Construction and Application of Fluorescent Probes with Imine Protective Groups for Hypochlorite Detection.

Several fluorescent probes have been designed to detect ClO− in biological systems based on the isomerization mechanism of C = N bonds. Particularly, fluorescein has emerged as an important fluorophore for detecting ClO− because of its unique properties. Previously, we introduced the fluorescein analog <bold>F-1</bold> with an active aldehyde group. In this study, two ClO− fluorescent sensors (<bold>F-2</bold> and <bold>F-3</bold>) with imine groups were designed and synthesized using diaminomaleonitrile and 2-hydrazylbenzothiazole as amines. The electron cloud distribution of <bold>F-2</bold> and <bold>F-3</bold> in ground and excited states was explored via Gaussian calculations, reasonably explaining their photophysical properties. The fluorescence detection of ClO− in solution using the two probes (<bold>F-2</bold> and <bold>F-3</bold>) was realized based on the mechanism of imine deprotection with ClO−. NaClO concentration titration demonstrated that the colorimetric detection of ClO− with the naked eye could be achieved using both <bold>F-2</bold> and <bold>F-3</bold>. However, after adding ClO−, the fluorescence intensity of probe <bold>F-2</bold> increased, whereas that of probe <bold>F-3</bold> first decreased and then increased. Probes <bold>F-2</bold> and <bold>F-3</bold> exhibited good selectivity, anti-interference capability, and sensitivity, with the detection limits of 169.95 and 37.30 µM, respectively. Owing to their low cell toxicity, probes <bold>F-2</bold> and <bold>F-3</bold> can be applied to detect ClO− in vivo. The design approach adopted in this study will further advance the future development of ClO− chemical probes through the removal of C = N bond isomerization. [ABSTRACT FROM AUTHOR]