Photodynamic therapy using methylene blue to treat cutaneous leishmaniasis

The purpose of this study was to show the efficiency and underlying mechanism of action of photodynamic therapy (PDT) using methylene blue (MB) and non-coherent light sources to treat cutaneous leishmaniasis (CL).

Systemic treatment can cause severe side effects, and PDT using porphyrin precursors as sensitizers has been used as an alternative to treat CL. MB has been used under illumination or in the dark to treat a wide range of medical conditions, and it exhibits antimicrobial activity against protozoa and viruses.

In in vitro tests, the cell viability (via a MTT colorimetric assay) of Leishmania amazonensis parasites was evaluated as a function of MB concentration. In in vivo experiments, we analyzed the treatment of two lesions from a patient with leishmaniasis. The patient received a low dose of pentavalent antimony (SbV), and one lesion was treated with PDT.

We observed IC(50) decreases from 100 to 20 μM in response to PDT when MB was used in different concentrations in in vitro tests. Use of SbV in combination with the PDT protocol produced faster wound recovery when compared with the use of SbV alone.

The in vitro experiments and the results from the clinical case suggest that the inexpensive PDT protocol that is based on MB and RL50® may be used to treat CL caused by L. amazonensis.