Colloidal Disperse Systems: Microemulsions and Nanoemulsions

Micro- and nanoemulsions are disperse systems widely used for the efficient and targeted drug delivery through various routes of administration. The difference between micro- and nanoemulsions is not related to the size scale, as the names suggest, since both systems might contain droplets with a diameter lower than 100 nm. The main difference between these two systems is that the droplet size of nanoemulsions is obtained by a mechanical reducing method, while microemulsions are formed spontaneously. Thus, microemulsions are thermodynamically and physically stable systems while nanoemulsions are susceptible to Ostwald ripening, one of the main causes of physical instability. In this chapter, the two systems will be presented and compared. Their composition, preparation, and characterization methods will be discussed, and some examples of formulations and medicines that include micro- and nanoemulsions will be presented.