Development of topical nanoemulsions containing the isoflavone genistein

We have recently described the incorporation of genistein into topical nanoemulsions. This study describes the physicochemical properties and the genistein permeation profile from these nanoemulsions. Formulations composed of egg lecithin, medium chain triglycerides (MCT) or octyldodecanol (ODD) and water were prepared by spontaneous emulsification. Irrespective of the oil core employed (MCT or ODD), this procedure yielded monodisperse emulsions with mean droplet sizes in the range of 230-280 nm. The addition of genistein in the oil phase, before emulsification, did not alter the properties of nanoemulsions. The amount of genistein incorporated in both formulations was close to 100% (1 mg/mL). Solubility and DSC experiments suggested that egg-lecithin may play an important role on the incorporation of genistein in nanoemulsions. Genistein permeation from formulations was assessed using pig ear skin in Franz type diffusion cells. The overall results showed a slow permeation profile for genistein from both nanoemulsions. Such results open interesting perspectives for the topical administration of genistein.