A simple preparation process for an efficient nano-formulation: small molecule self-assembly based on spinosad and sulfamic acid

The abuse of toxic organic solvents and surfactants has caused immeasurable damage to human health and the environment. Therefore, based on the concept of green chemistry, developing a new type of nano-based pesticide formulation that does not contain harmful additives is urgent for sustainable pest management. Herein, we report two natural small molecular substances, spinosad (SSD) and sulfamic acid (SA), that were self-assembled into SSD-SA nanoparticles (SSD-SA NPs) through noncovalent interactions without involving any organic solvents or carriers. The results showed that the optimized mass ratio of SA to SSD was 1 : 4 at pH 5 and 35 °C in aqueous solution for the formation of SSD-SA NPs. The core–shell structured nanospheres with particle sizes of around 7 nm had excellent physical and chemical properties, such as strong positive charges (+47.8 mV) and good surface activity. SSD-SA NPs exhibited good quick-acting performance against Plutella xylostella larvae and Frankliniella occidentalis, and the insecticidal activities of SSD-SA NPs were significantly higher than that of the commercial SSD suspension. The genotoxicity evaluation showed that the genotoxicity of SSD to Vicia faba was reduced by a combination of self-assembly technologies and thus SSD-SA NPs posed a low risk to plant cells. These small molecular self-assembled SSD-SA NPs developed by a simple and green preparation process would have great potential for application in sustainable pest management.