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The interest around essential oils is constantly increasing thanks to their biological properties exploitable in several fields, from pharmaceuticals to food and agriculture. However, their widespread use and marketing are still restricted due to their poor physico-chemical properties; i.e., high volatility, thermal decomposition, low water solubility, and stability issues. At the moment, the most suitable approach to overcome such limitations is based on the development of proper formulation strategies. One of the approaches suggested to achieve this goal is the so-called encapsulation process through the preparation of aqueous nano-dispersions. Among them, micro- and nanoemulsions are the most studied thanks to the ease of formulation, handling and to their manufacturing costs. In this direction, this review intends to offer an overview of the formulation, preparation and stability parameters of micro- and nanoemulsions. Specifically, recent literature has been examined in order to define the most common practices adopted (materials and fabrication methods), highlighting their suitability and effectiveness. Finally, relevant points related to formulations, such as optimization, characterization, stability and safety, not deeply studied or clarified yet, were discussed.

Nanoemulsions are of great interest in food industry finding various food applications. However, oil-in-water (o/w) nanoemulsions have been intensively investigated, but there are few studies on w/o nanoemulsions. In the present work the preparation of nanoemulsions with olive oil using non-ionic surfactants (Tween 20, 40, 60, 80, Span 20, 80) without the addition of a co-surfactant was studied and their emulsion properties and stability were examined. The stable nanoemulsions were presented in ternary phase diagrams (oil–water-surfactant) for each surfactant and the emulsifying ability of the efficient surfactants was determined. The nanoemulsions properties were evaluated in relationship to compositional components. From the results of this study it can be concluded that stable olive oil nanoemulsions without use of a co-surfactant were obtained and moreover the most efficient type of emulsifier and its ratio of addition in the system were determined.

Microemulsions are one in all the most effective candidates as novel drug delivery system due to their long time period stability, improved drug solubilization with simple preparation and administration. Surfactants and cosurfactants play crucial role to get stable, mild and clinically acceptable microemulsions in their optimized concentration, The main aim of the study to produce an efficient screening approach for the surfactant and cosurfactant selection for the excipients of microemulsion formulation development and to check the consequences of surfactant hydrophilic–lipophilic balance (HLB) as well solubilization stability process in microemulsion. The composition and extent of surfactants and cosurfactants were key variables for physicochemical properties of drug-loaded Microemulsions. The important aspects must be considered for a successful microemulsion process is that the stability of the liquid membrane. This study is an attempt to grasp the mechanism of the effect of the surfactant and chain length of co-surfactants within the microemulsion base formulation stability.

Background The oral route is the most popular route for the clinical administration of drugs to treat various diseases. Before a drug is absorbed into the blood circulation, it must undergo dissolution and permeation. However, most drugs exhibit poor aqueous solubility, and their limited absorption leads to low oral bioavailability. The solubility of hydrophobic drugs can be improved by various ways, such as solid dispersion, salt formation, pH modification, and self-emulsifying drug delivery system (SEDDS) use. Among them, the SEDDS has garnered attention during recent years as it improves oral bioavailability, reduces drug dose, and increases drug protection from unsuitable environment in the gastrointestinal tract. Area covered SEDDS comprises lipid-based formulations. It can solve the problems related to the dissolution and bioavailability of the Biopharmaceutics Classification System Class II and IV drugs. Depending on the preparation procedure, drug-loaded SEDDS can be divided into micro- (SMEDDS) and nano- (SNEDDS) formulations. In this review, we summarize the classification system of lipid formulations, the mechanism underlying improved oral drug absorption by SEDDS, and recent advances in the SEDDS. Expert opinion The SEDDS is a potential formulation for drug delivery. Owing to its small particle size, large surface area, high encapsulation efficiency, and high drug loading, the SEDDS can improve the rate and extent of oral absorption by maximizing drug solubility in the intestinal absorption site. Moreover, because of the lipid-based formulation of SEDDS, it can stimulate and enhance lymphatic transport of drugs to avoid hepatic first-pass metabolism, and thus improve their bioavailability.

