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Real-time monitoring of the cytochrome P450 1A1 (CYP1A1) activity in complex biological systems via a practical tool is highly sought after because of its significant role in the metabolism and bioactivation of various xenobiotics. Herein, according to slight differences in the 3D structure and substrate preference between CYP1A1 and its homologous CYP1A2, a series of novel ratiometric fluorescent probes were designed and synthesized using 1,8-naphthalimide because of its trait of naked-eye visualization and ratiometric fluorescence to achieve the detection of CYP1A1 in biological samples. Among these probes, NEiPN showed good water solubility, highly isoform selectivity and great sensitivity (LOD = 0.04874 nM) for CYP1A1 under simulated physiological conditions, which makes it favorable for monitoring CYP1A1 in vivo. Remarkably, NEiPN exhibited excellent reproducibility when it was used to detect the CYP1A1 content in human liver microsomes, which indicated that it has a great potential for quantifying the CYP1A1 content in real biological samples. Furthermore, NEiPN showed relatively low cytotoxicity and has been successfully applied in biological imaging in living cells and zebrafish. These findings indicate that NEiPN is capable of real-time monitoring of the activity of endogenous CYP1A1, which could provide support for CYP1A1-associated pathological processes. [ABSTRACT FROM AUTHOR]

Hydrogen sulfide and cysteine are momentous endogenous regulators of many physiological processes and maintain a dynamic balance of redox in living organisms. To investigate the inter-relationship of them in vivo, there is a pressing need to develop analytical molecular tools to identify related biomolecules. We construct a mitochondria-targeted single fluorescence probe (Mit-CM) for separately and continuously visualizing H 2 S, Cys and H 2 S/Cys with multi-response fluorescence signals. Mit-CM has the following advantages: (Ⅰ) colorimetric and ratiometric: two well-separated emission bands can ensure accurate detection of the analyte and significant color changes contribute to rapid identification of the analyte by the naked eye; (Ⅱ) mitochondrial localization: study the physiological functions of H 2 S and Cys in mitochondria; (Ⅲ) separate and continuous detection of H 2 S and Cys: reveal the inter-relationship and interconversion of them in biological system. Moreover, the desirable attributes of low cytotoxicity, better biocompatibility and excellent mitochondria enrichment ability indicate that Mit-CM can be employed to achieve detection and observe distribution of H 2 S, Cys and H 2 S/Cys in living organism. Image 1 • Ratiometric and colorimetric: contribute to accurate detection and rapid discrimination of the analyte. • Mitochondrial localization: study the physiological function of H 2 S and Cys in the mitochondria. • Separate and continuous detection of H 2 S and Cys: reveal the inter-relationship and interconversion of them in biological systems. [ABSTRACT FROM AUTHOR]

• Detecting CYP3A5 activity using fluorescent probe for the first time. • Excellent sensitivity (LOD = 0.04581 nM) was realized in Hcy-Br. • Hcy-Br possessing Preferable mitochondria-specific targeting (Rr = 0.8746). • Visualization of living cells and tumor-bearing mice was achieved in Hcy-Br. Cytochrome P450 (CYP) 3A5 as the most important CYPs in the CYP3A isoform, is polymorphic and plays a significant role in drug metabolism. Herein, two novel enzyme-activatable near-infrared (NIR) ratiometric fluorescent probes (Hcy-Br and Hcy-Cl) are designed and synthesized to measure the activity of CYP3A5 in complex biological systems. Hcy-Br possesses excellent sensitivity in response to CYP3A5 enzyme with the LOD = 0.04903 nM and could quickly reach equilibrium within 30 min. The ability of targeting mitochondria, along with preferable Pearson's correlation coefficients (Rr) of 0.8746, is realized in Hcy-Br. The application of Hcy-Br in living cells and tumor-bearing mice is also achieved successfully for monitoring endogenous CYP3A5 activity. Detecting CYP3A5 activity in living system via fluorescent probe, to the best of our knowledge, is reported for the first time. These findings suggest that Hcy-Br could be served as a useful tool for selectively detecting the activity of endogenous CYP3A5 in vivo, providing assistance for investigating the function of CYP3A5 in drug metabolism and pathologic process. [ABSTRACT FROM AUTHOR]

Reactive sulfur species (RSS), primarily containing glutathione (GSH), cysteine (Cys), hydrogen sulfide (H 2 S) and hydrogen polysulfides (H 2 S n , n > 1), were crucial endogenous biological signal molecules. Among them, H 2 S and H 2 S n played extremely momentous roles in many physiological and pathological processes. Limited by the vivo environmental diversity and complexity, it was highly desirable to rely on the single fluorescence probe platform to visualize H 2 S n and H 2 S according different fluorescence signals. Herein, we reported a two-photon excited fluorescent probe MC-S n that had the following merits: (Ⅰ) ratiometric and colorimetric: reducing detection errors and conducting visual analysis; (Ⅱ) two-photon microscope: better performance in vivo and vitro imaging; (Ⅲ) two specific sulfide reaction sites: studying on the mutual transformation of H 2 S n and H 2 S in biological systems. Furthermore, take advantages of low cytotoxicity (cell viability ≥ 85.99%), low limit of detection (21 nM), significant photostability, excellent pH stability, quick response behavior (175 s) and high penetration depth (110 μm), MC-S n can be employed to visualize endogenous and exogenous H 2 S n and H 2 S in cells, liver tissues and zebrafish. • Ratiometric and colorimetric: reducing detection errors and conducting visual analysis. • Two-photon microscope: better performance in vivo and vitro imaging. • Two specific sulfide reaction sites: studying on the mutual transformation of H2Sn and H2S in biological systems. • Low limit of detection (21 nM) and high penetration depth (110 μm). [ABSTRACT FROM AUTHOR]