The effects of emulsifier type,phase ratio,and homogenization methods on stability of the double emulsion

The double emulsion technology has a potential effect on the development of diversity and quality of functional foods by means of decreasing oil or salt concentration, encapsulating and controlling release of valuable components. In this study, it was aimed to formulate stable double emulsions to be used in food systems. W1/O ratios of primary emulsions, stabilized by polyglycerol polyricinoleate (PGPR), were designed as 2:8 and 4:6, and (W1/O)/W2 ratios of the double emulsions were used as 2:8 and 4:6. W/O/W phase ratios, homogenization methods applied to primary emulsion (high-speed homogenization, ultrasonic homogenization), and emulsifier types used in W2 phase [sodium caseinate (SC), xanthan gum, lecithin-whey protein concentrate] were used as independent variables. Particle size and distributions, stability, encapsulation efficiency (EE), rheological properties, long-term stability, and morphological properties of the double emulsions were investigated.

The double emulsions prepared with SC and (W1/O)/W2 ratio of 4:6, were found to have the higher stability values, higher apparent viscosity, and lower particle size. High-speed homogenization applied to primary emulsion reduced particle size of the double emulsion and increased apparent viscosity, but did not affect stability and EE of the double emulsions, significantly.     

Release of electrolytes from W/O/W double emulsions stabilized by a soluble complex of modified pectin and whey protein isolate

W/O/W double emulsions (DEs) stabilized by charged soluble complexes of whey protein isolate (WPI) and modified pectins were investigated in relation to their stability and the release of two types of electrolytes, NaCl and sodium ascorbate.WPI alone cannot properly stabilize the DEs. The droplet size is relatively large (100 μm) and increases with time. However, addition of modified pectin to form a soluble complex with WPI significantly improved the stability.DEs prepared with two types of oils (medium chain triglycerides (MCT) and R(+)-limonene) were studied by measuring droplet size, creaming, viscosity, and electrolyte release. Irrespective of their very different oil phase nature, both emulsions were stable against coalescence, but R(+)-limonene formed smaller droplets (25 μm) than MCT (35 μm). The electrolyte release rate was significantly higher from the R(+)-limonene that formed DEs with much lower viscosity. R(+)-limonene-DE released 75% of the NaCl after 28 days, while MCT-DE released only 50%. NaCl was released more slowly than sodium ascorbate.Apparently, the release mechanism from R(+)-limonene-DE was found to be “thinning the outer interface and release of the entire inner droplets” while it seems that the release from MCT-DE was slower and “diffusion controlled”.DEs stabilized by WPI/C63 released 12% of the sodium ascorbate after 1 day in milk and remained stable for at least 8 days. However, DEs stabilized with only WPI released about 50% of the sodium ascorbate after 1 day, and phase separated after 8 days.     

Development of a Microfluidic Formatted Ultrasound-Controlled Monodisperse Lipid Vesicles' Hydrogel Dressing Combined with Ultrasound for Transdermal Drug Delivery System

Transdermal drug delivery system (TDDS) has attracted much attention in the pharmaceutical technology area. However, the current methods are difficult to ensure penetration efficiency, controllability, and safety in the dermis, so its widespread clinical use has been limited. This work proposes an ultrasound-controlled monodisperse lipid vesicles (U-CMLVs) hydrogel dressing, which combines with ultrasound to form TDDS. Using microfluidic technology, prepare size controllable U-CMLVs with high drug encapsulation efficiency and quantitative encapsulation of ultrasonic response materials, and even uniform mix them with hydrogel to prepare the required thickness of dressings. The high encapsulation efficiency can ensure sufficient dosage of the drugs and further realize the control of ultrasonic response through quantitative encapsulation of ultrasound-responsive materials. Using high frequency (5 MHz, 0.4 W cm⁻²) and low frequency (60 kHz, 1 W cm⁻²) ultrasound to control the movement and rupture of U-CMLVs, the contents not only penetrate the stratum corneum into the epidermis but also break through the bottleneck of penetration efficiency, and deep into the dermis. These findings provide the groundwork for deep, controllable, efficient, and safe drug delivery through TDDS and lay a foundation for further expanding its application.     

