In vitro and in vivo effects of green synthesized silver nanoparticles against Giardia lamblia infection

Abstract

The current experimental study designed to examine the in vitro and in vivo effects of green synthesized silver nanoparticles (AgNPs) against G. lamblia as one of the main causes of parasitic diarrhea. The precipitation method was used to green synthesis of AgNPs by Astragalus ecbatanus aqueous extract. In vitro assay was performed on G. lamblia cysts and trophozoites after exposure with AgNPs at 10, 20, and 40 mg/mL for 10–360 min. Effects of AgNPs on trophozoite plasma membrane and their cytotoxic effects on normal and colon cancer cells were assessed by Sytox green and cell viability MTT assay. For thein vivo assay, BALB/c mice infected by Giardia, were treated with AgNPs at 10, 15, and 20 mg/kg/day for one week. On the 8th day post-infection, stool exam was performed to check the Giardia cysts presence and the reduction rate. The AgNPs were in the range between 5 and 80 nm, and the maximum distribution of particlesize was observed at 40–60 nm. AgNPs markedly (p<0.001) increased the mortality of G. lamblia trophpzoites as a dose-dependent reaction; AgNPs at 200 and 300 μg/mL destroyed G. lamblia cysts after 4 and 2 h, respectively. Trophozoites of G. lamblia were more sensitive to AgNPs than cysts, whereas, AgNPs at 100, 200, and 300 μg/mL killed all trophozoites after 4, 2, and 1 h of treatment, respectively. AgNPs dose-dependently dropped (p<0.001) the parasite load and viability of cysts of G. lamblia. Exposure of G. lamblia trophozoites with AgNPs dose-dependently increased the plasma membrane permeability of trophozoites via rising the exposed fluorescence. The CC50 value AgNPs for colon cancer and normal cell lines was 402.3 μg/mL and 819.6 μg/mL, respectively. The selectivity value greater than 2 (2.04) implies that this AgNPs is safe for normal cells compared to cancer cells. This experimental study showed that AgNPs green synthesized by A. ecbatanus displayed considerable in vitro and in vivo anti-Giardia activity and can accordingly a candidate for Giardia infection treatment. Nonetheless, farther researches on the accurate mechanisms of action as well as clarifying all toxicity aspects of the type of AgNPs must be considered.