Characterization of starch Pickering emulsions for potential applications in topical formulations.

The aim of this work has been to characterize starch based Pickering emulsions as a first step to evaluate their possible use as vehicles for topical drug delivery. A minor phase study of emulsions with high oil content has been performed. Emulsion stability against coalescence over eight weeks and after mild centrifugation treatment has been studied. The particle size, rheological properties and in vitro skin penetration of emulsions containing three different oils (Miglyol, paraffin and sheanut oil) was investigated. It was shown that it is possible to produce oil in water starched stabilised Pickering emulsions with oil content as high as 56%. Furthermore, this emulsions show good stability during storage over eight weeks and towards mild centrifugation. The particle size of the systems are only dependent on the ratio between oil and starch and for liquid oils the type of oil do not affect the particle size. The type of oil also affects the cosmetic and rheological properties of the creams but did not affect the transdermal diffusion in in vitro tests. However, it seems as if the Pickering emulsions affected the transport over the skin, as the flux was twice that of what has been previously reported for solutions.