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In this work, dual-emissive ratiometric fluorescent system was constructed by the introduction of an ideal internal reference. By virtue of its unique alkalinity, N2H4 could undergo a hydrazinolysis reaction with the ester group of F1, inducing remarkable fluorescence enhancement while the blue fluorescence of the internal reference DPA remained constant. Consequently, the fluorescence intensity ratios (I540/I440) were proportional to the concentrations of N2H4, which was beneficial for the exactly quantitative detection. The skillful strategy granted the sensing system advantages such as relative good solubility in aqueous media, easy-to-design, simple synthesis, large emission shift, good ratiometric response, as well as the successful application in real water samples and cell imaging. [ABSTRACT FROM AUTHOR]

Hydrogen sulfide and biothiol molecules such as Cys and GSH acted important roles in many physiological processes. To simultaneously detect and distinguish them was quite necessary by a suitable fluorescent probe. A novel chemosensor 4-(4-(benzo[d]thiazol-2-yl)-2-methoxyphenoxy)-7-nitrobenzo[c][1,2,5]oxadiazole (BMNO) was designed to detect H2S/Cys/GSH using the combination of nitrobenzofurazan (NBD) and benzothiazole fluorophores linked by a facile ether bond. The probe BMNO was developed for simultaneous identification of H2S, Cys and GSH. Noticeably, the color changes (from colorless to light purple, light orange and light yellow) of probe BMNO solutions for sensing H2S, Cys and GSH could be observed by naked eyes, respectively. The probe BMNO exhibited high selectivity and sensitivity for H2S, Cys and GSH showing distinct optical signal with detection limit as low as 0.15 μM, 0.03 μM and 0.14 μM, respectively. The sensing mechanism was clarified by spectrum analysis and some controlled experiments. In addition, these outstanding properties of probe BMNO enabled its practical applications in detection H2S in beer, and in cell imaging for Cys and GSH as well. [ABSTRACT FROM AUTHOR]

Fluorescence probes that selectively image cadmium are useful for detecting and tracking the amount of Cd2+ in cells and tissues. In this study, we designed and synthesized a novel Cd2+ fluorescence probe based on the pyridine-pyrimidine structure, 4-(methylsulfanyl)-6-(pyridin-2-yl)pyrimidin-2-amine (3), as a low-molecular-weight fluorescence probe for Cd2+. Compound 3 could successfully discriminate between Cd2+ and Zn2+ and exhibited a highly selective turn-on response toward Cd2+ over biologically related metal ions. The dissociation constant (Kd) and the limit of detection (LOD) of 5.4 × 10− 6 mol L− 1 and 4.4 × 10− 7 mol L− 1, respectively, were calculated using fluorescence titration experiments. Studies with closely related analogs showed that the bis-heterocyclic moiety of 3 acted as both a coordination site for Cd2+ and a fluorophore. Further, the methylsulfanyl group of compound 3 is essential for achieving selective and sensitive Cd2+ detection. Fluorescence microscopy studies using living cells revealed that the cell membrane permeability of compound 3 is sufficient to detect intracellular Cd2+. These results indicate that novel bis-heterocyclic molecule 3 has considerable potential as a fluorescence probe for Cd2+ in biological applications. [ABSTRACT FROM AUTHOR]

Endogenous sulfur dioxide (SO2), as a gas signal molecule, has a certain physiological functions. Understanding the role of endogenous SO2 in human physiology and pathology is of great significance to the biological characteristics of SO2,which bring challenges to develop fluorescent probes with excellent performance. Herein, we rationally designed and constructed a novel near-infrared bioprobe benzaldehyde-benzopyrylium (BBp) by employing the nucleophilic addition benzopyrylium perchlorate fluorophore and benzaldehyde moiety by means of C = C/C = O group that serves as both fluorescence reporting unit. Probe BBp exhibit excellent sensing performance with fluorescent "On − Off"rapid response (100 s) and long-wavelength emission (670 nm). With the treatment of HSO3−, the color of BBp solution obviously varies from purple to colorless, and the fluorescent color varies from red to colorless. By the fluorescence and colorimetric changes, probe BBp was capable of sensitive determination HSO3− with low limits of detection (LOD) of 0.43 μM, realizing visual quantitative monitoring SO2 derivative levels. Due to the low phototoxicity and good biocompatibility, it was successfully applied to monitor SO2 derivatives and fluorescence imaging in HepG2 and HeLa living cells. Hopefully, this work supplies a new strategy for designing NIR fluorescent probes for quantitative determination SO2 derivatives in biological samples. [ABSTRACT FROM AUTHOR]

