A novel Near-Infrared rhodamine-derivated turn-on fluorescence probe for sensing SO32− detection and their bio-imaging in vitro and in vivo

Sulfur dioxide (SO 2 ) is an important marker in the human body, and maintaining its balance is very significant for human health. The high concentration of SO 2 will cause harm to human health because of the transient nature of SO 2 . To measure the level of SO 2 , it is urgent to find a suitable detection method for the real-time monitoring of sulfite. Herein, we designed and exploited a Near-Infrared (NIR) turn-on fluorescent probe L derived from rhodamine for the detection of SO 3 2− in living cells and zebrafish. The addition of sulfite would attack the 4-position of the carbonyl group of levulinic acid, resulting in the cleavage of the ester bond and the formation of the fluorophore . The intramolecular charge transfer (ICT) was restored thus the monitoring system emitted the corresponding long NIR fluorescence at 646 nm. Probe L had high selectivity, a short response period within 10 min, and the detection limit of 0.6 μM. Besides, Probe L had a long excitation wavelength (>580 nm), which was in favor of more deeply biological imaging properties. Moreover, Probe L had low cell cytotoxicity through MTT assay, thus it was confirmed with good biocompatibility . In addition, probe L could successfully real-time monitor exogenous and endogenous sulfite in living cells, and be applied in zebrafish. The confocal results suggested that probe L had strong potential application prospect of outstanding capabilities for detecting sulfite in clinical diagnostics.