Spontaneous Emulsification Research Articles

Curcumin-loaded colloidal carrier system: formulation optimization, mechanistic insight, ex vivo and in vivo evaluation.

The present work investigated the topical delivery potential of nanoemulsion gel loaded with curcumin (CR). CR nanoemulsion (CR-NE) was prepared by spontaneous emulsification method using oil (Labrafac PG/glyceryl triacetate), surfactant:cosurfactant (Smix) (tween 80/polyethylene glycol [PEG] 400) and water. The pseudo-ternary phase diagrams were constructed and thermodynamic stability testing was performed. Droplet size and zeta potential were evaluated using photon correlation spectroscopy and transmission electron spectroscopy. Six formulations selected with an average droplet size ≤70±2.72 nm showed a fourfold increase in skin permeation as compared to crude CR solution in oil. The formulation CR-NE4 having a flux of 117.04±2.32 µg/cm2/h and with maximum retention (42.87%) was selected, characterized (droplet size =41.13±3.34 nm and zeta potential =−33.1±1.45 mV), and incorporated into gel using carbopol-980 (1% w/v). Skin dynamics analyzed by confocal laser scanning microscopy showed maximum deposition of CR up to a depth of 86.98 µm and was in concordance with differential scanning calorimetry and Fourier transform infrared spectroscopy studies that confirmed lipid bilayer disruption, enhancing permeation. A 28-day anti-arthritic evaluation (body weight, paw edema, tibiotarsal joint thickness, TNF-α and IL-1β levels, and histopathology) on Freund’s complete adjuvant induced arthritic rat model after topical application of CR-NE gel in Wistar rats demonstrated substantial reversal of arthritic symptoms. Thus, CR-NE gel possesses potential for therapeutic effects locally in inflammatory arthritic disorders with improved topical bioavailability.

Natural Bioadhesive Biodegradable Nanoparticle-Based Topical Ophthalmic Formulations for Management of Glaucoma.

We prepared and characterized topical ophthalmic formulations containing brimonidine-loaded bioadhesive cationic chitosan or anionic alginate nanoparticles (NPs) for sustained release of brimonidine as once daily regimen for management of glaucoma. Nanoparticles were prepared using a spontaneous emulsification solvent diffusion method. Different concentrations of polymers, emulsifiers, and NPs stabilizers were used for formulation optimization. Nanoparticles were characterized regarding particle size, zeta potential, morphology, and drug content. Brimonidine-loaded NPs were incorporated into eye drops, a temperature-triggered in situ gelling system, and a preformed gel. They then were characterized regarding their pH, viscosity, uniformity of drug content, in vitro release characteristics, in vitro cytotoxicity, and in vivo intraocular pressure (IOP) lowering effects. Characteristics of optimized brimonidine-loaded chitosan and alginate NPs, respectively, are: particle size, 115.67 ± 3.58 and 157.67 ± 5.53 nm; zeta potential, +35.27 ± 3.39 and -37.8 ± 3.77 mV; encapsulation efficiency, 74.34% ± 2.05% and 70.40% ± 2.77%; drug loading, 11.81% ± 0.67% and 13.14% ± 0.90%; and yield, 87.91% ± 5.92% and 76.53% ± 3.32%. Transmission electron microscope (TEM) analyses revealed that NPs have spherical shapes with a dense core and distinct coat. Formulations possessed uniform drug content. Furthermore, pH and viscosity were compatible with the eye. Formulations showed a sustained release without any burst effect with a Higuchi non-Fickian diffusion mechanism. Cytotoxicity studies revealed that all formulations are biocompatible. Importantly, all formulations possessed a sustained IOP lowering effect compared to the marketed brimonidine tartrate eye drops. These formulations provide a great improvement in topical ocular brimonidine delivery. The application of a single drop is sufficient to provide extended IOP reduction, which should improve patient compliance. We have developed a novel biocompatible topical delivery system for brimonidine, a first line glaucoma medication. Once daily application should have positive effects on patient compliance and, therefore, preservation of vision.

