Development and Characterization of Pyriproxyfen-Loaded Nanoemulsion for Housefly Control: Improving Activity, Reducing Toxicity, and Protecting Ecological Environment

Nanoemulsion provides an effective way for the efficient, safe, and environmentally friendly use for pesticides. In this study, the influence of the type, dosage of emulsifier, and emulsifying process on the formation and stability of nanoemulsion were investigated. On this basis, the optimal nanoemulsion formula loaded with pyriproxyfen was obtained. Pyriproxyfen (5%) and polyoxyethylene castor oil ether (6%; EL-20) were dissolved in hydrocarbon solvent (5%; S-100) with deionized water replenished to 100%. Compared with oil-in-water emulsion (EW) and emulsifiable concentrate (EC), the longest drying time ensured that the nanoemulsions had a more durable control effect. The pyriproxyfen-loaded nanoemulsions had a high pupation inhibition rate and 100% eclosion inhibition rate. In addition, at 7 and 14 days, the 50% lethal concentrations (LC50) of pyriproxyfen-loaded nanoemulsions to Eisenia fetida were 1450.63 and 804.19 mg/kg, respectively, indicating their low acute toxicity to earthworms and environmental friendliness. Moreover, the pyriproxyfen-loaded nanoemulsions showed a low apoptosis rate (5.29%), whose value was considerably lower than that of EW (29.51%) and EC (9.45%), indicating a low toxicity to human hepatocyte L02 cells. This research facilitated the design and fabrication of nanoemulsions for water-insoluble pesticides to enhance the insecticidal activity, lower the cytotoxicity, and reduce environmental pollution of such chemicals.