Effect of Dextrose in the Internal Aqueous Phase on Formation and Stabiblity of W/O/W Multiple Emulsions

The osmolarity of the internal aqueous phase of W/O/W multiple emulsions was varied by using different concentrations of dextrose in the internal phase. Evaluation of the stability of the emulsions was done by microscopic, viscometric and conductometric methods. Microscopic study indicated that as the dextrose concentration in the internal phase increased (0 - 2.50% W/V), the stability, in terms of coalescence of the internal droplets and rupture of the interfacial oily layer, increased from 12 hrs to 7-8 weeks. Viscometric evaluation showed the emulsions to exhibit Non-Newtonian flow and the apparent viscosities of freshly prepared emulsions increased from 8000 to 56,000 cps as the dextrose concentration was increased; the viscosity decreased as the emulsion aged. The amount of drug released as determined by the conductometric method, correlated with the viscosity and stability of the emulsions. The reduction of globule size of the primary (W/O) phase by use of a colloid mill increased the apparent viscosity significantly and thus improved the stability of the formulations.     

Effect of non-ionic surfactant concentration and type on the formation and stability of W/O/W multiple emulsions: Microscopic and conductometric evaluations

Abstract

W/O/W multiple emulsions with sodium salicylate as a model drug were prepared and evaluated for the effect of surfactant concentration and type on stability using microscopic and conductometric methods. Primary (W/O) emulsions were prepared with lipophilic surfactants (2-31% W/W relative to the oily phase). W/O/W emulsions were formed by mixing the primary emulsions with solutions containing 0.5 to 2% W/V hydrophilic surfactants. Optimum concentration of the lipophilic surfactant was 26% W/W. The optimum hydrophilic surfactant concentration was 1% W/V. Best stability was achieved with HLB 3.7 lipophilic and HLB 15.6 hydrophilic surfactants.     

Effect of non-ionic surfactant concentration and type on the formation and stability of W/O/W multiple emulsions: Microscopic and conductometric evaluations

W/O/W multiple emulsions with sodium salicylate as a model drug were prepared and evaluated for the effect of surfactant concentration and type on stability using microscopic and conductometric methods. Primary (W/O) emulsions were prepared with lipophilic surfactants (2-31% W/W relative to the oily phase). W/O/W emulsions were formed by mixing the primary emulsions with solutions containing 0.5 to 2% W/V hydrophilic surfactants. Optimum concentration of the lipophilic surfactant was 26% W/W. The optimum hydrophilic surfactant concentration was 1% W/V. Best stability was achieved with HLB 3.7 lipophilic and HLB 15.6 hydrophilic surfactants.     

Simple and straightforward determination of the enclosed water volume fraction of W/O/W double emulsions by analytical photocentrifugation

ABSTRACT

During the preparation of W/O/W-type double emulsions, a part of the internal water phase is often released to the external water phase. Thus, it is important that the enclosed water volume fraction can be determined in a simple and straightforward manner after preparation. In this work, a method is developed to determine the enclosed water volume fraction of W/O/W-type double emulsions using analytical photocentrifugation after which the results are compared to the enclosed water volume fraction as determined using pulsed field gradient Nuclear Magnetic Resonance (NMR). From the results, it can be concluded that analytical photocentrifugation is indeed a simple and straightforward method to determine the enclosed water volume fraction of double emulsions.     

Prolonged Tissue Levels of Pentazocine from Multiple W/O/W EMULSIONS IN MICE

Abstract

Multiple W/O/W emulsions containing pentazocine were prepared and tested in virto and in viro. The in viro results indicated a well controlled and higher drug release from teh W/O/W emulsions than the W/O emulsion. The in vivo data showed prolonged tissue levels of pentazocine after oral administration of W/O/W emulsions than the W/O emulsion to mice in comparison to acquenous drug solution and W/O emulsion.     

Dynamic-mechanical thermoanalysis test: a rapid alternative for accelerated freeze-thaw stability evaluation of W/O emulsions

Abstract

Objective: The aim of this study was to develop a new dynamic-mechanical thermoanalysis (DMTA) test and evaluate its performance as rapid rheological alternative to routinely used freeze-thaw test for accelerated stability testing of water-in-oil (W/O) emulsions.

