One-step supramolecular co-assembly of lignin into micro-/nanospheres for photostable, sustained-release delivery of photosensitive pesticides

Abstract

Conventional pesticide formulations face trade-offs among energy-intensive processing, organic-solvent burdens, and poor photostability. While encapsulation strategies offer a remedy, they are invariably hampered by intricate, multi-step fabrication. Herein, we develop a one-step, low-energy, and scalable aqueous platform to prepare micro-/nanosphere suspensions through cooperative self-assembly of renewable sodium lignosulfonate (SL) with pesticides, exemplified by emamectin benzoate (EB). EB-loaded spheres (EB@MSs and EB@NSs) form in situ at the water/cyclohexanone interface without pre-fabricated carriers or external crosslinking.Multiscale characterization indicates that electrostatic interactions and hydrogen bonding between SL and EB drive the assembly, yielding well-defined, uniform spheres. Remarkably, after 240 min of UV irradiation, EB@MSs and EB@NSs retain approximately 80% of EB, a four-fold enhancement over conventional emulsifiable concentrate (EC) and suspension concentrate (SC) formulations (~20%). This excellent photostability stems from the protective lignin-based matrix formed during the one-step assembly; moreover, the platform is applicable to various photosensitive pesticides.Laboratory and field trials against multiple pests demonstrate high efficacy with reduced dosage and extended protection. It also improves safety toward non-target organisms, including Daphnia magna and the predatory mite Amblyseius cucumeris.Overall, this research provides theoretical guidance and practical basis for the environmentally-friendly, low-energy production of green pesticide formulations.