Background The interest in larvicides of plant origin is generally renewed in vector control because of their safety compared to synthetic larvicides. However, there are concerns about the relative safety dose of these phytochemicals on non-target organisms which led to the development of plant derived nanoparticles. In this study, we examined the bioefficacy of low doses of two green synthesized nanoparticles on immature stages of Anopheles mosquitoes in Nigeria. Aqueous plants ( Moringa oleifera and Ficus exasperata ) extracts were used in the biosynthesis. The prepared Ag-NPs were characterizations using Fourier-transform infrared spectroscopy (FT-IR), UV-Vis spectroscopy, and scanning electron microscopy (SEM). Third and early fourth instars of known susceptible laboratory strains of Anopheles gambiae s.s. (KISUMU strains) and pyrethroid resistant field strain of An. gambiae were exposed to serial dilutions of 0.25, 0.5, 0.75, 1.0 and 2.5 ppm of each phyto nanoparticles. Moribund and dead larvae were observed after 24 and 48 h post exposure, and the results were analysed with descriptive statistics. Results With the laboratory mosquitoes, Moringa oleifera AgNP effected high mortalities of 88–100% (LC 50 = 0.39 ppm; LC 95 = 0.62 ppm) at 24 h post exposure except at the lowest concentration, while Ficus exasperate AgNP induced a 32–100% mortality (LC 50 = 0.51 ppm; LC 95 = 1.15 ppm) except at the lowest concentration. In the field populations, mortality in Moringa oleifera and Ficus exasperata was 23–93% (LC 50 = 0.65 ppm; LC 95 = 2.28 ppm) and 37–50% (LC 50 = 1.51 ppm; LC 95 = 391.64 ppm) respectively. There was no significant difference in mortality values between the laboratory and field strains ( P < 0.05) at both 24 and 48 h post exposure times. Conclusions Overall, the study demonstrates the bioefficacy and potential use of green synthesized nanoparticles, at very low concentrations for the control of Anopheles larvae even in areas where resistance to the current chemical insecticides have been reported.

中文翻译：

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两种银纳米颗粒（辣木和无花果）对尼日利亚拉各斯冈比亚按蚊（双翅目：虱科）实验室和野外菌株的杀幼虫潜力

背景 由于植物来源的杀幼虫剂与合成杀幼虫剂相比更安全，因此在病媒控制中通常重新引起人们对它们的兴趣。然而，人们担心这些植物化学物质对非目标生物的相对安全剂量导致了植物衍生纳米粒子的发展。在这项研究中，我们检查了低剂量的两种绿色合成纳米粒子对尼日利亚按蚊未成熟阶段的生物功效。在生物合成中使用水性植物（辣木和无花果）提取物。使用傅里叶变换红外光谱 (FT-IR)、紫外-可见光谱和扫描电子显微镜 (SEM) 对制备的 Ag-NP 进行表征。冈比亚按蚊已知易感实验室菌株的三龄和四龄早期 （KISUMU 菌株）和 An. 冈比亚人暴露于 0.25、0.5、0.75、1.0 和 2.5 ppm 的每种植物纳米颗粒的系列稀释液中。暴露后 24 和 48 小时观察垂死和死亡的幼虫，并用描述性统计分析结果。结果 对于实验室蚊子，除了最低浓度外，辣木 AgNP 在暴露后 24 小时导致 88-100%（LC 50 = 0.39 ppm；LC 95 = 0.62 ppm）的高死亡率，而榕树刺激 AgNP 导致 32-100 % 死亡率（LC 50 = 0.51 ppm；LC 95 = 1.15 ppm），最低浓度除外。在野外种群中，辣木和无花果的死亡率分别为 23-93%（LC 50 = 0.65 ppm；LC 95 = 2.28 ppm）和 37-50%（LC 50 = 1.51 ppm；LC 95 = 391.64 ppm）。在暴露后 24 小时和 48 小时，实验室和野外菌株之间的死亡率值没有显着差异（ P < 0.05）。结论 总体而言，该研究证明了绿色合成纳米颗粒的生物功效和潜在用途，即使在已报告对当前化学杀虫剂具有抗性的地区，其浓度也非常低，可用于控制按蚊幼虫。