Outer Water Phase Research Articles

Water-in-Oil-in-Water Nanoemulsions Containing Temulawak (Curcuma xanthorriza Roxb) and Red Dragon Fruit (Hylocereus polyrhizus) Extracts.

Hydrophobic curcumin in temulawak extract and hydrophilic betacyanin in red dragon fruit extract are high-value bioactive compounds with extensive applications in functional food. In this study, these extracts were encapsulated in water-in-oil-in-water (w/o/w) nanoemulsions as a delivery system using a two-step high-energy emulsification method. PGPR and Span 20 were used as lipophilic emulsifiers for the primary w/o emulsion. The most stable w/o/w formulation with the least oil phase separation of 5% v/v consisted of w/o emulsion (15% w/w) and Tween 80 (1.5% w/w) as hydrophilic emulsifier. The formulation was characterized by a 189-nm mean droplet diameter, 0.16 polydispersity index, and –32 mV zeta potential. The freeze–thaw stability may be attributed to the combination of low w/o emulsion content and high Tween 80 concentration in the outer water phase of the w/o/w nanoemulsions used in this study. The IC50 values of the nanoemulsion and the red dragon fruit extract were similar. It means that the higher concentration of curcumin in the nanoemulsions and the lower IC50 value of temulawak extract ensured sufficient antioxidant activities of the w/o/w nanoemulsions.

Formulation and in vitro characterization of long-acting PLGA injectable microspheres encapsulating a peptide analog of LHRH

The present study aimed to formulate triptorelin acetate (TA) into poly (D, L-lactic-co-glycolic) acid (PLGA) based injectable sustained-release microspheres (TA-PLGA-MS) by usingdouble emulsion solvent extraction/evaporation (DESE) technique and investigate the effects of various material attributes and process parameters on the quality attributes such as size, shape, surface morphology, encapsulation efficiency (EE) and in vitro release behavior of these microspheres. Variable compositions of the outer water phase, type of the organic solvents, volume ratios of inner water phase to oil phase, PLGA concentrations, and the powers for emulsification in the preparation of the microspheres showed an influence on their quality attributes. An optimal formulation (F-2) obtained from this univariate approach possess an excellent EE value of 63.5% ± 3.4% and an average volumetric particle size of 35.3 ± 1.8 μm. This formulation was further accomplished with different solidification rates assisted by variable incubation temperatures, which exhibited an impact on the shape/surface and inner morphology of the microspheres. The resultant microspheres also displayed different in vitro release patterns. The matrices processed with a high incubation temperature conferred the fastest and the most complete drug release profile over the period of 63 days. Thus, the solidification rate could be identified as one of the critical process parameters that affected the quality of the PLGA based injectable microspheres specifically designed for the prolonged delivery of TA.

Characterization of Antimicrobial Edible Films with Single and Double Emulsions from Clove (Syzygium aromaticum) Oil

Clove oil as a potent antimicrobial agent was added to enhance the properties of edible films. Clove oil was converted to single and double emulsion emulsions for homogenous dispersion in a starch based edible film suspension. Double emulsion was made with two steps emulsification with CaCl2 as inner water phase and guar gum as outer water phase. Single emulsion was prepared similarly without inner water phase. The physico-chemical characteristics and the antimicrobial activity of the of starch-based edible film added with the emulsion were observed. MBC/MFC of clove oil was determined against E. coli, S. aureus, R. stolonifer, and A. niger which gives value of 1.95, 1.46, 0.52, and 0.35 mg/ml respectively. Incorporation of different emulsions on starch-based edible films affect the properties of resulting edible films by increasing thickness, opacity, elongation at break, water vapor transmission rate, and swelling index. Both emulsions showed comparable physicochemical characteristics such as thickness, WVTR, and swelling index value. However, double emulsion produced more superior edible films in terms of tensile strength and antimicrobial activity. 15% addition of double emulsion were able to show strong antimicrobial activity with inhibition zone of more than 8.0 mm for E. coli and 24.0 mm for R. stolonifer.Keywords: clove oil; edible film; single and double emulsion

Effect of Stabilizers on Encapsulation Efficiency and Release Behavior of Exenatide-Loaded PLGA Microsphere Prepared by the W/O/W Solvent Evaporation Method.

