Natural phenolic Acid-Functionalized polyurethane microcapsules with superior foliar retention and UV protection for improving pesticide efficacy and safety

The leaf adhesion of pesticides and their photostability are critical challenges for modern precision agriculture, directly affecting efficacy, bioavailability, and environmental safety of pesticides. Herein, we utilized the natural phenolic acid 3,4-dihydroxyphenylacetic acid (DPA), known for its exceptional antioxidative, adhesive and UV-resistant properties, to prepare pyraclostrobin-loaded polyurethane microcapsules (Pyr@DPA-PU MCs), which achieved high encapsulation efficiency (95.57 %) and loading capacity (75.33 %), excellent spreading and leaf adhesion, as well as superior photostability. The results indicated that DPA-grafted PU shell can significantly enhance the interaction between PU MCs and rice leaves by multiple hydrogen bonds between the catechol groups and the functional groups on rice leaves. Furthermore, the hydrophobic, rigid, conjugated structure of the phenolic acids endows the MCs with exceptional UV protection for Pyr technical concentrate (TC), outperforming to the commercial formulation Seltima. In vitro bioactivity test showed that Pyr@DPA-PU MCs exhibits superior inhibitory effects against Rhizoctonia solani. Meanwhile, in vivo bioactivity tests indicated that Pyr@DPA-PU MCs markedly improved the photostability of Pyr, retaining 48.46 % antifungal activity against Rhizoctonia solani after 72 h of UV exposure, compared to 43.91 % for Seltima and only 17.71 % for a Pyr solution. Notably, Pyr@DPA-PU MCs exhibited reduced toxicity to zebrafish and LO2 cells relative to Pyr TC. This study presents a novel approach to enhance the performance of PU MCs through natural phenolic acid, thereby improving pesticide efficacy via enhanced leaf adhesion and photostability, ultimately contributing to more sustainable pesticide management practices.