Two-step Emulsification Process Research Articles

Bio-Inspired Crystalline Core-Shell Guanine Spherulites.

Spherical particles with diameters within the wavelength of visible light, known as spherulites, manipulate light uniquely due to their spatial organization and their structural birefringence. Most of the known crystalline spherulites are branched, and composed of metals, alloys, and semi-crystalline polymers. Recently, a different spherulite architecture is discovered in the vision systems of decapod crustaceans - core-shell spherulites composed of highly birefringent ( ) organic single-crystal platelets, with exceptional optical properties. These metastructures, which efficiently scatter light even in dense aqueous environments, have no synthetic equivalence and serve as a natural proof-of-concept as well as synthetic inspiration for thin scattering media. Here, the synthesis of core-shell spherulites composed of guanine crystal platelets (( ) is presented in a two-step emulsification process in which a water/oil/water emulsion and induced pH changes are used to promote interfacial crystallization. Carboxylic acids neutralize the dissolved guanine salts to form spherulites composed of single, radially stacked, β-guanine platelets, which are oriented tangentially to the spherulite surface. Using Mie theory calculations and forward scattering measurements from single spherulites, it is found that due to the single-crystal properties and orientation, the synthetic spherulites possess a high tangential refractive index, similarly to biogenicparticles.

Fabrication of stable Pickering double emulsion with edible chitosan/soy β-conglycinin complex particles via one-step emulsification strategy

Double emulsion is the most common multiple emulsion with compartmentalized internal structure. It can be used for delivery of both hydrophilic and hydrophobic bioactives and fat reduction in foods. However, conventional approach for stable double emulsion preparation often requires high dosage of synthetic surfactants (e.g., polyglycerol polyricinoleate, PGPR) and complicated two-step emulsification process. Herein, we report a facile approach to create stable double emulsion using particular emulsifier of edible chitosan/soy β-conglycinin (7S) complex nanoparticles via one-step emulsification. By modulating chitosan/7S complex ratio of particles and algal oil content in oil phase, water-in-oil-in-water (W/O/W) Pickering double emulsion was generated in most cases. The dominant mechanism for one-step generation of Pickering double emulsion can be attributed to the polyunsaturated fatty acids (PUFA) in algal oil. The binding of PUFA on particle surface contributes to hydrophobization of the chitosan/7S complex nanoparticles, leading to stabilization of W/O interface. Moreover, stability of the resultant Pickering double emulsions is correlated to particle contact angle. When using nanoparticles with chitosan/7S complex ratio of 1:2 and oil phase containing 40 wt% algal oil, particle contact angle at O/W interface is near 90°, which is the optimum condition to produce highly stable Pickering double emulsion. This facile approach for the fabrication of stable double emulsion is promising for a wide range of applications, particularly in food field.

Co-delivery of hydrophobic astaxanthin and hydrophilic phycocyanin by a pH-sensitive water-in-oil-in-water double emulsion-filled gellan gum hydrogel

Astaxanthin and phycocyanin were recommended for their bioactivities. However, limited stability and low bioavailability were not conducive to their applications in the food industry. A pH-sensitive double W 1 /O/W 2 emulsion-filled hydrogel loaded concomitantly with astaxanthin and phycocyanin was prepared using the two-step emulsification process. First, the W 1 /O emulsion was fabricated using polyglycerol polyricinoleate as a hydrophobic emulsifier. Second, W 1 /O/W 2 emulsions are typically formed by homogenizing W 1 /O emulsions with an aqueous phase containing sodium caseinate. Later, gellan gum was added to the double emulsion as an additional stabilizer and gelling agent to prepare the double emulsion-filled hydrogel. The influence of gellan gum on the microstructure, rheology, and stability of double emulsions was investigated. The double emulsions remained stable during 30 days’ storage when the content of gellan gum was above 0.4% since the hydrogel formation. The microstructure of double emulsions was maintained under the acidic environment due to the network formed by gellan gum while transformed from hydrogel state to solution state since the disintegration of gellan gum network under neutral conditions. Further, based on the pH-sensitive nature of double emulsion-filled hydrogel, the co-encapsulation of phycocyanin and astaxanthin and the in vitro release behavior were demonstrated. The maximum encapsulation efficiency of phycocyanin and astaxanthin was 94.1% and 90.82%, respectively. In vitro digestion proved their intestinal targeted release ability. These results suggested that the double emulsion-filled gellan gum hydrogel can be used as a pH-sensitive carrier for intestinal targeted delivery of hydrophobic and hydrophilic food bioactive ingredients. • pH-sensitive double emulsion-filled gellan gum hydrogel was prepared. • Co-encapsulation of astaxanthin and phycocyanin was achieved. • Gellan gum improved the encapsulation efficiency of astaxanthin and phycocyanin. • The double emulsions-filled hydrogel achieved intestinal targeting delivery.

