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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]

Dual‐state emission luminogens (DSEgens) are receiving research interest in the construction of multifunctional materials due to their inherent advantage of high emission efficiency in both the molecularly dispersed solution state and the solid state. However, it remains challenging in synthesizing DSEgens via a delicate manipulation of the molecular structures. This work presents an example of bright DSEgen synthesis by tuning the molecular electronic structures and conformations. Three coumarin‐tetraphenylethylene (TPE) molecules with a donor‐acceptor electronic structure and highly twisting conformations have been synthesized. While compound resulting from direct conjugation of coumarin with a TPE unit shows aggregation‐induced emission, compound with an N,N‐diaminoethyl modification on the 7‐position of coumarin and compound with a further phenyl linker between coumarin and TPE units feature strong dual‐state emission. Benefiting from their strong solid emission and twisting conformations, these fluorophores display reversible mechanofluorochromism. Finally, applications for rewritable information storage in the solid state and live‐cell imaging in the solution state were demonstrated. [ABSTRACT FROM AUTHOR]

Two green fluorescent tetrazine‐modified cyanine‐styryl dyes were synthesized for bioorthogonal labelling of DNA by means of the Diels‐Alder reaction with inverse electron demand. With DNA as target biopolymer the fluorescence of these dyes is released by two factors: (i) sterically by their interaction with DNA, and (ii) structurally via the conjugated tetrazine as quencher moiety. As a result, the reaction with bicyclononyne‐modified DNA is significantly accelerated up to ≥284,000 M−1 s−1, and the fluorescence turn‐on is enhanced up to 560 by the two‐factor fluorogenicity. These dyes are cell permeable even in low concentrations and undergo fluorogenic reactions with BCN‐modified DNA in living HeLa cells. The two‐factor fluorescence release improves the signal‐to‐noise ratio such that washing procedures prior to cell imaging are not needed, which is a great advantage for live cell imaging of DNA and RNA in the future. [ABSTRACT FROM AUTHOR]

Selective detection of H2S in the cellular systems using fluorescent CPs/MOFs is of great scientific interest due to their outstanding aqueous stability, biocompatibility and real‐time detection ability. Fabrication of such materials using complete biologically essential elements and applying them as an efficient biosensor is still quite challenging. In this context, two newly synthesized CPs containing biologically essential metal ion (Zn) and nitro/azido functional groups into the framework to sense extracellular and intracellular H2S by reducing into respective amines are presented. The CP‐1 containing the azide group acted as an efficient fluorescent turn‐on probe with the lowest detection limit (7.2 μM) and shortest response time (30 s) among the Zn‐based probes reported till date. Moreover, CP‐1 exhibited green luminescence in live cells after imaging a very low concentration of H2S, whereas the nitro analogue CP‐2 could not detect the target analyte due to its framework disruption. [ABSTRACT FROM AUTHOR]

The current review describes advances in the use of fluorescent 2,1,3‐benzothiadiazole (BTD) derivatives after nearly one decade since the first description of bioimaging experiments using this class of fluorogenic dyes. The review describes the use of BTD‐containing fluorophores applied as, inter alia, bioprobes for imaging cell nuclei, mitochondria, lipid droplets, sensors, markers for proteins and related events, biological processes and activities, lysosomes, plasma membranes, multicellular models, and animals. A number of physicochemical and photophysical properties commonly observed for BTD fluorogenic structures are also described. [ABSTRACT FROM AUTHOR]

Live‐cell imaging with fluorescent probes is an essential tool in chemical biology to visualize the dynamics of biological processes in real‐time. Intracellular disease biomarker imaging remains a formidable challenge due to the intrinsic limitations of conventional fluorescent probes and the complex nature of cells. This work reports the in cellulo assembly of a fluorescent probe to image cyclooxygenase‐2 (COX‐2). We developed celecoxib‐azide derivative 14, possessing favorable biophysical properties and excellent COX‐2 selectivity profile. In cellulo strain‐promoted fluorogenic click chemistry of COX‐2‐engaged compound 14 with non/weakly‐fluorescent compounds 11 and 17 formed fluorescent probes 15 and 18 for the detection of COX‐2 in living cells. Competitive binding studies, biophysical, and comprehensive computational analyses were used to describe protein‐ligand interactions. The reported new chemical toolbox enables precise visualization and tracking of COX‐2 in live cells with superior sensitivity in the visible range. [ABSTRACT FROM AUTHOR]

