Plant volatiles-based supramolecular nanoassembly induced by guanidines for sustainable phytopathogen management

Plant volatiles (PVs) are recognized as important mediators of plant interactions with the function of protecting against stress and inducing defense, which presents a potential resource to biopesticides for offering a sustainable and biosafe alternative to conventional agrochemicals. However, PVs exhibit limited bioavailability in practical applications due to the off-target losses caused by high volatility and low thermolability. Here, preselected hydrophobic eugenol (EUG) as a representative molecule and two hydrophilic guanidines (arginine and polyhexamethylene biguanide) as building blocks, two water-based, high-efficiency, and eco-friendly nanosystems (EUG NPs: EA NPs and EP NPs) were developed through self-assembly technology for long-lasting and synergistic phytopathogen management without any hazardous adjuvants. The fabricated EA NPs and EP NPs exhibited high loading rates (48.53% and 42.79%) with small particle sizes of 161 and 157 nm, low polydispersity index values of 0.106 and 0.089, and high ζ-potential values of +38.40 and +58.55 mV. Meanwhile, the resulting EUG NPs displayed improved physicochemical properties, including well-defined nanostructures, low volatilization, and good storage stability, wettability, and adhesion. Importantly, the constructed nanoassemblies could respond to pH changes for long-lasting controlled release of EUG and exhibited high in vitro, in vivo, or postharvest antimicrobial efficacies against Pseudomonas syringae and Botrytis cinerea. Biosafety tests validated that EUG NPs possessed a benign biocompatibility and enabled the promotion of crop seedling growth after the spraying application. These findings illustrate a distinctive perspective for developing PVs as eco-friendly nanopesticides, highlighting a water-based approach for hydrophobic volatile-based biopesticides with improved physicochemical properties and bioavailability.