Investigation of ouzo effect colloid formation via organosilica nanoparticles

The ouzo effect is a rapid route to nanoparticle formation through nanoprecipitation via the addition of a poor solvent to supersaturate a polymer solution. Currently, there are differing opinions on the mechanism of particle formation: nucleation and growth, nucleation and aggregation, or spinodal decomposition. To elucidate the mechanism, various concentrations of organosilica were added as artificial nucleation embryos to poly(methyl methacrylate)-tetrahydrofuran solutions prior to nanoprecipitation. Particle size distribution was monitored via dynamic light scattering, while the morphology and organic content of select samples were further characterized via transmission electron microscopy and thermal gravimetric analysis, respectively. The data establishes that spinodal decomposition was the mechanism of particle formation and that silica can be used as an additive for particle size distribution control during ouzo effect particle formation.

Fabrication of protein nanoparticles and microparticles within water domains formed in surfactant–oil–water mixtures: Phase inversion temperature method

Protein nanoparticles and microparticles can be formed using numerous fabrication methods. In this study, a templating method was developed that involves trapping globular proteins within the aqueous domains formed by surfactant–oil–water (SOW) mixtures, and then inducing protein aggregation and particle formation through thermal denaturation. A heat-set gelling protein (whey protein isolate) was located in the aqueous phase of an oil-in-water nanoemulsion formed by spontaneous emulsification. This system was then heated to promote the conversion of the oil-in-water nanoemulsion into a bicontinuous microemulsion at the phase inversion temperature (PIT) or a water-in-oil emulsion above the PIT. In principle, the nature of the aqueous domains present in the SOW system when the protein molecules unfold and aggregate determine the size and morphology of the protein particles formed. In this study, turbidity, rheology, and confocal fluorescence microscopy measurements were used to show that spheroid protein particles (1–10 μm) could be formed by heating SOW mixtures to a temperature above the PIT (which led to the formation of W/O emulsions) and where protein denaturation and aggregation occurred. This approach offers an alternative to existing methods of fabricating protein nanoparticles and microparticles suitable for utilization in the food and other industries. The major disadvantages of the method are that appreciable amounts of surfactant and oil are required in the particle-templating process, and that elevated temperatures are required to induce phase inversion and thermal denaturation.

Investigation of Size and Morphology of Chitosan Nanoparticles Used in Drug Delivery System Employing Chemometric Technique.

The polymeric nanoparticles are prepared from biocompatible polymers in size between 10-1000 nm. Chitosan is a biocompatible polymer that - can be utilized as drug delivery systems. In this study, chitosan nanoparticles were synthesized using an optimized spontaneous emulsification method. Determining particle size and morphology are two critical parameters in nanotechnology. The aim of this study is to introduce methodology based on relation between particle size and diffuse reflectance infrared fourier transform (DRIFT) spectroscopy technique. Partial least squares (PLS) technique was used to estimate the average particle size based on DRIFT spectra. Forty two different chitosan nanoparticle samples with different particle sizes were analyzed using DRIFT spectrometry and the obtained data were processed by PLS. Results obtained from the real samples were compared to those obtained using field emission scanning electron microscope(FE-SEM) as a reference method. It was observed that PLS could correctly predict the average particle size of synthesized sample. Nanoparticles and their morphological state were determined by FE-SEM. Based on morphological characteristics analyzing with proposed method the samples were separated into two groups of "appropriate" and "inappropriate". Chemometrics methods such as principal component analysis, cluster analysis (CA) and linear discriminate analysis (LDA) were used to classify chitosan nanoparticles in terms of morphology. The percent of correctly classified samples using LDA were 100 %and 90% for training and test sets, respectively.

