Photodynamic Therapy Using Toluidine Blue O (TBO) Dye as a Photosensitizer against .

Background: Photodynamic therapy (PDT) is alternative treatment of cutaneous leishmaniasis (CL), and phenolthiazine dyes such as Toluidine Blue O (TBO) have the potential role in PDT and notably affect parasites inactivation. This study aimed to evaluate the effectiveness of PDT by using TBO and a light-emitting diode (LED) in the treatment of zoonotic CL (ZCL).

Methods: The study was conducted in Iran University of Medical Sciences, Tehran, Iran in 2018-2020. Different concentration (7.8 μg/mL up to 500 μg/mL) of TBO as a photosensitizer and a 630 nm LED light as a source of light were used for antileishmanial activity against both forms of promastigotes and intracellular amastigotes. Effective concentration (EC) and cell cytotoxicity (CC) were calculated in both infected and non-infected J774.A1 macrophages, respectively. As well as inhibitory concentration (IC) was quantified in promastigotes for 2 h, 24 h, and 48 h after incubation using a MTT colorimetric assay.

Results: TBO dye in combination with the PDT significantly decreases the promastigotes and intra-cellular amastigotes viability when compared with TBO alone. Both TBO dye in combination with the PDT and TBO alone had no toxic effects on the mice macrophages; however, it significantly killed the entered parasites inside the cells. Our results in the current study established satisfactory findings in clearing intracellular parasites in in-vitro conditions.

Conclusion: TBO dye in combination with the PDT can be considered as a harmless, effective and importantly perfect treatment against causative agent of ZCL, in an in-vitro situation without any negative toxicity to the mice macrophages.