The aim of this study was to investigate the effects of various stabilizers on the encapsulation efficiency and release of exenatide-loaded PLGA (poly(lactic-co-glycolic acid)) microspheres prepared by the water-in-oil-in-water (W/O/W) solvent evaporation (SE) method. It was shown that the stabilizers affected exenatide stability in aqueous solutions, at water/dichloromethane interfaces, on PLGA surfaces, or during freeze-thawing and freeze-drying procedures. Sucrose predominantly reduces instability generated during freeze-thawing and freeze-drying. Phenylalanine prevents the destabilization at the water–dichloromethane (DCM) interface through decreased adsorption. Poloxamer 188 enhances stability in aqueous solutions and prevents adsorption to PLGA. Proline and lysine decrease adsorption on PLGA surfaces. Fourier transform infra-red spectroscopy (FT-IR) was used to find the molecular interaction of additives with exenatide or PLGA. Additives used in stability assessments were then added stepwise into the inner or outer water phase of the W/O/W double emulsion, and exenatide-loaded microspheres were prepared using the solvent evaporation method. The effect of each stabilizer on the encapsulation efficiency and release behavior of microspheres correlated well with the stability assessment results, except for the negative effect of poloxamer 188. Particle size analysis using laser diffractometry, scanning electron microscopy (SEM), water vapor sorption analysis, differential scanning calorimetry (DSC), and circular dichroism (CD) spectroscopy were also employed to characterize the prepared exenatide-loaded PLGA microsphere. This study demonstrated that an adequate formulation can be obtained by the study about the effect of stabilizers on peptide stability at the preformulation step. In addition, it can help to overcome various problems that can cause the destabilization of a peptide during the microsphere-manufacturing process and sustained drug release.

Influence of Process Parameters on the Characteristics of Hydrophilic Drug-Loaded Microparticles through Double Emulsion Solvent Evaporation Technique

The purpose of this study was to investigate the influence of process parameters on the characteristics of microparticles using double emulsion solvent evaporation method for encapsulation of hydrophilic drug. Donepezil hydrochloride (DPH), a reversible cholinesterase inhibitor, was selected as a model hydrophilic drug. Prior to conducting an experiment, the target particle size of microparticles was set at approximately 200 μm. The investigated process parameters include pH of outer water phase, stirring time, polymer amount, and volume of outer water phase. The results showed that DPH-loaded microparticles was successfully prepared in two steps. In the first step, the primary emulsion was prepared by dissolving DPH in distilled water before emulsifying in dichloromethane (DCM) containing different amounts of poly(butylmethacrylate-co-2-dimethylaminoethyl-methacrylate-co-methyl-methacrylate) (PBM-DM-MM) using ultrasonic probe. In the second step, the primary emulsion was emulsified in polyvinyl alcohol (PVA) solution by overhead stirrer to prepare double emulsion. After solvent evaporation, the microparticles were collected by centrifugation and washed with distilled water. Based on the statistical analysis, stirring time, polymer amount and volume of outer water phase were the main significant parameters influencing particle size of microparticles.

Properties of double W/O/W emulsions containing vitamin C and E stabilized with gelatin/sodium caseinate complex

Double emulsions are complex liquid dispersion systems in which the droplets of one dispersed liquid are further dispersed in another liquid, producing W/O/W or O/W/O emulsions. W/O/W emulsions are the most studied systems because they have great potential application. However, despite all the advantages, that these systems offer, it is very difficult to obtain stable formulations, and this is the reason for their limited practical application. The use of biopolymers to stabilize double emulsions could give rise to pharmaceutical and food applications. Based on previous studies, appropriate concentrations of gelatin and sodium caseinate (NaCAS) were selected to investigate the possibility of stabilization of double W/O/W emulsions by this system, if they are present in the outer aqueous phase. The investigations showed that interactions between gelatin and NaCAS in the outer water phase, as well as the composition of the mixtures of lipohilic emulsifiers used for the primary W/O emulsions preparation, influences the droplets size and sedimentation stability of double emulsions. The most stable emulsions were obtained at a NaCAS concentration when an insoluble coacervate forms (0.5 mass %) and at concentrations higher then this, when soluble negatively charged complexes adsorb at the oil/water interface.

