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 emulsio ns is essential to increase the release under shear. However, it leads to g lobules bursting during fabrication. To reduce this problem, we have tested a navel thermally reversible hydrogel, EMP hydrogel. This way, the corresp onding 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 degreesC) with a controlled rheometer. A granulometric analysi s was then performed with a laser diffraction granulometer, to assess the b reak up as a function of the shear rate at the three temperatures. Conducto metric measurements (CDM 230 conductometer) provided the corresponding rele ase curves. Results, As we expected, EMPME exhibited a thermally reversible behavior. C ompared to a reference emulsion thickened by carbopol, this new thermo-sens itive multiple emulsion displayed higher break up and fraction released at 35 degreesC. Conclusion. The first thermally reversible multiple emulsion has been devel oped in the present work. This one presents interesting advantages: (1) an easy fabrication process with a higher entrapment yield and (2) a higher fr action released at 35 degreesC compared with the reference emulsion.