All rights reserved.

  15. Fluorescent Probe Study of AOT Vesicle Membranes and Their Alteration upon Addition of Aniline or the Aniline Dimer p-Aminodiphenylamine (PADPA).

    PubMed

    Iwasaki, Fumihiko; Luginbühl, Sandra; Suga, Keishi; Walde, Peter; Umakoshi, Hiroshi

    2017-02-28

    Artificial vesicles formed from sodium bis(2-ethylhexyl) sulfosuccinate (AOT) in aqueous solution are used successfully as additives for enzymatic oligomerizations or polymerizations of aniline or the aniline dimer p-aminodiphenylamine (PADPA) under slightly acidic conditions (e.g., pH 4.3 with horseradish peroxidase and hydrogen peroxide as oxidants). In these systems, the reactions occur membrane surface-confined. Therefore, (i) the physicochemical properties of the vesicle membrane and (ii) the interaction of aniline or PADPA with the AOT membrane play crucial roles in the progress and final outcome of the reactions. For this reason, the properties of AOT vesicles with and without added aniline or PADPA were investigated by using two fluorescent membrane probes: 1,6-diphenyl-1,3,5-hexatriene (DPH) and 6-lauroyl-2-dimethylaminonaphthalene (Laurdan). DPH and Laurdan were used as "sensors" of the membrane fluidity, surface polarity, and membrane phase state. Moreover, the effect of hexanol, alone or in combination with aniline or PADPA, as a possible modifier of the AOT membrane, was also studied with the aim of evaluating whether the membrane fluidity and surface polarity is altered significantly by hexanol, which, in turn, may have an influence on the mentioned types of reactions. The data obtained indicate that the AOT vesicle membrane at room temperature and pH 4.3 (0.1 M NaH2PO4) is more fluid and has a more polar surface than in the case of fluid phospholipid vesicle membranes formed from 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC). Furthermore, the fluorescence measurements indicate that mixed AOT-hexanol membranes are less fluid than pure AOT membranes and that they have a lower surface polarity than pure AOT membranes. PADPA strongly binds to AOT and to mixed AOT/hexanol membranes and leads to drastic changes in the membrane properties (decrease in fluidity and surface polarity), resulting in Laurdan fluorescence spectra, which are characteristic for

  16. Fluctuations and interactions in microemulsions

    SciTech Connect

    Menes, R.; Safran, S.A.; Strey, R.

    1995-12-01

    We review the properties of microemulsions as described by an interfacial model which focuses upon the deformations of the surfactant monolayer separating mesoscopic water and oil domains. In some cases, the interfacial shape is well defined, resulting in a globular phase, while in others, the interface is strongly affected by thermal fluctuations, resulting in a random, sponge-like structure. In the globular phase, interactions between globules can result in phase coexistence comparable to those observed in polymeric systems. Recent experiments indicate that these interactions can result in closed-loop coexistence regions in the isothermal, concentration phase diagram. We propose a mechanism for this reentrant phase separation based on the combined effects of a shape transition and attractive interactions. Long cylindrical globules can phase separate at relatively low interglobular attractions. A transformation from elongated globules to compact spherical drops alters the balance between the entropy and the effective interglobule interactions, leading to the remixing of the globular system.

  17. Octanoyl galactose ester-modified microemulsion system self-assembled by coix seed components to enhance tumor targeting and hepatoma therapy

    PubMed Central

    Qu, Ding; Liu, Mingjian; Huang, Mengmeng; Wang, Lixiang; Chen, Yan; Liu, Congyan; Liu, Yuping

    2017-01-01

    A nanosized drug delivery platform with a combination of rational components and tumor targeting is significant for enhancement of anticancer therapy and reduction of side effects. In this study, we developed a octanoyl galactose ester-modified microemulsion system self-assembled by coix seed components (Gal(oct)-C-MEs), which improved the tumor accumulation through asialoglycoprotein receptor-mediated endocytosis and promoted the antitumor efficacy through multicomponent-mediated synergistic effect. Octanoyl galactose ester (Gal(oct)) with a yield of 82.3% was synthesized through a green enzymatic reaction and multidimensional characterization. Gal(oct)-C-MEs with a spherical shape had a small and uniform particle size (58.49±1.03 nm), narrow polydispersity index (0.09±0.01) and neutral surface charge (−5.82±0.57 mV). In the cellular uptake studies, the internalized Gal(oct)-C-ME was 2.28-fold higher relative to that of coix seed component-based microemulsions (C-MEs). The half-maximal inhibitory concentration of Gal(oct)-C-MEs against HepG2 cells was 46.5±2.4 μg/mL, which was notably higher than that of C-MEs. Importantly, the intratumor fluorescence of HepG2 xenograft-bearing nude mice treated with Cy5/Gal(oct)-C-MEs was 1.9-fold higher relative to treatment with Cy5/C-MEs. In the study of antitumor efficacy in vivo, HepG2 xenograft-bearing nude mice intragastrically administered Gal(oct)-C-MEs for 14 days exhibited the strongest inhibition of tumor growth and the lowest toxicity against liver and kidney among all the treatments. In summary, Gal(oct)-C-ME, as a highly effective and safe anticancer drug delivery system, showed promising potential for hepatoma therapy. PMID:28352174

  18. Lecithin-Linker Microemulsion Gelatin Gels for Extended Drug Delivery

    PubMed Central

    Xuan, Xiao-Yue; Cheng, Yu-Ling; Acosta, Edgar

    2012-01-01

    This article introduces the formulation of alcohol-free, lecithin microemulsion-based gels (MBGs) prepared with gelatin as gelling agent. The influence of oil, water, lecithin and hydrophilic and lipophilic additives (linkers) on the rheological properties and appearance of these gels was systematically explored using ternary phase diagrams. Clear MBGs were obtained in regions of single phase microemulsions (μEs) at room temperature. Increasing the water content in the formulation increased the elastic modulus of the gels, while increasing the oil content had the opposite effect. The hydrophilic additive (PEG-6-caprylic/capric glycerides) was shown to reduce the elastic modulus of gelatin gels, particularly at high temperatures. In contrast to anionic (AOT) μEs, the results suggest that in lecithin (nonionic) μEs, the introduction of gelatin “dehydrates” the μE. Finally, when the transdermal transport of lidocaine formulated in the parent μE and the resulting MBG were compared, only a minor retardation in the loading and release of lidocaine was observed. PMID:24300183

  19. Amphotericin B in oil-water lecithin-based microemulsions: formulation and toxicity evaluation.

    PubMed

    Brime, Begoña; Moreno, Marco A; Frutos, Gloria; Ballesteros, Ma Paloma; Frutos, Paloma

    2002-04-01

    A novel lecithin-based microemulsion containing AmB was developed to reduce the toxic effects of the drug, comparing it with the commercial formulation Fungizone. Phase diagrams containing the microemulsion region were constructed for pseudoternary systems composed of isopropil myristate (IPM)/Brij((R)) 96V/lecithin/water. The incorporation of AmB to the microemulsions was done following the Phase Inversion Temperature (PIT) method or by diluting the drug in the aqueous phase of the disperse system before forming the microemulsion. The percentage of drug entrapped in the microemulsion was analyzed by an HPLC method obtaining recoveries > 98%. Mean droplet size of the microemulsions chosen for the acute toxicity evaluation was of 45 nm, and the rheological studies showed that those microemulsions mentioned followed a Newtonian behavior. Different studies are described in this work to prove the stability of these new dosage forms. Acute toxicity results, determined by a graphic method, the probit binary model and the Reed and Muench method showed that lethal dose 50 (LD(50)) for AmB microemulsions was of 2.9 mgkg(-1) compared to 1.4 mgkg(-1) for the commercial deoxycholate suspension, Fungizone. The overall results indicate that treatment with AmB microemulsions was less toxic than Fungizone, suggesting a potential therapeutic application.

  20. Buckminsterfullerene-containing microemulsions

    SciTech Connect

    Zhang, W.; Honeychuck, R.V.; Hussam, A.

    1996-03-06

    We have shown that C{sub 60}-containing microemulsions can be readily prepared. This opens up the possibility of studying C{sub 60} molecules in a medium which has significant practical applications. One of the most intriguing aspects of this work is the revelation of a local C{sub 60} environment, inside the micelles, which is largely aromatic and weakly polar. This shows that van der Waals interactions between a fullerene molecule and the aromatic {pi} cloud of the solvent molecules are important in bringing the solute into solution in a largely aliphatic micellar interior. 23 refs., 1 fig.

  1. Hierarchically structured bicontinuous polymeric microemulsions

    SciTech Connect

    Fleury, Guillaume; Bates, Frank S.

    2012-07-24

    We recently described the synthesis and phase behavior of a new type of CECEC-P multiblock copolymer composed of glassy poly(cyclohexylethylene) (C), semicrystalline poly(ethylene) (E), and elastomeric poly(ethylene-alt-propylene) (P) with symmetric (equal volume) CECEC and P sequences (G. Fleury and F. S. Bates, Macromolecules, 2009, 42, 3598-3610). Here we report the formation and characterization of a multicontinuous structure based on the blending of CEC triblock copolymer and P homopolymer with such a hexablock copolymer along the 50:50 (CEC/P) isopleth. These materials produce a sequence of phases that are correlated with the volume fraction of CECEC-P as evidenced by SAXS and TEM measurements. A percolating bicontinuous mesostructure was identified at volume fractions of hexablock copolymer, f{sub CECEC-P} = 0.10 and 0.125, within the composition range known to result in a bicontinuous morphology in A-B/A/B systems. A solid product was formed by cooling the initially homogeneous ternary mixture from above the melting temperature of the E blocks to room temperature. Crystallization of E leads to microphase separation of C and E and simultaneous ejection of P from CEC (and CECEC) at a larger length scale. The mechanical properties of these materials are inferior to what is anticipated based on pure CEC triblock copolymer, attributable to the low molecular weight and irregular structure of the C/E region sequences. Nevertheless, this study establishes a procedure for producing bicontinuous yet structurally asymmetric materials based on the microemulsion process and extends the concept of a microemulsion to multiblock copolymers.

  2. Sustainable polymerizations in recoverable microemulsions.

    PubMed

    Chen, Zhenzhen; Yan, Feng; Qiu, Lihua; Lu, Jianmei; Zhou, Yinxia; Chen, Jiaxin; Tang, Yishan; Texter, John

    2010-03-16

    Free radical and atom-transfer radical polymerizations were conducted in monomer/ionic liquid microemulsions. After the polymerization and isolation of the resultant polymers, the mixture of the catalyst and ionic liquids (surfactant and continuous phase) can be recovered and reused, thereby dramatically improving the environmental sustainability of such chemical processing. The addition of monomer to recovered ionic liquid mixtures regenerates transparent, stable microemulsions that are ready for the next polymerization cycle upon addition of initiator. The method combines the advantages of IL recycling and microemulsion polymerization and minimizes environmental disposable effects from surfactants and heavy metal ions.

  3. Thermal fluctuations and phase equilibrium in microemulsions

    NASA Astrophysics Data System (ADS)

    Golubović, Leonardo; Lubensky, T. C.

    1990-04-01

    We construct a simple coarse-grained model and use it to study global phase behavior of ensembles of fluid membranes. This model is an improvement over previous phenomenological models of Talmon and Prager, de Gennes and co-workers, Widom, and more recently of Safran and co-workers. We show here that there is necessarily an entropic contribution, missing in all previous theories, to the coarse-grained free energy whose physical origin is the same as that of Helfrich's entropic repulsion stabilizing lamellar multimembrane phases. The inclusion of this steric entropy in the previous phenomenological studies is essential if they are to be used in the study of periodic phases in microemulsions and analogous surfactant systems. Thus the model enables us to obtain, in a unified way, phase diagrams containing both uniform and periodic phases in microemulsions and in binary systems of nonionic surfactant bilayers in a single solvent. Mean-field theory for this model yields rich phase diagrams containing dilute, random bicontinuous, lamellar, columnar, and an antiferromagnetic phase that may correspond to a droplet crystal or to a ``plumber's nightmare.'' The model depends on two phenomenological parameters related to strengths of steric entropy and softening of membrane rigidity. We discuss the sensitivity of phase diagrams (in particular the existence of the middle-phase microemulsion) to values of these parameters. We find that the existence of a realistic middle phase (with structural length scale much larger than the molecular length scale) crucially depends on the presence of steric entropy. The model reproduces the experimentally observed four-phase equilibria among uniform phases in microemulsions.

  4. Thermal fluctuations and phase equilibrium in microemulsions

    SciTech Connect

    Golubovic, L. Solid State Center, University of California, Los Angeles, Los Angeles, CA ); Lubensky, T.C. )

    1990-04-15

    We construct a simple coarse-grained model and use it to study global phase behavior of ensembles of fluid membranes. This model is an improvement over previous phenomenological models of Talmon and Prager, de Gennes and co-workers, Widom, and more recently of Safran and co-workers. We show here that there is necessarily an entropic contribution, missing in all previous theories, to the coarse-grained free energy whose physical origin is the same as that of Helfrich's entropic repulsion stabilizing lamellar multimembrane phases. The inclusion of this steric entropy in the previous phenomenological studies is essential if they are to be used in the study of periodic phases in microemulsions and analogous surfactant systems. Thus the model enables us to obtain, in a unified way, phase diagrams containing both uniform and periodic phases in microemulsions and in binary systems of nonionic surfactant bilayers in a single solvent. Mean-field theory for this model yields rich phase diagrams containing dilute, random bicontinuous, lamellar, columnar, and an antiferromagnetic phase that may correspond to a droplet crystal or to a plumber's nightmare.'' The model depends on two phenomenological parameters related to strengths of steric entropy and softening of membrane rigidity. We discuss the sensitivity of phase diagrams (in particular the existence of the middle-phase microemulsion) to values of these parameters. We find that the existence of a realistic middle phase (with structural length scale much larger than the molecular length scale) crucially depends on the presence of steric entropy. The model reproduces the experimentally observed four-phase equilibria among uniform phases in microemulsions.

  5. In situ microemulsion synthesis of hydroxyapatite-MgFe2O4 nanocomposite as a magnetic drug delivery system.

    PubMed

    Foroughi, Firoozeh; Hassanzadeh-Tabrizi, S A; Bigham, Ashkan

    2016-11-01

    In this study, an innovative synthesis process has been developed to produce hydroxyapatite-magnesium ferrite (HA-MgFe2O4) nanocomposite. In addition, the effect of calcination temperature on drug delivery behavior of produced samples was investigated. HA-MgFe2O4 nanocomposite was prepared via one-step modified reverse microemulsion synthesis route. The resulting products were characterized by X-ray Diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), vibrating sample magnetometer (VSM), and Brunauer-Emmett-Teller surface area analysis (BET). The calcined samples at 500 and 700°C demonstrated mesoporous characteristics and large specific surface areas of 88 and 32m(2)/g, respectively. TEM and VSM results showed that the nanocomposite calcined at 700°C has core-shell morphology and a maximum saturation magnetization of 9.47emug(-1). Copyright © 2016 Elsevier B.V. All rights reserved.

  6. Microstructure of supercritical CO2-in-water microemulsions: a systematic contrast variation study.

    PubMed

    Klostermann, Michael; Foster, Tobias; Schweins, Ralf; Lindner, Peter; Glatter, Otto; Strey, Reinhard; Sottmann, Thomas

    2011-12-07

    Microemulsions of the type H(2)O-scCO(2)-surfactant are potential candidates for novel solvent mixtures in the field of green chemistry. Furthermore, scCO(2)-microemulsions are highly interesting from a fundamental point of view since their properties such as the bending elastic constants can be strongly influenced solely by varying the pressure without changing the components. With this motivation we studied the phase behavior and the microstructure of water-rich scCO(2)-microemulsions. Such microemulsions were formulated using the technical grade non-ionic surfactants Zonyl FSO 100 and Zonyl FSN 100. At elevated pressures the temperature dependent phase behavior of these systems follows the general patterns of non-ionic microemulsions. Small angle neutron scattering experiments were conducted to determine the length scales and the topology of the microstructure of these systems. Having determined the exact scattering length densities and the composition of the respective sub-phases by a systematic contrast variation we could show that these systems consist of CO(2)-swollen microemulsion droplets that are dispersed in a continuous aqueous-phase. The scattering data were analyzed using a newly derived form factor for polydisperse, spherical core/shell particles with diffuse interfaces. The underlying analytical density profiles could be confirmed applying the model-free Generalized Indirect Fourier Transformation (GIFT) to the scattering data. Following the general patterns of non-ionic microemulsions the radius of the microemulsion droplets is found to increase almost linearly upon the addition of CO(2).

  7. Improved intestinal delivery of salmon calcitonin by water-in-oil microemulsions.

    PubMed

    Fan, Yating; Li, Xinru; Zhou, Yanxia; Fan, Chao; Wang, Xiaoning; Huang, Yanqing; Liu, Yan

    2011-09-15

    Therapeutic peptides are highly potent and specific in their functions, but difficulties in their oral administration require parallel development of viable delivery systems to improve their oral bioavailability. The objective of this study was to explore the feasibility of water-in-oil (w/o) microemulsions for improving the absorption of intraduodenally administered salmon calcitonin (sCT). The w/o microemulsions were prepared from medium chain triglyceride, Tween 80 and Span 80 or soybean phosphatidylcholine, propylene glycol and phosphate saline, and characterized by particle size and in vitro physical stability under dilution with different physiologically relevant diluents. The effects of addition of polymers such as hydroxypropylmethylcellulose and Carbomer into aqueous phase on the properties of microemulsions were assessed. sCT was efficiently encapsulated into microemulsions with nanoscaled diameter ranged from about 6 to 134nm. As expected from the non-ionic nature of the investigated microemulsions, the physical stability, evaluated by visual inspection, the particle size and leakage percent under dilution, was found to be unaffected by pH and/or ionic strength of diluents and it was opposite for the microemulsions with ionic components. In addition, the dilution extent had a pronounced effect on the physical stability of the diluted microemulsions. The effect of polymers added into aqueous phase of the microemulsions on the absorption of the drug entrapped in microemulsions with different components was investigated. The optimized microemulsions were shown to generate substantial enhancement (up to 4-fold) of relative pharmacological activity of sCT with regard to the control solution of the drug. This indicated that the w/o microemulsions could offer the potential to significantly improve intestinal absorption of sCT. Copyright © 2011 Elsevier B.V. All rights reserved.

  8. Structural studies of 1-butyl-3-methylimidazolium tetrafluoroborate/TX-100/ p-xylene ionic liquid microemulsions.

    PubMed

    Gao, Yan'an; Zhang, Jin; Xu, Hongyan; Zhao, Xueyan; Zheng, Liqiang; Li, Xinwei; Yu, Li

    2006-07-17

    The ionic liquid (IL) 1-butyl-3-methylimidazolium tetrafluoroborate (bmimBF4) forms nonaqueous microemulsions with p-xylene, with the aid of the nonionic surfactant TX-100. The phase behavior of the ternary system is investigated, and three microregions of the microemulsions-ionic liquid-in-oil (IL/O), bicontinuous, and oil-in-ionic liquid (O/IL)-are identified by conductivity measurements, according to percolation theory. On the basis of a phase diagram, a series of IL/O microemulsions are chosen and characterized by dynamic light scattering (DLS). The size of aggregates increases on increasing the amount of added polar component (bmimBF(4)), which is a similar phenomenon to that observed for typical water-in-oil (W/O) microemulsions, suggesting the formation of IL/O microemulsions. The microstructural characteristics of the microemulsions are investigated by FTIR and 1H NMR spectroscopy. The results indicate that the interaction between the electronegative oxygen atoms of the oxyethylene (OE) units in TX-100 and the electropositive imidazolium ring may be the driving force for the solubilization of bmimBF4 into the core of the TX-100 aggregates. In addition, the micropolarity of the microemulsions is investigated by using methyl orange (MO) as a UV/Vis spectroscopic probe. A relatively constant polarity of the microemulsion droplets is obtained in the IL microemulsion. Finally, a plausible structure for the IL/O microemulsion is presented.

  9. Evolution of the nonionic inverse microemulsion-acid-TEOS system during the synthesis of nanosized silica via the sol-gel process.

    PubMed

    Asaro, F; Benedetti, A; Freris, I; Riello, P; Savko, N

    2010-08-03

    The cyclohexane-igepal inverse microemulsion, comprehensively established for the synthesis of silica nanoparticles in an ammonia-catalyzed sol-gel process, was alternatively studied with an acid-catalyzed sol-gel process. Tetraethyl orthosilicate (TEOS) was used as the silica precursor, while two different aqueous phases containing either HNO(3) or HCl at two different concentrations, 0.1 and 0.05 M, were examined in the presence and in the absence of NaF, a catalyst of the condensation step. The evolution of the overall reacting system, specifically hydrolysis and polycondensation of reaction intermediates, was monitored in situ by time-resolved small-angle X-ray scattering. No size variation of the inverse micelles was detected throughout the sol-gel process. Conversely, the density of the micellar core increased after a certain time interval, indicating the presence of the polycondensation product. The IR spectra of the reacting mixture were in agreement with such a hypothesis. (1)H and (13)C NMR measurements provided information on the soluble species, the surfactant, and TEOS. The TEOS consumption was well fitted by means of an exponential decay, suggesting that a first-order kinetics for TEOS transpires in the various systems examined, with rate constants dependent not only on the acid concentration but also on its nature (anion specific effect), on the presence of NaF, and on the amount of water in the core of the inverse micelle. The self-diffusion coefficients, determined by means of PGSTE NMR, proved that a sizable amount of the byproduct ethanol was partitioned inside the inverse micelles. Characterization of the final product was carried out by means of thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and transmission electron microscopy (TEM), which concurrently confirmed that the silica isolated from the inverse nonionic microemulsion is not significantly different from the product of a bulk acid-catalyzed sol-gel synthesis

  10. Terpene microemulsions for transdermal curcumin delivery: effects of terpenes and cosurfactants.

    PubMed

    Liu, Chi-Hsien; Chang, Fu-Yen; Hung, De-Kai

    2011-01-01

    Microemulsion systems composed of terpenes, polysorbate 80, cosurfactants, and water were investigated as transdermal delivery vehicles for curcumin. Pseudoternary phase diagrams of three terpenes (limonene, 1,8-cineole, and α-terpineol) at a constant surfactant/cosurfactant ratio (1:1) were constructed to illustrate their phase behaviors. Limonene combined with cosurfactants like ethanol, isopropanol, and propylene glycol were employed as microemulsion ingredients to study their potential for transdermal curcumin delivery. The transdermal delivery efficacy and skin retention of curcumin were evaluated using neonate pig skin mounted on a Franz diffusion cell. The curcumin permeation rates in the limonene microemulsion studied were 30- and 44-fold higher than those of 1,8-cineole and α-terpineol microemulsions, respectively. Significant effects on the skin permeation rates were observed from microemulsions containing different limonene/water contents. Histological examination of treated skin was performed to investigate the change of skin morphologies. Characteristics such as droplet size, conductivity, interfacial tension, and viscosity were analyzed to understand the physicochemical properties of the transdermal microemulsions. In conclusion, microemulsions loaded with curcumin were successfully optimized for transdermal delivery after screening various terpenes, cosurfactants, and limonene/water ratios. These results indicate that the limonene microemulsion system is a promising tool for the percutaneous delivery of curcumin.

  11. Bicontinuous Polymeric Microemulsions from Polydisperse Diblock Copolymers

    SciTech Connect

    Ellison, Christopher J.; Meuler, Adam J.; Qin, Jian; Evans, Christopher M.; Wolf, Lynn M.; Bates, Frank S.

    2009-06-12

    Polymeric bicontinuous microemulsions are thermodynamically stable structures typically formed by ternary blends of immiscible A and B homopolymers and a macromolecular surfactant such as an AB diblock copolymer. Investigations of these bicontinuous morphologies have largely focused on model systems in which all components have narrow molecular weight distributions. Here we probe the effects of AB diblock polydispersity in ternary blends of polystyrene (PS), polyisoprene (PI), and poly(styrene-b-isoprene) (PS-PI). Three series of blends were prepared using the same PS and PI homopolymers; two of them contain nearly monodisperse components while the third includes a polydisperse PS-PI diblock. The PS and PI homopolymers and two of the PS-PI diblocks were prepared by anionic polymerization using sec-butyllithium and have narrow molecular weight distributions. The polydisperse PS-PI diblock was prepared by anionic polymerization using the functional organolithium 3-tert-butyldimethylsilyloxy-1-propyllithium; this diblock has a polydisperse PS block (M{sub w}/M{sub n} = 1.57) and a nearly monodisperse PI block (Mw/Mn < 1.1). The phase behavior of the three series of blends was probed using a combination of dynamic mechanical spectroscopy, small-angle X-ray scattering, and cloud point measurements, and a bicontinuous microemulsion channel was identified in each system. These results prove that monodisperse components are not required to form bicontinuous microemulsions and highlight the utility of polydispersity as a tool to tune polymer blend phase behavior. The random-phase approximation, originally advanced by de Gennes, and self-consistent field theory are used to provide a theoretical supplement to the experimental work. These theories are able to predict the directions of the polydispersity-driven shifts in domain spacing, order-disorder transition temperatures, and the location of the microemulsion channel. Self-consistent field theory is also used in conjunction

  12. Bicontinuous polymeric microemulsions from polydisperse diblock copolymers.

    PubMed

    Ellison, Christopher J; Meuler, Adam J; Qin, Jian; Evans, Christopher M; Wolf, Lynn M; Bates, Frank S

    2009-03-26

    Polymeric bicontinuous microemulsions are thermodynamically stable structures typically formed by ternary blends of immiscible A and B homopolymers and a macromolecular surfactant such as an AB diblock copolymer. Investigations of these bicontinuous morphologies have largely focused on model systems in which all components have narrow molecular weight distributions. Here we probe the effects of AB diblock polydispersity in ternary blends of polystyrene (PS), polyisoprene (PI), and poly(styrene-b-isoprene) (PS-PI). Three series of blends were prepared using the same PS and PI homopolymers; two of them contain nearly monodisperse components while the third includes a polydisperse PS-PI diblock. The PS and PI homopolymers and two of the PS-PI diblocks were prepared by anionic polymerization using sec-butyllithium and have narrow molecular weight distributions. The polydisperse PS-PI diblock was prepared by anionic polymerization using the functional organolithium 3-tert-butyldimethylsilyloxy-1-propyllithium; this diblock has a polydisperse PS block (Mw/Mn = 1.57) and a nearly monodisperse PI block (Mw/Mn < 1.1). The phase behavior of the three series of blends was probed using a combination of dynamic mechanical spectroscopy, small-angle X-ray scattering, and cloud point measurements, and a bicontinuous microemulsion channel was identified in each system. These results prove that monodisperse components are not required to form bicontinuous microemulsions and highlight the utility of polydispersity as a tool to tune polymer blend phase behavior. The random-phase approximation, originally advanced by de Gennes, and self-consistent field theory are used to provide a theoretical supplement to the experimental work. These theories are able to predict the directions of the polydispersity-driven shifts in domain spacing, order-disorder transition temperatures, and the location of the microemulsion channel. Self-consistent field theory is also used in conjunction with the

  13. Rate of Molecular Transfer of Allyl Alcohol across an AOT Surfactant Layer Using Muon Spin Spectroscopy.

    PubMed

    Jayasooriya, Upali A; Clayden, Nigel J; Steytler, David C; Oganesyan, Vasily S; Peck, Jamie N T; Khasanov, Rustem; Scheuermann, Robert; Stoykov, Alexey

    2016-01-26

    The transfer rate of a probe molecule across the interfacial layer of a water-in-oil (w/o) microemulsion was investigated using a combination of transverse field muon spin rotation (TF-μSR), avoided level crossing muon spin resonance (ALC-μSR), and Monte Carlo simulations. Reverse microemulsions consist of nanometer-sized water droplets dispersed in an apolar solvent separated by a surfactant monolayer. Although the thermodynamic, static model of these systems has been well described, our understanding of their dynamics is currently incomplete. For example, what is the rate of solute transfer between the aqueous and apolar solvents, and how this is influenced by the structure of the interface? With an appropriate choice of system and probe molecule, μSR offers a unique opportunity to directly probe these interfacial transfer dynamics. Here, we have employed a well characterized w/o microemulsion stabilized by bis(2-ethylhexyl) sodium sulfosuccinate (Aerosol OT), with allyl alcohol (CH2═CH-CH2-OH, AA) as the probe. Resonances due to both muoniated radicals, CMuH2-C*H-CH2-OH and C*H2-CHMu-CH2-OH, were observed with the former being the dominant species. All resonances displayed solvent dependence, with those in the microemulsion observed as a single resonance located at intermediate magnetic fields to those present in either of the pure solvents. Observation of a single resonance is strong evidence for interfacial transfer being in the fast exchange limit. Monte Carlo calculations of the ΔM = 0 ALC resonances are consistent with the experimental data, indicating exchange rates greater than 10(9) s(-1), placing the rate of interfacial transfer at the diffusion limit.

  14. Antimicrobial activity of a food-grade fully dilutable microemulsion against Escherichia coli and Staphylococcus aureus.

    PubMed

    Zhang, Hui; Shen, Yan; Weng, Peifang; Zhao, Guoqun; Feng, Fengqin; Zheng, Xiaodong

    2009-11-15

    Microemulsions are colloidal nanodispersions of oil and water stabilized by an interfacial film of surfactant molecules, typically in conjunction with a cosurfactant. There is a limited number of reports in the literature on microemulsion use for antimicrobial purposes. The physicochemical characterization of a food-grade fully dilutable microemulsion system with glycerol monolaurate (GML) as oil, organic acids as cosurfactant, Tween 80 as surfactant, and the antimicrobial activities against Escherichia coli and Staphylococcus aureus have been studied in this paper. The influence of organic acids on oil solubilization was clearly reflected in the phase behavior of these systems. Propionic acid demonstrated the greatest capability to improve the oil solubilization among the tested linear and nonlinear chain organic acids and contributed to the formation of U-type microemulsion systems. One microemulsion formulation with an average particle size of 8nm was selected, the composition is GML/propionic acid/Tween 80/water=3:9:8:12. The kinetics of killing experiments demonstrated that the undiluted microemulsion caused a complete loss of viability of E. coli or S. aureus cells in 1min and still had effective bactericidal effects even when diluted, more than 99% viable E. coli cells were killed within 15min and a complete loss of viability was achieved at 45min while more than 99% viable S. aureus cells were killed within 30min and a complete loss of viability was achieved at 60min in the presence of the 10-fold diluted microemulsion. The fast killing kinetics of the ten-fold serial dilutions of microemulsions were in good agreement with the mode of action studies, indicating that the interaction between the antimicrobial microemulsions and bacterial membranes significantly decreased the bacterial cell surface hydrophobicity and induced the quick release of 260nm absorbing materials. This work suggests the potential use of food-grade fully dilutable microemulsions for

  15. Development of microemulsions for ocular delivery.

    PubMed

    Gautam, Nivedita; Kesavan, Karthikeyan

    2017-03-01

    Microemulsions (MEs) are thermodynamic stable dispersion of oily phase and aqueous phase stabilized by surfactants and co-surfactants, and are a small droplet size of less than 100 nm. MEs are appropriate systems for ocular drug delivery because they improve ocular drug retention, extended duration of action, high ocular absorption, permeation of loaded drugs and effortlessness of preparation and administration. This review is an effort to summarize the recent development in the area of MEs, self-emulsifying drug delivery systems, which are examined in relation to their uses in ocular drug delivery. The noteworthy patent, toxicity and stability issues related to these ME systems are also explored here.

  16. Crystallization using reverse micelles and water-in-oil microemulsion systems: the highly selective tool for the purification of organic compounds from complex mixtures.

    PubMed

    Kljajic, Alen; Bester-Rogac, Marija; Klobcar, Andrej; Zupet, Rok; Pejovnik, Stane

    2013-02-01

    The active pharmaceutical ingredient orlistat is usually manufactured using a semi-synthetic procedure, producing crude product and complex mixtures of highly related impurities with minimal side-chain structure variability. It is therefore crucial for the overall success of industrial/pharmaceutical application to develop an effective purification process. In this communication, we present the newly developed water-in-oil reversed micelles and microemulsion system-based crystallization process. Physiochemical properties of the presented crystallization media were varied through surfactants and water composition, and the impact on efficiency was measured through final variation of these two parameters. Using precisely defined properties of the dispersed water phase in crystallization media, a highly efficient separation process in terms of selectivity and yield was developed. Small-angle X-ray scattering, high-performance liquid chromatography, mass spectrometry, and scanning electron microscopy were used to monitor and analyze the separation processes and orlistat products obtained. Typical process characteristics, especially selectivity and yield in regard to reference examples, were compared and discussed. Copyright © 2012 Wiley Periodicals, Inc.

  17. [Study on Chinese herbs' volatile oil micro-emulsions by means of pseudo-ternary phase diagram].

    PubMed

    Yang, Meng-Meng; Zhang, Yan; Liu, Xin-You; Zhang, Ting-Ting; Liu, Mei

    2011-08-01

    To optimize the formulation of Chinese herbs' volatile oil micro emulsion. Sreened the formulation of blank micro-emulsion and the formulation of micro-emulsion contained volatile oil by means of pseudo-ternary phase diagram. System of isopropyl myristate, polyoxyethylene hydrogenated castor oil, absolute ethyl alcohol and water could formed the largest area of micro-emulsion. The optimal formulation of micro-emulsion contained volatile oil was: volatile oil consisted of 2.852%, isopropyl myristate 6.65%, polyoxyethylene hydrogenated castor oil 30.42%, absolute ethyl alcohol 7.605% and water 52.47%. Using pseudo-ternary phase diagram to optimize the formulation of Chinese herbs' micro-emulsion is scientific and feasible. The volatile oil's solubility is also increased by made of oil-in-water type micro-emulsion and insured the stability.

  18. Effect of temperature on the enthalpies of formation of water- o-xylene-Triton X-100 microemulsions

    NASA Astrophysics Data System (ADS)

    Batov, D. V.; Kartsev, V. N.; Shtykov, S. N.

    2013-03-01

    Enthalpies of solution for water- o-xylene-Triton X-100 (TX-100) microemulsions and their components in 2-propanol are determined thermochemically at 288.15, 298.15, and 313.15 K. Enthalpies of formation for the microemulsions are calculated using a thermochemical cycle. It is shown that the enthalpies of formation are negative and fall in moving from water/oil microemulsions to oil/water microemulsions. The obtained data show that strong molecular interactions between components in the investigated systems favor the formation of thermodynamically stable microemulsions. It is concluded that the spontaneous formation of the microemulsions can be due to both the entropy and enthalpy contributions to the change in free energy.

  19. Antipsoriatic microemulsion gel formulations for topical drug delivery of babchi oil (Psoralea corylifolia).

    PubMed

    Ali, J; Akhtar, N; Sultana, Y; Baboota, S; Ahuja, A

    2008-05-01

    The aim of this study was to investigate and evaluate a microemulsion gel-based system of babchi oil (Psoralea corylifolia) for the treatment of psoriasis, which could provide improved permeation of the drug through the skin and increased patient compliance. Babchi oil is used because its chief constituent psoralen is a photoactive furocoumarin that binds to DNA when exposed to UV light to form photoproducts with pyrimidine base. This action inhibits DNA synthesis and causes decrease in cell proliferation. Moreover, babchi oil, in addition to providing psoralen, also acts as an oily phase for microemulsion system. The presence of surfactant and cosurfactant increases the permeation. On the basis of qualitative and quantitative estimation of all eight brands of babchi oil, Bakuchi Tail was selected for microemulsion formulation. Microemulsions were prepared by aqueous phase-titration method. Pseudoternary phase diagrams were constructed for the identification of microemulsion existence zones. Prepared microemulsions were subjected to different thermodynamic stability tests and characterized for droplet size, viscosity and refractive index. In vitro skin permeation of babchi oil through rat abdominal skin was determined by the Franz diffusion cell. The in vitro skin permeation profile of formulation F2, which consisted of 1.67% v/v of babchi oil, 8.33% v/v of oleic acid, S(mix) 55% v/v of Tween 80 Transcutol-P (S/Co ratio 1:1) and 35% v/v of distilled water, was significant when compared with other microemulsion formulations (p < 0.05). Formulation F2 was converted into microemulsion gel by adding 1% Carbopol-940 and coded as MGF2. Formulation MGF2 was selected for its in vivo antiinflammatory effects determined by footpad edema. The results suggested that microemulsion gel is a potential vehicle for improved topical delivery of psoralen and that microemulsion gels are potential vehicles for improved topical delivery of babchi oil. Copyright 2008 Prous Science, S

  20. Analysis of phase diagram and microstructural transitions in an ethyl oleate/water/Tween 80/Span 20 microemulsion system using high-resolution ultrasonic spectroscopy.

    PubMed

    Hickey, Sinead; Hagan, Sue A; Kudryashov, Evgeny; Buckin, Vitaly

    2010-03-30

    High-resolution ultrasonic spectroscopy was applied to analyse a pseudo-ternary phase diagram for a mixture consisting of water/ethyl oleate/Tween 80 and Span 20 at 25 degrees C. The measured changes in the ultrasonic velocity and attenuation with concentration of water in oil/surfactants mixtures showed several, well defined stages and transitions between them, which allowed construction of an 'ultrasonic' phase diagram. Quantitative analysis of the ultrasonic parameters enabled characterisation of various phases (microemulsion, liquid crystals and pseudo-bicontinuous) as well as evaluation of the state of the water and particle size in microemulsion phase.

  1. Aqueous phase microemulsions employing alkyl glucamide surfactants with chlorinated hydrocarbons

    SciTech Connect

    Arenas, E.; Baran, J.R. Jr.; Pope, G.A.

    1995-12-31

    This paper summarizes experiments on nonionic surfactants for electrolyte-free aquifer remediation of chlorocarbon contaminants. Various combinations of linear and branched alkylglucamides succeeded in producing Winsor Type I and III microemulsions at room temperature with various chlorinated hydrocarbons with little or no added electrolyte. Solubilization parameters at 0 and 0.1% NaCl were determined for the surfactant solutions. In comparing these two values, the solubilization parameter shows no definite trend of increasing as had been previously noted. There is no apparent explanation for this anomaly, except that operating at 0% NaCl may not be governed by the same rules that apply to systems with an electrolyte. A class of nonionic surfactants that produce aqueous phase microemulsions with no electrolyte and Winsor III middle phase microemulsions was identified.

  2. Structure of reverse microemulsion-templated metal hexacyanoferrate nanoparticles

    PubMed Central

    2012-01-01

    The droplet phase of a reverse microemulsion formed by the surfactant cetyltrimethylammonium ferrocyanide was used as a matrix to synthesize nanoparticles of nickel hexacyanoferrate by adding just a solution of NiCl2 to the microemulsion media. Dynamic light scattering and small-angle neutron scattering measurements show that the reverse microemulsion droplets employed have a globular structure, with sizes that depend on water content. Transmission electron microscopy and electron diffraction are used to obtain information about the structure of the synthesized nanoparticles. The results show that the size and shape of the coordination compound nanoparticles correspond with the size and shape of the droplets, suggesting that the presented system constitutes an alternative method of the synthesis of metal hexacyanoferrate nanoparticles. PMID:22264404

  3. High accuracy NMR chemical shift corrected for bulk magnetization as a tool for structural elucidation of microemulsions. Part 2 - Anionic and nonionic dilutable microemulsions.

    PubMed

    Hoffman, Roy E; Darmon, Eliezer; Aserin, Abraham; Garti, Nissim

    2016-02-01

    In our previous report we suggested a new analytical tool, high accuracy NMR chemical shift corrected for bulk magnetization as a supplementary tool to study structural transitions and droplet size and shape of dilutable microemulsions. The aim of this study was to show the generality of this technique and to demonstrate that in almost any type of microemulsion this technique provides additional valuable structural information. The analysis made by the technique adds to the elucidation of some structural aspects that could not be clearly determined by other classical techniques. Therefore, in this part we are extending the study to three additional systems differing in the type of oil phase (toluene and cyclohexane), the nature of the surfactants (anionic and nonionic), and other microemulsion characteristics. We studied sodium dodecyl sulfate (SDS)-based anionic microemulsions with different oils and a nonionic microemulsion based on Tween 20 as the surfactant and toluene as the oil phase. All the microemulsions were fully dilutable with water. We found that the change in the slope of chemical shift against dilution reflects phase transition points of the microemulsion (O/W, bicontinuous, W/O). Chemical shift changes were clearly observed with the transition between spherical and non-spherical (wormlike, etc.) droplet shapes. We compared the interaction of cyclohexane and toluene and used the anisotropic effect of toluene's ring current to determine its preferred orientation relative to SDS. Chemical shifts of the microemulsion components are therefore a useful addition to the arsenal of techniques for characterizing microemulsions. Copyright © 2014 Elsevier Inc. All rights reserved.

