A coumarin-based near infrared fluorescent probe for the detection of hydrogen sulfide/sulfur dioxide and mitochondrial viscosity

Existing studies have implied that H2S, SO2, and viscosity have potential interrelationships in diseases such as inflammation in the body. Developing fluorescent probes that can simultaneously distinguish and detect the three will be beneficial for relevant workers to explore their potential interrelationships in physiology and pathology. Due to the similar chemical properties of HS− and SO32− (both possessing strong nucleophilic properties), it presents a task with certain challenges that demand careful consideration to detect and differentiate between them using a single probe capable of simultaneously monitoring viscosity changes. In this study, we have designed and prepared a near-infrared fluorescent probe capable of distinguishing and detecting HS−, SO32−, and viscosity, as well as targeting mitochondria. The response of this probe to HS− and SO32− is quenching type and ratio type, respectively, with extremely low detection limits (LOD1 = 0.60 nM for HS−, LOD2 = 1.28 μM for SO32−), fast response time (T1 = 1 min for HS−, T2 = 2 min for SO32−), good selectivity and outstanding anti-interference performance. The monitoring of the viscosity of the probe also shows superior performance. As the viscosity enhances from 0.89 cP to 1412 cP, the fluorescence signal value increases by 52 times, and the trend of fluorescence intensity with viscosity well complies with the Förster-Hoffmann equation. To better understand the response mechanism of the probe to viscosity, we conduct a more in-depth exploration using Gaussian calculations, whose results are in excellent agreement with experimental phenomena. In addition, the probe has successfully achieved monitoring and imaging of HS−, SO32−, and viscosity in Hela cells and 97H cells.