Double-emulsion formulations have a compartmentalized structure that can provide high capacity of entrapment, protection of fragile substances, combination of incompatible substances in one product, and controlled release.  We successfully prepared volatile water-in-oil-in-water (W1/O/W2) double emulsions with a cream-like texture for potential application in dermal delivery.  This was achieved by selecting skin-compatible and volatile cyclomethicones, as the oil phase (O) of W1/O/W2 double emulsions.  Several surfactants (Abil� EM90, Abil� Care 85, and Tween 80) were used to stabilize the double emulsion structure and TEGO� Carbomer 341 ER thickener was added to reach a viscosity ratio that allowed  optimal formation of double-emulsion globules.The double-emulsion's evaporation behavior was studied by use of thermogravimetric analysis (TGA) in order to understand the release mechanism of the internal aqueous phase (W1).   The evaporation rates for the different double emulsions were compared against a mathematical model system, in which all three phases were expected to evaporate simultaneously, independently, and at constant rate.  Some similar characteristics between the model and the experimental data such as total evaporation time and presence of different evaporation stages were found.  Finally, protein release studies at skin-like thermal conditions were carried out.  It was found that the evaporation of W1/O/W2 double emulsions may act as an effective trigger mechanism for the release of ingredients in the W1 phase.  The release rate of the contents can be tuned by composition design, that is, by selecting oils with the appropriate volatility; the higher the volatility of the oil the faster the release rate of the internal aqueous phase.The understanding of the evaporation mechanism exhibited in volatile double-emulsion formulations is important for the controlled release of active substances involving applications of interest for cosmetic or pharmaceutical industries.

Evaporative destabilization of double emulsions for effective triggering of release

245th National Meeting (2013)

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