  4. Chemical and Photochemical Reactivity in Microemulsions and Waterless Microemulsions.

    DTIC Science & Technology

    1988-02-10

    Cl nBuOH microemulsions (CH3)2 A., ’Y B A’ B H 2 0 CH612 Figure 1 H20 C6H12 The source of H202 is the sodium perborate added to the different micro...important difference between sodium perborate and microemulsions containing H202 is that the former does not need basic pH. Otherwise, the reactions are...faster with ammonium salt, particularly in the regions A and A’ (figure 1). 1) Sodium perborate and phenylsufide Neither phenylsufone nor

  5. Applications of NMR in the characterization of pharmaceutical microemulsions.

    PubMed

    Hathout, Rania M; Woodman, Timothy J

    2012-07-10

    Microemulsions have successfully proven themselves as useful vehicles for drugs through the different routes of administration because they can confer on drugs greater water solubility and bioavailability. The ability to understand the structural aspects of these important drug delivery systems is essential to the progress of this science. The use of NMR techniques in pharmaceutical and drug delivery science is increasing especially in the characterization field. This review demonstrates the major and novel NMR methods and techniques used in understanding and characterizing the different microemulsion components, types and structures. Copyright © 2012 Elsevier B.V. All rights reserved.

  6. Microemulsions: A qualitative thermodynamic approach

    SciTech Connect

    Kahlweit, M.; Strey, R.; Busse, G. )

    1990-05-17

    Microemulsions, that is, stable colloidal dispersions of water and nonpolar solvents stabilized by amphiphiles, are of growing interest in research and industry. The phase behavior of the multicomponent mixture is essentially determined by the features of corresponding binary mixtures. The efficiency of an amphiphile in solubilizing the solvents reaches its maximum in the temperature interval in which the mixture separates into three coexisting liquid phases. The domain size of the dispersion is determined by the interfacial tension between the aqueous and the oil-rich phase in the presence of a saturated monolayer. Because the interfacial tension reaches its minimum in the three-phase interval and, furthermore, decreases with increasing amphiphilicity, the transition from weakly structured solutions to microemulsions is gradual. It is, therefore, suggested that microemulsions be defined as stable colloidal dispersions of domains sufficiently large for the dispersed solvent to exhibit the properties as, e.g., the dielectric number of a bulk phase.

  7. Mesoscopic modelling of frustration in microemulsions.

    PubMed

    Duvail, Magali; Dufrêche, Jean-François; Arleth, Lise; Zemb, Thomas

    2013-05-21

    The swelling behaviour of water-oil microemulsions - considering a surfactant layer between oil and water - has been studied using a two level-cuts Gaussian random field approach based on the Helfrich formalism. Microstructures and scattering properties of microemulsions have been calculated for different amounts of oil (and water) for flexible and rigid microemulsions. When the stiffness, the spontaneous curvature of the interfacial film, and the surface to volume ratio of the immiscible fluids are varied, the microemulsion topology and morphology change in order to minimize the microemulsion free energy. Our simulations point out a change in the microemulsion morphology as a function of the surfactant film rigidity and the composition of oil, water and the surfactant. Locally lamellar structures are found for rigid microemulsions, whereas for more flexible ones, the connected-droplet and/or bicontinuous structures are preferred. Furthermore, we show that the microemulsion swelling versus the volume fraction gives a specific signature of the microemulsion microstructure. This allows for discriminating between different types of microemulsions: flexible, frustrated and unfrustrated (close to bi-liquid foams), and connected structures as molten hexagonal and cubic phases. The universal swelling behaviour is compared to different analytic expressions of Disordered Open Connected (DOC) models for the microemulsion swelling versus the volume fraction.

  8. Protein extraction into the bicontinuous microemulsion phase of a Water/SDS/pentanol/dodecane winsor-III system: Effect on nanostructure and protein conformation.

    PubMed

    Hayes, Douglas G; Ye, Ran; Dunlap, Rachel N; Cuneo, Matthew J; Pingali, Sai Venkatesh; O'Neill, Hugh M; Urban, Volker S

    2017-09-07

    Bicontinuous microemulsions (BμEs), consisting of water and oil nanodomains separated by surfactant monolayers of near-zero curvature, are potentially valuable systems for purification and delivery of biomolecules, for hosting multiphasic biochemical reactions, and as templating media for preparing nanomaterials. We formed Winsor-III systems by mixing aqueous protein and sodium dodecyl sulfate (SDS) solutions with dodecane and 1-pentanol (cosurfactant) to efficiently extract proteins into the middle (BμE) phase. Bovine serum albumin (BSA) and cytochrome c partitioned to the BμE phase at 64% and 81% efficiency, respectively, producing highly concentrated protein solutions (32 and 44gL(-1), respectively), through release of water and oil from the BμEs. Circular dichroism spectroscopic analysis demonstrated that BSA underwent minor secondary structural changes upon incorporation into BμEs, while the secondary structure of cytochrome c and pepsin underwent major changes. Small-angle x-ray scattering (SAXS) results show that proteins promoted an increase of the interfacial fluidity and surface area per volume for the BμE surfactant monolayers, and that each protein uniquely altered self-assembly in the Winsor-III systems. Cytochrome c partitioned via electrostatic attractions between SDS and the protein's positively-charged groups, residing near the surfactant head groups of BμE monolayers, where it decreased surfactant packing efficiency. BSA partitioned through formation of SDS-BSA complexes via hydrophobic and electrostatic attractive interactions. As the BSA-SDS ratio increased, complexes' partitioning favored BμEs over the oil excess phase due to the increased hydrophilicity of the complexes. This study demonstrates the potential utility of BμEs to purify proteins and prepare nanostructured fluids possessing high protein concentration. Copyright © 2017 Elsevier B.V. All rights reserved.

  9. Rheology and flow-induced structure in a polystyrene-polyisoprene biocontinuous microemulsion

    NASA Astrophysics Data System (ADS)

    Brinker, Kristin

    2005-03-01

    Polymer bicontinuous microemulsions are blends of immiscible polymers compatibilized with diblock copolymer in such a way as to produce an equilibrium interconnected morphology. Previous experiments on a microemulsion of poly(ethyl ethylene) (PEE) and poly(dimethyl siloxane) (PDMS) have revealed a fascinating array of rheological and flow-induced structural phenomena. We have prepared a new microemulsion sample from low molecular weight polystyrene (PS) and polyisoprene (PI) and their corresponding block copolymer. Despite the fact that the constituent homopolymers are strictly Newtonian, the microemulsion exhibits substantial viscoelasticity associated with flow-induced deformation of the supramolecular organization. The linear viscoelastic properties of the PS-PI microemulsion closely resemble those previously found in the PEE- PDMS system. Under even fairly weakly nonlinear flow conditions, the PS-PI microemulsion exhibits a flow-induced phase transition. In situ small-angle x-ray scattering is used to probe both the flow-induced deformation of the equilibrium microemulsion structure as well as the onset and development of a flow-induced bulk phase separation. The higher suscepibility of the PS-PI system to phase separation may be related to a higher viscosity contrast between its constituents and those in the previously studied PEE-PDMS system.

  10. Formulation, characterization, and clinical evaluation of microemulsion containing clotrimazole for topical delivery.

    PubMed

    Hashem, Fahima M; Shaker, Dalia S; Ghorab, Mohamed Khalid; Nasr, Mohamed; Ismail, Aliaa

    2011-09-01

    The objective of the present study was to formulate and evaluate microemulsion systems for topical delivery of clotrimazole (CTM). The solubility of CTM in various oils was determined to select the oil phase of the microemulsion systems. Pseudoternary phase diagrams were constructed to identify the area of microemulsion existence. Five CTM microemulsion formulations (M1-M5) were prepared and evaluated for their thermodynamic stability, pH, refractive index, droplet size, viscosity, and in vitro release across cellulose membrane. Among the prepared microemulsion formulations, M3 (lemon oil/Tween 80/n-butanol/water) and M4 (isopropyl myristate/Tween 80/n-butanol/water) microemulsion systems were found to be promising according to their physical properties and CTM cumulative percentage release. Gel form of M3 and M4 were prepared using 1% Carbopol 940 as the hydrogel matrix. Both formulations were evaluated in the liquid and gel forms for drug retention in the skin in comparison to the marketed CTM topical cream and their stability examined after storage at 40°C for 6 months. Microemulsion formulations achieved significantly higher skin retention for CTM over the CTM cream. Stability studies showed that M4 preparations were more stable than M3. The in vitro anti-fungal activity of M4 against Candida albicans was higher than that of the conventional cream. Moreover, clinical evaluation proved the efficacy and tolerability of this preparation in the treatment of various topical fungal infections.

  11. Microemulsions for Colorectal Cancer Treatments. General Considerations and Formulation of Methotrexate.

    PubMed

    Flores, Sergio E; Rial-Hermida, M Isabel; Ramirez, Jorge C; Pazos, Alejandro; Concheiro, Angel; Alvarez-Lorenzo, Carmen; Peralta, René D

    2016-01-01

    Microemulsions combine the advantages of emulsions with those of nanocarriers, overcoming the stability problems of the former and providing facile scalable systems with compartments adequate for high drug loadings. Recently, microemulsions are gaining attention in the formulation of anticancer drugs not only for topical treatment, but also for systemic delivery as well as for the development of theranostic systems. The aim of this paper is two-fold. First, an updated review about general features, preparation, characterization and pharmaceutical applications, with a special focus on colorectal cancer, is provided. Second, a case study of formulation of methotrexate in microemulsions is presented. Various essential oils (menthol, trans-anethole, α-tocopherol) and surfactants (TPGS-1000, Maxemul 6112, Noigen RN-20) were investigated for the preparation of o/w microemulsions for the delivery of methotrexate, and the ability of methotrexate-loaded microemulsions to inhibit cancer cell growth was then evaluated. Disregarding the surfactants used, menthol and trans-anethole led to cytotoxic microemulsions, whereas α-tocopherol based-formulations induced cell proliferation. These findings highlight the role that the oily component may play in the efficacy and safety of the microemulsions.

  12. Microemulsions based on paeonol-menthol eutectic mixture for enhanced transdermal delivery: formulation development and in vitro evaluation.

    PubMed

    Wang, Wenping; Cai, Yaqin; Liu, Yanhua; Zhao, Yunsheng; Feng, Jun; Liu, Chen

    2017-09-01

    In this work, microemulsion-based gels were prepared for transdermal delivery of paeonol. Microemulsions containing eutectic mixtures of paeonol and menthol were developed. The obtained microemulsions were evaluated for particle size, viscosity and physical stability. The selected microemulsions were incorporated into Carbopol gels. Drug crystallization behavior during a short-term storage was compared and in vitro permeation and deposition study were conducted on mouse skin. Results showed that the eutectic liquids of paeonol and menthol at all ratio (6:4, 5:5 and 4:6) could form microemulsions but with significantly different physical characteristics. As the ratio of paeonol increased, the prepared microemulsions exhibited larger droplet size, higher viscosity and quicker crystal growth. Microemulsion containing paeonol and menthol at a ratio of 4:6 possessed the smallest size of 27 nm. Accordingly, the related gel showed better physical stability during 10 days of storage, as well as the highest percent of drug deposition (111.8 μg/cm(2)) and steady-state flux (0.3 μg/cm(2) h). These results suggested that the microemulsion formulation is a preferable approach for enhanced skin permeation, and the microemulsion based on drug-menthol eutectic mixture might be used as a potential transdermal delivery system for better therapeutic efficacy.

  13. Thermostability of Cromobacterium viscosum lipase in AOT/isooctane reverse micelle.

    PubMed

    Talukder, M M R; Zaman, M M; Hayashi, Y; Wu, J C; Kawanishi, T

    2007-04-01

    The thermostability of Cromobacterium viscosum lipase (EC 3.1.1.3) entrapped in AOT (sodium bis-[2-ethylhexyl] sulfosuccinate) reverse micelles was increased by the addition of short-chain polyethylene glycol (PEG 400). Two different approaches were considered: (1) the determination of half-life time and (2) the mechanistic analysis of deactivation kinetics. The half-life of lipase entrapped in AOT/isooctane reverse micelles with PEG 400 at 60 degrees C was 28 h, ninefold higher than that in reverse micelles without PEG 400. The lipase entrapped in both reverse micellar systems followed a series-type deactivation mechanism involving two first-order steps. The deactivation constant for the first step at 60 degrees C in PEG containing reverse micelles was 0.055 h!1, 11-fold lower than that in reverse micelles without PEG, whereas it remained almost constant for the second step. The inactivation energy of the lipase entrapped in reverse micelles with and without PEG 400 was 88.12 and 21.97 kJ/mol, respectively.

  14. Determination of the acid dissociation constant of bromocresol green and cresol red in water/AOT/isooctane reverse micelles by multiple linear regression and extended principal component analysis.

    PubMed

    Caselli, Maurizio; Mangone, Annarosa; Paolillo, Paola; Traini, Angela

    2002-01-01

    The pKa of 3',3",5',5"tetrabromo-m-cresolsulfonephtalein (Bromocresol Green) and o-cresolsulphonephtalein (Cresol Red) was spectrophotometrically measured in a water/AOT/isooctane microemulsion in the presence of a series of buffers carrying different charges at different water/surfactant ratios. Extended Principal Component Analysis was used for a precise determination of the apparent pKa and of the spectra of the acid and base forms of the dye. The apparent pKa of dyes in water-in-oil microemulsions depends on the charge of the acid and base forms of the buffers present in the water pool. Combination with multiple linear regression increases the precision. Results are discussed taking into account the profile of the electrostatic potential in the water pool and the possible partition of the indicator between the aqueous core and the surfactant. The pKa corrected for these effects are independent of w0 and are close to the value of the pKa in bulk water. On the basis of a tentative hypothesis it is possible to calculate the true pKa of the buffer in the pool.

  15. Measuring Size, Size Distribution, and Polydispersity of Water-in-Oil Microemulsion Droplets using Fluorescence Correlation Spectroscopy: Comparison to Dynamic Light Scattering.

    PubMed

    Khan, Mohammad Firoz; Singh, Moirangthem Kiran; Sen, Sobhan

    2016-02-11

    Water-in-oil microemulsion droplets (MEDs) are thermodynamically stable supramolecular structures formed in a mixture of water and oil, stabilized by surfactant layer. Here we use fluorescence correlation spectroscopy (FCS) to measure the diffusion, and the size, size distribution, and polydispersity of MEDs prepared in ternary mixtures of water/oil/sodium bis(2-ethylhexyl) sulfosuccinate (AOT) in heptane, isooctane, and nonane at (near) single droplet level. We compare FCS data directly to dynamic light scattering (DLS) data, which shows that the optical matching point (OMP) conditions of MEDs in different oils (where excess optical polarizability of droplets vanish) severely influence DLS data, while FCS extracts the accurate size, size distribution, and polydispersity of AOT-MEDs in all three oils. This suggests that extreme precaution must be taken in acquiring and explaining DLS data of MEDs in solution. FCS data show nearly identical W0-dependent (peak) size variations of AOT-MEDs in all three oils, though a subtle increase in (average) polydispersity of droplets is observed with increase in carbon chain length of oils. Establishing the accuracy of FCS data for AOT-MEDs, we further apply FCS to measure the size parameters of MEDs prepared in a quaternary mixture of water/oil/cetyltrimethylammonium bromide (CTAB)/1-butanol in hexane, heptane, and isooctane. Unlike AOT-MEDs, FCS data show substantial effect of added cosurfactant (1-butanol) and external oil on size, size distribution and polydispersity of quaternary CTAB-MEDs. Analysis of size distributions reveals large variation of polydispersity which possibly indicates the existence of larger shape heterogeneity, together with size heterogeneity, of CTAB-MEDs compared to AOT-MEDs in solution.

  16. Cremophor RH40-PEG 400 microemulsions as transdermal drug delivery carrier for ketoprofen.

    PubMed

    Ngawhirunpat, Tanasait; Worachun, Narumon; Opanasopit, Praneet; Rojanarata, Theerasak; Panomsuk, Suwannee

    2013-01-01

    The aim of this study was to prepare novel microemulsion for transdermal drug delivery of ketoprofen (KP). The microemulsion composed of ketoprofen as model drug, isopropyl myristate (IPM) as oil phase, surfactant mixture consisting of polyoxyl 40 hydrogenated castor oil (Cremophor RH40) as surfactant and polyethylene glycol 400 (PEG400) as co-surfactant at the ratio 1:1, and water were prepared. The viscosity, droplet size, pH, conductivity of microemulsions, and skin permeation of KP through shed snake skin were evaluated. The particle size, pH, viscosity and conductivity of microemulsions were in the range of 114-210 nm, 6.3-6.8, 124-799 cPs and 1-45 µS/cm, respectively. The ratio of IPM, and surfactant mixture played the important role in the skin permeation of KP microemulsions. As the amount of surfactant mixture and IPM increased, the skin permeation of KP decreased. The formulation composed of 30% IPM, 45% surfactant mixture and 25% water showed the highest skin permeation flux. The incorporation of terpenes in the 2.5% KP microemulsions resulted in significant enhancement in skin permeation of KP. The rank order of enhancement ratio for skin permeation enhancement of terpenes was α-pinene > limonene > menthone. The results suggested that the novel microemulsion system containing IPM, water, Cremophor RH40:PEG400 and terpenes can be applied for using as a transdermal drug delivery carrier.

  17. Influence of surfactin on physical and oxidative stability of microemulsions with docosahexaenoic acid.

    PubMed

    He, Zhenhong; Zeng, Weiwei; Zhu, Xiaoyu; Zhao, Haizhen; Lu, Yingjian; Lu, Zhaoxin

    2017-03-01

    Docosahexaenoic acid (DHA), one of the most important omega-3 polyunsaturated fatty acids (PUFAs), shows significant health benefits for human beings. In order to stabilize nutrients like DHA, microemulsion is normally used through the addition of surfactant, and surfactin as a natural peptide biosurfactant shows strong surface activity. In this study, we investigated the effects of surfactin on the stability of docosahexaenoic acid single cell oil (DHASCO) microemulsions. The microemusion region was significantly increased with elevated surfactin concentration from 0 to 0.2mmol/L, and reached a maximum. The o/w region of DHASCO microemulsion could significantly increase and the diameters of microemulsion particles were reduced from 140 to 15nm after addition of 0.2mmol/L surfactin into emulsion system. Generally, the physical and anti-oxidation stability of the o/w DHASCO microemulsion with surfactin was highly enhanced. DHA oxidation in microemulsion with surfaction was significantly reduced even stored at 37°C for 60days as compared to non-surfactin. The excellent properties of microemulsion with surfactin could be useful in functional food and medicine.

  18. Shape transitions in supercritical CO2 microemulsions induced by hydrotropes.

    PubMed

    James, Craig; Hatzopoulos, Marios Hopkins; Yan, Ci; Smith, Gregory N; Alexander, Shirin; Rogers, Sarah E; Eastoe, Julian

    2014-01-14

    The ability to induce morphological transitions in water-in-oil (w/o) and water-in-CO2 (w/c) microemulsions stabilized by a trichain anionic surfactant 1,4-bis(neopentyloxy)-3-(neopentyloxycarbonyl)-1,4-dioxobutane-2-sulfonate (TC14) with simple hydrotrope additives has been investigated. High-pressure small-angle neutron scattering (SANS) has revealed the addition of a small mole fraction of hydrotrope can yield a significant elongation in the microemulsion water droplets. For w/o systems, the degree of droplet growth was shown to be dependent on the water content, the hydrotrope mole fraction, and chemical structure, whereas for w/c microemulsions a similar, but less significant, effect was seen. The expected CO2 viscosity increase from such systems has been calculated and compared to related literature using fluorocarbon chain surfactants. This represents the first report of hydrotrope-induced morphology changes in w/c microemulsions and is a significant step forward toward the formation of hydrocarbon worm-like micellar assemblies in this industrially relevant solvent.

  19. Antinociceptive activity of Delta9-tetrahydrocannabinol non-ionic microemulsions.

    PubMed

    Lazzari, P; Fadda, P; Marchese, G; Casu, G L; Pani, L

    2010-06-30

    Delta(9)-Tetrahydrocannabinol (Delta(9)-THC), the major psychoactive constituent of Cannabis sativa L., has been widely studied for its potential pharmaceutical application in the treatment of various diseases and disturbs. This sparingly soluble terpeno-phenolic compound is not easy to handle and to be formulated in pharmaceutical preparations. The aim of this work was to develop a stable aqueous Delta(9)-THC formulation acceptable for different ways of administration, and to evaluate the therapeutic properties of the new Delta(9)-THC based preparation for pain treatment. Due to the thermodynamic stability and advantages of microemulsion based systems, the study was focused on the identification of aqueous microemulsion based systems containing Delta(9)-THC. Oil in water Delta(9)-THC microemulsions were individuated through phase diagrams construction, using the non-ionic surfactant Solutol HS15, being this surfactant acceptable for parenteral administration in human. A selected microemulsion samples containing 0.2 wt% of Delta(9)-THC, stable up to 52 degrees C, was successfully assayed on animal models of pain. Significant antinociceptive activity has been detected by both intraperitoneal and intragastric administration of the new Delta(9)-THC pharmaceutical preparation. The effect has been highlighted in shorter time if compared to a preparation of the same active principle based on previously reported conventional preparation. 2010 Elsevier B.V. All rights reserved.

  20. Studies on the kinetics of killing and the proposed mechanism of action of microemulsions against fungi.

    PubMed

    Al-Adham, Ibrahim S I; Ashour, Hana; Al-Kaissi, Elham; Khalil, Enam; Kierans, Martin; Collier, Phillip J

    2013-09-15

    Microemulsions are physically stable oil/water clear dispersions, spontaneously formed and thermodynamically stable. They are composed in most cases of water, oil, surfactant and cosurfactant. Microemulsions are stable, self-preserving antimicrobial agents in their own right. The observed levels of antimicrobial activity associated with microemulsions may be due to the direct effect of the microemulsions themselves on the bacterial cytoplasmic membrane. The aim of this work is to study the growth behaviour of different microbes in presence of certain prepared physically stable microemulsion formulae over extended periods of time. An experiment was designed to study the kinetics of killing of a microemulsion preparation (17.3% Tween-80, 8.5% n-pentanol, 5% isopropyl myristate and 69.2% sterile distilled water) against selected test microorganisms (Candida albicans, Aspergillus niger, Schizosaccharomyces pombe and Rhodotorula spp.). Secondly, an experiment was designed to study the effects of the microemulsion preparation on the cytoplasmic membrane structure and function of selected fungal species by observation of 260 nm component leakage. Finally, the effects of the microemulsion on the fungal membrane structure and function using S. pombe were studied using transmission electron microscopy. The results showed that the prepared microemulsions are stable, effective antimicrobial systems with effective killing rates against C. albicans, A. niger, S. pombe and Rhodotorula spp. The results indicate a proposed mechanism of action of significant anti-membrane activity, resulting in the gross disturbance and dysfunction of the cytoplasmic membrane structure which is followed by cell wall modifications, cytoplasmic coagulation, disruption of intracellular metabolism and cell death. Copyright © 2013 Elsevier B.V. All rights reserved.

  1. Form fluctuations of polymer loaded spherical microemulsions studied by neutron scattering and dielectric spectroscopy

    SciTech Connect

    Kuttich, B. Stühn, B.; Falus, P.; Grillo, I.

    2014-08-28

    We investigate the structure and shell dynamics of the droplet phase in water/AOT/octane microemulsions with polyethyleneglycol (M{sub W} = 1500) molecules loaded in the droplets. Size and polydispersity of the droplets is determined with small angle X-ray scattering and small angle neutron scattering experiments. Shell fluctuations are measured with neutron spin echo spectroscopy and related to the dynamic percolation seen in dielectric spectroscopy. Shell fluctuations are found to be well described by the bending modulus of the shell and the viscosities inside and outside the droplets. Addition of the polymer decreases the modulus for small droplets. For large droplets the opposite is found as percolation temperature shifts to higher values.

  2. Hygroscopic growth and deliquescence of NaCl nanoparticles coated with surfactant AOT.

    PubMed

    Alshawa, Ahmad; Dopfer, Otto; Harmon, Christopher W; Nizkorodov, Sergey A; Underwood, Joelle S

    2009-07-02

    Aerosolized nanoparticles of NaCl coated with variable amounts of surfactant AOT were generated by electrospraying AOT/NaCl aqueous solutions, followed by neutralizing and drying the resulting particles. A tandem differential mobility analyzer was used to select a narrow size distribution of particles with mobility equivalent diameters below 20 nm and monitor their hygroscopic growth as a function of relative humidity. Effects of the particle size and relative amount of surfactant on the hygroscopic growth of NaCl were studied. For pure NaCl nanoparticles, the deliquescence relative humidity (DRH) increased as the particle size was decreased, in full agreement with previous measurements. Below the DRH the NaCl nanoparticles had an equivalent of one-four monolayers of water adsorbed on the surface. The addition of a sub-monolayer AOT coating reduced the DRH and suppressed the hygroscopic growth of the NaCl core. At AOT coverage levels exceeding one monolayer, a clear deliquescence transition was no longer discernible. The Zdanovskii-Stokes-Robinson (ZSR) model failed to predict the observed growth factors of mixed AOT/NaCl nanoparticles reflecting a large contribution of the interfacial interactions between NaCl and AOT to the total free energy of the particles. There were indications that AOT/NaCl nanoparticles prepared by the electrospray aerosol source were enhanced in the relative mass fraction of AOT in comparison with the solution from which they were electrosprayed.

  3. Trend estimates of AERONET-observed and model-simulated AOT percentiles between 1993 and 2013

    NASA Astrophysics Data System (ADS)

    Yoon, Jongmin; Pozzer, Andrea; Chang, Dong Yeong; Lelieveld, Jos

    2016-04-01

    Recent Aerosol Optical thickness (AOT) trend studies used monthly or annual arithmetic means that discard details of the generally right-skewed AOT distributions. Potentially, such results can be biased by extreme values (including outliers). This study additionally uses percentiles (i.e., the lowest 5%, 25%, 50%, 75% and 95% of the monthly cumulative distributions fitted to Aerosol Robotic Network (AERONET)-observed and ECHAM/MESSy Atmospheric Chemistry (EMAC)-model simulated AOTs) that are less affected by outliers caused by measurement error, cloud contamination and occasional extreme aerosol events. Since the limited statistical representativeness of monthly percentiles and means can lead to bias, this study adopts the number of observations as a weighting factor, which improves the statistical robustness of trend estimates. By analyzing the aerosol composition of AERONET-observed and EMAC-simulated AOTs in selected regions of interest, we distinguish the dominant aerosol types and investigate the causes of regional AOT trends. The simulated and observed trends are generally consistent with a high correlation coefficient (R = 0.89) and small bias (slope±2σ = 0.75 ± 0.19). A significant decrease in EMAC-decomposed AOTs by water-soluble compounds and black carbon is found over the USA and the EU due to environmental regulation. In particular, a clear reversal in the AERONET AOT trend percentiles is found over the USA, probably related to the AOT diurnal cycle and the frequency of wildfires.

  4. Biocompatible microemulsions based on limonene: formulation, structure, and applications.

    PubMed

    Papadimitriou, Vassiliki; Pispas, Stergios; Syriou, Stauroula; Pournara, Anastasia; Zoumpanioti, Maria; Sotiroudis, Theodore G; Xenakis, Aristotelis

    2008-04-01

    The preparation of biocompatible (w/o) microemulsions based on R-(+)-limonene, water, and a mixture of lecithin and either 1-propanol or 1,2-propanediol as emulsifiers was considered. The choice of the compositions of the microemulsions used was based on the pseudo-ternary phase diagrams of the four-component system determined at 30 degrees C for different weight ratios of the components. When 1-propanol was considered as co-surfactant, the area of the microemulsion zone was remarkably increased. Interfacial properties and the dynamic structure of the emulsifier's monolayer were studied by electron paramagnetic resonance (EPR) spectroscopy using the spin-labeling technique. The rigidity and polarity of the interface were affected by the nature of the alcohol used as co-surfactant. When 1-propanol was used, the emulsifier's interface was much more flexible, indicating a less tight packing of lecithin molecules than in the case of 1,2-propanediol. In addition, the membrane's polarity was decreased when the diol was added as co-surfactant in the microemulsion system. To evaluate the size of the dispersed aqueous domains as a function of water content and other additives concentration, dynamic light scattering (DLS) measurements were carried out. Radii in the range from 60 to 180 nm were observed when 1-propanol was used as co-surfactant, and the water content varied from 0 to 12% w/w. Electrical conductivity measurements of R-(+)-limonene/lecithin/1-propanol/water microemulsions with increasing weight fractions of water indicated the appearance of a percolation threshold at water content above 4% w/w. Lipase from Rhizomucor miehei was solubilized in the aqueous domains of the biocompatible microemulsions, and the esterification of octanoic, dodecanoic, and hexadecanoic acids with the short-chained alcohols used as co-surfactants for the formulation of microemulsions was studied. The enzyme efficiency was affected by the chain length of the carboxylic acids and the

  5. Toward surfactant-free and water-free microemulsions.

    PubMed

    Fischer, Veronika; Marcus, Julien; Touraud, Didier; Diat, Olivier; Kunz, Werner

    2015-09-01

    It was recently demonstrated that a nano-clustering was present in the monophasic "pre-Ouzo" region of ternary liquid mixtures without surfactants. The goal of this work is to check if this nano-clustering is also present in the surfactant-free and water-free "green" microemulsions glycerol/ethanol/1-octanol and deep eutectic solvent/tetrahydrofurfuryl alcohol/diethyl adipate. The deep eutectic solvents used instead of water were ethylene glycol-choline chloride (molar ratio 4-1) and urea-choline chloride (molar ratio 2-1). To our knowledge this is the first time that deep eutectic solvents were used to formulate microemulsions. The surfactant-free and water-free microemulsions were studied using phase diagrams, dynamic light scattering, and small-angle X-ray scattering. The presence of aggregate fluctuations was demonstrated and they were found to be independent of molecular critical fluctuations, except when approaching the critical point where the critical phenomenon is superimposed to the signal. These structures have similarities to classical microemulsions but, in contrast to them, without having a sharp interface between the non-miscible phases, much as it was the case for systems previously investigated like water/ethanol/oil, where the oil was 1-octanol, fragrance molecules, or mosquito repellents. Copyright © 2015 Elsevier Inc. All rights reserved.

  6. TX-100/water/1-butyl-3-methylimidazolium hexafluorophosphate microemulsions.

    PubMed

    Gao, Yanan; Han, Shuaibing; Han, Buxing; Li, Ganzuo; Shen, Dong; Li, Zhonghao; Du, Jimin; Hou, Wanguo; Zhang, Gaoyong

    2005-06-21

    Both ionic liquids and water are typical green solvents. In this work, the phase behavior of the ternary system consisting of ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate (bmimPF6), TX-100, and water was determined at 25.0 degrees C. The water-in-bmimPF6, bicontinuous, and bmimPF6-in-water microregions of the microemulsions were identified by cyclic voltammetry method using potassium ferrocyanide K4Fe(CN)6 as the electroactive probe. Dynamic light scattering (DLS) and the UV-vis method were used to characterize the microemulsions. It was demonstrated that the hydrodynamic diameter (Dh) of the bmimPF6-in-water microemulsions is nearly independent of the water content but increases with increasing bmimPF6 content due to the swelling of the micelles by the ionic liquid. The UV-vis further confirmed the existence of water domains in the water-in-bmimPF6 microemulsions, and the salt potassium ferricyanide K3Fe(CN)6 could be dissolved in the water domains.

  7. Characterization of potent anticholinesterase plant oil based microemulsion.

    PubMed

    Chaiyana, Wantida; Saeio, Kiattisak; Hennink, Wim E; Okonogi, Siriporn

    2010-11-30

    In the present study, essential oils of three edible Thai plants, Cymbopogon citratus (Gramineae), Citrus hystrix (Rutaceae) and Zingiber cassumunar (Zingiberaceae) were comparatively tested for acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) inhibitory activities using Ellman's colorimetric method. C. citratus oil exhibited the highest activity with IC(50) values of 0.34±0.07μl/ml and 2.14±0.18μl/ml against BChE and AChE activity, respectively. It was further investigated whether microemulsions of this oil could be obtained. The effects of type of surfactant and co-surfactant as well as pH and ionic strength on the phase behavior of the oil/water system were investigated. Brij 97, Triton X-114, Tween 20 and Tween 85 were employed as surfactant whereas ethanol and hexanol were used as cosurfactants. The size analysis, electrical conductivity measurements and cholinesterase inhibition assays were done in selected microemulsion. The results revealed that the type and concentration of surfactant and co-surfactant exhibited a distinct influence on the C. citratus oil microemulsions. Moreover, the inhibitory activities of the microemulsion formulation were remarkable. Copyright © 2010 Elsevier B.V. All rights reserved.

  8. Microemulsion-enhanced remediation of soils contaminated with organochlorine pesticides.

    PubMed

    Zhang, Yanlin; Wong, Jonathan W C; Zhao, Zhenyong; Selvam, Ammaiyappan

    2011-12-01

    Soil contaminated by organic pollutants, especially chlorinated aromatic compounds such as DDT (1,1,1-trichloro-2,2-bis(4-chlorophenyl)ethane), is an environmental concern because of the strong sorption of organochlorine pesticide onto the soil matrix and persistence in the environment. The remediation of organochlorine pesticide contaminated soils through microemulsion is an innovative technology to expedite this process. The remediation efficiency was evaluated by batch experiments through studying the desorption of DDT and hexachlorocyclohexane (y-HCH) and sorption of microemulsion composed of Triton X-100, 1-pentanol and linseed oil in the soil-surfactant-water suspension system. The reduction of desorption efficiency caused by the sorption loss of microemulsion components onto the soil could be corrected by the appropriate adjustment of C/S (Cosurfactant/Surfactant) and O/S (Oil/Surfactant) ratio. The C/S and O/S ratios of 1:2 and 3:20 were suitable to desorb DDT and gamma-HCH from the studied soils because of the lower sorption of Triton X-100 onto the soil. Inorganic salts added in microemulsion increased the pesticides desorption efficiency of pesticides and calcium chloride has a stronger ability to enhance the desorption of DDT than sodium chloride. From the remediation perspective, the balance of surfactant or cosurfactant sorbed to soil and desorption efficiency should be taken into consideration to enhance the remediation of soils contaminated by organochlorine pesticides.

  9. Microemulsion: New Insights into the Ocular Drug Delivery

    PubMed Central

    Hegde, Rahul Rama; Verma, Anurag; Ghosh, Amitava

    2013-01-01

    Delivery of drugs into eyes using conventional drug delivery systems, such as solutions, is a considerable challenge to the treatment of ocular diseases. Drug loss from the ocular surface by lachrymal fluid secretion, lachrymal fluid-eye barriers, and blood-ocular barriers are main obstacles. A number of ophthalmic drug delivery carriers have been made to improve the bioavailability and to prolong the residence time of drugs applied topically onto the eye. The potential use of microemulsions as an ocular drug delivery carrier offers several favorable pharmaceutical and biopharmaceutical properties such as their excellent thermodynamic stability, phase transition to liquid-crystal state, very low surface tension, and small droplet size, which may result in improved ocular drug retention, extended duration of action, high ocular absorption, and permeation of loaded drugs. Further, both lipophilic and hydrophilic characteristics are present in microemulsions, so that the loaded drugs can diffuse passively as well get significantly partitioned in the variable lipophilic-hydrophilic corneal barrier. This review will provide an insight into previous studies on microemulsions for ocular delivery of drugs using various nonionic surfactants, cosurfactants, and associated irritation potential on the ocular surface. The reported in vivo experiments have shown a delayed effect of drug incorporated in microemulsion and an increase in the corneal permeation of the drug. PMID:23936681

  10. Development of the simple and sensitive method for lipoxygenase assay in AOT/isooctane reversed micelles.

    PubMed

    Park, Kyung Min; Kim, Yu Na; Choi, Seung Jun; Chang, Pahn-Shick

    2013-06-01

    In this study, we investigated the possibility of reversed micelles, widely used as an enzyme reactor for lipases, for the determination of lipoxygenase activity. Although it is rapid and simple, reversed micelles have some limitations, such as interference by UV-absorbing materials and surfactant. Lipoxygenase activity in the reversed micelles was determined by reading the absorbance of the lipid hydroperoxidation product (conjugated diene) at 234 nm. Among surfactants and organic media, AOT and isooctane were most effective for the dioxygenation of linoleic acid in reversed micelles. The strong absorbance of AOT in the UV region is a major obstacle for the direct application of the AOT/isooctane reversed micelles to lipoxygenase activity determination. To prevent interference by AOT, we added an AOT removal step in the procedure for lipoxygenase activity determination in reversed micelles. The lipoxygenase activity was dependent on water content, and maximum activity was obtained at an R-value of 10.

  11. Transdermal microemulsions of Glycyrrhiza glabra L.: characterization, stability and evaluation of antioxidant potential.

    PubMed

    Mostafa, Dina M; Ammar, Nagwa M; Abd El-Alim, Sameh H; El-anssary, Amira A

    2014-03-01

    The purpose of the present study is to formulate Glycyrrhiza glabra root and rhizome aqueous ethanolic extract in microemulsion carrier systems intended for transdermal delivery of incorporated antioxidant actives, flavonoids and polyphenols. The results obtained reveal that the microemulsion system ME3 possesses optimum properties regarding drug content (flavonoids and polyphenols), viscosity, pH, particle size and polydispersity index, zeta potential, stability, permeation of actives and hence possesses high in vitro and ex vivo antioxidant efficacy. These results indicate also that this microemulsion shows approximately 13-fold higher ex vivo antioxidant capacity compared with the liquorice extract solution. In addition, the proposed microemulsion is simple to dispense, cost effective and provides high patient compliance and convenience because of simple topical application and avoidance of non-comfortable oral or parenteral administration.

  12. Formation of flavor oil microemulsions, nanoemulsions and emulsions: influence of composition and preparation method.

    PubMed

    Rao, Jiajia; McClements, David Julian

    2011-05-11

    This study aimed to establish conditions where stable microemulsions, nanoemulsions or emulsions could be fabricated from a nonionic surfactant (Tween 80) and flavor oil (lemon oil). Different colloidal dispersions could be formed by simple heat treatment (90 °C, 30 min) depending on the surfactant-to-oil ratio (SOR): emulsions (r > 100 nm) at SOR < 1; nanoemulsions (r < 100 nm) at 1 < SOR < 2; microemulsions (r < 10 nm) at SOR > 2. Turbidity, electrical conductivity, shear rheology, and DSC measurements suggested there was a kinetic energy barrier in the oil-water-surfactant systems at ambient temperature that prevented them from forming metastable emulsion/nanoemulsion or thermodynamically stable microemulsion systems. High energy homogenization (high pressure or ultrasonic homogenizer) or low energy homogenization (heating) could be used to form emulsions or nanoemulsions at low or intermediate SOR values; whereas only heating was necessary to form stable microemulsions at high SOR values.

  13. Characterization of cephalexin loaded nonionic microemulsions.

    PubMed

    Fanun, Monzer; Papadimitriou, Vassiliki; Xenakis, Aristotelis

    2011-09-01

    Water/propylene glycol/sucrose laurate/ethoxylated mono-di-glyceride/isopropyl myristate/peppermint oil U-type microemulsions were used to solubilize cephalexin. Microemulsion dilution and interfacial factors contributing to the cephalexin solubilization were evaluated. Cephalexin solubilization capacity increases with the increase in the aqueous phase volume fraction (φ) up to 0.4 then decreases. Electrical conductivity of drug loaded and drug free microemulsions increases with φ. The hydrodynamic radius measured by dynamic light scattering of the oil-in-water loaded microemulsions decreases with temperature. The microemulsions were characterized by the volumetric parameters, density, excess volume, ultrasonic velocity and isentropic compressibility. The microemulsion densities increase with φ up to 0.8 then decrease. The excess volume decreases with φ up to 0.8 then stabilizes. Ultrasonic velocities increase with the increase in φ while isentropic compressibility decreases. Analysis of the volumetric parameters enabled the characterization of structural transition along the microemulsion phase region. The presence of water-in-oil, bicontinuous and oil-in-water microemulsions, at aqueous phase volume fractions below 0.2, between 0.3 and 0.7 and above 0.8, respectively were found. Interfacial properties and dynamic structure of the monolayer for drug loaded and drug free microemulsions, were studied by electron paramagnetic resonance spectroscopy employing the nitroxide spin probe 5-doxylstearic acid. The rigidity of the interface was affected by the water content and also the presence of cephalexin. Copyright © 2011 Elsevier Inc. All rights reserved.

