Design and synthesis of a novel colorimetric fluorescent probe for the selective detection of sulfur dioxide in SH-SY5Y neuroblastoma cells and its applications in traditional Chinese medicines

Sulfur fumigation has attracted extensive attention as one of the important post-harvest processing methods for some traditional Chinese medicines (TCMs) in the last decade. However, sulfur fumigation has recently emerged as a controversial topic due to its potential detrimental effects on the safety and efficacy of TCMs as some sulfur-fumigated TCMs contain numerous sulfur dioxide derivatives; moreover, high levels of sulfur dioxide derivatives can cause some diseases and dangerous environmental pollution. In this study, a DTCC probe with a fast response time, low limit of detection and a high fluorescence quantum yield was designed and synthesized to detect SO2 derivatives based on the coumarin-thiophene dye, which was fused with a coumarin moiety and 2-thiophenecarboxaldehyde. The probe DTCC exhibited a fast response time (less than 10 s), satisfactory selectivity for SO2 derivatives in the presence of other ROS and excellent sensitivity for SO2 derivatives with a low limit of detection (0.23 M) as well as a wide linear range (0-100 M). Furthermore, the probe DTCC was successfully applied in fluorescence imaging in SH-SY5Y neuroblastoma cells with excellent membrane permeability and stability. It was also employed in monitoring the total SO2 derivatives in several real TCM samples. These results illustrate that the probe DTCC has an excellent capability for monitoring SO2 derivatives in living cells and real TCM samples.