Encapsulation of amino acids in water-in-oil-in-water emulsions stabilized by gum arabic and xanthan gum

In this study, several kinds of amino acids were successfully encapsulated in a W1/O/W2 emulsion produced using a two-step emulsification process. Polyglycerol polyricinoleate (PGPR) was used as a hydrophobic emulsifier in the oil phase, while gum arabic (GA) and xanthan gum (XA) were used as an emulsifier and stabilizer in the outer water (W2) phase, respectively. The stability and encapsulation efficiency of the W1/O/W2 emulsions depended on the ratio of W1/O emulsion to W2 phase, as well as the concentration of GA and XA within the outer W2 phase. A W1/O/W2 emulsion prepared using 2 % (w/w) GA and 0.3 % (w/w) XA in the W2 phase exhibited good stability and a high encapsulation efficiency (>80 %) for several amino acids. As the hydrophobicity of amino acids and storage temperature increased, the leakage from the W1 to W2 phases increased, which can be attributed to increasing solubility in the oil phase. The encapsulation efficiency of lysine encapsulated in GA-XA-stabilized W1/O/W2 double emulsion was over 84 % after 28 days storage at 4 °C. These results indicate that double emulsions may be useful for the encapsulation of amino acids, which may be useful to protect them from their environment and mask bitter flavors.

Analysis of double-emulsion droplets with ESI mass spectrometry for monitoring lipase-catalyzed ester hydrolysis at nanoliter scale

Microfluidic double-emulsion droplets allow the realization and study of biphasic chemical processes such as chemical reactions or extractions on the nanoliter scale. Double emulsions of the rare type (o1/w/o2) are used here to realize a lipase-catalyzed reaction in the non-polar phase. The surrounding aqueous phase induces the transfer of the hydrophilic product from the core oil phase, allowing on-the-fly MS analysis in single double droplets. A microfluidic two-step emulsification process is developed to generate the (o1/w/o2) double-emulsion droplets. In this first example of microfluidic double-emulsion MS coupling, we show in proof-of-concept experiments that the chemical composition of the water layer can be read online using ESI–MS. Double-emulsion droplets were further employed as two-phase micro-reactors for the hydrolysis of the lipophilic ester p-nitrophenyl palmitate catalyzed by the Candida antarctica lipase B (CalB). Finally, the formation of the hydrophilic reaction product p-nitrophenol within the double-emulsion droplet micro-reactors is verified by subjecting the double-emulsion droplets to online ESI–MS analysis.Graphical abstract

Formulation and Characterization of Chitosan-Decorated Multiple Nanoemulsion for Topical Delivery In Vitro and Ex Vivo.

In the present study, chitosan-decorated multiple nanoemulsion (MNE) was formulated using a two-step emulsification process. The formulated multiple nanoemuslion was evaluated physiochemically for its size and zeta potential, surface morphology, creaming and cracking, viscosity and pH. A Franz diffusion cell apparatus was used to carry out in vitro drug-release and permeation studies. The formulated nanoemulsion showed uniform droplet size and zeta potential. The pH and viscosity of the formulated emulsion were in the range of and suitable for topical delivery. The drug contents of the simple nanoemulsion (SNE), the chitosan-decorated nanoemulsion (CNE) and the MNE were 71 ± 2%, 82 ± 2% and 90 ± 2%, respectively. The formulated MNE showed controlled release of itraconazole as compared with that of the SNE and CNE. This was attributed to the chitosan decoration as well as to formulating multiple emulsions. The significant permeation and skin drug retention profile of the MNE were attributed to using the surfactants tween 80 and span 20 and the co-surfactant PEG 400. ATR-FTIR analysis confirmed that the MNE mainly affects the lipids and proteins of the skin, particularly the stratum corneum, which results in significantly higher permeation and retention of the drug. It was concluded that the proposed MNE formulation delivers drug to the target site of the skin and can be therapeutically used for various cutaneous fungal infections.

