Types Of Microemulsions Research Articles

Development and pharmacokinetic evaluation of erythromycin lipidic formulations for oral administration in rainbow trout ( Oncorhynchus mykiss)

The aim of this work was to enhance the bioavailability of erythromycin base when administered orally in rainbow trout ( Oncorhynchus mykiss). Since erythromycin is normally given in the form of medicated feed, in this study three new types of feed formulation were developed. A self-emulsifying system and two types of double microemulsions (O/W/O) were prepared, characterized and adsorbed on a commercial extruded diet for fish. The emulsified systems were based on saturated polyglycolized glycerides and mono- and diglycerides of medium-chain fatty acids (as oily phase), Tween® 80 (as surfactant) and, in the case of double microemulsions, distilled water. The systems differed in percentage composition and for the amount and position of erythromycin in different phases. The three medicated feed were then administered orally by means of a gastric probe to rainbow trout and their relative bioavailability was estimated in comparison with that obtained after oral administration of feed with erythromycin powder. For each medicated feed, 80 fish were tested. Finally, plasma profiles of erythromycin after single administration of medicated feeds were used to predict profiles obtainable by administering once-daily medicated feeds for 7 consecutive days. The results proved that the feeds containing microemulsified erythromycin provided largely superior oral bioavailability and the advantage of obtaining the same efficacy against bacterial infections with a much lower dose of drug.

Enhanced skin delivery of polyphenols by microemulsion and prevention against UV irradiation-induced erythema formation

Polyphenols have been applied for topical purposes such as photoprotection against UV-induced skin damage. However, intradermal delivery of most polyphenols is inefficient. To improve the efficiency, we tried to clarify the usefulness of microemulsion using excised guinea pig dorsal skin and Yucatan micropig skin. We used two types of microemulsions consisting of isopropyl myristate (IPM), 150 mM NaCl solution, Tween 80 and ethanol. Weight ratio of IPM, 150 mM NaCl solution, Tween 80 and ethanol was 8:25:20:47 in microemulsion A, and 33:7:30:30 in microemulsion D. By using these microemulsions solubility and skin delivery of polyphenols such as genistein and chlorogenic acid were markedly improved. For example, solubility of genistein in 150 mM NaCl was only 0.059 mM, it increased to 80 mM in o/w-type microemulsion A, and further increased to 140 mM in w/o-type microemulsion D. Skin delivery of genistein also increased 36 times using microemulsion A and further increased about 60 times using microemulsion D at saturated concentration. On the other hand, enhancement effect of microemulsion A was larger than that of microemulsion D for skin accumulation of hydrophilic chlorogenic acid. Genistein and chlorogenic acid retained in the skin significantly inhibited lipid peroxidation dose-dependently in vitro. When genistein was applied with microemulsion D at saturated concentration (140 mM), lipid peroxidation tested by ammonium iron (II) sulfate and sodium citrate decreased to less than 10%. We furthermore revealed that pretreatment of guinea pig dorsal skin with microemulsion gel which contains either genistein or chlorogenic acid prevented UV-irradiation-induced erythema formation. These findings revealed the potential use of microemulsion for the delivery of these polyphenols to protect skin against UV-irradiation-induced damage.

A new type of microemulsion consisting of two halogen-free ionic liquids and one oil component

A ternary system consisting of toluene, as oil phase, and two ionic liquids, i.e., 1-butyl-3-methylimidazolium octylsulfate (bmimOctOSO 3) and 1-ethyl-3-methylimidazolium ethylsulfate (emimEtOSO 3), has been investigated. The isotropic phase region was studied by means of conductometric, cyclic voltammetric and rheological measurements. The results show that microemulsions can be formed, where the bmimOctOSO 3 take over the role of a surfactant in the spontaneous interfacial film formation process. Changes in the droplet–droplet exchange process can be assigned to transitions in the microstructure of the system from the IL-in-oil to oil-in-IL microemulsions, passing a bicontinuous phase. In the region between 5 wt.% and 21 wt.% of emimEtOSO 3, reverse microemulsions with a droplet size of 2–10 nm were detected using Dynamic Light Scattering (DLS) and Cryo-Scanning Electron Microscopy (Cryo-SEM).

