Inorganic Nanoparticles–Driven Self–Assembly of natural small molecules in water for constructing multifunctional nanocapsules against plant diseases

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Directly constructing nanoparticles through the self–assembly of natural small molecules in aqueous media presents many opportunities for crop protection; however, this special strategy is hindered by the lack of simple and cost–effective preparation methods to date. Herein, we report a facile strategy for constructing multifunctional natural nanocapsules for treating plant diseases based on the special coassembly of natural small organic molecules and inorganic nanoparticles. In aqueous conditions, uniform curcumin nanocapsules (ZnO@Cur) are assembled through electrostatic interactions, coordination effects and hydration effects as mediated by trace of nanoscale zinc oxide. The nanocapsules obtained can be further modified to enhance stability by introducing a polydopamine coating (ZnO@Cur@PDA). The antibacterial activity of ZnO@Cur@PDA against plant-pathogenic bacteria was better than that of curcumin, ZnO NPs, ZnO@Cur and zinc thiazole in vitro. The nanocapsules effectively kill plant–pathogenic bacteria via tight binding to the bacterial surface, inducing reactive oxygen species accumulation and disrupting bacterial cell walls. ZnO@Cur@PDA display strong activities against rice bacterial blight with protective activity of 64.0 % and curative activity of 62.2%, which is much better than commercial drugs bismerthiazol (protective activity of 33.0 % and curative activity of 38.4%) and zinc thiazole(protective activity of 38.6 % and curative activity of 31.8%). ZnO@Cur@PDA display adequate washing resistance, and low rice plant toxicity; furthermore, they are degradable. Additionally, both the inner cavities and outer surfaces of nanocapsules bear abundant sites and spaces that can be further tuned for loading other pesticide molecules or flexible construct complex multifunctional nanoparticles. Our study should encourage further development in the coassembly of organic and inorganic materials via green processes for effective and tunable nanopesticides.