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.

115