Effect of Alkyl Sulfate on the Phase Behavior of Microemulsions Stabilized with Monoacylglycerols

AbstractIn this study the effect of an anionic surfactant (sodium dodecyl sulfate SDS) and oils (hydrocarbons: C12–C16) on the formation and phase behavior of the systems of oil/monoacylglycerols (MAG):SDS/propylene glycol/water has been 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). Electrical conductivity measurement, FT‐IR spectroscopy and differential scanning calorimetry methods were applied to determine the structure and type of the microemulsions formed. The dimension of microemulsion droplets was characterized by dynamic light scattering. It has been stated that the concentration of SDS has a strong influence on the shape and extent of the microemulsion areas. Addition of an ionic surfactant to the mixture with MAG promotes an increase in the area of microemulsion formation in the phase diagrams, and these areas of the isotropic region change with the temperature. It was shown that the presence in the systems of a surfactant more hydrophilic than MAG caused an increase in water content in the microemulsions. It was found that, depending on temperature and concentration of the surfactant mixture, it was possible to obtain a W/O type microemulsion with a dispersed particles size distribution ranging from 20 to 50 nm and containing about 17–38% water in the system. Among different alkanes (from C12 to C16), hexadecane embedded microemulsions showed a maximum water solubilization capacity.

Stripping of nonionic surfactants from the coacervate phase of cloud point system for lipase separation by Winsor II microemulsion extraction with the direct addition of alcohols

Extractive microbial fermentation of lipase by Serratia marcescens ECU1010 in cloud point system was previously carried out in the cloud point system. The direct addition of different alcohols, including iso-butanol, 2-phenylethanol and 1-octanol, into the coacervate phase of the clear supernatant of the fermentation broth formed microemulsion, where the nonionic surfactants and lipase were unevenly partitioned between the different phases in the microemulsion system. The polarity of alcohols strongly affected the microemulsion type at room temperature condition. The results indicated that the Winsor II microemulsion, formed by the addition of iso-butanol or 2-phenylethanol as the organic solvent, favored the stripping of the nonionic surfactant into the O m phase, whereas the lipase was left in the excess aqueous phase. However, the Winsor I microemulsion, formed by the addition of 1-octanol as the organic solvent, failed to separate the lipase from the nonionic surfactant in the coacervate phase of cloud point system, because the nonionic surfactant and lipase were partitioned into the W m phase at the same time. Moreover, in the Winsor II microemulsion extraction with 2-phenylethanol as the organic solvent, in which case the protein–surfactant complexes were absent at the interface between the O m phase and the excess aqueous phase, the high lipase recovery (above 80%) and good nonionic surfactant removal were achieved. The effect of nonionic surfactants on lipase activity was also presented.

Enhanced Skin Delivery of Genistein and Other Two Isoflavones by Microemulsion and Prevention against UV Irradiation-Induced Erythema Formation

To improve the efficiency of the intradermal delivery of genistein and other two isoflavones (daidzein and biochanin A), we tried to clarify the usefulness of microemulsion by in vitro study on excised guinea pig dorsal skin and Yucatan micropig skin. Using microemulsion consisting of isopropyl myristate (IPM), 150 mM NaCl solution, Tween 80 and ethanol as a vehicle, the solubility of all the isoflavones markedly increased and significant amounts of isoflavones were delivered to the skin. The effect of water-in-oil (w/o)-type microemulsion D was larger than that of oil-in-water (o/w)-type microemulsion A. Among three isoflavones tested, the increase of genistein was most marked on both solubility and skin accumulation. Genistein retained in the skin significantly inhibited lipid peroxidation in vitro dose-dependently. Furthermore, pretreatment of guinea pig dorsal skin with genistein containing gel-like microemulsion D prevented UV irradiation-induced erythema formation. These findings indicate the potential use of w/o-type microemulsion for the delivery of genistein to protect skin against UV-induced oxidative damage.

Formation of organically and inorganically passivated CdS nanoparticles in reverse microemulsions

This paper is focused on the formation of organically and inorganically passivated cadmium sulfide (CdS) nanoparticles in two different types of microemulsions. On the one hand, we used a ternary inverse microemulsion consisting of water, heptanol, and 3-(N,N-dimethyldodecylammonio)propanesulfonate and on the other hand, a poly(ethyleneimine)-based quaternary microemulsion containing water, toluene, pentanol, and sodium dodecylsulfate. UV-vis measurements confirm the formation of CdS-ZnS core-shell nanoparticles in the ternary microemulsion. Using the quaternary microemulsion template phase, polymer capped luminescent CdS nanoparticles can be formed. After a complete solvent evaporation, the nanoparticles are redispersed in water and characterized by means of dynamic light scattering and transmission electron microscopy. From the ternary microemulsion, well-stabilized CdS-ZnS core-shell nanoparticles with diameters of about 5 nm can be redispersed, but from the quaternary microemulsion, only nanoparticle aggregates of about 100 nm.

