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Polydopamine fluorescent organic nanomaterials present unique physicochemical and biological properties, which have great potential application in bio-imaging and chemical sensors. Here, folic acid (FA) adjustive polydopamine (PDA) fluorescent organic nanoparticles (FA-PDA FONs) were prepared by a facile one-pot self-polymerization strategy using dopamine (DA) and FA as precursors under mild conditions. The as-prepared FA-PDA FONs had an average size of 1.9 ± 0.3 nm in diameter with great aqueous dispersibility, and the FA-PDA FONs solution exhibit intense blue fluorescence under 365 nm UV lamp, and the quantum yield is ~8.27%. The FA-PDA FONs could be stable in a relatively wide pH range and high ionic strength salt solution, and the fluorescence intensities are constant. More importantly, here we developed a method for rapidly selective and sensitive detection of mercury ions (Hg2+) within 10 s using FA-PDA FONs based probe, the fluorescence intensities of FA-PDA FONs presented a great linear relationship to Hg2+ concentration, the linear range and limit of detection (LOD) were 0–18 µM and 0.18 µM, respectively. Furthermore, the feasibility of the developed Hg2+ sensor was verified by determination of Hg2+ in mineral water and tap water samples with satisfactory results. [ABSTRACT FROM AUTHOR]

A novel fluorescence probe NA-LCX was rationally designed and synthesized for the sequential recognition of Cu2+ and H2S by the combination of hydroxyl-naphthalene and diformylphenol groups. The response properties of NA-LCX for Cu2+ ions and H2S with "on-off-on" manner were investigated by fluorescence emission spectra. A highly selective and sensitive response of complex NA-LCX-Cu2+ for H2S over other competing amino acids was observed with a limit of detection at 2.79 μM. The stoichiometry of NA-LCX toward Cu2+ ions was determined to be 1 : 1 by the UV-Vis absorption spectrum, and the coordination configuration was calculated by density functional theory (DFT) calculations. Moreover, probe NA-LCX was applied successfully for the recognition of Cu2+ ions and H2S in living cells. [ABSTRACT FROM AUTHOR]

[Display omitted] • A simple naphthalimide-based chemosensor was synthesized based on ICT process for ratiometric detection of SO 2 derivatives. • The probe displayed high selective and sensitive for derivatives (detection limit is 1.53 μM). • The probe was applied for exogenous and endogenous SO 2 imaging by dual emission channels in living Hela and HepG2 cells. SO 2 is a well-known signal molecule and one of reactive sulfur species, which closely participates in many metabolic processes. While unbalanced metabolism of sulfur dioxide can lead to serious complications of various diseases. Therefore, a rapid and accurate monitoring of SO 2 derivatives with high selectivity and sensitivity would be beneficial for their bio-analytic studies. Herein, a novel ratiometric fluorescent probe (NG-TCF) based on ICT mechanism for monitoring SO 2 was developed. The probe underwent a nucleophilic addition of HSO 3 -/SO 3 2- to give rise to a 120 nm blue-shift dual-emission signal changes in enhanced green channel and subdued red channel under a single wavelength excitation. The probe showed fast response rate (within 7 min), good sensitivity (the detection limit is 1.53 µM), and specific response toward HSO 3 -/SO 3 2- over other bio-species, including H 2 S and ClO-. Moreover, the probe can be applied for visual ratio imaging of exogenous and endogenous SO 2 derivatives in living cells. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel NIR fluorescent probe for detection of NO with large Stokes shift was developed. • Probe could target in Golgi and monitor NO fluctuation upon stimulation with Glu and LPS. • Probe could in vivo imaging NO concentration in brain of depression-like mice model via tail vein injection. Depression is a debilitating mental illness that poses a serious threat to human health. Nitric Oxide (NO), as an important gasotransmitter, is closely associated with the pathogenesis of depressive disorders. Effective monitoring of NO fluctuation is beneficial for the diagnosis of depression and therapy assessment of antidepressants. Currently, there is a lack of effective methods for rapidly and sensitively identifying NO and elucidating its relationship with depression diseases. Herein, we developed a NIR dye TJ730-based fluorescent probe TJ730-Golgi-NO incorporating benzenesulfonamide as a Golgi-targeted moiety and the thiosemicarbazide group for NO detection. The probe exhibited turn-on fluorescence ability and a large Stokes shift of 158 nm, which shows high sensitivity, selectivity, and rapid response (<1 min) for NO detection. TJ730-Golgi-NO could detect exogenous and endogenous NO in cells stimulated by Glu and LPS, and target Golgi apparatus. Moreover, we disclose a significant increase of NO in the depression model and a weak fluorescence evidenced in the fluoxetine-treated depression mice. This study provides a competent tool for studying the function of NO and helping improve the effective treatment of depression diseases. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel resorufin-based fluorescent probe for selective detection of NE was developed. • Probe displayed rapid response time (<10 min) and high selectivity towards NE. • Probe could detect endogenous NE and exocytosis process by fluorescent imaging in living cells and depression-like behavior mice. Norepinephrine (NE), as an important neurotransmitter, is closely associated with the pathogenesis of anxiety and depressive disorders. Effective monitoring of NE fluctuation aids in the diagnosis of depression and the therapeutic assessment of the antidepressant intervention. The construction of novel fluorescent probes with high specificity towards NE for imaging in depression models is still in demand urgently. In this work, a novel resorufin-based red-emitting fluorescent probe for real-time tracking NE was developed. NE can significantly increase the fluorescence of probe LNE by triggering deprotection of carbonothioate ligand via nucleophilic substitution. The probe LNE demonstrated significant NE selectivity and sensitivity over other analytes in vitro. In addition, probe LNE showed a fast response time (<10 min), and the change in fluorescence signal was positively linked with NE concentration, which could be utilized to track the dysregulation of NE in vivo. More importantly, this powerful probe was successfully employed for real-time visual and imaging of NE in living cells and depression-like behavior animals. [ABSTRACT FROM AUTHOR]

• A novel probe for endogenous GSH was produced based on the coumarin derivative. • The probe exhibited high selectivity for GSH with the detection limit of 0.12 μM. • The fluorescence "turn on" of the probe is depended on de-metallization process. • The probe could be used to detect GSH in the HepG2 cells by fluorescence image. Discrimination and quantification of intracellular biothiols, such as cysteine (Cys), homocysteine (Hcy), glutathione (GSH) under physiological conditions is significant for academic research and disease diagnosis. A new fluorescent probe (complex 1 -Cu2+) for discriminate detection of GSH was prepared by copper ions coordinate with coumarin carbohydrazide Schiff base derivative 1. In suitable buffer solution (CH 3 CN: HEPES = 3:2, v/v) and under appropriate pH condition (pH = 7.2–7.4), the UV–vis spectroscopy experiments showed that compound 1 and copper ion exhibited a 1:1 ratio binding mode and moderate binding ability. Fluorescence quenching of compound 1 was observed when it complexed with Cu2+ ions. An obviously fluorescence restoration appeared after addition of GSH to the solution of probe, which also exhibited a highly selectivity relative to cysteine (Cys) and homocysteine (Hcy) in the amino acid competitive experiments. The minimum detection limit was calculated to 0.12 μM by fluorescent method, which was distinctly below the physiological concentration of GSH in live cells. Its biological application to detect the endogenous GSH was further proved by the HepG2 cell fluorescence image test. [ABSTRACT FROM AUTHOR]