pH/pectinase dual-responsive pectin-chitosan nanoparticles for pathogen-activated delivery of α-Terthienyl against Botrytis cinerea.

The plant-derived photoactivated fungicide α-Terthienyl (α-T) exerts antimicrobial effects through light-induced reactive oxygen species generation. However, its agricultural application has been constrained by poor targeting capability and low photostability. To address these challenges, we developed a dual-responsive nanoparticle delivery system (α-T NPs) based on a pectin-chitosan polymer network that specifically recognizes the acidic and pectinase-rich microenvironment created by Botrytis cinerea hyphae secretions. Controlled release studies demonstrated that both acidic conditions (pH 5.0) and pectinase exposure substantially promoted α-T release, achieving cumulative release rates of 71.73% and 74.49% respectively over 60 h. The nanoparticle system showed no adverse effects on healthy tomato leaf growth while forming a protective barrier that effectively suppressed fungal infection. Targeted delivery significantly enhanced fungicidal efficacy, with α-T NPs exhibiting an EC₅₀ of 0.419 mg/L compared to 1.943 mg/L for α-T (technical material, TC). Confocal microscopy and quantitative analysis confirmed the enhanced targeting mechanism, revealing substantially stronger fluorescence intensity and higher α-T accumulation specifically on treated fungal hyphae. Additionally, α-T NPs significantly improved photostability, extending the half-life by approximately 1.93-fold under continuous illumination compared to α-T (TC). This work establishes an innovative “pathogen-activated” delivery platform with promising applications in sustainable crop protection.