Cloud point extraction assisted spectrophotometric quantification of trace boron impurity in uranium-based nuclear fuels.

The separation of boron in nuclear fuels by cloud point extraction (CPE) has been a challenge due to high acidity of digested sample solutions. High acidity hampers the coacervation of micelles. As a result, the cloud point temperature increases and thus could cause the inevitable loss of boron as volatile species. Herein we have proposed a novel CPE-assisted colorimetric method for the quantification of traces of boron (B) in uranium-based fuels. A 1:1 mixture of 2-ethyl hexane-1,3-diol (EHD) and curcumin dispersed in Triton X-114 surfactant was used in the proposed CPE process. We had investigated several compounds to act as micelle surface modifiers. Among them, only bromine water (Br2) was found not only to lower the cloud point temperature (CPT, from 80 °C to 42 ± 2 °C) but also resulted in the quantitative recovery of boron (≥95%). The CPE of boron from uranium matrix in a 2.0 mol L-1 HCl medium was suitable for direct chemical quality assurance of routine uranium-based fuels. The molar extinction coefficient of the boron-EHD-curcumin complex was found to be 4.75 × 105 L mol-1 cm-1 (λmax at 458 nm) in N,N-dimethyl formamide medium. The linear dynamic range and detection limit of the proposed analytical procedure were calculated to be 10-150 ng mL-1 and 0.8 ng mL-1 respectively. The proposed analytical methodology was validated by analysis of three in-house working reference materials of uranium. Determination of traces of boron in two uranium dioxide and two metallic uranium samples were found to demonstrate the applicability of the method. The relative standard deviation of the proposed method was found to be of 3-5%.

Biochemical characterization and enhanced production of endoxylanase from thermophilic mould Myceliophthora thermophila.

Endoxylanase production from M. thermophila BJTLRMDU3 using rice straw was enhanced to 2.53-fold after optimization in solid state fermentation (SSF). Endoxylanase was purified to homogeneity employing ammonium sulfate precipitation followed by gel filtration chromatography and had a molecular mass of ~ 25 kDa estimated by SDS-PAGE. Optimal endoxylanase activity was recorded at pH 5.0 and 60 °C. Purified enzyme showed complete tolerance to n-hexane, but activity was slightly inhibited by other organic solvents. Among surfactants, Tweens (20, 60, and 80) and Triton X 100 slightly enhanced the enzyme activity. The Vmax and Km values for purified endoxylanase were 6.29 µmol/min/mg protein and 5.4 mg/ml, respectively. Endoxylanase released 79.08 and 42.95% higher reducing sugars and soluble proteins, respectively, which control after 48 h at 60 °C from poultry feed. Synergistic effect of endoxylanase (100 U/g) and phytase (15 U/g) on poultry feed released higher amount of reducing sugars (58.58 mg/feed), soluble proteins (42.48 mg/g feed), and inorganic phosphate (28.34 mg/feed) in contrast to control having 23.55, 16.98, and 10.46 mg/feed of reducing sugars, soluble proteins, and inorganic phosphate, respectively, at 60 °C supplemented with endoxylanase only.

Determination of trace levels of selenium in natural water, agriculture soil and food samples by vortex assisted liquid-liquid microextraction method: Multivariate techniques.

A green vortex assisted based liquid-liquid microextraction (VA-LLME) method was developed for preconcentration of selenium. Ammonium pyrrolidine dithiocarbamate (APDC) was used to form a hydrophobic complex with selenium in natural water, agricultural soil and food samples by GFAAS. Whereas Triton X-114, a nonionic surfactant and 1-butyl-3-methylimidazolium hexafluorophosphate ionic liquid were used for Se extraction as a dispersing medium. The conical flasks contents were shack on a vortex mixer to increase the extraction efficiency. Multivariate techniques were used to evaluate extraction parameters; pH, vortex time, APDC amount, volume of ionic liquid and Triton X-114 and centrifugation rate on the recovery of Se. The central composite design (CCD) was used for further optimization of the essential extraction parameters. The enhancement factor and limit of detection were obtained as 98.7 and 0.07 µg L-1. The certified reference materials was used for accuracy of method and the related standard deviation was found to be 3.51%. The resulted data indicated that concentrations of Se in all types of water samples were below the permissible limit recommended by WHO.