  14. Theory of microemulsions in a gravitational field

    NASA Technical Reports Server (NTRS)

    Jeng, J. F.; Miller, Clarence A.

    1989-01-01

    A theory of microemulsions developed previously is extended to include the effect of a gravitational field. It predicts variation with position of drop size, drop volume fraction, and area per molecule in the surfactant films within a microemulsion phase. Variation in volume fraction is greatest and occurs in such a way that oil content increases with increasing elevation, as has been found experimentally. Large composition variations are predicted within a middle phase microemulsion near optimal conditions because inversion from the water-continuous to the oil-continuous arrangement occurs with increasing elevation. Generally speaking, gravity reduces solubilization within microemulsions and promotes separation of excess phases.

  15. Theory of microemulsions in a gravitational field

    NASA Technical Reports Server (NTRS)

    Jeng, J. F.; Miller, Clarence A.

    1989-01-01

    A theory of microemulsions developed previously is extended to include the effect of a gravitational field. It predicts variation with position of drop size, drop volume fraction, and area per molecule in the surfactant films within a microemulsion phase. Variation in volume fraction is greatest and occurs in such a way that oil content increases with increasing elevation, as has been found experimentally. Large composition variations are predicted within a middle phase microemulsion near optimal conditions because inversion from the water-continuous to the oil-continuous arrangement occurs with increasing elevation. Generally speaking, gravity reduces solubilization within microemulsions and promotes separation of excess phases.

  16. Adapalene microemulsion for transfollicular drug delivery.

    PubMed

    Bhatia, Gaurav; Zhou, Yingcong; Banga, Ajay K

    2013-08-01

    The aim of this study was to develop a microemulsion formulation of adapalene for transfollicular delivery. A pseudoternary phase diagram was developed for microemulsion consisting of oleic acid as oil phase, tween 20 as surfactant, Transcutol® as cosurfactant, and deionized water. Differential tape stripping and confocal laser scanning microscopy were performed to determine the penetration of microemulsion through hair follicles. Transmission electron microscopy, dynamic light scattering, polarizing light microscopy, and differential scanning calorimetry were performed to characterize the microstructures of microemulsion. The pH and viscosity of the microemulsions were also determined. Permeation studies were carried out in vitro on porcine ear skin over a period of 24 h using Franz diffusion cells. The drug penetration in the hair follicles increased from 0.109 ± 0.03 to 0.292 ± 0.094 μg, as the microstructure of microemulsion shifted from oil-in-water to bi-continuous, with increase in water content of microemulsion. Confocal laser scanning microscopy images suggested that hair follicles provided the path for transfollicular permeation of adapalene microemulsion. These results suggest that microemulsion penetrated through hair follicles and are promising for transfollicular drug delivery. Copyright © 2013 Wiley Periodicals, Inc.

  17. Fluorescence correlation spectroscopy: an efficient tool for measuring size, size-distribution and polydispersity of microemulsion droplets in solution.

    PubMed

    Pal, Nibedita; Dev Verma, Sachin; Singh, Moirangthem Kiran; Sen, Sobhan

    2011-10-15

    Fluorescence correlation spectroscopy (FCS) is an ideal tool for measuring molecular diffusion and size under extremely dilute conditions. However, the power of FCS has not been utilized to its best to measure diffusion and size parameters of complex chemical systems. Here, we apply FCS to measure the size, and, most importantly, the size distribution and polydispersity of a supramolecular nanostructure (i.e., microemulsion droplets, MEDs) in dilute solution. It is shown how the refractive index mismatch of a solution can be corrected in FCS to obtain accurate size parameters of particles, bypassing the optical matching problem of light scattering techniques that are used often for particle-size measurements. We studied the MEDs of 13 different W(0) values from 2 to 50 prepared in a ternary mixture of water, sodium bis(2-ethylhexyl) sulfosuccinate (AOT), and isooctane, with sulforhodamine-B as a fluorescent marker. We find that, near the optical matching point of MEDs, the dynamic light scattering (DLS) measurements underestimate the droplet sizes while FCS estimates the accurate ones. A Gaussian distribution model (GDM) and a maximum-entropy-based FCS data fitting model (MEMFCS) are used to analyze the fluorescence correlation curves that unfold Gaussian-type size distributions of MEDs in solution. We find the droplet size varies linearly with W(0) up to ~20, but beyond this W(0) value, the size variation deviates from this linearity. To explain nonlinear variation of droplet size for W(0) values beyond ~20, we invoke a model (the coated-droplet model) that incorporates the size polydispersity of the droplets.

  18. Improvement of lindane removal by Streptomyces sp. M7 by using stable microemulsions.

    PubMed

    Saez, Juliana Maria; Casillas García, Verena; Benimeli, Claudia Susana

    2017-10-01

    Lindane is an organochlorine pesticide which persists in the environment and can cause serious health problems due to its chlorinated and hydrophobic nature. Microemulsions are isotropic and macroscopically homogeneous systems with high solubilization capacity of hydrophilic and hydrophobic compounds. The aim of this study was to evaluate the removal of high concentrations of lindane by the actinobacterium Streptomyces sp. M7 in aqueous and soil systems in the presence of stable microemulsions. Three stable microemulsions were successfully formed with Tween 80, 1-pentanol and three vegetable oils. In most cases, an increase in the cosurfactant/surfactant ratio in the microemulsions favored the solubilization of lindane, while an increase in the oil/surfactant ratio negatively affected the stability of the system. The microemulsion prepared with soybean oil allowed the solubilization of 66% of lindane added to the aqueous medium and 4.5 times more than the surfactant solution at the same concentration. This microemulsion increased the bioavailability of lindane in the aqueous medium and hence enhanced its removal by Streptomyces sp. M7 almost two times respect to the achieved with the surfactant solution. In loam soil system, the addition of the microemulsion allowed an 87% of lindane removal by Streptomyces sp. M7, increasing almost 50% the removal respect to the obtained without the addition of surfactant agents, although it did not present significant difference respect to the obtained with the surfactant solution. This is the first report on enhanced lindane removal by actinobacteria by using direct microemulsions as bioremediation tools. Copyright © 2017 Elsevier Inc. All rights reserved.

  19. Novel nanodispersed coal liquefaction catalysts: Molecular design via microemulsion-based synthesis. Technical progress report, October--December 1993

    SciTech Connect

    Boakye, E.; Radovic, L.R.; Osseo-Asare, K.

    1994-09-01

    Three different synthesis protocols were used to synthesize nanosize molybdenum sulfide particles in the microemulsion system polyoxyethylene(5)nonylphenyl ether (NP-5)/cyclohexane/water: (a) acid-solubilized microemulsion plus tetrathiomolybdate (ASMPT), (b) tetrathiomolybdate-solubilized microemulsion plus acid (TSMPA) and (c) microemulsion plus microemulsion (MPM), i.e., acid-solubilized microemulsion plus tetrathiomolybdate-solubilized microemulsion. The particle size was found to depend on the synthesis method, especially at water-to-surfactant molar ratios (R) greater than 2.5. At R=3.5-4.5, the average particle size increased according to the synthesis method in the order: ASMPT < MPM < TSMPA. Furthermore, for each synthesis protocol, the average particle diameter increased with the water-to-surfactant molar ratio (R). These trends are rationalized by considering: (a) the increase in the rate of exchange of materials between the inverse micelles as R is increased, and (b) the different effects of the electrolytes (i.e., sulfuric acid and ammonium tetrathiomolybdate plus sodium hydroxide) on microemulsion stability.

  20. Formation mechanism of CdS nanoparticles with tunable luminescence via a non-ionic microemulsion route

    NASA Astrophysics Data System (ADS)

    Angelescu, Daniel G.; Munteanu, Gabriel; Anghel, Dan F.; Peretz, Sandu; Maraloiu, Adrian V.; Teodorescu, Valentin S.

    2013-01-01

    We investigated the synthesis of CdS nanoparticles via an optimized water-in-oil microemulsion route that used the non-ionic surfactant-based system H2O- n-octane-Brij30/1-octanol. For that purpose, a microemulsion that contained Cd(II) ions ( μe1) and another microemulsion that contained S2- ions ( μe2) were combined. To investigate the ways in which the non-ionic microemulsion characteristics controlled the size and emission properties of colloidal CdS quantum dots, μe1 and μe2 with tunable and robust similar structure were prepared. This requirement was fulfilled by matching the water emulsification failure boundary ( wefb) of the two microemulsions and carrying out synthesis along this boundary. Dynamic light scattering and fluorescence probe techniques were used to investigate the size and interfacial organization of the microemulsion water droplets, and the CdS nanoparticles were characterized by UV-Vis and static fluorescence spectrometry, TEM and HRTEM. Nanoparticles of diameter 4.5-5.5 nm exhibiting enhanced band edge emission were produced by increasing the water content of the precursor microemulsions. The experimental results were combined with a Monte Carlo simulation approach to demonstrate that growth via coagulation of seed nuclei represented the driving mechanism for the CdS nanoparticle formation in the water-in-oil microemulsion.

  1. In vitro and in vivo antifungal activity of a water-dilutable cassia oil microemulsion against Geotrichum citri-aurantii.

    PubMed

    Xu, Shi-Xiang; Li, Yi-Chen; Liu, Xia; Mao, Li-Juan; Zhang, Hui; Zheng, Xiao-Dong

    2012-10-01

    Recently, food-grade microemulsions have been of increasing interest to researchers and have shown great potential in industrial applications. In this study a food-grade water-dilutable microemulsion system with cassia oil as oil, ethanol as cosurfactant, Tween 20 as surfactant and water was developed and its antifungal activity in vitro and in vivo against Geotrichum citri-aurantii was assessed. The phase diagram results confirmed the feasibility of forming a water-dilutable microemulsion based on cassia oil. One microemulsion formulation, cassia oil/ethanol/Tween 20 = 1:3:6 (w/w/w), was selected with the capability to undergo full dilution with water. The average particle size was 6.3 nm. The in vitro antifungal experiments showed that the microemulsion inhibited fungal growth on solid medium and prevented arthroconidium germination in liquid medium and that cassia oil had stronger activity when encapsulated in the microemulsion. The in vivo antifungal experiments indicated that the water-dilutable microemulsion was effective in preventing postharvest diseases of citrus fruits caused by G. citri-aurantii. The results of this study suggest a promising utilisation of water-dilutable microemulsions based on essential oils for the control of postharvest diseases. Copyright © 2012 Society of Chemical Industry.

  2. Joint AOT-Single Scattering Albedo Retrieval in Algorithm MAIAC

    NASA Astrophysics Data System (ADS)

    Lyapustin, A.

    2015-12-01

    Multi-Angle Implementation of Atmospheric Correction (MAIAC) is a new algorithm which uses time series analysis and processing of groups of pixels for advanced cloud detection and retrieval of aerosol and surface bidirectional reflectance properties. MAIAC C6+ re-processing of MODIS data record, scheduled to begin in November 2015, will create a suite of products MCD19. Due to high 1km resolution, MAIAC provides information about fine scale aerosol variability required in different applications such as urban air quality analysis. During the past year, we developed a new MAIAC capability to retrieve Single Scattering Albedo (SSA) from MODIS by adapting OMI heritage approach of O. Torres. We will describe MAIAC retrieval approach, AERONET AOT and SSA validation for different world biomass burning regions, and will compare MAIAC results with other sensors.

  3. Laccase Activity in CTAB-Based Water-in-Oil Microemulsions.

    PubMed

    Azimi, Maryam; Nafissi-Varcheh, Nastaran; Faramarzi, Mohammad Ali; Aboofazeli, Reza

    2016-01-01

    The aim of this study was to develop a microemulsion system as a medium for laccase-catalyzed reactions. Phase behavior studies were conducted by constructing partial pseudo-ternary phase diagrams for systems comprising of cetyltrimethylammonium bromide (CTAB), various organic solvents as the oil phase (i.e., hexane, cyclohexane, heptane, octane, isooctane, toluene, isopropyl myristate), two co-surfactants (i.e., 1-butanol and 1-hexanol) and citrate buffer solution, at various surfactant/co-surfactant weight ratios (Rsm). A monophasic, transparent, non-birefringent area (designated as microemulsion domain) was seen to occur in some phase diagrams along the surfactant/organic solvent axis, the extent of which was dependent mainly upon the nature of co-surfactant and Rsm. On each phase diagram, three different water-in-oil (w/o) microemulsion systems with less than 50 wt% surfactant mixture and less than 20 wt% of aqueous phase were selected for laccase loading and activity measurements. Results revealed that the catalytic activity of laccase in CTAB-based w/o microemulsions decreased considerably, compared with its activity in the buffer solution, the extent of which depended upon the type of component and their compositions in the microemulsions. It was suggested that the conformational changes due to the electrostatic interactions between the cationic head group of CTAB and the negative enzyme might be the reason for the reduction of laccase activity, once entrapped in the microemulsion.

  4. Water-in-Oil Microemulsions for Protein Delivery: Loading Optimization and Stability.

    PubMed

    Perinelli, Diego R; Cespi, Marco; Pucciarelli, Stefania; Vincenzetti, Silvia; Casettari, Luca; Lam, Jenny K W; Logrippo, Serena; Canala, Elisa; Soliman, Mahmoud E; Bonacucina, Giulia; Palmieri, Giovanni F

    2017-01-01

    Microemulsions are attractive delivery systems for therapeutic proteins and peptides due to their ability to enhance bioavailability. Although different proteins and peptides have been successfully delivered through such ternary systems, no information can be found about protein loading and the formulation stability when such microemulsions are prepared with pharmaceuticallyapproved oils and surfactants. The aim of this work was to optimise a ternary system consisting of water/ ethyl oleate/Span® 80-Tween® 80 and to determine its protein loading capacity and stability, using bovine serum albumin (BSA) as a model of biomolecule. The optimization was carried out using a Central Composite Design and all the prepared formulations were characterised through dynamic light scattering, rheology, optical and polarized microscopy. Subsequently, the maximum loading capacity was determined and the stability of the final microemulsion with the highest content of protein was followed over six months. To investigate the structural features of the protein, BSA was recovered from the microemulsion and analysed through fluorescence spectroscopy. After incorporation of the protein in the microemulsion, a decrease of its aqueous solubility was observed. However, the formulation remained stable over six months and the native-like state of the recovered protein was demonstrated by fluorescence spectroscopy Conclusion: This study demonstrated the feasibility of preparing microemulsions with the highest content of protein and their long-term stability. Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.org.

  5. Laccase Activity in CTAB-Based Water-in-Oil Microemulsions

    PubMed Central

    Azimi, Maryam; Nafissi-Varcheh, Nastaran; Faramarzi, Mohammad Ali; Aboofazeli, Reza

    2016-01-01

    The aim of this study was to develop a microemulsion system as a medium for laccase-catalyzed reactions. Phase behavior studies were conducted by constructing partial pseudo-ternary phase diagrams for systems comprising of cetyltrimethylammonium bromide (CTAB), various organic solvents as the oil phase (i.e., hexane, cyclohexane, heptane, octane, isooctane, toluene, isopropyl myristate), two co-surfactants (i.e., 1-butanol and 1-hexanol) and citrate buffer solution, at various surfactant/co-surfactant weight ratios (Rsm). A monophasic, transparent, non-birefringent area (designated as microemulsion domain) was seen to occur in some phase diagrams along the surfactant/organic solvent axis, the extent of which was dependent mainly upon the nature of co-surfactant and Rsm. On each phase diagram, three different water-in-oil (w/o) microemulsion systems with less than 50 wt% surfactant mixture and less than 20 wt% of aqueous phase were selected for laccase loading and activity measurements. Results revealed that the catalytic activity of laccase in CTAB-based w/o microemulsions decreased considerably, compared with its activity in the buffer solution, the extent of which depended upon the type of component and their compositions in the microemulsions. It was suggested that the conformational changes due to the electrostatic interactions between the cationic head group of CTAB and the negative enzyme might be the reason for the reduction of laccase activity, once entrapped in the microemulsion. PMID:27980579

  6. Microstructure of microemulsion in MEEKC.

    PubMed

    Cao, Yuhua; Sheng, Jianwei

    2010-01-01

    The influences of the composition of microemulsion on the microstructure including dimensions and zeta potentials of microdroplets were measured in details. The average dynamic dimension of microdroplets was measured by dynamic laser light scattering, and zeta potential was determined to characterize average surface charge density of microdroplets. The experiment results showed that increase of the amount of surfactant resulted in decrease of microdroplet size but almost invariant zeta potential, which would enlarge migration time of the microdroplet in MEEKC. With increment of cosurfactant concentration, the microdroplet size had an increasing trend, whereas the zeta potential decreased. Thus, observed migration velocity of microdroplets increased, which made the separation window in MEEKC shortened. Neither dimension nor zeta potential of microdroplets changed by varying both the type and the amount of the oil phase. Adding organic solvent as modifier to microemulsion did not change the microdroplet size, but lowered zeta potential. The migration time of microdroplet still became larger, since EOF slowed down owing to organic solvent in capillary. So, besides increment of surfactant concentration, organic additive could also enlarge the separation window. Increase of cosurfactant concentration was beneficial for separation efficiency thanks to the looser structure of swollen microdroplet, and the peak sharpening might compensate for the resolution and peak capacity owing to a narrow separation window. Except the oil phase, tuning the composition of microemulsion would change the microstructure, eventually could be exploited to optimize the resolution and save analysis time in MEEKC.

  7. Investigation of microemulsion microstructure and its impact on skin delivery of flufenamic acid.

    PubMed

    Mahrhauser, Denise-Silvia; Kählig, Hanspeter; Partyka-Jankowska, Ewa; Peterlik, Herwig; Binder, Lisa; Kwizda, Kristina; Valenta, Claudia

    2015-07-25

    Microemulsions are well known penetration enhancing delivery systems. Several properties are described that influence the transdermal delivery of active components. Therefore, this study aimed to characterize fluorosurfactant-based microemulsions and to assess the impact of formulation variables on the transdermal delivery of incorporated flufenamic acid. The microemulsion systems prepared in this study consisted of bistilled water, oleic acid, isopropanol as co-solvent, flufenamic acid as active ingredient and either Hexafor(TM)670 (Hex) or Chemguard S-550-100 (Sin) as fluorosurfactant. Characterization was performed by a combination of techniques including electrical conductivity measurements, small-angle X-ray scattering (SAXS) and nuclear magnetic resonance (NMR) self-diffusion experiments. In vitro skin permeation experiments were performed with each prepared microemulsion using Franz type diffusion cells to correlate their present microstructure with their drug delivery to skin. Electrical conductivity increased with added water content. Consequently, the absence of a conductivity maximum as well as the NMR and SAXS data rather suggest O/W type microemulsions with spherical or rod-like microstructures. Skin permeation data revealed enhanced diffusion for Hex- and Sin-microemulsions if the shape of the structures was rather elongated than spherical implying that the shape of droplets had an essential impact on the skin permeation of flufenamic acid.

  8. Preparation and enhancement of oral bioavailability of curcumin using microemulsions vehicle.

    PubMed

    Hu, Liandong; Jia, Yanhong; Niu, Feng; Jia, Zheng; Yang, Xun; Jiao, Kuiliang

    2012-07-25

    A new microemulsions system of curcumin (CUR-MEs) was successfully developed to improve the solubility and bioavailability of curcumin. Several formulations of the microemulsions system were prepared and evaluated using different ratios of oils, surfactants, and co-surfactants (S&CoS). The optimal formulation, which consists of Capryol 90 (oil), Cremophor RH40 (surfactant), and Transcutol P aqueous solution (co-surfactant), could enhance the solubility of curcumin up to 32.5 mg/mL. The pharmacokinetic study of microemulsions was performed in rats compared to the corresponding suspension. The stability of microemulsions after dilution was excellence. Microemulsions have significantly increased the C(max) and area under the curve (AUC) in comparison to that in suspension (p < 0.05). The relative bioavailability of curcumin in microemulsions was 22.6-fold higher than that in suspension. The results indicated that the CUR-MEs could be used as an effective formulation for enhancing the oral bioavailability of curcumin.

  9. Evidence of water-in-ionic liquid microemulsion formation by nonionic surfactant Brij-35.

    PubMed

    Rai, Rewa; Pandey, Siddharth

    2014-09-02

    Brij-35, a common and popular nonionic surfactant, is shown to form water-in-ionic liquid (w/IL) microemulsions with IL 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim][PF6]) as the bulk phase. The presence of w/[bmim][PF6] microemulsions is hinted by the significantly increased solubility of water in Brij-35 solution of [bmim][PF6]. The formation of w/[bmim][PF6] microemulsions by Brij-35 is confirmed using dynamic light scattering (DLS) and small-angle X-ray scattering (SAXS) measurements. Brij-35 forms reverse micelle-type aggregates within [bmim][PF6] in the absence of added-water. These reverse micelles become w/[bmim][PF6] microemulsions as the water is added to the system. As the water loading (w0) is increased, the average diameter of the aggregates increases. Fourier transform infrared (FTIR) absorbance data reveal the presence of both "bound" and "free" water within the system. The "bound" water is associated with the water pools of the w/[bmim][PF6] microemulsions. Excited-state proton transfer (ESPT) involving probe pyranine shows deprotonation of pyranine within the water pools of the w/[bmim][PF6] microemulsions.

  10. Carbon dioxide in ionic liquid microemulsions.

    PubMed

    Zhang, Jianling; Han, Buxing; Li, Jianshen; Zhao, Yueju; Yang, Guanying

    2011-10-10

    Tailor-made emulsion: a CO(2) -in-ionic-liquid microemulsion was produced for the first time. The CO(2)-swollen micelles are "tunable" because the micellar size can be easily adjusted by changing the pressure of CO(2). The microemulsion has potential applications in materials synthesis, chemical reactions, and extraction.

  11. Trend Estimates of AERONET-Observed and Model-Simulated AOTs Between 1993 and 2013

    NASA Technical Reports Server (NTRS)

    Yoon, J.; Pozzer, A.; Chang, D. Y.; Lelieveld, J.; Kim, J.; Kim, M.; Lee, Y. G.; Koo, J.-H.; Lee, J.; Moon, K. J.

    2015-01-01

    Recently, temporal changes in Aerosol Optical Thickness (AOT) have been investigated based on model simulations, satellite and ground-based observations. Most AOT trend studies used monthly or annual arithmetic means that discard details of the generally right-skewed AOT distributions. Potentially, such results can be biased by extreme values (including outliers). This study additionally uses percentiles (i.e., the lowest 5%, 25%, 50%, 75% and 95% of the monthly cumulative distributions fitted to Aerosol Robotic Network (AERONET)-observed and ECHAM/MESSy Atmospheric Chemistry (EMAC)-model simulated AOTs) that are less affected by outliers caused by measurement error, cloud contamination and occasional extreme aerosol events. Since the limited statistical representativeness of monthly percentiles and means can lead to bias, this study adopts the number of observations as a weighting factor, which improves the statistical robustness of trend estimates. By analyzing the aerosol composition of AERONET-observed and EMAC-simulated AOTs in selected regions of interest, we distinguish the dominant aerosol types and investigate the causes of regional AOT trends. The simulated and observed trends are generally consistent with a high correlation coefficient (R = 0.89) and small bias (slope+/-2(sigma) = 0.75 +/- 0.19). A significant decrease in EMAC-decomposed AOTs by water-soluble compounds and black carbon is found over the USA and the EU due to environmental regulation. In particular, a clear reversal in the AERONET AOT trend percentiles is found over the USA, probably related to the AOT diurnal cycle and the frequency of wildfires. In most of the selected regions of interest, EMAC-simulated trends are mainly attributed to the significant changes of the dominant aerosols; e.g., significant decrease in sea salt and water soluble compounds over Central America, increase in dust over Northern Africa and Middle East, and decrease in black carbon and organic carbon over

  12. Trend Estimates of AERONET-Observed and Model-Simulated AOTs Between 1993 and 2013

    NASA Technical Reports Server (NTRS)

    Yoon, J.; Pozzer, A.; Chang, D. Y.; Lelieveld, J.; Kim, J.; Kim, M.; Lee, Y. G.; Koo, J.-H.; Lee, J.; Moon, K. J.

    2015-01-01

    Recently, temporal changes in Aerosol Optical Thickness (AOT) have been investigated based on model simulations, satellite and ground-based observations. Most AOT trend studies used monthly or annual arithmetic means that discard details of the generally right-skewed AOT distributions. Potentially, such results can be biased by extreme values (including outliers). This study additionally uses percentiles (i.e., the lowest 5%, 25%, 50%, 75% and 95% of the monthly cumulative distributions fitted to Aerosol Robotic Network (AERONET)-observed and ECHAM/MESSy Atmospheric Chemistry (EMAC)-model simulated AOTs) that are less affected by outliers caused by measurement error, cloud contamination and occasional extreme aerosol events. Since the limited statistical representativeness of monthly percentiles and means can lead to bias, this study adopts the number of observations as a weighting factor, which improves the statistical robustness of trend estimates. By analyzing the aerosol composition of AERONET-observed and EMAC-simulated AOTs in selected regions of interest, we distinguish the dominant aerosol types and investigate the causes of regional AOT trends. The simulated and observed trends are generally consistent with a high correlation coefficient (R = 0.89) and small bias (slope+/-2(sigma) = 0.75 +/- 0.19). A significant decrease in EMAC-decomposed AOTs by water-soluble compounds and black carbon is found over the USA and the EU due to environmental regulation. In particular, a clear reversal in the AERONET AOT trend percentiles is found over the USA, probably related to the AOT diurnal cycle and the frequency of wildfires. In most of the selected regions of interest, EMAC-simulated trends are mainly attributed to the significant changes of the dominant aerosols; e.g., significant decrease in sea salt and water soluble compounds over Central America, increase in dust over Northern Africa and Middle East, and decrease in black carbon and organic carbon over

  13. EPR study of polyaniline synthesized enzymatically in the presence of submicrometer-sized AOT vesicles.

    PubMed

    Rakvin, Boris; Carić, Dejana; Andreis, Mladen; Junker, Katja; Walde, Peter

    2014-02-27

    EPR spectroscopy was used to examine the magnetic properties of two enzymatically synthesized polyaniline (PANI) samples obtained in the presence of submicrometer-sized vesicles formed from sodium bis(2-ethylhexyl)sulfosuccinate (AOT) as templates. PANI-HRPC-AOT was synthesized with horseradish peroxidase isoenzyme C (HRPC) and hydrogen peroxide (H2O2) as oxidant while PANI-TvL-AOT was prepared with Trametes versicolor laccase (TvL) and dioxygen (O2) as oxidant. A commercial conductive sample of the emeraldine salt form of polyaniline (PANI-ES) was also used for comparison in order to correlate the experimental data obtained for PANI-HRPC-AOT and PANI-TvL-AOT with the properties of the well-characterized PANI-ES. It was shown that a model based on the concept of correlated polaronic bands could be applied for the interpretation of the EPR spectra of all three examined samples, although PANI-HRPC-AOT and PANI-TvL-AOT were significantly less conductive than PANI-ES. The magnetic properties of the PANI samples could be related to their conductivities, whereby a low conductivity was ascribed to decreased interchain spin interactions which were detectable from a splitting of the triplet spectrum at low temperatures (5-10 K). The obtained effective distance between the polyaniline chains is larger for enzymatically synthesized PANI than for PANI-ES, most likely mainly due to the presence of AOT which could not be removed completely during the work-up. AOT influences the chain conformation and the average chain-chain distance.

  14. Trend estimates of AERONET-observed and model-simulated AOTs between 1993 and 2013

    NASA Astrophysics Data System (ADS)

    Yoon, J.; Pozzer, A.; Chang, D. Y.; Lelieveld, J.; Kim, J.; Kim, M.; Lee, Y. G.; Koo, J.-H.; Lee, J.; Moon, K. J.

    2016-01-01

    Recently, temporal changes in Aerosol Optical Thickness (AOT) have been investigated based on model simulations, satellite and ground-based observations. Most AOT trend studies used monthly or annual arithmetic means that discard details of the generally right-skewed AOT distributions. Potentially, such results can be biased by extreme values (including outliers). This study additionally uses percentiles (i.e., the lowest 5%, 25%, 50%, 75% and 95% of the monthly cumulative distributions fitted to Aerosol Robotic Network (AERONET)-observed and ECHAM/MESSy Atmospheric Chemistry (EMAC)-model simulated AOTs) that are less affected by outliers caused by measurement error, cloud contamination and occasional extreme aerosol events. Since the limited statistical representativeness of monthly percentiles and means can lead to bias, this study adopts the number of observations as a weighting factor, which improves the statistical robustness of trend estimates. By analyzing the aerosol composition of AERONET-observed and EMAC-simulated AOTs in selected regions of interest, we distinguish the dominant aerosol types and investigate the causes of regional AOT trends. The simulated and observed trends are generally consistent with a high correlation coefficient (R = 0.89) and small bias (slope±2σ = 0.75 ± 0.19). A significant decrease in EMAC-decomposed AOTs by water-soluble compounds and black carbon is found over the USA and the EU due to environmental regulation. In particular, a clear reversal in the AERONET AOT trend percentiles is found over the USA, probably related to the AOT diurnal cycle and the frequency of wildfires. In most of the selected regions of interest, EMAC-simulated trends are mainly attributed to the significant changes of the dominant aerosols; e.g., significant decrease in sea salt and water soluble compounds over Central America, increase in dust over Northern Africa and Middle East, and decrease in black carbon and organic carbon over Australia.

  15. Dynamic light scattering study of microemulsion

    NASA Astrophysics Data System (ADS)

    Sharifi, Soheil; Alavi, Alireza

    2011-05-01

    Brownian motion is a subject of renewed interest since the development of photon correlation spectroscopy (PCS) in the last decade. The dynamic properties of microemulsions and colloidal systems are studied by measuring the relaxation of concentration fluctuations. The mixture of C12E5nanoemulsion with PEG have been studied by small-angle X-ray scattering and dynamic light scattering in order to determine structure and dynamic of the system. Light scattering experiment shown an exponential relaxation for pure C12E5 nanoemulsion that the shape of the relaxation change with increasing of polymer concentration in the C12E5 nanoemulsion, that relaxation becomes non-exponential, which demonstrates increase of cooperatively in the C12E5 nanoemulsion.

  16. Structure and phase behavior of polymer loaded non-ionic and anionic microemulsions

    NASA Astrophysics Data System (ADS)

    Weber, Andreas; Stühn, Bernd

    2016-04-01

    We investigate the structure and phase behavior of C12E4 based reverse water in octane microemulsions with small angle x-ray scattering and small angle neutron scattering experiments to explore the phase diagram of the droplet structure. In the regime of stable droplets, these droplets are loaded with the hydrophilic polymer polyethyleneoxide (MW = 1500 g/mol) and compared with microemulsions based on the anionic surfactant AOT. In the small angle neutron scattering experiments, we use shell contrast to focus on the surfactant shell and its variation with addition of polymer. We observe, as predicted by indirect measurements such as dielectric spectroscopy, that the polymer interacts differently with a nonionic or an anionic surfactant shell: In the former case the addition of polymer does not seem to affect the surfactant shell. In the latter case, the obtained scattering data show that the anionic surfactant layer is strongly influenced leading to a higher polydispersity which may be attributed to a floppier surfactant shell.

  17. Phase transition water-in-oil microemulsions as ocular drug delivery systems: in vitro and in vivo evaluation.

    PubMed

    Chan, Judy; Maghraby, Gamal M M El; Craig, Jennifer P; Alany, Raid G

    2007-01-02

    Microemuslion (ME)-based phase transition systems were evaluated for ocular delivery of pilocarpine hydrochloride (model hydrophilic drug). These used two non-ionic surfactants, sorbitan mono laurate and polyoxyethylene sorbitan mono-oleate with ethyl oleate (oil component) and water. These systems undergo phase change from ME to liquid crystalline (LC) and to coarse emulsion (EM) with a change in viscosity depending on water content. This study selected five formulations containing aqueous phase at 5% (w/w) (ME 5%), 10% (w/w) (ME 10%), 26% (w/w) (LC), 85% (w/w) (O/W EM) and 100% (solution) with the model drug at 1% (w/w). Incorporation of pilocarpine hydrochloride did not affect the phase behaviour. The viscosity was increased initially with dilution from ME 5% to ME 10% then LC, indicating structuring of the system, before being reduced in the EM formulation. Drug release depended on the viscosity with lower release rates obtained from formulations with high viscosity. The miotic response and duration of action were greatest in case of ME and LC formulations indicating high ocular bioavailability. Thus, phase transition ME is promising for ocular drug delivery as it provides the fluidity with its viscosity being increased after application increasing ocular retention while retaining the therapeutic efficiency.

  18. Characterization of patatin esterase activity in AOT-isooctane reverse micelles.

    PubMed

    Jiménez, M; Escribano, J; Gandía-Herrero, F; Chazarra, S; Cabanes, J; García-Carmona, F; Pérez-Gilabert, M

    2002-01-01

    Patatin is a family of glycoproteins that accounts for 30-40% of the total soluble protein in potato (Solanum tuberosum L.) tubers. This protein has been reported not only to serve as a storage protein but also to exhibit lipid acyl hydrolase (LAH) activity. In this study patatin is characterized in AOT-isooctane reverse micelles. The influence on the enzymatic activity of characteristic parameters of reverse micelles, w(o) (= H(2)O/AOT), and the percentage of H(2)O, theta, were investigated. The results obtained show that patatin esterase activity varies with w(o) but remains constant throughout the range of theta values studied. The variation with w(o) showed that the activity follows an S-shaped behavior pattern, reaching a maximum at about w(o) = 20 for 2% H(2)O. Patatin esterase activity was compared with p-nitrophenyl (PNP) fatty acid esters of different chain lengths. The activity was much higher for PNP-caprylate. The pH optimum was 6.0, different from the value obtained when patatin esterase activity was measured in mixed micelle systems. The optimal temperature was 35 degrees C, above which the activity decreased to almost zero. The kinetic parameters were also evaluated (K(m) = 10 mM, V(m) = 158 microM/min, V(m)/K(m) = 15.8 x 10(-3) min(-1)). This paper shows the suitability of reverse micelles for measuring patatin esterase activity, since it allows the study of the enzyme in similar conditions to that prevailing in vivo.

  19. Bicontinuous microemulsions as media for electrochemical studies

    SciTech Connect

    Iwunze, M.O.; Sucheta, A.; Rusling, J.F. )

    1990-03-15

    Biocontinuous microemulsions of didodecyldimethylammonium bromide (DDAB)/dodecane/water were explored as media for voltammetric reductions and oxidations of ruthenium(III) hexaammine, ferrocyanide, ferrocene, cob(II)alamin, and several polycyclic aromatic hydrocarbons (PAHs). These clear microemulsions are conductive and are believed to contain a dynamic extended network of interconnected water tubules. Agreement of simulated and experimental voltammetric data shows that electrochemical theory for homogeneous media is followed to a good approximation in DDAB microemulsions. Diffusion of electroactive solutes did not reflect the high bulk viscosities of the microemulsions. Nonpolar molecules and ions diffuse as if they were in neat oil or aqueous media, respectively, and voltammograms with good signal to noise ratio are obtained. Reductions of PAHs in the microemulsions occurred by an ECE-type pathway, with nearly reversible one-electron reductions achieved at high scan rates.

  20. Development of w/o microemulsion for transdermal delivery of iodide ions.

    PubMed

    Lou, Hao; Qiu, Ni; Crill, Catherine; Helms, Richard; Almoazen, Hassan

    2013-03-01

    The objective of this study was to develop a water-in-oil (w/o) microemulsion which can be utilized as a transdermal delivery for iodide ions. Several w/o microemulsion formulations were prepared utilizing Span 20, ethanol, Capryol 90®, and water. The selected formulations had 5%, 10%, 15%, 20%, and a maximum of 23% w/w water content. Potassium iodide (KI) was incorporated in all formulations at 5% w/v. Physicochemical characterizations were conducted to evaluate the structure and stability. These studies included: mean droplet size, pH, viscosity, conductivity, and chemical stability tests. In vitro human skin permeation studies were conducted to evaluate the diffusion of the iodide ion through human skin. The w/o microemulsion formulations were stable and compatible with iodide ions with water content ranging from 5% to 23% w/w. The addition of KI influenced the physicochemical properties of microemulsion as compared to blank microemulsion formulations. In vitro human skin permeation studies indicated that selected formulations improved iodide ion diffusion significantly as compared to control (KI solution; P value<0.05). Iodide ions were entrapped within the aqueous core of w/o microemulsion. Span 20, ethanol and Capryol 90 protected the iodide ions against oxidation and formed a stable microemulsion. It is worth to note that according to Hofmeister series, iodide ions tend to lower the interfacial tension between water and oil and consequently enhance overall stability. This work illustrates that microemulsion system can be utilized as a vehicle for the transdermal administration of iodide.

  1. Formulation and Characterization of Clotrimazole Microemulsions and Microemulsion-Based Gels

    NASA Astrophysics Data System (ADS)

    Kaewbanjong, Jarika; Amnuaikit, Thanaporn; Boonme, Prapaporn

    2014-11-01

    This study aimed to formulate and physically characterized clotrimazole microemulsions and microemulsion based-gels compared with their blank counterparts. Microemulsions were prepared by simple mixing of isopropyl palmitate, 2:1 mixture of water and isopropyl alcohol and 1:1 mixture of polyethylene 20 sorbitan monooleate and sorbitan monooleate. To develop microemulsion-based gels, fumed silica was use as a thickening agent at 2.5, 5 or 7.5% w/w. All studied formulations, i.e., 2 microemulsions and 6 microemulsion based-gels were investigated for physical properties such as appearance, conductivity, pH, rheological behavior and spreadability. Afterwards, 2 microemulsions (ME1 and ME2) and 2 microemulsion based-gels (MBG1-3 and MBG2-2) were selected to incorporate with clotrimazole and then investigated for physical properties. All formulations showed good appearance and physical properties. Clotrimazole did not affect most characteristics of their blank counterparts, except conductivity. Therefore, the investigated microemulsions and microemulsion based gels could be used as the vehicles of clotrimazole for skin drug delivery.

  2. Application of electrochemical impedance spectroscopy: A phase behavior study of babassu biodiesel-based microemulsions.

    PubMed

    Pereira, Thulio C; Conceição, Carlos A F; Khan, Alamgir; Fernandes, Raquel M T; Ferreira, Maira S; Marques, Edmar P; Marques, Aldaléa L B

    2016-11-05

    Microemulsions are thermodynamically stable systems of two immiscible liquids, one aqueous and the other of organic nature, with a surfactant and/or co-surfactant adsorbed in the interface between the two phases. Biodiesel-based microemulsions, consisting of alkyl esters of fatty acids, open a new means of analysis for the application of electroanalytical techniques, and is advantageous as it eliminates the required pre-treatment of a sample. In this work, the phase behaviours of biodiesel-based microemulsions were investigated through the electrochemical impedance spectroscopy (EIS) technique. We observed thatan increase in the amount of biodiesel in the microemulsion formulation increases the resistance to charge transfer at the interface. Also, the electrical conductivity measurements revealed that a decrease or increase in electrical properties depends on the amount of biodiesel. EIS studies of the biodiesel-based microemulsion samples showed the presence of two capacitive arcs: one high-frequency and the other low-frequency. Thus, the formulation of microemulsions plays an important role in estimating the electrical properties through the electrochemical impedance spectroscopy technique. Copyright © 2016 Elsevier B.V. All rights reserved.

  3. Application of electrochemical impedance spectroscopy: A phase behavior study of babassu biodiesel-based microemulsions

    NASA Astrophysics Data System (ADS)

    Pereira, Thulio C.; Conceição, Carlos A. F.; Khan, Alamgir; Fernandes, Raquel M. T.; Ferreira, Maira S.; Marques, Edmar P.; Marques, Aldaléa L. B.