Progress and challenges in the fabrication of DPS shells for ICF

To improve the quality of deuterated polystyrene (DPS) shells, the synthesis and purification of DPS as well as the fabrication of DPS shells are investigated. The molecular weight and molecular weight distribution, measured by GPC-MALLS, are about 350 kg mol-1 and less than 2.0, respectively. The results of TG and GC-MS indicate that the residual solvent is almost completely removed. DPS shells with ∼ 300 μm –2500 μm diameter and ∼10 μm–100 μm wall thickness are successfully prepared by a microfluidic device. The monodispersity of the diameter is much better than that of the wall thickness in a batch of DPS shells. The vacuoles can be suppressed by both reducing hydrophilic residues in DPS and adding some salts into the outer water phase (W2). The defects appearing during the drying process decrease by heat treatment, ethanol exchange, and lowered drying temperature. The results presented in this work not only provide guidelines for the preparation of DPS shells of better quality, but also indicate challenges for the future.

Microencapsulation of anthocyanins through two-step emulsification and release characteristics during in vitro digestion.

An anthocyanin-rich double emulsion (w/o/w) was prepared via a two-step emulsification method. Anthocyanins from black rice extract were incorporated in the inner water phase and dispersed inside the middle oil phase, which was then dispersed into the outer water phase. Generation of the double emulsion was confirmed by optical microscopic analysis and its microencapsulation efficiency was 99.45 ± 0.24%. An in vitro digestion study was carried out to evaluate anthocyanin concentration changes and release characteristics of the double emulsion using simulated gastrointestinal fluids. After 2 h incubation in the simulated gastric fluid, the percentage of diffused anthocyanins was 3.66 ± 2.32%. These observations indicate that the double emulsion could control the release of anthocyanins in the stomach. During incubation in the simulated intestinal fluid, a total release of anthocyanins in the double emulsion was observed within the first 20 min. A pH-dependent degradation of anthocyanins was also evident.

Investigations on the relationship between interfacial and single droplet experiments to describe instability mechanisms in double emulsions

Due to their multicomponent structure, water-in-oil-in-water (WOW) double emulsions are of great interest for the encapsulation of hydrophilic substances. Although promising applications are reported, few double emulsion products are available on the market because their stabilization is still challenging. To stabilize all internal interfaces, at least two interfacial active substances (IAS), a lipophilic and a hydrophilic one, have to be added. These IAS can interact with each other at the interfaces and thus might impair the double emulsion stability. Especially the impact of these interactions on the loss of inner water droplets due to coalescence with the outer water phase is largely unknown.In this study, we investigated if interfacial tension measurements can be related to the loss of inner water caused by coalescence. We determined the outer oil in water interfacial tension of a double emulsion, when a hydrophilic or a lipophilic IAS is used individually as well as in combination. Furthermore, the coalescence process between a water droplet encapsulated in oil and an adjacent continuous water phase was observed in single droplet experiments.As model system polyvinyl-alcohol (PVOH) was used as hydrophilic and polyglycerol-polyricinoleate (PGPR) was used as lipophilic IAS. For the sole use of PVOH, the behavior of the coalescence process can be related to the interfacial tension, which was changed by varying the PVOH type. It could be shown that the lower the interfacial tension is, the longer is the time until the coalescence process takes place. In addition, the duration of the coalescence process itself increases by decreasing the interfacial tension for the system under study.In case of the combined use of PVOH and PGPR, the observations differ in dependency on the PVOH type. In case of PVOH with a low hydrophobicity, the simultaneous presence of PGPR caused only a minor change of the coalescence behavior compared to the sole use of PVOH. In case of a PVOH type with higher hydrophobicity, the coalescence behavior changed clearly by the presence of PGPR. However, no correlation to the interfacial tension was found.

