Formation of fine emulsions by emulsification at high viscosity or low interfacial tension; A comparative study

Synthesis of eco-friendly layered double hydroxide and nanoemulsion for jasmine and peppermint oils and their larvicidal activities against Culex pipiens Linnaeus

Mosquito-borne diseases represent a growing health challenge over time. Numerous potential phytochemicals are target-specific, biodegradable, and eco-friendly. The larvicidal activity of essential oils, a jasmine blend consisting of Jasmine oil and Azores jasmine (AJ) (Jasminum sambac and Jasminum azoricum) and peppermint (PP) Mentha arvensis and their nanoformulations against 2nd and 4th instar larvae of Culex pipiens, was evaluated after subjecting to different concentrations (62.5, 125, 250, 500, 1000, and 2000 ppm). Two forms of phase-different nanodelivery systems of layered double hydroxide LDH and oil/water nanoemulsions were formulated. The synthesized nanoemulsions showed particle sizes of 199 and 333 nm for AJ-NE and PP-NE, with a polydispersity index of 0.249 and 0.198, respectively. Chemical and physiochemical analysis of TEM, SEM, XRD, zeta potential, drug loading capacity, and drug release measurements were done to confirm the synthesis and loading efficiencies of essential oils' active ingredients. At high concentrations of AJ and PP nanoemulsions (2000 ppm), O/W nanoemulsions showed higher larval mortality than both LDH conjugates and crude oils. The mortality rate reached 100% for 2nd and 4th instar larvae. The relative toxicities revealed that PP nanoemulsion (MA-NE) was the most effective larvicide, followed by AJ nanoemulsion (AJ-NE). There was a significant increase in defensive enzymes, phenoloxidase, and α and β-esterase enzymes in the treated groups. After treatment of L4 with AJ, AJ-NE, PP, and PP-NE, the levels of phenoloxidase were 545.67, 731.00, 700.00, and 799.67 u/mg, respectively, compared with control 669.67 u/mg. The activity levels of α-esterase were 9.71, 10.32, 8.91, and 10.55 mg α-naphthol/min/mg protein, respectively. It could be concluded that the AJ-NE and PP-NE nanoformulations have promising larvicidal activity and could act as safe and effective alternatives to chemical insecticides.

Coencapsulation of Polyphenols and Anthocyanins from Blueberry Pomace by Double Emulsion Stabilized by Whey Proteins: Effect of Homogenization Parameters

Blueberry pomace is a rich source of high-value bioactive polyphenols with presumed health benefits. Their incorporation into functional foods and health-related products benefits from coencapsulation and protection of polyphenol-rich extracts in suitable carriers. This study aimed to create a water-in-oil-in-water (W₁/O/W₂) double emulsion system suitable for the coencapsulation of total phenolics (TP) and anthocyanins (TA) from a polyphenol-rich extract of blueberry pomace (W₁). The effect of critical physical parameters for preparing stable double emulsions, namely homogenization pressure, stirring speed and time, was investigated by measuring the hydrodynamic diameter, size dispersity and zeta potential of the oil droplets, and the encapsulation efficiency of TP and TA. The oil droplets were negatively charged (negative zeta potential values), which was related to the pH and composition of W₂ (whey protein isolate solution) and suggests stabilization by the charged whey proteins. Increasing W₁/O/W₂ microfluidization pressure from 50 to 200 MPa or homogenization speed from 6000 to 12,000 rpm significantly increased droplet diameter and zeta potential and decreased TA and TP encapsulation efficiency. Increasing W₁/O/W₂ homogenization time from 15 to 20 min also increased droplet diameter and zeta potential and lowered TA encapsulation efficiency, while TP encapsulation did not vary significantly. In contrast, increasing W₁/O homogenization time from 5 to 10 min at 10,000 rpm markedly increased TA encapsulation efficiency and reduced droplet diameter and zeta potential. High coencapsulation rates of blueberry polyphenols and anthocyanins around 80% or greater were achieved when the oil droplets were relatively small (mean diameter < 400 nm), with low dispersity (<0.25) and a high negative surface charge (-40 mV or less). These characteristics were obtained by homogenizing for 10 min at 10,000 rpm (W₁/O), then 6000 rpm for 15 min, followed by microfluidization at 50 MPa.

