Tehran University of Medical Sciences Iranian Journal of Parasitology 1735-7020 9 1 2014 03 15 6 13 EN Mahdi Delavari Dept. of Parasitology, Faculty of Medical Sciences, Tarbiat Modares University, Tehran, Iran. Abdolhossein Dalimi Dept. of Parasitology, Faculty of Medical Sciences, Tarbiat Modares University, Tehran, Iran. Fatemeh Ghaffarifar Dept. of Parasitology, Faculty of Medical Sciences, Tarbiat Modares University, Tehran, Iran. Javid Sadraei Dept. of Parasitology, Faculty of Medical Sciences, Tarbiat Modares University, Tehran, Iran. 2015 10 14   Background: Although pentavalent antimony compounds are used as antileish-manial drugs but they are associated with limitations and several adverse complica-tions. Therefore, always effort to find a new and effective treatment is desired. In this study, the effect of ZnO nanoparticles with mean particle size of 20 nanome-ters (nm) on Leishmania major promastigotes and amastigotes was evaluated. Methods: Viability percentage of promastigotes after adding different concentra-tions of ZnO nanoparticles (30, 60, 90 and 120 μg/ml) to the parasite culture was evaluated by MTT assay. In the flow cytometry study, Annexin V-FITC Apoptosis detection Kit was used to study the induced apoptosis and necrotic effects. Result : IC50 after 24 hours of incubation was 37.8 μg/ml. ZnO nanoparticles ex-ert cytotoxic effects on promastigotes of L. major through the induction of apopto-sis. A concentration of 120 μg/ml of ZnO nanoparticles induced 93.76% apoptosis in L. major after 72 hours. Conclusion: ZnO NPs can induce apoptosis in L. major by dose and time-de-pended manner in vitro condition. https://ijpa.tums.ac.ir/index.php/ijpa/article/view/439 https://ijpa.tums.ac.ir/index.php/ijpa/article/download/439/299