Surfactant-Free Multiple Pickering Emulsions Stabilized by Combining Hydrophobic and Hydrophilic Nanoparticles

A series of W/O/W or O/W/O emulsion stabilized solely by two different types of solid nanoparticles were prepared by a two-step method. We explored the option of particular emulsifiers for the multiple Pickering emulsions, and a variety of nanoparticles (silica, iron oxide, and clay) only differing in their wettability was used. The primary W/O emulsion was obtained by the hydrophobic nanoparticles, and then the hydrophilic nanoparticles were used as emulsifier in the secondary emulsification to prepare the W/O/W emulsion. In a similar way, the primary O/W emulsion of the O/W/O emulsion was stabilized by the hydrophilic nanoparticles, while the secondary emulsification to prepare the O/W/O emulsion was effected with the hydrophobic nanoparticles. The resultant multiple Pickering emulsion was stable to coalescence for more than 3 months, except the W/O/W emulsions of which the secondary emulsion stabilized by clay nanoparticles became a simple O/W emulsion in a day after preparation. Moreover, the temperature and pH sensitive poly(N-isopropylacrylamide-co-methacrylic acid) (P(NIPAm-co-MAA)) microgels were introduced as an emulsifier for the secondary emulsification to obtain the stimulus-responsive multiple W/O/W emulsion. Such microgel-stabilized multiple emulsions could realize the efficient controlled release of water-soluble dye, Rhodamine B (RB) on demand in a multiple-emulsion delivery system.      

Controlling the stability and size of double-emulsion-templated poly(lactic-co-glycolic) acid microcapsules

The stability and size of poly(lactic-co-glycolic)acid (PLGA)-containing double emulsions and the resulting PLGA microcapsules are controlled by varying the composition of highly monodisperse water-in-oil-in-water (W/O/W) double emulsions. We propose that the basic inner phase of W/O/W double emulsions catalyzes the hydrolysis of PLGA and the ionization of carboxylic acid end groups, which enhances the surface activity of PLGA and facilitates the stabilization of the double emulsions. The size of PLGA-containing double emulsions and that of resulting microcapsules can be readily tuned by osmotic annealing, which depends on the concentration ratio of a solute in the inner and outer phases of double emulsions. The internal volume of PLGA microcapsules can be changed by more than 3 orders of magnitude using this method. This approach also overcomes the difficulty in generating monodisperse double emulsions and microcapsules over a wide range of dimensions using a single microfluidic device. The osmotic annealing method can also be used to concentrate encapsulated species such as colloidal suspensions and biomacromolecules.     

Preparation and characterization of W/O/W double emulsions containing MgCl2

The aim of present study is to design food-grade W/O/W double emulsions encapsulating Mg²⁺ and investigate their stability and release properties. Prepared emulsions were characterized in terms of global stability, particle size, rheological properties, and interfacial tension. The double emulsions were sensitive to the presence of magnesium salt. The mean droplet size and viscosity of emulsions was positively correlated to MgCl₂ concentration. The microscopic pictures confirmed that the water transfer between two aqueous phases caused the reduced stability of double emulsions. It was suggested that swelling breakdown was the main mechanism in controlling the release of encapsulated Mg²⁺.     

Invert and double emulsions as a base for microheterogeneous matrices for transdermal delivery of lipophilic drugs

Stable invert emulsions water/oil and double emulsions oil₁/water/oil₂ containing polyisobuthylene as pressure-sensitive polymeric adhesive are prepared. The dispersed phase of the invert emulsions contained micelles of the surfactant Tween 80 (Tw) with solubilized drug (Felodipine) and a skin permeation enhancer (glycerol monooleate, GMO). The active components (Felodipine and GMO) of the double emulsions were incorporated into the internal dispersed phase, while the intermediate water layer contained Tw and hydroxypropylcellulose. Ultradispersed polymer films with good adhesion to skin were prepared from both types of emulsions. The films based on double emulsions demonstrate the ability to release Felodipine at therapeutically effective levels and maintain these levels during the first 24 h to attain a therapeutically required dose. The invert and double emulsions were for the first time utilized as bases for microheterogeneous matrices for delivery of a lipophilic drug in bioavailable form.     