Fluorescent stapled peptides are important chemical tools for detecting intracellular distribution, protein–protein interactions, and localization of target proteins. These peptides are usually labeled with bulky sized fluorophores through reactive functional groups, which may alter the physical properties and biological activities of peptides. Herein, a unique strategy is developed for synthesizing new stapled peptides with built‐in fluorescence. The stapled peptides were prepared through Rh‐catalyzed C(sp2)−H olefination in tryptophan (Trp) residues by using pyridine/pyrimidine as the directing groups under mild conditions. This method displays good regioselectivity and high efficiency. Furthermore, as a proof of concept for its biological applications, stapled peptides without additional fluorophore 9 a and 9 b were constructed for a cell imaging study. These peptides displayed strong binding affinity toward integrin αvβ3 in A549 cells by cell imaging experiments. Notably they demonstrated even better anticancer activity than commercial antagonist cyclic (RGDfK). The method will provide robust tools for the peptide macrocyclization field. [ABSTRACT FROM AUTHOR]

Two red‐emitting dicyanomethylene‐4H‐pyran (DM) based fluorescent probes were designed and used for peroxynitrite (ONOO−) detection. Nevertheless, the aggregation‐caused quenching effect diminished the fluorescence and restricted their further applications. To overcome this problem, tetraphenylethylene (TPE) based glycoclusters were used to self‐assemble with these DM probes to obtain supramolecular water‐soluble glyco‐dots. This self‐assembly strategy enhanced the fluorescence intensity, leading to an enhanced selectivity and activity of the resulting glyco‐dot comparing to DM probes alone in PBS buffer. The glyco‐dots also exhibited better results during fluorescence sensing of intracellular ONOO− than the probes alone, thereby offering scope for the development of other similar supramolecular glyco‐systems for chemical biological studies. [ABSTRACT FROM AUTHOR]

Two‐photon excited fluorescent (TPEF) materials are highly desirable for bioimaging applications owing to their unique characteristics of deep‐tissue penetration and high spatiotemporal resolution. Herein, by connecting one, two, or three electron‐deficient zinc porphyrin units to an electron‐rich triazatruxene core via ethynyl π‐bridges, conjugated multipolar molecules TAT‐(ZnP)n (n=1–3) were developed as TPEF materials for cell imaging. The three new dyes present high fluorescence quantum yields (0.40–0.47) and rationally improved two‐photon absorption (TPA) properties. In particular, the peak TPA cross section of TAT‐ZnP (436 GM) is significantly larger than that of the ZnP reference (59 GM). The δTPA values of TAT‐(ZnP)2 and TAT‐(ZnP)3 further increase to 1031 and up to 1496 GM, respectively, indicating the effect of incorporated ZnP units on the TPA properties. The substantial improvement of the TPEF properties is attributed to the formation of π‐conjugated quadrapole/octupole molecules and the extension of D‐π‐A‐D systems, which has been rationalized by density function theory (DFT) calculations. Moreover, all of the three new dyes display good biocompatibility and preferential targeting ability toward cytomembrane, thus can be superior candidates for TPEF imaging of living cells. Overall, this work demonstrated a promising strategy for the development of porphyrin‐based TPEF materials by the construction and extension of D‐π‐A‐D multipolar array. [ABSTRACT FROM AUTHOR]

