Molluscicidal effect of green synthesized silver nanoparticles using Azadirachta indica on Biomphalaria alexandrina snails and Schistosoma mansoni cercariae

Abstract

Objective: To assess the molluscicidal effect of the eco-friendly green synthesized neem silver nanoparticles (neem-Ag NPs) against Biomphalaria alexandrina, the snail intermediate host for Schistosoma mansoni, and their cercaricidal potential. Methods: Methanol extracts from neem fruits were used for green synthesis of neem-Ag NPs. The neem-Ag NPs were characterized using UV-visible absorption spectra, dynamic laser light scattering technique, and transmission electron microscopy. The potential molluscicidal effect against adult and juvenile Biomphalaria alexandrina and the effect of the sub-lethal concentration on hatching of snail eggs and Schistosoma mansoni cercariae were evaluated. Results: The surface plasmon resonance of neem-Ag NPs showed a sharp absorption peak at λ max = 518 nm together with multiple peaks. The hydrodynamic diameter was (77.15±34.53) nm, the polydispersity index (0.338±0.000) and the zeta-potential -14.07 mV. Moreover, transmission electron microscopy showed that the average size of the nanoparticles was (27±2) nm. Agglomeration was evident and a light-colored capping layer could be seen coating the nanoparticles. Juvenile snails (LC 50: 0.83 ppm) were more susceptible to neem-Ag NPs than adults (LC 50: 1.07 ppm). In addition, neem-Ag NPs and neem at LC 50 concentrations inhibited the egg-hatching of snails and showed cercaricidal activity in a time-dependent manner. Conclusions: Neem-Ag NPs have lethal activities against Biomphalaria alexandrina snails and their eggs, as well as Schistosoma mansoni cercariae. Hence, neem-Ag NPs could be a potential agent to control schistosomiasis.