Controlled Release of a Sparingly Water‐Soluble Anticancer Drug through pH‐Responsive Functionalized Gold‐Nanoparticle‐Decorated Liposomes

The binding and detachment of carboxyl‐modified gold nanoparticles from liposomes is used for controlled drug delivery. This study reveals that the binding and detachment of nanoparticles from liposomes depends on the degree of hydration of the liposomes. Liposomes with a lower hydration level undergo stronger electrostatic interactions with negatively charged gold nanoparticles, thus leading to a slower detachment of the carboxyl‐modified gold nanoparticles under gastric conditions. Therefore, under gastric conditions, gold‐nanoparticle‐decorated dipalmitoylphosphatidylcholine (DPPC) liposomes exhibit an at least ten‐times‐slower drug release compared to gold‐nanoparticle‐decorated 1,2‐dimyristoyl‐sn‐glycero‐3‐phosphocholine (DMPC) liposomes, although both liposomes in the bare state fail to pursue controlled release. Our study also reveals that one can modulate the drug‐release rate by simply varying the concentration of nanoparticles. This study highlights a novel strategy for the controlled release of drug molecules from liposomes.     

Lipid vesicles as possible intermediates in the origin of life

Lipid vesicles (liposomes) are closed structures in which (at least) one lipid bilayer separates an aqueous inner compartment from the bulk external aqueous medium, as in membranes of contemporary biological cells. Lipid vesicles have therefore been considered as possible cell precursors during the prebiological era on Earth. Recently, it has been shown that lipid vesicles form spontaneously. Furthermore, it has been demonstrated that thermodynamically controlled peptide binding to and controlled polymerization reactions on vesicles are possible, thus leading to an increase in the molecular complexity of lipid vesicles. This may have been relevant during the prebiological evolution. © 1999 Elsevier Science Ltd.     

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.     

Temperature-induced protein release from water-in-oil-in-water double emulsions

A model water-in-oil-in-water (W1/O/W2) double emulsion was prepared by a two-step emulsification procedure and subsequently subjected to temperature changes that caused the oil phase to freeze and thaw while the two aqueous phases remained liquid. Our previous work on individual double-emulsion globules1 demonstrated that crystallizing the oil phase (O) preserves stability, while subsequent thawing triggers coalescence of the droplets of the internal aqueous phase (W1) with the external aqueous phase (W2), termed external coalescence. Activation of this instability mechanism led to instant release of fluorescently tagged bovine serum albumin (fluorescein isothiocyanate (FITC)-BSA) from the W 1 droplets and into W2. These results motivated us to apply the proposed temperature-induced globule-breakage mechanism to bulk double emulsions. As expected, no phase separation of the emulsion occurred if stored at temperatures below 18 degrees C (freezing point of the model oil n-hexadecane), whereas oil thawing readily caused instability. Crucial variables were identified during experimentation, and found to greatly influence the behavior of bulk double emulsions following freeze-thaw cycling. Adjustment of these variables accounted for a more efficient release of the encapsulated protein.     