Production and properties of a bioemulsifier obtained from a lactic acid bacterium.

In the present work, the production of bioemulsifier (BE) by a lactic acid bacterium (LAB) grown at 25 °C in lactic whey-based media for 24 h was evaluated. Maximum production was detected in a medium containing yeast extract, peptone and lactic whey (LAPLW medium), with a yield of 270 mg L-1. The BE proved to be more innocuous for Caco-2 cells, used as a toxicological indicator, than the non-ionic surfactant Triton X-100. In addition, the microbial product presented higher stability to changes in temperature (37 °C to 100 °C), pH (2-10), and salt concentration (5% and 20%, w/v) than the synthetic surfactant. Regarding emulsifying capacity tested against different hydrophobic substrates (kerosene, motor oil, diesel, sunflower oil, and grape oil), the BE displayed E24 values similar to or even better than those of Triton X-100. Finally, Triton X-100 caused irreversible modifications on the giant unilamellar vesicles (used as model membrane system), promoting the solubilization of the lipid bilayers. Nevertheless, BE induced temporary modifications of the membrane, which is associated with incorporation of the bioproduct in the outer layer. These results demonstrate the role of BE in biological processes, including reversible changes in microbial membranes to enhance the access to hydrophobic substrates.

Ex situ soil washing of highly contaminated silt loam soil using core-crosslinked amphiphilic polymer nanoparticles.

Non-ionic surfactants (Triton X-100 and Brij 30) and core-crosslinked amphiphilic polymer (CCAP) nanoparticles were used as extractants in the ex situ soil washing of silt loam soil contaminated with large quantities of petroleum oil, and their soil-washing performances were compared. Following washing with the surfactants, highly turbid aqueous solutions containing large numbers of soil and petroleum oil particles were produced. In contrast, the CCAP nanoparticles successfully extracted the petroleum oils from the soil samples without the formation of such a turbid aqueous solution. In addition, the CCAP nanoparticles extracted 96% of the petroleum oils, which is a significantly larger quantity than that by Brij 30 and Triton X-100 under equivalent conditions. Indeed, owing to their crosslinked micelle-like structure, the CCAP nanoparticles maintained their nanostructure even upon contact with a highly contaminated silt loam soil matrix, thereby resulting in the extraction of only the hydrophobic oily contaminants from the soil matrix and avoiding the formation of dispersions of soil particles and hydrophobic contaminants. As such, CCAP nanoparticles could be considered as suitable washing materials for highly contaminated silt loam soils.

Sensitive analysis of curcuminoids via micellar electrokinetic chromatography with laser-induced native fluorescence detection and mixed micelles-induced fluorescence synergism.

Curcuminoids, the major bioactive constituents of traditional medicine known as turmeric, have exhibited extensive therapeutic benefits. Excited by violet-blue light, curcuminoids can emit native fluorescence, making them possible to be detected with high sensitivity and specificity by laser-induced native fluorescence (LINF). Here, a commercial 445 nm laser diode was used as an excitation source to construct a confocal laser-induced fluorescence (LIF) detector and then a complete capillary electrophoresis (CE) system coupled with LIF detection was established. With three major curcuminoids, curcumin, demethoxy curcumin (DMC) and bisdemethoxy curcumin (BDMC) as target analytes, a micellar electrokinetic chromatography (MEKC) method was proposed using mixed micelles consisting of Triton X-100 and SDS to sensitize the native fluorescence of curcuminoids and enhance their separation efficiency. Fluorescence spectra revealed that the mixed micelles induced fluorescence synergism could enhance the signals of three curcuminoids by 77-, 57-, and 47-fold for curcumin, DMC, and BDMC. After systematic investigation, the optimal separation buffer for curcuminoids was chosen as follows: 20 mM Triton X-100, 20 mM SDS, 30% (v/v) methanol in 10 mM borax solution at pH 10.0. Under these conditions, a baseline separation of three curcuminoids was achieved within 10 min and the detection limits were found to be 4.1, 2.6, and 0.4 ng/mL for curcumin, DMC, and BDMC, respectively. Furthermore, the developed MEKC-LINF method was validated in terms of precision, linearity, accuracy and successfully applied for the determination of three curcuminoids in turmeric, medicinal turmeric liniment, curry seasoning, and human urine samples.