Photostable and near‐infrared (NIR)‐emitting organic fluorophores with large Stokes shifts are in great demand for long‐term bioimaging at deeper depths with minimal autofluorescence and self‐quenching. Herein, a new class of benzorhodamines and their analogues that are photostable and emit in the NIR region (up to 785 nm) with large Stokes shifts (>120 nm) is reported. The synthesis involves condensation of 7‐alkylamino‐2‐naphthols with 2‐[4‐(dimethylamino)‐2‐hydroxybenzoyl]benzoic acid, which leads to bent‐shaped benzorhodamines that emit orange fluorescence (≈600 nm); however, introduction of steric hindrance near the condensation site switched the regioselectivity, to provide a linear benzorhodamine system for the first time. The linear benzorhodamine derivatives provide bright fluorescence images in cells and in tissue. A carboxy‐benzorhodamine was applied for photothermal therapy of cancer cells and xenograft cancer mice. [ABSTRACT FROM AUTHOR]

Fluorescent probes that light‐up upon reaction with complementary bioorthogonal reagents are superior tools for no‐wash fluorogenic bioimaging applications. In this work, a thorough study is presented on a set of seventeen structurally diverse coumarin–tetrazine probes that produce fluorescent dyes with exceptional turn‐on ratios when reacted with trans‐cyclooctene (TCO) and bicyclononyne (BCN) dienophiles. In general, formation of the fully aromatic pyridazine‐containing dyes resulting from the reaction with BCN was found superior in terms of fluorogenicity. However, evaluation of the probes in cellular imaging experiments revealed that other factors, such as reaction kinetics and good cell permeability, prevail over the fluorescence turn‐on properties. The best compound identified in this study showed excellent performance in live cell‐labeling experiments and enabled no‐wash fluorogenic imaging on a timescale of seconds. [ABSTRACT FROM AUTHOR]

New L‐shaped fluorophores possessing five conjugated rings have been synthesized through a four‐step procedure involving diketopyrrolopyrrole synthesis and its double N‐alkylation, followed by trimethylsilyl bromide‐mediated rearrangement to thieno[2,3‐f]isoindole‐5,8‐dione and an intramolecular Friedel–Crafts reaction. In comparison with the parent isoindolediones and π‐expanded diketopyrrolopyrroles, these new dyes show red‐shifted absorption and emission (up to ≈630 nm). Their structural rigidity is responsible for both the observed small Stokes shifts and large fluorescence quantum yields. Tissue imaging studies revealed that these new dyes show advantageous features including minimal autofluorescence interference and pronounced solvent‐sensitive emission. Interestingly, there is a fundamental difference between a dye possessing an amino group and its analog bearing an N‐alkyl substituent. The former dye under two‐photon excitation at 900 nm gives bright images whereas its N‐alkylated counterpart does not. A new type of membrane localization has been discovered by an N‐alkylated isoindoledione possessing a benzofuryl substituent. In spite of the fact that the fluorescence quantum yield of this dye in a range of solvents is rather low, it does stain cell membranes exclusively. This new mode of cellular staining opens the door towards further development of membrane staining dyes. [ABSTRACT FROM AUTHOR]

Two different chromophores, namely a dipolar and an octupolar system, were prepared and their linear and nonlinear optical properties as well as their bioimaging capabilities were compared. Both contain triphenylamine as the donor and a triarylborane as the acceptor, the latter modified with cationic trimethylammonio groups to provide solubility in aqueous media. The octupolar system exhibits a much higher two‐photon brightness, and also better cell viability and enhanced selectivity for lysosomes compared with the dipolar chromophore. Furthermore, both dyes were applied in two‐photon excited fluorescence (TPEF) live‐cell imaging. [ABSTRACT FROM AUTHOR]

In this communication, the synthesis of three unknown polyfluorinated cyanine dyes and their application as selective markers for mitochondria are presented. By incorporating fluorous side chains into cyanine dyes, their remarkable photophysical properties were enhanced. To investigate their biological application, several different cell lines were incubated with the synthesized cyanine dyes. It was discovered that the presented dyes can be utilized for selective near‐infrared‐light (NIR) staining of mitochondria, with very low cytotoxicity determined by MTT assay. This is the first time that polyfluorinated cyanine fluorophores are presented as selective markers for mitochondria. Due to the versatile applications of polyfluorinated fluorophores in bioimaging and materials science, it is expected that the presented fluorophores will be stimulating for the scientific community. [ABSTRACT FROM AUTHOR]

