Preclinical Investigation of Methylene Blue‐mediated Antimicrobial Photodynamic Therapy on Leishmania Parasites Using Real‐Time Bioluminescence

Cutaneous leishmaniasis (CL) is a neglected disease that promotes destructive lesions. Difficulties in treatment are related to accessibility of drugs, resistance and toxicity. Antimicrobial photodynamic therapy (APDT) has been emerging as a promising treatment for CL. In this work, we evaluated methylene blue (MB)‐mediated APDT (MB‐APDT) on Leishmania amazonensis in vitro and in vivo by bioluminescence technique. In vitro , MB‐APDT was performed using a red LED (λ = 660 ± 11 nm, 100 mW cm −2 ) and MB (100 µ m ) at different light doses. In vivo , mice were infected and 4 weeks later, randomly divided into three groups: control, APDT 1 (single session) and APDT 2 (two sessions of MB‐APDT). MB was used at 100 µ m and energy dose was established at 150 J cm −2 . Parasite burden, lesion size and pain were evaluated weekly for 4 weeks. In vitro , lethal dose for 90% parasite inactivation was achieved at 48.8 J cm −2 . In vivo, although APDT 1 and APDT 2 groups have showed similar parasite burden after 4 weeks, two sessions were clinically better, especially considering the inflammatory process associated to CL. Our findings reinforce MB‐APDT as a cost‐effective treatment to combat CL.