A pH-responsive vanillin-Schiff base microcapsule for controlled release of pyraclostrobin

Environmentally responsive microcapsules hold great promise for sustainable pest management by improving efficacy, lowering dosage and enhancing environmental compatibility. Herein, a pH-responsive pyraclostrobin (Pyr)-loaded microcapsule (Pyr@PU) with an isocyanate core and vanillin-Schiff base polyurethane shell were successfully fabricated via interfacial polymerization.

The obtained microcapsules exhibited high loading capacity (80.89%) and encapsulation efficiency (96.17%), indicating excellent drug loading and encapsulation performance. In vitro release experiments confirmed that the Pyr@PU microcapsules exhibited prominent pH-responsive release behavior, with a higher cumulative Pyr release (82.81%) at pH 4.0 after 144 h. Meanwhile, the prepared Pyr@PU microcapsules possessed excellent photostability, favorable leaf wettability and superior rainfastness. Bioactivity assays revealed that the microcapsules exerted favorable antifungal effects. At 200 μg mL^-1, Pyr@PU provided protective and curative efficacy of 79.62% and 67.59% against kiwifruit pathogens, as well as 57.90% and 37.89% on rice leaves, respectively. Biosafety evaluation showed that Pyr@PU reduced the 96-h acute toxicity to zebrafish by 2.3-fold and displayed no obvious adverse effects on rice seed germination.

The fabricated pH-responsive Pyr@PU microcapsule exhibits superior UV resistance, leaf adhesion, rainfastness, antifungal efficacy, and biocompatibility. As a promising intelligent controlled-release platform for pesticides, Pyr@PU provides both control efficacy and environmental compatibility, showing great potential for application in sustainable agriculture. © 2026 Society of Chemical Industry.