新型pH响应性噻虫嗪纳米脂质体的制备及其杀虫活性

Fabrication of pH-responsive non-phospholipid liposomal nanocarriers for insecticidal activity of thiamethoxam

为提高农药利用率,减少环境风险,提高农药靶向性,利用胆固醇和硬脂胺通过自组装形成的非磷脂类纳米脂质体作为农药载体,构建了具有缓控释特性的噻虫嗪纳米脂质体。电镜和粒度分析结果表明,该纳米制剂呈现出良好的分散性和稳定性,载药后的纳米粒径为173.7 nm±1.6 nm,载药量为8.97%,带有正电荷的脂质体与噻虫嗪间存在静电相互作用。体外释放试验结果表明,相对于原药组8 h内完全释放,噻虫嗪纳米脂质体8 h累计释放率为62%,实现了噻虫嗪的缓释效果。制备的噻虫嗪纳米脂质体具有碱性pH敏感性,其中当pH值为10.0时噻虫嗪的释放速率显著提高,有助于噻虫嗪在鳞翅目昆虫独特的碱性pH中肠环境中进行响应性释放和积累。以亚洲玉米螟Ostrinia furnacalis为模式昆虫的杀虫活性试验结果表明,有效成分为0.6 mg/mL的噻虫嗪纳米脂质体较原药组的杀虫活性更佳,作用1 d后原药组仅部分影响其生命活动,而纳米脂质体组存活率已降至60%以下,表现出纳米脂质体载体提高了噻虫嗪对玉米螟的杀虫活性。以非磷脂类脂质体作为农药载体,为农药活性成分的定向可控递送和缓控释提供了新的理论依据与技术途径,不仅可高效提高农药利用率,同时具备经济和环境友好等优势,具有广阔的应用前景。

Non-phospholipid liposomes(sterosomes) composed of cholesterol and stearylamine were fabricated as a sustained and pH-responsive pesticide carrier for controlling the release of thiamethoxam(Thx) agianst Lepidoptera pests. This strategy achieved high insecticidal activity, reduced environmental risks and improved targeting of pesticides. Thx-loaded sterosomes were prepared by repeated freeze-thaw cycles and characterized with field emission scanning electron microscopy(FESEM). The size distribution and ζ-potential were also determined. The results demonstrated that sterosomes(173.7 nm ± 1.6 nm) exhibited good dispersibility and stability. The drug loading was8.97%. Prolonged drug release was obtained at pH 7.0, which would help to achieve drug delivery with the movement of the carriers and effectively reduce the release rate of Thx, while at pH 10.0, the release rate was accelerated, due to the phase separation between deprotonated stearylamine and cholesterol.This property may improve the accumulation of Thx in the gut of Lepidoptera, as their digestive tract has a unique highly alkaline pH. The insecticidal effect was evaluated using Ostrinia furnacalis as the model insect, and the survival rate of Thx-sterosomes group(effective Thx 6 mg/mL) was lower than60% after 1 day. Thx-loaded sterosomes showed better efficacy and a stronger insecticidal activity than the free Thx solution. Thx-loaded sterosomes exhibited sustained and pH-responsive controlled release of the pesticide, suggesting a practically and economically desirable strategy for the preparation of novel pesticide formulations.