Effect of outer water phase composition on oil droplet size and yield of (w1/o/w2) double emulsions

In this study the effect of various emulsifiers (whey protein isolate (WPI), Na-caseinate, and Tween 20) and thickeners (xanthan and pectin) present in the outer water phase, w2, on oil droplet size and yield of the inner water phase, w1, of (w1/o/w2) double emulsions was investigated. Double emulsions stabilized by Tween 20 had smaller oil droplet sizes and higher yields in comparison to emulsions stabilized by WPI and Na-caseinate. Gelation of the inner water droplets w1 increased yield by 20% for all emulsifiers. Upon the addition of thickeners, the increasing viscosity of the outer water phase, w2, facilitated oil droplet breakup. This resulted in smaller oil droplets and lower yields. When pectin was used as a thickener, in comparison to xanthan, an additional decrease in yield was observed. The yield decreased to values close to zero indicating that all inner water droplets w1 were lost during emulsification.We conclude that type of hydrophilic emulsifier, properties of inner water droplets, viscosity ratio of continuous and dispersed phase, as well as type of thickener influence oil droplet size and yield of w1 phase of double emulsions. This work provides a better understanding of how composition influences the properties of double emulsions and how this can be used to design double emulsions as fat replacers in more complex food systems.

Investigations on the influence of osmotic active substances on the structure of water in oil emulsions for the application as inner phase in double emulsions

Water in oil in water (WOW) double emulsions have a great potential as encapsulation systems in different industrial sections. Nevertheless, there are only few double emulsion based products available on market. An important limitation, regarding the product launch, is the insufficient stability of these products. Many instability mechanisms have to be taken into account: coalescence between inner water droplets, coalescence between outer oil droplets, coalescence between inner and outer water phase, and diffusion between the dispersed water droplets and the continuous outer water phase. In the present study, we focus on structural changes and stabilization mechanisms of inner water in oil (WO) emulsions. Osmotic active substances (OAS) have to be used in the inner water droplets to limit the diffusion processes between the water phases in double emulsions. We therefore investigated the influence of different OAS on the structural changes in WO emulsions. We focused on three subprocesses influencing the emulsification result: droplet breakup, stabilization directly after breakup and diffusional processes after droplet stabilization. For this, we prepared WO emulsions using sodium chloride, calcium chloride and glucose as OAS and polyglycerine-polyricinoleate as lipophilic emulsifier. The droplet size distribution was determined to evaluate structural changes. Furthermore, we measured interfacial properties and emulsion viscosities to evaluate stabilizing effects. Kinetic stabilization effects were evaluated by applying high pressure homogenization, known as a process with high requirements on the stabilization efficiency. The osmolality of the inner water phases was determined as parameter for the likelihood of diffusional processes. This characteristic value strongly depends on OAS type and concentration. Adsorption kinetics and diffusional processes turned out as the main factors influencing inner emulsion structure.

The influence of hydrophilic mPEG segment on formation, morphology, and properties of PCL‐mPEG microspheres

AbstractThis research displayed the differences of formation process, morphology, degradation, and release behaviors between PCL and PCL‐mPEG microspheres. Lysozyme loaded microspheres were prepared by double emulsion evaporation method, and the double droplets transformation process was observed and compared under microscope. Microspheres morphology, in vitro degradation and release behaviors were evaluated by scanning electron microscope, gel permeation chromatography, and bicinchoninic acid protein assay kit. PCL‐mPEG microspheres got a rough surface and the outer water phase penetrated into PCL‐mPEG double droplet easier than PCL during the transformation, accompanied with a high broken percentage and size swelling. PCL‐mPEG microspheres get a faster degradation/erosion rate than PCL microspheres, and the rate was in direct proportion to mPEG chain length. In vitro release analysis showed that PCL‐mPEG microspheres get a faster release rate than PCL microspheres, and the rate was also in direct proportion to mPEG chain length.

Food-grade double emulsions as effective fat replacers in meat systems

Double emulsions were used to not only replace 7 and 11% of animal fat in meat products, but also as a way to enhance the product colour. The coarse emulsion containing native beetroot juice as inner water phase, sunflower oil as oil phase and 0.5% whey protein isolate as outer water phase was prepared using a rotor stator system. The resulting coarse double emulsion had a typical average droplet size of 32 μm, that was refined further using a hybrid membrane premix emulsification system resulting in an average droplet size of 20 μm. Both double emulsions were exposed to heat threatment (70 °C for 30 min), and were physically stable due to the high viscosity (2.9 Pa s). Besides these emulsions had high colour retention. When added to meat systems, both double emulsions showed good water and fat binding capacity, and they reduced the hardness and improved the colour of meat systems, which are both desirable characteristics. The main conclusion of the paper is that double emulsion technology can be used to reach dual functionality in meat products; reduction of caloric load and colour retention.

