Magnetic Nanoemulsions: Comparison between Nanoemulsions Formed by Ultrasonication and by Spontaneous Emulsification

Nanoemulsions are particularly suitable as a platform in the development of delivery systems. The type of nanoemulsion with a higher stability will offer an advantage in the preparation of a delivery system for lipophilic drugs. Nanoemulsions can be fabricated by different processing methods, which are usually categorized as either high- or low-energy methods. In this study, a comparison between two methods of preparing magnetic oil-in-water (O/W) nanoemulsions is described. The nanoemulsions were formed by sonication (the high-energy method) or by spontaneous emulsification (the low-energy method). In both cases, the oil phase was olive oil, and a phospholipid and a pegylated phospholipid were used as emulsifiers. To favor the comparison, the amounts of the components were the same in both kinds of nanoemulsions. Moreover, nanoemulsions were loaded with hydrophobic superparamagnetic nanoparticles and indomethacin. In vitro, releases studies indicated a short drug burst period followed by a prolonged phase of dissolutive drug release. The Korsmeyer-Peppas model can fit the associated kinetics. The results showed that such nanoemulsions are suitable as a platform in the development of delivering systems for lipophilic drugs. The long-term stability was also examined at different temperatures, as well as the interaction with plasma proteins. Nanoemulsion obtained by the low-energy method showed a great stability at 4 °C and at ambient temperature. Its size and polydispersity did not change over more than two months. The spontaneous emulsification method therefore has great potential for forming nanoemulsion-based delivery systems.