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Alkaline phosphatase (ALP) is an essential enzyme in various tissues, which has been reported to be extensively involved in various physiological and pathological processes. Fluorescent probe assays carried out in vivo are desirable for monitoring the ALP activity. In this study, a novel red-light fluorescent DHP probe, which exhibited good selectivity and high sensitivity, for monitoring the ALP activity in real time was described. The DHP probe exhibited good water solubility, and the detection limit of ALP was determined as 0.031 U/L; this value is almost less than those of the other probes reported previously. The probe exhibited high selectivity, which will not interfere with various enzymes and amino acids. Moreover, the sensing and luminescence mechanisms of ALP to DHP was investigated by density functional theory (DFT) and time-dependent DFT. Furthermore, the DHP probe was applied for the detection of endogenous ALP in BEL-7402 cells, and the fluctuation of the ALP levels in BEL-7402 and HEK 293 T cells was successfully tracked by fluorescence microscopy. [ABSTRACT FROM AUTHOR]

• Development of a novel red-emitting fluorescent probe (HSA) for the detection of Cys. • The probe can high sensitivity detect Cys with a low LOD. • Successfully verified the experimental results by the theoretical calculation study. • The probe can be used for exogenous Cys monitoring and endogenous Cys cell imaging experiments. Herein, we synthesized a red-emitting fluorescence turn-on probe (HSA) for specific detection of cysteine (Cys) over other biothiols (glutathione (GSH) and homocysteine (Hcy)). The acrylate group was chosen as the recognition site for specific discrimination of Cys. Absorption and emission spectra display a high selectivity towards Cys over GSH/Hcy, organic small-molecule interfering substances and anions, with a high sensitivity towards Cys (0.12 μM) in 1% ethanol-containing PBS buffer solution (25 mM, pH = 7.4). Density functional theory (DFT) and time-dependent DFT (TDDFT) calculations were conducted to clarify the luminescence mechanism of the probe. Furthermore, the probe was successfully applied to the determination of free Cys in human serum and the fluorescence imaging of endogenous Cys in living cells. [ABSTRACT FROM AUTHOR]

We designed and synthesized a water-soluble near-infrared (NIR) fluorescent probe with the recognition unit of the cyanine-like structure and acrylate group. Through an aromatic ring nucleophilic substitution reaction based on sulfhydryl moiety, an off-on fluorescence response toward cysteine (Cys) was realized. The probe exhibited excellent spectral performance with an emission wavelength of 720 nm and a detection limit of 0.20 μM. The spectral properties, selectivity and anti-interference performance of the probe were systematically investigated. Density functional theory (DFT) calculations were conducted to clarify the luminescence mechanism of the probe. Furthermore, the probe was successfully applied to the detection of free Cys in human serum and the NIR imaging of endogenous Cys in living cells. Thus, the probe has a promising application prospect in clinical diagnosis and fluorescence imaging. Image 1 • Development of a novel near-infrared fluorophore (MTR). • Design and application of fluorescent probe (MTR-C) for the detection of endogenous Cys. • Successfully verified the experimental results by the theoretical calculation study. • Successfully tracked the fluctuations of Cys levels in BEL-7402 cells. [ABSTRACT FROM AUTHOR]