Datura metel-synthesized silver nanoparticles magnify predation of dragonfly nymphs against the malaria vector Anopheles stephensi

Abstract

Malaria is a life-threatening disease caused by parasites transmitted to people and animals through the bites of infected mosquitoes. The employ of synthetic insecticides to control Anopheles populations leads to high operational costs, non-target effects, and induced resistance. Recently, plant-borne compounds have been proposed for efficient and rapid extracellular synthesis of mosquitocidal nanoparticles. However, their impact against predators of mosquito larvae has been poorly studied. In this study, we synthesized silver nanoparticles (AgNPs) using the Datura metel leaf extract as reducing and stabilizing agent. The biosynthesis of AgNPs was confirmed analyzing the excitation of surface plasmon resonance using ultraviolet-visible (UV-vis) spectroscopy. Scanning electron microscopy (SEM) showed the clustered and irregular shapes of AgNPs, with a mean size of 40-60 nm. 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 be acting as AgNP capping agents. In laboratory, LC50 of D. metel extract against Anopheles stephensi ranged from 34.693 ppm (I instar larvae) to 81.500 ppm (pupae). LC50 of AgNP ranged from 2.969 ppm (I instar larvae) to 6.755 ppm (pupae). Under standard laboratory conditions, the predation efficiency of Anax immaculifrons nymphs after 24 h was 75.5 % (II instar larvae) and 53.5 % (III instar larvae). In AgNP-contaminated environment, predation rates were boosted to 95.5 and 78 %, respectively. Our results documented that D. metel-synthesized AgNP might be employed at rather low doses to reduce larval populations of malaria vectors, without detrimental effects on behavioral traits of young instars of the dragonfly Anax immaculifrons.

Fabrication of nano-mosquitocides using chitosan from crab shells: Impact on non-target organisms in the aquatic environment

“…Also in this second experiment, fishes were effective predators of first and second instars of malaria mosquitoes, while they are not active control agents against late larval instars. In agreement with recent research, our results highlighted that a combined approach using biofabricated AgNP and predaceous aquatic organisms represent a synergic and effective control route against mosquito vectors of economic importance (Murugan et al, 2015a(Murugan et al, , 2015b(Murugan et al, , 2015dBenelli, 2016b). Indeed, it has been showed that the predation rates of Poecilia reticulata post-treatment with Toddalia asiatica-synthesized AgNP were higher, reaching 89.75% against II instar Culex quinquefasciatus larvae, and 74% against III instar larvae (Murugan et al, 2015e).…”

“…Similarly, Roni et al, (2013) reported that AgNP produced using the aqueous leaf extract of Nerium oleander exhibited dose-dependent larval toxicity against A. stephensi. It has been argued that the biotoxicity against mosquito young instars may be related to the ability of AgNP to penetrate through the exoskeleton (Murugan et al 2015d. In the intracellular space, nanoparticles can bind to sulphur from proteins or to phosphorus from DNA, leading to the rapid denaturation of organelles and enzymes.…”

One-pot green synthesis of silver nanocrystals using Hymenodictyon orixense: a cheap and effective tool against malaria, chikungunya and Japanese encephalitis mosquito vectors?

“…Interestingly, no signicant damages were found at doses below 12 ppm. 9,41 43 Haldar et al 44 did not detected toxicity of Ag NP produced using dried green fruits of D. roxburghii against P. reticulata, aer 48 h-exposure to LC 50 of IV instar larvae of A. stephensi and C. quinquefasciatus.…”

Biological Control of Mosquito Vectors: Past, Present, and Future

“…This has been demonstrated for various species of copepods (e.g., M. edax [58], M. thermocyclopoides [54], Megacyclops formosanus [72], M. aspericornis [56]), tadpoles (e.g., Hoplobatrachus tigerinus [70]), fish (e.g., Gambusia affinis [29], Poecilia reticulata [73], Carassius auratus [74], Aplocheilus lineolatus [21]), odonate young instars (e.g., Anax immaculifrons nymphs [75], Brachydiplax sobrina nymphs [76]), and water bugs (e.g., Diplonychus indicus [77]). This opportunity should be explored further, since the exploitation of synergies between ultra-low doses of plant-fabricated mosquitocides and biological control agents may represent a further control option readily available in tropical and sub-tropical developing countries worldwide [13].…”