Pharmaceutical Development and Design of Thermosensitive Liposomes Based on the QbD Approach

This study aimed to produce thermosensitive liposomes (TSL) by applying the quality by design (QbD) concept. In this paper, our research group collected and studied the parameters that significantly impact the quality of the liposomal product. Thermosensitive liposomes are vesicles used as drug delivery systems that release the active pharmaceutical ingredient in a targeted way at ~40–42 °C, i.e., in local hyperthermia. This study aimed to manufacture thermosensitive liposomes with a diameter of approximately 100 nm. The first TSLs were made from DPPC (1,2-dipalmitoyl-sn-glycerol-3-phosphocholine) and DSPC (1,2-dioctadecanoyl-sn-glycero-3-phosphocholine) phospholipids. Studies showed that the application of different types and ratios of lipids influences the thermal properties of liposomes. In this research, we made thermosensitive liposomes using a PEGylated lipid besides the previously mentioned phospholipids with the thin-film hydration method.     

A Comparison Investigation of Coix Seed Oil Liposomes Prepared by Five Different Methods

The physicochemical properties of coix seed oil (CSO) liposomes prepared by five different methods were evaluated for morphology, encapsulating efficiency, particle size, storage stability, and in vitro release. The different preparation methods resulted in several types of vesicles with different properties. The type of vesicles was closely related to leakage pattern, which affected the storage stability and in vitro release profiles. Ethanol injection method was the best choice for preparing safe and stable liposomes with controlled release. The release mechanisms might account for the diffusion of CSO, and Higuchi was the most suitable model for liposomes stored at high temperature or released in simulated intestinal fluid (SIF).     

Microcalorimetric studies of the effects of artesunate liposomes on the metabolism of <Emphasis Type="Italic">Escherichia coli</Emphasis> during growth

A thermal dynamic model of nanoformulations entrapped in artesunate liposomes was established and biological thermodynamics was applied for investigation of the drug formulations. Effects of artesunate liposomes on the growth metabolism of Escherichia coli were studied by microcalorimetry. The results showed that (1) Comparison of artesunate and artesunate liposomes, the thermogenesis curves of E. coli were significant different in the metabolic process: lag phase (AB), log phase (BC), stationary phase (CD), and decline phase (DE); (2) Linear fit of the data of total metabolic heat of E. coli effected by different concentration artesunate (1–300 μg), the equation can be obtained as follows: Y = 364720.61−1075.25x, R = 0.9985; Linear fit of the data of total metabolic heat of E. coli effected by different concentration artesunate liposomes (30–120 μg), the linear equation can be obtained as follows: Y = 54251.5765−35.71122x, R = 0.98345; (3) The half inhibitory concentration I _C50 was 50.05 μg/mL, the relative sensitivity was obviously different; (4) Artesunate liposomes having better sustained release properties as compare to artesunate.     

Formulation of Piperine–Chitosan-Coated Liposomes: Characterization and In Vitro Cytotoxic Evaluation

The present research work is designed to prepare and evaluate piperine liposomes and piperine–chitosan-coated liposomes for oral delivery. Piperine (PPN) is a water-insoluble bioactive compound used for different diseases. The prepared formulations were evaluated for physicochemical study, mucoadhesive study, permeation study and in vitro cytotoxic study using the MCF7 breast cancer cell line. Piperine-loaded liposomes (PLF) were prepared by the thin-film evaporation method. The selected liposomes were coated with chitosan (PLFC) by electrostatic deposition to enhance the mucoadhesive property and in vitro therapeutic efficacy. Based on the findings of the study, the prepared PPN liposomes (PLF3) and chitosan coated PPN liposomes (PLF3C1) showed a nanometric size range of 165.7 ± 7.4 to 243.4 ± 7.5, a narrow polydispersity index (>0.3) and zeta potential (−7.1 to 29.8 mV). The average encapsulation efficiency was found to be between 60 and 80% for all prepared formulations. The drug release and permeation study profile showed biphasic release behavior and enhanced PPN permeation. The in vitro antioxidant study results showed a comparable antioxidant activity with pure PPN. The anticancer study depicted that the cell viability assay of tested PLF3C2 has significantly (p < 0.001)) reduced the IC₅₀ when compared with pure PPN. The study revealed that oral chitosan-coated liposomes are a promising delivery system for the PPN and can increase the therapeutic efficacy against the breast cancer cell line.     

