Toxicity of Sonneratia caseolaris-Derived Silver Nanomaterials and Related Histological Changes in the Dengue Vector, Aedes albopictus

Worldwide, dengue, Zika, and Chikungunya have the greatest potential for epidemics since they are primarily spread by the bites of infected Aedes mosquitoes. There is an urgent need for eco-friendly control tools on dengue vectors. The present research suggested a novel method of mangrove-mediated synthesis of silver nanoparticles (AgNPs) employing a leaf extract of Sonneratia caseolaris, acting as a capping and reducing agent. Further, the S. caseolaris-synthesized AgNPs were confirmed by UV-vis spectroscopy with maximum absorption of 434 nm. The crystalline nature of the S. caseolaris-synthesized AgNPs was examined through XRD. The spherical shape of the mangrove-derived AgNPs with an average size of 79.30 nm was confirmed by SEM, and the functional biomolecules which are acting as stabilizing and capping agent during the formulation of nanomaterials were examined by FTIR. Furthermore, the stability of the mangrove-derived AgNPs was analyzed through Zeta potential and DLS analysis. In mosquitocidal assay, both mangrove extract and its derived AgNPs were highly toxic against Ae. albopictus with LC₅₀ values of AgNPs were ranged from 25.20 ppm (I instar) to 101.90 ppm (pupae), and for mangrove extract, the LC₅₀ values were ranged from 240.34 ppm (I instar) to 404.76 ppm (pupae), respectively. Also, both mangrove extract and its derived AgNPs greatly reduced the adult longevity and fecundity of Ae. albopictus. Concerning non-target assay, the predatory potential of mosquito fish Gambusia affinis was 66.46% and 53.99% on III and IV larval instars of Ae. albopictus in standard laboratory conditions, while in AgNPs-treated settings, the predatory potential of fishes was boosted to 69.98% and 56.05% respectively. Finally, histological changes in Ae. albopictus targeted with mangrove-derived AgNPs were studied by light microscopy after 24 h of post treatment. Overall, this is the first report on the mosquito larvicidal and pupicidal efficacy of S. caseolaris-derived AgNPs on Ae. albopictus. These findings imply that the S. caseolaris-mediated AgNPs are an effective and environmentally friendly tool to control mosquitoes at their early life stages.