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The fluorescence of functional dyes was generally quenched in aqueous solution, which hindered their application in water‐bearing detections. In this work, a novel strategy based on host‐guest interaction was provided for the purpose of fluorescence enhancement in aqueous solution and cell imaging. Three adamantane‐modified fluorescent dyes (Coum‐Ad, NP‐Ad, NR‐Ad) with coumarin, 1,8‐naphthalimide and Nile Red as fluorophores were initially designed and prepared. The ((adamantan‐1‐yl)methyl)amino group, as the auxochrome of those dyes, complexed with methylated β‐cyclodextrin (M‐β‐CD) via supramolecular interaction, and then fluorescent supramolecular nanoparticles (FSNPs) were formed by self‐assembly in water. The inclusion equilibrium constant (K) could be as high as 3.94×104 M−1. With the addition of M‐β‐CD, fluorescence quantum yields of these dyes were separately improved to 69.8 %, 32.9 % and 41.3 %. Inspired by the above satisfactory results, six adamantane‐modified probes organelle‐NPAds with organelle‐targeting capability were further obtained. As the formation of hydrogen bonds between organelle‐NPAd2 and M‐β‐CD verified by theoretical calculation, K of organelle‐NPAd2 (5.13×104 M−1~4.53×105 M−1) with M‐β‐CD was higher than that of organelle‐NPAd1 (1.15×104 M−1~3.66×104 M−1) and their fluorescence quantum yields increased to 32.8 %~83.6 % in aqueous solution. In addition, fluorescence enhancement was realized in cell imaging with the addition of M‐β‐CD. [ABSTRACT FROM AUTHOR]

Polarity and viscosity, as important microenvironment parameters, play an essential role in cell metabolism. Therefore, 9-acridine carboxaldehyde reacted with cyano compounds to obtain polarity-sensitive probes 1a–b and viscosity-sensitive probes 1c–d. Among them, with the increase in solvent polarity, the maximum emission wavelength of acridine-dicyanoisophorone-based probe 1a red-shifted from 553 nm to 594 nm, the fluorescence quantum yield increased from 0.5% to 35.6%, and the fluorescence intensity enhanced 38 fold. The acridine-cyanofuranone based probe 1b also has a polarity response similar to 1a. Nevertheless, when the solution viscosity increased from 0.89 cP (100% water) to 856 cP (1% water), the fluorescence intensity of the acridine-tricyanodihydrofuran based probe 1c at 430 nm enhanced 5.6 times. The acridine-cyanobenzothiazole based probe 1d also had a viscosity response similar to 1c. In addition, probes 1a–b were used for further HeLa cell imaging experiments due to their good photostability and the results suggested that probe 1a could locate lipid droplets and probes 1b–c could stain lysosomes. Moreover, probes 1a–b could dynamically monitor the changes in intracellular polarity. [ABSTRACT FROM AUTHOR]

[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]

In this paper, several novel nitrogen-containing heterocycle dyes 1a-c with large conjugated planar structures based on naphthyridine derivatives were designed and synthesized, which had excellent optical properties and biological applications. Optical test showed the maximum absorption wavelengths of 1a-c were in the range of 443–485 nm, while the maximum emission wavelengths located at 523–610 nm in difference solvents. Furthermore, they exhibited polarity related fluorescence intensity changes with high fluorescence quantum yields, even up to 88% (1a in THF). Moreover, the transient absorption spectra revealed the excited-state lifetime of dye 1a became shorter with the increase of solvent polarity. Density functional theory calculations are also used to help explain the effect of the polarity of solvents on their fluorescence properties. Interestingly, the dyes 1a-c were somewhat toxic to cancer cells, while had an obvious growth-promoting effect on normal cells. Additionally, 1a-c with excellent lipid droplet (LD) targeting could be used for long-term observation of targeted cellular lis) hysiological activity and further applied to dynamic monitoring of changes in LDs polarity stimulated by TLR4 activator (LPS) in living cells. Overall, the excellent optical properties and biocompatibility of 1a-c indicate that they can serve as fluorescent probes for biological applications, and the results have important implications for understanding the physiological functions of LDs, especially in terms of morphological and polar changes. [Display omitted] • The dibenzo[c,f] [2,7]naphthyridine skeleton have been first applied in the field of cell imaging. • Dyes 1a-c possess high fluorescence quantum yield and excellent polarity response. • Dyes 1a-c are somewhat toxic to cancer cells, while have a growth-promoting effect on normal cells. • Dyes 1a-c can sensitively target lipid droplets with a low concentration, and dynamically monitor their polarity changes. [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]