Formulation of W/O/W emulsions loaded with short-chain fatty acid and their stability improvement by layer-by-layer deposition using dietary fibers

This study prepared water-in-oil-in-water (W/O/W) emulsions loaded with short-chain fatty acid (SCFA) and attempts to improve their stability with layer-by-layer deposition using dietary fibers. The water-in-oil (W/O) emulsion consisted of an inner water phase containing 5 wt% butyric acid and soybean oil phase containing a hydrophobic emulsifier. The weight fraction of the inner water phase was 5 wt%. W/O emulsions with a Sauter mean droplet diameter (d3,2) of 0.4 μm were prepared using high-pressure homogenization. The W/O/W emulsion consisted of W/O emulsion dispersed in an outer water phase containing 0.5 wt% modified lecithin, and the weight fraction of the W/O phase was 20 wt%. The W/O phase was dispersed in the modified lecithin solution to prepare a W/O/W emulsion using rotor-stator homogenization. The d3,2 of the resultant W/O/W emulsion droplets was 16.9 μm, and their ζ-potential was −77.8 mV at pH 5. W/O/W emulsion droplets were coated with chitosan (CHI) and carboxymethyl cellulose (CMC), which is driven by electrostatic interaction. The ζ-potential data indicated successful coating of the droplets. W/O/W emulsion droplets coated with dietary fibers were highly stable over 4 weeks. Our results demonstrated that W/O/W emulsions loaded with SCFA could be better stabilized with layer-by-layer coating using dietary fibers.

Synthesis of Nanovesicular Glutathione Peroxidase Mimics with a Selenenylsulfide-Bearing Lipid.

In this article, we describe the development of a nanosized-glutathione peroxidase (GPx) mimic based on liposomes of which the amphiphilic selenenylsulfide derivative (R–Se–S–R′) was incorporated into a lipid membrane. A lipid membrane-compatible selenenylsulfide derivative, 1-oxo-headecyl-seleno-l-cysteine-methyl-Se-yl-S-l-penicillamine methyl ester (OHSeP), was synthesized. X-ray photoelectron spectroscopy revealed that the sulfur and selenium atoms of the OHSeP molecule formed a selenenylsulfide linkage. The use of OHSeP easily allowed the introduction of the seleno-l-cysteine (SeCys) moiety into the liposomal membranes by mixing with the phosphatidylcholines (PCs), which gave rise to the GPx-like catalytic activity because of the selenium atom in the SeCys moiety. The penicillamine moiety of the OHSeP molecule incorporated into the OHSeP/PC liposomes was thought to orient toward the outer water phase. The OHSeP/PC liposomes generated the GPx-like catalytic activity, which was ascribed to the SeCys moiety that was introduced into the PC-based liposomes. Consequently, the lipid/water interface of the liposomal membranes could possibly provide an effective colloidal platform for the development of water-soluble nanosized GPx mimics.

Monodisperse Uni- and Multicompartment Liposomes.

Liposomes are self-assembled phospholipid vesicles with great potential in fields ranging from targeted drug delivery to artificial cells. The formation of liposomes using microfluidic techniques has seen considerable progress, but the liposomes formation process itself has not been studied in great detail. As a result, high throughput, high-yielding routes to monodisperse liposomes with multiple compartments have not been demonstrated. Here, we report on a surfactant-assisted microfluidic route to uniform, single bilayer liposomes, ranging from 25 to 190 μm, and with or without multiple inner compartments. The key of our method is the precise control over the developing interfacial energies of complex W/O/W emulsion systems during liposome formation, which is achieved via an additional surfactant in the outer water phase. The liposomes consist of single bilayers, as demonstrated by nanopore formation experiments and confocal fluorescence microscopy, and they can act as compartments for cell-free gene expression. The microfluidic technique can be expanded to create liposomes with a multitude of coupled compartments, opening routes to networks of multistep microreactors.