Preparation and drying of water-in-oil-in-water (W/O/W) double emulsion to encapsulate soy peptides

Soy peptide solution (40%, w/w) was successfully encapsulated in a W1/O/W2 double emulsion produced by a two-step emulsification process. Polyglycerol polyricinoleate (PGPR) was found to be an effective inner emulsifier compared to Span 60 and lecithin to produce stable W1/O primary emulsion. The primary emulsion was subsequently emulsified into an outer aqueous phase (W2) containing octenyl succinic anhydride (OSA) starch and maltodextrin. The droplet size and encapsulation efficiency of the peptide solution in W1/O/W2 emulsion were found to depend on the W1:O ratio, peptide concentration in the inner W1 phase and homogenization condition of the secondary emulsification step. The double emulsion with the highest encapsulation efficiency (>80%) was prepared by: (i) using 40% (w/w) soy peptide solution as W1 phase; (ii) controlling W1:O ratio at 3:7 (w/w) and (iii) homogenizing the emulsion at 10,000 rpm for 3 min. The freeze-dried microcapsule powder of W1/O/W2 emulsion showed higher encapsulation efficiency (>70%) compared to spray-dried one. The freeze-dried microcapsule of W1/O/W2 double emulsion developed in this study is a promising delivery matrix to encapsulate hydrophilic ingredients including peptides. Fourier-transform infrared spectroscopy (FTIR) spectra of the microcapsule powder indicated good compatibility between peptide and encapsulants.

Formation of stable nanoemulsions by ultrasound-assisted two-step emulsification process for topical drug delivery: Effect of oil phase composition and surfactant concentration and loratadine as ripening inhibitor.

Nanoemulsions are very interesting systems as they offer capacity to encapsulate both hydrophilic and lipophilic molecules in a single particle, as well as the controlled release of chemical moieties initially entrapped in the internal droplets. In this study, we propose a new two-step modified ultrasound-assisted phase inversion approaches-phase inversion temperature (PIT) and self-emulsification, to prepare stable o/w nanoemulsions from a fully water-dilutable microemulsion template for the transdermal delivery of loratadine (a hydrophobe and as Ostwald ripening inhibitor). Firstly, the primary water-in-oil microemulsion concentrate (w/o) was formed using loratadine in the oil phase (oleic acid or coconut oil) and Tween 80 in the aqueous phase and by adjusting the PIT around 85°C followed by stepwise dilution with water at 25°C to initiate the formation the nanoemulsions (o/w). To assure the long-term stability, a brief application of low frequency ultrasound was employed. Combining the two low energy methods resulted in nanoemulsions prepared by mixing constant surfactant/oil ratios above the PIT with varying water volume fraction (self-emulsification) during the PIT by stepwise dilution. The kinetic stability was evaluated by measuring the droplet size with time by dynamic light scattering (DLS). The droplet size ranged 15-43nm and did not exceed 100nm over the period of 6months indicating the system had high kinetic stability. Cryo-TEM showed that the nanoemulsions droplets were monodispersed and approaching micellar structure and scale. All nanoemulsions had loratadine crystals formed within 20days after preparation, which tended to sediment during storage. Nanoemulsions improved the in vitro permeation of loratadine through porcine skin up to 20 times compared to the saturated solution.

