Photodynamic Therapy Mediated by Methylene Blue Dye in Wound Healing

OBJECTIVE: We sought to investigate the wound-healing process after photodynamic therapy (PDT) mediated by methylene blue dye (MB). BACKGROUND DATA: Few scientific studies show the PDT roles in wound healing. MATERIALS AND METHODS: One hundred rats were given a circular wound on the back, inflicted with a 6-mm-diameter punch. The animals were divided into four groups: control (no treatment); dye (topical application of MB); laser (InGaAlP, 117.85 J/cm(2), 100 mW, 660 nm, single point); and PDT (topical application of MB followed by laser irradiation). After 1, 3, 5, 7, and 14 days, the cutaneous wounds were photographed and assessed with histopathologic examination by using light microscope. Changes seen in edema, necrosis, inflammation, granulation tissue, re-epithelialization, and number of young fibroblasts were semiquantitatively evaluated. The wound-area changes were measured with special software and submitted to statistical analysis. RESULTS: The laser group demonstrated the smallest wound area at 14 days after the surgical procedure (p < 0.01). Concerning complete re-epithelialization, the laser group showed it at 5-7 days after surgery, whereas the PDT and the other groups showed it at 14 days. CONCLUSIONS: Laser interaction with tissue is somehow changed when exposed to the MB. PDT mediated by MB was not prejudicial to wound healing, as no delay occurred compared with the control group.