A new scaffold for producing efficient organic fluorescent materials was identified: 2,5‐diamino‐4,6‐diarylpyrimidine featuring a C4N4 elemental composition. Single‐step installation of two aryl groups at the 4,6‐positions of the pyrimidine core delivered fluorescent organic materials in a modular fashion. A range of fluorescent compounds with distinct absorption/emission properties was readily accessed by changing the aromatic attachments. A generally high absorption coefficient and quantum yield were observed, including C4N4 derivatives that could fluoresce even in the solid state. The two amino groups at the 2,5‐positions of the pyrimidine were essential for intense fluorescence with a large Stokes shift, which was corroborated by structural relaxation to a p‐iminoquinone‐like structure in the excited state. Besides live‐cell imaging capabilities, fluorescent labeling of a protein involved in autophagy elucidated a new protein–protein interaction, supporting potential utility in bioimaging applications. A new scaffold for producing efficient organic fluorescent materials was identified: 2,5‐diamino‐4,6‐pyrimidine featuring a C4N4 elemental composition (see figure). Single‐step installation of two aryl groups at the 4,6‐positions of the pyrimidine core delivered fluorescent organic materials in a modular fashion. [ABSTRACT FROM AUTHOR]

Abstract: The low toxicity, high surface area, and ease of functionalisation of carbon nanohorns (CNH) makes them attractive systems for cellular imaging, diagnostics and therapeutics. However, challenges remain for the biomedical translation of these and other nanomaterials. A significant task is tuning the surface chemistry to achieve optimal cellular interactions. Herein, we combine real‐time fluorescent imaging of nanoparticle cellular uptake and real‐time differential interference contrast (DIC) imaging of extracellular media to monitor a) nanoparticle/nanoparticle and b) nanoparticle/cell interactions for CNHs covalently modified with an OFF/ON near‐IR dye, the fluorescence of which is switched OFF in extracellular environments and triggered upon cellular internalisation. CHN samples modified with different loadings of the hydrophobic dye are taken as a simple model of drug‐loaded nanoparticle systems. The punctate fluorescence suggests the CNHs are delivered to lysosomes and other vesicles of the endocytic pathway. DIC imaging highlights the competition that exists for many particle types, between extracellular aggregation and cellular internalization, the efficiency of which would be dependent upon the amount of fluorophore loading. The results of this study illustrate how complementary real‐time imaging methods together with physicochemical characterisation can be used to address the challenges involved in optimising nanoparticle/cell interactions for biomedical applications. [ABSTRACT FROM AUTHOR]

Abstract: Diketopyrrolopyrroles (DPPs) have recently attracted much interest as very bright and photostable red‐emitting molecules. However, their tendency to form nonfluorescent aggregates in water through the aggregation‐caused quenching (ACQ) effect is a major issue that limits their application under the microscope. Herein, two DPP molecules have been incorporated into the membrane of highly stable and water‐soluble quatsomes (QS; nanovesicles composed of surfactants and sterols), which allow their nanostructuration in water and, at the same time, limits the ACQ effect. The obtained fluorescent organic nanoparticles showed superior structural homogeneity, along with long‐term colloidal and optical stability. A thorough one‐ (1P) and two‐photon (2P) fluorescence characterization revealed the promising photophysical features of these fluorescent nanovesicles, which showed a high 1P and 2P brightness. Finally, the fluorescent QSs were used for the in vitro bioimaging of Saos‐2 osteosarcoma cell lines; this demonstrates their potential as nanomaterials for bioimaging applications. [ABSTRACT FROM AUTHOR]