    2016-11-01

    Microemulsions are thermodynamically stable systems of two immiscible liquids, one aqueous and the other of organic nature, with a surfactant and/or co-surfactant adsorbed in the interface between the two phases. Biodiesel-based microemulsions, consisting of alkyl esters of fatty acids, open a new means of analysis for the application of electroanalytical techniques, and is advantageous as it eliminates the required pre-treatment of a sample. In this work, the phase behaviours of biodiesel-based microemulsions were investigated through the electrochemical impedance spectroscopy (EIS) technique. We observed thatan increase in the amount of biodiesel in the microemulsion formulation increases the resistance to charge transfer at the interface. Also, the electrical conductivity measurements revealed that a decrease or increase in electrical properties depends on the amount of biodiesel. EIS studies of the biodiesel-based microemulsion samples showed the presence of two capacitive arcs: one high-frequency and the other low-frequency. Thus, the formulation of microemulsions plays an important role in estimating the electrical properties through the electrochemical impedance spectroscopy technique.

  4. Tricaprylin microemulsion for oral delivery of low molecular weight heparin conjugates.

    PubMed

    Kim, Sang Kyoon; Lee, Eun Hye; Vaishali, Bagalkot; Lee, Seulki; Lee, Yong-kyu; Kim, Choong-Yong; Moon, Hyun Tae; Byun, Youngro

    2005-06-20

    Heparin is available to patients only by parenteral administrations due to its low oral bioavailability. For the oral delivery of low molecular weight heparin (LMWH), LMWH-DOCA was synthesized by chemical conjugation of LMWH and deoxycholic acid (DOCA) and this conjugate was formulated in a microemulsion system. The coupling ratios of DOCA to LMWH for LD1 and LD2 were 1.33 and 2.37, respectively. The microemulsion was composed of tricaprylin, surfactant mixture (Tween 80 and Span 20) and LMWH-DOCA in water, and their volume ratio was 5:3:1:1. Pharmacokinetic parameters of LMWH were not significantly changed by conjugation with DOCA; however, when LMWH-DOCA in tricaprylin microemulsion was orally administered in mice, its bioavailability was increased up to 1.5%. Furthermore, the enhancing effect of the conjugated DOCA in the tricaprylin microemulsion on the absorption of LMWH in the intestine was more significantly increased in monkey than in mice. Since the tricaprylin microemulsion could dissolve LMWH-DOCA, this formulation could maximize the enhancing effect of the conjugated DOCA on the absorption of LMWH in the intestine. Finally, it was expected that 20 mg/kg of LMWH-DOCA in the tricaprylin microemulsion was enough to prevent deep vein thrombosis (DVT) and pulmonary embolism (PE).

  5. [Structure and dynamics of microemulsions in bulk, at interfaces, and in confined geometries]. Progress report

    SciTech Connect

    Not Available

    1993-12-31

    The authors have been constructing a special purpose small angle neutron scattering spectrometer (SAND) in collaboration with IPNS of Argonne National Laboratory and Texaco Research Laboratories in Beacon, New York. The spectrometer, having a moderate neutron flux, will be uniquely suited for detailed studies of complex fluids in their various phases. This spectrometer will be fully available to general users of the small angle scattering community after a year of testing and upon installation of the auxiliary equipment. The general research objective of the MIT group is to continue studies of the microstructural relationship to phase-behavior in three-component microemulsion systems. Specifically, they shall study the (1) variation of bulk structures when a microemulsion undergoes a non-wetting to wetting transition, (2) correlating interfacial reflectivity measurements of these wetting transitions to the SANS results, (3) use the contrast variation technique they recently developed for measuring the mean and Gaussian curvatures of the surfactant sheet to study the structural inversion of water-in-oil to oil-in-water microemulsions and the transition of disordered bicontinuous microemulsion to ordered lamellar phases, (4) investigation of the effects of spatial confinement on the phase behavior and structure of bicontinuous microemulsions, and finally (5) they shall continue the study of the recently discovered non-exponential relaxation of droplet density fluctuations near the critical and percolation points in water-in-oil droplet microemulsions.

  6. A Study of Organic Chemical Reactions in Microemulsions.

    DTIC Science & Technology

    1984-10-24

    organic synthesis were investigated. The first involved a delineation of the ability of microemulsions to catalyze synthetically useful reactions of water...microemulsions in organic synthesis . We also began the design and synthesis of turnover catalysts for carbon and phosphorus ester hydrolysis. Originator...furnished key words include: microemulsions, organic synthesis , microemulsions, reactive site, microemulsion, destructible (cleavable) surfactant-based, destructible (cleavable) surfactants, turnover catalysts.

  7. Competitive surfactant adsorption of AOT and Tween 20 on gold measured using a quartz crystal microbalance with dissipation.

    PubMed

    Thavorn, Jakkrit; Hamon, Joshua J; Kitiyanan, Boonyarach; Striolo, Alberto; Grady, Brian P

    2014-09-23

    Competitive surfactant adsorption of anionic surfactant AOT and nonionic surfactant Tween 20 on gold was investigated by using a quartz crystal microbalance with dissipation (QCM-D) at 25 °C. The adsorption isotherm of pure AOT did not reach a plateau at the CMC, but rather adsorption continued to increase gradually at concentrations higher than the CMC before reaching a plateau. This behavior is evidence of competitive adsorption between AOT and impurities. The adsorbed layer of AOT on gold became more viscoelastic as the concentration of AOT increased. Tween 20 reached the plateau adsorption on gold before its concentration reached the CMC, suggesting that the attraction between Tween 20 and gold is very strong. The Tween 20 adsorbed layer was rigid when compared to the AOT adsorbed layer, as indicated by low dissipation. The addition of Tween 20 to a surface covered by AOT resulted in an increase in adsorbed mass, suggestive of the insertion of Tween 20 into the AOT adsorbed layer as expected because Tween 20 is able to separate the repulsive headgroups of AOT. When AOT was added to a preformed Tween 20 layer, a drop in the adsorbed amount was found between 0 and 0.1 CMC, and then no change was observed until the CMC of AOT was reached; the adsorbed amount then increased, reaching a final adsorption greater than that of pure AOT. All data support the formation of mixed surfactant layers on the surface. Although a two-step model fit both AOT and Tween 20 adsorption kinetic data well, AOT was found to adsorb much more slowly than Tween 20.

  8. Studies on the micropolarities of bmimBF4/TX-100/toluene ionic liquid microemulsions and their behaviors characterized by UV-visible spectroscopy.

    PubMed

    Li, Na; Gao, Yan'an; Zheng, Liqiang; Zhang, Jin; Yu, Li; Li, Xinwei

    2007-01-30

    Ionic liquids (ILs), 1-butyl-3-methylimidazolium tetrafluoroborate (bmimBF4), were substituted for polar water and formed nonaqueous microemulsions with toluene by the aid of nonionic surfactant TX-100. The phase behavior of the ternary system was investigated, and microregions of bmimBF4-in-toluene (IL/O), bicontinuous, and toluene-in-bmimBF4 (O/IL) were identified by traditional electrical conductivity measurements. Dynamic light scattering (DLS) revealed the formation of the IL microemulsions. The micropolarities of the IL/O microemulsions were investigated by the UV-vis spectroscopy using the methyl orange (MO) and methylene blue (MB) as absorption probes. The results indicated that the polarity of the IL/O microemulsion increased only before the IL pools were formed, whereas a relatively fixed polar microenvironment was obtained in the IL pools of the microemulsions. Moreover, UV-vis spectroscopy has also shown that ionic salt compounds such as Ni(NO3)2, CoCl2, CuCl2, and biochemical reagent riboflavin could be solubilized into the IL/O microemulsion droplets, indicating that the IL/O microemulsions have potential application in the production of metallic or semiconductor nanomaterials, and in biological extractions or as solvents for enzymatic reactions. The IL/O microemulsions may have some expected effects due to the unique features of ILs and microemulsions.

  9. A capillary electrophoretic system based on a novel microemulsion for the analysis of coenzyme Q10 in human plasma by electrokinetic chromatography.

    PubMed

    Lucangioli, Silvia; Flor, Sabrina; Sabrina, Flor; Contin, Mario; Mario, Contin; Tripodi, Valeria; Valeria, Tripodi

    2009-06-01

    A new analytical method for determination of coenzyme Q10 (2,3-dimethoxy-5-methyl-6-decaprenyl-1,4-benzoquinone, CoQ10) in human plasma was developed based on CE using a double tensioactive microemulsion. CoQ10 was quantitatively extracted into 1-propanol/hexane and quantified by MEEKC. The microemulsion was prepared by mixing 1.4% w/w sodium bis(2-ethylhexyl) sulfosuccinate, 4% w/w cholic acid, 1% w/w octane, 8.5% w/w butanol, 0.1% w/w PVA and 85% w/w 10 mM Tris buffer at pH 9.0. The optimized electrophoretic conditions included the use of an uncoated silica capillary of 60 cm total length and 75 mum id, an applied voltage of 20 kV, room temperature and 214 nm ultraviolet detection. Selectivity, linearity, LOD, LOQ, precision and accuracy were evaluated as the parameters of validation. Owing to its simplicity and reliability, the proposed method can be an advantageous alternative to the traditional methodology for the quantitation of CoQ10 in human plasma with good accuracy and precision.

  10. Toxicity Evaluation of Microemulsion (Nano Size) of Sour Cherry Kernel Extract for the Oral Bioavailability Enhancement

    PubMed Central

    Salimi, Anayatollah; Motaharitabar, Eisa; Goudarzi, Mehdi; Rezaie, Annahita; Kalantari, Heibatullah

    2014-01-01

    Background: In the recent years nanostructured materials have been the focus of researches due to their wide-spread possibilities to provide new shapes and structures for some materials. Microemulsions can provide uniform nano-sized droplets for templating. Microemulsions are isotropic, thermodynamically-stable systems of oil, water and surfactant with a 20-200 nm droplet size. They can be prepared as oil-in-water (o/w), water-in-oil (w/o) or bicontinuous systems, depending on the equilibrium spontaneous curvature of the surfactant layer at the oil-water interface. Objectives: The aim of this study was to introduce a system designed to improve and enhance the bioavailability of bioflavonoids in the Prunus cerasus (sour cherry) seed kernel extract by developing a novel delivery system, i.e. microemulsion (nanosized particles). Materials and Methods: Microemulsion formulations were prepared by mixing appropriate amounts of surfactants (Tween 80 and Span 20), cosurfactant (propylene glycol) (3:1 ratio), and oil phase (olive oil). The prepared microemulsions were evaluated regarding their mean droplet size, transparency, viscosity, and pH. Sour cherry kernel extract microemulsion was orally administered to mice at doses of 2.5%, 5%, and 10% for 10 days. On the last day, their blood as well as their liver and kidney were used for biochemical and histopathological analyses, respectively. Results: Biochemical factors levels and the pathological study indicated that there were not significant differences in microemulsion extracts compared with the control group (P > 0.05). Conclusions: Not only no toxicity evidence of this product was observed in the dose range used in foods or healthcare, but also it improved the cardiac function recovery. PMID:24644434

  11. The effect of water on the microstructure of 1-butyl-3-methylimidazolium tetrafluoroborate/TX-100/benzene ionic liquid microemulsions.

    PubMed

    Gao, Yan'an; Li, Na; Zheng, Liqiang; Zhao, Xueyan; Zhang, Jin; Cao, Quan; Zhao, Mingwei; Li, Zhen; Zhang, Gaoyong

    2007-01-01

    The ionic liquid (IL) 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF4]) forms nonaqueous microemulsions with benzene with the aid of nonionic surfactant TX-100. The phase diagram of the ternary system was prepared, and the microstructures of the microemulsion were recognized. On the basis of the phase diagram, a series of ionic liquid-in-oil (IL/O) microemulsions were chosen and characterized by dynamic light scattering (DLS), which shows a similar swelling behavior to typical water-in-oil (W/O) microemulsions. The existence of IL pools in the IL/O microemulsion was confirmed by UV/Vis spectroscopic analysis with CoCl2 and methylene blue (MB) as the absorption probes. A constant polarity of the IL pool is observed, even if small amounts of water are added to the microemulsion, thus suggesting that the water molecules are solubilized in the polar outer shell of the microemulsion, as confirmed by FTIR spectra. 1H NMR spectroscopic analysis shows that these water molecules interact with the electronegative oxygen atoms of the oxyethylene (OE) units of TX-100 through hydrogen-bonding interactions, and the electronegative oxygen atoms of the water molecules attract the electropositive imidazolium rings of [bmim][BF4]. Hence, the water molecules are like a glue that stick the IL and OE units more tightly together and thus make the microemulsion system more stable. Considering the unique solubilization behavior of added water molecules, the IL/O microemulsion system may be used as a medium to prepare porous or hollow nanomaterials by hydrolysis reactions.

  12. Microemulsions with surfactant TX100, cyclohexane, and an ionic liquid investigated by conductance, DLS, FTIR measurements, and study of solvent and rotational relaxation within this microemulsion.

    PubMed

    Pramanik, Rajib; Sarkar, Souravi; Ghatak, Chiranjib; Rao, Vishal Govind; Setua, Palash; Sarkar, Nilmoni

    2010-06-10

    Room-temperature ionic liquids (RTILs), N,N,N-trimethyl-N-propyl ammonium bis(trifluoromethanesulfonyl) imide ([N(3111)][Tf(2)N]), were substituted for polar water and formed nonaqueous microemulsions with cyclohexane by the aid of nonionic surfactant TX-100. The phase behavior of the ternary system was investigated, and microregions of [N(3111)][Tf(2)N]-in-cyclohexane (IL/O), bicontinuous, and cyclohexane-in-[N(3111)][Tf(2)N] (O/IL) were identified by traditional electrical conductivity measurements. Dynamic light scattering (DLS) revealed the formation of the IL microemulsions. The FTIR study of O-H stretching band of TX100 also supports this finding. The dynamics of solvent and rotational relaxation have been investigated in [N(3111)][Tf(2)N]/TX100/cyclohexane microemulsions using steady-state and time-resolved fluorescence spectroscopy as a tool and coumarin 480 (C-480) as a fluorescence probe. The size of the microemulsions increases with gradual addition of [N(3111)][Tf(2)N], which revealed from DLS measurement. This leads to the faster collective motions of cation and anions of [N(3111)][Tf(2)N], which contributes to faster solvent relaxation in microemulsions.

  13. Study of Schultz distribution to model polydispersity of microemulsion droplets

    SciTech Connect

    Kotlarchyk, M.; Stephens, R.B.; Huang, J.S.

    1988-03-24

    The authors have employed a histogram analysis method to study the spectra obtained by small-angle neutron scattering (SANS) in order to investigate the size distribution of a model water-in-oil three-component microemulsion. It is found that the often used Schultz distribution function is indeed one of the reasonable choices to represent the moderately polydispersed droplet system. Analysis based on mean spherical approximations of the SANS data and inverse Laplace transformation of quasi-elastic light scattering data, assuming a Schultz distribution, yield consistent results compared with the histogram method. The polydispersity index, ..delta..R/anti R, found in the model microemulsion is roughly constant at larger R, but increases at small R, consistent with a theory proposed by Safran.

  14. Enzymatic Treatments on Tencel in Water and Microemulsion.

    PubMed

    Nostro, Pierandrea Lo; Corrieri, Danilo; Ceccato, Massimo; Baglioni, Piero

    2001-04-15

    Tencel is a relatively new fabric, obtained from wood pulp, that looks like natural cotton. In order to be suitable for commercial purposes, Tencel must be processed to improve its qualities. In this paper we report our studies on the enzymatic defibrillation of Tencel, in which we checked the different behavior of the same set of enzymes dispersed in pure water and in a microemulsion system. Surface properties, such as scanning electron microscopy, contact angle, porosimetry, breaking load, and thickness, were determined, in order to monitor the surface modification of the fabric upon enzymatic defibrillation, and indicate that the process is more efficient and less damaging when carried out in the microemulsion medium. Furthermore, we chemically modified Tencel by attaching fluorinated chains to the fabric surface. Surface properties show that fluorination of Tencel leads to a high degree of water- and oil-repellency in the fabric. Copyright 2001 Academic Press.

  15. Model for microemulsions: An exactly solvable case

    SciTech Connect

    Renlie, L. ); Hoye, J.S. ); Skaf, M.S. ); Stell, G. )

    1991-10-01

    The microscopic model for microemulsions, introduced earlier by Ciach, Hoye, and Stell (J. Chem. Phys. {bold 90}, 1214 (1989)) is here specialized to a one-dimensional lattice and solved exactly by the transfer matrix method. The microemulsion phase is identified by the formation of thermally distributed surfactant-bounded domains of oil. For this phase we find scattering functions and characteristic lengths that have some of the same features found in experimental data for microemulsions. Mean-field interactions beyond nearest-neighbor sites are introduced in order to study the phase diagram for the nonperiodic phases we encounter.

  16. Oil recovery process using polymer microemulsion complexes

    SciTech Connect

    Baker, E.G.; Canter, N.H.; Robbins, M.L.

    1982-11-23

    A process for the enhanced recovery of oil from a subterranean formation using a polymer-microemulsion complex is disclosed. The polymer is polyethylene oxide or polyvinyl pyrrolidone which interacts with the surfactant of the microemulsion to form a physical association. The resulting complex is characterized by a complexation energy of at least 2 kcal/mole. Slugs containing the present polymer-microemulsion complexes are stable at high salinity, show reduced destabilization due to surfactant adsorption and retention by the formation, have low interfacial tensions and achieve an early banking, as well as increased displacement of crude oil.

  17. Self-assembly, phase behaviour and structural behaviour as observed by scattering for classical and non-classical microemulsions.

    PubMed

    Prévost, Sylvain; Gradzielski, Michael; Zemb, Thomas

    2017-09-01

    In this review, we discuss the conditions for forming microemulsions, systems which are thermodynamically stable mixtures of oil and water made stable by the presence of an interfacial film containing surface active molecules. There are several types of microemulsions, depending largely on the stiffness of the amphiphilic monolayer that separates the oily and the aqueous micro-domain. We first discuss and compare the phase behaviour of these different types, starting from the classical microemulsion made from a flexible surfactant film but then also moving on to less classical situations: this occurs when the interfacial film is stiff or when microemulsions are formed in the absence of a classical surfactant. In the second part, we relate these different microemulsion types to the structural features as can be determined via different methodologies by small angle scattering (SAS). Using absolute scaling, general theorems as well as fitting under constraints or to pre-supposed shapes in real space or correlation functions in reciprocal space allows to classify all microemulsions into classical flexible, rigid or ultra-flexible microemulsions with either globular, connected cylinder of locally flat interfaces, with the corresponding conductivity and phase stability properties. Copyright © 2017 Elsevier B.V. All rights reserved.

  18. Optimizing surfactant content to improve oral bioavailability of ibuprofen in microemulsions: just enough or more than enough?

    PubMed

    You, Xiuhua; Xing, Qiao; Tuo, Jue; Song, Weijuan; Zeng, Ying; Hu, Haiyan

    2014-08-25

    Microemulsions show excellent potential as drug delivery systems, but the surfactants used to prepare them can cause side effects. Researchers have explored various strategies to expand microemulsion area and thereby reduce the surfactant content necessary, but how these strategies affect drug oral bioavailability has not been investigated in detail. Microemulsions were prepared using 16% or 24% mixed surfactant Tween 80-Cremophor EL-PEG400 (1:1:2) and either 6% caprylic/capric triglyceride oil (GTCC) or 6% or 15% mixed oil (Maisine™ 35-1 with GTCC). Some microemulsions contained just enough surfactant based on ternary phase diagrams, while others had excess surfactant. All empty and ibuprofen-loaded microemulsions were clear or translucent with a slight blue color, and they remained stable after dilution and centrifugation. In experiments with rats, oral bioavailability (AUC0⟶t) of ibuprofen in the microemulsions was similar for the different formulations (6779.0-7413.3 min μg/mL) and significantly higher than that of an ibuprofen suspension (4830.9 min μg/mL). The different formulations behaved similarly in a cellular uptake assay with Caco-2 cells. These results suggest that excess surfactant does not increase oral bioavailability or cellular uptake of ibuprofen. Therefore, to minimize side effects, using just enough surfactant to ensure microemulsion stability and drug solubility may be an appropriate strategy.

  19. Optimization of minoxidil microemulsions using fractional factorial design approach.

    PubMed

    Jaipakdee, Napaphak; Limpongsa, Ekapol; Pongjanyakul, Thaned

    2016-01-01

    The objective of this study was to apply fractional factorial and multi-response optimization designs using desirability function approach for developing topical microemulsions. Minoxidil (MX) was used as a model drug. Limonene was used as an oil phase. Based on solubility, Tween 20 and caprylocaproyl polyoxyl-8 glycerides were selected as surfactants, propylene glycol and ethanol were selected as co-solvent in aqueous phase. Experiments were performed according to a two-level fractional factorial design to evaluate the effects of independent variables: Tween 20 concentration in surfactant system (X1), surfactant concentration (X2), ethanol concentration in co-solvent system (X3), limonene concentration (X4) on MX solubility (Y1), permeation flux (Y2), lag time (Y3), deposition (Y4) of MX microemulsions. It was found that Y1 increased with increasing X3 and decreasing X2, X4; whereas Y2 increased with decreasing X1, X2 and increasing X3. While Y3 was not affected by these variables, Y4 increased with decreasing X1, X2. Three regression equations were obtained and calculated for predicted values of responses Y1, Y2 and Y4. The predicted values matched experimental values reasonably well with high determination coefficient. By using optimal desirability function, optimized microemulsion demonstrating the highest MX solubility, permeation flux and skin deposition was confirmed as low level of X1, X2 and X4 but high level of X3.

  20. Microemulsion electrokinetic chromatography for analysis of phthalates in soft drinks.

    PubMed

    Hsieh, Sung-Yu; Wang, Chun-Chi; Wu, Shou-Mei

    2013-12-15

    Microemulsion electrokinetic chromatography (MEEKC) is proposed for analysis of di-n-butyl phthalate (DBP) and di-(2-ethylhexyl) phthalate (DEHP) in soft drinks. However, the instability of microemulsion is a critical issue. In this research, a novel material, Pluronic® F-127, which has the properties of polymer and surfactant, was added for stabilizing the microemulsion in the MEEKC system. Our data demonstrate that the presence of Pluronic® F-127 (0.05-0.30%) also helps enhance resolution of highly hydrophobic compounds, DBP and DEHP. The electrokinetic injection of sodium dodecyl sulphate (SDS) including sample (-10 kV, 20 s) was introduced in this MEEKC system and this yielded about 25-fold sensitivity enhancement compared with hydrodynamic injection (1 psi, 10 s). During method validation, calibration curves were linear (r≥0.99), within a range of 75-500 ng/mL for DBP and 150-1000 ng/mL for DEHP. As the precision and accuracy assays, absolute values of relative standard deviation (RSD) and relative error (RE) in intraday (n=3) and interday (n=5) observations were less than 4.93%. This method was further applied for analyzing six commercial soft drinks and one was found containing 453.67 ng/mL of DEHP. This method is considered feasible for serving as a tool for analysis of highly hydrophobic molecules.

  1. Phase behavior of reverse microemulsions based on Peceol(®).

    PubMed

    Mouri, Abdelkader; Diat, Olivier; El Ghzaoui, Abdeslam; Bauer, Caroline; Maurel, Jean Claude; Devoisselle, Jean-Marie; Dorandeu, Christophe; Legrand, Philippe

    2014-02-15

    The phase diagram of the four component system Peceol®/lecithin/ethanol/water was studied at 25°C and at a fixed fraction of ethanol. It shows an isotropic W/O microemulsion phase, biphasic liquid system and Liquid crystalline phases. The stabilizing effect of lecithin with the fluidifying effect of ethanol on the microemulsion based on long chain glycerides provides an effective combination to solubilize a large amount of water. Some structural transitions in the phase diagram were investigated as a function of water content using conductivity, rheology, Karl Fisher titration, optical microscopy and SAXS measurements. The results show no change in the microstructure of the isotropic liquid upon phase separation in the liquid biphasic area. However, in the water rich region, migration of ethanol to the external aqueous phase at the expense of the saturated microemulsion promotes the formation of liquid crystalline phases. As a function of water content, the structural change to the liquid crystalline phases follows: isotropic phase L2 → Inverted hexagonal phase H2 → Inverted hexagonal H2/lamellar Lα phases.

  2. Preparation and Characterization of Dexamethasone Microemulsion Based on Pseudoternary Phase Diagram

    PubMed Central

    Moghimipour, Eskandar; Salimi, Anayatollah; Karami, Masoud; Isazadeh, Sara

    2013-01-01

    Background The increased incidence of inflammatory diseases has necessitated the need to search for new topical dosage form of dexamethasone. Objectives The purpose of the present study was the preparation and evaluation of novel microemulsion as a topical delivery system for dexamethasone by mixing appropriate amount of surfactant including Tween 80 and Labrasol, cosurfactant such as capryol 90 and oil phase including labrafac lipophile wl-transcutol P (10:1 ratio). Materials and Methods The prepared microemulsions were evaluated regarding their particle size, zeta potential, X-Ray scattering, conductivity, stability, viscosity, differential scanning calorimetry (DSC), scanning electron microscopy (SEM), refractory index (RI), pH, and x-ray diffraction (XRD). Results The results showed that the maximum oil was incorporated in microemulsion system that contained surfactant to cosurfactant ratio of 4:1. The mean droplet size range of microemulsion formulation was in the range of 5.09 to 159 nm, and its refractory index (RI) and pH were 1.44 and 7, respectively. Viscosity range was 57-226 cps. Drug release profile showed that 48.18% of the drug released in the 24 hours of experiment. Also, Hexagonal, cubic and lamellar structures were seen in the SEM photograph and XRD peak of microemulsions. Conclusions This study demonstrated that physicochemical properties and in vitro release were dependent upon the contents of S/C, water, and oil percentage in formulations. SAXS technique and SEM obtained important information about microstructure of microemulsions. W/O and bicontinuous microemulsion with different microstructures were found in formulations. PMID:24624198

  3. Preparation methods for monodispersed garlic oil microspheres in water using the microemulsion technique and their potential as antimicrobials.

    PubMed

    Zheng, Hua Ming; Li, Hou Bin; Wang, Da Wei; Liu, Dun

    2013-08-01

    Garlic oil is considered as a natural broad-spectrum antibiotic because of its well-known antimicrobial activity. However, the characteristics of easy volatility and poor aqueous solubility limit the application of garlic oil in industry. The purpose of the present work is to develop and evaluate an oil-free microemulsion by loading garlic oil in microemulsion system. Microemulsions were prepared with ethoxylated hydrogenated castor (Cremophor RH40) as surfactant, n-butanol (or ethanol) as cosurfactant, oleic acid-containing garlic oil as oil phase, and ultrapure water as water phase. The effects of the ratio of surfactant to cosurfactant and different oil concentration on the area of oil-in-water (O/W) microemulsion region in pseudoternary phase diagrams were investigated. The particle size and garlic oil encapsulation efficiency of the formed microemulsions with different formulations were also investigated. In addition, the antimicrobial activity in vitro against Escherichia coli and Staphylococcus aureus was assessed. The experimental results show that a stable microemulsion region can be obtained when the mass ratio of surfactant to cosurfactant is, respectively, 1:1, 2:1, and 3:1. Especially, when the mixture surfactants of RH40/n-butanol 2/1 (w/w) is used in the microemulsion formulation, the area of O/W microemulsion region is 0.089 with the particle size 13.29 to 13.85 nm and garlic oil encapsulation efficiency 99.5%. The prepared microemulsion solution exhibits remarkable antibacterial activity against S. aureus. © 2013 Institute of Food Technologists®

  4. Microemulsion-based synthesis of nanocrystalline materials.

    PubMed

    Ganguli, Ashok K; Ganguly, Aparna; Vaidya, Sonalika

    2010-02-01

    Microemulsion-based synthesis is found to be a versatile route to synthesize a variety of nanomaterials. The manipulation of various components involved in the formation of a microemulsion enables one to synthesize nanomaterials with varied size and shape. In this tutorial review several aspects of microemulsion based synthesis of nanocrystalline materials have been discussed which would be of interest to a cross-section of researchers working on colloids, physical chemistry, nanoscience and materials chemistry. The review focuses on the recent developments in the above area with current understanding on the various factors that control the structure and dynamics of microemulsions which can be effectively used to manipulate the size and shape of nanocrystalline materials.

  5. Phase behavior and microstructure of nonaqueous microemulsions

    SciTech Connect

    Martino, A.; Kaler, E.W. )

    1990-02-22

    Phase behavior of glycerol, propylene glycol, hydrocarbon, and alkylpolyglycol ether (C{sub i}E{sub j}) surfactant microemulsions has been studied. Surfactant solubility in the polar organic phase (a mixture of glycerol and propylene glycol) decreases when glycerol content is increased, and a 2-3-2 phase transition is observed at constant temperature. The phase behavior usually observed in water microemulsions as a function of temperature is observed here as a function of the fraction of glycerol in the polar organic phase. Phase behavior is reported as a function of oil solvophobicity and the surfactant solvophilic-lipophilic balance and is compared to a well-established model developed for aqueous microemulsions. Porod analysis of small-angle X-ray scattering (SAX) measurements indicates the presence of interfaces; thus the fluids are microstructured. The SAXS measurements suggest that aqueous and nonaqueous microemulsions are structurally similar.

  6. Ionic Liquid-Based Microemulsions in Catalysis.

    PubMed

    Hejazifar, Mahtab; Earle, Martyn; Seddon, Kenneth R; Weber, Stefan; Zirbs, Ronald; Bica, Katharina

    2016-12-16

    The design and properties of surface-active ionic liquids that are able to form stable microemulsions with heptane and water are presented, and their promise as reaction media for thermomorphic palladium-catalyzed cross-coupling reactions is demonstrated.

  7. Formation of organic nanoparticles by electrospinning of volatile microemulsions.

    PubMed

    Dvores, Michelle P; Marom, Gad; Magdassi, Shlomo

    2012-05-01

    This study presents a method for one-step formation of poly(ethylene oxide) nanofibers incorporating nanoparticles of a poorly water-soluble compound. Using the new method reported here, nanofiber-nanoparticle composites are fabricated in one step by electrospinning of an oil-in-water microemulsion, in which a model material, propylparaben, has been dissolved within the volatile dispersed phase in the presence of a high-molecular-weight polymer. The approach is based on nanoscale confinement to the dispersed phase of an oil-in-water microemulsion with a volatile oil phase, in which the poorly water-soluble materials are dissolved. Thus, when the thermodynamically stable oil-in-water microemulsion is combined with the rapid evaporation of solvent inherent in the electrospinning process, the droplets are converted into organic nanoparticles embedded within a polymeric nanofiber. In addition to possessing process simplicity, this method exhibits a very high percentage of nanoparticle loading with desirable active material properties. Specifically, the diameter of the nanofibers is in the range of 60-185 nm, and propylparaben exists within the nanofiber as nanocrystals of 30-120 nm. These dimensions suggest that the nanofiber-nanocrystal composites could serve as a delivery system for water-insoluble materials.

  8. Fluorinated microemulsions: A study of the phase behavior and structure

    SciTech Connect

    LoNostro, P.; Choi, S.M.; Chen, S.H.; Ku, C.Y.

    1999-06-24

    Fluorinated surfactants have been studied for their peculiar property to form micellar aggregates in water and oils (hydrocarbons or fluorocarbons) and to produce stable microemulsions. Because of their capacity to dissolve large amounts of gases (such as oxygen and carbon dioxide) and for their characteristic physicochemical properties, fluorocarbons have been tested for specific medical purposes, and their microemulsions are among the most promising candidates for the production of suitable blood substitutes and other biocompatible fluids. The authors have synthesized a new partially fluorinated nonionic surfactant, namely, F(CF{sub 2}){sub 7}-CO-(OCH{sub 2}CH{sub 2}){sub 7.2}OCH{sub 3} (I), that forms stable microemulsions with water and perfluorocarbons such as perfluorooctane (PFO). In this paper the authors describe for the first time the phase behaviors of perfluorooctanoic acid (PFOA) in water/PFH and in water/PFO, and that of ester I in water/PFO. Small-angle neutron-scattering (SANS) experiments provide a detailed description of the microstructure of the H{sub 2}O/PFO/PFOA ternary system.

  9. Ionic liquid/oil microemulsions as chemical nanoreactors.

    PubMed

    Gayet, Florence; El Kalamouni, Chaker; Lavedan, Pierre; Marty, Jean-Daniel; Brûlet, Annie; Lauth-de Viguerie, Nancy

    2009-09-01

    The phase diagram and microstructure of the ternary system ionic, liquid benzylpyridinium bis(trifluoromethanesulfonyl)imide)/nonionic surfactant (octylphenol ethoxylate)/toluene, were studied by using conductivity measurements, dynamic light scattering, pulse field gradient spin-echo NMR, and small-angle neutron scattering. Three microregions were identified by conductivity measurements according to the percolation theory. The sizes of IL-in-oil microemulsions with various IL fractions were then determined by NMR and DLS and were found to be in accordance with the radii of gyration (approximately 2 or 3 nm) determined by SANS. The reverse IL-in-oil microemulsions were used as nanoreactors to perform a Matsuda-Heck reaction between p-methoxyphenyl diazonium salt and 2,3-dihydrofurane in the presence of a palladium catalyst. The reaction yields obtained were greater in microemulsions (67%) than in bulk IL (33%), highlighting a strong effect of confinement. Moreover, a direct correlation between the quantity of IL and the reaction yield was observed.

  10. Formation of hollow silica nanospheres by reverse microemulsion.

    PubMed

    Lin, Cheng-Han; Chang, Jen-Hsuan; Yeh, Yi-Qi; Wu, Si-Han; Liu, Yi-Hsin; Mou, Chung-Yuan

    2015-06-07

    Uniform hollow silica nanospheres (HSNs) synthesized with reverse microemulsion have great application potential as nanoreactors because enzymes or nanocatalysts can be easily encapsulated de novo in synthesis. Water-in-oil (w/o) reverse microemulsions comprising the polymeric surfactant polyoxyethylene (5) isooctylphenyl ether (Igepal CA-520), ammonia and water in a continuous oil phase (alkanes) coalesce into size-tunable silica nanoparticles via diffusion aggregation after the introduction of silica precursors. Here, we elucidate in detail the growth mechanism for silica nanoparticles via nucleation of ammonium-catalyzed silica oligomers from tetraethylorthosilicate (TEOS) and nanoporous aminopropyltrimethoxy silane (APTS) in the reverse microemulsion system. The formation pathway was studied in situ with small-angle X-ray scattering (SAXS). We find a four-stage process showing a sigmoidal growth behavior in time with a crossover from the induction period, early nucleation stage, coalescence growth and a final slowing down of growth. Various characterizations (TEM, N2 isotherm, dynamic light scattering, zeta potential, NMR, elemental analysis) reveal the diameters, scattering length density (SLD), mesoporosity, surface potentials and chemical compositions of the HSNs. Oil phases of alkanes with different alkyl chains are systematically employed to tune the sizes of HSNs by varying oil molar volumes, co-solvent amounts or surfactant mixture ratios. Silica condensation is incomplete in the core region, with the silica source of TEOS and APTS leading to the hollow silica nanosphere after etching with warm water.

  11. Effect of solvents on the pattern formation in a Belousov-Zhabotinsky reaction embedded into a microemulsion

    NASA Astrophysics Data System (ADS)

    Dähmlow, Patricia; Vanag, Vladimir K.; Müller, Stefan C.

    2014-01-01

    Using the ferroin- and the bathoferroin-catalyzed Belousov-Zhabotinsky (BZ) reaction embedded in the sodium-bis (2-ethylhexyl) sulfosuccinate (AOT) water-in-oil microemulsion, we observed different patterns occurring in two different solvents, hexane and octane. Turing patterns were found in both solvents with ferroin. They differ in their interaction with coexisting bulk oscillations, such that a new excitation front was formed around the evolving Turing patterns in hexane. However, in octane, the bulk oscillation merged with the evolving patterns, forming a new excitation front, which propagated into two directions: towards the existing patterns and away from them. For the bathoferroin-catalyzed BZ reaction, patterns like dash waves, jumping waves, and bubble waves were found in both solvents having different wavelengths. A curvature dependence of the splitting and merging of dashes was found.

  12. Effect of solvents on the pattern formation in a Belousov-Zhabotinsky reaction embedded into a microemulsion.

    PubMed

    Dähmlow, Patricia; Vanag, Vladimir K; Müller, Stefan C

    2014-01-01

    Using the ferroin- and the bathoferroin-catalyzed Belousov-Zhabotinsky (BZ) reaction embedded in the sodium-bis (2-ethylhexyl) sulfosuccinate (AOT) water-in-oil microemulsion, we observed different patterns occurring in two different solvents, hexane and octane. Turing patterns were found in both solvents with ferroin. They differ in their interaction with coexisting bulk oscillations, such that a new excitation front was formed around the evolving Turing patterns in hexane. However, in octane, the bulk oscillation merged with the evolving patterns, forming a new excitation front, which propagated into two directions: towards the existing patterns and away from them. For the bathoferroin-catalyzed BZ reaction, patterns like dash waves, jumping waves, and bubble waves were found in both solvents having different wavelengths. A curvature dependence of the splitting and merging of dashes was found.

  13. A step toward the development of high-temperature stable ionic liquid-in-oil microemulsions containing double-chain anionic surface active ionic liquid.

    PubMed

    Rao, Vishal Govind; Banerjee, Chiranjib; Ghosh, Surajit; Mandal, Sarthak; Kuchlyan, Jagannath; Sarkar, Nilmoni

    2013-06-20

    Owing to their fascinating properties and wide range of potential applications, interest in nonaqueous microemulsions has escalated in the past decade. In the recent past, nonaqueous microemulsions containing ionic liquids (ILs) have been utilized in performing chemical reactions, preparation of nanomaterials, synthesis of nanostructured polymers, and drug delivery systems. The most promising fact about IL-in-oil microemulsions is their high thermal stability compared to that of aqueous microemulsions. Recently, surfactant-like properties of surface active ionic liquids (SAILs) have been used for preparation of microemulsions with high-temperature stability and temperature insensitivity. However, previously described methods present a limited possibility of developing IL-in-oil microemulsions with a wide range of thermal stability. With our previous work, we introduced a novel method of creating a huge number of IL-in-oil microemulsions (Rao, V. G.; Ghosh, S.; Ghatak, C.; Mandal, S.; Brahmachari, U.; Sarkar, N. J. Phys. Chem. B2012, 116, 2850-2855), composed of a SAIL as a surfactant, room-temperature ionic liquids as a polar phase, and benzene as a nonpolar phase. The use of benzene as a nonpolar solvent limits the application of the microemulsions to temperatures below 353 K. To overcome this limitation, we have synthesized N,N-dimethylethanolammonium 1,4-bis(2-ethylhexyl) sulfosuccinate (DAAOT), which was used as a surfactant. DAAOT in combination with isopropyl myristate (IPM, as an oil phase) and ILs (as a polar phase) produces a huge number of high-temperature stable IL-in-oil microemulsions. By far, this is the first report of a huge number of high-temperature stable IL-in-oil microemulsions. In particular, we demonstrate the wide range of thermal stability of [C6mim][TF2N]/DAAOT/IPM microemulsions by performing a phase behavior study, dynamic light scattering measurements, and (1)H NMR measurements and by using coumarin-480 (C-480) as a fluorescent probe

  14. Activated microporous materials through polymerization of microemulsion precursors

    NASA Astrophysics Data System (ADS)

    Venkatesan, Arunkumar

    Microemulsions have been well studied for their unique characteristics. They are isotropic, thermodynamically stable and microstructured mixtures of oil and water stabilized by one or more surfactant species. They are formed spontaneously and are thermodynamically stable. Microemulsion precursors can be polymerized to make microporous solids with controlled pore structure and sizes. These polymeric solids have been studied extensively in the past. Although the fundamental properties of the microporous solids have been studied in depth, the development of specific applications that will utilize the unique properties of these solids has not been exhaustively researched. The current work establishes the feasibility of making activated microporous solids from microemulsion precursors, by the use of a ligand that chelates metals and also attaches itself to the polymer monolith. It also uses a novel 'in-situ' incorporation by combining the formulation and incorporation steps into one. The research objectives are, to formulate a microemulsion system that can yield useful microporous solids upon polymerization and activation, to characterize these solids using existing techniques available for analysis of similar microporous solids, to identify and understand the effect of the variables in the system and to study the influence of these variables on the performance characteristics of this material. Characterization techniques like Differential Scanning Calorimetry, Thermogravimetric Analysis and Scanning Electron Microscopy were used. A hydroxyethylmethylmethacrylate/methylmethacrylate/aqueous phase containing 10% SDS' system was chosen as the precursor microemulsion and the corresponding microporous solids were made. A metal chelating ligand, Congo Red, was incorporated onto the microporous polymer using NaOH as a binding agent. The ability of the resultant 'activated' microporous solid to remove metal ions from solution, was evaluated. The metal ion chosen was chromium

  15. Investigation on the structure of water/AOT/IPM/alcohols reverse micelles by conductivity, dynamic light scattering, and small angle X-ray scattering.

