A highly selective ratiometric fluorescent and chromogenic probe for sulfite and its applications in imaging of living cells and zebrafish in vivo

•A ratiometric fluorescent probe CEBI was designed and synthesized for SO32− detection.•The probe exhibits highly sensitivity and selectivity toward SO32−.•HR-ESI-MS, 1H NMR and DFT/TDDFT calculations verified the binding mode and reaction mechanism of CEBI with SO32−.•The probe show low cytotoxicity and can be applied in cells and zebrafish.

Herein we report a new carbazole-benzo[e]indolium dye (CEBI) as a ratiometric fluorescent and chromogenic probe for sulfite (SO32−) detection based on intramolecular charge transfer (ICT) mechanism. Upon treatment with SO32−, the probe CEBI displayed a remarkable fluorescence ratiometric response (∼560-fold fluorescenc enhancement) together with a color change from red to weak red and a large shift (135 nm) in emission wavelength. The experimentally observed changes in the spectral features of the probe upon addition of SO32− were systematically studied using high resolution electrospray ionization mass spectrometry (HR-ESI-MS), proton nuclear magnetic resonance (1H NMR), and time-dependent density functional theory (TDDFT) calculations. We found a linear relationship between the ratio of fluorescence intensities at 465 nm and 600 nm (F465/F600) and SO32− concentration over the range of 0-40 μM with a detection limit of 0.025 μM. Moreover, the novel probe demonstrated fluorescence imaging of SO32− in living cells and zebrafish, suggesting its potential in clinical diagnostics.

Graphical abstractDownload high-res image (115KB)Download full-size image