Biotoxicity of Azadirachta indica-synthesized silver nanoparticles against larvae of Culex quinquefasciatus

• Published in: South African journal of botany 2023-02, Vol.153, p.308-314
• Main Authors: Aremu, Harun K., Azeez, Luqmon A., Adekale, Idris A., Busari, Hassan K., Adebayo, Zainab A., Disu, Alimat, Usman, Halima N., Adeyemo, Oluwatosin M., Oyewole, Olu I.
• Format: Article
• Language: English
• Subjects: Azadirachta indica; Culex quinquefasciatus; Enzyme profile; Genotoxicity; Larvicidal activity; Silver nanoparticle
• ISSN: 0254-6299; 1727-9321
• DOI: 10.1016/j.sajb.2023.01.021

•The UV peaks at 425 nm and the FTIR analysis displayed five prominent bands.•Toxicity of biosynthesized AgNPs showed a concentration-dependent larvicidal effect.•There is a significant alteration of antioxidant profile in larvae.•There were visible changes in the genome during toxicity. With the increasing number of disease-related deaths from mosquitoes, it is critical to develop effective and environmentally friendly alternatives. The present study synthesized and characterized silver nanoparticles mediated with aqueous leaf extract of Azadirachta indica and established the larvicidal potential against Culex quinquefasciatus. The biosynthesized AgNPs were characterized using UV-visible spectroscopy, Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and energy dispersive X-ray fluorescence spectroscopy (EDXRF). Fourth-instar larvae of Cx. quinquefasciatus were subjected to different concentrations (50 – 250 mgL−1) of the biosynthesized AgNPs for 24 hr. Toxicity was further evaluated by monitoring changes in the enzyme profile and the integrity of DNA of larvae using random amplified polymorphic DNA assay (RAPD). The SEM image showed the biosynthesized AgNPs appeared clustered and had a characteristic peak at 425 nm. FTIR analysis revealed prominent peaks at 3455, 2934, 1636, 1385 and 1076 cm−1 representing O-H stretching of alcohols, C-H stretching vibration attributed organic molecules, N-H bending characteristic of primary amines, and alkyl groups, O-H bending and secondary alcohol. Biosynthesized AgNPs showed a dose-dependent larvicidal effect. Maximum mortality (97.40 %) at 250 mgL−1 with LC50 and LC90 values of 85.56 mgL−1 and 231.51 mgL−1 respectively along with a significant alteration in activities of CAT, GST, ALP and GSH concentration in larvae was observed. Also, the loss of primer bands suggests some level of genotoxicity. Overall, the biosynthesized AgNPs of A. indica have the potential to be used in the development of safe and eco-friendly larvicide for the control of mosquito larvae.