    PubMed

    Zhang, Xiaoguang; Chen, Yingjun; Liu, Jiexiang; Zhao, Chuanzhuang; Zhang, Haijiao

    2012-03-29

    We have systematically investigated the effect of alcohols (ethanol, propanol, butanol, and pentanol) on the structure of the water/AOT/IPM system using conductivity, dynamic light scattering (DLS), and small-angle X-ray scattering (SAXS) techniques. The results show that no percolation phenomenon is observed in the water/AOT/IPM system, whereas the addition of ethanol (propanol and butanol) induces apparently percolation. The threshold water content (W(p)) depends closely on the alcohol type and concentration. The effect of alcohols on the conductance behavior is discussed from the physical properties of alcohols, the interfacial flexibility, and the attractive interactions between droplets. The hydrodynamic diameter of droplets (d(H)) obtained from DLS increases markedly with the increase in water content (W(0)); however, it decreases gradually with increasing alcohol chain length and concentration. SAXS measurements display distinctly the shoulder, the low hump peaks, and the heavy tail phenomenon in the pair distance distribution function p(r) profile, which rely strongly on the alcohol species and its concentration. The gyration radius (R(g)) increases with increasing W(0), and decreases with the increase of alcohol chain length and concentration. Schematic diagram of the conductance mechanism of water/AOT/IPM/alcohol systems is primarily depicted. Three different phases of the discrete droplets, the oligomers, and the isolated ellipsoidal droplets existed in the different W(0) ranges correspond to three different stages in the conductivity-W(0) curve. Coupling the structure characteristics of reverse micelles obtained from DLS and SAXS techniques with conductivity could be greatly helpful to deeply understand the percolation mechanism of water/AOT/IPM/alcohols systems.

  16. Co-surfactant free microemulsions: Preparation, characterization and stability evaluation for food application.

    PubMed

    Xu, Zhenbo; Jin, Jun; Zheng, Minying; Zheng, Yan; Xu, Xuebing; Liu, Yuanfa; Wang, Xingguo

    2016-08-01

    The aim of the study is to prepare co-surfactant free microalgal oil microemulsions and investigate their properties as well as processing stability for food application. The physicochemical characteristics of the microemulsions were investigated by dynamic light scattering (DLS), turbidity, conductivity, rheological measurements and transmission electron microscopy (TEM). Within the microemulsion region, when the surfactant to oil ratio was 9:1, the hydrodynamic diameter (Dh) was 18nm; when the surfactant to oil ratio was 7.5:1, the hydrodynamic diameter (Dh) was 50nm. Rheological studies proved that the microemulsion system was a pseudoplastic fluid, which followed a shear thinning flow behavior. The loss rate of docosahexaenoic acid (DHA) was less than 5%wt after ultra high temperature (UHT) and high temperature short time (HTST) thermal treatments. A high content of CaCl2 (10.0%wt) could not destroy the microemulsion system, and it could be stored at 4°C for two years. Copyright © 2016 Elsevier Ltd. All rights reserved.

  17. Macroscopic Phase Separation, Modulated Phases, and Microemulsions: A Unified Picture of Rafts

    PubMed Central

    Shlomovitz, Roie; Maibaum, Lutz; Schick, M.

    2014-01-01

    We simulate a simple phenomenological model describing phase behavior in a multicomponent membrane, a model capable of producing macroscopic phase separation, modulated phases, and microemulsions, all of which have been discussed in terms of raft phenomena. We show that one effect of thermal fluctuations on the mean-field phase diagram is that it permits a direct transition between either one of the coexisting liquid phases to a microemulsion. This implies that one system exhibiting phase separation can be related to a similar system exhibiting the heterogeneities characteristic of a microemulsion. The two systems could differ in their average membrane composition or in the relative compositions of their exoplasmic and cytoplasmic leaves. The model provides a unified description of these raft-associated phenomena. PMID:24806930

  18. Microemulsions for use as spaces in well cementation

    SciTech Connect

    Carriay, J.; De Lautrec, J.

    1980-09-23

    New application of microemulsions as buffers between the slurry and the cement in the cementation of oil wells. The microemulsions contain an amphoteric surfactant selected from the group of alkyl dimethyl betaines.

  19. Ionic liquid containing microemulsions: probe by conductance, dynamic light scattering, diffusion-ordered spectroscopy NMR measurements, and study of solvent relaxation dynamics.

    PubMed

    Pramanik, Rajib; Sarkar, Souravi; Ghatak, Chiranjib; Rao, Vishal Govind; Sarkar, Nilmoni

    2011-03-17

    Room-temperature ionic liquid (RTIL), N-methyl-N-propylpyrrolidinium bis(trifluoromethanesulfonyl)imide ([P(13)][Tf(2)N]), was substituted for polar water and formed nonaqueous microemulsions with benzene by the aid of nonionic surfactant TX-100. The phase behavior of the ternary system was investigated, and microregions of [P(13)][Tf(2)N]-in-benzene (IL/O), bicontinuous, and benzene-in-[P(13)][Tf(2)N] (O/IL) were identified by traditional electrical conductivity measurements. Dynamic light scattering (DLS) revealed the formation of these IL microemulsions because with gradual increase of RTIL contents the droplet sizes of the microemulsions are also gradually increasing. Pulsed-field gradient spin-echo NMR have been studied to measure the diffusion coefficients of neat [P(13)][Tf(2)N] and [P(13)][Tf(2)N] in microemulsions which indicate ionic liquid containing microemulsions is formed. Moreover, the dynamics of solvent relaxation have been investigated in [P(13)][Tf(2)N]/TX100/benzene microemulsions using steady-state and time-resolved fluorescence spectroscopy using coumarin 153 (C-153) and coumarin 480 (C-480) fluorescence probe with variation of RTIL contents in microemulsions. For both of the probes with increasing amount of ionic liquids in microemulsions the relative contribution of the fast components increases and the slow components contribution decreases; therefore the average solvation time decreases. © 2011 American Chemical Society

  20. Tween-embedded microemulsions--physicochemical and spectroscopic analysis for antitubercular drugs.

    PubMed

    Mehta, S K; Kaur, Gurpreet; Bhasin, K K

    2010-03-01

    The microemulsion composed of oleic acid, phosphate buffer, ethanol, and Tween (20, 40, 60, and 80) has been investigated in the presence of antitubercular drugs of extremely different solubilities, viz. isoniazid (INH), pyrazinamide (PZA), and rifampicin (RIF). The phase behavior showing the realm of existence of microemulsion has been delineated at constant surfactant/co-surfactant ratio (K (m) = 0.55) with maximum isotropic region resulting in the case of Tween 80. The changes in the microstructure of Tween 80-based microemulsion in the presence of anti-TB drugs have been established using conductivty (sigma) and viscosity (eta) behavior. The optical microscopic images of the system help in understanding the effect of dilution and presence of drug on the structure of microemulsion. Partition coefficient, particle size analysis, and spectroscopic studies (UV-visible, Fourier transform infrared, and 1H NMR) have been performed to evaluate the location of a drug in the colloidal formulation. To compare the release of RIF, PZA, and INH from Tween 80 formulation, the dissolution studies have been carried out. It shows that the release of drugs follow the order INH>PZA>RIF. The kinetics of the release of drug has been analyzed using the Korsmeyer and Peppas equation. The results have given a fair success to predict that the release of PZA and INH from Tween 80 microemulsion is non-Fickian, whereas RIF is found to follow a Fickian mechanism.

  1. Distribution of nobiletin chitosan-based microemulsions in brain following i.v. injection in mice.

    PubMed

    Yao, Jing; Zhou, Jian Ping; Ping, Qi Neng; Lu, Yun; Chen, Liang

    2008-03-20

    The purpose of this study was to characterize the in vitro properties of a number of chitosan-based microemulsions containing nobiletin and determine its distribution in mice brain following i.v. administration. The phase behavior and properties of chitosan-based microemulsions were investigated in a pseudo-ternary system composed of polyoxyethylene 35 castor oil/benzyl alcohol/medium-chain triglyceride/tea oil/water with the chitosan. The droplet sizes were found to be smaller than 25 nm by photo correlation spectrometer. The nobiletin-loaded hyaluronic acid chitosan-based microemulsion (HAC-ME) carried negative charge and nobiletin-loaded hydrochlorate chitosan-based microemulsion (HCC-ME) carried positive charge. The concentrations of nobiletin in tissues were determined by HPLC after i.v. administration of HAC-ME, nobiletin-loaded microemulsion (ME), HCC-ME and nobiletin solution. Based on AUC(0-t), MRT and C(max), HAC-ME delivered more nobiletin to the brain compared to nobiletin solution, ME and HCC-ME. The long-circulation effect might contribute to the higher AUC(0-t) for HAC-ME in brain. On the other hand, the AUC(0-t) in plasma and brain after i.v. administration of HCC-ME were not significantly increased relative to ME. These results indicate that HAC-ME may be presented as potential candidates for delivering more drugs into the brain.

  2. Influence of surfactant amphiphilicity on the phase behavior of IL-based microemulsions.

    PubMed

    Harrar, Agnes; Zech, Oliver; Klaus, Angelika; Bauduin, Pierre; Kunz, Werner

    2011-10-15

    In this work, we report on the phase behavior of 1-ethyl-3-methyl-imidazolium-ethylsulfate ([emim][etSO(4)])/limonene/polyethylene glycol tert-octylphenyl ether (Triton X-114 or TX-114) microemulsions as a function of ionic liquid (IL) content and temperature. Phase diagrams, conductivity measurements, and small angle X-ray scattering (SAXS) experiments will be presented. A hydrophilic IL, instead of water is used with the goal to enlarge the temperature range on which stable microemulsions can be formed. Indeed, the system shows remarkably large temperature stability, in particular down to -35 °C. We will emphasize on a comparison with a recently published work about microemulsions composed of [emim][etSO(4)], limonene, and Triton X-100 that to some extent are stable at temperatures well below the freezing point of water. The key parameter responsible for the difference in phase behavior, microstructure, and temperature stability is the average repeating number of ethylene oxide units in the surfactant head group, which is smaller for Triton X-114 compared to Triton X-100. Among the fundamental interest, how the amphiphilicity of the surfactant influences the phase diagram and phase behavior of IL-based microemulsions, the exchange of Triton X-100 by Triton X-114 results in one main advantage: along the experimental path the temperature where phase segregation occurs is significantly lowered leading to single phase microemulsions that exist at temperatures beneath 0 °C.

  3. Antioxidant and antimicrobial activities of clove bud essential oil and eugenol nanoparticles in alcohol-free microemulsion.

    PubMed

    Hamed, Said Fatouh; Sadek, Zainab; Edris, Amr

    2012-01-01

    Clove bud essential oil (CEO) and its major individual phenolic constituent eugenol were formulated as nanoparticles in water-based microemulsion systems. The oil titration method was used to incorporate different amounts of the oil and eugenol in the micellar solution of Tween-20. The Antioxidant and antimicrobial activities were evaluated using the DPPH* free radical scavenging assay and the agar disc dilution method, respectively. Results showed that microemulsion improved the evaluated activities of CEO and eugenol compared with the crude counterparts. Individual eugenol microemulsion was more effective than CEO microemulsion which contained only 61.7% eugenol among its constituents. The results of this study could have potential applications in water-based disinfectants, preservation and flavoring of food and in personal hygiene products. It may also have promising applications in the nutraceutical and functional beverage field.

  4. KDP Aqueous Solution-in-Oil Microemulsion for Ultra-Precision Chemical-Mechanical Polishing of KDP Crystal

    PubMed Central

    Dong, Hui; Wang, Lili; Gao, Wei; Li, Xiaoyuan; Wang, Chao; Ji, Fang; Pan, Jinlong; Wang, Baorui

    2017-01-01

    A novel functional KH2PO4 (KDP) aqueous solution-in-oil (KDP aq/O) microemulsion system for KDP crystal ultra-precision chemical-mechanical polishing (CMP) was prepared. The system, which consisted of decanol, Triton X-100, and KH2PO4 aqueous solution, was available at room temperature. The functional KDP aq/O microemulsion system was systematically studied and applied as polishing solution to KDP CMP technology. In this study, a controlled deliquescent mechanism was proposed for KDP polishing with the KDP aq/O microemulsion. KDP aqueous solution, the chemical etchant in the polishing process, was caged into the micelles in the microemulsion, leading to a limitation of the reaction between the KDP crystal and KDP aqueous solution only if the microemulsion was deformed under the effect of the external force. Based on the interface reaction dynamics, KDP aqueous solutions with different concentrations (cKDP) were applied to replace water in the traditional water-in-oil (W/O) microemulsion. The practicability of the controlled deliquescent mechanism was proved by the decreasing material removal rate (MRR) with the increasing of the cKDP. As a result, the corrosion pits on the KDP surface were avoided to some degree. Moreover, the roughnesses of KDP with KDP aq/O microemulsion (cKDP was changed from 10 mM to 100 mM) as polishing solutions were smaller than that with the W/O microemulsion. The smallest surface root-mean-square roughness of 1.5 nm was obtained at a 30 mmol/L KDP aq solution, because of the most appropriate deliquescent rate and MRR. PMID:28772632

  5. Two- and three-dimensional standing waves in a reaction-diffusion system

    NASA Astrophysics Data System (ADS)

    Bánsági, Tamás, Jr.; Vanag, Vladimir K.; Epstein, Irving R.

    2012-10-01

    We observe standing waves of chemical concentration in thin layers [quasi-two-dimensional (2D)] and capillaries [three-dimensional (3D)] containing the aqueous Belousov-Zhabotinsky reaction in a reverse microemulsion stabilized by the ionic surfactant sodium bis-2-ethylhexyl sulfosuccinate (AOT) and with cyclo-octane as the continuous phase. The 3D structures are oscillatory lamellae or square-packed cylinders at high and low volume fractions, respectively, of aqueous droplets. These patterns correspond to oscillatory labyrinthine stripes and square-packed spots in the 2D configuration. Computer simulations, as well as observations in E. coli, give qualitative agreement with the observed patterns and suggest that, in contrast to Turing patterns, the structures are sensitive to the size and shape of the system.

  6. Brazilian version of an assessment tool for the evaluation of work organizational aspects (AOT) by the NIOSH WMSD Research Consortium: translation and application in industrial sectors.

    PubMed

    Batistão, Mariana V; Alcântara, Carolina C; Pissinato, Isabella G; Alem, Michele E R; Coury, Helenice J C G

    2012-01-01

    Work organization affects the production of a company as well as the health of employees. It is a challenge to create sustainable production systems with the least harm to the health. An observational assessment tool was developed by the NIOSH--WMSD Research Consortium and adapted by the SHARP study. The objectives were to translate this assessment tool into Brazilian Portuguese (as the Avaliação de Aspectos Organizacionais do Trabalho--AOT) and to evaluate its applicability in an industrial setting. The AOT final translated version was obtained after a consensus by the research team. Difficulties arose in applying the translated version due to technical terms with no direct equivalents in Portuguese, nonexcluding or similar alternatives, and questions that gave room for various interpretations, besides the great complexity of the tasks performed in the sectors. Despite that, the results suggest that AOT was sensitive for discriminating differences between sectors. Nevertheless, for better application of this tool in complex industrial environments, it is necessary: training and consensus among evaluators, familiarity with organizational aspects of the occupational settings evaluated. Also for assuring the internal validity of the analysis, might be necessary, the creation of subdivisions in the sectors evaluated if the tasks vary significantly intra-sector. The present report can help to understand the difficulties inherent to the evaluation of organizational aspects on a collective level and also the possible implications related to the translation of this assessment into other languages.

  7. The preparation of neem oil microemulsion (Azadirachta indica) and the comparison of acaricidal time between neem oil microemulsion and other formulations in vitro.

    PubMed

    Xu, Jiao; Fan, Qiao-Jia; Yin, Zhong-Qiong; Li, Xu-Ting; Du, Yong-Hua; Jia, Ren-Yong; Wang, Kai-Yu; Lv, Cheng; Ye, Gang; Geng, Yi; Su, Gang; Zhao, Ling; Hu, Ting-Xiu; Shi, Fei; Zhang, Li; Wu, Chang-Long; Tao, Cui; Zhang, Ya-Xue; Shi, Dong-Xia

    2010-05-11

    The preparation of neem oil microemulsion and its acaricidal activity in vitro was developed in this study. In these systems, the mixture of Tween-80 and the sodium dodecyl benzene sulfonate (SDBS) (4:1, by weight) was used as compound surfactant; the mixture of compound surfactant and hexyl alcohol (4:1, by weight) was used as emulsifier system; the mixture of neem oil, emulsifier system and water (1:3.5:5.5, by weight) was used as neem oil microemulsion. All the mixtures were stired in 800 rpm for 15 min at 40 degrees C. The acaricidal activity was measured by the speed of kill. The whole lethal time value of 10% neem oil microemulsion was 192.50 min against Sarcoptes scabiei var. cuniculi larvae in vitro. The median lethal time value was 81.7463 min with the toxicity regression equations of Y=-6.0269+3.1514X. These results demonstrated that neem oil microemulsion was effective against Sarcoptes scabie var. cuniculi larvae in vitro.

  8. Unexpected increasing AOT trends over northwest Bay of Bengal in the early postmonsoon season

    NASA Astrophysics Data System (ADS)

    Kishcha, Pavel; Starobinets, Boris; Long, Charles N.; Alpert, Pinhas

    2012-12-01

    The main point of our study is that aerosol trends can be created by changes in meteorology without changes in aerosol source strength. Over the 10 year period 2000-2009, in October, Moderate Resolution Imaging Spectroradiometer (MODIS) showed strong increasing aerosol optical thickness (AOT) trends of approximately 14% yr-1 over northwest Bay of Bengal (BoB) in the absence of AOT trends over the east of the Indian subcontinent. This was unexpected because sources of anthropogenic pollution were located over the Indian subcontinent and aerosol transport from the Indian subcontinent to northwest BoB was carried out by prevailing winds. In October, winds over the east of the Indian subcontinent were stronger than winds over northwest BoB, which resulted in wind convergence and accumulation of aerosol particles over northwest BoB. Moreover, there was an increasing trend in wind convergence over northwest BoB. This led to increasing trends in the accumulation of aerosol particles over northwest BoB and, consequently, to strong AOT trends over this area. In contrast to October, November showed no increasing AOT trends over northwest BoB or the nearby Indian subcontinent. The lack of AOT trends over northwest BoB corresponds to a lack of trends in wind convergence in that region. Finally, December domestic heating by the growing population resulted in positive AOT trends of similar magnitude over land and sea. Our findings illustrate that in order to explain and predict trends in regional aerosol loading, meteorological trends should be taken into consideration together with changes in aerosol source strength.

  9. Unexpected increasing AOT trends over northwest Bay of Bengal in the early postmonsoon season

    SciTech Connect

    Kishcha, P.; Starobinets, B.; Long, Charles N.; Alpert, P.

    2012-12-13

    The main point of our study is that aerosol trends can be created by changes in meteorology without changes in aerosol source strength. Over the 10 year period 2000–2009, in October, Moderate Resolution Imaging Spectroradiometer (MODIS) showed strong increasing aerosol optical thickness (AOT) trends of approximately 14% yr-1 over northwest Bay of Bengal (BoB) in the absence of AOT trends over the east of the Indian subcontinent. This was unexpected because sources of anthropogenic pollution were located over the Indian subcontinent and aerosol transport from the Indian subcontinent to northwest BoB was carried out by prevailing winds. In October, winds over the east of the Indian subcontinent were stronger than winds over northwest BoB, which resulted in wind convergence and accumulation of aerosol particles over northwest BoB. Moreover, there was an increasing trend in wind convergence over northwest BoB. This led to increasing trends in the accumulation of aerosol particles over northwest BoB and, consequently, to strong AOT trends over this area. In contrast to October, November showed no increasing AOT trends over northwest BoB or the nearby Indian subcontinent. The lack of AOT trends over northwest BoB corresponds to a lack of trends in wind convergence in that region. Finally, December domestic heating by the growing population resulted in positive AOT trends of similar magnitude over land and sea. Our findings illustrate that in order to explain and predict trends in regional aerosol loading, meteorological trends should be taken into consideration together with changes in aerosol source strength.

  10. Improving oral bioavailability of metformin hydrochloride using water-in-oil microemulsions and analysis of phase behavior after dilution.

    PubMed

    Li, Yuan; Song, Jiaqi; Tian, Ning; Cai, Jie; Huang, Meihong; Xing, Qiao; Wang, Yalong; Wu, Chuanbin; Hu, Haiyan

    2014-10-01

    Microemulsions show significant promise for enhancing the oral bioavailability of biopharmaceutics classification system (BCS) class II drugs, but how about class III drugs remains unclear. Here we employed metformin hydrochloride (MET) as the model drug and prepared drug-loaded water-in-oil (W/O) microemulsions selecting different hydrophile-lipophile balance (HLB) surfactant systems, using HLB 8 as a cut-off. We examined the phase behaviors of microemulsions after dilution and attempted to correlate these behaviors to drug oral bioavailability. ME-A, including a lower content of surfactants (35%), underwent a transition of W/O emulsion and then became a stable O/W emulsion in a light milky appearance; ME-B, in contrast, introducing a higher content of surfactants (45%), still remained transparent or semitransparent upon dilution. Unexpectedly, ME-A showed significantly higher oral bioavailability, which can be reduced by blocking the lymphatic absorption pathway. Comparatively, the AUC of ME-B is lower, close to MET solution. Both microemulsions behaved similarly in intestinal perfusion test because of the dilution before perfusion, lacking of the important phase transition of W/O emulsion. These findings suggest that W/O microemulsions improve oral bioavailability of BCS class III drug by promoting lymphatic absorption. Analyzing the phase behavior of microemulsions after dilution may help predict the drug oral bioavailability and optimize formulations. Copyright © 2014. Published by Elsevier B.V.

  11. Microemulsions of N-alkylimidazolium ionic liquid and their performance as microreactors for the photocycloaddition of 9-substituted anthracenes.

    PubMed

    Li, Xin-Wei; Zhang, Jin; Zheng, Li-Qiang; Chen, Bin; Wu, Li-Zhu; Lv, Feng-Feng; Dong, Bin; Tung, Chen-Ho

    2009-05-19

    The phase behavior of the ternary system consisting of an ionic liquid (1-tetradecyl-3-methylimidazolium bromide [C14mim]Br), p-xylene, and water were investigated. Depending on the composition of the ternary system, formation of hexagonal and lamellar liquid crystals as well as microemulsions was observed. 1H NMR spectroscopy study, 2D ROESY spectroscopic analysis, and rheological measurements of the microemulsions indicated that p-xylene is preferably located in the hydrophobic core and the palisade shells of the microemulsions. The sizes of the microemulsion droplets for the samples with water/[C14mim]Br ratio of 78:22 are measured by both dynamic light scattering (DLS) and transmission electron microscopy with the freeze-fracture technique (FF-TEM). Upon change of the mole ratio of the solubilized xylene to [C14mim]Br from 0 to 2.4, the diameters of the microemulsion droplets increase from ca. 20 to 90 nm and size distribution gets broad. These microemulsions can solubilize and preorientate anthracene derivatives with a polar 9-substituent, and thus may enhance the head-to-head cyclomers in the photocyclization of these substrates.

  12. Comparison of different water/oil microemulsions containing diclofenac sodium: preparation, characterization, release rate, and skin irritation studies.

    PubMed

    Kantarci, Gülten; Ozgüney, Işik; Karasulu, H Yeşim; Arzik, Sevgi; Güneri, Tamer

    2007-11-02

    The aim of the present study was to make a comparison of the in vitro release rate of diclofenac sodium (DS) from microemulsion (M) vehicles containing soybean oil, nonionic surfactants (Brij 58 and Span 80), and different alcohols (ethanol [E], isopropyl alcohol [I], and propanol [P]) as cosurfactant. The optimum surfactant:cosurfactant (S:CoS) weight ratios and microemulsion areas were detected by the aid of phase diagrams. Three microemulsion formulations were selected, and their physicochemical properties were examined for the pH, viscosity, and conductivity. According to the release rate of DS, M prepared with P showed the significantly highest flux value (0.059 +/- 0.018 mg/cm(2)/h) among all formulations (P < .05). The conductivity results showed that DS-loaded microemulsions have higher conductivity values (18.8-20.2 microsiemens/cm) than unloaded formulations (16.9-17.9 microsiemens/cm), and loading DS into the formulation had no negative effect on system stability. Moreover, viscosity measurements were examined as a function of shear rate, and Newtonian fluid characterization was observed for each microemulsion system. All formulations had appropriate observed pH values varying from 6.70 to 6.85 for topical application. A skin irritation study was performed with microemulsions on human volunteers, and no visible reaction was observed with any of the formulations. In conclusion, M prepared with P may be a more appropriate formulation than the other 2 formulations studied as drug carrier for topical application.

  13. [The absorption kinetics of oleanolic acid self-microemulsion in rat stomach and intestine].

    PubMed

    Yang, Rui; Su, Le-Qun; Huang, Xin

    2008-11-01

    To study the absorption kinetics of oleanolic acid self-microemulsion in rat stomach and intestine. The absorption kinetics were obtained by using the in situ perfusion method in rat. The absorption of drug was determinated by the decrease in stomach and intestine with the HPLC as the detection method. The absorption percent of oleanolic acid microemulsion for 2 hours was 10.15% in stomach; The absorption rate constants of oleanolic acid microemulsion and micelle were 0.0901/h and 0.0486/h in small intestine, respectively; The best absorption segment in intestine was duodenum, ileum, jejunum and colon by turns. The oleanolic acid self-microemulsifying system significantly enhances the absorption of oleanolic acid in the gastrointestinal tract and improves its bioavailability.

  14. Preparation and characterization of platinum-ruthenium bimetallic nanoparticles using reverse microemulsions for fuel cell catalyst.

    PubMed

    Kim, Taeyoon; Kobayashi, Koichi; Nagai, Masayuki

    2007-01-01

    Platinum-ruthenium bimetallic nanoparticles are prepared by chemical reduction using sodium borohydride in reverse microemulsions of water/isooctane/Igepal CA-630/2-propanol for fuel cell catalysts. The prepared nanoparticles are characterized by transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and energy-dispersive X-ray analysis. The average size and morphology of nanoparticles are dependent on the water volume fraction in reverse microemulsion system in the range of ca. 2-4 nm. The morphology of particles is related with the percolation behavior of water droplets in reverse microemulsions. By the pretreatment of water phase using a hydrochloric acid, the particles of a homogeneous solid solution state can be obtained. The CO stripping cyclovoltammetry and the electrochemical measurements compared with commercial catalyst show that the prepared particles have a high electrochemically active surface area and a stable and high catalytic activity for reformate gas oxidation.

  15. Protein diffusion in a bicontinuous microemulsion: inducing sub-diffusion by tuning the water domain size.

    PubMed

    Neubauer, Ralph; Höhn, Sebastian; Dulle, Martin; Lapp, Alain; Schulreich, Christoph; Hellweg, Thomas

    2017-03-08

    We study the diffusion of an enhanced green fluorescent protein (GFP+) in bicontinuous sugar-surfactant based microemulsions. The size of the water domains in such systems is controlled by changes of the oil-to-water ratio. Hence, microemulsions allow to produce confinement effects in a controlled way. At high water content the protein is found to exhibit Fickian diffusion. Decreasing the water domain size leads to a slowing down of the protein diffusion and sub-diffusive behavior is obtained on the scale observed by fluorescence correlation spectroscopy. Further decrease of the water domain size finally nearly fixes the GFP+ in these domains and forces it to increasingly follow the breathing mode of the microemulsion matrix.

  16. Nanodroplet cluster formation in ionic liquid microemulsions.

    PubMed

    Gao, Yanan; Voigt, Andreas; Hilfert, Liane; Sundmacher, Kai

    2008-08-04

    A common ionic liquid (IL), 1-butyl-3-methylimidazolium tetrafluoroborate (bmimBF(4)), is used as polar solvent to induce the formation of a reverse bmimBF(4)-in-toluene IL microemulsion with the aid of the nonionic surfactant Triton X-100. The swelling process of the microemulsion droplets by increasing bmimBF(4) content is detected by dynamic light scattering (DLS), conductivity, UV/Vis spectroscopy, and freeze-fracture transmission electron microscopy (FF-TEM). The results show that the microemulsion droplets initially formed are enlarged by the addition of bmimBF(4). However, successive addition of bmimBF(4) lead to the appearance of large-sized microemulsion droplet clusters (200-400 nm). NMR spectroscopic analysis reveal that the special structures and properties of bmimBF(4) and Triton X-100 together with the polar nature of toluene contribute to the formation of such self-assemblies. These unique self-assembled structures of IL-based microemulsion droplet clusters may have some unusual and unique properties with a number of interesting possibilities for potential applications.

  17. One-step separation of β-galactosidase from β-lactoglobulin using water-in-oil microemulsions.

    PubMed

    Mazı, Bekir G; Hamamcı, Haluk; Dungan, Stephanie R

    2012-05-01

    Solubilisation of β-galactosidase from Kluyveromyces lactis in Aerosol-OT water-in-isooctane microemulsions was measured as a function of buffer type and concentration, pH, and protein concentration. For buffer concentrations above ∼40mM, the enzyme was largely excluded from the droplets. Based on these results, a one-step separation was developed. A protein-containing aqueous feed was injected into an AOT/isooctane solution, with the feed volume slightly in excess of the predicted water solubility. Impurity proteins were entrapped inside the microemulsion droplets that then formed in the organic phase, while the high MW target protein was excluded and entered a newly formed, excess aqueous phase. The separation of β-galactosidase from the test protein β-lactoglobulin was most complete at 100mM KCl salt concentration, where the droplets were large enough to carry β-lactoglobulin but too small for β-galactosidase. At 100mM [KCl], 92% of the total enzyme activity was recovered in a concentrated and virtually pure form.

  18. Micelle, microemulsions, and gels for the conservation of cultural heritage.

    PubMed

    Baglioni, Piero; Berti, Debora; Bonini, Massimo; Carretti, Emiliano; Dei, Luigi; Fratini, Emiliano; Giorgi, Rodorico

    2014-03-01

    Past restorations performed with acrylic and vinyl polymers showed detrimental effects to wall paintings that lead to the complete disfiguration of the painted surfaces. The removal of these materials performed with the traditional solvent-based methodology represents a real challenge to conservators and usually achieves very poor results. This review reports on the new palette, nowadays available to restorers, based on microemulsions, micellar systems, physical and chemical gels specifically formulated for the cleaning of cultural heritage artefacts. These systems have been developed in the last twenty years within the cultural framework of colloids and surface science.

  19. Laminated sponges as challenging solid hydrophilic matrices for the buccal delivery of carvedilol microemulsion systems: Development and proof of concept via mucoadhesion and pharmacokinetic assessments in healthy human volunteers.

    PubMed

    Abd-Elbary, Ahmed; Makky, Amna M A; Tadros, Mina Ibrahim; Alaa-Eldin, Ahmed Adel

    2016-01-20

    Carvedilol (CVD) suffers from low absolute bioavailability (25%) due to its limited aqueous solubility and hepatic first-pass metabolism. Hydroxypropyl methylcellulose (HPMC) laminated buccal sponges loaded with CVD microemulsions (CVD-ME) were exploited to surmount such limitations. Six pseudoternary-phase diagrams were constructed using Capmul® MCM C8/Capmul® PG8, Tween® 80, propylene glycol and water. Six CVD-ME systems (0.625% w/v) were incorporated into HPMC core sponges backed with Ethocel® layers. The sponges were preliminary evaluated via FT-IR, DSC and XRD. The surface pH, morphology and in vitro drug release studies were evaluated. In vivo mucoadhesion and absorption studies of the best achieved laminated sponges (F4) were assessed in healthy volunteers. CVD-ME systems displayed nano-spherical clear droplets. The sponges showed interconnecting porous matrices through which CVD was dispersed in amorphous state. No intermolecular interaction was detected between CVD and HPMC. The surface pH values were almost neutral. The sponges loaded with CVD-ME systems showed more sustained-release profiles than those loaded with CVD-powder. Compared to Dilatrend® tablets, the significantly (P<0.05) higher bioavailability (1.5 folds), delayed Tmax and prolonged MRT(0-∞) unraveled the dual-potential of F4 sponges for water-insoluble drugs, like CVD, in improving drug oral bioavailability and in controlling drug release kinetics via buccal mucosa.

  20. Closed and open structure aggregates in microemulsions and mechanism of percolative conduction

    SciTech Connect

    Maitra, A.; Mathew, C.; Varshney, M. )

    1990-06-28

    The electrical conductivity and water self-diffusion coefficients of the oil-continuous microemulsions of Aerosol OT at the onset of the percolation process as well as in the bicontinuous system have been measured. Low self-diffusion coefficients of water indicate that the droplets maintain their closed shell structure. It has been concluded from the results that the percolative conduction arises due to the hopping of the charge carriers across the surfactant monolayer of the droplets, and the aggregates open up only at the onset of formation of bicontinuous microemulsions.

  1. Formation, thermodynamic properties, microstructures and antimicrobial activity of mixed cationic/non-ionic surfactant microemulsions with isopropyl myristate as oil.

    PubMed

    Bardhan, Soumik; Kundu, Kaushik; Das, Sajal; Poddar, Madhumita; Saha, Swapan K; Paul, Bidyut K

    2014-09-15

    Modification of the interface by blending of surfactants produces considerable changes in the elastic rigidity of the interface, which in turn affects the physicochemical properties of w/o microemulsions. Hence, it could be possible to tune the thermodynamic properties, microstructures and antimicrobial activity of microemulsions by using ionic/non-ionic mixed surfactants and polar lipophilic oil, which are widely used in biologically relevant systems. The present report was aimed at precise characterization of mixed cetyltrimethylammonium bromide and polyoxyethylene (23) lauryl ether microemulsions stabilized in 1-pentanol (Pn) and isopropyl myristate at different physicochemical conditions by employing phase studies, the dilution method, conductivity, DLS, FTIR (with HOD probing) and (1)H NMR measurements. Further, microbiological activities at different compositions were examined against two bacterial strains Bacillus subtilis and Escherichia coli at 303 K. The formation of mixed surfactant microemulsions was found to be spontaneous at all compositions, whereas it was endothermic at equimolar composition. FTIR and (1)H NMR measurements showed the existence of bulk-like, bound and trapped water molecules in confined environments. Interestingly, composition dependence of both highest and lowest inhibitory effects was observed against the bacterial strains, whereas similar features in spontaneity of microemulsion formation were also evidenced. These results suggested a close relationship between thermodynamic stability and antimicrobial activities. Such studies on polar lipophilic oil derived mixed surfactant microemulsions have not been reported earlier. Copyright © 2014 Elsevier Inc. All rights reserved.

  2. Assessment of the percutaneous penetration of indomethacin from soybean oil microemulsion: effects of the HLB value of mixed surfactants.

    PubMed

    Chen, Liangmei; Tan, Fengping; Wang, Jinfeng; Liu, Feng

    2012-01-01

    The objective of this study was to evaluate the influence of the ratios or the hydrophile-lipophile balance (HLB) values of Cremophor EL and Span 80 on the phase behavior of the O/W microemulsions and the percutaneous absorption and penetration of indomethacin microemulsions. The existence of microemulsion regions is investigated in quaternary systems composed of soybean oil/Cremophor EL and Span 80 (mixed surfactants)/diethylene glycol monoethyl ether (cosurfactant)/water by constructing pseudo-ternary phase diagrams at various Cremophor EL/Span 80 ratios. In addition, five microemulsion formulations with various mixed surfactants HLB values were evaluated by in vitro penetration experiments using mouse skin and Franz diffusion cells. The flux and amount of indomethacin penetration from 5 microemulsion formulations were significantly different from the control, and the enhance ratios ranged from 2.38 to 4.68 and 2.11 to 4.23, respectively. The HLB value of mixed surfactants in the formulations was a principal factor in determining the percutaneous penetration of the drug. The flux and amount of drug penetration increased gradually with increasing content of the lipophilic surfactant Span 80 and skin retention was highest for mixed surfactants with a HLB value of 7.6. Therefore, it is suggested that the presence of mixed surfactants was beneficial in the formation of O/W microemulsions and enhanced percutaneous penetration of indomethacin.

  3. Proton transport and the water environment in nafion fuel cell membranes and AOT reverse micelles.

    PubMed

    Spry, D B; Goun, A; Glusac, K; Moilanen, David E; Fayer, M D

    2007-07-04

    The properties of confined water and diffusive proton-transfer kinetics in the nanoscopic water channels of Nafion fuel cell membranes at various hydration levels are compared to water in a series of well-characterized AOT reverse micelles with known water nanopool sizes using the photoacid pyranine as a molecular probe. The side chains of Nafion are terminated by sulfonate groups with sodium counterions that are arrayed along the water channels. AOT has sulfonate head groups with sodium counterions that form the interface with the reverse micelle's water nanopool. The extent of excited-state deprotonation is observed by steady-state fluorescence measurements. Proton-transfer kinetics and orientational relaxation are measured by time-dependent fluorescence using time-correlated single photon counting. The time dependence of deprotonation is related to diffusive proton transport away from the photoacid. The fluorescence reflecting the long time scale proton transport has an approximately t-0.8 power law decay in contrast to bulk water, which has a t-3/2 power law. For a given hydration level of Nafion, the excited-state proton transfer and the orientational relaxation are similar to those observed for a related size AOT water nanopool. The effective size of the Nafion water channels at various hydration levels are estimated by the known size of the AOT reverse micelles that display the corresponding proton-transfer kinetics and orientational relaxation.

  4. Monitoring of urban air pollution from MODIS and AERONET Aerosol Optical Thickness (AOT) data

    NASA Astrophysics Data System (ADS)

    Tijani, K.; Chiaradia, M.; Guerriero, L.; Pasquariello, G.; Morea, A.; Nutricato, R.; Preziosa, G.

    2012-12-01

    Air pollution, caused by fuel industries and urban traffic and its environmental impact, are of considerable interest to studies in air quality. In this paper, the monitoring of the air pollution over urban areas in Italy through Aerosol Optical Thickness (AOT) data retrieved from Moderate Resolution Imaging Spectroradiometer (MODIS) measurements is presented. The high spatio-temporal frequency of MODIS AOT products (twice per day at 470nm, 1km full resolution) demonstrates that this satellite can be potentially used to routinely monitor the air pollution over land, especially urban area, which is the main source of aerosol particles. In this work AOT data derived by MODIS from November 2010 to February 2011 (winter period) and from May 2011 to August 2011 (summer period) were compared with AOT measurements from 6 different Aerosol Robotic Network (AERONET) stations over Italy (Bari, Lecce, Roma, Ispra, Potenza, Etna). The statistical analysis shows a good agreement between the ground based AOT measurements and the values retrieved using space based sensors, as shown in Figure 1. For all the stations the mean error is negligible, with a correlation ranging from 0.725 (in the worst case) to 0.96 (see Table 1). Moreover, LANDSAT-panchromatic images were used to discriminate urban and rural areas, based on the typical finger-like projections of urban land uses. The results of this study will be presented and commented. Acknowledgements This work was funded by Apulian Region in the framework of the ECOURB project. (Analisi e Modelli di inquinamento atmosferico e termico per sistemi di ECOlabeling URBano, 2009-2012). Figure 1: Scatter plot between AOT derived from MODIS and AERONET for Lecce City in summer period from May 2011 to August 2011. Y = - 0.023+0.86x (fit) ; Table 1: Statistical Analysis Report on the difference between AOT derived from MODIS and AERONET from May 2011 to August 2011 (summer period) for 6 different Aerosol Robotic Network (AERONET) stations

  5. Solvation dynamics of coumarin 153 embedded in AOT + phenol organogels studied by time-resolved fluorescence spectroscopy

    NASA Astrophysics Data System (ADS)

    Nishiyama, Katsura; Takata, Kei; Watanabe, Keiichi; Shigematsu, Hirotake

    2012-03-01

    We investigate solvation dynamics of organogel utilizing ps-ns fluorescence spectroscopy. The organogel studied in this Letter comprises bis(2-ethylhexyl) sulfosuccinate (AOT) and p-chlorophenol in the m-xylene solvent, that produce an organogel architecture with self-assembly. Within the organogel, an emitting probe, coumarin 153 (C153), is embedded. We then obtain dynamic response functions of solvation derived from the time-resolved fluorescence spectra of C153. We propose that total energy of the C153-organogel system relaxes with a relaxation time of 3.9 ns, whereas the entire rearrangement of the organogel structure around C153 is achieved with that of 6.1 ns, respectively.

