High-fidelity fluorescent probes for visualizing the inhibitory behavior of selenium on cadmium uptake in rice.

Cadmium (Cd), a widespread and highly toxic environmental contaminant, has seriously impacted the growth of rice and the quality of its products. Hence, it is crucial to monitor and employ robust means to reduce Cd levels in rice, and selenium (Se) has been proven to chelate cadmium ion (Cd2+) in rice with rational use. Herein, for the first time, the reported selenocysteine (Sec) probe NN-Sec and the newly designed Cd2+ probe SCP were chosen as visualization tools to monitor Sec-inhibited Cd2+ uptake in rice. Specifically, reduced fluorescence of rice precultured with Cd2+ was observed by SCP after Se application, while similarly decreased fluorescence of rice pretreated with Se was observed by NN-Sec after Cd2+ addition. The diminished fluorescence indicated the formation of Cd-Se complexes reduced the Cd2+ content in rice. Additionally, it was Cd2+ and Se that entered the rice causing the fluorescence generation, as demonstrated by inductively coupled plasma mass spectrometry (ICP-MS). To conclude, the two probes successfully visualized Se inhibited Cd2+ uptake in rice, which could provide a robust tool for supporting the development of novel organic fertilizers and reagents to reduce Cd2+ content in rice and the environment.

Rational Development of a New Reaction-Based Ratiometric Fluorescent Probe with a Large Stokes Shift for Selective Detection of Bisulfite in Tap Water, Real Food Samples, Onion Tissues, and Zebrafish.

Bisulfite (HSO3-) is usually widely added to tap water and food because it has antibacterial, bleaching, and antioxidant effects. However, its abnormal addition would cause a series of serious diseases related to it. Therefore, development of an effective method for HSO3- detection was of great significance to human health. In this work, a new reaction-based ratiometric fluorescent probe KQ-SO2 was rationally designed, which could be used for the highly selective detection of HSO3- in tap water, real food samples, onion tissues, and zebrafish. Specifically, a positively charged benzo[e]indolium moiety and a carbazole group through a condensation reaction resulted in KQ-SO2, which displayed two well-resolved emission bands separated by 225 nm, fast response (1 min), and high selectivity and sensitivity toward HSO3- upon undergoing the Michael addition reaction, as well as low cytotoxicity in vitro. In addition, KQ-SO2 has been successfully applied for the detection of HSO3- in tap water, real food samples, onion tissues, and zebrafish with satisfactory results. We predict that KQ-SO2 could be used as a powerful tool to reveal the relationship between HSO3- and the human health.