Interface-optimized hollow metal–phenolic PDA@ZIF-8 nanocarriers for stimuli-responsive Zn2+/Salicylate co-delivery and efficient control of tobacco bacterial wilt

Sustainable management of plant bacterial diseases calls for delivery systems that minimize reliance on conventional synthetic pesticides while improving deposition efficiency, on-demand release, and environmental compatibility. This study employs a coordination-driven hollowing strategy to construct interface-optimized hollow metal–phenolic nanocarrier (NaSA@PDA@ZIF-8), achieving synergistic loading of sodium salicylate and Zn2+. PDA-induced etching of ZIF-8 generates a well-defined hollow architecture while enhancing hydrophilicity and colloidal stability. The optimized nanocarrier, obtained via Box–Behnken response surface design, achieves a NaSA loading content of 23.90%. Regarding interfacial performance, the carrier exhibits significantly optimized wetting behavior with a contact angle reduced to 51.15°, enhanced dynamic spreading speed, and outstanding leaf adhesion and rain-wash resistance, ensuring effective retention and utilization in complex field environments. Under simulated bacterial wilt conditions in tobacco (acidic pH 5.0 and elevated temperature of 35 °C), the system exhibited enhanced release behavior. The cumulative release of NaSA reached 81.72% and 83.40%, while Zn2+ release reached 23.19% and 18.72%, indicating good responsiveness to disease-relevant microenvironmental conditions. Its antibacterial activity (EC50 = 17.80 mg·L-1) is likely associated with multiple contributing factors, including Zn2+ release, potential ROS generation mediated by PDA, and NaSA-related activation of plant defense responses. This work demonstrates a hollow metal–phenolic nanoplatform that integrates interfacial adhesion, stimuli-responsive co-delivery, and biosafety, providing a multifunctional reference model for green plant protection.