Thesis ( Ph.D.) - Cairo University - Faculty of Science. - Department of Entomology

Effects of Plant Extract-mediated and Radio-synthesized Nanoparticles on Culex pipiens complex (Diptera: Culicidae) Ph.D. Degree in Entomology (Insect physiology and cell biology). Effective strategies for mosquitos{u2019} management are crucial to minimize the number of mosquito-borne diseases. This problem is being solved by using safer nanocids that reduce environmental pollution among integrated pest management (IPM) programs. Selenium nanoparticles (SeNPs) were green synthesized using Cupressus sempervirens, microwave (MW) and gamma (G) irradiation methods. SeNPs were characterized by UV-Vis spectroscopy, transmission electron microscopy (TEM), fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), dynamic light scattering (DLS) and zeta potential analysis. Characterization revealed stable spherical particles with a size of 11-55 nm for SeNPs-MW (20 min) and 21-75 nm for SeNPs-G (40 KGy). Ionizing and non-ionizing radiations play significant roles in increasing SeNPs yield and decreasing their size. The concentration LC50 of 3rd instar larvae Culex pipiens for SeNPs-MW, and SeNPs-G were 28.25 mg/L and 31.28 mg/L, respectively. The accumulated Se concentration was increased in SeNPs-G-treated larvae and measured with inductively-coupled plasma mass spectrometry (ICP-MS). Evaluation of the adverse effects of SeNPs on detoxification enzymes, acetylcholinoesterase (AChE), glutathione-S-transferase (GST) and carboxylesterase (CarE) in the 2nd, 3rd and 4th instar larvae at concentration LC50 were recorded. Significant decreases were observed in the total protein levels. Genotoxicity and ultrastructure of the integument and midgut epithelial cells of the 3rd instar larvae showed DNA damage and cell lysis, accumulation and penetration of SeNPs in the exoskeleton. These results highlighted the important role of G and MW irradiation with plant extract in the synthesis and stabilization of SeNPs, and their insecticidal effect on mosquito larvae. Also, the results indicate adverse effects of SeNPs on AChE gene expression which is down regulated, suggesting that SeNPs induce the formation of reactive oxygen species responsible for apoptosis.

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