State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University , Nanjing, Jiangsu Province 210023, China.
Environ Sci Technol. 2016 Jul 19;50(14):7799-807. doi: 10.1021/acs.est.6b01645. Epub 2016 Jul 8.
Calcium plays versatile roles in aquatic ecosystems. In this study, we investigated its effects on the uptake of polyacrylate-coated TiO2 nanoparticles (PAA-TiO2-NPs) by the water flea (cladoceran) Daphnia magna. Particle distribution in these daphnids was also visualized using synchrotron radiation-based micro X-ray fluorescence spectroscopy, transmission electron microscopy, and scanning electron microscopy. At low ambient Ca concentrations in the experimental medium ([Ca]dis), PAA-TiO2-NPs were well dispersed and distributed throughout the daphnid; the particle concentration was highest in the abdominal zone and the gut, as a result of endocytosis and passive drinking of the nanoparticles, respectively. Further, Ca induced PAA-TiO2-NP uptake as a result of the increased Ca influx. At a high [Ca]dis, the PAA-TiO2-NPs formed micrometer-sized aggregates that were ingested by D. magna and concentrated only in its gut, independent of the Ca influx. Our results demonstrated the multiple effects of Ca on nanoparticle bioaccumulation. Specifically, well-dispersed nanoparticles were taken up by D. magna through endocytosis and passive drinking whereas the uptake of micrometer-sized aggregates relied on active ingestion.
钙在水生生态系统中发挥着多种作用。在本研究中，我们研究了钙对水蚤（枝角类）大型溞摄取聚丙烯酸包覆的 TiO2 纳米颗粒（PAA-TiO2-NPs）的影响。还使用同步辐射微 X 射线荧光光谱、透射电子显微镜和扫描电子显微镜观察了这些溞类体内的颗粒分布。在实验介质中环境钙浓度较低时（[Ca]dis），PAA-TiO2-NPs 很好地分散并分布在整个溞体内；由于内吞作用和纳米颗粒的被动摄取，颗粒浓度在腹部区域和肠道中最高。此外，由于 Ca 流入的增加，Ca 诱导了 PAA-TiO2-NP 的摄取。在高[Ca]dis 时，PAA-TiO2-NPs 形成了微米级的聚集体，被大型溞摄取，并仅集中在其肠道中，而与 Ca 流入无关。我们的结果表明 Ca 对纳米颗粒生物累积有多种影响。具体来说，分散良好的纳米颗粒通过内吞作用和被动摄取被大型溞摄取，而微米级聚集体的摄取则依赖于主动摄取。