Optimization of Curcuminoid-Loaded PLGA Nanoparticles Using Box-Behnken Statistical Design

Curcuminoids are a mixture of phenolic compounds isolated from Curcuma longa L. (turmeric) rhizomes that possess antioxidant, anti-inflammatory, anti-Alzheimer and anticancer activities. However, curcuminoids have poor solubility in acid and neutral solutions, rapid decomposition in neutral and alkaline solutions, and low bioavailability that limits their use as therapeutic agents. To overcome these problems, statistical design for preparation and characterization of poly(D,L-lactide-co-glycolide) (PLGA) nanoparticles as a carrier for curcuminoids was evaluated in this study. The curcuminoid-loaded PLGA nanoparticles were prepared by a modified spontaneous emulsification solvent diffusion method using polyvinyl alcohol (PVA) as a stabilizer. The formulations were optimized using three-factor, three-level Box-Behnken experimental design. The independent variables in the formulations were the lactide/glycolide (LA/GA) molar ratio of PLGA (50:50 to 85:15), the curcuminoid concentration (2%-10%, w/v), and the PVA concentration (3%-7%, w/v). The dependent variables were particle size, loading capacity and entrapment efficiency. Statistical evaluation showed that the LA/GA molar ratio of PLGA and the curcuminoid and PVA concentrations all affected the characteristics of the PLGA nanoparticles. To achieve a minimum particle size and maximum loading capacity and entrapment efficiency, the optimal formulation of the curcuminoid-loaded PLGA nanoparticles had a LA/GA molar ratio of PLGA of 50:50, 10% (w/v) curcuminoids, and 3% (w/v) PVA. A sustainable in vitro release profile of curcuminoids was obtained from this optimal formulation.

Tuneable stability of nanoemulsions fabricated using spontaneous emulsification by biopolymer electrostatic deposition

Nanoemulsions can be formed spontaneously from surfactant–oil–water systems using low energy methods. In this work, we showed that the droplets in oil–in–water nanoemulsions fabricated by spontaneous emulsification could be coated with an anionic biopolymer (beet pectin) using electrostatic deposition. Nanoemulsions were formed by titrating oil (medium chain triglycerides) and surfactant (polyoxyethylene sorbitan monostearate+lauric arginate) mixtures into an aqueous solution (10mM citrate buffer, pH 4). Lauric arginate was used to generate a positive charge on the droplet surfaces, thereby enabling subsequent electrostatic deposition of anionic pectin. Extensive droplet aggregation occurred when intermediate pectin concentrations were used due to bridging flocculation. However, stable anionic pectin-coated lipid droplets could be formed at high pectin concentrations. These results demonstrate the possibility of tailoring the functionality of lipid nanodroplets produced by spontaneous emulsification.

Aluminium-phthalocyanine chloride nanoemulsions for anticancer photodynamic therapy: Development and in vitro activity against monolayers and spheroids of human mammary adenocarcinoma MCF-7 cells.

BackgroundPhotodynamic therapy (PDT) combines light, molecular oxygen and a photosensitizer to induce oxidative stress in target cells. Certain hydrophobic photosensitizers, such as aluminium-phthalocyanine chloride (AlPc), have significant potential for antitumor PDT applications. However, hydrophobic molecules often require drug-delivery systems, such as nanostructures, to improve their pharmacokinetic properties and to prevent aggregation, which has a quenching effect on the photoemission properties in aqueous media. As a result, this work aims to develop and test the efficacy of an AlPc in the form of a nanoemulsion to enable its use in anticancer PDT.ResultsThe nanoemulsion was developed using castor oil and Cremophor ELP®, and a monodisperse population of nanodroplets with a hydrodynamic diameter of approximately 25 nm was obtained. While free AlPc failed to show significant activity against human breast adenocarcinoma MCF-7 cells in an in vitro PDT assay, the AlPc in the nanoemulsion showed intense photodynamic activity. Photoactivated AlPc exhibited a 50 % cytotoxicity concentration (CC50) of 6.0 nM when applied to MCF-7 cell monolayers and exerted a powerful cytotoxic effect on MCF-7 cell spheroids.ConclusionThrough the use of spontaneous emulsification, a stable AlPc nanoemulsion was developed that exhibits strong in vitro photodynamic activity on cancer cells.Electronic supplementary materialThe online version of this article (doi:10.1186/s12951-015-0095-3) contains supplementary material, which is available to authorized users.

