A phenoxazine-based fluorescent chemosensor for dual channel detection of Cd²⁺ and CN⁻ ions and its application to bio-imaging in live cells and zebrafish

A simple phenoxazine-based fluorescence chemosensor N-(4-((4-((5-oxo-5H-benzo [a]phenoxazin-6-yl)amino)phenyl)sulfonyl)phenyl)furan-2-carboxamide (NPC) was developed for discriminative detection of Cd²⁺ and CN⁻ ions. This easily available chemosensor was synthesized by adding a furan-2-carboxamide group to a phenoxazine fluorophore and a phenyl sulfonyl chelating site. The sensor NPC exhibited turn-on fluorescence emission for Cd²⁺, and the obtained NPC–Cd²⁺ complex detected CN⁻ via turn-off fluorescence response with 2:1 binding stoichiometry in CH₃CN/H₂O (99:1 v/v) medium by fluorescence spectroscopy. The detection limits of Cd²⁺ and CN⁻ were 0.60 μM and 0.145 μM, respectively, which were significantly lower than the World Health Organization guidelines. The proposed mechanism of sensor NPC was additionally supported by NMR, FT-IR analyses, DFT and a UV/visible titration studies. Furthermore, the sensor NPC has been successfully demonstrated as a biomarker for detecting Cd²⁺ in live cells and zebrafish larvae.