Multiple pickering high internal phase emulsions stabilized by modified diatomite particles via one-step emulsification process

Conventional approaches to generating double emulsions are cumbersome, complicated, and based on a two-step emulsification process using a combination of two distinctive surfactants. In this work, the surface properties of diatomite particles were successfully tailored by chemical modification with palmitoyl chloride. The properties of the resulting diatomite particles changed from the original hydrophilicity to hydrophobicity, leading to straightforward stabilization of oil-in-water-in-oil (O/W/O) Pickering double emulsions by a one-step emulsification process. Pickering double high internal phase emulsions (HIPEs) with an internal phase up to 80 vol% could be produced solely using the modified diatomite particles. The water-in-oil (W/O) droplet sizes of these HIPEs were much larger than the droplets of conventional nanoparticle-stabilized Pickering HIPEs. Furthermore, using the O/W/O Pickering double emulsions as templates, the porous polymer particles were fabricated. In addition, it was demonstrated that the wide particle size distribution of diatomite particles and modified heterogeneity were the reasons for the formation of multiple emulsions.

Application of the fractional factorial design in multiple W/O/W emulsions

ABSTRACTIn presented research, multiple W/O/W emulsions were developed by using experimental design method. A 24-1 fractional factorial design was performed by varying the following input parameters: primary polymeric emulsifier (PEG 30-dipolyhydroxystearate) concentration (0.8% and 2.4%), secondary polymeric emulsifier (Poloxamer 407) concentration (0.8% and 1.2%), electrolyte magnesium sulfate heptahydrate (0.08% and 0.4%) and electrolyte sodium chloride (0.08% and 0.4%). Multiple emulsions were prepared by a two-step emulsification process. Obtained emulsions were characterized with rheological measurements, conductivity and centrifugation tests. Factorial analysis revealed that the concentration of the primary emulsifier was the predominant factor influencing the phase separation, conductivity and maximal apparent viscosity. Additionally, electrolyte magnesium sulfate heptahydrate was more efficient in stabilizing these systems, compared to sodium chloride. The applied fractional factorial design method enabled determination of the optimal concentrations of the primary and secondary emulsifier, as well as the concentration of electrolytes, in order to obtain W/O/W emulsions with desired maximal apparent viscosities, low values of conductivity and without phase separation after centrifugation.

Oil-in-oil-in-water pre-double emulsions stabilized by nonionic surfactants and silica particles: A new approach for topical application of rutin

The aim of the present study was to prepare new rutin-loaded oil-in-oil-in-water (o/o/w) pre-double emulsions for topical application. The new formulations were prepared through two-step emulsification process and stabilized by hydrophobic silica particles and nonionic surfactants. Obviously, the use of a dual emulsifier system could effectively improve emulsifier tridimensional network structure strength and emulsions stability. After dilution with aqueous medium, the optimized formulations could self-emulsify to o/o/w double emulsions, with inner oil phase mainly containing the drug. Subsequently, a sustained release profile was observed for up to 12h and a good stability was achieved over a period of 3 months at 4°C and 25°C. DPPH scavenging assay confirmed that rutin could be protected by the o/o/w pre-double emulsions. Compared to rutin aqueous solution, the o/o/w pre-double emulsions presented higher ability to enhance skin permeation of rutin, and significantly increased drug distribution in the skin as well. These studies demonstrated that this new o/o/w pre-double emulsions might be a promising vehicle for topical application of poorly water-soluble and simultaneously poorly oil-soluble drugs, such as rutin.

Evaluation of a new solid non-aqueous self-double-emulsifying drug-delivery system for topical application of quercetin

This study aimed to the evaluation of a new solid non-aqueous self-double-emulsifying drug-delivery system (SDEDDS) for topical application of quercetin. The new formulation was prepared through two-step emulsification process and could spontaneously form oil-in-oil-in-water (O/O/W) double emulsions after dilution with aqueous medium, with inner oil phase mainly containing the drug. Solid state characterisation was performed by DSC and X-ray powder diffraction. Furthermore, the optimised QT-SDEDDS displayed sustained release profile and was found to be stable up to 30 days under 4 °C and 25 °C. Antioxidant capacities showed that quercetin could be protected by the solid non-aqueous SDEDDS. Compared with the quercetin ethanol aqueous solution, the QT-SDEDDS exhibited higher permeation ability, and significantly increased accumulation of quercetin in the skin. These studies demonstrated that the solid non-aqueous SDEDDS might be a promising carrier for topical application of poorly water-soluble and simultaneously poorly oil-soluble drugs, such as quercetin.