Voltammetric determination of thujone in herbal matrices in the presence of Triton X-100.

A simple, sensitive and rapid method of low concentration of thujone determination using Controlled Growth Mercury Drop Electrode and Differential Pulse Voltammetry was described. The reduction of thujone in phosphoric acid or potassium nitrate, involves a quasi-reversible and adsorption-controlled two-electron process. In voltammetric experiments the addition of ethanol and Triton X-100 is recommended. Experimental conditions, such as composition of supporting electrolyte, concentration of Triton X-100 and operation parameters were established. The optimal electrolyte should contain: 0.04 mol L-1 phosphoric acid (pH = 1.9) or 0.05 mol L-1 potassium nitrate (pH = 6.4), 0.0002% Triton X-100 and 9.6% ethanol. The calibration graph was linear from 0.7 to 140 mgL-1 of thujone in H3PO4 as supporting electrolyte and from 0.7 to 115 mgL-1 of the analyte in KNO3. The detection limit was 0.4 mgL-1 in H3PO4 and 0.6 mgL-1 in KNO3, with the correlation coefficient of 0.998. The influence of interfering substances, such as Al(III), Bi(III), Cd(II), Cr(III), Cu(II), Pb(II), Tl(I), V(III) and Zn(II) was studied. The proposed method was validated by the thujone recovery study from the specially prepared spiked herbal matrices and alcohol extract. The considered real sample was thuja oil, in which thujone was successfully determined. All measurements were performed without sample preparation.

High-Yield and Sustainable Production of Phosphatidylserine in Purely Aqueous Solutions via Adsorption of Phosphatidylcholine on Triton-X-100-Modified Silica.

Triton X-100 was covalently bound to a surface of silica and acted as an anchor molecule to facilitate the adsorption of phosphatidylcholine (PC) in a purely aqueous solution. The silica-adsorbed PC obtained was successfully used for phospholipase D (PLD)-mediated transphosphatidylation in the production of phosphatidylserine (PS). Organic solvents were completely avoided in the whole production process. The PC loading and PS yield reached 98.9 and 99.0%, respectively. Two adsorption models were studied, and the relevant parameters were calculated to help us understand the adsorption and reaction processes deeply. In addition, the silica-adsorbed PC provides a promising way to continuously biosynthesize PS. A packed-bed reactor was employed to demonstrate the process flow of the continuous production of PS. The recyclability and stability of the Triton-X-100-modified silica were excellent, as demonstrated by its use 30 times during continuous operation without any loss of the productivity.

Discovery of hyaluronidase inhibitors from natural products and their mechanistic characterization under DMSO-perturbed assay conditions.

The present study discovered four novel hyaluronan-degrading enzyme (hyaluronidase) inhibitors including chikusetsusaponins and catechins through the activity-guided separation of Panax japonicus and Prunus salicina, respectively. Although the discovery resulted in identification of usual frequent hitters, subsequent mechanistic characterizations under our DMSO-perturbed assay conditions and related protocols revealed that chikusetusaponin IV would serve as an aggregating and non-specific binding inhibitor, while (-)-epicatechin would interact specifically with enzyme at the catalytic site or more likely at a kind of catechin-binding site with a relatively week inhibitory activity. The latter description might provide a possible explanation for the well-known fact that a series of catechin have been described as frequent hitters in biological assays with a moderate activity. Thus, the present study demonstrated a practical and robust methodology to characterize initial screening hits mechanistically molecule-by-molecule in the early stage of natural product-based drug discovery.

