Nanoemulsions: An emerging technology in drug delivery

Abstract

Nanoemulsions are a class of two-phase liquid systems with an internal phase droplet size of less than 200 nm. Although two-phase emulsion systems have been known for decades, the concept of nanoemulsions is fairly recent. Nanoemulsion stability is far more reliable than traditional two-phase "macro"-emulsion systems, which has led to nanoemulsions becoming an attractive option for the delivery of diverse categories of lipophilic small molecule drugs and bioactive agents. This chapter presents an overview of the theories underlying the formulation of emulsions for maximum stability and potential for scale-up. Both low and high energy dispersive techniques have been discussed with suggestions of suitable equipment. Various techniques for formulation have been discussed with specific attention to the nature of the drug and suitability of the excipients. Correlations have been established between stability of nanoemulsions and the nature and concentration of the surfactant, cosurfactant, oil phase, and temperature. A brief section has been devoted to the in vitro characterization of nanoemulsions with reference to instrumentation and techniques used in the pharmaceutical industry. The last part of the chapter is devoted to the application of nanoemulsions in anticancer drug delivery, with examples on how these novel delivery systems can enhance the efficacy of anticancer drugs while significantly reducing the toxic effects of the chemotherapeutic agents.