Clerodendrum chinense-mediated biofabrication of silver nanoparticles: Mosquitocidal potential and acute toxicity against non-target aquatic organisms

Mosquito-borne diseases represent a deadly threat for millions of people worldwide. However, the use of synthetic insecticides to control Culicidae may lead to high operational costs and adverse non-target effects. Plant-borne compounds have been proposed for rapid extracellular synthesis of mosquitocidal nanoparticles. Their impact against biological control agents of mosquito larval populations has been poorly studied. In this study, we synthesized silver nanoparticles (Ag NPs) using the Clerodendrum chinense leaf extract as reducing and stabilizing agent. The biosynthesis of AgNP was confirmed analyzing the excitation of surface Plasmon resonance using ultraviolet-visible (UV-vis) spectrophotometry. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) showed the clustered and irregular shapes of Ag NP. The presence of silver was determined by energy dispersive X-ray (EDX) spectroscopy. Fourier transform infrared (FTIR) spectroscopy analysis investigated the identity of secondary metabolites, which may act as Ag NP capping agents. The acute toxicity of C. chinense leaf extract and biosynthesized Ag NP was evaluated against larvae of Anopheles subpictus, Aedes albopictus and Culex tritaeniorhynchus. Compared to the leaf aqueous extract, biosynthesized Ag NP showed higher toxicity against A. subpictus, A. albopictus, and C. tritaeniorhynchus with LC50 values of 10.23, 11.10 and 12.38μg/mL, respectively. Biosynthesized Ag NPs were found safer to non-target organisms Diplonychus indicus, Anisops bouvieri and Gambusia affinis, with respective LC50 values ranging from 647.05 to 6877.28μg/ml. Overall, our results highlight that C. chinense-fabricated Ag NP are a promising and eco-friendly tool against larval populations of mosquito vectors of medical and veterinary importance, with negligible toxicity against non-target aquatic organisms.