Photo-induced antileishmanial activity of indocyanine green: In vitro and in vivo studies

Abstract Background Indocyanine green is a promising dye for photodynamic and photothermal therapy. However, ICG tends to aggregate in aqueous media, which limits its use in light therapy. Loading ICG onto a biocompatible structure can improve its aqueous stability. The aim of this study was to investigate the synergistic effect of PDT/PTT on leishmanial activity in the presence of micelles loaded with ICG. Methods After synthesizing micelles containing ICG, the dark toxicity of the pharmaceutical agents and in vitro phototoxicity by a cw 808 nm laser on promastigotes were determined via MTS assay. Finally, the efficacy of the treatments was assessed by measuring the diameter of the lesion every three days in a study conducted on 33 female BALB/c mice aged 4-6 weeks. Results At 808 nm, the absorbance of ICG inside the micelles was approximately2.5 times that of free ICG. The optimal concentration of ICG was determined to be 100 μM based on the toxicity of the medicinal agents topromastigotes. In the in vitro experiment, the groups containing ICG showed a significant decrease in survival compared to the control group with increasing light dose. In the animal model study, the simultaneous presence of medicinal agents and the application of a laser created a significant difference in the relative area of the lesion compared to the control group. Conclusion The findings of this study show that PTT/PDT mediated by ICG can be considered an inexpensive, safe, easy to administer and efficient treatment against Leishmania L. major both in vitro and in vivo. Moreover, this treatment does not cause any adverse effects when compared to other treatments.