Nanoemulsions; preparation, characterization and applications

Insolubility of the nonpolar compounds in water causes some problems and limitations including their lower bioavailability and mixing in the aqueous formulations. In addition to, the nonpolar components are more sensitive to oxygen and lights and their properties drastically reduce when they expose to the air. Nanoemulsions are one of the main finding of the researchers to increase the stability of these types of components in the water and to decrease their sensitive in the environment. Nanoemulsions contain two immiscible phases which droplets of a phase are disperses in another one [1]. There are two basic types of nanoemulsions most likely to be formed depending on the composition that is oil-in-water (O/W) or water-in-oil (W/O) [2]. Nowadays, several methods for preparing nanoemulsions are available. They can be produced using both low-energy, in which a change of curvature and a phase transition takes place during the emulsification process and high-energy protocols that consist of the application of high mechanical energy during emulsification e.g., high pressure homogenization or microfluidization. Several techniques has been used for characterization of nanoemulsions. The morphology of the nanoparticles is studied by TEM, SEM and AFM. Bioactive components is measured by HPLC and UV-visible. The specific surface area of nanoemulsion can be measured using the BET analysis [3]. DLS, SEM, FESEM and TEM analysis of the nanoemulsions is performed to determine the droplet size. The surface electrical charge (ζ-potential) on nanoemulsion droplets is measured by using a particle electrophoresis instrument. Nanoemulsions are beneficial for encapsulating, protecting and delivering the poorly water-soluble bioactive components for both functional food and pharmaceutical applications. Nanoemulsions are largely used in the areas of food, cosmetic, paints, reduce waste medicine and pharmaceutics applications [4].