Curcumin is a well-known and widely used substance of natural origin. It has also been found to be helpful in the treatment of liver diseases. Unfortunately, curcumin has very low bioavailability and a sensitivity to external agents. Improving these parameters is the subject of many studies. One way to overcome these problems may be to use Phosal® Curcumin as a source of curcumin and encapsulate this dispersion into a nanoemulsion using different types and concentrations of surfactants and co-surfactants, thus manipulating the physicochemical parameters of the nanoemulsion. The present study aimed to develop curcumin-loaded nanoemulsions for intravenous administration and to investigate the effect of Kolliphor HS15 concentration on their critical quality attributes. Methods: Phosal® Curcumin-loaded nanoemulsions with different concentrations of Kolliphor HS15 were prepared by high-pressure homogenization. The effect of Kolliphor HS15 on emulsion physicochemical properties such as mean droplet diameter (MDD), polydispersity index (PDI), zeta potential (ZP), osmolality (OSM), and pH, as well as encapsulation efficiency (EE) and retention rate (RR) of curcumin, were determined. Mid-term stability studies and short-term stress tests were conducted to evaluate the impact of Kolliphor HS15 on the critical quality attributes of the curcumin-loaded nanoemulsions stored under various conditions. Results: Five nanoemulsions with increasing Kolliphor HS15 concentrations were developed. Their MDD ranged from 85.2 ± 2.0 to 154.5 ± 5.1 nm, with a PDI from 0.18 ± 0.04 to 0.10 ± 0.01 and ZP from −15.6 ± 0.7 to −27.6 ± 3.4 mV. Depending on the concentration of Kolliphor HS15, the EE ranged from 58.42 ± 1.27 to 44.98 ± 0.97%. Conclusions: The studied parameters of the developed nanoemulsions meet the requirements for formulations for intravenous administration. Using the appropriate concentration of Kolliphor HS15 allows for a formulation that presents a protective effect against both curcumin and emulsion degradation.

Biomass-derived bio-oil is a sustainable and renewable energy resource, and liquefaction is a potential conversion way to produce bio-oil. Emulsification is a physical upgrading technology, which blends immiscible liquids into a homogeneous emulsion through the addition of an emulsifier. Liquefaction bio-oil from food waste is characterized by its high pour point when compared to diesel fuel. In order to partially replace diesel fuel by liquefaction bio-oil, this study aimed to develop a method to simultaneously extract and emulsify the bio-oil using a commercial surfactant (Atlox 4914, CRODA, Snaith, UK). The solubility and stability of the emulsions at various operating conditions such as the bio-oil-to-emulsifier ratio (B/E ratio), storage temperature and duration, and co-surfactant (methanol) addition were analyzed. The results demonstrate that higher amounts of bio-oil (7 g) and emulsifier (7 g) at a B/E ratio = 1 in an emulsion have a higher solubility (66.48 wt %). When the B/E ratio was decreased from 1 to 0.556, the bio-oil solubility was enhanced by 45.79%, even though the storage duration was up to 7 days. Compared to the emulsion stored at room temperature (25 °C), its storage at 100 °C presented a higher solubility, especially at higher B/E ratios. Moreover, when methanol was added as a co-surfactant during emulsification at higher B/E ratios (0.714 to 1), it rendered better solubility (58.83–70.96 wt %). Overall, the emulsified oil showed greater stability after the extraction-emulsification process.