Due to its high toxicity, long durability, easy absorption by aquatic organisms, and significant bioaccumulation, Hg2+ has caused substantial environmental damage and posed serious threats to human health. Therefore, effective detection of Hg2+ is of utmost importance. In this study, a turn-on fluorescent probe based on dicyanoisoflurone was developed for the detection of Hg2+. The probe exhibited near-infrared fluorescence signal at 660 nm upon excitation by 440 nm UV light in a mixture of CH3CN and HEPES buffer (4:1, v/v, 10 mM, pH = 7.5), with selective binding to Hg2+ in a molar ratio of 1:1. This binding event was accompanied by a visible color change from light yellow to orange. By utilizing the enhanced fluorescence signal change, this probe enables highly sensitive analysis and detection of Hg2+ with excellent selectivity (association constant = 1.63 × 104 M− 1), large Stokes shift (220 nm), high sensitivity (detection limit as low as 5.6 nM), short reaction time (30 s), and a physiological pH range of 7.5–9.5. The probe was successfully employed for detecting of Hg2+ in real water and living cells. [ABSTRACT FROM AUTHOR]

The spectroscopic properties for a number of new hydroxylated 2-stilbazoles were studied by absorption and fluorescence spectroscopy. The maximum absorption and emission wavelengths, the molar extinction coefficients, and the Stokes shift values of derivatives were given. The dependence of the spectral characteristics on pH was shown. The possibility of creating molecular logic systems and fluorescent dyes for bioimaging based on these derivatives was demonstrated. The dependence of fluorescence on the medium redox properties was established for an one of derivatives. The possibility of a fluorescent probe creating on its basis to assess the oxidative state of living systems was demonstrated. The probe has good biocompatibility and can be successfully used for fluorescence imaging in cells. [ABSTRACT FROM AUTHOR]

It is well known that sulfite (SO32−) plays an indispensable role in various physiological processes. Abnormal levels of SO32− can trigger a wide variety of diseases involving respiratory, nervous and cardiovascular systems. Hence, it is necessary to find an efficient approach for detection of SO32−. In this study, a pyrene derivative, (E)-4-(3-oxo-3-(pyren-1-yl)prop-1-en-1-yl)phenyl acrylate (PPA), was designed and synthesized for monitoring SO32−. The probe possessed simple synthetic steps, excellent anti-interference ability and specific response to SO32− in the presence of other substances. The reaction between PPA and SO32− was ascribed to Michael addition and the detection mechanism was confirmed by HRMS spectra analysis and FTIR analysis. Additionally, PPA responded linearly to detect SO32− within the rang of 0–100 μM. The limit of detection was calculated as low as 0.17 μM in accordance with the recommendation of IUPAC (CDL =3sb/m). Notably, PPA was further applied in biological imaging in HepG2 cells, which provided a possibility to monitor SO32− in vivo. [ABSTRACT FROM AUTHOR]

A new "turn-on" fluorescent probe Py based on rhodamine and piperonaldehyde was designed and synthesized for detecting Fe3+ in cells. The free probe Py was non-fluorescent. While only upon addition of Fe3+, the significant increase of the fluorescence and color were observed which could be visible directly by "naked-eye". The probe Py shows high selectivity and sensitivity for Fe3+ over other common metal ions in EtOH-H2O (3/2, v/v) mixed solution. The association constant and the detection limit were calculated to be 4.81 × 104 M−1 and 1.18 × 10−8 mol/L respectively. The introduction of piperonaldehyde unit could increase probe rigidity which could enhance its optical properties. Meanwhile, the binding mode between Py and Fe3+ was found to be a 1:1 complex formation. The density functional theory (DFT) calculations were performed which would further confirm the recognition mechanism between probe Py and Fe3+. In addition, the probe has been proved to be reversible for detecting Fe3+. Moreover, the probe Py was used to detect Fe3+ in cells successfully. [ABSTRACT FROM AUTHOR]