A simple and mild light-triggered fluorescent labeling approach, based on the photolysis and reactive carbene insertion of diazirine, to rapidly generate fluorescent nanoparticles is reported. Proof of concept studies demonstrated that the non-fluorescent SiNPs could be covalently labeled by diazirine-conjugated fluorescein (dFITC) upon photo irradiation ( λ=365 nm) to afford fluorescent SiNPs with good fluorescent stability and low cytotoxicity. In vitro cellular imaging results indicated that the internalization of SiNPs into living cells could be readily visualized based on fluorescein-labeled SiNPs (F-SiNPs) in real time. We believe that the light-triggered labeling approach may offer a valuable method for surface modification of nanomaterials to achieve new functions. [ABSTRACT FROM AUTHOR]

A highly water-soluble, fluorescence turn-on sensor for Ca2+ is reported. The sensor affords high selectivity in sensing Ca2+ over other biologically important metal cations. The dissociation constant of the sensor in binding Ca2+ is 0.92 m m. Fluorescence microscopy experiments demonstrate that the sensor is cell-impermeable and capable of detecting extracellular Ca2+. [ABSTRACT FROM AUTHOR]

Herein we describe a photosensitizer (PS) with the capacity to perform multiple logic operations based on a pyrene-containing phthalocyanine (Pc) derivative. The system presents three output signals (fluorescence at 377 and 683 nm, and singlet oxygen (¹O2) production), which are dependent on three inputs: two chemical (concentration of dithiothreitol (DTT) and acidic pH) and one physical (visible light above 530 nm for ¹O2 sensitization). The multi-input/multioutput nature of this PS leads to single-, double-, and triple-mode activation pathways of its fluorescent and photodynamic functions, through the interplay of various interrelated AND, ID, and INHIBIT gates. Dual fluorescence emissions are potentially useful for orthogonal optical imaging protocols while ¹O2 is the main reactive species in photodynamic therapy (PDT). We thus expect that this kind of PS logic system will be of great interest for multimodal cellular imaging and therapeutic applications. [ABSTRACT FROM AUTHOR]

Pyrene-based turn-on ratiometric fluorescent probe 1 demonstrates high sensitivity and exceptional selectivity toward Cr3+ in the presence of other metals, including Fe3+ in aqueous media. Interaction of Cr3+ with probe 1 brings pyrene moieties close enough to have better aligned π-π stacking, thus enhancing the excimer peak many fold. On the other hand, the interaction of Fe3+ with probe 1 brings forth a negligible difference in stacking, resulting in an insignificant change in fluorescence intensity. Exceptional selectivity of probe 1 with Cr3+ over Fe3+ and other metals has been confirmed by theoretical studies in addition to experimental results. Imaging of HeLa cells observed by confocal fluorescence microscopy reveals that probe 1 can be used to monitor Cr3+ in live cells to map its subcellular distribution. [ABSTRACT FROM AUTHOR]

Improved cellular selectivity for nucleoli staining was achieved by simple chemical modification of carbon dots (C-dots) synthesized from waste carbon sources such as cow manure (or from glucose). The C-dots were characterized and functionalized (amine-passivated) with ethylenediamine, affording amide bonds that resulted in bright green fluorescence. The new modified C-dots were successfully applied as selective live-cell fluorescence imaging probes with impressive subcellular selectivity and the ability to selectively stain nucleoli in breast cancer cell lineages (MCF-7). The C-dots were also tested in four other cellular models and showed the same cellular selection in live-cell imaging experiments. [ABSTRACT FROM AUTHOR]

Photoactivatable (caged) fluorophores are widely used in chemistry, materials, and biology. However, the development of such molecules exhibiting photoactivable solid-state fluorescence is still challenging due to the aggregation-caused quenching (ACQ) effect of most fluorophores in their aggregate or solid states. In this work, we developed caged salicylaldehyde hydrazone derivatives, which are of aggregation-induced emission (AIE) characteristics upon used in chemistry, materials, and biology. However, the development of such molecules exhibiting photoactivable solid-state fluorescence is still challenging due to the aggregation-caused quenching (ACQ) effect of most fluorophores in their aggregate or solid states. In this work, we developed caged salicylaldehyde hydrazone derivatives, which are of aggregation-induced emission (AIE) characteristics upon light irradiation, as efficient photoactivatable solid-state fluorophores. These compounds displayed multiple-color emissions and ratiometric (photochromic) fluorescence switches upon wavelength-selective photoactivation, and were successfully applied for photopatterning and photoactivatable cell imaging in a multiple-color and stepwise manner. [ABSTRACT FROM AUTHOR]

