- Substituted 9-Diethylaminobenzo[ a]phenoxazin-5-ones (Nile Red Analogues): Synthesis and Photophysical Properties
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Nile Red is a benzo[a]phenoxazone dye containing a diethylamino substituent at the 9-position. In recent years, it has become a popular histological stain for cellular membranes and lipid droplets due to its unrivaled fluorescent properties in lipophilic environments. This makes it an attractive lead for chemical decoration to tweak its attributes and optimize it for more specialized microscopy techniques, e.g., fluorescence lifetime imaging or two-photon excited fluorescence microscopy, to which Nile Red has never been optimized. Herein, we present synthesis approaches to a series of monosubstituted Nile Red derivatives (9-diethylbenzo[a]phenoxazin-5-ones) starting from 1-naphthols or 1,3-naphthalenediols. The solvatochromic responsiveness of these fluorophores is reported with focus on how the substituents affect the absorption and emission spectra, luminosity, fluorescence lifetimes, and two-photon absorptivity. Several of the analogues emerge as strong candidates for reporting the polarity of their local environment. Specifically, the one- and two-photon excited fluorescence of Nile Red turns out to be very responsive to substitution, and the spectroscopic features can be finely tuned by judiciously introducing substituents of distinct electronic character at specific positions. This new toolkit of 9-diethylbenzo[a]phenoxazine-5-ones constitutes a step toward the next generation of optical molecular probes for advancing the understanding of lipid structures and cellular processes.
- Hornum, Mick,Mulberg, Mads W.,Szomek, Maria,Reinholdt, Peter,Brewer, Jonathan R.,Wüstner, Daniel,Kongsted, Jacob,Nielsen, Poul
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p. 1471 - 1488
(2021/01/13)
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- Nile-red-based fluorescence probe for selective detection of biothiols, computational study, and application in cell imaging
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A new colorimetric and fluorescence probe NRSH based on Nile-red chromophore for the detection of biothiols has been developed, exhibiting high selectivity towards biothiols over other interfering species. NRSH shows a blue shift in absorption peak upon reacting with biothiols, from 587 nm to 567 nm, which induces an obvious color change from blue to pink and exhibits a 35-fold fluorescence enhancement at 645 nm in red emission range. NRSH displays rapid (2S, which is faster than other biothiols (>5 min). The detection limits of probe NRSH towards biothiols are very low (22.05 nM for H2S, 34.04 nM for Cys, 107.28 nM for GSH and 113.65 nM for Hcy). Furthermore, NRSH is low cytotoxic and can be successfully applied as a bioimaging tool for real-time monitoring biothiols in HeLa cells. In addition, fluorescence mechanism of probe NRSH is further understood by theoretical calculations.
- Meng, Zhi-Zhong,Rong, Xiang,Xu, Zhong-Yong,Yan, Jin-Wu,Zhang, Lei,Zhu, Bin
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- Structural modifications of nile red carbon monoxide fluorescent probe: Sensing mechanism and applications
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Carbon monoxide (CO) is a cell-signaling molecule (gasotransmitter) produced endogenously by oxidative catabolism of heme, and the understanding of its spatial and temporal sensing at the cellular level is still an open challenge. Synthesis, optical properties, and study of the sensing mechanism of Nile red Pd-based CO chemosensors, structurally modified by core and bridge substituents, in methanol and aqueous solutions are reported in this work. The sensing fluorescence "off-on" response of palladacycle-based sensors possessing low-background fluorescence arises from their reaction with CO to release the corresponding highly fluorescent Nile red derivatives in the final step. Our mechanistic study showed that electron-withdrawing and electron-donating core substituents affect the rate-determining step of the reaction. More importantly, the substituents were found to have a substantial effect on the Nile red sensor fluorescence quantum yields, hereby defining the sensing detection limit. The highest overall fluorescence and sensing rate enhancements were found for a 2-hydroxy palladacycle derivative, which was used in subsequent biological studies on mouse hepatoma cells as it easily crosses the cell membrane and qualitatively traces the localization of CO within the intracellular compartment with the linear quantitative response to increasing CO concentrations.
- Klán, Petr,Madea, Dominik,Martínek, Marek,Muchová, Lucie,Váňa, Ji?í,Vítek, Libor
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p. 3473 - 3489
(2020/03/25)
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- Single-Atom Fluorescence Switch: A General Approach toward Visible-Light-Activated Dyes for Biological Imaging
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Photoactivatable fluorophores afford powerful molecular tools to improve the spatial and temporal resolution of subcellular structures and dynamics. By performing a single sulfur-for-oxygen atom replacement within common fluorophores, we have developed a facile and general strategy to obtain photoactivatable fluorogenic dyes across a broad spectral range. Thiocarbonyl substitution within fluorophores results in significant loss of fluorescence via a photoinduced electron transfer-quenching mechanism as suggested by theoretical calculations. Significantly, upon exposure to air and visible light residing in their absorption regime (365-630 nm), thio-caged fluorophores can be efficiently desulfurized to their oxo derivatives, thus restoring strong emission of the fluorophores. The effective photoactivation makes thio-caged fluorophores promising candidates for super-resolution imaging, which was realized by photoactivated localization microscopy (PALM) with low-power activation light under physiological conditions in the absence of cytotoxic additives (e.g., thiols, oxygen scavengers), a feature superior to traditional PALM probes. The versatility of this thio-caging strategy was further demonstrated by multicolor super-resolution imaging of lipid droplets and proteins of interest.