  6. Formation of hollow silica nanospheres by reverse microemulsion

    NASA Astrophysics Data System (ADS)

    Lin, Cheng-Han; Chang, Jen-Hsuan; Yeh, Yi-Qi; Wu, Si-Han; Liu, Yi-Hsin; Mou, Chung-Yuan

    2015-05-01

    Uniform hollow silica nanospheres (HSNs) synthesized with reverse microemulsion have great application potential as nanoreactors because enzymes or nanocatalysts can be easily encapsulated de novo in synthesis. Water-in-oil (w/o) reverse microemulsions comprising the polymeric surfactant polyoxyethylene (5) isooctylphenyl ether (Igepal CA-520), ammonia and water in a continuous oil phase (alkanes) coalesce into size-tunable silica nanoparticles via diffusion aggregation after the introduction of silica precursors. Here, we elucidate in detail the growth mechanism for silica nanoparticles via nucleation of ammonium-catalyzed silica oligomers from tetraethylorthosilicate (TEOS) and nanoporous aminopropyltrimethoxy silane (APTS) in the reverse microemulsion system. The formation pathway was studied in situ with small-angle X-ray scattering (SAXS). We find a four-stage process showing a sigmoidal growth behavior in time with a crossover from the induction period, early nucleation stage, coalescence growth and a final slowing down of growth. Various characterizations (TEM, N2 isotherm, dynamic light scattering, zeta potential, NMR, elemental analysis) reveal the diameters, scattering length density (SLD), mesoporosity, surface potentials and chemical compositions of the HSNs. Oil phases of alkanes with different alkyl chains are systematically employed to tune the sizes of HSNs by varying oil molar volumes, co-solvent amounts or surfactant mixture ratios. Silica condensation is incomplete in the core region, with the silica source of TEOS and APTS leading to the hollow silica nanosphere after etching with warm water.Uniform hollow silica nanospheres (HSNs) synthesized with reverse microemulsion have great application potential as nanoreactors because enzymes or nanocatalysts can be easily encapsulated de novo in synthesis. Water-in-oil (w/o) reverse microemulsions comprising the polymeric surfactant polyoxyethylene (5) isooctylphenyl ether (Igepal CA-520), ammonia and

  7. Reversible switching of amphiphilic self-assemblies between micelles and microemulsions by a thermal stimulus.

    PubMed

    Dong, Bin; Xing, Xueqing; Wang, Rui; Wang, Bing; Zhou, Xiaoyan; Wang, Chang; Yu, Li; Wu, Zhonghua; Gao, Yanan

    2015-07-14

    The ionic liquid (IL), tetrabutylphosphonium trifluoroacetate ([P4444][CF3COO]), showed a low critical solution temperature (LCST)-type phase transition in water. Using this temperature-sensitive IL and the Triton X-100/H2O system, the reversible transformation between micelles and microemulsions was thus realized by a thermal stimulus for the first time.

  8. Microemulsion extrusion technique: a new method to produce lipid nanoparticles

    NASA Astrophysics Data System (ADS)

    de Jesus, Marcelo Bispo; Radaic, Allan; Zuhorn, Inge S.; de Paula, Eneida

    2013-10-01

    Solid lipid nanoparticles (SLN) and nanostructured lipid carriers (NLC) have been intensively investigated for different applications, including their use as drug and gene delivery systems. Different techniques have been employed to produce lipid nanoparticles, of which high pressure homogenization is the standard technique that is adopted nowadays. Although this method has a high efficiency, does not require the use of organic solvents, and allows large-scale production, some limitations impede its application at laboratory scale: the equipment is expensive, there is a need of huge amounts of surfactants and co-surfactants during the preparation, and the operating conditions are energy intensive. Here, we present the microemulsion extrusion technique as an alternative method to prepare lipid nanoparticles. The parameters to produce lipid nanoparticles using microemulsion extrusion were established, and the lipid particles produced (SLN, NLC, and liposomes) were characterized with regard to size (from 130 to 190 nm), zeta potential, and drug (mitoxantrone) and gene (pDNA) delivery properties. In addition, the particles' in vitro co-delivery capacity (to carry mitoxantrone plus pDNA encoding the phosphatase and tensin homologue, PTEN) was tested in normal (BALB 3T3 fibroblast) and cancer (PC3 prostate and MCF-7 breast) cell lines. The results show that the microemulsion extrusion technique is fast, inexpensive, reproducible, free of organic solvents, and suitable for small volume preparations of lipid nanoparticles. Its application is particularly interesting when using rare and/or costly drugs or ingredients (e.g., cationic lipids for gene delivery or labeled lipids for nanoparticle tracking/diagnosis).

  9. Ionic liquid-in-oil microemulsions.

    PubMed

    Eastoe, Julian; Gold, Sarah; Rogers, Sarah E; Paul, Alison; Welton, Tom; Heenan, Richard K; Grillo, Isabelle

    2005-05-25

    Phase stability and small-angle neutron scattering (SANS) data show that surfactant-stabilized nanodomains of a typical ionic liquid (1-butyl-3-methylimidazolium tetrafluoroborate [bmim][BF4]) may be dispersed by the nonionic surfactant Triton-X100 in cyclohexane. Analyses of these SANS data are consistent with the formation of ionic liquid-in-oil microemulsion droplets.

  10. Ionic Liquid-Based Microemulsions in Catalysis

    PubMed Central

    2016-01-01

    The design and properties of surface-active ionic liquids that are able to form stable microemulsions with heptane and water are presented, and their promise as reaction media for thermomorphic palladium-catalyzed cross-coupling reactions is demonstrated. PMID:27978714

  11. Hexatic and Microemulsion Phases in the 2d Quantum Plasma

    NASA Astrophysics Data System (ADS)

    Clark, Bryan; Casula, Michele; Ceperley, David

    2009-03-01

    It has been long known that the two-dimensional one component plasma supports both a Wigner-crystal and liquid phase. Classically [1,2], it is known that a hexatic phase exists but it is not known how this hexatic phase extends into the quantum regime. Moreover, at low temperature, phenomenological arguments [3] from Jamei, et. al. suggest the existence of microemulsion phases including stripes and bubbles. We use diffusion and path integral Monte Carlo to map out this phase diagram. We are able to extend the hexatic phase into the quantum regime as well as quantify the nature of the defects and exponents in the long range quantum system. We also specify the the nature, extent and existence (or lack thereof) of the expected low-T microemulsion phases. [0pt] [1] Muto, S. & Aoki, H. Crystallization of a classical two-dimensional electron system: Positional and orientational orders. Phys. Rev. B 59, 14911(1999).[0pt] [2] He, W.J. et al. Phase transition in a classical two-dimensional electron system. Phys. Rev. B 68, 195104(2003).[0pt] [3] Jamei, R., Kivelson, S. & Spivak, B. Universal Aspects of Coulomb-Frustrated Phase Separation. Phys. Rev. Lett. 94, 056805-4(2005).

  12. Characterization of caprylocaproyl macrogolglycerides based microemulsion drug delivery vehicles for an amphiphilic drug.

    PubMed

    Djordjevic, Ljiljana; Primorac, Marija; Stupar, Mirjana; Krajisnik, Danina

    2004-03-01

    Microemulsion systems composed of water, isopropyl myristate, PEG-8 caprylic/capric glycerides (Labrasol), and polyglyceryl-6 dioleate (Plurol Oleique), were investigated as potential drug delivery vehicles for an amphiphilic model drug (diclofenac diethylamine). Pseudo-ternary phase diagram of the investigated system, at constant surfactant/cosurfactant mass ratio (Km 4:1) was constructed at room temperature by titration, and the oil-to-surfactant/cosurfactant mass ratios (O/SC) that exhibit the maximum in the solubilization of water were found. This allowed the investigation of the continuous structural inversion from water-in-oil to oil-in-water microemulsions on dilution with water phase. Furthermore, electrical conductivity (sigma) of the system at Km 1:4, and O/SC 0.250 was studied, and the percolation phenomenon was observed. Conductivity and apparent viscosity (eta') measurement results well described colloidal microstructure of the selected formulations, including gradual changes during their formation. Moreover, sigma, eta', and pH values of six selected microemulsion vehicles which differ in water phase volume fraction (phi(w)) at the selected Km and O/SC values, were measured. In order to investigate the influence of the amphiphilic drug on the vehicle microstructures, each system was formulated with 1.16% (w/w) diclofenac diethylamine. Electrical conductivity, and eta' of the investigated systems were strongly affected by drug incorporation. The obtained results suggest that diclofenac diethylamine interacts with the specific microstructure of the investigated vehicles, and that the different drug release kinetics from these microemulsions may be expected. The investigated microemulsions should be very interesting as new drug carrier systems for dermal application of diclofenac diethylamine.

  13. An enhanced VIIRS aerosol optical thickness (AOT) retrieval algorithm over land using a global surface reflectance ratio database

    NASA Astrophysics Data System (ADS)

    Zhang, Hai; Kondragunta, Shobha; Laszlo, Istvan; Liu, Hongqing; Remer, Lorraine A.; Huang, Jingfeng; Superczynski, Stephen; Ciren, Pubu

    2016-09-01

    The Visible/Infrared Imager Radiometer Suite (VIIRS) on board the Suomi National Polar-orbiting Partnership (S-NPP) satellite has been retrieving aerosol optical thickness (AOT), operationally and globally, over ocean and land since shortly after S-NPP launch in 2011. However, the current operational VIIRS AOT retrieval algorithm over land has two limitations in its assumptions for land surfaces: (1) it only retrieves AOT over the dark surfaces and (2) it assumes that the global surface reflectance ratios between VIIRS bands are constants. In this work, we develop a surface reflectance ratio database over land with a spatial resolution 0.1° × 0.1° using 2 years of VIIRS top of atmosphere reflectances. We enhance the current operational VIIRS AOT retrieval algorithm by applying the surface reflectance ratio database in the algorithm. The enhanced algorithm is able to retrieve AOT over both dark and bright surfaces. Over bright surfaces, the VIIRS AOT retrievals from the enhanced algorithm have a correlation of 0.79, mean bias of -0.008, and standard deviation (STD) of error of 0.139 when compared against the ground-based observations at the global AERONET (Aerosol Robotic Network) sites. Over dark surfaces, the VIIRS AOT retrievals using the surface reflectance ratio database improve the root-mean-square error from 0.150 to 0.123. The use of the surface reflectance ratio database also increases the data coverage of more than 20% over dark surfaces. The AOT retrievals over bright surfaces are comparable to MODIS Deep Blue AOT retrievals.

  14. Surfactant-free microemulsions of 1-butyl-3-methylimidazolium hexafluorophosphate, propylamine nitrate, and water.

    PubMed

    Xu, Jie; Deng, Huanhuan; Fu, Yunlei; Chen, Yuquan; Zhang, Jing; Hou, Wanguo

    2017-03-08

    Generally, surfactants (or amphiphiles) are believed to be necessary components of microemulsions. However, it has been demonstrated that, in the absence of traditional surfactants, microemulsions can also form from a ternary system of two immiscible fluids (i.e., oil and water phases) and an amphi-solvent, but the current understanding of such surfactant-free microemulsions (SFMEs) is very limited. Herein, we report an SFME consisting of the hydrophobic ionic liquid (IL) 1-butyl-3-methylimidazolium hexafluorophosphate (bmimPF6), the protic IL propylamine nitrate (PAN), and water, in which bmimPF6 and PAN are used as the oil phase and the amphi-solvent, respectively. The microstructures and structural transitions of the SFME were investigated using cyclic voltammetry, fluorescence spectroscopy, and ultraviolet-visible spectroscopy. The SFME exhibited water-in-bmimPF6 (W/IL), bicontinuous (BC), and bmimPF6-in-water (IL/W) microstructures, depending on the composition of the ternary system, similar to the case of traditional surfactant-based microemulsions (SBMEs). The three kinds of microstructures were confirmed by cryogenic transmission electron microscopy (cryo-TEM) observations. To the best of our knowledge, this is the first report on SFMEs composed of two ILs as components, especially where one is used as the amphi-solvent.

  15. Enhanced intestinal absorption of daidzein by borneol/menthol eutectic mixture and microemulsion.

    PubMed

    Shen, Qi; Li, Xi; Li, Wenji; Zhao, Xinyi

    2011-12-01

    In the present study, the effect of a borneol/menthol eutectic mixture (25:75) and microemulsion on the absorption of daidzein in rat intestinal membrane was evaluated. The microemulsion formulation was composed of ethyl oleate (oil), Cremophor RH40 (surfactant), PEG400 (co-surfactant), and water. The borneol/menthol eutectic mixture and its microemulsion were found to enhance the intestinal absorption of daidzein in vitro. A diffusion chamber system with isolated rat intestinal membranes was used. In contrast, verapamil (0.3 mM), a typical P-glycoprotein inhibitor, showed no effect on the absorption of daidzein by this system. A pharmacokinetic study was conducted in rats. After oral administration of daidzein at a dose of 10 mg/kg in the form of either borneol/menthol eutectic mixtures or suspension, the relative bioavailability of borneol/menthol eutectic mixtures and microemulsion was enhanced by about 1.5- and 3.65-fold, respectively, compared with a daidzein suspension. In conclusion, a borneol/menthol eutectic mixture can enhance the absorption of daidzein, although the mechanism of absorption enhancement is still unclear.

  16. Influence of high intensity sweeteners and sugar alcohols on a beverage microemulsion.

    PubMed

    Marcus, Julien; Wolfrum, Stefan; Touraud, Didier; Kunz, Werner

    2015-12-15

    The present paper shows the effects of added sugars and sweeteners on the clearing temperature of a highly water dilutable fatty acid salt microemulsion used as a model of a beverage concentrate. There is a twofold interest in this work. The first one is practical and relates to the fact that many fatty acid salt surfactants can be used in food without major regulatory restrictions. As is shown here, they allow making highly stable microemulsions even at neutral and acidic pH. The second one is more of scientific interest. The model system can be used to study the effect of sugars and sweeteners on the formulation stability depending on their charges, amphiphilic properties, and localization in the microemulsion interfacial film. An important practical result is the discovery of the possibility to formulate highly dilutable microemulsions at neutral or slightly acid pH with a good taste in presence of sucralose. Further, a significant decrease of the pKA of the fatty acid is observed in presence of stevia, thus allowing transparent, fairly stable systems at neutral pH.

  17. Microemulsion formation and phase behavior of anionic and cationic surfactants with sodium dodecyl sulfate and cetyltrimethylammonium bromide

    SciTech Connect

    Li, X.; Lin, E.; Zhao, G.; Xiao, T.

    1996-12-01

    The phase behavior and solubilization of multiphase microemulsions in mixed anionic-cationic surfactant systems were studied for fixed ratio of water-to-oil and surfactant-to-alcohol. In the mixed surfactants (sodium dodecyl sulfate + cetyltrimethylammonium bromide)/heptane/alcohol/water systems, microemulsions and birefringement phases are formed by adjusting the surfactant ratio {epsilon} and the cationic weight fraction {delta}. The bicontinuous (or w/o microemulsion) {yields} birefringement o/w microemulsion transition takes place and microemulsion domain enlarges with increasing {epsilon}. The optimum surfactant concentration {gamma} increases and the corresponding optimum {delta} decreases with increasing {epsilon} and both of them decrease with increasing the alcohol chain length butanol to hexanol. The birefringent region shrinks rapidly with increasing alcohol and/or CTAB weight fractions in total surfactant concentration. Conductivity measurements have been performed in the single-phase region of the system containing mixed surfactants and alcohols at 25 C. The conductivity results indicate where a transition takes place and which of these different types of phase structures may be in the single-phase of the system containing anionic-cationic mixed surfactants.

  18. Phase behavior and microstructure of microemulsions with a room-temperature ionic liquid as the polar phase.

    PubMed

    Atkin, Rob; Warr, Gregory G

    2007-08-09

    Microemulsions of nonionic alkyl oligoethyleneoxide (CiEj) surfactants, alkanes, and ethylammonium nitrate (EAN), a room-temperature ionic liquid, have been prepared and characterized. Studies of phase behavior reveal that EAN microemulsions have many features in common with corresponding aqueous systems, the primary difference being that higher surfactant concentrations and longer surfactant tailgroups are required to offset the decreased solvophobicity the surfactant molecules in EAN compared with water. The response of the EAN microemulsions to variation in the length of the alkane, surfactant headgroup, and surfactant tailgroup has been found to parallel that observed in aqueous systems in most instances. EAN microemulsions exhibit a single broad small-angle X-ray scattering peak, like aqueous systems. These are well described by the Teubner-Strey model. A lamellar phase was also observed for surfactants with longer tails at lower temperatures. The scattering peaks of both microemulsion and lamellar phases move to lower wave vector on increasing temperature. This is ascribed to a decrease in the interfacial area of the surfactant layer. Phase behavior, small-angle X-ray scattering, and conductivity experiments have allowed the weakly to strongly structured transition to be identified for EAN systems.

  19. Mechanisms of microemulsion enhancing the oral bioavailability of puerarin: comparison between oil-in-water and water-in-oil microemulsions using the single-pass intestinal perfusion method and a chylomicron flow blocking approach

    PubMed Central

    Tang, Tian-Tian; Hu, Xiong-Bin; Liao, De-Hua; Liu, Xin-Yi; Xiang, Da-Xiong

    2013-01-01

    The purpose of the present work was to determine the mechanisms by which microemulsions (MEs) enhance the oral bioavailability of puerarin. The in situ perfusion method was used in rats to study the absorption mechanisms of an oil-in-water (O/W) microemulsion (O/W-ME) and a water-in-oil (W/O) microemulsion (W/O-ME). The possibility of lymphatic transport of the MEs was investigated using a chylomicron flow blocking approach. The results for the absorption mechanisms in the stomach and intestines indicated that the absorption characteristics of the O/W-ME and W/O-ME depend on the segment. The W/O-ME had higher internal membrane permeability than the O/W-ME. The results of the lymphatic transport analyses showed that both the O/W-ME and W/O-ME underwent lymphatic transport and that this pathway was a major contributor to the oral bioavailability of MEs. Furthermore, the type of ME can significantly affect the absorption of puerarin through the lymphatic system due to the oil content and the form of the microemulsion after oral administration. In conclusion, these data indicate that microemulsions are an effective and promising delivery system to enhance the oral bioavailability of poorly water-soluble drugs. PMID:24277986

  20. Buffering the aqueous phase pH in water-in-CO{sub 2} microemulsions

    SciTech Connect

    Holmes, J.D.; Ziegler, K.J.; Audriani, M.; Lee, C.T. Jr.; Bhargava, P.A.; Johnston, K.P.; Steytler, D.C.

    1999-07-08

    Water-in-oil (w/o) microemulsions have been exploited for use in a wide range of applications, including chemical and enzymatic reactions, protein and metal extraction, and the production of nanoparticles. Microemulsions are attractive systems for studying such applications because they have the ability to function as a universal solvent medium by solubilizing high concentrations of both polar and apolar molecules within their dispersed aqueous and continuous oil phases, respectively. The addition of organic and inorganic buffers to nanometer size water-in-CO{sub 2} microemulsion droplets stabilized by ammonium perfluoropolyether (PFPE-NH{sub 4}) results in an increase in pH from 3 to values of 5--7. The effects of temperature, pressure, buffer type, buffer concentration, ionic strength, and CO{sub 2} solubility on the pH inside water-in-CO{sub 2} microemulsions and on biphasic water-CO{sub 2} systems were measured by the hydrophilic indicator 4-nitrophenyl-2-sulfonate and were predicted accurately with thermodynamic models. In both systems, modest buffer loadings result in a steep pH jump from 2.5 pH units. Further increases in pH require large amounts of base to overcome buffering due to the carbonic acid-bicarbonate equilibrium. A pH approaching neutrality was obtained in w/c microemulsions with approximately 1.5 mol kg{sup {minus}1} NaOH. At high buffer loadings, the effects of temperature and pressure on pH values are negligible.

  1. Utilization of Microemulsions from Rhinacanthus nasutus (L.) Kurz to Improve Carotenoid Bioavailability.

    PubMed

    Ho, Nai-Hsing; Inbaraj, Baskaran Stephen; Chen, Bing-Huei

    2016-05-06

    Carotenoids have been known to reduce the risk of several diseases including cancer and cardiovascular. However, carotenoids are unstable and susceptible to degradation. Rhinacanthus nasutus (L.) Kurz (R. nasutus), a Chinese medicinal herb rich in carotenoids, was reported to possess vital biological activities such as anti-cancer. This study intends to isolate carotenoids from R. nasutus by column chromatography, identify and quantify by HPLC-MS, and prepare carotenoid microemulsions for determination of absolute bioavailability in rats. Initially, carotenoid fraction was isolated using 250 mL ethyl acetate poured into an open-column packed with magnesium oxide-diatomaceous earth (1:3, w/w). Fourteen carotenoids including internal standard β-apo-8'-carotenal were resolved within 62 min by a YMC C30 column and gradient mobile phase of methanol-acetonitrile-water (82:14:4, v/v/v) and methylene chloride. Highly stable carotenoid microemulsions were prepared using a mixture of Capryol(TM)90, Transcutol®HP, Tween 80 and deionized water, with the mean particle being 10.4 nm for oral administration and 10.7 nm for intravenous injection. Pharmacokinetic study revealed that the absolute bioavailability of carotenoids in microemulsions and dispersion was 0.45% and 0.11%, respectively, while a much higher value of 6.25% and 1.57% were shown for lutein, demonstrating 4-fold enhancement in bioavailability upon incorporation of R. nasutus carotenoids into a microemulsion system.

  2. Understanding and optimizing microemulsions with magnetic room temperature ionic liquids (MRTILs).

    PubMed

    Klee, Andreas; Prevost, Sylvain; Gasser, Urs; Gradzielski, Michael

    2015-03-12

    Nonaqueous microemulsions containing the magnetic room temperature ionic liquid (MRTIL) bmimFeCl4 as polar phase were studied with respect to their macroscopic phase behavior and structure by means of small angle neutron scattering (SANS). The phase behavior was studied in detail for different alcohols as cosurfactant and different oils as nonpolar phase and mainly by varying the chain length of the used ionic surfactant (CnmimCl with n = 14, 16, 18). In general, phase behavior and structural ordering in the mesophases were found to be comparable to water systems where with increasing content of MRTIL the microemulsions seems to become less and less structured leading to a rough and softer interface with less long-range ordering. The extent of structuring increases with increasing chain length of the surfactant. However, the pure surfactant is not able to form microemulsions and a rather large amount of alcohol is required for stabilization, where the effectiveness of the alcohol increases with increasing chain length of the alcohol. From this comprehensive investigation systematic trends can be deduced in order to formulate correspondingly structured microemulsions with MRTIL as polar phase.

  3. Highly concentrated emulsified microemulsions as solvent-free plant protection formulations.

    PubMed

    Engelskirchen, Sandra; Maurer, Reinhard; Levy, Tatjana; Berghaus, Rainer; Auweter, Helmut; Glatter, Otto

    2012-12-15

    Effective plant protection agents are readily available and well implemented in industry. However, delivery to the plant and application on the leaf are processes that still need to be optimized. Up to now plant protection formulations represent either emulsion or suspension concentrates that often contain environmentally harmful organic solvents and/or adjuvants. Emulsified microemulsions are hierarchically organized systems comprising emulsion droplets that confine a water-in-oil microemulsion. In the present contribution we show that emulsified microemulsions prepared from environmentally friendly components can be loaded with the plant-protection agent Fenpropimorph® up to 48 wt.% without organic solvent. The emulsion itself is highly concentrated, containing 60 wt.% of dispersed phase, and can be readily diluted with water for spraying in farming applications. Small-angle X-ray measurements reveal the existence of a water-in-Fenpropimorph® microemulsion confined inside the emulsion droplets. Dynamic light scattering shows that the emulsions prepared are monomodal, comprising droplet radii in the hundred nanometer range.

  4. In Vivo Evaluation of Transdermal Iodide Microemulsion for Treating Iodine Deficiency Using Sprague Dawley Rats.

    PubMed

    Alayoubi, Alaadin; Sullivan, Ryan D; Lou, Hao; Patel, Hemlata; Mandrell, Timothy; Helms, Richard; Almoazen, Hassan

    2016-06-01

    The objective of this study was to evaluate the transdermal efficiency of iodide microemulsion in treating iodine deficiency using rats as an animal model. Animals were fed either iodine-deficient diet (20 μg/kg iodide) or control diet (200 μg/kg iodide) over a 17-month period. At month 14, iodide microemulsion was applied topically in iodine-deficient group and physiological evaluations of thyroid gland functions were characterized by monitoring the thyroid hormones (T3, T4), thyroid-stimulating hormone (TSH), iodide ion excretion in urine, and the overall rat body weights in both groups. Moreover, morphological evaluations of thyroid gland before and after treatment were performed by ultrasound imaging and through histological assessment. Prior to microemulsion treatment, the levels of T3, T4, and TSH in iodine-deficient group were statistically significant as compared to that in the control group. The levels of T3 and T4 increased while TSH level decreased significantly in iodine-deficient group within the first 4 weeks of treatment. After treatment, iodide concentration in urine increased significantly. There was no statistical difference in weight between the two groups. Ultrasound imaging and histological evaluations showed evidence of hyperplasia in iodine-deficient group. Topical iodide microemulsion has shown a promising potential as a novel delivery system to treat iodine deficiency.

  5. Fluctuation mechanism of the dielectric polarization of water-in-oil microemulsions with ionic surfactant

    NASA Astrophysics Data System (ADS)

    Kozlovich, Nick; Puzenko, Alexander; Alexandrov, Yuriy; Feldman, Yuri

    1998-08-01

    A statistical model is proposed to describe the dielectric polarization of ionic microemulsions at a region far below percolation in which the microemulsions consist of spherical single droplets with water in the central core surrounded by a layer of surfactant molecules. The model describes the effect of temperature and dispersed phase content on the behavior of the dielectric polarization of ionic water-in-oil microemulsions and explains the experimentally observed increase of the static dielectric permittivity as a function of temperature. The microemulsions formed with surfactant sodium bis(2-ethylhexyl) sulfosuccinate have been analyzed with the help of this model. The systems are considered to consist of nanometer-sized spherical noninteracting water droplets of equal size with negatively charged head groups, staying at the interface, and positive counterions, distributed in the electrical diffuse double layer of the droplet interior. It is shown that the droplet polarizability is proportional to the mean-square fluctuation dipole moment of the droplet. This mean-square dipole moment and the corresponding value of the dielectric increment depend on the equilibrium distribution of counterions within a diffuse double layer. The density distribution of ions is determined by the degree of the dissociation of the ionic surfactant. The relationship between the dielectric permittivity, the constant of dissociation of surfactant, the content of the dispersed phase, and the temperature has been ascertained.

  6. Role of mucoadhesive polymers in enhancing delivery of nimodipine microemulsion to brain via intranasal route.

    PubMed

    Pathak, Rudree; Prasad Dash, Ranjeet; Misra, Manju; Nivsarkar, Manish

    2014-04-01

    Intranasal drug administration is receiving increased attention as a delivery method for bypassing the blood-brain barrier and rapidly targeting therapeutics to the CNS. However, rapid mucociliary clearance in the nasal cavity is a major hurdle. The purpose of this study was to evaluate the effect of mucoadhesive polymers in enhancing the delivery of nimodipine microemulsion to the brain via the intranasal route. The optimized mucoadhesive microemulsion was characterized, and the in vitro drug release and in vivo nasal absorption of drug from the new formulation were evaluated in rats. The optimized formulation consisted of Capmul MCM as oil, Labrasol as surfactant, and Transcutol P as co-surfactant, with a particle size of 250 nm and zeta potential value of -15 mV. In vitro and ex vivo permeation studies showed an initial burst of drug release at 30 min and sustained release up to 6 h, attributable to the presence of free drug entrapped in the mucoadhesive layer. In vivo pharmacokinetic studies in rats showed that the use of the mucoadhesive microemulsion enhanced brain and plasma concentrations of nimodipine. These results suggest that incorporation of a mucoadhesive agent in a microemulsion intranasal delivery system can increase the retention time of the formulation and enhance brain delivery of drugs.

  7. Structural characterization of glass-forming oil/water microemulsions by neutron scattering

    NASA Astrophysics Data System (ADS)

    Alba-Simionesco, C.; Teixeira, J.; Angell, C. A.

    1989-07-01

    Small angle neutron scattering (SANS) has been used to establish the dispersed droplet character of a class of pseudo-three-component oil/water (o/w) microemulsions which can be cooled continuously into the glassy state without either crystallization or microemulsion destabilization. SANS of toluene microemulsions at low volume fractions (˜0.5%) of toluene indicate a droplet radius of 270±10 Å. At normal concentrations (˜33 vol % oil), the droplet size cannot be determined precisely but the presence of a droplet state of small polydispersity is established for toluene, p-xylene, benzene, CS2, and CCl4 by the presence of a sharp peak in the scattered neutron intensity vs Q plots. Average interdroplet separations range from 200 to 300 Å, implying average radii of ˜125 Å. Such radii are consistent with freeze-fracture electron microscope studies of the same or similar systems. Variable temperature studies on toluene microemulsions during both cooling and warming cycles in the temperature range ambient to 100 K, show only minor (˜10%) changes in the interdroplet separation down to 220 K at which temperature diffusion through the viscous matrix phase becomes too slow to permit further emulsion structure changes on the time scale of the cooling experiment. The origin, and some possible exploitations, of this unusual stability against temperature change are discussed.

  8. Antifungal activity of topical microemulsion containing a thiophene derivative

    PubMed Central

    Guimarães, Geovani Pereira; de Freitas Araújo Reis, Mysrayn Yargo; da Silva, Dayanne Tomaz Casimiro; Junior, Francisco Jaime Bezerra Mendonça; Converti, Attílio; Pessoa, Adalberto; de Lima Damasceno, Bolívar Ponciano Goulart; da Silva, José Alexsandro

    2014-01-01

    Fungal infections have become a major problem of worldwide concern. Yeasts belonging to the Candida genus and the pathogenic fungus Cryptococcus neoformans are responsible for different clinical manifestations, especially in immunocompromised patients. Antifungal therapies are currently based on a few chemotherapeutic agents that have problems related to effectiveness and resistance profiles. Microemulsions are isotropic, thermodynamically stable transparent systems of oil, water and surfactant that can improve the solubilization of lipophilic drugs. Taking into account the need for more effective and less toxic drugs along with the potential of thiophene derivatives as inhibitors of pathogenic fungi growth, this study aimed to evaluate the antifungal activity of a thiophene derivative (5CN05) embedded in a microemulsion (ME). The minimum inhibitory concentration (MIC) was determined using the microdilution method using amphotericin B as a control. The formulations tested (ME- blank and ME-5CN05) showed physico-chemical properties that would allow their use by the topical route. 5CN05 as such exhibited moderate or weak antifungal activity against Candida species (MIC = 270–540 μg.mL−1) and good activity against C. neoformans (MIC = 17 μg.mL−1). Candida species were susceptible to ME-5CN05 (70–140 μg.mL−1), but C. neoformans was much more, presenting a MIC value of 2.2 μg.mL−1. The results of this work proved promising for the pharmaceutical industry, because they suggest an alternative therapy against C. neoformans. PMID:25242940

  9. Environmentally friendly ionic liquid-in-water microemulsions for extraction of hydrophilic and lipophilic components from Flos Chrysanthemi.

    PubMed

    Chen, Jue; Cao, Jun; Gao, Wen; Qi, Lian-Wen; Li, Ping

    2013-10-21

    Ionic liquids (ILs) have numerous chemical applications as environmentally green solvents that are extending into microemulsion applications. In this work, a novel benign IL-in-water microemulsion system modified by an IL surfactant has been proposed for simultaneous extraction of hydrophilic and lipophilic constituents from Flos Chrysanthemi (Chrysanthemum morifolium). Constituents were analyzed by rapid-resolution liquid chromatography coupled with quadrupole time-of-flight mass spectrometry. A mixture-design approach was used to optimize the IL surfactant and the IL oil phase in the microemulsion system. Microemulsions consisting of 6.0% 1-dodecyl-3-methylimidazolium hydrogen sulfate, 0.1% 1-vinyl-3-methylimidazolium hexafluorophosphate and 93.9% water offered the acceptable extract efficiency that are comparable to or even better than conventional volatile organic solvents. This assay was fully validated with respect to the linearity of response (r(2) > 0.999 over two orders of magnitude), precision (intra-RSD < 0.49 and inter-day RSD < 2.21), and accuracy (recoveries ranging from 93.73% to 101.84%). The proposed IL-in-water microemulsion method provided an environmentally friendly alternative for efficient extraction of compounds from Flos Chrysanthemi and could be extended to complex environmental and pharmaceutical samples.

  10. Propylammonium nitrate as a solvent for amphiphile self-assembly into micelles, lyotropic liquid crystals, and microemulsions.

    PubMed

    Atkin, Rob; Bobillier, Sophie M C; Warr, Gregory G

    2010-01-28

    The phase behavior and self-assembled microstructures of a range of oligo(oxyethylene)-n-alkyl ether (C(i)E(j)) surfactants has been investigated in propylammonium nitrate (PAN), a room temperature ionic liquid. Micelles and single-phase microemulsions were all found to form at alkyl chain lengths from dodecyl to octadecyl, and lyotropic liquid crystals formed with hexadecyl chains or longer. Small-angle neutron scattering (SANS) shows that self-assembly occurs by solvophobic interactions driving the aggregation of the alkyl chains, but several results indicate that these are weaker in PAN than in water or ethylammonium nitrate, due chiefly to the hydrophobicity of PAN. Longer alkyl chains are needed for lyotropic liquid crystals to form, and higher surfactant concentrations are needed to form a single phase microemulsion. Conductivity shows these microemulsions to be weakly structured, and relatively insensitive to oil or surfactant molecular structure, unlike water-based systems. However, SANS contrast variation reveals a nanosegregation of oil from the alkyl tails of surfactants within the microemulsion, and may suggest a cosurfactant-like role for the propylammonium cation. Molecular areas within microemulsions and lamellar phases are larger than corresponding water- or ethylammonium nitrate-based systems due to the large molecular volume of the solvating PANs.

  11. Characterization of microemulsion structures in the pseudoternary phase diagram of isopropyl palmitate/water/Brij 97:1-butanol.

    PubMed

    Boonme, Prapaporn; Krauel, Karen; Graf, Anja; Rades, Thomas; Junyaprasert, Varaporn Buraphacheep

    2006-05-12

    This research was aimed to characterize microemulsion systems of isopropyl palmitate (IPP), water, and 2:1 Brij 97 and 1-butanol by different experimental techniques. A pseudoternary phase diagram was constructed using water titration method. At 45% wt/wt surfactant system, microemulsions containing various ratios of water and IPP were prepared and identified by electrical conductivity, viscosity, differential scanning calorimetry (DSC), cryo-field emission scanning electron microscopy (cryo-FESEM) and nuclear magnetic resonance (NMR). The results from conductivity and viscosity suggested a percolation transition from water-in-oil (water/oil) to oil-in-water (oil/water) microemulsions at 30% wt/wt water. From DSC results, the exothermic peak of water and the endothermic peak of IPP indicated that the transition of water/oil to oil/water microemulsions occurred at 30% wt/wt water. Cryo-FESEM photomicrographs revealed globular structures of microemulsions at higher than 15% wt/wt water. In addition, self-diffusion coefficients determined by NMR reflected that the diffusability of water increased at higher than 35% wt/wt water, while that of IPP was in reverse. Therefore, the results from all techniques are in good agreement and indicate that the water/oil and oil/water transition point occurred in the range of 30% to 35% wt/wt water.

  12. A novel solubilization of phenanthrene using Winsor I microemulsion-based sodium castor oil sulfate.

    PubMed

    Zhao, Baowei; Zhu, Lizhong; Gao, Yanzheng

    2005-03-17

    Problems associated with polycyclic aromatic hydrocarbons (PAHs) contaminated site in environmental media have received increasing attention. Ex situ soil washing is commonly used for treating contaminated soils by separating the most contaminated fraction of the soil for disposal. Surfactant-enhanced soil washing is being considered with increasing frequency to actually achieve soil-contaminant separation. In this research, a novel solubilization of phenanthrene and extraction of phenanthrene from spiked soil by sodium castor oil sulfate (SCOS) microemulsion was presented and compared with the conventional surfactants, Triton X-100 (TX100), Tween 80 (TW80), Brij35, sodium dodecylbenzene sulfonate (SDBS) and sodium dodecyl sulfate (SDS). Unlike conventional surfactants, SCOS forms stable microemulsion in water and thus behaves much like a separate bulk phase in concentrating organic solutes. The extent of solubility enhancement is linearly proportional to the concentration of SCOS microemulsion, in contrast with the effect of a conventional surfactant in which a sharp inflection occurs in the vicinity of the measured critical micelle concentration. SCOS microemulsion exhibits the largest mass solubilization ratio among the selected surface active agents (SAAs) in both soil-free system and soil-water system. The partitioning coefficients of phenanthrene between the emulsified phase and the aqueous phase, Kem, is slightly larger than those between the micellar pseudo phase and the aqueous phase, Kmc. The extraction experiments demonstrate high and fast desorption of phenanthrene from spiked soil by SCOS microemulsion perhaps due to its high solubilization capacity compared with the conventional surfactant solutions. The results show that SCOS could be an attractive alternative to synthetic surfactants in ex situ washing for PAH-contaminated soils.

  13. Intranasal microemulsion of sildenafil citrate: in vitro evaluation and in vivo pharmacokinetic study in rabbits.

    PubMed

    Elshafeey, Ahmed H; Bendas, Ehab R; Mohamed, Osama H

    2009-01-01

    The purpose of the present study was to prepare intranasal delivery system of sildenafil citrate and estimate its relative bioavailability after nasal administration in rabbits to attain rapid onset of action with good efficacy at lower doses. Sildenafil citrate saturated solubility was determined in different solvents, cosolvents, and microemulsion systems. For nasal application, sildenafil citrate was formulated in two different systems: the first was a cosolvent system (S3) of benzyl alcohol/ethanol/water/Transcutol/taurodeoxy cholate/Tween 20 (0.5:16.8:47.7:15.9:1:18.1% w/w). The second was a microemulsion system (ME6) containing Oleic acid: Labrasol/Transcutol/water (8.33:33.3:16.66:41.66% w/w). The prepared systems were characterized in relation to their clarity, particle size, viscosity, pH, and nasal ciliotoxicity. In vivo pharmacokinetic performance of the selected system ME6 (with no nasal ciliotoxicity) was evaluated in a group of six rabbits in a randomized crossover study and compared to the marketed oral tablets. The targeted solubility (>20 mg/ml) of sildenafil citrate was achieved with cosolvent systems S1, S3, and S5 and with microemulsion systems ME3-ME6. The saturated solubility of sildenafil citrate in cosolvent system S3 and microemulsion system ME6 were 22.98 +/- 1.26 and 23.79 +/- 1.16 mg/ml, respectively. Microemulsion formulation ME6 showed shorter t (max) (0.75 h) and higher AUC((0-infinity)) (1,412.42 ng h/ml) compared to the oral tablets which showed t (max) equals 1.25 h and AUC((0-infinity)) of 1,251.14 ng h/ml after administration to rabbits at dose level of 5 mg/kg. The relative bioavailability was 112.89%. In conclusion, the nasal absorption of sildenafil citrate microemulsion was found to be fast, indicating the potential of nasal delivery instead of the conventional oral administration of such drug.

