Study of the Breakup Under Shear of a New Thermally Reversible Water-in-Oil-in-Water (W/O/W) Multiple Emulsion

Purpose. Thickening of the external aqueous phase of W/O/W multiple emulsions is essential to increase the release under shear. However, it leads to globules bursting during fabrication. To reduce this problem, we have tested a novel thermally reversible hydrogel, EMP hydrogel. This way, the corresponding multiple emulsion (EMPME) would gel only at skin temperature, which may increase the active ingredient delivery when topically applied.Methods. Samples were sheared at different shear rates and temperatures (20, 30, and 35°C) with a controlled rheometer. A granulometric analysis was then performed with a laser diffraction granulometer, to assess the break up as a function of the shear rate at the three temperatures. Conductometric measurements (CDM 230 conductometer) provided the corresponding release curves.Results. As we expected, EMPME exhibited a thermally reversible behavior. Compared to a reference emulsion thickened by carbopol, this new thermo–sensitive multiple emulsion displayed higher break up and fraction released at 35°C.Conclusion. The first thermally reversible multiple emulsion has been developed in the present work. This one presents interesting advantages: (1) an easy fabrication process with a higher entrapment yield and (2) a higher fraction released at 35°C compared with the reference emulsion.