Effects of Photodynamic Therapy with Methylene Blue and Light-Emitting Diode on L. Amazonensis and L. Braziliensis Promastigotes

Background: Leishmaniasis can be present under different clinical manifestations and caused by different species of Leishmania . Photodynamic therapy (PDT) has demonstrated promising effects on leishmaniasis treatment, but it is necessary to investigate the mechanisms of action of this therapy on different Leishmania species. Methods: L. amazonensis and L. braziliensis promastigotes were used to evaluate the effects of PDT with methylene blue (MB) and red light-emitting diode (LED, 660 nm, 25 and 50 mW/cm², 60 and 300 s). The cell viability was analyzed with MTT and Trypan blue live/dead count and the morphology was analyzed with transmission electron microscopy (TEM). Results: L. amazonensis and L. braziliensis promastigotes demonstrated decrease in cell viability with PDT and a decrease in cell volume, bleb formation, chromatin condensation, mitochondrial dilation and cytoplasmic vacuoles. Conclusion: PDT caused parasite inactivation, with best results in the highest concentration and power density independent of the species.