Infrared Photobiomodulation Modulates <scp>PpIX</scp> Production After Topical Methyl Aminolevulinate in Normal Human Skin: An Exploratory Study

Photodynamic therapy (PDT) for skin lesions requires optimized photosensitizer accumulation. Since protoporphyrin IX (PpIX) synthesis is linked to mitochondrial activity, photobiomodulation (PBM) may modulate this process. This exploratory study examined the effects of PBM at 780 or 808 nm on MAL-induced PpIX in normal human skin. Eleven volunteers received paired-arm treatments (5, 10, or 15 J/cm²). Following 30 min of MAL, PBM was applied, with total incubation lasting 210 min. PpIX was assessed via spectroscopy and widefield imaging. Although mean PBM/no-PBM ratios were nominally above 1, no statistically significant differences were found among fluences or against unity, primarily due to high interindividual variability (CV up to 35%). These findings suggest that while PBM shows a trend toward modulating photosensitizer accumulation, the response is highly heterogeneous. This study provides a rationale for further investigation into personalized PBM-assisted PDT protocols to manage biological variability and refine clinical outcomes.