  14. Silver nanoparticles in hydrogels and microemulsions—a comparative account of their properties and bio-activity

    NASA Astrophysics Data System (ADS)

    Ray, Debajyoti; Chatterjee, Saptarshi; Sarkar, Keka; De, Swati

    2014-09-01

    Stable silver nanoparticles were prepared in sodium Aerosol OT (AOT) based microemulsions and hydrogels. The various gel and microemulsion compositions used for nanoparticle synthesis were obtained from the phase diagram of the AOT/n-heptane/H2O system. It was found that only in gels can AOT play a dual role of stabilizer as well as reducing agent. In microemulsions, AOT acts as a stabilizer only. In gels, the commonly used NaBH4 reduction results in spherical silver nanoparticles while the AOT based reduction yields highly facetted particles. In microemulsion however, larger particles of undefined shapes are formed in low yield while for the gels, a large number of particles are formed. The synthesized silver nanoparticles show strong antibacterial activity.

  15. Choline acetate enhanced the catalytic performance of Candida rogusa lipase in AOT reverse micelles.

    PubMed

    Xue, Luyan; Zhao, Yin; Yu, Lijie; Sun, Yanwen; Yan, Keqian; Li, Ying; Huang, Xirong; Qu, Yinbo

    2013-05-01

    Choline acetate is an ionic liquid composed of a kosmotropic anion and a chaotropic cation. According to Hofmeister series, a kosmotropic anion and/or a chaotropic cation could stabilize an enzyme, thereby facilitating the retention of the catalytic activity of the enzyme. In this work, we first report the influence of choline acetate on the activity and stability of lipase in AOT/water/isooctane reverse micelles. The indicator reaction is the lipase-catalyzed hydrolysis of 4-nitrophenyl butyrate. The results show that a low level of choline acetate does not affect the microstructure of the AOT reverse micelles, but the ionic liquid can improve the catalytic efficiency of lipase. Fluorescence spectra show that a high level of choline acetate has an impact on the conformation of lipase, so the activation is mainly due to the influence of choline acetate on the nucleophilicity of water. Infrared spectra demonstrate that choline acetate can form stronger hydrogen bonds with water surrounding lipase, and therefore enhance the nucleophilicity of the water, which makes it easier to attack the acyl enzyme intermediate, thereby increasing the activity of the lipase-catalyzed hydrolysis of the ester. A study on the stability of lipase in AOT reverse micelles indicates that the ionic liquid is able to maintain the activity of lipase to a certain extent. The effect of choline acetate is consistent with that predicted based on Hofmeister series.

  16. Molecular dynamics simulations of cytochrome c unfolding in AOT reverse micelles: The first steps.

    PubMed

    Abel, S; Waks, M; Marchi, M

    2010-08-01

    This paper explores the reduced form of horse cytochrome c confined in reverse micelles (RM) of sodium bis-(2-ethylhexyl) sulfosuccinate (AOT) in isooctane by molecular dynamics simulation. RMs of two sizes were constructed at a water content of W (o) = [ H₂O ]/[AOT] = 5.5 and 9.1. Our results show that the protein secondary structure and the heme conformation both depend on micellar hydration. At low hydration, the protein structure and the heme moiety remain stable, whereas at high water content the protein becomes unstable and starts to unfold. At W (o) = 9.1 , according to the X-ray structure, conformational changes are mainly localized on protein loops and around the heme moiety, where we observe a partial opening of the heme crevice. These findings suggest that within our time window (10ns), the structural changes observed at the heme level are the first steps of the protein denaturation process, previously described experimentally in micellar solutions. In addition, a specific binding of AOT molecules to a few lysine residues of the protein was found only in the small-sized RM.

  17. Preparation, characterization and relative bioavailability of oral elemene o/w microemulsion.

    PubMed

    Zeng, Zhaowu; Zhou, Guanglin; Wang, Xiaoli; Huang, Eric Zhijian; Zhan, Xiaori; Liu, Jun; Wang, Shuling; Wang, Anming; Li, Haifeng; Pei, Xiaolin; Xie, Tian

    2010-09-07

    The objective was to develop an elemene oil/water (o/w) microemulsion and evaluate its characteristics and oral relative bioavailability in rats. Elemene was used as the oil phase and drug, polysorbate 80 as a surfactant along with ethanol, propylene glycol, and glycerol as the cosurfactants. The microemulsion was prepared by mixing method, or ultrasonication method in an ultrasonic bath. Its three-dimensional response surface diagram was drawn by Mathcad software. The microemulsion was characterized by visual observation, cross-polarized microscopy, size, zeta potential, acidity, viscosity, and surface tension measurement. The drug content and entrapment efficiency were determined by ultra fast liquid chromatography (UFLC) and liquid surface method. Blood was drawn from rats at different time points after oral administration of an elemene microemulsion or a commercial elemene emulsion for measurement of the drug in plasma by UFLC to establish the pharmacokinetic parameters and relative bioavailability. The elemene microemulsion as a clarified and isotropic system containing 1% elemene (w/v), 5% ethanol (v/v), 15% propylene glycol (v/v), 15% glycerol (v/v), and 5% polysorbate 80 (w/v), was characterized as (57.7 ± 2.8) nm in size, 0.485 ± 0.032 in polydispersity index, (3.2 ± 0.4) mv in zeta potential, (5.19 ± 0.08) in pH, 6 mpa·s in viscosity, (31.8 ± 0.3) mN·m(-1) in surface tension, (8.273 ± 0.018) mg·mL(-1) in content of β-elemene, and (99.81 ± 0.24)% in average entrapment efficiency. The area under the concentration-time curves from 0 h to 24 h (AUC(0→24h)) of the elemene microemulsion and commercial elemene emulsion were integrated to be 3.092 mg·h·L(-1) and 1.896 mg·h·L(-1) respectively, yielding a relative bioavailability of 163.1%. The present study demonstrates the elemene microemulsion as a new formulation with ease of preparation, high entrapment efficiency, excellent clarity, good stability, and improved bioavailability.

  18. Biocatalytic synthesis of flavor ester "pentyl valerate" using Candida rugosa lipase immobilized in microemulsion based organogels: effect of parameters and reusability.

    PubMed

    Raghavendra, Tripti; Panchal, Nilam; Divecha, Jyoti; Shah, Amita; Madamwar, Datta

    2014-01-01

    Pentyl valerate was synthesized biocatalytically using Candida rugosa lipase (CRL) immobilized in microemulsion based organogels (MBGs). The optimum conditions were found to be pH 7.0, temperature of 37 °C, ratio of concentration of water to surfactant (Wo) of 60, and the surfactant sodium bis-2-(ethylhexyl)sulfosuccinate (AOT) for MBG preparation. Although kinetic studies revealed that the enzyme in free form had high affinity towards substrates (K(m) = 23.2 mM for pentanol and 76.92 mM for valeric acid) whereas, after immobilization, the K(m) values increased considerably (74.07 mM for pentanol and 83.3 mM for valeric acid) resulting in a slower reaction rate, the maximum conversion was much higher in case of immobilized enzyme (~99%) as compared to free enzyme (~19%). Simultaneous effects of important parameters were studied using response surface methodology (RSM) conjugated with Box-Behnken design (BBD) with five variables (process parameters), namely, enzyme concentration, initial water content (Wo), solvent used for MBG preparation, substrate ratio and time, and response as the final product formation, that is, pentyl valerate (%). The MBGs were reused for 10 consecutive cycles for ester synthesis. Efficacy of AOT/isooctane as dehydrating agent for extracting excess water from MBGs was found to exert a positive effect on the esterification reaction.

  19. Biocatalytic Synthesis of Flavor Ester “Pentyl Valerate” Using Candida rugosa Lipase Immobilized in Microemulsion Based Organogels: Effect of Parameters and Reusability

    PubMed Central

    Raghavendra, Tripti; Panchal, Nilam; Divecha, Jyoti; Shah, Amita; Madamwar, Datta

    2014-01-01

    Pentyl valerate was synthesized biocatalytically using Candida rugosa lipase (CRL) immobilized in microemulsion based organogels (MBGs). The optimum conditions were found to be pH 7.0, temperature of 37°C, ratio of concentration of water to surfactant (Wo) of 60, and the surfactant sodium bis-2-(ethylhexyl)sulfosuccinate (AOT) for MBG preparation. Although kinetic studies revealed that the enzyme in free form had high affinity towards substrates (Km = 23.2 mM for pentanol and 76.92 mM for valeric acid) whereas, after immobilization, the Km values increased considerably (74.07 mM for pentanol and 83.3 mM for valeric acid) resulting in a slower reaction rate, the maximum conversion was much higher in case of immobilized enzyme (~99%) as compared to free enzyme (~19%). Simultaneous effects of important parameters were studied using response surface methodology (RSM) conjugated with Box-Behnken design (BBD) with five variables (process parameters), namely, enzyme concentration, initial water content (Wo), solvent used for MBG preparation, substrate ratio and time, and response as the final product formation, that is, pentyl valerate (%). The MBGs were reused for 10 consecutive cycles for ester synthesis. Efficacy of AOT/isooctane as dehydrating agent for extracting excess water from MBGs was found to exert a positive effect on the esterification reaction. PMID:25093166

  20. Electron beam induced and microemulsion templated synthesis of CdSe quantum dots: tunable broadband emission and charge carrier recombination dynamics

    NASA Astrophysics Data System (ADS)

    Guleria, Apurav; Singh, Ajay K.; Rath, Madhab C.; Adhikari, Soumyakanti

    2015-04-01

    CdSe quantum dots (QDs) were synthesized by a rapid and one step templated approach inside the water pool of AOT (sodium bis(2-ethylhexyl) sulfosuccinate) based water-in-oil microemulsions (MEs) via electron beam (EB) irradiation technique with high dose rate, which favours high nucleation rate. The interplay of different experimental parameters such as precursor concentration, absorbed dose and {{W}0} values (aqueous phase to surfactant molar ratio) of MEs were found to have interesting consequences on the morphology, photoluminescence (PL), surface composition and carrier recombination dynamics of as-grown QDs. For instance, highly stable ultrasmall (∼1.7 nm) bluish-white light emitting QDs were obtained with quantum efficiency (η) of ∼9%. Furthermore, QDs were found to exhibit tunable broadband light emission extending from 450 to 750 nm (maximum FWHM ∼180 nm). This could be realized from the CIE (Commission Internationale d’Eclairage) chromaticity co-ordinates, which varied across the blue region to the orange region thereby, conferring their potential application in white light emitting diodes. Additionally, the average PL lifetime ≤ft( ≤ft< τ \\right> \\right) values could be varied from 18 ns to as high as 74 ns, which reflect the role of surface states in terms of their density and distribution. Another interesting revelation was the self-assembling of the initially formed QDs into nanorods with high aspect ratios ranging from 7 to 20, in correspondence with the {{W}0} values. Besides, the fundamental roles of the chemical nature of water pool and the interfacial fluidity of AOT MEs in influencing the photophysical properties of QDs were investigated by carrying out a similar study in CTAB (cetyltrimethylammonium bromide; cationic surfactant) based MEs. Surprisingly, very profound and contrasting results were observed wherein ≤ft< τ \\right> and η of the QDs in case of CTAB MEs were found to be at least three times lower as compared to

  1. Effect of microemulsions on transdermal delivery of citalopram: optimization studies using mixture design and response surface methodology.

    PubMed

    Huang, Chi-Te; Tsai, Ming-Jun; Lin, Yu-Hsuan; Fu, Yaw-Sya; Huang, Yaw-Bin; Tsai, Yi-Hung; Wu, Pao-Chu

    2013-01-01

    The aim of this study was to evaluate the potential of microemulsions as a drug vehicle for transdermal delivery of citalopram. A computerized statistical technique of response surface methodology with mixture design was used to investigate and optimize the influence of the formulation compositions including a mixture of Brij 30/Brij 35 surfactants (at a ratio of 4:1, 20%-30%), isopropyl alcohol (20%-30%), and distilled water (40%-50%) on the properties of the drug-loaded microemulsions, including permeation rate (flux) and lag time. When microemulsions were used as a vehicle, the drug permeation rate increased significantly and the lag time shortened significantly when compared with the aqueous control of 40% isopropyl alcohol solution containing 3% citalopram, demonstrating that microemulsions are a promising vehicle for transdermal application. With regard to the pharmacokinetic parameters of citalopram, the flux required for the transdermal delivery system was about 1280 μg per hour. The microemulsions loaded with citalopram 3% and 10% showed respective flux rates of 179.6 μg/cm(2) and 513.8 μg/cm(2) per hour, indicating that the study formulation could provide effective therapeutic concentrations over a practical application area. The animal study showed that the optimized formulation (F15) containing 3% citalopram with an application area of 3.46 cm(2) is able to reach a minimum effective therapeutic concentration with no erythematous reaction.

  2. Microemulsion-enhanced electrochemiluminescence of luminol-H2O2 for sensitive flow injection analysis of antioxidant compounds.

    PubMed

    Xiuhua, Wei; Chao, Liu; Yifeng, Tu

    2012-05-30

    A microemulsion enhanced electrochemiluminescence (ECL) of luminol-H(2)O(2) was studied with the flow-injection (FI) technique. The results revealed that the microemulsion composed with cetyltrimethylammonium bromide (CTAB), n-butanol, n-heptane and water greatly enhanced the ECL especially in acidic medium. The ECL emission increased for 20 to 2 times in this microemulsion medium over the pH range of 5.0-8.0 compared to that in aqueous solution. The mechanism of enhancement of surfactant and microemulsion for luminol-H(2)O(2) ECL was discussed. It is mainly based on the electrostatic interaction between luminol anion and the head group of surfactant, which causes the adsorption and promotes the dissociation of luminol on the surfaces of the microemulsion droplets, favors the oxidation of luminol by the yielded reactive oxygen species (ROSs) during electrolysis. This research is very significant for ECL applications because of the extended practicable pH range which was suitable for environmental and biological systems. As an example, this FI-ECL technique can be applied for determination of oligo proanthocyanidin (OPC) because of its antioxidant property and to evaluate the total antioxidant activity of the grape skin using OPC as an index. Copyright © 2012 Elsevier B.V. All rights reserved.

  3. Effect of microemulsions on transdermal delivery of citalopram: optimization studies using mixture design and response surface methodology

    PubMed Central

    Huang, Chi-Te; Tsai, Ming-Jun; Lin, Yu-Hsuan; Fu, Yaw-Sya; Huang, Yaw-Bin; Tsai, Yi-Hung; Wu, Pao-Chu

    2013-01-01

    The aim of this study was to evaluate the potential of microemulsions as a drug vehicle for transdermal delivery of citalopram. A computerized statistical technique of response surface methodology with mixture design was used to investigate and optimize the influence of the formulation compositions including a mixture of Brij 30/Brij 35 surfactants (at a ratio of 4:1, 20%–30%), isopropyl alcohol (20%–30%), and distilled water (40%–50%) on the properties of the drug-loaded microemulsions, including permeation rate (flux) and lag time. When microemulsions were used as a vehicle, the drug permeation rate increased significantly and the lag time shortened significantly when compared with the aqueous control of 40% isopropyl alcohol solution containing 3% citalopram, demonstrating that microemulsions are a promising vehicle for transdermal application. With regard to the pharmacokinetic parameters of citalopram, the flux required for the transdermal delivery system was about 1280 μg per hour. The microemulsions loaded with citalopram 3% and 10% showed respective flux rates of 179.6 μg/cm2 and 513.8 μg/cm2 per hour, indicating that the study formulation could provide effective therapeutic concentrations over a practical application area. The animal study showed that the optimized formulation (F15) containing 3% citalopram with an application area of 3.46 cm2 is able to reach a minimum effective therapeutic concentration with no erythematous reaction. PMID:23919086

  4. Design and Development of Repaglinide Microemulsion Gel for Transdermal Delivery.

    PubMed

    Shinde, Ujwala A; Modani, Sheela H; Singh, Kavita H

    2017-07-17

    Microemulsion formulation of repaglinide, a BCS class II hypoglycemic agent with limited oral bioavailability, was developed considering its solubility in various oils, surfactants, and cosurfactants. The pseudo-ternary phase diagrams for microemulsion regions were constructed by water titration method at K m 1:1 and characterized for optical birefringence, percentage transmittance, pH, refractive index, globule size, zeta potential, viscosity, drug content, and thermodynamic stability. To enhance the drug permeation and residence time, the optimized microemulsions having mean globule size of 36.15 ± 9.89 nm was gelled with xanthan gum. The developed microemulsion-based gel was characterized for globule size, zeta potential, pH, and drug content. All evaluation parameters upon gelling were found to be satisfactory. Ex vivo permeability study across rat skin demonstrated higher steady-state flux (P < 0.05) for microemulsion of repaglinide in comparison to the repaglinide microemulsion gel. At the end of 24 h, the cumulative drug permeation from microemulsion and microemulsion gel was found to be 229.19 ± 24.34 and 180.84 ± 17.40 μg/cm(2), respectively. The microemulsion formulation showed 12.30-fold increase in flux as compared to drug suspension with highest enhancement ratio (E r ) of 12.36. Whereas microemulsion gel exhibited 10.97-fold increase in flux (with highest E r , 11.78) as compared to repaglinide (RPG) suspension. In vivo efficacy study was performed in normal Sprague-Dawley rats by using oral glucose tolerance test. Results of RPG transdermal microemulsion gel demonstrated remarkable advantage over orally administered RPG by reducing the glucose level in controlled manner. Hence, it could be a new, alternative dosage form for effective therapy of type 2 diabetes mellitus.

  5. Microemulsion formulation of clonixic acid: solubility enhancement and pain reduction.

    PubMed

    Lee, Jung-Mi; Park, Kyung-Mi; Lim, Soo-Jeong; Lee, Mi-Kyung; Kim, Chong-Kook

    2002-01-01

    Clonixic acid is currently marketed as a salt form because of its poor water-solubility. However, the commercial dosage form causes severe pain after intramuscular or intravenous injection. To improve the solubility of clonixic acid and to reduce pain on injection, clonixic acid was incorporated into oil-in-water microemulsions prepared from pre-microemulsion concentrate composed of varying ratios of oil and surfactant mixture. As an oil phase for drug incorporation, up to 14% castor oil could be included in the pre-microemulsion concentrate without a significant increase in droplet size. Both drug contents and droplet size increased as the weight ratio of Tween 20 to Tween 85 decreased. Taken together, when microemulsions were prepared from pre-microemulsion concentrate composed of 5:12:18 weight ratio of castor oil:Tween 20:Tween 85, clonixic acid could be incorporated at 3.2 mg mL(-1) in the microemulsion with a droplet size of less than 120 nm. The osmotic pressure of this microemulsion was remarkably lower than the commercial formulation, irrespective of the dilution ratios. The rat paw-lick test was used to compare pain responses among formulations. The microemulsion formulation significantly reduced the number of rats licking their paws as well as the total licking time, suggesting less pain induction by the microemulsion formulation. The pharmacokinetic parameters of clonixic acid after intravenous administration of the clonixic acid microemulsion to rats were not significantly different from those of the commercial formulation, lysine clonixinate. The present study suggests that microemulsion is an alternative formulation for clonixic acid with improved characteristics.

  6. Probing the microstructure of nonionic microemulsions with ethyl oleate by viscosity, ROESY, DLS, SANS, and cyclic voltammetry.

    PubMed

    Kaur, Gurpreet; Chiappisi, Leonardo; Prévost, Sylvain; Schweins, Ralf; Gradzielski, Michael; Mehta, Surinder K

    2012-07-24

    electrochemistry. NMR-ROESY experiments give information regarding the internal organization of the microemulsion droplets. In general, one finds a continuous structural transition from a W/O over a bicontinuous to an O/W microemulsion, however with a peculiar network formation over an extended concentration range, which is attributed to the somewhat amphiphilic oil ethyl oleate. The detailed knowledge of the structural behavior of this type of system might be important for their future applications.

  7. Oil-in-water microemulsions based on cationic surfactants with a hydroxyalkyl fragment in the head group

    NASA Astrophysics Data System (ADS)

    Mirgorodskaya, Alla B.; Yackevich, Ekaterina I.; Zakharova, Lucia Ya.; Konovalov, Alexander I.

    2013-04-01

    The stable oil-in-water microemulsions with a high water content were formed on the basis of cationic surfactants, including those that contain a hydroxyalkyl fragment in the head group. These systems can bind the water- and oil-soluble reagents into a single aggregate formed by self-assembling components. The size, surface and electrokinetic potentials of aggregates in the surfactant/n-hexane/n-butanol/water microemulsions were determined. Besides, their catalytic effect on the cleavage of carboxylic acid esters was evaluated. The behavior of the system was shown to be determined not only by hydrophobic and electrostatic interactions but also by specific interactions, i.e., hydrogen bonds.

  8. Electric field induced percolation in microemulsions: simulation of the electric conductivity

    NASA Astrophysics Data System (ADS)

    Ilgenfritz, G.; Runge, F.

    1992-02-01

    Structure changes can be induced by high electric fields in microemulsions which bring the system from a nonconducting state to a highly conducting state. We report conductivity and electric birefringence measurements in a microemulsion, stabilized by the nonionic surfactant Igepal CO-520 (10 wt% 0.01 M KCl/40% n-hexane, 40% c-hexane/ 10% Igepal). Based on the experimental findings we investigate two models which may be relevant for understanding the field induced percolation behavior. Computer simulations of the electric conductivity, using the random walk approach, are performed with the following heterogeneous systems: (a) statistically distributed conducting Ising chains in a nonconducting matrix, (b) nonconducting overlapping spheres in a conducting medium. Both systems are capable of modelling certain aspects of the observed percolation. The continuum percolation with overlapping spheres puts special emphasis on the Bruggeman equation of the conductivity in dispersed systems, which is found to be valid in a much wider range than might have been thought before.

  9. [Preparation of solid lipid nanoparticles by microemulsion technique].

    PubMed

    Mao, Shi-rui; Wang, Yan-zhi; Ji, Hong-yu; Bi, Dian-zhou

    2003-08-01

    To prepare solid lipid nanoparticles by microemulsion technique. Stearic acid was used as the oil phase, lecithin as surfactant, alcohol as cosurfactant and distilled water as the aqueous phase. Microemulsion was prepared by mixing the above component in proper ratio. The corresponding pseudoternary phase diagram monitored Microemulsion formation field of different lecithin/alcohol. Solid lipid nanoparticles (SLN) were prepared by dispersing warm microemulsion in cold water under magnetic stirring. Then appropriate microemulsions that can contain more water phase and suitable oil phase were selected to prepare SLN. The influence of formulation, process variables on the preparation and quality of SLN were studied. Based on the investigation of single factors, orthogonal design was used to optimize SLN formulation and preparation process, and more, the reproducibility of the optimized results were studied. The results showed that the device temperature (Ti), water temperature (Tw), and delivery rate (Rd) were the key factors that influence the preparation process of SLN, and Tw was extremely important. The ratio of microemulsion formulation, the ratio of microemulsion and distilled water had also influence on its quality. Microemulsion technique can be used to prepare solid lipid nanoparticles.

  10. Ammonia-in-oil-microemulsions and their application.

    PubMed

    Gyger, Fabian; Bockstaller, Pascal; Gerthsen, Dagmar; Feldmann, Claus

    2013-11-18

    Liquid ammonia on the nanoscale: Ammonia-in-oil microemulsions are used to synthesize Bi, Re, CoN, and GaN nanoparticles, which can be obtained without further thermal treatment. These microemulsions are as reproducible and simple as their water-in-oil conterparts, with the exception of the required low temperature of -40 °C.

  11. Controlled-release injectable microemulsions: recent advances and potential opportunities.

    PubMed

    Dubey, Rajesh

    2014-02-01

    Controlled-release injectable (CRI) formulations hold significant value for several indications. However, there have been very few successful developments and approvals due to various challenges that include limited polymer options, drug-excipient process incompatibility and complex scale-up/validation processes. Microemulsion technology, as reviewed in this article, promises to resolve many of these challenges. In addition to its development and manufacturing advantages, feasibility to engineer microemulsion formulations by choosing its constituents and nature of formulation vis-à-vis drug candidate demonstrates capability of microemulsion to modulate in-vivo drug release and thereby optimize drug pharmacokinetics and pharmacodynamics. This potential of microemulsion has been used in a few studies to prolong in vivo drug residence time resulting in a more favorable benefit/risk profile for various drugs. Virtues of injectable microemulsion, results related to prolonged-release injectable microemulsion, impact on drug safety and efficacy and possible opportunities have been discussed. A detailed review of research work on microemulsions as well as other parenteral controlled-release formulations was conducted using PubMed, Science Direct and Google Scholar. The fact that microemulsion formulations administered through subcutaneous or intramuscular route would undergo significantly prolonged elimination should be leveraged to develop novel CRI drug products. Such products will find enormous application for several drug candidates which have poor oral pharmacokinetics resulting into poor treatment outcome.

  12. Microemulsions: Options To Expand the Synthesis of Inorganic Nanoparticles.

    PubMed

    Wolf, Silke; Feldmann, Claus

    2016-12-19

    Microemulsions (MEs) are ideal for obtaining high-quality inorganic nanoparticles. As thermodynamically stable systems with a nanometer-sized droplet phase that serves as a nanoreactor, MEs have obvious advantages for the synthesis of nanoparticles. MEs also have disadvantages, such as their complexity as multicomponent systems, the low amount of obtainable nanoparticles, their limited thermal stability, the fact that hydrolyzable or oxidizable compounds are often excluded from synthesis, the partly elaborate separation of nanoparticles, as well as the removal of surface-adhered surfactants subsequent to synthesis. This Review presents some strategies to further expand the options of ME-based synthesis of inorganic nanoparticles. This comprises the crystallization of nanoparticles in "high-temperature MEs", the synthesis of hollow nanospheres, the use of hydrogen peroxide or liquid ammonia as the polar droplet phase, and the synthesis of base metals and nitrides in MEs. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. Temperature dependence of the surfactant film bending elasticity in a bicontinuous sugar surfactant based microemulsion: a quasielastic scattering study.

    PubMed

    Wellert, Stefan; Karg, Matthias; Holderer, Olaf; Richardt, André; Hellweg, Thomas

    2011-02-28

    Currently, the design of microemulsions is focussed on the formulation of environmentally compatible systems formed by non-harmful amphiphiles and oils. The use of sugar-based surfactants allows the design of microemulsions where, instead of the temperature, the addition of short- or medium-chain alcohols tunes the curvature of the amphiphilic interface. In this work, the resulting temperature stability of a sugar surfactant and rapeseed methyl ester based bicontinuous microemulsion is exploited to study the influence of temperature variations on the bending elastic constant κ. Quasi-elastic scattering of light and neutrons is used to separate long-range collective motions and local thermally excited undulations of the interface. κ in units of kT is found to be independent of temperature over a wide range.

  14. Enhancement of transdermal delivery of ibuprofen using microemulsion vehicle.

    PubMed

    Hu, Liandong; Hu, Qiaofeng; Yang, Jianxue

    2014-10-01

    The objective of this study was to find a stable microemulsion vehicle for transdermal delivery of ibuprofen to improve the skin permeability. Microemulsion was prepared using different sorts of oils, surfactants and co-surfactants. Pseudo-ternary phase diagrams were used to evaluate the microemulsion domain. The effects of oleic acid and surfactant mixture on skin permeation of ibuprofen were evaluated with excised skins. The optimum formulation F3 consisting of 6% oleic acid, 30% Cremophor RH40/Transcutol P (2:1, w/w) and 59% water phase, showed a high permeation rate of 42.98 µg/cm(2)/hr. The mean droplet size of microemulsion was about 43 nm and no skin irritation signs were observed on the skin of rabbits. These results indicated that this novel microemulsion is a useful formulation for the transdermal delivery of ibuprofen.

  15. Enhancement of transdermal delivery of ibuprofen using microemulsion vehicle

    PubMed Central

    Hu, Liandong; Hu, Qiaofeng; Yang, Jianxue

    2014-01-01

    Objective(s): The objective of this study was to find a stable microemulsion vehicle for transdermal delivery of ibuprofen to improve the skin permeability. Materials and Methods: Microemulsion was prepared using different sorts of oils, surfactants and co-surfactants. Pseudo-ternary phase diagrams were used to evaluate the microemulsion domain. The effects of oleic acid and surfactant mixture on skin permeation of ibuprofen were evaluated with excised skins. Results: The optimum formulation F3 consisting of 6% oleic acid, 30% Cremophor RH40/Transcutol P (2:1, w/w) and 59% water phase, showed a high permeation rate of 42.98 µg/cm2/hr. The mean droplet size of microemulsion was about 43 nm and no skin irritation signs were observed on the skin of rabbits. Conclusion: These results indicated that this novel microemulsion is a useful formulation for the transdermal delivery of ibuprofen. PMID:25729544

  16. Coexistence, Interfacial Energy, and the Fate of Microemulsions of 2D Dipolar Bosons

    NASA Astrophysics Data System (ADS)

    Moroni, Saverio; Boninsegni, Massimo

    2014-12-01

    The superfluid-crystal quantum phase transition of a system of purely repulsive dipolar bosons in two dimensions is studied by quantum Monte Carlo simulations at zero temperature. We determine freezing and melting densities and estimate the energy per unit length of a macroscopic interface separating the two phases. The results rule out the microemulsion scenario for any physical realization of this system, given the exceedingly large predicted size of the bubbles.

  17. Study the effect of HLB of surfactant on particle size distribution of hematite nanoparticles prepared via the reverse microemulsion

    NASA Astrophysics Data System (ADS)

    Housaindokht, Mohammad Reza; Nakhaei Pour, Ali

    2012-05-01

    Hematite nanoparticles have been synthesized via reverse microemulsion route at room temperature. The microemulsion system, contained water, chloroform, 1-butanol, and surfactant, was combined with iron nitrate solution to result iron oxide nanoparticles precipitation. Three technical surfactants, with different structures and HLB (hydrophile-lipophile balance) values were employed and the effects of the HLB values on the hematite particle size were investigated. The prepared particles were evaluated by BET, XRD and TEM techniques. These results showed that the iron oxide particle size and particle size distribution increased with increasing surfactant HLB values.

  18. Preparation and Anesthetic Properties of Propofol Microemulsions in Rat

    PubMed Central

    Morey, Timothy E.; Modell, Jerome H.; Shekhawat, Dushyant; Grand, Todd; Shah, Dinesh O.; Gravenstein, Nikolaus; McGorray, Susan P.; Dennis, Donn M.

    2010-01-01

    Introduction Propofol's lipophilicity has required dispersion in a soybean macroemulsion. We hypothesized that the anesthetic properties of propofol are preserved when reformulated as a transparent microemulsion rather than as a turbid macroemulsion and that the dose-response relationship can be selectively modified by altering the microemulsion's surfactant type and concentration. Methods Microemulsions of propofol were formulated using purified poloxamer 188 (3%, 5%, 7%), and sodium salt of fatty acids (C8, C10, C12) in saline and characterized using ternary/binary diagrams, particle sizing, and stability upon dilution. Rats received propofol (10 mg/kg/min) as either a microemulsion or conventional macroemulsion to determine these endpoints: induction (dose; stunned; loss of lash reflex, righting reflex, withdrawal to toe pinch) and recovery (recovery of lash, righting, withdrawal reflexes). After a 14 day recovery period, rats were crossed over into the opposite experimental limb. Results Forty-eight microemulsions (diameter: 11.9-47.7 nm) were formulated. Longer carbon chain length led to a marked increase in the volume of diluent necessary to break these microemulsions. All rats experienced anesthetic induction with successful recovery although significantly greater doses of propofol were required to induce anesthesia with microemulsions irrespective of surfactant concentration or type than with macroemulsions. The sodium salt of C10 fatty acid microemulsion required the greatest dose and longest time for anesthetic induction. Conclusion Propofol microemulsions cause induction in rat similar to that from macroemulsions. The surfactant concentration and type markedly affects the spontaneous destabilization and anesthetic properties of microemulsions, a phenomenon suggesting a mechanism whereby dose-response relationship can be selectively modified. PMID:16732089

  19. Development, Characterization, and In Vitro Evaluation of Tamoxifen Microemulsions

    PubMed Central

    Monteagudo, E.; Gándola, Y.; González, L.; Bregni, C.; Carlucci, A. M.

    2012-01-01

    Microemulsions (MEs) were designed by an innovative rational development, characterized, and used to load up to 20 mM of Tamoxifen citrate (TMX). They were made with acceptable and well-characterized excipients for all the routes of administration. Some of their properties, such as nanometric mean size and long stability shelf life, make them interesting drug delivery systems. The results obtained after the in vitro inhibition of estradiol-induced proliferation in MCF-7 breast cancer cells demonstrated a significant effect in cell growth. A decreasing of at least 90% in viable cells was shown after the incubation with MEs containing 20 mM of TMX. Besides, two compositions which loaded 10 mM of drug showed a cytotoxic effect higher than 70%. These results encourage the evaluation of alternative protocols for this drug administration, not only for estrogen receptor (ER) positive tumors, but also for ER negative. PMID:22272375

  20. Shear flow behavior of a dynamically symmetric polymeric bicontinuous microemulsion

    NASA Astrophysics Data System (ADS)

    Zhou, Ning

    2005-03-01

    Soft materials with complex internal structure often exhibit fascinating rheological behavior. For example, under flow the poly (ethylethylene) (PEE)/poly(dimethyl siloxane) (PDMS)/PEE-PDMS polymeric bicontinuous microemulsion (BμE) showed shear-induced macrophase separation.^ 1 This was tentatively attributed to the extreme dynamical asymmetry of the two homopolymers, i.e., their viscosities differed by three orders of magnitude. To understand the role of the dynamic symmetry of a BμE when subjected to shear flow, we have developed a new ternary polymer blend system poly(butylene oxide) (PBO)/ poly(ethylenepropylene) (PEP)/PEP-PBO, which is dynamically almost symmetric. We will report on the shear flow behavior of this new BμE. Reference: [1] Krishnan et al. Phys. Rev. Lett. 2001, 87, 098301

  1. In vitro suppression of oral squamous cell carcinoma growth by ultrasound-mediated delivery of curcumin microemulsions.

    PubMed

    Lin, Hung-Yin; Thomas, James L; Chen, Huan-Wen; Shen, Chih-Min; Yang, Wen-Jen; Lee, Mei-Hwa

    2012-01-01

    There is increasing interest in using natural products as anticancer agents, as many have antioxidative properties that may help to prevent cellular damage that can lead to cancer. In addition, there is the expectation that many natural products will have low toxicity and few side effects. However, most anticancer and antioxidative agents are hydrophobic, reducing their bioavailability in vivo and making them problematic to deliver. Curcumin provides a good model system for study. In low doses it shows both anticancer and antioxidation effects, whereas in high doses and delivered locally it could be cytotoxic for cancer cells. In this paper, curcumin microemulsions were formed with food-grade chemicals, including soybean lecithin, soybean oil, and Tween 80, a Food and Drug Administration-approved surfactant. The optimized composition formed curcumin microemulsions with a mean size of 40-50 nm, carrying a concentration of curcumin as high as 15 μM. The stability of curcumin microemulsions refrigerated at 5°C over at least 968 days was assessed by size distribution and zeta potential. The effects of low-frequency ultrasound on two oral squamous cell carcinoma cell lines (OSCC-4 and OSCC-25), and the synergy between treatment with curcumin microemulsions and low-frequency sonic stimulation, were tested. Finally, microscopic imaging of the cells confirmed the toxic effects of the curcumin microemulsions, showing damaged and ruptured cells after treatment. Brief exposure to the curcumin-containing microemulsions did have cytotoxic effects, but the addition of ultrasound strongly enhanced those effects, especially on OSCC-25 cells.

  2. In vitro suppression of oral squamous cell carcinoma growth by ultrasound-mediated delivery of curcumin microemulsions

    PubMed Central

    Lin, Hung-Yin; Thomas, James L; Chen, Huan-Wen; Shen, Chih-Min; Yang, Wen-Jen; Lee, Mei-Hwa

    2012-01-01

    There is increasing interest in using natural products as anticancer agents, as many have antioxidative properties that may help to prevent cellular damage that can lead to cancer. In addition, there is the expectation that many natural products will have low toxicity and few side effects. However, most anticancer and antioxidative agents are hydrophobic, reducing their bioavailability in vivo and making them problematic to deliver. Curcumin provides a good model system for study. In low doses it shows both anticancer and antioxidation effects, whereas in high doses and delivered locally it could be cytotoxic for cancer cells. In this paper, curcumin microemulsions were formed with food-grade chemicals, including soybean lecithin, soybean oil, and Tween 80, a Food and Drug Administration-approved surfactant. The optimized composition formed curcumin microemulsions with a mean size of 40–50 nm, carrying a concentration of curcumin as high as 15 μM. The stability of curcumin microemulsions refrigerated at 5°C over at least 968 days was assessed by size distribution and zeta potential. The effects of low-frequency ultrasound on two oral squamous cell carcinoma cell lines (OSCC-4 and OSCC-25), and the synergy between treatment with curcumin microemulsions and low-frequency sonic stimulation, were tested. Finally, microscopic imaging of the cells confirmed the toxic effects of the curcumin microemulsions, showing damaged and ruptured cells after treatment. Brief exposure to the curcumin-containing microemulsions did have cytotoxic effects, but the addition of ultrasound strongly enhanced those effects, especially on OSCC-25 cells. PMID:22393291

  3. Coexistence, Interfacial Energy and the Fate of Microemulsions of 2D Dipolar Bosons

    NASA Astrophysics Data System (ADS)

    Boninsegni, Massimo

    The superfluid-crystal quantum phase transition of a system of purely repulsive dipolar bosons in two dimensions has been the subject of a lot of theoretical study, mainly because of some intriguing predictions by Spivak and Kivelson (2004) regarding an exotic, intermediate ''microemulsion'' that should appear at low temperature between the crystal and the superfluid. We investigated this scenario by means of Quantum Monte Carlo simulations at zero temperature, determined freezing and melting densities, and estimated the energy per unit length of a macroscopic interface separating the coexisting crystal and superfluid phases. The results rule out quantitatively the microemulsion scenario for any physical realization of this system, given the exceedingly large predicted size of the bubbles. Reference: S. Moroni and M. Boninsegni, Phys. Rev. Lett. 113, 240407 (2014)

  4. Cryogenic transmission electron microscopy study: preparation of vesicular dispersions by quenching microemulsions.

    PubMed

    Lee, H S; Morrison, E D; Zhang, Q; McCormick, A V

    2016-09-01

    We previously showed that long-lived nanoemulsions, seeming initially vesicular, might be prepared simply by diluting and cooling (quenching) warm microemulsions with n-hexadecane with precooled water. In this paper, we confirm that these systems are vesicular dispersions when fresh, and they can be made with similar structures and compositional dependence using alkanes with chain lengths ranging from octane to hexadecane. The nanostructures of fresh nanoemulsions are imaged with cryogenic transmission electron microscopy (cryo-TEM). We confirm that water-continuous microemulsions give simple dispersions of vesicles (sometimes unilamellar), typically less than 100 nm in diameter; these systems can avoid separation for over 2 months. Selected samples were also prepared using halogenated alkanes to create additional contrast in the cryo-TEM, allowing us to confirm that the oil is located in the observed vesicular structures. © 2016 The Authors Journal of Microscopy © 2016 Royal Microscopical Society.

  5. A synthesis of AOT40-based response functions and critical levels of ozone for agricultural and horticultural crops

    NASA Astrophysics Data System (ADS)

    Mills, G.; Buse, A.; Gimeno, B.; Bermejo, V.; Holland, M.; Emberson, L.; Pleijel, H.

    Crop-response data from over 700 published papers and conference proceedings have been analysed with the aim of establishing ozone dose-response functions for a wide range of European agricultural and horticultural crops. Data that met rigorous selection criteria (e.g. field-based, ozone concentrations within European range, full season exposure period) were used to derive AOT40-yield response functions for 19 crops by first converting the published ozone concentration data into AOT40 (AOT40 is the hourly mean ozone concentration accumulated over a threshold ozone concentration of 40 ppb during daylight hours, units ppm h). For any individual crop, there were no significant differences in the linear response functions derived for experiments conducted in the USA or Europe, or for individual cultivars. Three statistically independent groups were identified: ozone sensitive crops (wheat, water melon, pulses, cotton, turnip, tomato, onion, soybean and lettuce); moderately sensitive crops (sugar beet, potato, oilseed rape, tobacco, rice, maize, grape and broccoli) and ozone resistant (barley and fruit represented by plum and strawberry). Critical levels of a 3 month AOT40 of 3 ppm h and a 3.5 month AOT40 of 6 ppm h were derived from the functions for wheat and tomato, respectively.