Due to its high toxicity, long durability, easy absorption by aquatic organisms, and significant bioaccumulation, Hg2+ has caused substantial environmental damage and posed serious threats to human health. Therefore, effective detection of Hg2+ is of utmost importance. In this study, a turn-on fluorescent probe based on dicyanoisoflurone was developed for the detection of Hg2+. The probe exhibited near-infrared fluorescence signal at 660 nm upon excitation by 440 nm UV light in a mixture of CH3CN and HEPES buffer (4:1, v/v, 10 mM, pH = 7.5), with selective binding to Hg2+ in a molar ratio of 1:1. This binding event was accompanied by a visible color change from light yellow to orange. By utilizing the enhanced fluorescence signal change, this probe enables highly sensitive analysis and detection of Hg2+ with excellent selectivity (association constant = 1.63 × 104 M− 1), large Stokes shift (220 nm), high sensitivity (detection limit as low as 5.6 nM), short reaction time (30 s), and a physiological pH range of 7.5–9.5. The probe was successfully employed for detecting of Hg2+ in real water and living cells. [ABSTRACT FROM AUTHOR]

In order to better monitor the content of Fe3+ and H2S in the biological environment, two new fluorescent probes were designed and synthesized. With the addition of Fe3+, the strong fluorescence emission of two probes was significantly quenched due to the paramagnetic effect of Fe3+. With the further addition of S2−, the fluorescence intensity was quickly restored. Two probes showed high selectivity and strong sensitivity for the detection of Fe3+ and S2−, and the fluorescence intensity "ON-OFF-ON" was accompanied with the interaction process. At the same time, two probes displayed good anti-interference ability which was not interfered by the existence of other ions. In addition, two probes illustrated fast response time to Fe3+, S2− and small cytotoxicity to cells. Therefore, two probes can provide a potential ideal tool for detecting Fe3+ and H2S in organisms and the environment. [ABSTRACT FROM AUTHOR]

H2S was deemed as a toxic gradient in the realm of food and environment but plays pivotal pathophysiological roles in organisms. H2S instabilities and disturbances are always responsible for multiple disorders. We fabricated a H2S-responsive NIR fluorescent probe (HT) for H2S detection and evaluation both in vitro and in vivo. HT exhibited rapid H2S response within 5 min, accompanied with visible color change and NIR fluorescence generation, and the fluorescent intensities were linearly correlated with corresponding H2S concentrations. When HT was incubated with A549 cells, the intracellular H2S and H2S fluctuations could be monitored ore rotundo via the responsive fluorescence. Meanwhile, when HT was co-administrated with H2S prodrug ADT-OH, the H2S release from ADT-OH could be visualized and monitored to evaluate its release efficacy. [ABSTRACT FROM AUTHOR]

The development of quick and precise detection technologies for active compounds in vivo is critical for disease prevention, diagnosis and pathological investigation. The fluorescence signal of the fluorophore usually defines the probe's sensitivity to the chemical being examined. Many natural compounds containing flavone and isoflavone scaffolds exhibit a certain amount fluorescence, albeit with poor fluorescence quantum yields. Therefore, we used density functional theory (DFT) and time-dependent density functional theory (TDDFT) calculations to investigate the fluorescence characteristics of chromium-derived fluorophores in more depth. Different substituents are introduced at different positions of the chromone. As weak electron donor groups, alkyl and aromatic groups were discovered to have varying quantum yields on the fluorophore scaffold, and longer alkyl chains are favorable to enhance fluorescence quantum yield. In comparison to the amino group, substituted amino group can avoid group rotation, and the introduction of cyclic amines such as pyrrolidine and heterocyclic amines can improve optical characteristics. The electron-donating methoxy group at position 6 helps to increase the fluorescence quantum yield. [ABSTRACT FROM AUTHOR]

