Evaluation of photodynamic therapy with methylene blue, by the Fourier Transform Infrared Spectroscopy (FT-IR) in Leishmania major - in vitro.

Cutaneous Leishmaniasis (CL), a parasitic disease caused by protozoa from the genus Leishmania, affects the skin and mucous membranes. Current treatment modalities have severe side effects, underlining the need for alternative treatments. One of the emerging techniques is Photodynamic Therapy (PDT), wherein a photosensitizer delivered inside pathogen is activated by irradiation, resulting in generation of reactive oxygen species, killing the pathogen. A detailed study of chemical changes within the pathogen due to this therapy may help improve therapeutic efficiency. Therefore, in this study, Fourier Transform Infrared Spectroscopy (FT-IR) was used to investigate the chemical profiles of Leishmania major promastigotes in culture after PDT and compared with untreated pathogens. Results suggest increase in proteins, nuclear material, and disordered and β-sheet protein structures; and decrease in lipids, carbohydrates, and α-helix and turns, bends protein conformations. The Amide I band analysis showed the conformational changes in protein secondary structure. These chemical changes may be associated with known effects of PDT - membrane degradation, and reduction in the energy source of the parasite.