Dual-mode chemosensor for the fluorescence detection of zinc and hypochlorite on a fluorescein backbone and its cell-imaging applications.

Fluorescein coupled with 3-(aminomethyl)-4,6-dimethylpyridin-2(1)-one (FAD) was synthesized for the selective recognition of Zn over other interfering metal ions in acetonitrile/aqueous buffer (1 : 1). Interestingly, there was a significant fluorescence enhancement of FAD in association with Zn at 426 nm by strong chelation-induced fluorescence enhancement (CHEF) without interrupting the cyclic spirolactam ring. A binding stoichiometric ratio of 1 : 2 for the ligand FAD with metal Zn was proven by a Jobs plot. However, the cyclic spirolactam ring was opened by hypochlorite (OCl) as well as oxidative cleavage of the imine bond, which resulted in the emission enhancement of the wavelength at 520 nm. The binding constant and detection limit of FAD towards Zn were determined to be 1 × 10 M and 1.79 μM, respectively, and the detection limit for OCl was determined as 2.24 μM. We introduced here a dual-mode chemosensor FAD having both the reactive functionalities for the simultaneous detection of Zn and OCl by employing a metal coordination (Zn) and analytes (OCl) induced chemodosimetric approach, respectively. Furthermore, for the practical application, we studied the fluorescence imaging inside HeLa cells by using FAD, which demonstrated it can be very useful as a selective and sensitive fluorescent probe for zinc.