Water fluxes and encapsulation efficiency in double emulsions: impact of emulsification and osmotic pressure unbalance

We study the influence of the emulsification process on encapsulation efficiency of drugs in double water-in-oil-in-water emulsions. Two drugs were used, first vitamin B12 which can be considered as a model drug and secondly a suspension of Cydia pomonella Granulovirus (CpGV), a virus used in organic agriculture to protect fruits against the Carpocapse insect. Encapsulation is measured by classical UV-Vis spectroscopy method. Additionally we show that rheology is a useful tool to determine water exchanges during emulsification. In a two-step emulsification process, using rotor-stator mixers, encapsulation reaches high levels, close to 100% whatever the flowing regime. This encapsulation decreases only if two conditions are fulfilled simultaneously: (i) during the second emulsification step the flow is turbulent and (ii) it leads to excessive fragmentation inducing formation of too small drops. We also investigate the effect of a deliberate loss of osmotic pressure balance on the encapsulation and characterize the induced water fluxes. We show that encapsulation of vitamin B12 is not affected by the osmotic pressure unbalance, while water exchanges, if they exist, are very fast and aim at restoring equilibrium. As a consequence, the emulsification efficiency is not very sensitive to osmotic stresses provided that the interfaces resist mechanically.

Double Emulsions Stabilized by Xanthan in the Absence of Hydrophilic Surfactant

The preparation of double water-in-oil-in-water (W/O/W) emulsions containing xanthan gum (XG) in the absence of hydrophilic surfactant was investigated. The emulsions were prepared by the two-step emulsification process. The stability of these systems was evaluated through the evaluation of physicochemical and rheological properties. Microscopic observations in combination with particle size analysis were also performed. The obtained results show that it is possible to prepare stable double emulsions with a single polysaccharide by using the indirect process. The stability depends on the viscosity of the continuous phase and hence the concentration of XG. The apparent viscosity of the emulsions increased with the increase of XG concentration. Particle size analysis shows that the droplet sizes are directly related to XG concentration.

A new method to synthesize high solid content waterborne polyurethanes by strict control of bimodal particle size distribution

Abstract A new method named two-step emulsification process was developed to synthesize high solid content waterborne polyurethanes by strict control of the bimodal particle size distribution. In the first step, a series of 40% solid content polyester-based (WPU-1) with low content of hydrophilic group and large particle size were firstly synthesized. In the second step, polyether-based prepolymers (WPU-2 prepolymers) with high content of hydrophilic group were firstly prepared and WPU-1 emulsions were used to emulsify WPU-2 prepolymers to obtain the final emulsions with high solid content (WPU-3). The particle size of WPU-3 present bimodal distribution and the diameter ratio and volume percentage of large particles to small particles in WPU-3 were able to be strictly controlled by this method. The viscosity of WPU-3 with 55% solid content was only 489.1 mPa s −1 when the diameter ratio of large particles to small particles was 9.2 and the volume percentage of large particles was 74%.

Preparation of biodegradable PCL particles via double emulsion evaporation method using ultrasound technique

Polymeric nanoparticles have attracted growing attention because of their unique properties and extensive application. In this study, polycaprolactone (PCL) nanoparticles were prepared via double emulsion solvent evaporation-like process using power ultrasound, and the effects of various process parameters on particle size, zeta potential, and morphology were investigated and optimized. Nanoparticles (NPs) were prepared by two-step emulsification process. In the first step, the inner aqueous phase (W1) was homogenized with organic phase (PCL in dichloromethane) to obtain primary emulsion. In the second step, the primary emulsion was emulsified with outer aqueous phase (W2) containing polyvinyl alcohol (PVA) as stabilizer using power ultrasound, followed by evaporation of solvent which resulted in a particulate suspension at the end. Effects of various parameters like ultrasound exposure time and amplitude, outer aqueous phase volume, PVA concentration, and PCL content were investigated. It has been shown that, by increasing ultrasound exposure time, amplitude, and outer aqueous phase volume, the particle size decreases. Additionally, particle size was also related to amount of PCL and PVA concentration. Spherical NPs with smooth surfaces were observed by scanning electron microscopy (SEM).