Herein, a new strategy has been developed through combining a microwave-assisted technique with hydrothermal treatment to reduce graphene waste and improve production yield of graphene quantum dots (GQDs) prepared by top-down methods. By using fluorinated graphene oxide (FGO) as a raw material, fluorinated GQDs and nonfluorinated GQDs can be synthesized. Additionally, in the fluorinated GQDs, the protective shell supplied by fluorine improves the pH stability of photoluminescence and the strong electron-withdrawing group, F, reduces the π- electron density of the aromatic structure; thus inhibiting reactivity toward singlet oxygen produced during irradiation and improving the photostability. Therefore, the as-prepared fluorinated GQDs with excellent photo- and pH stability are suitable for long-term cellular imaging. [ABSTRACT FROM AUTHOR]

A series of new rationale designed 2,1,3-benzothiadiazole (BTD) fluorescent derivatives has been synthesized and applied for cellular selective staining of cancer cells in cell-imaging experiments. Four new synthesized BTD derivatives showed only poor or reasonable cellular selection, but with excellent fluorescence intensity and almost no background signal emitting at the blue or green channels. The knowledge gained by analysing their molecular architecture, however, allowed the planning and synthesis of a fluorescent BTD, which was then successfully tested and showed superior mitochondrial selection with outstanding results in bioimaging experiments in living cells. The new marker (named Splendor) was then compared with the commercially available MitoTracker Red (also through co-staining experiments) and showed far better mitochondrial selection, fluorescence intensity and chemical stability. Mitochondrial imaging and tracking (dynamic changes) was possible using Splendor during the whole cellular division cycle. DFT calculations were performed to offer insights into the origin of the chemical- and photostability of BTD derivatives. In addition, molecular docking calculations hint at a potential molecular target for the BTD derivatives in the mitochondrial protein adenine nucleotide translocase, which may explain the mitochondrial selectivity of Splendor versus the other four BTD derivatives. [ABSTRACT FROM AUTHOR]

We describe a straightforward strategy for the synthesis of strongly fluorescent pyridoindoles by Pd-catalyzed oxidative annulations of internal alkynes with C-3 functionalized indoles through CH/NH bond activation in a one-pot tandem process. Mechanistic investigations reveal the preferential activation of NH indole followed by CH activation during the cyclization process. Photophysical properties of pyridoindoles exhibited the highest fluorescence quantum yield of nearly 80 %, with emission color varying from blue to green to orange depending on the substructures. Quantum mechanical calculations provide insights into the observed photophysical properties. The strong fluorescence of the pyrido[1,2- a]indole derivative has been employed in subcellular imaging, which demonstrates its localization in the cell nucleus. [ABSTRACT FROM AUTHOR]

Carbon nanodots (C-dots) show great potential as an important material for biochemical sensing, energy conversion, photocatalysis, and optoelectronics because of their water solubility, chemical inertness, low toxicity, and photo- and electronic properties. Numerous methods have been proposed for the preparation of C-dots. However, complex procedures and strong acid treatments are often required, and the as-prepared C-dots tend to be of low quality, and in particular, have a low efficiency for photoluminescence. Herein, a facile and general strategy involving the electrochemical carbonization of low-molecular-weight alcohols is proposed. As precursors, the alcohols transited into carbon-containing particles after electrochemical carbonization under basic conditions. The resultant C-dots exhibit excellent excitation- and size-dependent fluorescence without the need for complicated purification and passivation procedures. The sizes of the as-prepared C-dots can be adjusted by varying the applied potential. High-quality C-dots are prepared successfully from different small molecular alcohols, suggesting that this research provides a new, highly universal method for the preparation of fluorescent C-dots. In addition, luminescence microscopy of the C-dots is demonstrated in human cancer cells. The results indicate that the as-prepared C-dots have low toxicity and can be used in imaging applications. [ABSTRACT FROM AUTHOR]

