A facile ratiometric near-infrared fluorescent probe using conjugated 1,8-naphthalimide and dicyanoisophorone with a vinylene linker for detection and bioimaging of hypochlorite.

A new ratiometric near-infrared fluorescent probe 3 for detecting ClO- using conjugated 1,8-naphthalimide and dicyanoisophorone with a vinylene linker was reported. Probe 3 exhibited a ratiometric signal (I705/I535), large Stokes shift (205 nm), high selectivity and sensitivity, low detection limit (0.738 μM), rapid response (within 3 s) and good biocompatibility. The sensing mechanism involved the oxidation of the olefin double bond by ClO- to release the initial N-butyl-4-hydroxyl-3-formyl-1,8-naphthalimide 1, followed by inhibition of an ICT process from the electron-donor 4-hydroxyl-1,8-naphthalimide to dicyanoisophorone. At the same time, the probe 3-loaded test strips were applied in sensing of ClO- with moderate "naked-eye" color changes. Additionally, probe 3 has been successfully used for ratiometric bioimaging of ClO- in HeLa cells with low cytotoxicity.