Polyglyceryl-10 Stearate를 이용한 W/O/W 다중 에멀젼의 제조에 관한 연구

다중 에멀젼은 다층 구조를 갖는 에멀젼으로 W/O/W형과 O/W/O형으로 구분된다. 화장품 분야에서 다중에멀젼은 불안정한 유효성분의 안정화를 위해 이용되지만, 제조의 어려움과 안정성 등의 문제로 잘 이용되지 않는다. 본 연구에서는 다중 에멀젼의 제조에 있어 2 단계(two-step) 유화법을 이용하여 W/O/W형 다중 에멀젼을 제조하였고, 다중 에멀젼의 형성에 영향을 주는 요소 중 유화제의 계열에 초점을 두어 유화 안정성 및 에멀젼 형성정도를 측정하였다. 결과를 통해 다중 에멀젼은 오일의 특성에 따라 polyglyceryl-10 stearate 유화제에 의해 다중 에멀젼의 형성이 달라지는 것을 확인하였고, 이를 통해 주 유화제로써 polyglyceryl-10 stearate 유화제의 적용이 다중 에멀젼 형성 및 안정화의 가능성이 있음을 제시하였다.

Impact of electrolytes on double emulsion systems (W/O/W) stabilized by an amphiphilic block copolymer

In this work, the block copolypeptide surfactant, poly(l-lysine·HBr)40-b-poly(racemic-leucine)20, was synthesized and characterized, then used to build water-in-oil-in-water (W/O/W) double emulsions. Double emulsions are usually prepared by a two-step emulsification process and commonly stabilized using a combination of hydrophilic and hydrophobic surfactants. Herein, we report a one-step phase inversion process to produce water-in-oil-in-water (W/O/W) double emulsions stabilized by a synthetic diblock copolymer and electrolyte. It was found that the O/W ratio and the type of electrolyte had a marked effect on the formation and type of the double emulsions. Moreover, double emulsions containing an NaCl isotonic solution were stable for at least two months, whereas those using glucose as a substitute for NaCl showed a clear compartmental change. The mechanism behind this was related to the electrostatic interaction between the anion of the electrolyte and the cation of the polylysine residues, which affected the HLB value and curvature. This novel finding is very interesting in terms of both scientific research and practical applications.

Formulation and Characterization of Double Emulsions Stabilized by Sodium Caseinate–Xanthan Mixtures. Effect of pH and Biopolymer Concentration

Water-in-oil-in-water (w/o/w) double emulsions were stabilized by xanthan gum (XG) in presence of sodium caseinate (SC) using a two-step emulsification process. The evaluation of stability of emulsions was conducted over a period of 20 days. This monitoring was revealed by studying the physicochemical and rheological properties and by optical microscopy observations in combination with granulometry measurements. At natural pH, stability of double emulsions prepared by XG–SC mixture depends on XG concentration. The apparent viscosity of the emulsions increased with the increase of XG concentration. Adjustment of pH of emulsions made with XG–SC near the isoelectric point of the protein improved their stability. At this pH, the viscosity is affected by the XG and SC concentrations. The droplet sizes of double emulsions stabilized by the SC–XG mixture are influenced by the pH and the concentration of two biopolymers. The weight ratio between the two biopolymers in the external aqueous phase has a great influence on the stability of double emulsions formulated at natural pH and pH 5.

Production of monodisperse multivesiculated polyester particles with a T-junction microfluidic device

Production of monodisperse multivesiculated particles (MVPs) of polyester reticulated with styrene was studied using a T-junction device for droplet generation. The process is based on a w/o/w double emulsion, which after crosslinking and drying yields solid particles filled with closely packed microvoids. The effect of continuous and dispersed phase flow rates, protective colloid concentration, and temperature on droplet size was studied. SEM analysis of internal morphology of particles produced using a one-step double emulsification process indicated that vesiculation was sparse and mostly located in the particle outer layer. This was attributed to the long time needed for water diffusion to fill-in the organic droplets. Much better results were obtained using a two-step emulsification process, in which water was pre-emulsified in the organic phase, and the final double emulsion was generated in the T-junction. Monodisperse particles with uniform vesiculation throughout the entire core were obtained in this way. The pre-emulsion was observed to be more stable when using triethanolamine instead of diethylenetriamine as w/o stabilization promoter, allowing for continuous production for longer runs.