Efficacy of some pyrethroid nanopesticides against cotton leaf worm Spodoptera littoralis: Toxicity, biochemical and molecular docking studies

Abstract

Although pesticides are favourable for pest controlling because more than 30-40\% of the food production is lost due to pests, the extensive use of pesticides has harmful effects on the environment and health. Nanotechnology techniques are recently used in developing agrochemical formulations. Nanoemulsions as new approaches have attracted great attention in delivering many poorly soluble in water active compounds. In this study, the most widely used pyrethroid insecticides (cypermethrin, deltamethrin, and lambda-cyhalothrin) were formulated as nanoemulsions by high-energy ultrasonication. The droplet sizes of prepared nanoemulsions have been investigated by Dynamic Light Scattering (DLS) and Transmission Electron Microscope (TEM), characterization result reveals the size of particles in the range 24.42-84.99 nm. Formulated nanoemulsions in comparison with the active ingredient (a.i) and emulsifier concentrate (EC) were evaluated against 4th instar larvae of S. littoralis. The in vivo activity levels of targeted enzymes, acetylcholinesterase (AChE), and adenosine triphosphate (ATPase) were studied in two bioassay methods (leaf dipping and topical application). Our finding showed that cypermethrin nanoemulsion has the highest activity with LC50 = 19.92 mg/l and LD50 = 2.11 ng/larva. Furthermore, the developed nano-formulation showed adequate toxicity levels on AChE and ATPase compared to the active ingredient and EC formulations. The protein-ligand docking was also studied, and the docking poses showed that the insecticides had an excellent binding affinity to the active site of the target enzymes. On this basis, these results suggest that oil in water (O/W) nanoemulsions would be beneficial and can be applied for delivery insecticide formulations.