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• A novel mitochondrion-targeting turn-on fluorescent probe RThy for detecting •OH. • Its turn on mechanism is based on the cleavage of azo-bond by •OH. • The azo group acts not only as a quenching-group but also as recognizing-group of •OH. • It successfully tracked mitochondrion •OH in live cells and zebrafish. Detection and imaging of hydroxyl radical (•OH) with high sensitivity and selectivity in biological systems is of great importance in evaluating the role of •OH plays in the physiological and pathological processes. Herein, a novel mitochondrion-targeting turn-on fluorescent probe RThy , has been developed to detect •OH in living cells and zebrafish. Probe's turn on mechanism is based on the cleavage of azo-bond by •OH. In RThy sensing system, possessing two groups: a lipophilic cation as a targeting-group, and an azo group acts not only as a quenching-group for tunable light absorption but also as recognizing-group of •OH. In the absence of •OH, almost non-fluorescence emission at 550 nm was observed. However, after reaction with •OH, bright fluorescence emission at 550 nm gradually increased with the continuous addition of •OH, displaying ˜50 folds fluorescence intensity enhancements and a quite low detection limit of 8 nM. The selectivity test showed RThy exhibits excellent selectivity toward •OH among all the ROS/RNS species tested. Furthermore, the probe has been successfully employed for imaging •OH in living cells and zebrafish, thus demonstrating RThy as a useful tool for studying •OH in practical sample application, and providing powerful theoretical basis and technical support for investigation of the interaction •OH with physiological and pathology. [ABSTRACT FROM AUTHOR]

Hydrogen sulfide (H 2 S), one of the biologically important gaseous signal molecules, plays an essential role in diverse normal biochemical functions and pathological processes. Herein, an efficient two-photon in and near-infrared out mitochondria-targeting dye has been designed, synthesized and characterized. It is easily synthesized by the condensation reaction (C˭C) of 4-hydroxybenzaldehyde and 6-(diethylamino)−1,2,3,4-tetrahydroxanthylium (mitochondria-targeting), which possesses large two-photon action absorption cross-section ~160 g and high fluorescence quantum yield ~0.15. Encouraged by the results, we proceeded to conjugate this new dye with a H 2 S recognition moiety (4-dinitrobenzene-ether, DNB), on the basis of the intramolecular charge transfer (ICT) strategy, to construct a novel H 2 S fluorescent probe (TP-NIR-HS), which shows a targeting ability with high sensitivity and selectivity, and low cytotoxicity. This new probe was then applied for two-photon imaging of living cells and tissues and showed high imaging resolution and a deep-tissue imaging depth of ~350 µm, thus demonstrating its practical application in biological systems, and providing a valuable theoretical basis and technical support for the study of physiological and pathological functions of H 2 S. [ABSTRACT FROM AUTHOR]

Abstract: We report herein a fluorescent probe for the detection of hydrogen sulfide (H2S) with high sensitivity and selectivity. The probe is installed with double azide groups and displays high sensitivity to H2S (around 120-fold turn-on response). It reacts with H2S with high selectivity over other reactive sulfur, nitrogen, and oxygen species. The probe was also applied to detect H2S in living cells. [Copyright &y& Elsevier]