Biomass coacervate micro-bridges for eradicating hydrophobic fungal conidia

Fungal conidia, the primary vectors for crop disease persistence, possess chemically inert and hydrophobic surfaces that thwart conventional fungicides by creating a formidable barrier to interfacial wetting and active-ingredient delivery. Using gray mold (Botrytis cinerea) as a model, we address this challenge by engineering an all-biomass coacervate platform via the electrostatic self-assembly of anionic sodium lignosulfonate (SL) and cationic ε-poly-l-lysine (PLL). These bio-based droplets function as versatile micro-carriers, simultaneously partitioning hydrophilic berberine (BER) and hydrophobic eugenol (EUG) to enable synchronized, dual-phase delivery from a single aqueous continuous phase. The resulting BER-EUG@SL/PLL system exhibits enhanced wetting, spreading, and adhesion on crop leaf surfaces. In vitro assays demonstrate that the BER-EUG@SL/PLL system achieves superior antifungal efficacy, yielding an EC₅₀ of 53.11 mg/L, a 2.18-fold enhancement over the berberine aqueous solution and a 1.68-fold improvement over the physical mixture. A co-toxicity coefficient (CTC) of 126.48 confirms that the coacervate architecture facilitates a potent synergistic effect between the two actives. Crucially, we propose and validate an "interfacial enrichment-hotspot" mechanism. Micro-interfacial characterization reveals that the coacervates preferentially adhere to the conidial surface, concentrating the encapsulated actives at the spore-water interface and overcoming the inherent hydrophobicity of the fungal wall. Furthermore, this biomass-derived matrix significantly mitigates off-target toxicity in zebrafish, Vicia faba, and Chlorella vulgaris. This work provides a sustainable, high-efficiency strategy for the delivery of amphiphilic agrochemical cargoes, offering a sophisticated material solution to persistent agricultural pathogens.