Evaporative destabilization of double emulsions for effective triggering of release

In this work, volatile water-in-oil-in-water (W1/O/W2) double emulsions with a cream-like texture were formulated 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. 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 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, studies showing visual evidence of release and phase separation induced by evaporation 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.