Oil-frozen W1/O/W2 double emulsions for dermal biomacromolecular delivery containing ethanol as chemical penetration enhancer

ABSTRACT Oil-frozen water-in-oil-in-water (W 1 /O/W 2 ) double emulsions (DE) containing ethanol up to 40% (w/v) in the external aqueous W 2 phase exhibited external coalescence upon thawing of the oil phase, releasing up to 85% of the encapsulated protein of the internal aqueous phase. These emulsions were studied in vitro as potential dermal macromolecular delivery formulations, achieving fluorescein isothiocyanate-labeled bovine serum albumin (FITC-BSA) penetration of up to 86 μm into porcine skin, reaching the viable epidermis where the immunocompetent Langerhans cells are located. Enzyme-linked immunosorbent assay was performed to observe the effect of the emulsification process and ethanol content on the ability of BSA to form antigen–antibody complexes; results indicated that ethanol content and the emulsification process did not diminish the BSA–antibody complex formation when compared with a BSA standard aqueous solution. Therefore, it is shown that oil-frozen W 1 /O/W 2 DE, with penetration-enhancing ethanol in the W 2 phase, can potentially be used for cutaneous vaccine delivery formulations.