Reversible Ni2+ fluorescent probe based on ICT mechanism and its application in bio-imaging of Zebrafish

[Display omitted] •A new lysosome-targeted“turn-off”fluorescent probe NIC was developed for detecting Ni2+.•The process of monitoring Ni2+ is reversible, and the fluorescence is restored by EDTA.•NIC possesses rapid response capability to Ni2+ within 40 s and simple synthesis process.•NIC is successfully applied for imagingof Ni2+ in Hela cells and Zebrafish. To determine the relevant mechanism of Ni2+ on cells in the physiological and pathological process, a novel probe (NIC) was developed, which could label the lysosomes and was applied for the first time to the imaging of Ni2+ in Zebrafish. NIC was designed and synthesized with a N-hydroxynaphthalimide as the fluorophore and morpholine as the lysosomal targeting group. The probe used hydroxyl oxygen and oxygen on the amide as the coordination site of Ni2+. With the addition of Ni2+, the intramolecular charge transfer (ICT) effect from hydroxy to naphthalimide disappeared, and the fluorescence intensity of NIC gradually decreased, accompanied by a noticeable color change (from faint yellow to orange). The experimental results demonstrated that NIC could reversibly monitor Ni2+ in Hela cells and Zebrafish. The NIC probe showed good selectivity, low cytotoxicity, and fast response (