  6. Microemulsions from vegetable oil and aqueous alcohol with trialkylamine surfactant as alternative fuel for diesel engines

    SciTech Connect

    Schwab, A.W.; Pryde, E.H.

    1984-05-29

    Hybrid fuel microemulsions are prepared from vegetable oil, a C/sub 1/-C/sub 3/ alcohol, water, and a surfactant comprising a lower trialkylamine. For enhanced water tolerance by the fuel, the amine is reacted with a longchain fatty acid for conversion to the corresponding trialkylammonium soap. Optionally, 1-butanol is incorporated into the system as a cosurfactant for the purpose of lowering both the viscosity and the solidification temperature.

  7. Microemulsion characterization by the use of a noninvasive backscatter fiber optic probe

    NASA Technical Reports Server (NTRS)

    Ansari, Rafat R.; Dhadwal, Harbans S.; Cheung, H. M.; Meyer, William V.

    1993-01-01

    This paper demonstrates the utility of a noninvasive backscatter fiber optic probe for dynamic light-scattering characterization of a microemulsion comprising sodium dodecyl sulfate/1-butanol/ brine/heptane. The fiber probe, comprising two optical fibers precisely positioned in a stainless steel body, is a miniaturized and efficient self-beating dynamic light-scattering system. Accuracy of particle size estimation is better than +/- 2 percent.

  8. Simple microscopic model of a microemulsion

    NASA Astrophysics Data System (ADS)

    Schick, M.; Shih, Wei-Heng

    1987-09-01

    A simple model of a three-component mixture, representing oil, water, and surfactant, displays many of the properties of microemulsions. Proximity to critical phenomena is responsible for the occurrence of low and ultralow surface tensions and of short-range structure. The increase of the amphiphilic nature of the surfactant, known to reduce the amount of it needed to solubilize oil and water, also alters the wetting behavior and introduces liquid-crystal phases at lower temperatures. It has no strong effect on the surface tensions.

  9. Effect of combined use of nonionic surfactant on formation of oil-in-water microemulsions.

    PubMed

    Li, Ping; Ghosh, Anasuya; Wagner, Robert F; Krill, Steve; Joshi, Yatindra M; Serajuddin, Abu T M

    2005-01-06

    self-emulsifying microemulsions drug delivery system (SMEDDS).

  10. Development and evaluation of microemulsions for transdermal delivery of insulin.

    PubMed

    Malakar, Jadupati; Sen, Suma Oomen; Nayak, Amit Kumar; Sen, Kalyan Kumar

    2011-01-01

    Insulin-loaded microemulsions for transdermal delivery were developed using isopropyl myristate or oleic acid as the oil phase, Tween 80 as the surfactant, and isopropyl alcohol as the cosurfactant. The pseudoternary phase diagrams were constructed to determine the composition of microemulsions. The insulin permeation flux of microemulsions containing oleic acid as oil phase through excised mouse skin and goat skin was comparatively greater than that of microemulsions containing isopropyl myristate as oil phase. The insulin-loaded microemulsion containing 10% oleic acid, 38% aqueous phase, and 50% surfactant phase with 2% dimethyl sulfoxide (DMSO) as permeation enhancer showed maximum permeation flux (4.93 ± 0.12 μg/cm(2)/hour) through goat skin. The in vitro insulin permeation from these microemulsions was found to follow the Korsmeyer-Peppas model (R(2) = 0.923 to 0.973) over a period of 24 hours with non-Fickian, "anomalous" mechanism. Together these preliminary data indicate the promise of microemulsions for transdermal delivery of insulin.

  11. Development and Evaluation of Microemulsions for Transdermal Delivery of Insulin

    PubMed Central

    Malakar, Jadupati; Sen, Suma Oomen; Nayak, Amit Kumar; Sen, Kalyan Kumar

    2011-01-01

    Insulin-loaded microemulsions for transdermal delivery were developed using isopropyl myristate or oleic acid as the oil phase, Tween 80 as the surfactant, and isopropyl alcohol as the cosurfactant. The pseudoternary phase diagrams were constructed to determine the composition of microemulsions. The insulin permeation flux of microemulsions containing oleic acid as oil phase through excised mouse skin and goat skin was comparatively greater than that of microemulsions containing isopropyl myristate as oil phase. The insulin-loaded microemulsion containing 10% oleic acid, 38% aqueous phase, and 50% surfactant phase with 2% dimethyl sulfoxide (DMSO) as permeation enhancer showed maximum permeation flux (4.93 ± 0.12 μg/cm2/hour) through goat skin. The in vitro insulin permeation from these microemulsions was found to follow the Korsmeyer-Peppas model (R2 = 0.923 to 0.973) over a period of 24 hours with non-Fickian, “anomalous” mechanism. Together these preliminary data indicate the promise of microemulsions for transdermal delivery of insulin. PMID:22389858

  12. Antifungal activity of topical microemulsion containing a thiophene derivative.

    PubMed

    Guimarães, Geovani Pereira; de Freitas Araújo Reis, Mysrayn Yargo; da Silva, Dayanne Tomaz Casimiro; Junior, Francisco Jaime Bezerra Mendonça; Converti, Attílio; Pessoa, Adalberto; de Lima Damasceno, Bolívar Ponciano Goulart; da Silva, José Alexsandro

    2014-01-01

    Fungal infections have become a major problem of worldwide concern. Yeasts belonging to the Candida genus and the pathogenic fungus Cryptococcus neoformans are responsible for different clinical manifestations, especially in immunocompromised patients. Antifungal therapies are currently based on a few chemotherapeutic agents that have problems related to effectiveness and resistance profiles. Microemulsions are isotropic, thermodynamically stable transparent systems of oil, water and surfactant that can improve the solubilization of lipophilic drugs. Taking into account the need for more effective and less toxic drugs along with the potential of thiophene derivatives as inhibitors of pathogenic fungi growth, this study aimed to evaluate the antifungal activity of a thiophene derivative (5CN05) embedded in a microemulsion (ME). The minimum inhibitory concentration (MIC) was determined using the microdilution method using amphotericin B as a control. The formulations tested (ME- blank and ME-5CN05) showed physico-chemical properties that would allow their use by the topical route. 5CN05 as such exhibited moderate or weak antifungal activity against Candida species (MIC = 270-540 μg . mL(-1)) and good activity against C. neoformans (MIC = 17 μg . mL(-1)). Candida species were susceptible to ME-5CN05 (70-140 μg . mL(-1)), but C. neoformans was much more, presenting a MIC value of 2.2 μg . mL(-1). The results of this work proved promising for the pharmaceutical industry, because they suggest an alternative therapy against C. neoformans.

  13. Behavior of PPI-G2 Dendrimer in a Microemulsion.

    PubMed

    Rokach, Shifra; Ottaviani, Maria Francesca; Shames, Alexander I; Aserin, Abraham; Garti, Nissim

    2017-03-16

    Dendrimer nanostructures are of eminent interest in biomedical applications because of their uniform and well-defined molecular size and shape, and their ability to cross cell membranes and reduce the risk of premature clearance from the human body. Dendrimers perform as gene and drug carriers and have also shown significant therapeutic properties for treating cancer and neurodegenerative diseases. A complex drug delivery system, based on a dendrimer solubilized in the aqueous core of a water-in-oil (W/O) microemulsion (ME) along with the drug may combine the advantages of both dendrimers and MEs to provide better control of drug release. We propose a new microemulsion composed of drug-permitted surfactants and dendrimer that can be used as a potential controlled drug delivery nanosystem. The influence of second generation poly(propyleneimine) (PPI-G2) dendrimer; solubilized in (W/O) ME with a capacity of up to 25 wt% PPI-G2 at various pHs; and their interactions with the surfactant phosphatidylcholine (PC), cosurfactant (butanol), and water was studied. SAXS and EPR measurements indicated that increasing PPI-G2 concentration reduces droplet curvature and increases droplet size thus increasing macro-(SAXS) and micro-(EPR) order degree. Furthermore, SD-NMR and ATR-FTIR show stronger interactions between PPI-G2 and water molecules at the expense of PC and butanol headgroups hydration, which increases microviscosity (EPR). PPI-G2's effect is somewhat opposite to the increasing water phase effect, thus reducing the amount of free water (DSC) and slowing the mobility of all ME components (SD-NMR).

  14. Effects of microemulsions on the stratum corneum and hydrocortisone penetration.

    PubMed

    Lehmann, L; Keipert, S; Gloor, M

    2001-09-01

    We tested a high-water-content hydrophilic microemulsion (ME 1) and a low-water-content lipophilic microemulsion (ME 2) for their suitability for use in dermatology, in general, and as alternative hydrocortisone (HC) vehicles, in particular. The lipophilic component of both study products was isopropyl myristate. The surfactant/cosurfactant system of ME 1 consisted of two sucrose esters and that of ME 2 was a mixture of Tagat S and Plurololeat. Both MEs showed no in vitro irritability in the hen's egg test on chorioallantoic membranes. In 14 subjects, stratum corneum water content was determined by corneometry and transepidermal water loss (TEWL) by the Tewameter before and after 3 days use of ME 1 or ME 2 as well as on two untreated control sites. ME 1 produced dehydration and increased TEWL as evidence of barrier compromise. ME 2 also produced an increase in TEWL but had no dehydrating effect. Subjects then underwent standardized washing with a surfactant solution. Under these conditions, pretreatment with ME 2 also produced dehydration, but to a lesser extent than did pretreatment with ME 1. In the same subjects, the impact of the two MEs on HC penetration (0.5%, 24h occlusion) was evaluated in terms of the chromameter-determined blanching effect compared with that on a site treated only with an occlusive film dressing. The comparator was an ambiphilic cream (Basiscreme (BC) Deutscher Arzneimittel Codex (German Formulary)). Irritative skin redness produced by ME 1 was significant and that produced by ME 2 was slight but visible, compared with BC. HC penetration was demonstrable from all the study products via the blanching effect and was significantly greater from ME 1 and slightly greater from ME 2 than from BC. However, neither ME would improve HC therapy because the irritative effects were so great that the blanching effect of HC formulated in ME 1 was significantly smaller and that of HC in ME 2 slightly smaller than that of HC formulated in BC.

  15. Using different structure types of microemulsions for the preparation of poly(alkylcyanoacrylate) nanoparticles by interfacial polymerization.

    PubMed

    Krauel, K; Davies, N M; Hook, S; Rades, T

    2005-08-18

    A phase diagram of the pseudoternary system ethyloleate, polyoxyethylene 20 sorbitan mono-oleate/sorbitan monolaurate and water with butanol as a cosurfactant was prepared. Areas containing optically isotropic, low viscosity one-phase systems were identified and systems therein designated as w/o droplet-, bicontinuous- or solution-type microemulsions using conductivity, viscosity, cryo-field emission scanning electron microscopy and self-diffusion NMR. Nanoparticles were prepared by interfacial polymerization of selected w/o droplet, bicontinuous- or solution-type microemulsions with ethyl-2-cyanoacrylate. Morphology of the particles and entrapment of the water-soluble model protein ovalbumin were investigated. Addition of monomer to the different types of microemulsions (w/o droplet, bicontinuous, solution) led to the formation of nanoparticles, which were similar in size ( approximately 250 nm), polydispersity index ( approximately 0.13), zeta-potential ( approximately -17 mV) and morphology. The entrapment of the protein within these particles was up to 95%, depending on the amount of monomer used for polymerization and the type of microemulsion used as a polymerization template. The formation of particles with similar characteristics from templates having different microstructure is surprising, particularly considering that polymerization is expected to occur at the water-oil interface by base-catalysed polymerization. Dynamics within the template (stirring, viscosity) or indeed interfacial phenomena relating to the solid-liquid interface appear to be more important for the determination of nanoparticle morphology and characteristics than the microstructure of the template system.

  16. Sulfur Nanoparticles Synthesis and Characterization from H2S Gas, Using Novel Biodegradable Iron Chelates in W/O Microemulsion

    NASA Astrophysics Data System (ADS)

    Deshpande, Aniruddha S.; Khomane, Ramdas B.; Vaidya, Bhalchandra K.; Joshi, Renuka M.; Harle, Arti S.; Kulkarni, Bhaskar D.

    2008-06-01

    Sulfur nanoparticles were synthesized from hazardous H2S gas using novel biodegradable iron chelates in w/o microemulsion system. Fe3+ malic acid chelate (0.05 M aqueous solution) was studied in w/o microemulsion containing cyclohexane, Triton X-100 and n-hexanol as oil phase, surfactant, co-surfactant, respectively, for catalytic oxidation of H2S gas at ambient conditions of temperature, pressure, and neutral pH. The structural features of sulfur nanoparticles have been characterized by X-ray diffraction (XRD), transmission electron microscope (TEM), energy dispersive spectroscopy (EDS), diffused reflectance infra-red Fourier transform technique, and BET surface area measurements. XRD analysis indicates the presence of α-sulfur. TEM analysis shows that the morphology of sulfur nanoparticles synthesized in w/o microemulsion system is nearly uniform in size (average particle size 10 nm) and narrow particle size distribution (in range of 5 15 nm) as compared to that in aqueous surfactant systems. The EDS analysis indicated high purity of sulfur (>99%). Moreover, sulfur nanoparticles synthesized in w/o microemulsion system exhibit higher antimicrobial activity (against bacteria, yeast, and fungi) than that of colloidal sulfur.

  17. Solubilization of Tea Seed Oil in a Food-Grade Water-Dilutable Microemulsion

    PubMed Central

    Deng, Lingli; Que, Fei; Wei, Hewen; Xu, Guangwei; Dong, Xiaowei; Zhang, Hui

    2015-01-01

    Food-grade microemulsions containing oleic acid, ethanol, Tween 20, and water were formulated as a carrier system for tea seed oil (Camellia oleifera Abel.). The effect of ethanol on the phase behavior of the microemulsion system was clearly reflected in pseudo-ternary diagrams. The solubilization capacity and solubilization efficiency of tea seed oil dispersions were measured along the dilution line at a 70/30 surfactant/oil mass ratio with Tween 20 as the surfactant and oleic acid and ethanol (1:3, w/w) as the oil phase. The dispersed phase of the microemulsion (1.5% weight ratio of tea seed oil to the total amount of oil, surfactant, and tea seed oil) could be fully diluted with water without phase separation. Differential scanning calorimetry and viscosity measurements indicated that both the carrier and solubilized systems underwent a similar microstructure transition upon dilution. The dispersion phases gradually inverted from the water-in-oil phase (< 35% water) to the bicontinuous phase (40–45% water) and finally to the oil-in-water phase (> 45% water) along the dilution line. PMID:25996147

  18. Effect of Temperature on the Phase Behavior of Ionic-Nonionic Microemulsions

    PubMed

    Aramaki; Ozawa; Kunieda

    1997-12-01

    Microemulsions are formed over a wide range of temperatures in brine/sodium dodecyl sulfate/polyoxyethylene dodecyl ether (C12EO2 or C12EO3)/decane systems. In a dilute region, lamellar liquid crystal is present instead of bicontinuous microemulsion at the composition at which the HLB of the mixed surfactant is optimum in the given system. The monomeric solubilities of C12EO2 or C12EO3 in oil and the mixing fraction of C12EO2 or C12EO3 in the mixed surfactant layer were determined using the geometrical relation of three-phase tie triangle containing the liquid crystal phase in the composition tetrahedron and were compared at 35 and 60°C. The change in the HLB composition with temperature is well described by increasing the monomeric solubility and decreasing the mixing fraction of nonionic surfactant in the surfactant layer. As a result, temperature-insensitive microemulsions are formed in the SDS-C12EO3 system. Copyright 1997 Academic Press. Copyright 1997Academic Press

  19. Fully dilutable microemulsions embedded with phospholipids and stabilized by short-chain organic acids and polyols.

    PubMed

    Spernath, Aviram; Aserin, Abraham; Garti, Nissim

    2006-07-15

    Evidence on the role of phosphatidylcholine (PC) as a membrane permeability enhancer was the driving force in forming new liquid nanosized (modified microemulsions) oral delivery system containing PC molecules. In this study we have demonstrated the feasibility of constructing phase diagrams with a large isotropic regions capable of being fully diluted with water. The microemulsions were stabilized with mixtures composed of PC and nonionic surfactant (polyoxyethylene-40 hydrogenated castor oil, HECO40) and short-chain organic acid as cosurfactant/cosolvent. When propionic acid served as the cosurfactant/cosolvent, the isotropic region was at its maximum (ca. 72% of the total phase diagram area). The presence of a blend of PC and HECO40 seems to have synergistic effects, forming an isotropic region comprising 72% of the area of the phase diagram, in comparison to 20 and 50% in systems stabilized by PC and HECO40, alone, respectively. The role of the PC molecules in the formation of those microemulsions is demonstrated by comparing three soy lecithins. Lecithin with a high PC content forms larger isotropic regions with more "free dilution" lines. Several nonionic surfactants have been investigated, yet only HECO40 seems to have a packing parameter suitable for the formation of large isotropic U-type systems.

  20. Phase behavior and kinetics of phase separation of a nonionic microemulsion of C12E5/water/1-chlorotetradecane upon a temperature quench.

    PubMed

    Roshan Deen, G; Oliveira, Cristiano L P; Pedersen, Jan Skov

    2009-05-21

    The phase behavior and phase separation kinetics of a model ternary nonionic microemulsion system composed of pentaethylene glycol dodecyl ether (C12E5), water, and 1-chlorotetradecane were studied. With increasing temperature, the microemulsion exhibits the following rich phase behavior: oil-in-water phase (L1+O), droplet microemulsion phase (L1), lamellar liquid crystalline phase (Lproportional), and sponge-like (liquid) phase (L3). The microemulsion with a fixed surfactant-to-oil volume fraction ratio (Phis/Phio) of 0.81 and droplet volume fraction of 0.087 was perturbed from equilibrium by a temperature quench from the L1 region (24 degrees C) to an unstable region L1+O (13 degrees C), where the excess oil phase is in equilibrium with the microemulsion droplets. The process of phase separation in the unstable region was followed by time-resolved small-angle X-ray scattering (TR-SAXS) and time-resolved turbidity methods. Due to the large range of scattering vector (q=0.004-0.22 A(-1)) that is possible to access with the TR-SAXS method, the growth of the oil droplets and shrinking of the microemulsion droplets as a result of phase separation could be studied simultaneously. By using an advanced polydisperse ellipsoidal hard-sphere model, the experimental curves have been quantitatively analyzed. The microemulsion droplets were modeled as polydisperse core-shell ellipsoidal particles, using molecular constraints, and the oil droplets are modeled as polydisperse spheres. The radius of gyration (Rg) of the growing oil droplets, volume fraction of oil in the microemulsion droplets, and polydispersity were obtained from the fit parameters. The volume equivalent radius at the neutral plane between the surfactant head and tail of the microemulsion droplet decreased from 76 to 51 A, while the radius of oil drop increased to 217 A within the 160 min of the experiment. After about 48 min from the temperature quench, the system reaches a steady state and continues to

  1. Synthesis of NaYF4:Yb3+, Er3+ upconversion nanoparticles in normal microemulsions

    PubMed Central

    2011-01-01

    An interface-controlled reaction in normal microemulsions (water/ethanol/sodium oleate/oleic acid/n-hexane) was designed to prepare NaYF4:Yb3+, Er3+ upconversion nanoparticles. The phase diagram of the system was first studied to obtain the appropriate oil-in-water microemulsions. Transmission electron microscopy and X-ray powder diffractometer measurements revealed that the as-prepared nanoparticles were spherical, monodisperse with a uniform size of 20 nm, and of cubic phase with good crystallinity. Furthermore, these nanoparticles have good dispersibility in nonpolar organic solvents and exhibit visible upconversion luminescence of orange color under continuous excitation at 980 nm. Then, a thermal treatment for the products was found to enhance the luminescence intensity. In addition, because of its inherent merit in high yielding and being economical, this synthetic method could be utilized for preparation of the UCNPs on a large scale. PMID:21968102

  2. Optimization of process parameters for ruthenium nanoparticles synthesis by (w/o) reverse microemulsion

    NASA Astrophysics Data System (ADS)

    Nandanwar, S. U.; Barad, J.; Nandwani, S.; Chakraborty, M.

    2015-03-01

    Taguchi OA factorial design method was used to identify the several factors that might affect the particle size of ruthenium nanoparticles prepared by the mixing of two reactive microemulsions. In the present work, the objective of evaluating the factors influencing the particle size had been improvised by studying two qualitative factors viz., effect of different reducing agents and effect of different co-surfactants. Using orthogonal experimental design and analysis technique, the system performance could be analyzed with more objective conclusion through only a small number of simulation experiments. Analysis of variance was carried out to identify the significant factors affecting the response and the best possible factor level combination was determined through. It was found that the formation of ruthenium nanoparticles, microemulsions were greatly influenced by the type of reducing agent used in the technique followed by water-to-surfactant molar ratio.

  3. Nonaqueous microemulsions based on n,n'-alkylimidazolium alkylsulfate ionic liquids.

    PubMed

    Rojas, Oscar; Tiersch, Brigitte; Rabe, Christian; Stehle, Ralf; Hoell, Armin; Arlt, Bastian; Koetz, Joachim

    2013-06-11

    The ternary system composed of the ionic liquid surfactant (IL-S) 1-butyl-3-methylimidazolium dodecylsulfate ([Bmim][DodSO4]), the room temperature ionic liquid (RTIL) 1-ethyl-3-methylimidazolium ethylsulfate ([Emim][EtSO4]), and toluene has been investigated. Three major mechanisms guiding the structure of the isotropic phase were identified by means of conductometric experiments, which have been correlated to the presence of oil-in-IL, bicontinuous, and IL-in-oil microemulsions. IL-S forms micelles in toluene, which swell by adding RTIL as to be shown by dynamic light scattering (DLS) and small-angle X-ray scattering (SAXS) experiments. Therefore, it is possible to form water-free IL-in-oil reverse microemulsions ≤10 nm in size as a new type of nanoreactor.

  4. Slow relaxation mode in concentrated oil-in-water microemulsions consisting of repulsive droplets

    NASA Astrophysics Data System (ADS)

    Hattori, Y.; Ushiki, H.; Courbin, L.; Panizza, P.

    2007-02-01

    The present contribution reports on the observation of two diffusive relaxation modes in a concentrated microemulsion made of repulsive droplets. These two modes can be interpreted in the frame of Weissman’s and Pusey’s theoretical pioneering works. The fast mode is associated to the collective diffusion of droplets whereas the slow one corresponds to the relaxation of droplet concentration fluctuations associated with composition and/or size. We show that (i) repulsive interactions considerably slow down the latter and (ii) a generalized Stokes Einstein relationship between its coefficient of diffusion and the Newtonian viscosity of the solutions, similar to the Walden’s rule for electrolytes, holds for concentrated microemulsion systems made of repulsive droplets.

  5. Effect of microemulsions on cell viability of human dermal fibroblasts

    NASA Astrophysics Data System (ADS)

    Li, Juyi; Mironava, Tatsiana; Simon, Marcia; Rafailovich, Miriam; Garti, Nissim

    Microemulsions are optically clear, thermostable and isotropic mixture consisting of water, oil and surfactants. Their advantages of ease preparation, spontaneous formation, long-term stability and enhanced solubility of bioactive materials make them great potentials as vehicles in food and pharmaceutical applications. In this study, comparative in vitro cytotoxicity tests were performed to select a best formulation of microemulsion with the least toxicity for human dermal fibroblasts. Three different kinds of oils and six different kinds of surfactants were used to form microemulsions by different ratios. The effect of oil type and surfactant type as well as their proportions on cell proliferation and viability were tested.

  6. Styrene polymerization in three-component cationic microemulsions

    SciTech Connect

    Perez-Luna, V.H.; Puig, J.E. ); Castano, V.M. ); Rodriguez, B.E.; Murthy, A.K.; Kaler, E.W. )

    1990-06-01

    The polymerization of styrene in three-component dodecyltrimethylammonium bromide (DTAB) microemulsions is reported. The structure of the unpolymerized microemulsions, determined by conductimetry and quasielastic light scattering (QLS), is consistent with styrene-swollen micelles in equilibrium with regular micelles, both dispersed in an aqueous phase. Polymerization of these transparent microemulsions, monitored by QLS an dilatometry, produced stable, bluish monodisperse microlatices with particle radii ranging from 20 to 30 nm, depending on styrene content. Polymerization initiation appears to occur in the styrene-swollen micelles, and the polymer particles grow by recruiting monomer and surfactant from uninitiated droplets and small micelles.

  7. Polymer-microemulsion complexes for the enhanced recovery of oil

    SciTech Connect

    Baker, E.G.; Canter, N.H.; Robbins, M.L.

    1982-10-12

    A polymer-microemulsion complex useful for the enhanced recovery of crude oil is disclosed. The polymer is polyethylene oxide or polyvinyl pyrrolidone and interacts with the surfactant of the microemulsion to form a physical association. The resulting complex is characterized by a complexation energy of at least 2 kcal/mole. The polymer microemulsion complexes are stable at high salinity, reduce adsorption and retention by the formation, lower interfacial tension, achieve retentions as low as 0.1 mg surfactant/gm sand at high salinity and provide for early banking , as well as high recovery of oil.

  8. Cy3 in AOT reverse micelles II. Probing intermicellar interactions using fluorescence correlation spectroscopy.

    PubMed

    McPhee, Jeffrey T; Scott, Eric; Levinger, Nancy E; Van Orden, Alan

    2011-08-11

    Cyanine-3 (Cy3) fluorescent dye molecules confined in sodium di-2-ethylhexyl sulfosuccinate (AOT) reverse micelles were examined using dynamic light scattering and fluorescence correlation spectroscopy to probe the kinetics of Cy3 dye and reverse micelle aggregation. This study explored a range of reverse micelle sizes, defined as w(0) = [H(2)O]/[AOT], in which the occupation number ranged from one Cy3 molecule per ∼10(5) to ∼10(6) reverse micelles. These measurements reveal that in the smallest reverse micelle, w(0) = 1, the Cy3 molecules aggregate to form H-aggregate dimers, and the Cy3 dimerization is accompanied by the formation of a transient dimer between reverse micelles. Transient reverse micelle dimer particles are only observed in the small fraction of Cy3-labeled reverse micelles probed by fluorescence correlation spectroscopy and are not observed in the bulk solution probed by dynamic light scattering. Furthermore, fluorescence correlation spectroscopy makes it possible to probe the size and shape of these dimers, revealing prolate ellipsoid-shaped particles with twice the volume and surface area of a single reverse micelle.

  9. Rheology of a Polymeric Bicontinuous Microemulsion

    NASA Astrophysics Data System (ADS)

    Krishnan, Kasiraman; Lodge, Timothy P.; Bates, Frank S.; Burghardt, Wesley R.

    2002-03-01

    We have investigated the rheological properties of a model polymeric bicontinuous microemulsion. The microemulsion consists of a ternary blend of poly(ethyl ethylene) (PEE), poly(dimethyl siloxane) (PDMS) and the diblock copolymer PEE-PDMS. Steady shear measurements reveal four regimes as a function of shear rate. Newtonian behavior is observed at low shear rates (regime I), whereas shear thinning occurs in regime II. The striking feature is a stress plateau in regime III, independent of shear rate; the stress increases with shear rate again in regime IV. The morphologies in different regimes were characterized by neutron scattering, x-ray scattering, light scattering and microscopy, and these provide evidence for the occurrence of flow-induced phase separation. Transient rheological measurements reveal a behavior similar to worm-like micelles. Transient measurements for step changes in shear rate between different regimes confirm the proposed morphologies. Equilibrium rheological measurements show similarities with diblock copolymer lamellar phases just above the order-disorder transition.

  10. Microemulsion Formulation of Carbendazim and Its In Vitro Antifungal Activities Evaluation

    PubMed Central

    Leng, Pengfei; Zhang, Zhiming; Li, Qian; Zhao, Maojun; Pan, Guangtang

    2014-01-01

    The fungus Rhizoctonia solani Kuhn is a widespread and destructive plant pathogen with a very broad host range. Although various pathogens, including R. solani, have been traditionally controlled using chemical pesticides, their use faces drawbacks such as environmental pollution, development of pesticide resistance, and other negative effects. Carbendazim is a well-known antifungal agent capable of controlling a broad range of plant diseases, but its use is hampered by its poor aqueous solubility. In this study, we describe an environmentally friendly pharmaceutical microemulsion system using carbendazim as the active ingredient, chloroform and acetic acid as solvents, and the surfactants HSH and 0204 as emulsifiers. This system increased the solubility of carbendazim to 30 g/L. The optimal microemulsion formulation was determined based on a pseudo-ternary phase diagram; its physicochemical characteristics were also tested. The cloud point was greater than 90°C and it was resistant to freezing down to −18°C, both of which are improvements over the temperature range in which pure carbendazim can be used. This microemulsion meets the standard for pesticide microemulsions and demonstrated better activity against R. solani AG1-IA, relative to an aqueous solution of pure carbendazim (0.2 g/L). The mechanism of activity was reflected in the inhibition of against R. solani AG1-IA including mycelium growth, and sclerotia formation and germination were significantly better than that of 0.2 g/L carbendazim water solution according to the results of t-test done by SPSS 19. PMID:25310219

  11. A SANS study of the interfacial curvatures and the phase behavior in bicontinuous microemulsions

    NASA Astrophysics Data System (ADS)

    Choi, Sung-Min

    A microemulsion is a three-component system in which oil and water are solubilized via an interfacial surfactant monolayer. Depending on the composition and various external conditions, it exhibits a wide variety of phases with corresponding mesoscopic scale interfacial structures. For scientific as well as industrial purposes, knowledge of the relation between the interfacial structure and the phase behavior is crucial but its quantitative measure is lacking. To identify the relation in a quantitative way, the natural parameters to be measured are the interfacial curvatures: Gaussian, mean, and square mean curvatures. A new small-angle neutron scattering (SANS) data analysis method to extract the interfacial curvatures was developed and applied to various microemulsions. The method involves the use of a clipped random wave model with an inverse 8th order polynomial spectral function. The spectral density function contains three basic length scales: the inter- domain distance, the coherence length, and the surface roughness parameter. These three length scales are essential to describe mesoscopic scale interfaces. A series of SANS experiments were performed at various phase points of isometric and non-isometric microemulsions. Using the developed model, the three interfacial curvatures at each phase point were determined for the first time in a practical way. In isometric bicontinuous microemulsions, the Gaussian curvature is negative and has a parabolic dependence on the surfactant volume fraction. In non-isometric systems, based on the measured interfacial curvatures, a characteristic structural transformation was identified. As the water and oil volume ratio moves away from unity, the bicontinuous structure transforms to a spherical structure through an intermediate cylindrical structure. (Copies available exclusively from MIT Libraries, Rm. 14- 0551, Cambridge, MA 02139-4307. Ph. 617-253-5668; Fax 617-253-1690.)

  12. An amine-oxide surfactant-based microemulsion for the cleaning of works of art.

    PubMed

    Baglioni, Michele; Jàidar Benavides, Yareli; Berti, Debora; Giorgi, Rodorico; Keiderling, Uwe; Baglioni, Piero

    2015-02-15

    Surfactant-based aqueous fluids, such as micellar solutions and microemulsions, are effective, safe and selective media for cleaning operations in conservation of cultural heritage. The search for better-performing systems and eco-friendly cleaning systems is currently a major goal in conservation science. We report here on a ternary o/w microemulsion, composed of diethyl carbonate (DC) as the oil phase and N,N-Dimethyldodecan-1-amine oxide (DDAO) as the surfactant. DDAO is a well known and widely used detergent and solubilizing agent, selected here for its degradability and eco-compatibility. Due to its nonionic/cationic nature, it can be used also when nonionic-based formulations become ineffective because of clouding and phase separation. Moreover, DDAO is insensitive to the presence of divalent metal ions, usually abundant in wall paintings substrates. Small-Angle Neutron Scattering (SANS) provided detailed information about the nanostructure of the surfactant aggregates. Finally, the cleaning effectiveness of the nanofluid was assessed both on fresco mock-ups and on real wall paintings conserved in the archeological site of Tulum, Mexico. Here, conservators successfully used the microemulsion to remove naturally aged films of complex polymer mixtures from the works of art surface. Copyright © 2014 Elsevier Inc. All rights reserved.

  13. Use of microemulsions as vehicles for nucleophilic reagents in cosmetic formulations.

    PubMed

    Parra, J L; García Domínguez, J J; Comelles, F; Sänchez, J; Solans, C; Pelejero, C; Balaguer, F

    1985-06-01

    Synopsis The modifications of chemical reactivity induced in the human hair during its treatment with oxidative (H(2)O(2)) or reductive (HSO(3)Na) agents via a micellar or a microemulsion system have been investigated. For this purpose, phase diagrams of micellar solutions and microcmulsions with H(2)O(2) or NaSO(3)H have been made in order to find out the corresponding areas of solubility. The properties of conductivity, surface tension and light scattering of various monophasic compositions as a function of their water content, have been studied. As a result of the chemical reactivity data of human hair obtained through the reaction of H(2)O(2) or HSO(3)Na via a micellar or a microemulsion system, it appears reasonable to predict a more effective reaction of such agents with cystine residues existing in keratinic substrates, particularly when they are applied via a microemulsion. The decrease of the water content of the compositions considered, increases chemical reactivity of the keratinic proteins favouring the formation of cysteine and of cysteic acid in the reductive or oxidative treatments respectively.

  14. Seasonal differences in aerosol water may reconcile AOT and surface mass measurements in the Southeast U.S.

    NASA Astrophysics Data System (ADS)

    Nguyen, T. K. V.; Ghate, V. P.; Carlton, A. M. G.

    2015-12-01

    Summertime aerosol optical thickness (AOT) in the Southeast U.S. is high and sharply enhanced (2-3 times) compared to wintertime AOT. This seasonal pattern is unique to the Southeast U.S. and is of particular interest because temperatures there have not warmed over the past 100 years, contrasting with trends in other U.S. regions. Some investigators hypothesize the Southeast temperature trend is due to secondary organic aerosols (SOA) formed from interactions of biogenic volatile organic compounds (BVOCs) and anthropogenic emissions that create a cooling haze. However, aerosol measurements made at the surface do not exhibit strong seasonal differences in mass or organic fraction to support this hypothesis. In this work, we attempt to reconcile the spatial and temporal distribution of AOT over the U.S. with surface mass measurements by examining trends in particle-phase liquid water, an aerosol constituent that effectively scatters radiation and is removed from aerosols in mass measurements at routine surface monitoring sites. We employ the thermodynamic model ISORROPIA (v2.1) to estimate surface and aloft aerosol water mass concentrations at locations of Interagency Monitoring of Protected Visual Environments (IMPROVE) sites using measured speciated ion mass concentrations and NCEP North American Regional Reanalysis (NARR) meteorological data. Results demonstrate strong seasonal differences in aerosol water in the eastern compared to the western part of the U.S., consistent with geographic patterns in AOT. The highest mean regional seasonal difference from 2000 to 2007 is 5.5 μg m-3 and occurs the Southeast, while the lowest is 0.44 μg m-3 and occurs in the dry Mountain West. Our findings suggest 1) similarity between spatial trends in aerosol water in the U.S. and previously published AOT data from the MODIS-TERRA instrument and 2) similar interannual trends in mean aerosol water and previously published interannual AOT trends from MISR, MODIS-TERRA, MODIS

  15. Core-shell nano-architectures: the incorporation mechanism of hydrophobic nanoparticles into the aqueous core of a microemulsion.

    PubMed

    Scorciapino, Mariano A; Sanna, Roberta; Ardu, Andrea; Orrù, Federica; Casu, Mariano; Musinu, Anna; Cannas, Carla

    2013-10-01

    This work presents an in-depth investigation of the molecular interactions in the incorporation mechanism of colloidal hydrophobic-capped nanoparticles into the hydrophilic core of reverse microemulsions. (1)H Nuclear Magnetic Resonance (NMR) was employed to obtain molecular level details of the interaction between the nanoparticles capping amphiphiles and the microemulsion surfactants. The model system of choice involved oleic acid (OAC) and oleylamine (OAM) as capping molecules, while igepal-CO520 was the surfactant. The former were studied both in their "free" state and "ligated" one, i.e., bound to nanoparticles. The latter was investigated either in cyclohexane (micellar solution) or in water/cyclohexane microemulsions. The approach was extremely useful to gain a deeper understanding of the equilibria involved in this complex system (oleic acid capped-Bi2S3 in igepal/water/cyclohexane microemulsions). In difference to previously proposed mechanisms, the experimental data showed that the high affinity of the capping ligands for the reverse micelle interior was the drivingforce for the incorporation of the nanoparticles. A simple ligand-exchange mechanism could be ruled out. The collected information about the nanoparticle incorporation mechanism is extremely useful to develop new synthetic routes with an improved/tuned coating efficiency, in order to tailor the core-shell structure preparation.

  16. Utilization of Microemulsions from Rhinacanthus nasutus (L.) Kurz to Improve Carotenoid Bioavailability

    PubMed Central

    Ho, Nai-Hsing; Inbaraj, Baskaran Stephen; Chen, Bing-Huei

    2016-01-01

    Carotenoids have been known to reduce the risk of several diseases including cancer and cardiovascular. However, carotenoids are unstable and susceptible to degradation. Rhinacanthus nasutus (L.) Kurz (R. nasutus), a Chinese medicinal herb rich in carotenoids, was reported to possess vital biological activities such as anti-cancer. This study intends to isolate carotenoids from R. nasutus by column chromatography, identify and quantify by HPLC-MS, and prepare carotenoid microemulsions for determination of absolute bioavailability in rats. Initially, carotenoid fraction was isolated using 250 mL ethyl acetate poured into an open-column packed with magnesium oxide-diatomaceous earth (1:3, w/w). Fourteen carotenoids including internal standard β-apo-8′-carotenal were resolved within 62 min by a YMC C30 column and gradient mobile phase of methanol-acetonitrile-water (82:14:4, v/v/v) and methylene chloride. Highly stable carotenoid microemulsions were prepared using a mixture of CapryolTM90, Transcutol®HP, Tween 80 and deionized water, with the mean particle being 10.4 nm for oral administration and 10.7 nm for intravenous injection. Pharmacokinetic study revealed that the absolute bioavailability of carotenoids in microemulsions and dispersion was 0.45% and 0.11%, respectively, while a much higher value of 6.25% and 1.57% were shown for lutein, demonstrating 4-fold enhancement in bioavailability upon incorporation of R. nasutus carotenoids into a microemulsion system. PMID:27150134

  17. Sample stacking for the analysis of catechins by microemulsion EKC.

    PubMed

    Huang, Hsi-Ya; Huang, I-Yun; Liang, Hsin-hui; Lee, Szetsen

    2007-06-01

    In this study, an on-line concentration method, ASEI (anion-selective exhaustive injection)-sweeping technology which was coupled with microemulsion EKC (MEEKC), was used to analyze and detect six catechins ((-)-epicatechin, (+)-catechin, (-)-epigallocatechin gallate, (-)-epicatechin gallate, (-)-epigallocatechin, and (-)-gallocatechin). In addition to the effects of the buffer pH and electrolyte concentration on stacking, the compositions of microemulsion (types of oil phase, and types and levels of cosurfactant) also dominated the stacking effect of catechins. In MEEKC, the effect of the type of oil in microemulsion on separation mechanism is often unclear. This study had demonstrated that the oil type in microemulsion indeed altered the affinity of oil droplets with analytes. Finally, this proposed ASEI-sweeping MEEKC method was able to detect trace level of catechins in food products that was not previously possible by a normal MEEKC method.

  18. Surfactant ionic liquid-based microemulsions for polymerization.

    PubMed

    Yan, Feng; Texter, John

    2006-07-05

    Surfactants based on imidazolium ionic liquids (ILs), including polymerizable surfactant ILs, have been synthesized and used to stabilize polymerizable microemulsions useful for producing polymer nanoparticles, gels, and open-cell porous materials.

  19. Separation of neutral compounds by microemulsion electrokinetic chromatography: fundamental studies on selectivity.

    PubMed

    Gabel-Jensen, C; Honoré Hansen, S; Pedersen-Bjergaard, S

    2001-04-01

    The selectivity of microemulsion electrokinetic chromatography (MEEKC) was studied utilizing some uncharged model compounds like aromatic amides, steroids, and esters of nicotinic acid. The cosurfactant of the microemulsion was found to be the most important factor affecting the selectivity, and alteration between 6.6% of 1-propanol, 1-butanol, tetrahyd