Clear, Aqueous Topical Drop of Triamcinolone Acetonide.

The objective of this study was to develop a clear aqueous mixed nanomicellar formulation (NMF) of triamcinolone acetonide (TA) with a combination of nonionic surfactant hydrogenated castor oil 60 (HCO-60) and octoxynol-40 (Oc-40). In order to delineate the effects of drug-polymer interactions on entrapment efficiency (EE), loading efficiency (LE), and critical micellar concentration (CMC), a design of experiment (DOE) was performed to optimize the formulation. In this study, full-factorial design has been used with HCO-60 and OC-40 as independent variables. All formulations were prepared following solvent evaporation and film rehydration method, characterized with size, polydispersity, shape, morphology, EE, LE, and CMC. A specific blend of HCO-60 and Oc-40 at a particular wt% ratio (5:1.5) produced highest drug EE, LE, and smallest CMC (0.0216 wt%). Solubility of TA in NMF improved 20 times relative to normal aqueous solubility. Qualitative 1H NMR studies confirmed the absence of free drug in the outer aqueous NMF medium. Moreover, TA-loaded NMF appeared to be highly stable and well tolerated on human corneal epithelial cells (HCEC) and human retinal pigment epithelial cells (D407 cells). Overall, these studies suggest that TA in NMF is safe and suitable for human topical ocular drop application.

Size distribution analysis of influenza virus particles using size exclusion chromatography.

Size exclusion chromatography is a standard method in quality control of biopharmaceutical proteins. In contrast, vaccine analysis is often based on activity assays. The hemagglutination assay is a widely accepted influenza quantification method, providing no insight in the size distribution of virus particles. Capabilities of size exclusion chromatography to complement the hemagglutination assay are investigated. The presented method is comparatively robust regarding different buffer systems, ionic strength and additive concentrations. Addition of 200mM arginine or sodium chloride is necessary to obtain complete virus particle recovery. 0.5 and 1.0M arginine increase the hydrodynamic radius of the whole virus particles by 5nm. Sodium citrate induces virus particle aggregation. Results are confirmed by dynamic light scattering. Retention of a H1N1v strain correlates with DNA contents between 5ng/mL and 670ng/mL. Quantitative elution of the virus preparations is verified on basis of hemagglutination activity. Elution of hemagglutination inducing compounds starts at a flow channel diameter of 7000nm. The universal applicability is demonstrated with three different influenza virus samples, including an industrially produced, pandemic vaccine strain. Size distribution of the pandemic H1N1v 5258, H1N1 PR/8/34, and H3N2 Aichi/2/68 preparations spreads across inter- and intra-particle volume and extends to the secondary interaction dominated range. Thus, virus particle debris seems to induce hemagglutination. Fragments generated by 0.5% Triton™ X-100 treatment increase overall hemagglutination activity.

Stabilization of Candida antarctica Lipase B (CALB) Immobilized on Octyl Agarose by Treatment with Polyethyleneimine (PEI).

Lipase B from Candida antarctica (CALB) was immobilized on octyl agarose (OC) and physically modified with polyethyleneimine (PEI) in order to confer a strong ion exchange character to the enzyme and thus enable the immobilization of other enzymes on its surface. The enzyme activity was fully maintained during the coating and the thermal stability was marginally improved. The enzyme release from the support by incubation in the non-ionic detergent Triton X-100 was more difficult after the PEI-coating, suggesting that some intermolecular physical crosslinking had occurred, making this desorption more difficult. Thermal stability was marginally improved, but the stability of the OCCALB-PEI was significantly better than that of OCCALB during inactivation in mixtures of aqueous buffer and organic cosolvents. SDS-PAGE analysis of the inactivated biocatalyst showed the OCCALB released some enzyme to the medium during inactivation, and this was partially prevented by coating with PEI. This effect was obtained without preventing the possibility of reuse of the support by incubation in 2% ionic detergents. That way, this modified CALB not only has a strong anion exchange nature, while maintaining the activity, but it also shows improved stability under diverse reaction conditions without affecting the reversibility of the immobilization.

