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Iron (Fe3+) is one of the most essential elements in the human body; deficiency or overdose of Fe3+ may have adverse effects on human health and immunity. Hence, it is essential to establish a sensitive and selective method for ion detection. In this study, novel green fluorescent N-doped carbon dots (N-CDs) were prepared with caffeic acid as the carbon source via a simple hydrothermal method. The solution of the as-prepared N-CDs exhibits 21.5% quantum yield, good salt stability, excellent water solubility, low cytotoxicity and good photobleaching resistance. The N-CDs can be used as a fluorescent probe for the detection of Fe3+ ions in aqueous solutions and bioimaging in living cells. [ABSTRACT FROM AUTHOR]

In this paper, we designed and synthesized a novel TBET-based ratiometric fluorescent chemodosimeter, RH-Au, for Au3+. It was found that the probe RH-Au displayed highly selective, sensitive and naked-eye detection upon the addition of Au3+. The probe RH-Au can be used in the pH range 6.0–7.5 and the detection limit was determined to be as low as 2.91 nM (0.57 ppb). We also demonstrated a successful application of imaging Au3+ in living cells using RH-Au. [ABSTRACT FROM AUTHOR]

Hypochlorite (ClO−) mediates various physiological processes and diseases as a reactive oxygen species. The visualization of the concentration changes of endogenous hypochlorite in cells and in vivo faces great challenges due to the single-signal (spectrum) variation. In this study, a multifunctional ratiometric fluorescent probe IBA was designed and developed for analyzing hypochlorite and Cu2+ independently through a synergetic FRET-PET mechanism. The sensor displayed excellent capacities in anti-interference capacity and sensitivity during the analysis processes of hypochlorite and Cu2+. In particular, IBA showed different fluorescence signal for hypochlorite and Cu2+ meeting the need of independent analysis. And taking advantage of excellent optical properties of the probe in detecting hypochlorite, it successfully monitored the fluctuation of exogenous and endogenous hypochlorite in A549 cells. Moreover, IBA could visualize the changes of hypochlorite in living zebrafish with the fluorescent change between red and green. Overall, the designed novel probe IBA can serve as a potential tool to analyze hypochlorite and Cu2+, and the exploration of the variations of hypochlorite through living imaging shows potential to study the relevant molecular mechanisms and metabolism routes during multifarious physiological activities. [Display omitted] • A ratiometric fluorescent probe was synthesized based on cyanofuran. • The multifunctional sensor for detecting HClO and Cu2+ without crosstalk. • The probe exhibits highly sensitivity and selectivity toward HClO and Cu2+. • The sensor achieves sensing exogenous and endogenous HClO in cells and zebrafish. [ABSTRACT FROM AUTHOR]

Hypochlorous acid plays a very important role in living cells, because it can resist microorganism attack and has a lethal effect on pathogens. The unnormal generation of ClO - can cause tissue damage and corresponding diseases. Detection of ClO - is very necessary in biological systems. In this article, we respectively hybridized the two different water-soluble coumarin (7-hydroxycoumarin and 7-diethylaminocoumarin) fluorophores with a longer-wavelength emissive rhodamine fluorophore to construct an intergrant, and then isothiocyanate was modified with the intergrant to recognized ClO - . The two ratiometric fluorescent probes RHClO-1 and RHClO-2 were developed for ClO - detecting with high selectivity and sensitivity. Especially, the probe RHClO-2 has lower detection limit (42 nM) for ClO - in 5 s. What's more, the probe RHClO-2 was successfully used in monitoring endogenous ClO - in living cells. [ABSTRACT FROM AUTHOR]

Cysteine (Cys) is a biological thiol. Aberrant changes in thiol levels are associated with the development and pathogenesis of various diseases, including liver damage, Alzheimer's disease, weakness, and cardiovascular diseases. Therefore, thiol detection in biological samples has great importance in health monitoring and disease prediction. In this study, we developed a ratiometric fluorescence nanosensor combined with carbon dots (CDs)-doped mesoporous silica and fluorescein-based fluorescent probes loaded in pores for Cys detection. The nanosensor emitted fluorescence at 450 nm upon excitation at 370 nm. In the presence of Cys, the fluorescence emission from the probe could be selectively enhanced, whereas that from CDs could be changed. Thus, a ratiometric fluorescent sensor was developed. This sensor can eliminate the potential influence of background fluorescence and other analyte-independent external environmental factors. The nanosensor was utilized to monitor Cys levels in human serum, and satisfactory results were obtained. Results indicated that the nanosensor can be utilized as an excellent fluorescent nanocomposite material in practical biological applications. [Display omitted] • A new SiCDs was prepared, which presented photostability, high fluorescent quantum yield (QY=72%), pH and salt stability. • A novel ratiometric fluorescence nanosensor based Si-doped carbon dots was prepared. • The ratiometric fluorescence nanosensor had a better selectivity for Cysteine. The limit of detection was 0.73 μM. • The ratiometric nanosensor could be used to detect Cysteine in human serum. [ABSTRACT FROM AUTHOR]