Stealth Liposomes (PEGylated) Containing an Anticancer Drug Camptothecin: In Vitro Characterization and In Vivo Pharmacokinetic and Tissue Distribution Study

Numerous attempts to overcome the poor water solubility of cam ptothecin (CPT) by various nano drug delivery systems are described in various sources in the literature. However, the results of these approaches may be hampered by the incomplete separation of free CPT from the formulations, and this issue has not been investigated in detail. This study aimed to promote the solubility and continuous delivery of CPT by developing long-lasting liposomes using various weights (M.W. 2000 and 5000 Daltons) of the hydrophilic polymer polyethylene glycol (PEG). Conventional and PEGylated liposomes containing CPT were formulated via the lipid film hydration method (solvent evaporation) using a rotary flash evaporator after optimising various formulation parameters. The following physicochemical characteristics were investigated: surface morphology, particle size, encapsulation efficiency, in vitro release, and formulation stability. Different molecular weights of PEG were used to improve the encapsulation efficiency and particle size. The stealth liposomes prepared with PEG₅₀₀₀ were discrete in shape and with a higher encapsulation efficiency (83 ± 0.4%) and a prolonged rate of drug release (32.2% in 9 h) compared with conventional liposomes (64.8 ± 0.8% and 52.4%, respectively) and stealth liposomes containing PEG₂₀₀₀ (79.00 ± 0.4% and 45.3%, respectively). Furthermore, the stealth liposomes prepared with PEG₅₀₀₀ were highly stable at refrigeration temperature. Significant changes were observed using various pharmacokinetic parameters (mean residence time (MRT), half-life, elimination rate, volume of distribution, clearance, and area under the curve) of stealth liposomes containing PEG₂₀₀₀ and PEG₅₀₀₀ compared with conventional liposomes. The stealth liposomes prepared with PEG₅₀₀₀ showed promising results with a slow rate of release over a long period compared with conventional liposomes and liposomes prepared with PEG₂₀₀₀, with altered tissue distribution and pharmacokinetic parameters.     

Glucose-triggered release from liposomes incorporating poly(<Emphasis Type="Italic">N</Emphasis>-isopropylacrylamide-co-methacrylic acid-co-octadecylacrylate) and glucose oxidase

In order to design liposomes which release their contents in a glucose-sensitive manner, the surfaces of egg phosphatidylcholine (egg PC) liposomes or dioleoylphosphatidylethanolamine (DOPE) liposomes were modified with the copolymer of N-isopropylacrylamide/methacrylic acid/octadecylacrylate and hydrophobically modified glucose oxidase (EC 1.1.3.4.). Whichever the liposomes were prepared with egg PC or DOPE, an extensive release of calcein was observed at acidic conditions. And DOPE liposomes were more pH sensitive than egg PC liposomes in terms of the release. In glucose-dependent calcein release experiment, there was no release for 180 min when the suspension of liposome was free of glucose. When the glucose concentration was 50 mg/dl, no appreciable amount of calcein was released for the first 50 min, but a significant release was observed for the last 130 min. At glucose concentration of 200 mg/dl, calcein release became more extensive and the releases for 180 min from egg PC and DOPE liposome were 84% and 98%, respectively.     

Efficient formation of giant liposomes through the gentle hydration of phosphatidylcholine films doped with sugar

