Fluorescence distinguishing of SO2 derivatives and Cys/GSH from multi-channel signal patterns and visual sensing based on smartphone in living cells and environment

Sulfur dioxide (SO2), cysteine (Cys) and glutathione (GSH), which perform crucial actions in regulating the balance of human, are closely related reactive sulfur species (RSS). Moreover, SO2 is one of the most concerned air pollutants, which is easily soluble in water and forms its derivatives. Therefore, it is highly desirable to differentiate SO2 derivatives and Cys/GSH in living cells and environment. Herein, a new near-infrared (NIR) mitochondria-targeted fluorescent probe, NIR-CG, which could distinguish SO2 derivatives and Cys/GSH by using multiple sets of signal patterns under single excitation was reported. NIR-CG exhibited different fluorescence signal modes to SO32− and Cys/GSH with low limit of detection (17.1 nM for SO32−, 17.3 nM for Cys and 25.9 nM for GSH). The recognition mechanisms of NIR-CG to SO32− and Cys/GSH were verified by HRMS, 1H NMR and DFT calculation. NIR-CG had good ability of mitochondrial targeted and fluorescence imaging in cells. What's more, NIR-CG showed great recovery rates (101–104%) in the determination of SO32− in actual water samples. It was worth noting that NIR-CG-based paper strip successfully realized the visual quantitative detection of SO32− and Cys/GSH by use of smartphone, which offered a novel method to develop powerful sensing platform.