Double Emulsions

Abstract

Double emulsions may be either of the water-in-oil-in-water type (W/O/W) (with dispersed oil globules containing smaller aqueous droplets) or of the oil-in-waterin- oil type (O/W/O) (with dispersed aqueous globules containing smaller oily dispersed droplets). Increasing attention has been devoted to these systems with the aim of taking advantage of their double (or multiple) compartment structure. Indeed, double emulsions present many interesting possibilities for the controlled release of chemical substances initially entrapped in the internal droplets. Various industries, including foods and cosmetics, are showing clear interest in the technological development of such complex systems. The field of human pharmaceuticals is the major area of application; W/O/W emulsions have been investigated mostly as potential vehicles for various hydrophilic drugs (vaccines, vitamins, enzymes, hormones) that would be then slowly released. Active substances may also migrate from the outer to the inner phase of multiple emulsions, providing in that case a kind of reservoir particularly suitable for detoxification (overdose treatment) or, in a different domain, for the removal of toxic materials from waste water. In any case, the impact of double emulsions designed as drug delivery systems would be of significant importance in the controlled release field, provided that the stability and release mechanisms were more clearly understood and monitored.