A mitochondria-oriented fluorescent probe for ultrafast and ratiometric detection of HSO3- based on naphthalimide-hemicyanine

A novel ratiometric and red emitting fluorescent probe for naked-eye detection of HSO3- was developed based on Fluorescence Resonance Energy Transfer (FRET) from naphthalimide to hemicyanine. Naphthalimide was linked to the 1-position of the indole moiety via the ethylketone group. C?C double bonds conjugated with indole and 4-(piperazin-1-yl)benzene were applied as the recognizer and the probe displayed strong red fluorescence and week green fluorescence. Upon the addition of HSO3-, the obvious red fluorescence at 590 nm was quenched completely while the green fluorescence at 527 nm recovered. The selective probe showed excellent sensitivity to HSO3- with a low detection limit (LOD) of 61.2 nM and a fast response time of 30 s. The sensing mechanism proved to be Michael addition, which was confirmed by H-1 NMR. Moreover, the probe was mitochondria-oriented and employed for monitoring exogenous HSO3- in living cells. Overall the excellent performance of the probe proved great potential for practical and biological application.