Eco-friendly synthesis of selenium nanoparticles using Streptomyces microflavus and their efficacy against the larvae of Culex quinquefasciatus, Aedes aegypti, and Anopheles stephensi

Mosquitoes, particularly Aedes, Anopheles, and Culex species, are significant carriers of vector-borne diseases and pose a global public health problem. The use of insecticides for vector control has detrimental effects on the environment and human health. So, in the current study, Streptomyces microflavus extract was used for the synthesis of Se-NPs through a biological and eco-friendly method and to evaluate the larvicidal, pupicidal, and larval pupal duration against A. aegypti, A. stephensi, and C. quinquefasciatus. The biosynthesized Se-NPs were characterized using UV–Vis, TEM, SEM, EDX, XRD, FTIR, Zeta, and DLS analysis. The Se-NPs showed potential larvicidal activity with a mortality percentage of 74.4% (A. aegypti), 90.4% (A. stephensi), and 95.2% (C. quinquefasciatus) respectively. The study also investigated the morphological changes in mosquito larvae treated with Se-NPs and found significant alterations in size, intestinal disruption, and damage to the anal papillae and cuticular membrane. Additionally, the Se-NPs exhibited pupicidal activity (77.33%, 66.67%, and 65.30% against C. quinquefasciatus, A. stephensi, and A. aegypti respectively) and affected the larval and pupal durations of the mosquitoes. The enzymatic antioxidant analysis showed increased levels of SOD and GPx enzymes, while the detoxified enzyme analysis showed decreased levels of AChE and GST enzymes in the treated mosquito larvae. Histopathological analysis revealed damaged epithelial cell layers, rupture of the midgut, and muscle and adipose tissue damage in the treated larvae. The toxicity of the Se-NPs on non-target organisms, such as Artemia salina, was also evaluated, and the nanoparticles showed low toxicity. Overall, the study suggests that S. microflavus–synthesized Se-NPs have potential as larvicidal agents and offer a more environmentally friendly alternative to chemical insecticides. Further research is needed to explore their mechanisms of action and effects on other organisms.

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