Preparation, characterisation and comparative toxicity of nanopermethrin against Anopheles stephensi and Culex pipiens

Objectives To assess the effectiveness of nanopermethrin as a potential new formulation for pest and vector control. Methods Permethrin nanoparticles were prepared by the ionic gelation method and its structure and the formulations were designed using Box–Behnken statistical technique. The effect of independent variables (Chitosan/Permethrin ratio, tripolyphosphate quantity, sonication time) on the properties of nanoparticles was investigated to determine the optimal formulation. Results The size of the nanoparticles ranged from 135.27 ± 5.88 to 539.5 ± 24.01 nm and the insecticide entrapment efficiency per cent (EE%) ranged from 7.72 ± 1.36 to 63.59 ± 3.17%. Anopheles stephensi larvae were then bioassayed with the nanopermethrin and compared with the results of the bioassay with the mother molecule of permethrin using a standard WHO‐recommended mosquito larval bioassay kit. LC50 with permethrin and nanopermethrin on larvae of An. stephensi were 0.125 and 0.026 ppm showing a 4.8 times difference. The LC50 for permethrin and nanopermethrin on Culex pipiens were 0.003 and 0.00032 ppm, respectively, showing a 9.4‐fold difference. Conclusion Nanopermethrin is much more potent than its mother molecule against larvae of An. stephensi and Cx. pipiens.