Structural analysis and adsorbability onto the corneal epithelial cells-model interface of vitamin nano-emulsions.

: O/W nano-emulsions can be used as effective drug carriers of hydrophobic active ingredients in an aqueous solution, because nano-emulsions are comparatively stable and their structure can be controlled by changing the compositions and the preparation methods. In this paper, we focused on vitamin A and its derivatives (VA), which are among the widely-used lipophilic active ingredients, and tried to develop the nano-emulsions, which can bring out the efficiency of VA for the healing of injured corneas, with the detailed structural analysis of them using the small-angle X-ray scattering (SAXS) method. As a result, we elucidated that the nano-emulsions bearing the hydrophobic oil/water interface can be prepared by decreasing the surfactant concentration against vitamins. Moreover, we clarified that the nano-emulsions composed of lower surfactant concentration tend to adsorb VA onto the corneal epithelial cells-model interface. Therefore it is necessary to prepare the nano-emulsions, which have the hydrophobic oil/water interface for improving the adsorbability onto cell membranes.