Study on high performance ice slurry formed by cooling emulsion in ice storage (discussion on adaptability of emulsion to thermal storage material)

This study focuses on an emulsion as a new thermal storage material for ice storage. Two types of emulsions were formed using an oil–water mixture with a small amount of additive. A silicone, light and lump oils were used. The water contents of the emulsions were 70, 80 and 90%. The additive was an amino group modified silicone oil. No depression of freezing point was observed for the emulsions because of their hydrophobic properties. In order to determine the structure of the emulsions, their electrical resistances were measured. Moreover, components of the liquids separating from the emulsions were analyzed. The results indicated that one emulsion was a W/O type emulsion, while the other was an O/W type. Finally, adaptability of the two emulsions to ice storage was discussed, it was concluded that a high performance ice slurry could be formed by the W/O type emulsion.     

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.     

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

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.     

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

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.     

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 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.     

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.     

Development and in vitro characterization of chitosan-based microspheres for nasal delivery of promethazine

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.     

The effect of additives on the treatment of oil-in-water emulsions by vacuum evaporation

A simple batch vacuum evaporation process for the treatment of several oil-in-water (O/W) emulsions is reported. The experiments were carried out with waste emulsions from an industrial copper rolling process and with model emulsions prepared in the laboratory. No detailed information on the formulation of the industrial waste O/W emulsions was available. Several model emulsions were formulated using the same base oil (an 85–15% (w/w) mixture of a synthetic poly-α-olefin and a trimethylol propane trioleate ester, respectively) and one of the three following surfactants: Brij-76 (polyethylene glycol octadecyl ether, non-ionic), CTAB (hexadecyltrimethyl ammonium bromide, cationic), and Oleth-10 (glycolic acid ethoxylate oleyl ether, anionic). Experimental results show a strong influence of operating conditions, such as pressure or bath temperature, on the evaporation performance. As a general trend, the higher the values of these parameters, the higher the pollutant content in the obtained aqueous effluent. The presence of surfactants increase the evaporation rate, especially at low operating vacuum pressures, the solubility of oil molecules in water and the evaporation temperature of model O/W emulsions. Furthermore, COD reductions higher than 99.5% for the treated waste O/W emulsions were achieved.     

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

Abstract

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.     

A Robust Switchable Oil-In-Water Emulsion Stabilized by Electrostatic Repulsions between Surfactant and Similarly Charged Carbon Dots

How to control the stability of oil-in-water (O/W) emulsions is one of the main topics for scientists working in colloidal systems. Recently, carbon dots (CDs) have received great interest as smart materials because of their excellent physicochemical properties and versatile applications. Herein, for the first time, advanced and switchable O/W emulsions are presented that are stabilized by the synergistic effect of cationic surfactant cetyltrimethylammonium bromide CTAB (emulsifier) and similarly charged CDs (stabilizer). In the formulated emulsion, the cationic surfactant molecules are adsorbed at the oil and water interface to decrease the interfacial tension and enrich the drops with a positive charge to ensure intensive electrostatic repulsions among them. On the contrary, cationic CDs are distributed in the water phase among the droplets to reduce the water secretion and prevent flocculation and droplet coalescence. The stabilizing effect is found to be universal for emulsions of a range of oil phases. Furthermore, the formulated emulsion is found to be switchable between “stable” and “unstable” modes by adding an equivalent of anionic surfactant sodium dodecyl benzene sulphonate (SDBS). The stabilized and switchable O/W emulsions are believed to have wide practical applications in water purification, pharmaceuticals, protein recognition, as well as catalysis.     

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.     

Solid emulsion gel as a novel construct for topical applications: synthesis, morphology and mechanical properties

A series of the solid emulsion gels with the oil volume fraction in the range of 0–50% were synthesized through a polycondensation reaction between activated p-nitrophenyl carbonate poly(ethylene glycol) and protein-stabilized oil-in-water emulsions. The resultant structures were investigated in terms of swelling behavior, composition, morphology, mechanical and skin hydration properties. Solid emulsions gels share the properties of both hydrogel and emulsion. Similar to the classical hydrogel, the SEG swells in water up to equilibrium swelling degree, which decreases as the oil volume fraction increases, and comprises immobilized drops of protein-stabilized oil. The impregnation of the oil phase is found to reduce tensile stiffness of the material, but improves material’s extensibility. The mechanical properties of the constructs (Young moduli in the range of 9–15 kPa and the elongation at break of 120–220%) are interpreted according to the “rule of elasticity mixture” that considers the elasticity of the composite material to be a sum of the contributions from individual components, i.e. hydrogel and dispersed oil drops. An idealized model that takes into account the history of the material preparation has been proposed to explain the improved extensibility of the constructs. The results of the mechanical tests, equilibrium swelling, and the skin hydration effect of the solid emulsion gels in vivo are discussed from the perspective of the biomedical applications of the solid emulsion gels, in particular, for the transdermal delivery of hydrophilic and lipophilic drugs.     

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.     

Agglomeration control of hydroxyapatite nano-crystals grown in phase-separated microenvironments

Materials synthesis processes that require high temperatures consume large quantities of energy that generate an environmental burden. We attempted to synthesize hydroxyapatite (HAp) nano-crystals without firing or melting. “Water in oil” (W/O) emulsions were employed as microreactors for HAp formation. The surfactant-bounded water mediated HAp crystal nucleation, and HAp nano-crystallites were obtained. The obtained particles were aggregates composed of plate-like nano-crystals and monodisperse tiny crystals. Utilization of the W/O emulsions resulted in tunable nucleation frequency and the reactant provision, and yielded HAp nano-crystals with characteristic agglomeration properties.     

Microwave-assisted sol–gel process for production of spherical mesoporous silica materials

Spherical mesoporous SiO₂ and SiO₂–TiO₂ particles were synthesized by sol–gel method using W/O emulsion under microwave irradiation. In SiO₂ system, W/O emulsion was prepared by mixing partially hydrolyzed Si(OC₂H₅)₄ aqueous solution including C₁₈TAC as template with n-hexane solution including polyglycerol polyricinalate as emulsifier. In SiO₂–TiO₂ system, Ti(OC₂H₅)₄ capped by acetylacetone was added to the aqueous phase. In both cases, spherical products were synthesized by heating of W/O emulsion for 30 min under microwave irradiation. The specific surface area and pore size of spherical products were 800 m²/g and 1.6 nm, respectively, which indicates that the spherical products are mesoporous. These results suggest that sol–gel reaction in water phase proceeds rapidly because microwave quickly and selectively heats up the aqueous solution.     

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.     

Formation of high performance ice slurry by W/O emulsion in ice storage (effective method to propagate supercooling dissolution)

This study focused ice slurry formation in an ice storage system using W/O emulsions with 70 and 80% water contents. Emulsions consisted of a silicone oil–water mixture with a small amount of amino-group-modified silicone oil additive. Ice slurry was formed by cooling the emulsion without ice adhesion to the cooling wall, as water in the emulsion did not directly contact the cooling wall. As the structure of W/O emulsion slowed the propagation rate of supercooling dissolution, voltage and ultrasonic wave were applied to the W/O emulsion to propagate dissolution more quickly and decrease maximum supercooling degree, respectively. Thus, the effects of voltage and ultrasonic wave applications on propagation rate were clarified.