In Vitro Activity of Green Synthesized Silver Nanoparticles via Thymus Vulgaris Extract against Leishmania major

Background: We aimed to assess the in vitro effects of the green synthesized silver nanoparticles (Ag NPs) via Thymus vulgaris (thyme) against Leishmania major infection. Methods: We have prepared T. vulgalis silver nanoparticles (TSNPs) by adding thyme extract to the silver nitrate aqueous solution (0.2 mM), and evaluated their antileishmanial activity. The viability of L. major promastigotes was assessed in the presence of various concentrations of TSNPs by direct counting after 24 h. The MTT assay was used to identify the viability of promastigotes. The same procedures were assessed in uninfected macrophage cells. The apoptotic effects of nanoparticles on L. major promastigotes were determined by flow cytometry assay using annexin staining. To evaluate anti-amastigotes activity of TSNPs, light microscopic observation was used to determine the number of parasites within the macrophages in each well.  Results: The effect of TSNPs on promastigotes and amastigotes of L. major was effective and had a reverse relationship with its concentration. TSNPs, inhibited the growth rate of L. major amastigotes and, the IC50 value of these nanoparticles was estimated 3.02 µg/mL (28 µM) after 72h. The results of flow cytometry showed that the toxic effects of TSNPs on promastigotes after 24 hours were statistically significant (P 0.05) and showed 69.51% of apoptosis. Conclusion: TSNPs had an inhibitor effect on promastigote and amastigote forms of L. major in vitro. It might be considered as a candidate for the treatment of this infection.