Determination and speciation of trace and ultratrace selenium ions by energy-dispersive X-ray fluorescence spectrometry using graphene as solid adsorbent in dispersive micro-solid phase extraction.

A dispersive micro-solid phase extraction (DMSPE) with graphene as a solid adsorbent and ammonium pyrrolidinedithiocarbamate (APDC) as a chelating agent was proposed for speciation and detemination of inorganic selenium by the energy-dispersive X-ray fluorescence spectrometry (EDXRF). In developed DMSPE, graphene particles are dispersed throughout the analyzed solution, therefore reaction between Se(IV)-APDC complexes and graphene nanoparticles occurs immediately. The concentration of Se(VI) is calculated as the difference between the concentration of selenite after and before prereduction of selenate. A central composite face-centered design with 3 center points was performed in order to optimize conditions and to study the effect of four variables (pH of the sample, concentration of APDC, concentration of Triton-X-100, and sample volume). The best results were obtained when suspension consisting of 200 µg of graphene nanosheets, 1.2 mg of APDC and 0.06 mg of Triton-X-100 was rapidly injected to the 50 mL of the analyzed solution. Under optimized conditions Se ions can be determined with a very good recovery (97.7±5.0% and 99.2±6.6% for Se(IV) and Se(VI), respectively) and precision (RSD=5.1-6.6%). Proposed DMSPE/EDXRF procedure allowed to obtain low detection limits (0.032 ng mL(-1)) and high enrichment factor (1013±15). The proposed methodology was successfully applied for the determination of Se in mineral, tap, lake and sea water samples as well as in biological materials (Lobster Hepatopancreas and Pig Kidney).

Cellular uptake of Nigella sativa oil-PLGA microparticle by PC-12 cell line.

The aim of this study is to investigate the cell uptake of Nigella sativa oil (NSO)-PLGA microparticle by neuron-like PC-12 cells in comparison to surfactants; hydrophilic (Tween 80 & Triton X100) and hydrophobic (Span 80). Solvent evaporation was used to precisely control the size, zeta potential and morphology of the particle. The results revealed varying efficiencies of the cell uptake by PC-12 cells, which may be partially attributed to the surface hydrophobicity of the microparticles. Interestingly, the uptake efficiency of PC-12 cells was higher with the more hydrophilic microparticle. NSO microparticle showed evidence of being preferably internalised by mitotic cells. Tween 80 microparticle showed the highest cell uptake efficiency with a concentration-dependent pattern suggesting its use as uptake enhancer for non-scavenging cells. In conclusion, PC-12 cells can take up NSO-PLGA microparticle which may have potential in the treatment of neurodegenerative disease.

Mechanism of a decrease in potency for the recombinant influenza A virus hemagglutinin H3 antigen during storage.

The recombinant hemagglutinin (rHA)-based influenza vaccine Flublok® has recently been approved in the United States as an alternative to the traditional egg-derived flu vaccines. Flublok is a purified vaccine with a hemagglutinin content that is threefold higher than standard inactivated influenza vaccines. When rHA derived from an H3N2 influenza virus was expressed, purified, and stored for 1 month, a rapid loss of in vitro potency (∼50%) was observed as measured by the single radial immunodiffusion (SRID) assay. A comprehensive characterization of the rHA protein antigen was pursued to identify the potential causes and mechanisms of this potency loss. In addition, the biophysical and chemical stability of the rHA in different formulations and storage conditions was evaluated over time. Results demonstrate that the potency loss over time did not correlate with trends in changes to the higher order structure or hydrodynamic size of the rHA. The most likely mechanism for the early loss of potency was disulfide-mediated cross-linking of rHA, as the formation of non-native disulfide-linked multimers over time correlated well with the observed potency loss. Furthermore, a loss of free thiol content, particularly in specific cysteine residues in the antigen's C-terminus, was correlated with potency loss measured by SRID.