Significance: Due to inherent emulsion instability and versatilities of storage and use conditions, stability assessment of emulsion products still remains complex and challenging task. Recommended stability evaluation protocols are time-consuming, imposing need for alternate test procedures, especially in the early stage of product development, as well as in the quality assurance setting, including quality control.

Methods: Five model W/O emulsions were prepared, comprehensively rheologically characterized (continual and oscillatory tests), and subjected to stability evaluation through freeze-thaw test in stability chamber and DMTA tests using an air-bearing rheometer.

Results: Analyzed emulsions displayed desired shear-thinning flow behavior with yield point. The storage modulus dominated over the loss modulus in the linear viscoelastic regions of amplitude sweeps, as was the case in frequency sweeps over entire frequency range. Statistical comparison showed good agreement between freeze-thaw test, as a method available and used in daily routine work for accelerated evaluation of the physical stability, and DMTA test, as a rheological simulation of the said routine method. Duration of DMTA test was significantly shorter compared to routine but lengthy freeze-thaw test (3.5?h versus 12?days).

Conclusions: According to our results, DMTA test could be a rapid alternative for accelerated freeze-thaw stability evaluation of W/O emulsions, thus enabling high formulating turnover and decision making in R&D and QC departments.     

Stability Study of W/O/W Viscosified Multiple Emulsions

Stable multiple emulsions with a small proportion of primary emulsion containing different viscosifying agents in the outer aqueous phase were formulated. The multiple systems were assessed by evaluating several parameters, such as the macroscopic aspect, droplet size, release rate, and accelerated stability under elevated temperatures. The effect of different viscosifying agents at different concentrations on the stability and the multiplicity of the multiple emulsions was examined. The viscosity increased by increasing the concentration of the viscosifying agents. It also appeared that the viscosifying agents increased the temperature stability of the multiple emulsions. As a result, the formulation viscosified with Klucel was more stable, while the one prepared with carbomer viscosified the outer phase at much lower concentrations with much better skin feel.     

Stability study of W/O/W viscosified multiple emulsions

Stable multiple emulsions with a small proportion of primary emulsion containing different viscosifying agents in the outer aqueous phase were formulated. The multiple systems were assessed by evaluating several parameters, such as the macroscopic aspect, droplet size, release rate, and accelerated stability under elevated temperatures. The effect of different viscosifying agents at different concentrations on the stability and the multiplicity of the multiple emulsions was examined. The viscosity increased by increasing the concentration of the viscosifying agents. It also appeared that the viscosifying agents increased the temperature stability of the multiple emulsions. As a result, the formulation viscosified with Klucel was more stable, while the one prepared with carbomer viscosified the outer phase at much lower concentrations with much better skin feel.     

Formulation of Propolis Extract Emulsions. II. O/W Creams Formulated with Self-Emulsifying Bases

Abstract

Propolis extract O/W emulsions, formulated with self-emulsifying bases are prepared. Type and optimal concentration of excipients (bases, consistency agents, solubilising factors) are chosen to obtain stable emulsions with desirable macroscopic properties, satisfactory consistency compatible with cutaneous application, in wound healing.     

Formulation of Propolis Extract Emulsions. I. O/W Creams Based on Non-Ionic Surfactants and Various Consistency Agents

Abstract

The formulation of propolis extract O/W emulsions, a material of therapeutic value in wound healings, is described. Type and optimal concentration of excipients (non ionic surfactants, consistency agents, solubilising factors) are chosen to obtain stable emulsions of desirable macroscopic properties, satisfactory consistency and pH compatible with cutaneous application.     

