Solvent-Free Mechanochemical Synthesis of Tannic Acid–Citric Acid/Uniconazole Nanocapsules with Enhanced Intracellular Delivery for Nanopesticide Applications

Developing a safe and eco-friendly nanodelivery system is essential for enhancing pesticide efficacy and minimizing environmental and health risks. However, achieving solvent-free nanopesticide formulation remains a formidable technical challenge. Herein, we report a solvent-free mechanochemical strategy for the controllable synthesis of tannic acid–citric acid (TA-CA)/uniconazole (UZ) core/shell nanocapsules (UZ@TA-CA). Benefiting from the high active ingredient loading content of 86.4% and the porous shell structure design, the UZ@TA-CA nanocapsules demonstrate superior release performance of uniconazole under acidic, neutral, and alkaline conditions. In addition, the UZ@TA-CA nanocapsules exhibit a regular spherical morphology with an average particle size of 501.6 nm, which makes them easily absorbed by the roots for deep delivery and improved pesticide utilization. The live imaging system and laser scanning confocal microscopy results disclose that the UZ@TA-CA nanocapsules can be absorbed by cotton roots and further transported. Furthermore, transmission electron microscopy reveals that the UZ@TA-CA nanocapsules penetrate through the cell walls and plasma membranes of the root epidermis to enter the vascular tissue (xylem) and further ascend to the stems and leaves to accomplish intracellular delivery of uniconazole. This work offers a different perspective for the rational design and preparation of nanocapsules for practical applications in the field of nanopesticides.