Single-Step Biofabrication of Silver Nanocrystals Using Naregamia alata: A Cost Effective and Eco-Friendly Control Tool in the Fight Against Malaria, Zika Virus and St. Louis Encephalitis Mosquito Vectors

Abstract

Botanical-based nanosynthesis has been recently reported as a cheap alternative for mosquito management. Screening different botanicals as reducing and capping agents led to the production of metal nanoparticles with different biophysical and mosquitocidal features. Here, Naregamia alata-mediated biosynthesis of silver nanoparticles (AgNPs) was conducted. AgNPs were tested on egg, larval and adult populations of three important mosquito vectors, Anopheles stephensi, Aedes aegypti and Culex quinquefasciatus. AgNPs were characterized using UV–Vis spectrophotometry, FTIR, AFM, SEM, TEM, EDX, and XRD analyses. Maximum larvicidal toxicity was detected against A. stephensi (LC50 = 12.40 µg/ml), followed by A. aegypti (LC50 = 13.57 µg/ml) and C. quinquefasciatus (LC50 = 14.84 µg/ml). A single treatment with AgNPs tested at 60, 75 and 90 μg/ml led to no egg hatchability. In adulticidal experiments, the maximum efficacy was observed on A. stephensi (LD50 = 31.60 μg/ml), followed by A. aegypti (LD50 = 34.31 μg/ml) and C. quinquefasciatus (LD50 = 37.52 μg/ml), respectively. AgNPs were safer for three non-target mosquito natural enemies, Anisops bouvieri, Diplonychus indicus and Gambusia affinis, with LC50 ranging from 629 to 2111 µg/ml. Overall, N. alata-fabricated AgNPs are a promising and eco-friendly tool against Anopheles, Aedes and Culex mosquito vectors, with negligible toxicity against non-target aquatic organisms.