Physical and oxidative stability of fish oil nanoemulsions produced by spontaneous emulsification: Effect of surfactant concentration and particle size

Nanoemulsion-based delivery systems offer many potential benefits for incorporating omega-3 oils into foods and beverages. Nanoemulsions are gaining popularity because of their ease of preparation, small particle size, relatively high stability, and production of optically transparent emulsions. In this study, spontaneous emulsification, a low-energy method, was used to fabricate fish oil nanoemulsions. The influence of surfactant-to-oil-ratio on particle size and physical stability was evaluated. Optically transparent nanoemulsions were formed and maintained physical stability at 37°C for 14days. Furthermore, the effect of particle size and surfactant concentration on oxidative stability of these nanoemulsions was compared to emulsions produced by microfluidizer, a high-energy method. These nanoemulsions had similar oxidative stabilities at 55°C for 14days. These results demonstrate that spontaneous emulsification can produce fish oil nanoemulsions that are physically stable and oxidize at similar rates as traditionally prepared nanoemulsions, and therefore may be suitable for fortifying clear food systems.

Ketoprofen-loaded pomegranate seed oil nanoemulsion stabilized by pullulan: Selective antiglioma formulation for intravenous administration

This study aimed to prepare pomegranate seed oil nanoemulsions containing ketoprofen using pullulan as a polymeric stabilizer, and to evaluate antitumor activity against in vitro glioma cells. Formulations were prepared by the spontaneous emulsification method and different concentrations of pullulan were tested. Nanoemulsions presented adequate droplet size, polydispersity index, zeta potential, pH, ketoprofen content and encapsulation efficiency. Nanoemulsions were able to delay the photodegradation profile of ketoprofen under UVC radiation, regardless of the concentration of pullulan. In vitro release study indicates that nanoemulsions were able to release approximately 95.0% of ketoprofen in 5h. Free ketoprofen and formulations were considered hemocompatible at 1μg/mL, in a hemolysis study, for intravenous administration. In addition, a formulation containing the highest concentration of pullulan was tested against C6 cell line and demonstrated significant activity, and did not reduce fibroblasts viability. Thus, pullulan can be considered an interesting excipient to prepare nanostructured systems and nanoemulsion formulations can be considered promising alternatives for the treatment of glioma.

Amazon Nanotechnology Network Applied to Drugs (RANAF)

Submit Manuscript | http://medcraveonline.com Growing interest has been observed in the last years for nanostructures applied to biomedical area, especially regarding controlled release of drugs. Progressive release of the drug, transport to specific tissues, increase therapeutic index, reduce side effects, constant plasmatic levels, increased absorption and bioavailability can be considered special advantages of nanoformulations. Several types of nanoformulations have been developed, including a main group which can be classified as nanodispersions. Systems formed by two immiscible liquids and small droplets in a nanosize range, often stabilized by one or more surfactants, are called nanoemulsions. Bluish reflect associated to Tyndall effect can be observed when they are formed and several methods have been used to generate nanoemulsions, such as spontaneous emulsification, low or high energy methods. Considering the intrinsic nature of the drug, if solid insoluble substances are used, it may be usefull to prepared nanocrystals (nanosuspensions). More complex structures can be achieved by using polymeric coating, affording obtainment of nanoparticles. Polymer choice, on this specific case, is a critical point, considering that this component may modulate controlled release of substances. In all cases, utilization of economic viable methods is encouraged, which also must be reproducible and able to encapsulate the drug. Scales up have been successfully performed and nowadays, nanoformulations can be used as novel therapeutic agents by consumers. On this context, “Rede Amazonica de Nanotecnologia Aplicada a Farmacos (RANAF)” (Amazon Nanotechnology Network Applied to Drugs) was created and started with approval of the project entitled “Nanoencapsulation of anti-inflammatory drugs from synthetic and natural origin in polymeric matrix for controlled release”, with had finantial support from Brazilian Research Concil (CNPq, register number 564745/2010-3). RANAF has been performing a main whole to consolidate nanotechnology research through Amazon institutions, being also supported by important groups from other countries, such as Cuba and France (French Guyanne). Great Amazon biodiversity, which is outstanding in Amapa State (Brazil), can be sustainably used in order to achieve innovative natural product based nanoformulations. This is a main aim of RANAF studies, being applicable not only for pharmaceuticals, but also for food, cosmetics, pesticides and other products. Recently, the Laboratory of Phytopharmaceutical Nanobiotechnology was created to involve all development steps, being decisive together with Drug Research Laboratory, to carry RANAF research for different applications, including nanonutraceuticals and nanomedicines for anti-inflammatory, antidepressant, ansiolitica and erectile dysfunction treatment, among others. Commentary Commentary