In this paper, oxazolepyridine and coumarin units were combined to prepare cell membrane fluorescent probe (PM-A) through aldol condensation reaction. PM-A had long wavelength emission (665–739 nm), high molar extinction coefficient (around 3.14 × 104 M−1cm−1) and large Stokes shift (150–219 nm). The photo-stability test showed that PM-A had a high relative residual absorption (93%) after 6 h of continuous illumination. In addition, the supramolecular interaction between PM-A and β-cyclodextrin was evaluated and applied to cell imaging. Probe PM-A had no fluorescence in water, but had obvious fluorescence signal in β-cyclodextrin solution. With the addition of β-cyclodextrin (0–800 eq), the fluorescence quantum yield of PM-A increased from 0% to 45%. Laser confocal experiments showed that when only PM-A was added, the probe concentration needed to be 15 μM to image the cell membrane obviously. In sharp contrast, with the help of β-cyclodextrin solution, the concentration of probe PM-A only needed 0.5 μM to quick and high specificity image cell membranes. Moreover, PM-A had high photo-bleaching resistance and long retention time after adding β-cyclodextrin. These excellent properties of PM-A were of great significance to the study of cell membrane. [Display omitted] • A near-infrared fluorescent probe (PM-A) with oxazolepyridine and coumarin units was prepared for the imaging of cell membrane at 15 μM. • The supramolecular interaction between probe PM-A and β-cyclodextrin was evaluated. • Probe PM-A showed rapid and high specificity of cell membrane imaging at the concentration of 0.5 μM with the help of β-cyclodextrin. [ABSTRACT FROM AUTHOR]

1,8-Naphthalimide is widely applied in the construction of probes because it is easy to be modified. However, 1,8-naphthalimide has been reported rarely in the application of organelle labelling especially lipid droplets (LDs). Herein, three types of amine compounds, aliphatic amine (a , b), aromatic amine (c , d) and heterocyclic amine (e , f), were chosen to construct fluorescent dyes (1a - 1f) with 4-bromo- N -butylnaphthalimide (1) by Ullmann reaction. The maximum emission wavelength ranged from 490 nm to 550 nm. What's more, 1a-1e showed high fluorescence quantum yields (0.54–0.93) in chloroform and 1e-1f had excellent photostability (>92%). In addition, the cell imaging experiment showed that they could label lipid droplets for HeLa cancer cells and L929 normal cells with extremely low toxicity. This work realizes the classical fluorophore 1,8-naphthalimide to synthesize a series of LDs markers without complex synthesis steps. Image 1 • An easy way to synthesize a series of lipid droplets markers with 1,8-naphthalimide unit. • All the 1,8-naphthalimide derivatives had high photostability and fluorescence quantum yield. • All the markers showed extremely low toxicity to cells. [ABSTRACT FROM AUTHOR]

Two probes based on tetrahydroxanthylium unit (probe 1a) and methyltetrahydroxanthylium unit (probe 1b) were designed and synthesized for the detection of hydrazine. Probes 1a–b exhibited turn-on red emission signal and high selectivity toward NH 2 NH 2. The response time of probe 1a to NH 2 NH 2 was more than 60 min, while that of probe 1b was less than 30 min. The detection limits of probes 1a–b were calculated as 210 nM and 110 nM respectively. What's more, the tolerance experiments showed that methyltetrahydroxanthylium unit possessed higher tolerance toward nucleophiles. Moreover, cells imaging experiments demonstrated that probe 1b could detect exogenous NH 2 NH 2 in living HeLa cells. Image 1 • Fluorophores based on tetrahydroxanthylium with and without methyl at the C-7 position weredesigned and synthesized for reducing the impact of nucleophiles, and they were designed as the corresponding NH 2 NH 2 probes (1a-b). • Probe 1b with red emission showed faster response time (within 30 min) and lower detection limit (110.0 nM). • Probe 1b could detect exogenous hydrazine in living HeLa cells. [ABSTRACT FROM AUTHOR]

• Cyanine dye with benzo[e]indol and aromatic azonia unites have dual organelles target abilities. • A probe was designed for the detection of NTR in mitochondria and lysosome simultaneously. • NIR emission, fast OFF-ON response (180 s) and low detection limit (3.2 ng/mL). In this article, a benzo[ e ]indol aromatic azonia skeleton cyanine dye (3) with excellent performance was developed successfully through simple modification of an original aromatic azonia skeleton cyanine dye. Dye 3 had mitochondria/lysosome-targeting ability and its maximum emission wavelength extended to the near infrared region (655 nm). Inspired by this, probe 1a was designed, which connecting 2-bromomethyl-5-nitrofuran to the cyanine dye 3 , and was the first mitochondria and lysosome dual-targeting probe for nitroreductase (NTR) detection. In addition to exhibiting good selectivity and fast response (180 s), probe 1a also exhibited high sensitivity to NTR (the detection limit was 3.2 ng/mL). The cell imaging experiments showed probe 1a could work as a dual mitochondria/lysosome-targeting probe to detect NTR in HeLa cells. [ABSTRACT FROM AUTHOR]

A small molecule fluorescent probe (probe 1) based on adenine-coumarin derivative was designed and synthesized in this paper. Probe 1 exhibited a significant fluorescence-enhancing response to nucleic acids at 495 nm (for DNA) and 487 nm (for RNA). The fluorescence enhancement of probe 1 for DNA and RNA was 5.68 and 9.73 times respectively, the fluorescence quantum yield was changed from 2.5% to 11.7% and 22.5% accordingly. Meanwhile, an excellent linear relationship of fluorescence intensity at 495 nm or 487 nm versus the nucleic acid concentration (1 μM for probe 1 , 0–350 μg/mL for DNA and 0–300 μg/mL for RNA) was obtained. Co-staining and nucleic acid digestion experiments showed that probe 1 could selectively image nucleic acids in mitochondria and nucleoli in HeLa cells. Unlabelled Image • An adenine-coumarin based probe was designed and synthesized. • Excellent light stability and high selectivity for DNA and RNA • Low cell cytotoxicity in HeLa cells • Image DNA in mitochondria of HeLa cells [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]