Review of Nanoemulsion Formulation and Characterization Techniques

Nanoemulsions are colloidal dispersion systems that are thermodynamically stable, composed of two immiscible liquids mixed along with emulsifying agents (surfactants and co-surfactants) to form a single phase. Nanoemulsions have extensively been investigated as drug delivery systems. This review aims to provide consolidated information regarding various formulation and characterization techniques developed for nanoemulsions. Nanoemulsions are formulated using two different methods, the persuasion method and the Brute force method. Various characterization techniques for nanoemulsions include determination of entrapment efficiency, particle size, polydispersity index, zeta potential as well as characterization through differential scanning calorimetry, Fourier-transform infrared spectroscopy and transmission electron microscopy. Nanoemulsions are further evaluated by studying in vitro drug release, in vitro permeation, stability and thermodynamic stability, shelf life, dispersibility, viscosity, surface tension, friccohesity, refractive index, percent transmittance, pH and osmolarity.