Formation and characterization of filled hydrogel beads based on calcium alginate: Factors influencing nanoemulsion retention and release

Filled hydrogel particles fabricated from natural lipids and biopolymers can be utilized as tailor-made encapsulation and delivery systems. In the present study, the impact of nanoemulsion fabrication method (low energy versus high energy) on the retention and release of a lipophilic bioactive component (curcumin) and of lipid droplets from calcium alginate beads was investigated. Initially, curcumin was dissolved within an oil phase, and then the oil phase was encapsulated within the hydrogel beads using a two-step process. First, nanoemulsions composed of the same constituents (medium chain triglycerides, Tween 60, curcumin, and phosphate buffer) were prepared using either low energy (spontaneous emulsification) or high energy (microfluidization) homogenization. Second, the nanoemulsions were mixed with alginate solutions (0.25–1.5%), and then the resulting mixture was dripped into calcium solutions (10–500 mM) to form filled hydrogel beads. Unloaded beads became more spherical and rigid with increasing alginate and calcium concentrations. Turbidity and spectrophotometry measurements showed that the amount and extent of curcumin and lipid droplet release from the hydrogel beads decreased with increasing alginate and calcium concentration, which was attributed to a reduction in the pore size of the hydrogel matrix. In particular, a high amounts of curcumin released were observed in delivery systems containing high Tween 60 concentrations, which was attributed to rapid diffusion of curcumin-loaded surfactant micelles out of the beads. These results have important implications for the design of delivery systems to entrap and control the release of lipophilic bioactive components within filled hydrogel particles.

Preparation, characterization, and in vivo study of rhein-loaded poly(lactic-co-glycolic acid) nanoparticles for oral delivery

A novel rhein formulation based on poly(lactic-co-glycolic acid) (PLGA) nanoparticles (NPs) suitable for oral administration was developed in this study. The designed nanosystems were obtained by a modified spontaneous emulsification solvent diffusion method. The morphology of rhein-loaded PLGA NPs showed a spherical shape with a smooth surface, without any particle aggregation. Mean size of the NPs was 140.5±4.3 nm, and the zeta potential was −16.9±3.1 mV. The average drug loading was 3.9%±0.7%, and encapsulation efficiency was 84.5%±6.2%. Meanwhile, NPs are characterized by the slower release (only about 70% of rhein is released within 5 hours), and the model that fitted best for rhein released from the NPs was Higuchi kinetic model with correlation coefficient r=0.9993, revealing that rhein could be controlled released from the NPs. In vivo, NPs altered the distribution of rhein, and the half-life after oral administration was prolonged remarkably more than those of suspensions (22.6 hours vs 4.3 hours). The pharmacokinetic results indicated that the NPs had sustained-release efficacy. The area under the curve0–∞ of the NPs formulation was 3.07-fold higher than that of suspensions, suggesting that the encapsulated rhein had almost been absorbed in rats over the period of 12 hours. Although rhein-loaded PLGA NP formulations are hopefully used as a chemotherapeutic or adjuvant agent for human gastric cancer (SGC-7901), their in vivo antitumor effect and mechanisms at the molecular level still need further study.

