Abstract：
The atrazine nanodelivery system, composed of poly(ε-caprolactone) (PCL+ATZ) nanocapsules (NCs), has demonstrated efficient delivery of the active ingredient to target plants in previous studies, leading to greater herbicide effectiveness than conventional formulations. Established nanosystems can be enhanced or modified to generate new biological activity patterns. Therefore, this study aimed to evaluate the effect of chitosan coating of PCL+ATZ NCs on herbicidal activity and interaction mechanisms with Bidens pilosa plants. Chitosan-coated NCs (PCL/CS+ATZ) were synthesized and characterized for size, zeta potential, polydispersity, and encapsulation efficiency. Herbicidal efficiency was assessed in postemergence greenhouse trials, comparing the effects of PCL/CS+ATZ NCs (coated), PCL+ATZ NCs (uncoated), and conventional atrazine (ATZ) on photosystem II (PSII) activity and weed control. Using a hydroponic system, we evaluated the root absorption and shoot translocation of fluorescently labeled NCs. PCL/CS+ATZ presented a positive zeta potential (25 mV), a size of 200 nm, and an efficiency of atrazine encapsulation higher than 90%. The postemergent herbicidal activity assay showed an efficiency gain of PSII activity inhibition of up to 58% compared to ATZ and PCL+ATZ at 96 h postapplication. The evaluation of weed control 14 days after application ratified the positive effect of chitosan coating on herbicidal activity, as the application of PCL/CS+ATZ at 1000 g of a.i. ha-1 resulted in better control than ATZ at 2000 g of a.i. ha-1 and PCL+ATZ at 1000 g of a.i. ha-1. In the hydroponic experiment, chitosan-coated NCs labeled with a fluorescent probe accumulated in the root cortex, with a small quantity reaching the vascular cylinder and leaves up to 72 h after exposure. This behavior resulted in lower leaf atrazine levels and PSII inhibition than ATZ. In summary, chitosan coating of nanoatrazine improved the herbicidal activity against B. pilosa plants when applied to the leaves but negatively affected the root-to-shoot translocation of the herbicide. This study opens avenues for further investigations to improve and modify established nanosystems, paving the way for developing novel biological activity patterns.
摘要：
阿特拉津纳米递送系统,由聚（ε-己内酯）（PCL+ATZ）纳米胶囊（NC）组成，在以前的研究中已经证明了活性成分有效地输送到目标植物，导致比传统配方更大的除草剂效力。建立的纳米系统可以被增强或修饰以产生新的生物活性模式。因此,本研究旨在评估壳聚糖包衣PCLATZNCs对除草活性的影响及其与鬼针草植物的相互作用机制。合成了壳聚糖包覆的NC(PCL/CS+ATZ),zeta电位,多分散性，和封装效率。在出苗后温室试验中评估了除草效率，比较PCL/CS+ATZNC(涂层)的效果，PCL+ATZNC(无涂层),和常规阿特拉津（ATZ）对光系统II（PSII）活性和杂草控制。使用水培系统，我们评估了荧光标记的NC的根吸收和芽易位。PCL/CS+ATZ呈现正zeta电位(25mV),200纳米的尺寸，阿特拉津的包封效率高于90%。出苗后除草活性测定显示，与ATZ和PCLATZ相比，在施用后96小时，PSII活性抑制的效率提高了58％。施用后14天的杂草控制评价证实了壳聚糖包衣对除草活性的积极作用，因为在1000ga.i.ha-1下应用PCL/CSATZ比2000ga.i.ha-1下的ATZ和1000ga.i.ha-1下的PCLATZ更好。在水培实验中，用荧光探针标记的壳聚糖包被的NCs积累在根皮层中，少量到达血管筒，并在暴露后72小时内离开。这种行为导致叶片阿特拉津水平和PSII抑制低于ATZ。总之,纳米阿特拉津的壳聚糖涂层改善了施用于叶片时对B.pilosa植物的除草活性，但对除草剂的根-茎易位产生了负面影响。这项研究为进一步研究开辟了途径，以改善和修改已建立的纳米系统，为开发新的生物活性模式铺平道路。
