IMMOBILIZATION OF PARTICULATE SYSTEMS ON THE SKIN BY THE MEAN OF EMULSIONS

For controlled delivery purposes, it can be interesting to immobilize polymeric particles onto the surface of the skin for a prolonged perio de of time, either for pharmaceutical or for cosmetic applications. Th is paper shows that this result can be achieved by incorporating parti cles in emulsions specifically designed for this purpose. In order to evaluate the extent and duration of adhesion of such systems, an artif icial substrate has been prepared and its surface energy and hydration degree have been adjusted to reproduce those of human skin. A hydrody namic method has been used to study the removal either of crude partic les or of H/L emulsion embedded particles after deposit on either arti ficial substrate or human skin. Immobilization of the particles on the skin for prolonged periods of times (up to 330 minutes) under immersi on conditions, has been proved to be feasible. It has been shown to be dependent on formulation since particle retention was increased from 40% up to 98% when embedding the particles into the emulsion tested. A dditionnaly, good correlations between detachment from the artificial substrate and those from the human skin have been obtained. These resu lts confirm the ability of the artificial substrate to mimic propertie s of the skin which are of importance for adhesion measurements.