Giant liposomes, or giant vesicles, are cell-size (approximately 5-100 microm) compartments enclosed with phospholipid bilayers, and have often been used in biological research. They are usually generated using hydration methods, "electroformation" and "gentle hydration (or natural swelling)", in which dry lamellar films of phospholipids are hydrated with aqueous solutions. In gentle hydration, however, giant liposomes are difficult to prepare from an electrostatically neutral phospholipid because lipid lamellae cannot repel each other. In this study, we demonstrate the efficient formation of giant liposomes using the gentle hydration of neutral phospholipid (dioleoyl phosphatidylcholine, DOPC) dry films doped with nonelectrolytic monosaccharides (glucose, mannose, and fructose). A mixture of DOPC and such a sugar in an organic solvent (chloroform/methanol) was evaporated to form the films, which were then hydrated with distilled water or Tris buffers containing sodium chloride. Under these conditions, giant liposomes spontaneously formed rapidly and assumed a swollen cell-sized spherical shape with low lamellarity, whereas giant liposomes from pure DOPC films had multilamellar lipid layers, miscellaneous shapes and smaller sizes. This observation indicates that giant unilamellar vesicles (GUVs) of DOPC can be obtained efficiently through the gentle hydration of sugar-containing lipid dry films because repulsion between lipid lamellae is enhanced by the osmosis induced by dissolved sugar.     

Formulation of Isopropyl Isothiocyanate Loaded Nano Vesicles Delivery Systems: In Vitro Characterization and In Vivo Assessment

Isopropyl Isothiocyanate (IPI) is a poorly water-soluble drug used in different biological activities. So, the present work was designed to prepare and evaluate IPI loaded vesicles and evaluated for vesicle size, polydispersity index (PDI) and zeta potential, encapsulation efficiency, drug release, and drug permeation. The selected formulation was coated with chitosan and further assessed for the anti-platelet and anti-thrombotic activity. The prepared IPI vesicles (F3) exhibited a vesicle size of 298 nm ± 5.1, the zeta potential of −18.7 mV, encapsulation efficiency of 86.2 ± 5.3% and PDI of 0.33. The chitosan-coated IPI vesicles (F3C) exhibited an increased size of 379 ± 4.5 nm, a positive zeta potential of 23.5 ± 2.8 mV and encapsulation efficiency of 77.3 ± 4.1%. IPI chitosan vesicle (F3C) showed enhanced mucoadhesive property (2.7 folds) and intestinal permeation (~1.8-fold) higher than IPI vesicles (F3). There was a significant (p < 0.05) enhancement in size, muco-adhesion, and permeation flux achieved after coating with chitosan. The IPI chitosan vesicle (F3C) demonstrated an enhanced bleeding time of 525.33 ± 12.43 s, anti-thrombin activity of 59.72 ± 4.21, and inhibition of platelet aggregation 68.64 ± 3.99%, and anti-platelet activity of 99.47%. The results of the study suggest that IPI chitosan vesicles showed promising in vitro results, as well as improved anti-platelet and anti-thrombotic activity compared to pure IPI and IPI vesicles.     

Vesicular release dynamics are altered by the interaction between the chemical cargo and vesicle membrane lipids

The release of the cargo from soft vesicles, an essential process for chemical delivery, is mediated by multiple factors. Among them, the regulation by the interaction between the chemical cargo species and the vesicular membrane, widely existing in all vesicles, has not been investigated to date. Yet, these interactions hold the potential to complicate the release process. We used liposomes loaded with different monoamines, dopamine (DA) and serotonin (5-HT), to simulate vesicular release and to monitor the dynamics of chemical release from isolated vesicles during vesicle impact electrochemical cytometry (VIEC). The release of DA from liposomes presents a longer release time compared to 5-HT. Modelling the release time showed that DA filled vesicles had a higher percentage of events where the time for the peak fall was better fit to a double exponential (DblExp) decay function, suggesting multiple kinetic steps in the release. By fitting to a desorption–release model, where the transmitters adsorbed to the vesicle membrane, the dissociation rates of DA and 5-HT from the liposome membrane were estimated. DA has a lower desorption rate constant, which leads to slower DA release than that observed for 5-HT, whereas there is little difference in pore size. The alteration of vesicular release dynamics due to the interaction between the chemical cargo and vesicle membrane lipids provides an important mechanism to regulate vesicular release in chemical and physiological processes. It is highly possible that this introduces a fundamental chemical regulation difference between transmitters during exocytosis.

The release of the cargo from soft vesicles, an essential process for chemical delivery, is mediated by multiple factors.