Amphiphilic prodrug nano-micelles of fipronil coupled with natural carboxylic acids for improving physicochemical properties and reducing the toxicities to aquatic organisms

Fipronil (FP), as a broad-spectrum and highly efficient pesticide, is strictly limited due to its high toxicity to aquatic organisms and honeybees. Herein, novel prodrugs were prepared by covalently bonding FP to three natural carboxylic acids with different polarities respectively and subsequently self-assembled into regular nano-micelles for reducing the toxicity of FP to aquatic organisms. The results showed that the obtained prodrugs possessing cleavable amide bonds could be self-assembled into nano-micelles without using any adjuvants, and the physicochemical properties of prepared nano-micelles were influenced by introduced groups and showed spherical morphology, low PDI, strong negative charges, good surface activity, and excellent max retention on hydrophobic leaves due to the amphiphilic structure. The nano-micelles formed by coupling FP with cinnamic acid had the same insecticidal activity against Plutella xylostella larvae as FP and showed four times toxicity toward adult zebrafish less than FP after 96 h treatment. Therefore, this prodrug self-assembly technology would provide a promising strategy for reducing the toxicities of pesticides to ecology and environment.