Fluorescence induction of protoporphyrin IX by a new 5-aminolevulinic acid nanoemulsion used for photodynamic therapy in a full-thickness ex vivo skin model

An ex vivo porcine skin model was utilized to analyse the penetration of 5-aminolevulinic acid (5-ALA) contained in a nanoemulsion-based formulation BF-200 ALA (10% 5-ALA-hydrochloride) versus 16% aminolevulinate methyl ester-hydrochloride in a commercially cream (MAL cream) by fluorescence microscopy of their common metabolite protoporphyrin IX (PpIX) after 3, 5, 8 and 12 h. Fluorescence signals of PpIX in pig skin treated with BF-200 ALA were stronger than those for MAL cream. At 8 and 12 h, the PpIX fluorescence signals were 4.8- and 5.0-fold higher than those measured after MAL cream application. Fluorescence signals of PpIX after application of BF-200 ALA were detected in deeper tissue layers of the epidermis than after application of MAL cream (97.2 +/- 5.7 mu m for BF-200 ALA vs 42.0 +/- 4.2 mu m for MAL cream). These data implicate that BF-200 ALA in photodynamic therapy might lead to a superior therapeutically effect of intraepidermal (in situ) squamous cell carcinomas.