Iron and iron oxide nanoparticles are highly toxic to Culex quinquefasciatus with little non-target effects on larvivorous fishes

The control of filariasis vectors has been enhanced in several areas, but there are main challenges, including increasing resistance to insecticides and lack of cheap and eco-friendly products. The toxicity of iron (Fe⁰) and iron oxide (Fe₂O₃) nanoparticles has been scarcely investigated yet. We studied the larvicidal and pupicidal activity of Fe⁰ and Fe₂O₃ nanoparticles against Culex quinquefasciatus. Fe⁰ and Fe₂O₃ nanoparticles produced by green (using a Ficus natalensis aqueous extract) and chemical nanosynthesis, respectively, were analyzed by UV–Vis spectrophotometry, FT-IR spectroscopy, XRD analysis, SEM, and EDX assays. In larvicidal and pupicidal experiments on Cx. quinquefasciatus, LC₅₀ of Fe⁰ nanoparticles ranged from 20.9 (I instar larvae) to 43.7 ppm (pupae) and from 4.5 (I) to 22.1 ppm (pupae) for Fe₂O₃ nanoparticles synthesized chemically. Furthermore, the predation efficiency of the guppy fish, Poecilia reticulata, after a single treatment with sub-lethal doses of Fe⁰ and Fe₂O₃ nanoparticles was magnified. Overall, this work provides new insights about the toxicity of Fe⁰ and Fe₂O₃ nanoparticles against mosquito vectors; we suggested that green and chemical fabricated nano-iron may be considered to develop novel and effective pesticides.