Prolonged Release of Tegafur from S/O/W Multiple Emulsion

Abstract

To develop a prolonged and sustained release preparation, we prepared an albumin microsphere-in-oil-in-water emulsion (S/O/W) and examined sustained release from it in comparison with other control preparations such as water-in-oil (W/O) emulsions and microspheres in vitro and in vivo, respectively. Tegafur was used as a model drug. A microsphere-in-oil emulsion was prepared by adding albumin microspheres to soybean oil containing 20% Span 80. To prepare an S/O/W emulsion, the microsphere-in-oil emulsion was added into an aqueous solution of hydroxypropyl methylcellulose containing Pluronic F68. The mean particle size of the albumin microspheres was 3 µm, and the ratio of entrapment of tegafur into albumin microspheres was about 25%. In an in vitro release test, the t₇₅ of the S/O/W emulsion was fourfold greater and in an in vivo release test the mean residence time of tegafur from the S/O/W emulsion was more than twofold that from a W/O emulsion or microsphere system. The mean residence time of 5-fluorouracil (5-FU) from an S/O/W emulsion was also greater than with other dosage forms. These results suggest the possible usefulness of an S/O/W emulsion for the sustained and prolonged release of tegafur.     

Physicochemical characterization and in vitro release of salicylic acid from O/W emulsions prepared with Montanov 68: effect of formulation parameters

Montanovs® are surfactants consisting of a combination of alkylpolyglucosides and long chain saturated alcohols. They are used to formulated oil in water (O/W) emulsions where they generate liquid crystals. Emulsions containing 5% Montanov 68® with 40% Lanol 1688® were prepared and salicylic acid (SA) was incorporated at different stages of the O/W emulsion preparation. This study highlights the effects of formulation parameters on the microscopic characteristics, particle size and rheologic properties of Montanov 68® O/W emulsions. Diffusion studies with these emulsions showed the influence of SA incorporation at different steps on the release kinetics. Montanov® enabled the release of SA to be controlled when it was solubilized in the internal phase. The presence of a physical barrier formed by the Montanov® at the interface between the oil and water appeared to modulate the SA passage to the external phase.     

Prolonged Tissue Levels of Pentazocine from Multiple W/O/W EMULSIONS IN MICE

Multiple W/O/W emulsions containing pentazocine were prepared and tested in virto and in viro. The in viro results indicated a well controlled and higher drug release from teh W/O/W emulsions than the W/O emulsion. The in vivo data showed prolonged tissue levels of pentazocine after oral administration of W/O/W emulsions than the W/O emulsion to mice in comparison to acquenous drug solution and W/O emulsion.     

Prolonged release of pentazocine from multiple O/W/O emulsions

Multiple O/W/O emulsions containing pentazocine were prepared and tested in vitro and in vivo. The effect of two different concentrations of three additives, viz. sodium chloride, glucose and glycerol, location of the drug either in one or any two phases of the O/W/O emulsions and pH of the receptor fluid on in vitro release characteristics of the drug was studied. All the parameters influenced the drug release. Multiple O/W/O emulsions gave higher extent of drug release than the simple O/W emulsions. The results of in vivo studies in mice showed prolonged tissue levels of pentazocine from the multiple O/W/O emulsions in comparison to aqueous drug solution and simple O/W emulsion.     

Preparation of spherical SnO2 particles by W/O type emulsion method

An attempt to prepare spherical particles was made using a W/O type emulsion as a reaction field. The effects of surfactant content, W/O ratio and stirring conditions for the preparation of emulsions, which determined the size of water drops in the emulsions, were investigated on the size and morphology of the obtained SnO₂ particles. The size and morphology of the obtained particles were largely influenced by a water/surfactant molar ratio (R-value) for the preparation of the emulsions. Particles having relatively high sphericity were obtained at an R-value below 1500. In order to obtain mono-sized SnO₂ particles with narrow distributions, R-value should be adjusted to the narrow range from 250 to 500. Spherical SnO₂ particles showing narrow particle size distributions were obtained at W/O ratio of 1/1 and surfactant content of 11.2 × 10^–2 mol/l or 22.4 × 10^–2 mol/l. Furthermore, the particle size and morphology of SnO₂ depended on the revolution rate of an emulsifier for emulsification. Mono-dispersed spherical particles having narrow size distributions formed at revolution rates of 3000 and 4000 rpm. At extremely low and high revolution rate of the emulsifier, particles showing high sphericity were not obtained, but agglomerates of un-spherical fine particles. The interfacial reaction time determined the internal structures of spherical particles. The reaction for short time yielded hollow spherical SnO₂ particles, and the internal structure of the particles became denser with increasing reaction time.     