Thermal reversibility of vitamin E-enriched emulsion-based delivery systems produced using spontaneous emulsification

The influence of temperature scanning and isothermal storage conditions on turbidity, particle size, and thermal reversibility of vitamin E-enriched emulsions produced by spontaneous emulsification was examined. Initially, the mini-emulsions formed were optically transparent and contained small droplets (d≈44nm). When heated (20–90°C), emulsions exhibited a complex turbidity–temperature profile with a phase inversion temperature (PIT) at ≈75–80°C. Temperature scanning rate had a major influence on emulsion thermal reversibility. Slow heating (0.5°C/min) above the PIT followed by quench cooling (≈67°Cmin−1) to 30°C did not appreciably increase turbidity or droplet diameter (d≈50nm), suggesting these systems were thermo-reversible. However, slow heating to temperatures below the PIT followed by rapid cooling appreciably increased droplet size and turbidity (thermo-irreversible). Cooling rate also affected emulsion thermo-reversibility: the turbidity and droplet size after heating above the PIT decreased with increasing cooling rate.

Microfluidic Selective Concentration of Microdroplet Contents by Spontaneous Emulsification

The selective concentration of the contents in a microdroplet using spontaneous emulsification was proposed and demonstrated in a microfluidic channel. Aqueous microdroplets having a 40-μm diameter, in octane containing 100 mM of Span 80, shrank to 10 μm within 10 min with nanodroplet formation at the interface of the microdroplets. The microdroplets' contents either stayed in the microdroplet or partitioned into the nanodroplets, depending on their properties. The size and the hydrophobicity of the contents are two parameters that determine concentration/separation. In addition, this method was applied to a bound complex and free ligand (B/F) separation to demonstrate its applicability to biochemical analyses. Here we report the separation of water-soluble molecules in microdroplets for the first time. This method is expected to enhance the flexibility of the design of droplet analytical processes and widen their applicability.

Liquid phase combustion of iron in an oxygen atmosphere

In this article, we report an investigation of laser-initiated ignition of pure iron rods, using optical pyrometry, video observations, and analysis of metallographic cross section of quenched burning liquid on copper plates. When ignition occurs, caused by the melting of metal, the combustion takes place in the liquid. Two distinct superposed phases (L1 and L2) are identified in the liquid, according to the known phase diagram of the iron oxide system. Our observations show that the L1 and L2 phases can be either distinct and immiscible or mixing together. The temperature of the transition at which the mixing occurs is around 2350 K. Two mechanisms are proposed to explain the mixing occurring at high temperature: the spontaneous emulsification resulting from a strong decrease of the interfacial tension between L1 and L2 and the reduction of the miscibility gap between them at high temperature. Based on the experimental data of the evolution of the temperature and the video observation of the melt for different ignition conditions, we provide a complete description of the combustion process of iron induced by laser. Eventually, an extrapolation of the iron–oxygen phase diagram, to temperatures higher than 2000 K, is proposed.

Stability Testing of Beclomethasone Dipropionate Nanoemulsion

Purpose: To perform stability studies on a nanoemulsion formulation containing beclomethasone dipropionate (BD) and prepared by spontaneous emulsification method.Method: A nanoemulsion (o/w) containing BD was prepared using eucalyptus oil, Tween-40, ethanol and distilled water. The nanoemulsions were characterized by droplet size, pH, viscosity, conductivity and refractive index. Stability studies were performed according to International Council on Harmonization (ICH) guidelines over a period of 3 months. Droplet size, pH, viscosity, conductivity and refractive index were determined monthly for 3 months. The shelf-life of the nanoemulsion formulation was determined by accelerated stability testing.Results: The droplet size, conductivity, viscosity, pH and refractive index of the optimized formulations did not change significantly (p ≥ 0.05) after 3 months of storage at room temperature (25 ºC). The shelf life was 1.83 years at room temperature.Conclusion: The study demonstrates that the physical and chemical stability of BD is enhanced when it is formulated as a nanoemulsion.Keywords: Nanoemulsion, Beclomethasone dipropionate, Shelf-life, Accelerated stability, Viscosity, Conductivity, Refractive index