Different Kinetic Behaviors for Unimolecular and Bimolecular Ester Hydrolysis Reactions in Strongly Acidic Microemulsions

Replacing the counterion in sodium bis(2-ethylhexyl)sulfosuccinate with H(+) allows strongly acidic microemulsions to be obtained. These systems are the only known colloidal medium in which it is possible to reach local concentrations of acid, expressed as Hammett acidity function (H(0)), lower than H(0) = -0.2, which corresponds to a concentration of acid above 1 M in aqueous solution. In the present work, there has been analyzed the influence of this type of microemulsion on the acid hydrolysis of two esters derived from picolinic acid: 4-nitrophenylpicolinate (NPP) and 2,4-dinitrophenylpicolinate (DNPP). The reaction rate for NPP and DNPP increases up to 16 times on increasing the size of the aqueous nanocore of the microemulsion, which supposes an experimental behavior opposed to the one observed for the hydrolysis of nitrophenylacetate (NPA). The key to this differentiated behavior of NPP and DNPP resides in the fact that the rate-determining step for the acid hydrolysis mechanism is the water addition to the protonated ester. The reaction rate increases on increasing the nucleophilicity of water; that is, on increasing W (W = [H(2)O]/[surfactant]). Therefore, the acid hydrolysis of esters in strongly acidic microemulsions presents an A2 mechanism when reactivity increases with W, and an A1 mechanism if it decreases with W.

Phase behavior and microstructure of the system consisting of 1-butyl-3-methylimidazolium hexafluorophosphate, water, triblock copolymer F127 and short-chain alcohols

The phase behavior and microstructure of the system consisting of ionic liquid BmimPF 6, copolymer F127, H 2O and short-chain alcohols including ethanol, n-propanol or n-butanol were investigated at 30 °C. Large areas of single-phase microemulsion were observed in all the three systems. Specially, lyotropic liquid crystal appeared in the n-butanol system while it disappeared when the other two alcohols were used. The water-in-BmimPF 6, bicontinuous, and BmimPF 6-in-water regions of the microemulsions were identified by the usual electrical conductivity measurement. As an attempt, UV–vis spectroscopy was successfully used to distinguish different type of microemulsions using methyl orange as solvatochromic probe. Furthermore, dynamic light scattering (DLS) measurements were also skillfully introduced to vividly track the structural variation of different microemulsions. On the other hand, the hydrodynamic diameter of the BmimPF 6-in-water microemulsion was accurately obtained. An unusual phenomenon was demonstrated that Z-average size of BmimPF 6-in-water microemulsions decreases with increasing BmimPF 6 (oil) concentration at fixed (F127 + n-propanol) concentration.

Microemulsion flooding for enhanced oil recovery

Petroleum recovery methods basically consist of fluid injection aiming to displace the oil out of the rock pores. Among the methods used in enhanced oil recovery, chemical methods, which may involve microemulsion flooding, are cited. In this work, injection assays have been carried out with two types of microemulsion: one was prepared with a commercial surfactant (MCS) and another contained a surfactant synthesized in laboratory (MLS). The experiments basically consisted of the injection of fluids into cylindrical plug samples from the Assu Formation (RN, Brazil). During the microemulsion flooding, samples were collected as a function of time and the mass of oil recovered by the microemulsion was determined. From the results obtained, one could conclude that the use of microemulsion prepared with the commercial MCS allowed for recovery indices as high as 87.5%, whilst the use of the MLS microemulsion permitted recovery indices as high as 78.7%. This was mainly due to the difference in viscosity between the two microemulsions used.

Extraction of water miscible organic dyes by reverse micelles of alkyl glucosides

The extraction of methyl orange or methylene blue from an aqueous phase to an organic phase of reverse micelles of alkyl glucosides was investigated. Dodecyl glucoside, a biodegradable and biocompatible surfactant, was employed as a kind of alkyl glucosides, since a stable Winsor II system consisting of the water-in-oil type microemulsion and aqueous phases was formed when an organic solution containing dodecyl glucoside was contacted with an aqueous solution. The water content in the reverse micellar organic phase increased with an increase in the concentration of dodecyl glucoside. The extraction ratio of dyes also increased with increasing the concentration of dodecyl glucoside. Furthermore, the extraction ratio of dyes was dramatically dependent upon the pH of an aqueous phase and temperature.