Determination of Cu, As, Hg and Pb in vegetable oils by electrothermal vaporization inductively coupled plasma mass spectrometry with palladium nanoparticles as modifier.

The determination of Cu, As, Hg and Pb in vegetable oils by electrothermal vaporization inductively coupled plasma mass spectrometry (ETV-ICP-MS) was investigated. The oils were injected in the form of emulsions containing 5% m/v vegetable oil, 1.5% v/v Triton X-100 and 50 µg mL(-1) ascorbic acid. Palladium nanoparticles (Pd-NPs) were used as modifier. The interference of (40)Ar(35)Cl(+) at arsenic mass m/z 75 was reduced significantly using dynamic reaction cell (DRC). Standard addition and isotope dilution methods were used for the quantifications. The method reported has been applied to the determination of Cu, As, Hg and Pb in selected vegetable oil samples purchased from a local market. The analytical results obtained were in good agreement with those of digested samples analyzed by pneumatic nebulization ICP-MS with 95% confidence according to Student t-test (except for Cu). Precision between sample replicates was better than 10% with the ETV-ICP-MS method. The detection limits obtained from standard addition curves were 0.4, 0.5, 1.1 and 0.4 ng g(-1) for Cu, As, Hg and Pb, respectively, in the original oil samples.

Bioassays against pinewood nematode: assessment of a suitable dilution agent and screening for bioactive essential oils.

Acetone was investigated and found to be an appropriate alternative to Triton X-100 as a solvent of essential oils in bioassays aimed to investigate their effects on pinewood nematode (Bursaphelenchus xylophilus) mortality. Therefore it was used as dilution agent to screen the effectiveness of fifty two essential oils against this pest. Thirteen essential oils were highly effective, resulting in more than 90% pinewood nematode mortality at 2 mg/mL, with six of them resulting in 100% mortality. LC100 values ranged between 0.50 mg/mL and 0.83 mg/mL for the essential oils of Origanum vulgare and Satureja montana, respectively. Essential oils were submitted to gas chromatography and gas chromatography-mass spectrometry analysis and their chemical composition established. Data from essential oils with 100% mortality at 2 mg/mL and other essential oils previously found to have LC100 ≤ 2 mg/mL was combined, their chemical profiles investigated by correspondences analysis plus automatic classification.

Realization of the reversible vesicle-micelle transition of vitamin-derived bolaamphiphiles by heat change monitoring.

The real-time energetics involved in the structural change of a zwitterionic vitamin-derived bolaamphiphiles (DDO) vesicles, which were induced by conventional surfactants, such as hexadecyltrimethylammonium bromide (CTAB), sodium dodecyl sulfate (SDS), and Triton X-100 (TX100), was characterized by isothermal titration calorimetry (ITC). Interactions of both CTAB and SDS with DDO were accompanied with considerable heat release whereas the interaction energetics between TX-100 and the vesicles were small. However, the transition of DDO vesicles to micelles did occur upon the addition of all of the three surfactants. Fine inflection points were observed in heat flow enthalpograms, which indicated systematically the change of vesicle structure. By monitoring the interaction of CTAB with DDO, we found that heat release kept constant over a certain concentration range at higher temperatures. The repairing effect of heating was revealed and a reversible transition from micelles to vesicles of DDO was thus realized. Further encapsulation of fluorescein in DDO vesicles proved that the reversible vesicle-micelle transition was controllable. This research demonstrates that ITC combined with complementary analytical methods such as dynamic light scattering (DLS) and transmission electron microscopy (TEM) helps to get the real-time information of the structural changes of vesicles. It also shows that these synthetic novel bolaamphiphiles offer great promise for designing controllable release system.