Development and In Vitro Characterization of Chitosan-based Microspheres for Nasal Delivery of Promethazine

ABSTRACT

Conventional and composed promethazine-loaded microspheres were prepared by spray drying of chitosan solution systems and double water-in-oil-in-water (W/O/W) emulsion systems, respectively. Double emulsions were prepared in two different feed concentrations, with chitosan dissolved in both water phases, and ethylcellulose dissolved in oil phase. Swelling and bioadhesive properties of the microspheres depended on the chitosan content, type and the feed concentration of spray-dried system. Results obtained suggested that better ethylcellulose microcapsules with promethazine in the chitosan matrix were formed when less concentrated emulsion systems were spray-dried. Thus, in case of such a system, with ethylcellulose/chitosan weight ratio of 1:2, prolonged promethazine release was obtained.     

Fabrication of polystyrene hollow spheres in W/O/W multiple emulsions

One mild multiple emulsions was used for the fabrication of hollow polystyrene (PS) spheres. Polystyrene was dissolved in a volatile organic solvent to form the O phase, then an aqueous phase containing a surfactant was transferred into above phase to form an oil-in-water (W_in/O) emulsion, followed by addition of W_in/O emulsion in the external W_out phase, and solvent evaporation. Final product with diameter of 150 μm, surface roughness of 30 nm, and sphericity of 98.0% was obtained. The possible influences on the formation of PS hollow sphere were also discussed.     

Preparation of monodisperse W/O emulsions using a stainless-steel microchannel emulsification chip

In this study, hydrophobically treated stainless-steel microchannel (MC) array chips were used for preparing monodisperse W/O emulsions. A water-saturated decane containing 5?wt% tetraglycerin monolaurate condensed ricinoleic acid ester was used as the continuous phase. A Milli-Q water containing 5?wt% polyethylene glycol (molecular weight 20,000) and 5?wt% NaCl was used as the dispersed phase. The stainless-steel MC array chips used for MC emulsification had a sufficiently high contact angle of the dispersed phase to their surface in the continuous phase. The resultant uniform-sized aqueous droplets with a coefficient of variation of <5% had average diameters of 100–300?µm, depending on the MC cross-sectional size. The maximum productivity of uniform-sized aqueous droplets reached higher than 1?mL?h^?1. The difference in the critical capillary number of the dispersed phase that flows in a 100-µm depth MC was 1.5 times greater than that in a 30-µm depth MC.     

Thermal stability of the engineered interfaces in Wf/W composites

Application of tungsten as a structural material is severely restricted due to its inherent brittleness. Recently, a novel toughening method for tungsten was proposed by the authors using tungsten wires as reinforcement. The idea is analogous to the fiber-reinforced ceramic–matrix composites theory which utilizes the internal energy dissipation caused by the debonding and frictional sliding at the fiber/matrix interfaces to absorb strain energy and to redistribute stress concentrations over an extended volume. To maximize the energy dissipation, the interfaces need to be engineered by coating which can withstand thermal exposure during service. In this work, we studied the thermal stability of various interfacial coatings after heat treatment. Microstructural change and the effect on mechanical properties were investigated by means of electron microscopy and fiber push-out tests. The results show that the microstructural phases of the analyzed interfaces remained relatively stable under thermal exposure of 800 °C for 10 h. Under such thermal exposure, the fracture energy of the Er/W multilayer and the ZrO _x /Zr multilayer were affected by less than 10%, while it was increased by 40% for the ZrO _x /W bilayer. The fracture energy of the C/W dual layer was decreased by a factor of 4, whereas for the Cu/W multilayer case it was increased by a factor of 2.     

Formulation of Propolis Extract Emulsions. II. O/W Creams Formulated with Self-Emulsifying Bases

Propolis extract O/W emulsions, formulated with self-emulsifying bases are prepared. Type and optimal concentration of excipients (bases, consistency agents, solubilising factors) are chosen to obtain stable emulsions with desirable macroscopic properties, satisfactory consistency compatible with cutaneous application, in wound healing.