Catalytic hydrogenation of dimethyl itaconate in non-ionic microemulsions: influence of the size of micelle

The structural dimensions of two different microemulsions were extracted and correlated with the catalytic hydrogenation of dimethyl itaconate (DMI) performed in such media using the water-soluble catalyst complex Rh–TPPTS. The commercial, polyoxyethylene-based non-ionic surfactants Igepal CA-520 and Triton X-100 were used to obtain two different types of microemulsions with cyclohexane and water; pentanol as a cosurfactant was added to the Triton system. Dynamic light scattering (DLS) and small angle neutron scattering (SANS) measurements were used to determine the characteristic sizes of the Igepal and Triton microemulsions, respectively, showing a linear dependence between the initial hydrogenation rate of DMI and the radius of the micelles. The initial hydrogenation rate of DMI in bulk water is exceeded in both microemulsions. Indications of deformation of the originally spherical Triton X-100 reverse micelles upon addition of the water-soluble catalyst complex Rh–TPPTS were found.

Development of Novel Multifunctional Cosmetic Raw Materials and Their Applications. IV. The Effect of Structure of Polyoxyethylene / Polyoxypropylene Derivative on the Self-organizing Structures of Surfactants

In this study, the effect of a random copolymer of polyoxyethylene (POE, 38 mol)/polyoxypropylene (POP, 10 mol) pentaerythrytol tetramethyl ether [PEPTME (38/10)], which is unable to form a self-organizing structure on account of its bulkiness, on the microemulsion phase was examined. The phase diagram of the liquid paraffin - nonionic surfactant+PEPTME (38/10) - water system was compared with that of polyoxyethylene (POE)/polyoxypropylene (POP) dimethyl ether (EPDME) system which has a straight-chain structure. In the previous study, the authors reported that a special droplet type microemulsion (highly concentrated microemulsion) was formed, when EPDME was distributed in the hydrophilic moiety of a surfactant in a lamellar liquid crystalline phase. In contrast, it was found that the use of PEPTME (38/10) resulted in disappearance of lamellar as well as hexagonal and cubic liquid crystals, and the formation of an optically isotropic and fluid phase owing to the relationship between the original microemulsion phase and the highly concentrated microemulsion phase. Thus, PEPTME (38/10) was considered to be most suited for preparing highly concentrated microemulsions.

Monte Carlo Simulation of Microemulsion Phase Transitions by Solvent Accessible Surface Area

AbstractResults of lattice Monte Carlo simulation are presented for the behavior of a mixture of oil‐water‐amphiphile in different conditions. For the first time, the phase transitions between different types of microemulsion are modeled, in a qualitative manner, using the concept of solvent accessible surface area. All of the simulations are run in canonical (N, V, T) ensemble. Simple cubic lattices with the dimension of 50 have been used to avoid any size or surface effects of the boxes. Periodic boundary conditions and excluded volumes are used to mimic the box of simulation as a bulk of solution. All of the results are in good qualitative agreement with previous theoretical and experimental results.

Evolutionary Artificial Neural Networks as Tools for Predicting the Internal Structure of Microemulsions

The purpose of this study was to predict microemulsion structures by creating two artificial evolutionary neural networks (ANN) combined with a genetic algorithm. The first ANN would be able to determine the type of microemulsion from the desired composition, and the second to determine the type of microemulsion directly from a differential scanning calorimetry (DSC) curve. The algorithms and the structures for each ANN were constructed and programmed in C++ computer language. The ANNs had a feedforward structure with one hidden level and were trained using a genetic algorithm. DSC was used to determine the microemulsion type. The ANNs showed very encouraging accuracy in predicting the microemulsion type from its composition and also directly from the DSC curve. The percentage success, calculated over the tested data, was over 90%. This enabled us, with satisfactory accuracy, to construct several pseudoternary diagrams that could facilitate the selection of the microemulsion composition to obtain the optimal desired drug carrier. The ANN constructed here, enhanced with a genetic algorithm, is an effective tool for predicting the type of microemulsion. These findings provide the basis for reducing research time and development cost for characterizing microemulsion properties. Its application would stimulate the further development of such colloidal drug delivery systems, exploit their advantages and, to a certain extent, avoid their disadvantages.