The mechanism of antibacterial activity of tetrandrine against Staphylococcus aureus.

Tetrandrine (TET) is a bis-benzylisoquinoline alkaloid derived from the radix of Stephania tetrandra S. Moore. TET performs a wide spectrum of biological activities. The radix of S. tetrandrae has been used traditionally in Asia, including Korea, to treat congestive circulatory disorders and inflammatory diseases. The aim of this study was to examine the mechanism of antibacterial activity of tetrandrine against Staphylococcus aureus. The mechanism was investigated by studying the effects of TET in combination with detergent or membrane potential un-couplers. In addition, the direct involvement of peptidoglycan (PGN) was assessed in titration assays. TET activity against S. aureus was 125-250 µg/mL, and the minimum inhibitory concentration (MIC) of the two reference strains was 250 µg/mL. The OD(600) of each suspension treated with a combination of ethylenediaminetetraacetic acid (EDTA), tris(hydroxymethyl) aminomethane (TRIS), and Triton X-100 (TX) with TET (0.25×MIC) had been reduced from 43% to 96%. Additional structure-function studies on the antibacterial activity of TET in combination with other agents may lead to the discovery of more effective antibacterial agents.

Investigation of surfactant/cosurfactant synergism impact on ibuprofen solubilization capacity and drug release characteristics of nonionic microemulsions.

The current study investigates the performances of the multicomponent mixtures of nonionic surfactants regarding the microemulsion stabilisation, drug solubilization and in vitro drug release kinetic. The primary surfactant was PEG-8 caprylic/capric glycerides (Labrasol). The cosurfactants were commercially available mixtures of octoxynol-12 and polysorbate 20 without or with the addition of PEG-40 hydrogenated castor oil (Solubilisant gamma 2421 and Solubilisant gamma 2429, respectively). The oil phase of microemulsions was isopropyl myristate. Phase behaviour study of the pseudo-ternary systems Labrasol/cosurfactant/oil/water at surfactant-to-cosurfactant weight ratios (K(m)) 40:60, 50:50 and 60:40, revealed a strong synergism in the investigated tensides mixtures for stabilisation of microemulsions containing up to 80% (w/w) of water phase at surfactant +cosurfactant-to-oil weight ratio (SCoS/O) 90:10. Solubilization of a model drug ibuprofen in concentration common for topical application (5%, w/w) was achieved at the water contents below 50% (w/w). Drug free and ibuprofen-loaded microemulsions M1-M6, containing 45% (w/w) of water phase, were prepared and characterized by polarized light microscopy, conductivity, pH, rheological and droplet size measurements. In vitro ibuprofen release kinetics from the microemulsions was investigated using paddle-over-enhancer cell method and compared with the commercial 5% (w/w) ibuprofen hydrogel product (Deep Relief, Mentholatum Company Ltd., USA). The investigated microemulsions were isotropic, low viscous Bingham-type liquids with the pH value (4.70-6.61) suitable for topical application. The different efficiency of the tensides mixtures for microemulsion stabilisation was observed, depending on the cosurfactant type and K(m) value. Solubilisant gamma 2429 as well as higher K(m) (i.e., lower relative content of the cosurfactant) provided higher surfactant/cosurfactant synergism. The drug molecules were predominantly solubilized within the interface film. The amount of drug released from the formulations M3 (10.75%, w/w) and M6 (13.45%, w/w) (K(m) 60:40) was limited in comparison with the reference (22.22%, w/w) and follows the Higuchi model. Microemulsions M2 and M5 (K(m) 50:50) gave zero order drug release pattern and ∼15% (w/w) ibuprofen released. The release profiles from microemulsions M1 and M4 (K(m) 40:60) did not fit well with the models used for analysis, although the amounts of ibuprofen released (24.47%, w/w) and 17.99% (w/w), respectively) were comparable to that of the reference hydrogel. The drug release mechanism was related with the surfactant/cosurfactant synergism, thus the lower efficiency of the tensides corresponded to the faster drug release.