Sufficient PpIX production for PDT even with short contact time of topically applied 5-ALA in rabbit tongues

Although effectiveness of photodynamic therapy (PDT) after application of 5-aminolevulinic acid ointment to oral mucosal lesions has been reported, a consensus regarding recontact time of ALA applied to a lesion has been unreached. Hence, we determined the contact time of ALA required for protoporphyrin IX (PpIX) production efficient for full-blown PDT reaction. ALA ointment was topically applied to healthy rabbits’ tongues for different periods and then washed out. On the surface of the tongue, 10-min contact of ALA maximized the PpIX-derived fluorescence. PpIX yield in a tissue specimen with 10-min contact of ALA reached 73% of that in a tissue specimen with 240-min contact. Histological observation showed that PpIX accumulation predominated in the basal layer, and the PDT effects were confined in the mucosal epithelium regardless of contact time. These results suggest that 5-aminolevulinic-acid-ointment-mediated PDT with short contact of ALA is potentially applicable for treating tongue epithelial lesions.