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[Display omitted] • Probes 1a-b for detection of thiophenols by ESIPT mechanism were constructed with diethylcoumarin–salicylaldehyde units. • They showed large Stokes shift (greater than100 nm) and one of them displayed NIR-emitting (670 nm) when detecting thiophenols. • Probes 1a-b could form inclusion complexes with M-β-CD. • The presence of M-β-CD reduced the detection limits of probes 1a - b towards thiophenols. Thiophenol and its derivatives are compounds with high toxicity to organisms and environmental pollution, so it is necessary to detect the level of thiophenols in the environment and biological samples. The probes 1a-b were obtained by introducing the 2,4-dinitrophenyl ether group into diethylcoumarin–salicylaldehyde based compounds. And they can form host-guest compounds with methylated β-cyclodextrin (M-β-CD), the association constants of inclusion complexes are 49.2 M−1, 125 M−1 respectively. The fluorescence intensities of probes 1a-b at 600 nm (1a) and 670 nm (1b) increased significantly in thiophenols detection. Meanwhile, with the addition of M-β-CD, the hydrophobic cavity of M-β-CD significantly increased the fluorescence intensity of probes 1a-b , thus the detection limits of probes 1a-b to thiophenols were reduced from 410 nM, 365 nM to 62 nM, 33 nM respectively. Whereas, the good selectivity and short response time of probes 1a-b towards thiophenols was not affected in the presence of M-β-CD. Moreover, probes 1a-b were used for further water sample detection and HeLa cell imaging experiments due to their good response to thiophenols and the results suggested that probes 1a-b had the potential to detect the content of thiophenols in water samples and living cells. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Five probes (1a-e) have excellent photo stability. • Four probes (1a-d) exhibit "OFF–ON" fluorescent responses towards nucleic acids. • Probe 1a can image mitochondrial nucleic acid. • Probe 1a was a low-toxic probe for live HeLa cells. Abstract Five cyanine dyes (1a-e) with azonia unit have been prepared by the reaction of pyrido[1,2−a]pyrimidinium ions and suitable aldehydes. Before further research, their photo and thermal stabilities were determined in the first place. At least 88% absorption remained after 5 h irradiating illustrated all of these dyes had excellent photo stability. Meanwhile, the decomposition temperature of dyes was around 200 °C which demonstrated they had good thermal stability. Therefore, the good photo and thermal stability made them possible to be probes. Subsequently, the optical properties of probes toward nucleic acids had been measured. TheirOFF–ON fluorescent responses (1a - d) towards nucleic acids were investigated. In addition, confocal microscopy imaging of probe 1a in live HeLa cells indicated that probe 1a could image mitochondrial nucleic acid. [ABSTRACT FROM AUTHOR]

To evaluate the lysosome targetability of different nitrogen-containing basicity groups, seven fluorescent probes based on phenoxazinium connected different nitrogen-containing basicity groups were prepared. Probe 8b containing N , N -dimethylphenyl, 8c containing N , N -diethylphenyl group and 8d containing quinolin-8-yl group exhibited obvious emission responses at 675 nm with pH ranging from 2.4 to 5.6, 3.4–7.6 and 1.8–4.2, and their calculated p K a were 3.99, 5.57 and 2.46 respectively. While probe 8a containing morphoyl group, probe 8e containing pyridine-4-yl, probe 8f containing pyridine-3-yl and probe 8g containing pyrimidine group showed no significant changes of emission intensity when pH changes from 2.0 to 8.0. Moreover, three probes 8b , 8c and 8d showed good selectivity for hydrogen ion. Fluorescent imaging experiments indicated that probes 8c and 8d were lysosome biomarkers for Ges-1 and HeLa cells. [ABSTRACT FROM AUTHOR]

A near-infrared fluorescent probe based on benzo[a]phenoxazine containing o -phenylenediamine group as reactive site was designed and synthesized. The titration experiment showed that the probe gave colorimetric response towards sodium nitrite with the absorption maxima at 630 nm and 542 nm in pH = 5.0 disodium hydrogen phosphate-citric acid buffers containing 30% DMSO; its emission was located in 590–820 nm with the 9.1-fold fluorescent enhancement under excitation at 580 nm. Moreover, the probe can detect nitrite quantitatively in a concentration range of 0.0–26.0 μM and the detection limit is as low as 45 nM. The salient features of this method are high sensitivity and selectivity, fast detection and low detection limit. Fluorescence confocal imaging experiments with V79 and HeLa cells indicate that the probe has the potential application in quantitative detection exogenous nitrite level for in cellular imaging. [ABSTRACT FROM AUTHOR]

