Fabrication of tannic acid-modified urchin-like iron oxide drug delivery system for enhanced leaf retention, pH/NIR dual-responsive release and reduced environmental harm

Given the severe environmental pollution caused by low utilization efficiency of conventional pesticides, developing intelligent, eco-friendly nanopesticides is imperative. Enhancing foliar retention and stimuli-responsive release are common strategies, yet current nano-delivery systems still suffer from insufficient foliar adhesion stability and environmental responsiveness. This work fabricated a pH/NIR dual-responsive system based on tannic acid-modified urchin-like α-Fe₂O₃. The system reinforces foliar anchoring via the synergistic effect of its spiny morphology and hydrogen-bonding interactions, with 1.5-fold higher retention than spherical particles. Moreover, this system enhances imidacloprid (IMI) photostability by 70 % relative to free IMI, with encapsulation efficiency and loading capacity of 26.64 % and 10.22 %, respectively. Relative to single-responsive systems, it features a NIR-boosted pH-responsive mechanism that enables precise pesticide release, thus achieving a 95.5 % mortality rate against target pests at low concentrations. Additionally, it exhibits favorable biocompatibility verified by cellular and zebrafish assays, while iron ions released from degradation promote plant growth. Therefore, this system integrates the synergistic functions of enhanced foliar retention, improved photostability, precise drug release, and crop growth promotion. These results validate its potential in boosting pesticide utilization and alleviating environmental risks, offering new perspectives for designing high-efficiency, eco-friendly nanopesticide formulations.