Hydrophilic Model Drug Delivery from Concentrated Reverse Emulsions

Abstract

Highly concentrated water-in-oil gel-emulsions have been prepared from five components: fluorocarbon, hydrocarbon, fluorinated and hydrogenated surfactants, and water. Whatever the ratio of fluorinated to hydrogenated compounds, the stability of these mixed emulsions allows them to be used for the transport of drugs. A series of model molecules solubilized in water have been chosen because of the modulation of the hydrophobicity of the probe molecule by varying the alkyl substitute length: methyl, ethyl, and propyl paraben. The release of these molecules has been studied with an automatic setup. The experiments take about 48 h to reach equilibrium regardless of the emulsion composition. Nevertheless some variations have been observed with respect to either the chosen probe molecule or the amount of hydrogenated and fluorinated compounds in the gel emulsion. In light of the results, diffusion takes place in two possible steps: (i) transfer from big droplets to the continuous micellar phase and (ii) transfer from the continuous oily phase to the aqueous receptor solution. The influence of these two steps is related to the molecular structure of the model drug on one hand and to its solubility both in the micellar oily phase and in the aqueous phase constituting the gel emulsion in the other hand.