Quantitatively Tracking the Speciation and Dynamics of Selenium Nanoparticles in Rice Plants

The uptake, translocation, and transformation of engineered nanoparticles (ENPs) in plants present significant challenges due to the lack of effective determination methods. This is especially true for selenium nanoparticles (SeNPs), which hold promise for Se-biofortified agriculture and exhibit dynamic behaviors within plant system. Herein, we proposed a novel approach that incorporates enzymic digestion and membrane filtration to selectively extract SeNPs and dissolved Se from plant tissues, employing rice (<i>Oryza sativa</i>) plant as a model. Subsequently, the SeNPs retained on the membrane were quantified using inductively coupled plasma mass spectrometry (ICPMS), while the dissolved Se in the filtrate, including selenite (Se(IV)), selenate (Se(VI)), and seleno amino acid, were analyzed by liquid chromatography coupled with ICPMS (LC-ICPMS). Recoveries of 83.5-91.4% for SeNPs and 73.6-99.4% for dissolved Se at a spiking level of 8 μg/g in quality control samples were obtained. With the established method, it was discovered that SeNPs taken up by rice leaves can transform into Se (IV) and organic Se, and all the Se species could be translocated downward, but only Se (IV) and SeNPs could be excreted through the roots. These findings provide valuable insights into the fate of SeNPs in plants and their related biological responses.