A benzothiophene-based fluorescent probe with dual-functional to polarity and cyanide for practical applications in living cells and real water samples.

Polarity is a significant intracellular environmental parameter associated with cancer, while cyanide (CN) is known to be highly toxic to humans. In this work, we designed a dual-functional fluorescent probe (TPABT) for simultaneous detection of polarity and CN. As a polarity sensor, the probe exhibits NIR emission at 766 nm in 1,4-dioxane (non-polar solvent), whose emission intensity is 71-fold stronger than that in water (polar solvent). Meanwhile, the fluorescence intensity and quantum yield are linearly related to solvent polarity, confirming the polarity response ability of TPABT. For cell polarity detection, low cytotoxicity and polarity sensitivity of probe enable the applications for differentiating cancer cells (HeLa, 4TI) from normal cells (HUV, 3 T3) and monitoring the polarity changes of 4TI cells. As a CN sensor, TPABT displays a turn-on fluorescence at 640 nm upon the addition of CN, with advantages of anti-interference, response in aqueous media and low detection limit (22 nM). Additionally, we further explored the practical applications of TPABT for CN determination in three types of real water samples (drinking water, tap water and lake water) and living cells. Notably, TPABT responses to polarity and CN in two independent fluorescence channels of 766 and 640 nm, respectively, ensuring the dual functions for polarity and CN sensing. Consequently, this multi-responsive fluorescent probe TPABT is promising to diagnose polarity-related diseases and detect CN in real environments.