In vitro antiplasmodial activity, hemocompatibility and temporal stability of Azadirachta indica silver nanoparticles

Recently green nanotechnology has gained great interest as a promising tool for drug discovery. In the present study, we synthesized and characterized silver nanoparticles (AgNPs) using Azadirachta indica (AI) and evaluated their hemocompatibility and effect against Plasmodium falciparum strains. AI leaves and barks were used for aqueous extracts (AIL and AIB) and AgNPs synthesis. AgNPs were characterized using spectroscopic, diffraction, electron microscopic and electrostatic techniques. Anti-plasmodial and haemolytic activity were assessed following the SYBR Green I fluorescence assay and Miki et al. protocol, respectively. The normalized fluorescence counts were plotted against the log-transformed drug concentration and half-maximal inhibitory concentration (IC₅₀) determined by analyzing the dose-response curves. AgNPs were stored for 120 days at room temperature-RT, +4 °C and -20 °C and subsequently their stability was evaluated by spectroscopy. Both NPs were predominantly spheroidal, crystalline in nature, stable, well dispersed with mean size of 13.01 nm for AIL-NPs and 19.30 nm for AIB-NPs and exhibited good antiplasmodial activity against 3D7 and RKL9 P. falciparum strains with IC₅₀ of 9.27 µg/mL and 11.14 µg/mL for AIL-NPs, 8.10 µg/mL and 7.87 µg/mL for AIB-NPs, respectively. A. indica contain bioactive phyto-compounds indicating great potential for anti-malarial drug development through green nanotechnology. The AgNPs were structurally stable after 120 days but antiplasmodial activity was considerably affected. A significant haemolytic activity (>25%) was observed with AIL- and AIB-AgNPs at concentrations ≥125 µg/mL.