Preparation and In Vitro Evaluation of W/O Nanoemulsions for the Skin Permeation of 5-Aminolevulinic Acid.

We investigated the skin permeation of 5-aminolevulinic acid (ALA) through Yucatan micropig full-thickness skin by using ALA-loaded W/O nanoemulsions composed of Span/Tween/ethanol (EtOH)/isopropyl palmitate (IPP)/10 wt% aqueous ALA solution. The nanoemulsions were prepared using Span 20/Tween 20 (S20/T20), Span 80/Tween 80 (S80/T80), and Span 20/Tween 80 (S20/T80) mixed surfactant systems. Based on the results of the phase diagram study and hydrodynamic diameter measurement of the nanoemulsions, we decided that the optimal weight ratio of Span/Tween/EtOH/IPP/10 wt% aqueous ALA solution in the nanoemulsion was 0.