Selenocysteine (Sec) is a primary kind of reactive selenium species in cells, and its vital roles in physiological processes have been characterized. Therefore, the highly effective method for sensing Sec in metabolic processes and selenium-rich food must be developed. This study presents a new fluorescent probe, namely, GSH-NB@AuNPs, for highly selective detection of selenol based on the fluorescence quenching quality on the surface of gold nanoparticles (AuNPs). The probe consists of glutathione (GSH) and Nile blue (NB) moieties assembled on AuNPs. The probe exhibits excellent sensitivity and selectivity for Sec and is applied in imaging endogenous and exogenous Sec in living cells through confocal fluorescence microscopy. The proposed probe provides a promising and powerful method for detecting selenol in foodstuff (such as selenium-rich rice and tea) with the detection limit of 9.5 nM. This study presents a new probe GSH-NB@AuNPs for highly selective detection of selenol based on the fluorescence quenching quality on the surface of gold nanoparticles. Image 1 • A gold nanoparticle-based probe for selenol was developed. • It could sense selenol rapidly with high selectivity and low detection limit (9.5 nM). • The probe could be used for imaging endogenous and exogenous selenol in living cells. • This is the first example using gold nanoparticle-based probe to detect selenol in foodstuff. [ABSTRACT FROM AUTHOR]

Biothiols, such as glutathione (GSH) and cysteine (Cys), play important roles in many physiological processes, and variations in their levels are related to different diseases. Many fluorescence probes have been developed to understand the function of biothiols, but only few of such probes can detect both Cys and GSH. Herein, a new strategy for specific colorimetric and fluorescent detection of Cys and GSH by different cascade reactions was developed. By utilizing this strategy, we designed and synthesized two fluorescent probes, namely, CR1 and CR2 , for detection of Cys and GSH under physiological conditions. CR1 contains a stronger electron-withdrawing substituent group and provides high selectivity and sensitivity for Cys and GSH. This probe is based on the mechanism of Cys-induced native-chemical-ligation-cyclization and GSH-induced transthioesterification–cyclization cascade reactions, with detection limits of 0.029 and 0.371 μM, respectively. CR1 can be successfully applied for imaging Cys and GSH in living cells with low cell toxicity. A new dual-channel trinal-site fluorescent probe CR1 for Cys and GSH was developed based on different cascade reactions. Image 1 • A cascade reaction-based trinal-site probe CR1 was developed for Cys and GSH. • The probe can detect both Cys and GSH with detection limits of 0.029 and 0.371 μM, respectively. • The probe can be used for imaging Cys and GSH in living cells with low cell toxicity. [ABSTRACT FROM AUTHOR]

Herein, we designed and synthesized a luminophor, Rh-F , which is an intergrant of rhodol and 2-hydroxy benzothiazole by introducing a benzothiazole unit onto the ortho-position of the phenolic hydroxy of rhodol. Rh-F exhibited excellent fluorescence properties such as a large Stokes shift (>180 nm) and the synergistic effect of aggregation-induced emission (AIE) and an excited state intramolecular proton transfer (ESIPT) feature. The AIE/ESIPT mechanism was thoroughly explored using X-ray single-crystal structures and photophysical determinations. Furthermore, Rh-F showed a sensitive fluorescence response to Fe2+ with low detection limits of 115.2 nM and high selectivity. Studies of its sensing mechanism indicated that the Fe2+-induced blue-green fluorescence-quenched at 525 nm originates from an irreversible Fe2 + chelate with the oxygen atom of the hydroxyl group and the N atom of the benzothiazole moiety. This blocked the ESIPT process of Rh-F which resulted in the quenching of the fluorescence sensor for Rh-F. A new Benzothiazole-rhodol based fluorescent probe was constructed facilely with ESIPT-induced AIE and an application for Detecting Fe2+ Ion. Unlabelled Image • Rh-F exhibited excellent synergistic effect of AIE and ESIPT feature. • Rh-F achieves "on-off" fluorescence and visual color change for detecting Fe2+. • Rh-F showed a sensitive fluorescence response to Fe2+ with high selectivity. [ABSTRACT FROM AUTHOR]