A Detailed Comprehensive Review of Multiple Nanoemulsions on Pharmaceutical Applications

Biphasic systems, composed of two immiscible liquid phases such as oil and water, are extensively utilized for the transportation of both hydrophilic and hydrophobic substances. Emulsions, particularly nanoemulsions, have attracted notable interest due to their tiny droplet sizes (≤100nm), improved dispersion characteristics, and enhanced kinetic stability. In contrast to thermodynamically stable microemulsions, nanoemulsions are in a metastable state, which allows for increased formulation possibilities and higher concentration of additives. These attributes render them highly adaptable for application in drug delivery, cosmetics, and material science. Advancing the functionality of nanoemulsions, multiple emulsions, which contain immiscible droplets encapsulated within other droplets (for example, water-in-oil-in-water), present the distinct benefits of being able to co-encapsulate both hydrophilic and lipophilic compounds. Nonetheless, traditional multiple emulsions frequently experience challenges with poor physical stability and low encapsulation efficiency. To address these issues, multiple nanoemulsions have been created, merging the advantages of both multiple emulsions and nanoemulsions. These systems, typically featuring droplet sizes ranging from 20-200nm, demonstrate improved kinetic stability, enhanced encapsulation efficiency, minimized creaming, and favorable controlled release profiles. They are particularly advantageous in pharmaceuticals, neutraceuticals, and cosmetic sectors where high bioavailability and effective performance are essential. This review presents a thorough examination of multiple nanoemulsions, detailing their structural type, mechanism of formation, preparation methods, characterization techniques, and various applications. The progress of these systems signifies a promising path in the fields of drug delivery and multifunctional formulation science.