Microemulsions are nanocolloidal systems composed of water, an oil, and a surfactant, sometimes with an additional co-surfactant, which have found a wide range of practical applications, including the extractive removal of contaminants from polluted water. In this study, microemulsion systems, including a nonionic surfactant (Brij 30), water, and esters selected from two homologous series of C1–C6 alkyl acetates and ethyl C1–C4 carboxylates, respectively, were prepared by the surfactant titration method. Phase transitions leading to the formation of Winsor II and Winsor IV microemulsions were observed and phase diagrams were constructed. The dependences of phase transitions on the salinity and pH and the addition of isopropanol as a co-surfactant were also investigated. Some physical properties, namely density, refractive index, electrical conductivity, dynamic viscosity, and particle size, were measured for a selection of Winsor IV microemulsions, providing further insight into some other phase transitions occurring in the monophasic domains of phase diagrams. Finally, Winsor II microemulsions were tested as extraction solvents for the removal of four tricyclic antidepressant drugs from aqueous media. Propyl acetate/Brij 30/H2O microemulsions provided the best extraction yields (>90%), the highest Nernst distribution coefficients (~40–88), and a large volumetric ratio of almost 3 between the recovered purified water and the resulting microemulsion extract. Increasing the ionic strength (salinity) or the pH of the aqueous antidepressant solutions led to an improvement in extraction efficiencies, approaching 100%. These results could be extrapolated to other classes of pharmaceutical contaminants and suggest ester- and nonionic surfactant-based microemulsions are a promising tool for environmental remediation.

Nebivolol is a third-generation beta-a drenoceptor antagonist. It differs from other beta-a drenoceptor an tagonists as it combines highly selective beta (1)-adrenoceptor antagonist properties with nitric oxide-mediated vasodilator actions and beneficial effects on endothelial function. But this very useful drug use is limited due to challenge of poor water solubility (0.0403 mg/ml). Present study deals with enhancement of solubility of Nebivolol by micro emulsion technique. Various oils, surfactants, and co-surfactants were used to check solubility of Nebivolol. Pseudoternary phase diagrams were constructed using various combinations of ingredients i.e. oil: surfactant: co-surfactant. Micro emulsion batches were prepared by phase titration method. Developed micro emulsion was evaluated for various physicochemical, stability parameters, in-vitro and ex-vivo parameters. Results showed stable micro emulsion form of Nebivolol improved solubility.

The strategy using nonionic microemulsion as a solubilizer for hydrophobic drugs was studied and is demonstrated in this work. The aqueous phase behaviors of mixed nonionic surfactants with various oils at 37 °C are firstly constructed to give the optimal formulations of nonionic microemulsions with applications in the enhanced solubilization of the model hydrophobic drug, paclitaxel, at 37 °C. Briefly, the suitable oil phase with paclitaxel significantly dissolved is microemulsified with appropriate surfactants. Surfactants utilized include Tween 80, Cremophor EL, and polyethylene glycol (4.3) cocoyl ether, while various kinds of edible oils and fatty esters are used as the oil phase. On average, the apparent solubility of paclitaxel is increased to ca. 70–100 ppm in the prepared microemulsions at 37 °C using tributyrin or ethyl caproate as the oil phases. The sizes of the microemulsions attained are mostly from ca. 60 nm to ca. 200 nm. The cytotoxicity of the microemulsion formulations is assessed with the cellular viability of 3T3 cells. In general, the cell viability is above 55% after 24 h of cultivation in media containing these microemulsion formulations diluted to a concentration of total surfactants equal to 50 ppm and 200 ppm.

There has been a resurgence of interest in nano emulsions for diverse pharmaceutical applications considering the fact that low-power emulsification techniques, including spontaneous or self-nano emulsification, have been defined. Self-nano emulsifying drug delivery structures (SNEDDS) are anhydrous homogenous liquid mixtures along with oil, surfactant, drug and co-emulsifier or solubilizer, which spontaneously form oil-in-water nanoemulsion of about 200 nm or less in size upon dilution with water below gentle stirring. The physicochemical properties , drug solubilization ability and physiological targets notably govern the selection of the SNEDDS additives. The composition of the SNEDDS can be optimized with the help of Phase diagrams, whereas statistical experimental design can be used to further optimize SNEDDS. it can improve oral bioavailability of various hydrophobic drugs Cellular uptake is enhanced due to nanosized droplets of SNEDDS.