Preparation of stable food-grade double emulsions with a hybrid premix membrane emulsification system

In this study we demonstrate that food-grade double emulsions can be successfully prepared using a hybrid premix emulsification system. A coarse emulsion containing beetroot juice as inner water phase, sunflower oil as oil phase and 0.5% or 1.0% whey protein isolate solution as outer water phase was prepared using a rotor stator system. This emulsion was further refined, using a bed of glass beads (diameter 71μm), through which the emulsion was pushed at different applied pressure (200–500kPa) and number of passes (1–5). All applied pressures lead to much smaller droplets while the juice remained encapsulated (>98%). The viscosity of the emulsions increased due to swelling of the internal water phase, and this implies that it is possible to encapsulate the components efficiently at relatively low internal water phase fraction at which the emulsions can be handled easily, while allowing them to obtain their final viscosity later.

Influence of Processing on the Physical Stability of Multiple Emulsions Containing a Green Solvent

AbstractThe influence of the emulsification process on the microstructure and physical stability of model water‐in‐oil‐in‐water (W/O/W) emulsions formulated with a green solvent and a mixture of amphiphilic copolymers as emulsifiers was investigated. Emulsions were prepared by applying a homogenization step with a rotor‐stator device followed by high‐pressure homogenization. Viscous flow tests, transmitted light optical microscopy, globule size distribution (GSD), and multiple light scattering (MLS) measurements were carried out. The GSDs obtained were the result of a recoalescence due to overprocessing and the coalescence of inner droplets with the outer water phase. MLS detected a main destabilization mechanism by creaming. The passing of the emulsion through a high‐pressure homogenizer (HPH) significantly delayed the creaming process.

Improvement of sphericity of thick-walled polystyrene shell

Abstract Thick-walled polymer shells with high sphericity are always needed in the inertial confined fusion (ICF) experiments. The introduction of hexadecane (H) into the oil phase (O) was used to explore possible effects in improving the sphericity of polystyrene (PS) shells. The experimental results showed that not only the interfacial tension increased, but also the density matching levels between the inner water phase (W1) and the oil phase, and that between the W1/O compound droplets and the outer water phase (W2) were improved, probably due to the hydrophobic characteristic and low density of H. Therefore, the batch yield of PS shells with the out-of-round ( δ OOR ) values less than 1 μm increased from 16% to 60% with increasing H mass fraction in the O phase from 0 to 0.6%. For wall uniformity, the yield of the PS shells with Δ t w less than 3 μm also increased from 45% to 67%, but there was no further increase when H mass fraction in the O phase was more than 0.2%. However, when the H mass fraction was 1.0%, the PS shells became opaque, since there were many voids in the shells resulting from very low solubility of H in water. Therefore, the H concentrations in the O phase should be controlled according to the requirements of the structure. Obviously, the introduction of H into the O phase provides a novel and effective method for preparing PS shells with high sphericity.

Preparation and characterization of quercetin-loaded silica microspheres stabilized by combined multiple emulsion and sol-gel processes

Despite exhibiting a wide spectrum of cosmeceutical properties, flavonoids and related compounds have some limitations related to their stability and solubility in distilledwater. In this project, we prepared silica microspheres using a novel method that uses polyol-in-oil-in-water (P/O/W) emulsion and sol-gel methods as techniques for stabilizing quercetin. A stable microsphere suspension was successfully preparedusing a mixed solvent system comprising a polyol-phase medium for performing the sol-gel processing of tetraethyl orthosilicate (TEOS) as an inorganic precursor with outer water phase. The morphology of the microsphere was evaluated using a scanning electron microscope (SEM), which showed a characteristic spherical particle shape with a smooth surface. Furthermore, SEM/EDSanalysis of a representative microsphere demonstrated that the inner structure of the silica microspheres was filled with quercetin. The mean diameter of the microsphere was in the range 20.6-35.0 ?m, and the encapsulation efficiency ranged from 17.8% to 27.5%. The free and encapsulated quercetin samples were incubated in separateaqueous solutions at 25 and 42?C for 28 days. The residualcontent of the quercetin encapsulated by silica microspheres was 82% at 42?C. In contrast, that of the free quercetin stored at 42?C decreased to ~24%.