Civil and Environmental Engineering, Carnegie Mellon University , Pittsburgh, Pennsylvania 15213, United States.
Future Industries Institute, University of South Australia , Mawson Lakes, South Australia 5095, Australia.
Environ Sci Technol. 2017 Jul 5;51(13):7361-7368. doi: 10.1021/acs.est.7b00813. Epub 2017 Jun 16.
Nanoparticle (NP) physiochemical properties, including surface charge, affect cellular uptake, translocation, and tissue localization. To evaluate the influence of surface charge on NP uptake by plants, wheat seedlings were hydroponically exposed to 20 mg/L of ∼4 nm CeO NPs functionalized with positively charged, negatively charged, and neutral dextran coatings. Fresh, hydrated roots and leaves were analyzed at various time points over 34 h using fluorescence X-ray absorption near-edge spectroscopy to provide laterally resolved spatial distribution and speciation of Ce. A 15-20% reduction from Ce(IV) to Ce(III) was observed in both roots and leaves, independent of NP surface charge. Because of its higher affinity with negatively charged cell walls, CeO(+) NPs adhered to the plant roots the strongest. After 34 h, CeO(-), and CeO(0) NP exposed plants had higher Ce leaf concentrations than the plants exposed to CeO(+) NPs. Whereas Ce was found mostly in the leaf veins of the CeO(-) NP exposed plant, Ce was found in clusters in the nonvascular leaf tissue of the CeO(0) NP exposed plant. These results provide important information for understanding mechanisms responsible for plant uptake, transformation, and translocation of NPs, and suggest that NP coatings can be designed to target NPs to specific parts of plants.
纳米颗粒 (NP) 的物理化学性质，包括表面电荷，会影响细胞摄取、转运和组织定位。为了评估表面电荷对植物摄取 NP 的影响，将小麦幼苗进行水培暴露于 20 mg/L 的约 4nm CeO NPs，这些 NPs 带有带正电荷、带负电荷和中性葡聚糖涂层。在 34 小时内的不同时间点，使用荧光 X 射线吸收近边光谱法分析新鲜、水合的根和叶，以提供 Ce 的横向分辨空间分布和形态。在根和叶中，Ce(IV)到 Ce(III)的还原率均降低了 15-20%，与 NP 表面电荷无关。由于其与带负电荷的细胞壁具有更高的亲和力，CeO(+) NPs 最强烈地附着在植物根部。34 小时后，暴露于 CeO(-)和 CeO(0) NP 的植物叶片中的 Ce 浓度高于暴露于 CeO(+) NP 的植物。在暴露于 CeO(-) NP 的植物中，Ce 主要存在于叶脉中，而在暴露于 CeO(0) NP 的植物中，Ce 则存在于非叶脉组织的簇中。这些结果为理解植物摄取、转化和转运 NP 的机制提供了重要信息，并表明可以设计 NP 涂层将 NP 靶向到植物的特定部位。