[Display omitted] Five cyanine dyes (6a-e) with aza units were prepared by the reaction of pyridinum or quinolinium with suitable aldehydes. They present several remarkable features including large Stokes shift (235–282 nm), long emission wavelength (640–698 nm) and excellent selectivity. Moreover, probes 6a-b display obvious and sensitive fluorescent response to DNA and RNA in aqueous solution, and the quantum yield of probe 6a response to RNA increases from 0 to 8.9%. More importantly, probes 6c and 6e can effectively avoid DNA interference and only respond to RNA in aqueous solution. In addition, laser confocal cell experiment has showed that probe 6b can image the nucleolus of nucleic acids in HeLa cells. [ABSTRACT FROM AUTHOR]

• Probe 1 based on benzo[ e ]indole and aromatic azonia exhibited near infrared emission and high sensitivity for viscosity. • A good linear relationship between lg (I 650nm) and lg η (viscosity values from 0.89 cP to 8.6 cP). • Probe 1 with the low concentration (500 nM) could simultaneously detect changes of viscosity in mitochondria and lysosomes. • Probe 1 could be used to distinguish between cancer cells and normal cells. • Probe 1 could detect the mitochondrial and lysosomal viscosity fluctuation during autophagy. This article reported a hemicyanine dye fluorescent probe (1), based on benzo[ e ]indole and aromatic azonia skeleton, for simultaneous detection of viscosity fluctuation in mitochondria and lysosomes. Probe 1 exhibited near infrared emission and high sensitivity towards viscosity of the medium. As the viscosity increases, the rotation of C C single bond between the benzo[ e ]indole and the nitrogen heterocycle could be suppressed, and the entire molecular scaffold was coplanar and emitted strong fluorescence due to more delocalized electron distribution. The fluorescence intensity of probe 1 was enhanced 16.2 times at 650 nm as the viscosity increased from 0.89 cP to 865 cP. Correspondingly, the fluorescence quantum yield of probe 1 increased from 4.2% to 49.6%. The change of lg (I 650nm) had a good linear relationship with lg η (viscosity values: 0.89 cP to 8.6 cP), which meant the viscosity of dilute solution could be detected quantitatively. In cell experiments, probe 1 with low concentration (500 nM) had stronger fluorescence intensity in cancer cells than in normal cells. Besides, probe 1 could monitor the viscosity changes of mitochondria and lysosomes caused by the addition of ionophores (monensin, nystatin and dexamethasone) or in the process of autophagy. The results provide a simple and effective method for the early diagnosis of related diseases. [ABSTRACT FROM AUTHOR]

In this study, a mitochondria-specific fluorescent probe for efficient ratiometric detection of Cys was designed and investigated. Probe 1 is composed of a xanthylene skeleton and a benzyl group containing an acryloyl moiety. The probe showed excellent water solubility, good selectivity and sensitivity toward Cys over other analytes, and afforded an extremely low detection limit of 33.7 nM. The possible detection mechanism was ascertained by HRMS analysis. Moreover, probe 1 had excellent mitochondrial-targeting ability (the Pearson's correlation coefficient was 0.96), and was capable of monitoring endogenous Cys in living HeLa cells by dual channel ratiometric bioimaging, demonstrating its significant potential in biological applications. Image 1 • A novel ratiometric and mitochondria-targetability fluorescent probe 1 with a xanthylene skeleton for Cys was developed. • Probe 1 showed excellent water solubility, high selectivity and sensitivity (detection limit of 33.7 nM) towards Cys. • Probe 1 could be successfully used for imaging cellular exogenous and endogenous Cys. [ABSTRACT FROM AUTHOR]

Three 5 H -benzo[a]phenoxazin-5-one-based (benzoresorufin and nile-red) Cysteine (Cys) detection probes have been comparatively designed and synthesized in this paper. The optical experiments exhibit probe 1b with a crotonoyl group has no response toward Cys; while probes 1a and 1c have the same reaction site (acryloyl group), their optical responses to Cys are quite different. The benzoresorufin-based-probe 1a shows a turn-on fluorescence response (118-fold) to Cys at 631 nm and affords a very low detection limit (DL = 19.8 nM). Compared with probe 1a , the nile-red-based probe 1c displays gradually diminishing fluorescence intensity with increased Cys concentration at 665 nm. And the notable different fluorescence response mechanisms of probes 1a and 1c toward Cys can be interpreted by HRMS and time-dependent density functional theorety (TDDFT) calculations. Furthermore, both of the two probes indicate high sensitivity and selectivity toward Cys over other similar structured amino acids including homocysteine (Hcy) and glutathione (GSH). Further cellular applications of the two probes have been successfully performed in HeLa cells. Image 1 • Three Cys probes 1a − c based on benzoxazine (benzoresorufin and nile-red) were comparatively designed, synthesized and investigated, and the mechanism was proposed. • Their different responses to Cys could indicate that the same fluorophore with different auxochrome groups and detection groups have different properties. • Probes 1a and 1c exhibited high selectivity for Cys, and 1a had a low detection limit of 19.8 nM. • Off-on and attenuation response; long emission wavelength; cell imaging. [ABSTRACT FROM AUTHOR]