β-Cyclodextrin/Azobenzene Microspheres Loaded with Paraquat Are Safe and Effective

Although paraquat is a widely used herbicide, it is toxic to humans if ingested or absorbed through an open wound. To improve the safety of paraquat, a new formulation of paraquat based on photoresponsive polymers was exploited. Photoresponsive beta-cyclodextrin polymer microspheres (AZO-CD) were synthesized via a host-guest interaction between beta-cyclodextrin and azobenzene. AZO-CD were characterized by Fourier transform infrared spectrometry, circular dichroism, ultraviolet (UV) spectropho-tometry, and thermogravimetric analysis, and their photoresponsiveness was also evaluated. AZO-CD were used to load paraquat, which yielded photoresponsive paraquat-loaded microspheres. For the paraquat-loaded microspheres, irradiation with UV light or sunlight induced the isomerization of azobenzene into the cis form. Then, the cis-azobenzene was liberated from the cavities of the beta-cyclodextrin. The paraquat-loaded microspheres released paraquat continuously over time. Furthermore, under UV light, the herbicidal capacity of the paraquat-loaded microspheres against barnyard grass was comparable to that of free paraquat at the same dose. Our findings show that loading paraquat into AZO-CD provides a safe and environmentally friendly herbicide formulation.

Automated summary

Researchers improved the safety of the widely used herbicide paraquat by developing a new formulation based on photoresponsive polymers. They synthesized beta-cyclodextrin polymer microspheres that released paraquat upon exposure to UV light, showing comparable herbicidal capacity to free paraquat. This study provides a new approach for developing safer and environmentally friendly herbicides.