Formulation of oil-in-water emulsions for pesticide applications: impact of surfactant type and concentration on physical stability

Oil-in-water (O/W) emulsions can be utilized as effective pesticide delivery systems in the agricultural industry. In this study, the effects of hydrophile-lipophile balance (HLB), concentration, and location of surfactants on the formation and physical stability of O/W emulsions suitable for pesticide applications was investigated using dynamic light scattering and vertical laser profiling. A non-polar pesticide (lambda-cyhalothrin) was used as a model. The pesticide emulsion with the highest stability was obtained using a commercial non-ionic surfactant (polyoxyethylene castor oil ether, EL-20) with a required HLB value of 10.5. Emulsion stability increased as the surfactant concentration was increased from 2 to 6%, which was attributed to the formation of smaller oil droplets during emulsification. Emulsions prepared with the surfactant initially in the oil phase were more stable than those prepared with it initially in the aqueous phase. The optimum formulation of the pesticide emulsion was determined as follows: 5% lambda-cyhalothrin (active ingredient) and 6% EL-20 (surfactant) dissolved in 5% S-200 (aromatic hydrocarbon, as oil phase), then deionized water up to 100%, which met the quality indicators set by the FAO standards. The present study is expected to provide useful information to improve the stability of pesticide emulsions for commercial applications.

Exotic Vegetable Oils for Cosmetic O/W Nanoemulsions: In Vivo Evaluation

Oil-in-water nanoemulsions are stable systems with droplet sizes in the 20–200 nm range. The physicochemical properties of these systems may be influenced by the addition of additives. Thus, the influence of ethoxylated (EL) and acetylated lanolin (AL) addition on the droplet size, pH values, electrical conductivity and stability of nanoemulsions was investigated. Then, effect of nano-emulsions additives with EL (NE-EL) or AL (NE-AL) in hydration, oiliness and pH of the skin were evaluated. Nanoemulsion safety was evaluated through the observation of no undesirable effects after skin formulation application. Both additives caused changes in droplet size and electrical conductivity, but not in pH values. Nanoemulsions containing up to 6.0% ethoxylated lanolin and 2.0% acetylated lanolin remained stable after centrifugation tests. Higher concentrations of the additives made the nanoemulsions unstable. Stability tests showed that ethoxylated lanolin produced more stable nanoemulsions then acetylated lanolin and that the major instability phenomenon occurring in these systems is coalescence at elevated temperatures. Nanoemulsion-based lanolin derivatives increased skin hydration and oiliness and did not change cutaneous pH values. These formulations are non-toxic since they did not cause any irritation on the skin surface after nanoemulsion application, showing potential as carriers for pharmaceuticals and cosmetic applications.

Physicochemical and functional properties of gelatins extracted from turkey and chicken heads

Gelatins were prepared from chicken and turkey heads in a series of batch extractions at 2 different temperatures (50 and 60°C), and their composition and functional properties were evaluated. Gelatin yield from chicken and turkey heads was 52.29 and 62.76%, respectively, on a dry weight basis relative to the total collagen content in the raw materials. The gel strength of turkey gelatins varied from 332.7 to 368.4 g, which was significantly (P < 0.05) higher than that of chicken gelatins. Both chicken and turkey head gelatins had high solubility at acidic and alkaline pH values. However, turkey head gelatins showed better emulsifying and foaming properties compared with chicken gelatins.