Acid-responsive fluorescent compounds were prepared by introducing an ortho-hydroxyphenyl to pyrazoline with a benzothiazole backbone. These compounds demonstrated normal fluorescence photoinduced electron transfer (PET) under neutral conditions but the addition of trifluoroacetic acid showed an arctic blue fluorescence, we verified that a protonation process of nitrogen in the thiazole ring which weakened the ability of thiazole to donate electrons to the pyrazoline and changed the photoinduced electron transfer led to photoinduced electron transfer (PET), which was the mechanism of the fluorescence quenching phenomenon under strongly acidic conditions. The photophysical properties of Benzothiazole pyrazoline exhibited blue emission at 421 nm in aqueous DMSO. The blue shift in the emission was switched by acid in DMSO, showing the compound's distinct fluorescence peak at 554 nm. To investigate solvatochromism, eight different solvents were used. The red-shift emission observed in enhancing the polarity of solvents and emission in DMSO suggested the conformation of the molecule which led to the intramolecular charge transfer by color and emission changes. Furthermore, the probe was also applied using the High-performance liquid chromatography (HPLC) with a UV detector to determine the trifluoroacetic acid in water samples. Interestingly, the method was found to be linear over the range of 10.0 µg L−1 to 250.0 µg L−1 (0.999). Under the optimum condition, the separation of trifluoroacetic acid was achieved in 20 min with the LOD of 1.3 µg L−1 and LOQ of 5.1 µg L−1. This proposed method also showed satisfactory results when applied for the analysis of trifluoroacetic acid in a water sample. [ABSTRACT FROM AUTHOR]

A new spiropyran-based fluorescent probe was developed for dual detection of Fe2+ ion and pH. Addition of Fe2+ and Ag+ to the probe solution enhanced the fluorescence intensity by 6 and 5 fold, respectively. Addition of Fe3+, Hg2+ and Ni2+ caused slight increase in the fluorescence intensity of the probe. While addition of other common metal ions did not bring about substantial change of the fluorescence. Thus the probe can be used for fluorescence turn-on detection of Fe2+ ion in ethanol/water (9:1) medium. The detection limit of the probe for Fe2+ is 0.77 µM. The suitable pH range for the probe to detect Fe2+ was pH 3 − 9. Other metal ions including Li+, Na+, K+, Ag+, Cu2+, Zn2+, Co2+, Ni2+, Mn2+, Sr2+, Hg2+, Ca2+, Mg2+, Al3+, Cr3+, and Fe3+ did not cause marked interference with Fe2+ recognition. The color of the probe solution was yellow at pH 1 − 2 and colorless at other pH values. The fluorescence intensity of the probe was low at pH 1 − 12 and increased significantly when the pH was 13 and 14, indicating that the probe can be used as a colorimetric and fluorescent probe for sensing extremely acidic or extremely alkaline conditions through different channels. [ABSTRACT FROM AUTHOR]

A new pyrazoline-based probe was synthesized and the structure was determined by using X-ray diffraction analysis. The probe responds to Cu in aqueous medium in 'turn-off' fluorescent manner with selectivity and sensitivity. Furthermore, the probe could be used for real-time tracking of Cu in Hela cells. [ABSTRACT FROM AUTHOR]

Probe 1 was designed and synthesized as a new fluorescent molecular probe for thiols in PBS buffer at physiological condition. This fluorescent molecular probe consists of a thiol reaction moiety bound to a coumarin fluorophore. Its fluorescence quantum yield is low, but a drastic enhancement of fluorescence intensity was observed in the presence of thiols. Possible interference with other analytes was examined. Probe 1 displays a highly selective fluorescent enhancement with thiols, and the probe was successfully applied to thiols determination in intracellular, in human urine and blood samples. [ABSTRACT FROM AUTHOR]