Intracellular reactive oxygen species and reactive sulfur play a vital role in regulating redox homeostasis and maintaining cell functions. Sulfur dioxide (SO2) has emerged as an important gas signal molecule recently, which is not only a potential reducing agent but also a potential inductor of oxidative stress in organisms. Due to high reactivity, peroxynitrite (ONOO–) could act on many biomolecules, such as proteins, lipids, and nucleic acids, and cause irreversible damage, eventually leading to cell apoptosis or necrosis. In order to further illuminate the dichotomous role of SO2 under oxidative stress induced by ONOO–, we designed the first dual-site fluorescent sensor (NIR-GYf) for separate or continuous detection of SO2 and ONOO–. NIR-GYf was successfully used for cell imaging of endogenous SO2 and ONOO–. In addition, western blotting analysis was used to verify the oxidation and antioxidation of SO2 and its dichotomous biological influence. Finally, NIR-GYf was integrated with multiple Boolean logic operations to construct an advanced analysis device, thereby realizing the direct analysis of SO2 and ONOO– levels.

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As a momentous gas signal molecule, sulfur dioxide (SO 2 ) participates in diverse physiological activities. Excess SO 2 will cause an apparent decrease in the level of intracellular glutathione (GSH), thereby damaging the body's antioxidant defense system. In addition, endogenous SO 2 can be generated from GSH by reacting with thiosulfate (S 2 O 3 2− ) and enzymatically reduced to cysteine (Cys), a synthetic precursor of GSH. In view of their close correlation, a two-photon (TP) mitochondriatargeted multifunctional fluorescence sensor Mito-Na-BP was rationally designed and synthesized for detecting SO 2 and GSH simultaneously. Under single-wavelength excitation, the sensor responded to GSH-SO 2 and SO 2 -GSH continuously with blueshifted and green fluorescence-enhanced signal modes, respectively, not just to GSH (enhanced) and SO 2 (quenched) at 638 nm with a completely converse response tendency. Given its favorable spectral performance (high sensitivity, superior selectivity, and fast response rate) at physiological pH, Mito-Na-BP has been successfully applied in monitoring the level fluctuation of GSH affected from high-dose SO 2 and visualizing in real time the metabolic process of GSH to SO 2 by TP imaging. It is expected that this research will provide a convenient and efficient tool for elucidating intricate relationships of GSH and SO 2 and facilitate further exploration of their functions in biomedicine.

A novel Gd(iii) complex-based MRI contrast agent GdL has been designed and synthesized, which exhibited a much higher relaxivity than the commercially used Magnevist®, good water solubility, excellent stability, high biosafety and biocompatibility.