Comparison between gelatines extracted from mackerel and blue whiting bones after different pre-treatments

Gelatines were extracted from mackerel and blue whiting bones after chemical or enzymatic pre-treatments and their functional properties (solubility, foaming and emulsifying properties) were analysed. The pre-treatment significantly (p<0.05) affected the composition and the functional properties of the extracted gelatines. The amino acid analyses showed that chemically pre-treated bone gelatines had higher imino acids (proline and hydroxyproline) contents compared to those extracted after the enzymatic pre-treatment, for both fish species. It was observed that all gelatines had higher solubility at low pH with a maximum value observed at pH 2. A significant effect of ionic strength was observed. Increasing the NaCl concentration to more than 1% resulted in a significant decrease of the solubility. Mackerel bone gelatines showed lower foaming capacity (FC) and higher foaming stability (FS) than blue whiting bone gelatines. Increasing the concentration of gelatine decreased the emulsifying activity index (EAI) but increased the stability index (ESI). The use of enzymes in the pre-treatment process gave gelatines with significantly (p<0.05) higher EAI and ESI.

Efficient emulsification of viscous oils at high drop volume fraction

It is shown experimentally in this study that the increase of drop volume fraction can be used as an efficient tool for emulsification of viscous oils in turbulent flow. In a systematic series of experiments, the effects of drop volume fraction and viscosity of the dispersed phase on the mean, d(32), and maximum, d(V95), diameters of the drops, formed during emulsification, are quantified. The volume fraction, Φ, of the dispersed oily phase is varied between 1% and 90%, and oils with viscosity varying between 3 and 10,000 mPa.s are studied. All experiments are performed at sufficiently high surfactant concentration, as to avoid possible drop-drop coalescence during emulsification. The analysis of the experimental data shows that there is a threshold drop volume fraction, Φ(TR), at which a transition from inertial turbulent regime into viscous turbulent regime of emulsification occurs, due to the increased overall viscosity of the emulsion. At Φ < Φ(TR), d(32) and d(V95) depend weakly on Φ and are well described by known theoretical expression for emulsification in inertial turbulent regime (Davies, Chem. Eng. Sci. 1985, 40, 839), which accounts for the effects of oil viscosity and interfacial tension. At Φ > Φ(TR), both d(32) and polydispersity of the formed emulsions decrease very significantly with the increase of Φ (for the oils with η(D) > 10 mPa.s). Thus, very efficient emulsification of the viscous oils is realized. Very surprisingly, a third regime of emulsification is observed in the range of concentrated emulsions with Φ > 75%, where the mean drop size and emulsion polydispersity are found experimentally to be very similar for all oils and surfactants studied-an experimental fact that does not comply with any of the existing models of drop breakup during emulsification. Possible mechanistic explanations of this result are discussed. The experimental data for semiconcentrated and concentrated emulsions with Φ > Φ(TR) are described by a simple scaling expression, which accounts for the effects of all main factors studied.

Terpene microemulsions for transdermal curcumin delivery: effects of terpenes and cosurfactants

Microemulsion systems composed of terpenes, polysorbate 80, cosurfactants, and water were investigated as transdermal delivery vehicles for curcumin. Pseudoternary phase diagrams of three terpenes (limonene, 1,8-cineole, and α-terpineol) at a constant surfactant/cosurfactant ratio (1:1) were constructed to illustrate their phase behaviors. Limonene combined with cosurfactants like ethanol, isopropanol, and propylene glycol were employed as microemulsion ingredients to study their potential for transdermal curcumin delivery. The transdermal delivery efficacy and skin retention of curcumin were evaluated using neonate pig skin mounted on a Franz diffusion cell. The curcumin permeation rates in the limonene microemulsion studied were 30- and 44-fold higher than those of 1,8-cineole and α-terpineol microemulsions, respectively. Significant effects on the skin permeation rates were observed from microemulsions containing different limonene/water contents. Histological examination of treated skin was performed to investigate the change of skin morphologies. Characteristics such as droplet size, conductivity, interfacial tension, and viscosity were analyzed to understand the physicochemical properties of the transdermal microemulsions. In conclusion, microemulsions loaded with curcumin were successfully optimized for transdermal delivery after screening various terpenes, cosurfactants, and limonene/water ratios. These results indicate that the limonene microemulsion system is a promising tool for the percutaneous delivery of curcumin.