Construction of a Dual Drug-Loading System Based on Chitosan-Alkali Lignin Pickering Emulsion and Its Synergistic Control of Rice Sheath Blight​

Abstract

Rice sheath blight is a major global disease caused by Rhizoctonia solani (R. solani). Based on dual-pesticide synergistic co-delivery technology, multi-target synergistic intervention against the pathogen can enhance pesticide efficacy while reducing required application rates. Therefore, this study employed electrostatic self-assembly to prepare chitosan-alkali lignin (AC) nanocomposite particles as stabilizers. Through systematic optimization of oil-water ratio and ultrasonic power, a novel dual-drug Pickering emulsion delivery system (AZO@ACVA) was successfully constructed for synergistic control of rice sheath blight. This system achieves efficient co-loading of the hydrophilic pesticide validamycin (VA) and the hydrophobic pesticide azoxystrobin (AZO), demonstrating multiple functional advantages: within the acidic microenvironment formed by pathogen infection, the carrier exhibits pH-responsive release properties, enabling intelligent synergistic release of both drugs. On leaf surfaces, the amphiphilic structure of the AC nanocarrier combined with the synergistic effect of Tween 80 significantly enhances the wetting and adhesion of the emulsion on both hydrophobic rice leaves and hydrophilic cucumber leaves. The deposition levels reached 2.28 times and 1.89 times that of commercial formulations, respectively, with markedly improved resistance to rain wash-off. Simultaneously, the synergistic barrier effect between the lipid phase and lignin effectively delays pesticide photodegradation. Antimicrobial experiments demonstrate significant synergistic effects between VA and AZO in this system, achieving a much higher inhibition rate against rice sheath blight pathogens than either commercial pesticide alone. Furthermore, this fully biomass-based system substantially reduces acute toxicity to zebrafish, exhibiting excellent environmental compatibility. This study provides innovative insights and a technological platform for the synergistic delivery and green control of hydrophilic and hydrophobic pesticides.

Keywords: alkaline lignin, emulsion, dual-loaded drug, Pesticide delivery