Benzophenone-3 entrapped in solid lipid microspheres: formulation and in vitro skin evaluation

Solid lipid microspheres (SLM), lipid-in-water formulations made from oil-and-wax mixtures, were studied concerning feasibility. SLMs were then loaded with a benzophenone-3, water insoluble UVAB-filter intended for dermal application. Microspheres were prepared by dispersion with homogenisers and investigated by polarizing micrography and scanning electron micrography. For the selected formulations, investigations on percutaneous penetration of B-3 capacity were performed "in vitro" using Franz cells. Microspheres, 5-50 μm in size, and a spherical shape were obtained from several mixtures. B-3 was added and the loading capacity of this drug in the SLM was obtained for a maximum of 5% when the lipophilic phase was 18%. The lipophilic mixture with non-ionic surfactants in the selected formulation of lipid microspheres has a favorable effect on size. The selected formulation is also cosmetically adapted and it is composed of physiological and biodegradable lipids. B-3 was released and penetrated into skin more quickly and in greater quantity than in SLM form, from vehicles containing free B-3. This work has shown that SLM is an excellent carrier for lipophilic sunscreens like B-3 in order to decrease the release and penetration rate of this UV absorber compared with B-3 in oily solution.