Stabilisation of w/o/w multiple emulsions by interfacial complexation of macromolecules and nonionic surfactants

Abstract

A new approach to obtain stable w/o/w multiple emulsions has been developed; the basis is the interfacial interaction between a macromolecule, e.g. albumin or polyacrylic acid in the internal aqueous, and a lipophilic poloxamer surfactant in the dispersed oil phase. Lipophilic poloxamer surfactants of high molecular weight, e.g. Poloxamer 331, were preferable in forming a stable w/o and the subsequent w/o/w emulsions. Similarly, hydrophilic poloxamer surfactants of high molecular weight could enhance the stability of the w/o/w multiple emulsions when used to emulsify the initial w/o emulsions, e.g. poloxamer 403. A water soluble, internal marker, Sulphane Blue, was encapsulated within the emulsion droplets and the release rate studies were carried out. The results revealed that both the mass transfer rate and stability of the oil membrane could be influenced by the combination of external (secondary) hydrophilic surfactants used. The secondary surfactant affected release rate primarily by control of mass transfer through the oil liquid membrane. In optimising a stable multiple emulsion formulation, both the HLB (hydrophilic-lipophilic balance) values and surface activities of the surfactants have to be considered.