- Tang, Juan,Robichaux, Michael A.,Wu, Kuan-Lin,Pei, Jingqi,Nguyen, Nhung T.,Zhou, Yubin,Wensel, Theodore G.,Xiao, Han
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supporting information
p. 14699 - 14706
(2019/10/11)
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- Artificial photosynthesis of methanol from carbon dioxide and water via a Nile red-embedded TiO2 photocathode
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The conversion of carbon dioxide into useful chemicals is a prospective strategy for alleviating the greenhouse effect and the depletion of energy. Herein, we report an artificial photosynthetic system composed of a photoanode and a photocathode comprised of NRx@TiO2 functionalized with Nile red via covalent linkage or Pd/NRx@TiO2 with additional palladium nanoparticles. The new Nile red derivatives and organic-inorganic composite electrodes were steadily prepared and well characterized using NMR, HRMS, UV-vis, FTIR, TEM, XPS, XRD and SEM. Methanol and oxygen were the products that could be detected in the liquid and gas phase. The main active species in this artificial photosynthesis system were proven using EPR spectroscopy to be hydroxy radicals releasing O2 gas via H2O2. Moreover, the carbon source of methanol was validated using a 13CO2 labeling experiment; 18O2 was determined to come from H2O using GC-MS. The optimal photoelectrocatalytic CO2 reduction was carried out using Pd/NR2@TiO2 as the working electrode yielding methanol at a rate of 106 μM h?1 cm?2 with high light quantum efficiency (Φcell = 0.95).
- Jia, Yongjian,Xu, Yanjie,Nie, Rong,Chen, Fengjuan,Zhu, Zhenping,Wang, Jianguo,Jing, Huanwang
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supporting information
p. 5495 - 5501
(2017/03/22)
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- Rational Design of a Robust Fluorescent Probe for the Detection of Endogenous Carbon Monoxide in Living Zebrafish Embryos and Mouse Tissue
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Carbon monoxide (CO) is one of the most important gaseous signal molecules in biological systems. However, the investigation of the functions of CO in living organisms is restricted by the lack of functional molecular tools. To address this critical challenge, we present herein the rational design, synthesis, and in vivo imaging studies of a powerful two-photon excited near-infrared fluorescent probe (1-Ac) for endogenous CO monitoring. The advantageous features of the new probe include high stability, low background fluorescence, large fluorescence enhancement, high sensitivity, and two-photon excitation with emission in the near-infrared region. Significantly, these merits of the probe enable the tracking of endogenous CO in zebrafish embryos and mouse tissues for the first time.
- Liu, Keyin,Kong, Xiuqi,Ma, Yanyan,Lin, Weiying
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supporting information
p. 13489 - 13492
(2017/10/17)
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- Photoconductive Nile red cyclopalladated metallomesogens
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The synthesis and the electrochemical, photophysical and photoconductive properties of two new cyclometallated metallomesogens are described. These two complexes were respectively obtained by covalent metallation of Nile red, or a polyalkylated Nile red derivative, to a palladium(ii) ion and by using a polyalkylated Schiff base as an ancillary ligand to complete the coordination sphere of the metal centre. The introduction of long alkyl chains on either one or both ligands leads to disk-shaped metallomesogens with ordered room temperature columnar organisation induced, in both cases, by the formation of dimeric pairs. As shown by powder X-Ray diffraction studies, both complexes exhibit a columnar rectangular mesophase over a wide temperature range. These complexes show a redox solution behaviour characterised by one reversible single-electron reduction and two consecutive reversible oxidation waves, which give them an electrochemical amphoteric character. Energy levels and distributions of frontier orbitals have been estimated. Photoconductivity of the mesophase at room temperature has been observed from UV-Vis to near IR wavelength. The high thermal, electrochemical and mesophase stabilities of the studied Nile red complexes confirm that cyclometallated Pd(ii) complexes form a new class of photoconductors with features suitable for molecular semiconductor applications. The Royal Society of Chemistry 2012.
- Ionescu, Andreea,Godbert, Nicolas,Crispini, Alessandra,Termine, Roberto,Golemme, Attilio,Ghedini, Mauro
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p. 23617 - 23626
(2013/02/25)
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- Near-infrared solid-state fluorescent naphthooxazine dyes attached with bulky dibutylamino and perfluoroalkenyloxy groups at 6- and 9-positions
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No solid-state fluorescence is observed for 9-(diethylamino)benzo[a]phenoxazin-5-one (Nile Red). However, 9-dibutylamino-6-{perfluoro[4-methyl-3-(1-methylethyl)-2-penten]-2-oxy}benzo[a]phenoxazin-5-one showed fluorescence maximum at 717 nm in solid state
- Park, So-Yeon,Kubota, Yasuhiro,Funabiki, Kazumasa,Shiro, Motoo,Matsui, Masaki
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supporting information; experimental part
p. 1131 - 1135
(2009/05/11)
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