Glutathione and Laccase Dual-Responsive Lignin Nanocarriers Inspired by Host-Pathogen Interactions for Fungicide Delivery

Designing sustainable plant protection strategies inspired by host-pathogen interactions is an effective approach to improve pesticide utilization and reduce the environmental risks of traditional formulations. Herein, based on the phenomenon that the rice blast fungus releases laccase during crop infection by a burst of glutathione (GSH) when crops are subjected to biotic stress, lignin nanocarriers crosslinked with GSH-responsive cystamine are introduced to obtain dual-responsive pyraclostrobin-loaded nanocarriers (Pyr@MLC) with ca. 90 nm diameter. Pyr@MLC are synthesized via crosslinking methacrylated lignin with cystamine in miniemulsion. Pyr@MLC accelerates the release of the fungicide by both triggers: GSH (cleaving disulfide linkages in cystamine) and laccase (degrading lignin). Additionally, Pyr@MLC exhibits superior dispersion, foliar retention, and a 30-fold enhancement in fungicide photostability. Pyr@MLC demonstrates a 61.4 ± 4.7% control efficacy against rice blast in a pot assay, exceeding that of non-GSH-responsive nanocarriers (49.7 ± 4.9%) and pyraclostrobin suspension concentrate (22.9 ± 2.4%) after 14 days of treatment. Moreover, confocal microscopy shows that the Pyr@MLC can be bidirectionally translocated in barley plants and without impact on plant growth within one month. These findings underscore the potential of lignin nanocarriers for efficient, targeted fungicide delivery in plants, providing a promising strategy to advance sustainable agriculture.