Study of Microemulsion Polymerization Conditions on the Preparation of “Stimuli” Responsive Copolymer Nanogels of N‐Acryloyl‐N′‐Methyl Piperazine and Methyl Methacrylate

pH responsive copolymer nanogel particles of N‐acryloyl‐N′‐methyl piperazine (AcrNMP) and methyl methacrylate (MMA) were prepared by a suitable oil‐in‐water type microemulsion polymerization. Effect of microemulsion polymerization conditions such as water content, surfactant‐to‐monomer ratio, amount of monomer, and crosslinker content were studied. The nanogel particles showed spherical morphology with narrow size distribution. The nanogels swelled excessively in acidic solutions reaching a diameter of 750 nm and de‐swelled to 350 nm in basic solutions. This pH response to swelling is due to the protonation of N′‐methyl piperazine nitrogen that leads to electrostatic interactions within the nanogel.

Design, development and bioavailability assessment of Oxytetracycline hydrochloride double o/w/o microemulsion formulation

The aim of this research was to improve the oral bioavailability of Oxytetracycline hydrochloride, a broad spectrum antibiotic having poor oral bioavailability, through the formulation of double o/w/o microemulsion systems. The range of compositions forming a clear one-phase region (primary o/w microemulsion) was evaluated through the construction of the ternary diagram and then three different types of double microemulsions were prepared using the two-step technology. The formulations were characterized for droplet size and zeta potential. DSC was used for determining the type of microemulsion and to verify the formation of double microemulsion systems. The physical characterization gave satisfactory results that were compatible with double microemulsion systems. Finally, the pharmacokinetics of microemulsions was evaluated after oral administration on rats and compared to that of an aqueous and an oily solution. Results indicated an oral bioavailability enhancement of 5.7 and 2 times over the aqueous and oily solutions, respectively.

Aerosol OT Microemulsions as Carriers for Transdermal Delivery of Hydrophobic and Hydrophilic Local Anesthetics

The skin permeation enhancement of many kinds of drugs and cosmetic substances by microemulsions has been widely known; however, the correlations between microemulsion microstructures and the efficiency of skin permeation are not fully elucidated. Therefore, the aim of our study was to investigate the influence of microemulsion types on in vitro skin permeation of model hydrophobic drugs and their hydrophilic salts. The microemulsion systems were composed of isopropyl palmitate (IPP), water, a 2:1 w/w mixture of Aerosol OT (AOT) and 1-butanol, and a model drug. The concentrations of surfactant mixture and model drug were maintained at 45% and 1% w/w, respectively. The concentrations of IPP and water were 15% and 39% w/w, respectively, for oil-in-water (o/w) type and vice versa for water-in-oil (w/o) type. The samples were prepared by simple mixing and characterized by visual appearance, pH, refractive index, electrical conductivity, viscosity, and determination of the state of water and IPP in the formulations using differential scanning calorimetry. Transdermal flux of lidocaine, tetracaine, dibucaine, and their respective hydrochloride salts from the drug-loaded AOT-based microemulsions through heat-separated human epidermis was investigated in vitro using modified Franz diffusion cells. The o/w microemulsions resulted in the highest fluxes of the model drugs in base form as compared with the other formulations within the same group of drugs. Moreover, the skin permeation of drug from microemulsions depended on drug molecular structure and interaction between drug and surfactant.

イオン性界面活性剤のHLB制御による環境対応型マイクロエマルション洗浄剤の開発

イオン性界面活性剤のHLB制御による環境対応型マイクロエマルション洗浄剤の開発

Applications of microemulsions in cosmetics

Since microemulsions were discovered approximately six decades ago, their applications in several fields, including cosmetics, have been increased due to their good appearance, thermodynamic stability, high solubilization power, and ease of preparation. In addition, microemulsions can enhance skin permeation of the loaded substances. They are classified into three types: oil-in-water, bicontinuous, and water-in-oil. All types of microemulsions can be formed spontaneously when the ratios of oil, water, and amphiphile in the systems are appropriate. These proper ratios can be found in a microemulsion region of a phase diagram. The efficiency of microemulsions in topical application is related to microemulsion type. Microemulsion characterization needs a combination of the data from several experimental techniques. Numerous applications of cosmetic microemulsions include skin-care, hair-care, and personal-care products for improving the product efficiency and stability. Moreover, new materials have been developed to be used in cosmetic microemulsion formulations for increasing the product efficiency and reducing the toxicity. The aim of this review is to present some basic information of microemulsions and novel applications of microemulsions in cosmetic formulations.