A novel cyclic chalcone fluorescent probe C-PN was synthesized to detect ONOO−. After reaction with peroxynitrite, the double bond of C-PN in the cyclic chalcone structure was disconnected, which caused the change of intramolecular charge transfer (ICT) effect, emitting blue fluorescence and quenching orange red fluorescence. Visible to the naked eye, the color of the probe solution changed. The probe showed low sensitivity (detection limit = 20.2 nm), short response time (less than 60 s) at low concentration of ONOO−, good visibility, and good selectivity and stability for ONOO−.

There is an urgent need to develop highly sensitive and selective fluorescence probes for ONOO- in mitochondria. Herein, we reported a ratiometric fluorescent probe COUS with coumarin-cyanine hybrid as fluorophore and C = C bonds as reaction sites of ONOO-. The probe COUS was sensitive and selective to ONOO-, and had a large fluorescence emission shift (239 nm) as well as a low detection limit (41.88 nM). Moreover, COUS showed the mitochondrial targeting ability, and the targeting moiety could dissociate from the probe when reacting with ONOO-, which enabled COUS to accurately detect ONOO- in mitochondria.

Monitoring intracellular pH using ratiometric fluorescent probes can provide further insights into various biological processes including many diseases. Although ratiometric fluorescent probes with dual emission can efficiently exclude interferences (probe concentration, instrumental efficiency, and environmental conditions) compared with traditional off-on fluorescent probes, development of pH-responsive fluorescent probes with dual emission remains relatively unexplored and challenging. Herein we reported a new hemicyanine-based ratio-metric fluorescent probe 1 with a hydroxyl group. The probe 1 exhibits dual emission and shows a real-time and selective fluorescence response to micro-environmental pH conditions in a range of 6.0 similar to 8.0. Further studies revealed that 1 could exclusively enter and accumulate into mitochondria and monitor the pH microenvironmental conditions through fluorescence imaging in HepG2 cells. We suggest that this probe might be used as a probe to elucidate the role of pH in many physiological processes.

A novel near-infrared fluorescent probe CySNC based on hemicyanine was developed to monitor fluctuations of biothiols in response to oxidative stress caused by heavy metal ion poisoning. In the presence of biothiols, CySNC showed "turn-on " fluorescence at 772 nm with low limits of detection (0.12 mu M for Cys, 0.15 mu M for Hcy and 0.14 mu M for GSH). The probe CySNC had excellent fluorescence response to Cys/Hcy/GSH under physiological conditions and the response time for Cys/Hcy/GSH was 15 min, 35 min and 28 min, respectively. In addition, CySNC was applied for detecting endogenous and exogenous biothiols in mitochondria with low cytotoxicity. More importantly, CySNC successfully visualized biothiols fluctuations induced by Ag+ in mitochondria and confirmed the relationship between oxidative stress and biothiols levels by stimulation with Ag+ and H2O2 in mitochondria, which provided a new train of thought to unravel the mechanisms of heavy ion poisoning.

A novel near-infrared fluorescent probe CyOE based on hemicyanine dye containing acetyl as a recognition site is reported. The probe CyOE shows high selectivity and sensitivity (LOD = 82 nM, 2.58 ppb), as well as good water solubility and quantitative detectability of hydrazine in the concentration range of 0-75 mu M (R-2 = 0.993). Moreover, CyOE has a significant increase in fluorescence at 735 nm with the addition of N2H4, which provides a rapid, colorimetric and gas-phase detection method for N2H4 in both aqueous solution and real water samples. In addition, CyOE is successfully utilized to visualize hydrazine in cells with low cytotoxicity and high cell permeability. (C) 2022 Elsevier B.V. All rights reserved.