The design, synthesis, properties, and cell imaging applications of a series of 2-pyridyl disulfide based fluorescent probes (WSP1, WSP2, WSP3, WSP4 and WSP5) for hydrogen sulfide detection are reported. The strategy is based on the dual-nucleophilicity of hydrogen sulfide. A hydrogen sulfide mediated tandem nucleophilic substitution-cyclization reaction is used to release the fluorophores and turn on the fluorescence. The probes showed high sensitivity and selectivity for hydrogen sulfide over other reactive sulfur species, including cysteine and glutathione. [ABSTRACT FROM AUTHOR]

A new strategy for fast fluorescent detection of cysteine (Cys), based on a response-assisted electrostatic attraction, is demonstrated. By utilizing this strategy, we designed and synthesized three fluorescent probes for the specific detection of Cys under actual physiological conditions. The probe m- CP, a coumarin fluorophore conjugated with a substituted methyl pyridinium group through an unsaturated ketone unit, showed highly selective and sensitive detection for cysteine (Cys) over homocysteine (Hcy) and glutathione (GSH). The kinetic analysis indicated that the sensing process was highly accelerated (a response time less than 1 min) by the response-assisted electrostatic attraction. More importantly, control experiments with isomeric probes first demonstrated that the spatial charge configuration of the probe played an important role in Cys-preferred selectivity and kinetic rate acceleration. Furthermore, the practical utility of the probe m- CP in the fluorescent labeling of Cys residues within proteins was demonstrated. Finally, these probes were employed in living cell imaging with HeLa cells, in which it displayed satisfactory cell permeability and enabled us to distinguish active thiols in the cytoplasm, nucleus, and mitochondria. [ABSTRACT FROM AUTHOR]

Cover Feature: In Cellulo Generation of Fluorescent Probes for Live-Cell Imaging of Cylooxygenase-2 (Chem. Eur. J. 10/2021) Keywords: cancer; drug design; fluorescence; fluorogenic click chemistry; imaging agents; live cell imaging EN cancer drug design fluorescence fluorogenic click chemistry imaging agents live cell imaging 3189 3189 1 02/17/21 20210215 NES 210215 B In cellulo generation of fluorescent probes b is an essential tool in chemical biology to visualize the dynamics of biological processes in real-time. Cancer, drug design, fluorescence, fluorogenic click chemistry, imaging agents, live cell imaging. [Extracted from the article]

A new scaffold for producing efficient organic fluorescent materials was identified: 2,5‐diamino‐1,3‐diarylpyrimidine featuring a C4N4 elemental composition. Single‐step installation of two aryl groups at the 4,6‐positions of the pyrimidine core delivered fluorescent organic materials in a modular fashion. A variety of fluorescent compounds with distinct absorption/emission properties was readily accessed in a modular fashion by varying the peripheral aromatic attachments. This cover picture visualizes the central C4N4 core efficiently harvesting light to intensely emit fluorescence in a range of wavelengths. More information can be found in the Communication by M. Shibasaki, N. Kumagai, et al. on page 4299. [ABSTRACT FROM AUTHOR]

A correction to the article “Simultaneous Imaging of Mitochondria and Lysosomes using Two-Photon Fluorescent Probes" that was published in the 2012 issue of the journal is presented.

Live Cell Imaging A series of newly designed 2,1,3 ‐ benzothiadiazole (BTD) fluorescent derivatives has been synthesized and applied for selective mitochondrial staining and dynamics inside live cells. The most selective biomarker (Splendor) showed an impressive subcellular localization with a bright green fluorescence emission revealing important features of the organelle distribution and dynamics during the cell division. For more details, see the Full Paper by B. A. D. Neto et al. on page 15360 ff. [ABSTRACT FROM AUTHOR]