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[Display omitted] • This is a rhodamine-based "off-on" fluorescent probe with a novel structure to detect tyrosinase activity. • The rhodamine fluorophore structure was improved by expanding the π-conjugation system, asymmetric synthesis, and fixing the N terminus, which greatly improved the fluorescence quantum yield of the fluorophore. • The use of 3-hydroxybenzyl oxygen as the recognition group of the probe effectively avoids the interference of reactive oxygen species in the detection of tyrosinase and improves the selectivity of the probe for tyrosinase. Tyrosinase (TYR) detection will be crucial in the prevention and early diagnosis of some illnesses, including epilepsy, albinism, and melanoma, due to the close linkage of abnormal expression of TYR with the occurrence of these diseases. Therefore, how to obtain a fluorescent probe that has a high fluorescence quantum yield and high specificity for detecting TYR activity will be of significance. In this work, we improved the rhodamine structure by expanding the π-conjugation system and using asymmetric synthesis to provide a fluorescent probe with good optical properties for the specific detection of TYR. The fluorescence quantum yield of fluorophore released from the probe by the enzymatic reaction with TYR was as high as 0.22, which was significantly greater than that of other previously reported fluorescent probes. We also chose 3-hydroxybenzyl oxygen as the recognition group, which can successfully lessen the interference from reactive oxygen species (ROS). At the same time, the probe demonstrated great sensitivity in detecting TYR activity, and the detection limit of TYR for the probe was calculated to be 0.45 U/mL. In addition, the probe has currently been successfully utilized to evaluate TYR activity in cells. Therefore, this probe is anticipated to be crucial in identifying TYR activity in challenging settings. [ABSTRACT FROM AUTHOR]

[Display omitted] • A fluorescent probe DPY simultaneously responds to GSH/ONOO-with dual-emission. • DPY can co-target ER and Mito, tracking the GSH-ONOO- crosstalk in both organelles. • Fluorescent imaging in living cells discloses the ER-Mito contact change in ferroptosis. Ferroptosis is a recently proposed cell death mechanism characterized by iron-dependent lipid peroxidation. Reactive oxygen/nitrogen species (ROS/RNS) are responsible for lipid peroxidation in the endoplasmic reticulum (ER) and mitochondria (Mito) and result in glutathione (GSH) depletion in ferroptosis. Peroxynitrite (ONOO–) is a highly reactive RNS, and its equilibrium with GSH is vital to maintain redox homeostasis in ER and Mito. The GSH-ONOO– crosstalk is thus essential to understand the changes of ER and Mito in cells during ferroptosis. Further, the interplay between ER and Mito, the ER–Mito contact, is expected to change during ferroptosis, which has been observed in other cell death forms but not in ferroptosis. Here, we report a new fluorescent probe (DPY) with a dual response to GSH and ONOO– in both the ER and Mito. Fluorescence of DPY can be triggered by GSH and ONOO– at 608 (red) and 456 nm (blue) excited at 561 and 405 nm, respectively. The structure of DPY contains both the ER- and Mito-targeting units, and simultaneous anchoring of the probe is allowed in duple organelles. Application of the probe in cell imaging firstly reveals GSH/ONOO– crosstalk in ER and Mito in erastin- and RSL3-induced cells during ferroptosis. And a closer ER–Mito contact is also observed in hepatic cells during ferroptosis. Further studies on the blue-red merged images disclose the ER-Mito contact change in cells during ferroptosis through the observed difference in Pearson correlation coefficients. A similar trend is also verified in acetaminophen-induced ferroptosis. [ABSTRACT FROM AUTHOR]

Phosphorus and nitrogen doped carbon dots (PN-CDs) were conveniently prepared by carbonization of adenosine-5′-triphosphate using a hydrothermal treatment. The PN-CDs with P/C atomic ratio of ca. 9.2/100 emit blue luminescence with high quantum yields of up to 23.5%. The PN-CDs were used as a novel sensing platform for live cell imaging of reactive oxygen species (ROS) and reactive nitrogen species (RNS), including ClO − , ONOO − , and NO in macrophages. The nanosensor design is based on our new finding that the strong fluorescence of the PN-CDs can be sensitively and selectively quenched by ROS and RNS both in vitro and in vivo. These results reveal that the PN-CDs can serve as a sensitive sensor for rapid imaging of ROS and RNS signaling with high selectivity and contrast. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel benzocoumarin-based fluorescent probe BL for monitoring HOCl was designed and synthesized. • BL exhibits simple synthesis, excellent selectivity, fast response (<60 s), high sensitivity (DL, 5.64 nM). • BL was successfully applied to detect HClO spiked in tap water, 84 disinfectants and lake water, and has achieved satisfying recovery rates. • BL could readily fabricate solid-state visual sensors to be used to convenient detect HClO. • BL was nontoxic andsuccessfully used to monitor the variations of endogenous/exogenous HOCl in live RAW 264.7 macrophages. Hypochlorous acid (HOCl) is widely used in daily production and life. It is also a kind of endogenously produced reactive oxygen species (ROS) in the human immune system, plays a crucial role in many pathophysiological processes. This work designed and synthesized a novel based on benzocoumarin fluorescent probe BL for specific detection HOCl. BL has brilliant selectivity, high sensitivity (5.64 nM), fast response (60 s), moderate water-solubility. The intramolecular charge transfer (ICT) sensing mechanism of BL has been verified by fluorescence, UV, MS, and density functional theory (DFT) calculations. BL can make into a solid-state visual sensor to detect HOCl conveniently. BL was also applied to detect HClO spiked in tap water, 84 disinfectants, lake water, and satisfying recovery rates. Finally, BL was low toxic and used to track the variations of endogenous/exogenous HClO in living cells successfully. Totally, BL provides a powerful and reliable monitoring tool to reveal the biological functions of HOCl and ensure safe use. [ABSTRACT FROM AUTHOR]

In this work, a new turn-on near-infrared fluorescent probe based on N , N -dimethylaniline as a donor and pyridinium group as an acceptor has been successfully constructed for superoxide anion detection, which exhibits a remarkable fluorescence enhancement with a low limit of detection and an excellent mitochondrial targeting effect in MCF-7 cells with good biocompatibility after treatment of lipopolysaccharide. [Display omitted] • A new fluorescent probe DMPS-O for O 2 •- detection with a large Stokes shift was developed. • DMPS-O showed a remarkable near-infrared fluorescence enhancement after reacting with O 2 •-. • DMPS-O was suitable for detecting endogenous O 2 •- in MCF-7 cells. • DMPS-O was capable of locating mitochondria in cells. Superoxide anion (O 2 •-), as a kind of crucial reactive oxygen species (ROS), often causes a series of oxidative damage and various biological dysfunction when it is excessive in cells. Compared with other detection methods, fluorescence detection is often used for cell imaging due to its high temporal and spatial resolution. Hence, a novel "turn-on" fluorescent probe DMPS-O based on N , N -dimethylaniline as a donor and pyridinium group as an acceptor was designed and synthesized to detect superoxide anion. DMPS-O showed a remarkable fluorescence enhancement in the near-infrared region and a large Stokes shift after reacting with superoxide anion and its limit of detection was calculated to be 22.2 nM. Finally, CCK-8 and confocal fluorescence imaging experiments revealed that the fluorescent probe DMPS-O with low cytotoxicity was suitable for detecting endogenous superoxide anions and locating mitochondria in the MCF-7 and HepG2 cells. [ABSTRACT FROM AUTHOR]