Enhanced dissolution and oral bioavailability of nifedipine by spontaneous emulsifying powders: Effect of solid carriers and dietary state

The objective of this study was to prepare spontaneous emulsifying powder (SEP) for improving dissolution and enhancing oral bioavailability of a poorly water-soluble drug, nifedipine (NDP). In order to investigate the effects of solid carrier properties, such as surface area and pore size, and a concurrent food intake on absorption of NDP in rats, different SEP formulations were prepared by adsorbing liquid spontaneous emulsifying formulation (SEF), composing of polyoxyl 35 castor oil, caprylic/capric glyceride and diethylene glycol monoethyl ether at a ratio of 1:1:8, onto various solid carriers (i.e., silica (FS), porous calcium silicate (PCS) and porous silicon dioxide). The solid characterization by scanning electron microscopy, differential scanning calorimetry and powder X-ray diffraction revealed the absence of crystalline NDP in the formulations. SEP also demonstrated excellent spontaneous emulsification properties similar to SEF. The droplet size of emulsions formed after dilution was less than 200nm. The solid carriers (particularly PCS) had significant and positive effect in drug dissolution; the mean dissolution time of SEP containing PCS was considerably improved. SEP also provided a good stability after storage in accelerated and long-term conditions for 6months. The bioavailability study resulted in enhanced values of Cmax and AUC for SEP formulations, when tested in both fasted and fed rats. Furthermore, comparing the AUC in fasted and fed rats, NDP powder exhibited a significant food effect. The difference in bioavailability of NDP in fed compared to fasted state can be avoided by using SEP.

Nanoemulsion formation and characterization by spontaneous emulsification: Investigation of its antibacterial effects on Listeria monocytogenes

Atransparent oil‐in‐water nanoemulsion system consisting of eucalyptus oil, Tween‐20 as organic phase and water as an aqueous phase was developed using a low energy emulsification method. Physicochemical properties such as droplet size, optical transparency, and long‐term stability was studied. The stable eucalyptus oil nanoemulsion (1:2) having mean droplet size in the range of 50-100 nm with a polydispersity index <0.2. The optimized nanoemulsion formulation exhibited significantly higher antibacterial activity by the well diffusion method against Listeria monocytogenes. Further, alteration in the membrane integrity was assessed, and it is found higher for nanoemulsion treated cells than control cells. Atomic force microscopic observations showed distorted morphology of treated bacterial cells. These results propose the possible use of eucalyptus oil nanoemulsion in the food industries. Key words: Antibacterial, eucalyptus oil, Listeria monocytogenes, nanoemulsion, spontaneous emulsification

Potential of Spontaneous Emulsification Flooding for Enhancing Oil Recovery in High-Temperature and High-Salinity Oil Reservoir

Emulsification tests and oil/water interfacial tension measurements were made to develop an alkali/surfactant spontaneous emulsification system to adapt the high-temperature and high-salinity in Shengtuo reservoir; also, oil displacement efficiency under different shear strength was investigated by a sandpack flood test. The results showed that the interfacial tension of oil/water could be lowered to an ultra-low level by a synergistic effect of alkali and surfactant, leading to spontaneous emulsification of oil in brine under condition of porous medium. When shear strength was low, the particle size of the formed emulsion droplet was larger, droplets might coalesce in the pore throat and generate a strong “Jamin” effect, and the mobility ratio of water to oil could be effectively reduced so as to increase the sweep efficiency and oil recovery. The particle size of the emulsion decreased with an increase of the shear strength, and emulsion droplets were insufficient to plug the water channel effectively and were entrained out of the formation with the displacing fluid due to the limited capability of reducing the water-to-oil mobility ratio, which resulted in lower oil displacement efficiency. Therefore, the entrapment of emulsion droplets was the main mechanism to enhance recovery, and oil recovery could be improved by reducing shear strength during flooding.