Sodium Alginate-Encapsulated ZIF-8 Nanoparticles for Enhanced Foliar Adhesion and pH-Responsive Delivery of Tebuconazole

The development of functional nanopesticides is crucial for improving pesticide utilization efficiency and represents a major research direction in pesticide formulation. In this study, a sodium alginate-coated metal–organic framework (ZIF-8@SA) was used as a carrier to construct a tebuconazole (Teb) nano-delivery system, Teb/ZIF-8@SA, featuring foliar adhesion and pH-responsive release properties. The structure and performance of the system were systematically investigated. Results showed that Teb/ZIF-8@SA had an average particle size of approximately 394.14 nm and a pesticide loading capacity of 25.73% w/w. Its deposition on cabbage leaves was 1.29 times higher than that of a tebuconazole suspension. After simulated rainfall, the retention of active ingredient on leaves was 4.25 times greater than that of the suspension. The system exhibited distinct pH-responsive release behavior, with cumulative release rates of 61.89% at pH 7 and 89.21% at pH 5 over 84 h. Plant absorption and translocation experiments demonstrated that, seven days after foliar application, Teb content in leaves, stems, and roots of cucumber plants was 3.18, 2.59, and 1.13 times higher, respectively, compared to the suspension treatment, indicating effective uptake and translocation. In plate antifungal assays, Teb/ZIF-8@SA showed a 25.43% higher inhibition rate against Fusarium graminearum than the suspension. Moreover, acute toxicity to zebrafish was nearly tenfold lower for Teb/ZIF-8@SA than for the Teb suspension. In conclusion, this foliar-adhesive and pH-responsive nano-delivery system offers a promising strategy for sustainable agriculture development.