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Standing wave (SW) microscopy is a method that uses an interference pattern to excite fluorescence from labelled cellular structures and produces high‐resolution images of three‐dimensional objects in a two‐dimensional dataset. SW microscopy is performed with high‐magnification, high‐numerical aperture objective lenses, and while this results in high‐resolution images, the field of view is very small. Here we report upscaling of this interference imaging method from the microscale to the mesoscale using the Mesolens, which has the unusual combination of a low‐magnification and high‐numerical aperture. With this method, we produce SW images within a field of view of 4.4 mm × 3.0 mm that can readily accommodate over 16,000 cells in a single dataset. We demonstrate the method using both single‐wavelength excitation and the multi‐wavelength SW method TartanSW. We show application of the method for imaging of fixed and living cells specimens, with the first application of SW imaging to study cells under flow conditions. LAY DESCRIPTION: With a standard microscope, it is possible to interfere two or more beams of light and produce a contour map of cell structures using a technique known as standing wave microscopy. This method is usually applied with high power objective lenses, and only a tiny area can be studied, usually showing structural detail from one or two cells at most. The Mesolens is a unique objective lens that has been designed and manufactured to image large populations of cells in a single image. Two‐dimensional images of cells can be obtained with the Mesolens using regular illumination methods, but the cell topography is lost. Here we have combined standing wave illumination with the Mesolens to perform topographical imaging of large numbers of cells in a single image. We first proved the method with a non‐biological specimen comprised of a glass lens, and then we applied the technique to imaging of fixed and living cells: in the case of red blood cells, we showed that we can study the topography of more than 16,000 cells in a single image. With the much larger area of study afforded by the Mesolens, we also used standing wave illumination for the first time monitor red blood cell topography when the cells are subject to flow environment. This new application of standing wave imaging at unusually large spatial scales may prove useful for studying behaviour in the circulatory system. [ABSTRACT FROM AUTHOR]

Organic and polymer fluorescent nanomaterials are a frontier research focus. Here in this work, a series of fluorinated zwitterionic random copolymers end‐attached with a quasi‐chromophoric group of pyrene or tetraphenylethylene (TPE) are well synthesized via atom transfer radical polymerization with activators regenerated by electron transfer (ARGET ATRP). Those random copolymers with total degree of polymerization 100 or 200 are able to produce fluorescent single‐chain nanoparticles (SCNPs) through intra‐chain self‐folding assembly with quite uniform diameters in the range of 10–20 nm as characterized by dynamic light scattering and transmission electron microscopy. By virtue of the segregation or confinement effect, both SCNPs functionalized with pyrene or TPE group are capable of emitting fluorescence, with pyrene tethered SCNPs exhibiting stronger fluorescence emission reaching the highest quantum yield ≈20%. Moreover, such kind of fluorescent SCNPs manifest low cytotoxicity and good cell imaging performance for Hela cells. The creation of fluorescent SCNPs through covalently attached one quasi‐chromophore to the end of one fluorinated zwitterionic random copolymer provides an alternative strategy for preparing polymeric luminescence nanomaterials, promisingly serving as a new type of fluorescent nanoprobes for biological imaging applications. [ABSTRACT FROM AUTHOR]

Synthesis and photophysical properties of a fluorescent probe HBD is described. Probe upon interaction with metal ions, anions and nucleoside pyrophosphates (NPPs) showed fluorescence quenching with Cu2+ due to chelation enhanced quenching effect (CHEQ). Moreover, interaction of ensemble HBD.Cu2+ with anions and NPPs showed fluorescence “turn‐On” response with ATP selectively. “On‐Off‐On” responses observed with Cu2+ and ATP is attributed to an interplay between ESIPT and TICT processes. Cyclic voltammogram of probe exhibited quasi‐reversible redox behaviour with three oxidation and two reduction potentials and the change in band gaps of probe suggested the interaction with Cu2+ and ATP. The 2 : 1 and 1 : 1 binding stoichiometry for an interaction between probe and Cu2+ (LOD, 62 nM) and ensemble, HBD.Cu2+ with ATP (LOD, 0.4 μM) respectively are realised by Job's plot and HRMS data. Cell imaging studies carried out to detect Cu2+ and ATP in HeLa cells. Also, the output emission observed with Cu2+ and ATP is utilized to construct an implication (IMP) logic gate. Test paper strips showed naked‐eye visible color responses to detect Cu2+ and ATP. In real water samples probe successfully detected copper (0.03 μM) between 5–6.5 ppb level (ICP‐MS method). [ABSTRACT FROM AUTHOR]

The deployment of small‐molecule fluorescent agents plays an ever‐growing role in medicine and drug development. Herein, we complement the portfolio of powerful fluorophores, reporting the serendipitous discovery and development of a novel class with an imidazo[1,2‐a]pyridinium triflate core, which we term PyrAtes. These fluorophores are synthesized in a single step from readily available materials (>60 examples) and display Stokes shifts as large as 240 nm, while also reaching NIR−I emissions at λmax as long as 720 nm. Computational studies allow the development of a platform for the prediction of λmax and λEm. Furthermore, we demonstrate the compatibility of these novel fluorophores with live cell imaging in HEK293 cells, suggesting PyrAtes as potent intracellular markers. [ABSTRACT FROM AUTHOR]

Biologically‐active near‐ultraviolet emitting spirooxindole‐pyrrolidine/pyrrolothiazole‐β‐ketothiolester have been synthesised via Chemo‐/regio‐/stereoselective manner. Excited‐state intramolecular proton transfer (ESIPT) of β‐ketothiolester exhibits excitation‐dependent emission with intermolecular hydrogen bonding ability with solvents. The emission could be tunable between 330 nm to 460 nm. Selected fluorescent compounds 4{4,2,1}, 4{12,2,2}, 5{4,2,1} and 5{12,2,2} shows cytotoxicity effect on PC3 cells, where the highest IC50 value (6 μM) was found for the probe 5{12,2,2}. The fluorescent behavior of 5{4,2,1} and 5{12,2,2} acted as an imaging molecule against cancer cells. [ABSTRACT FROM AUTHOR]

Heavy metal contamination has become a global environmental problem and currently drawn much attention from researchers in worldwide. High exposure to heavy metals can lead to problems like kidney, liver and brain damage, skin and lung cancer, etc. Rapid and sensitive detection of heavy metals is of immense importance in environmental monitoring. Over the past few decades, enormous efforts have been made to design various sensors to identify and monitor these harmful metal ions. In Comparison with other methods, fluorescence‐based chemosensors have received extensive attention because of the advantages of high sensitivity, low cost, real‐time monitoring, simple operation, etc. The pyrene derivatives are significant polycyclic aromatic hydrocarbons (PAHs) with strong fluorescence. They are widely used as fluorescent probes in many applications due to their easy modification, high fluorescence quantum yield, and strong fluorescence emission in live cells, outstanding cell permeability, and very low cytotoxicity. The SDG 6: Clean water and sanitation alarm a strong strategy, and careful identification of the risk connected to environmental pollutants needs urgent attention in this situation. Therefore, we highlight different types of pyrene‐based fluorophores and the fluorescence mechanisms for the sensitive and selective detection methodology of Arsenic, Mercury, Cadmium, Lead, and Chromium heavy metals. [ABSTRACT FROM AUTHOR]

A light controllable two‐photon near‐infrared (NIR) optical probe is conveniently constructed by multivalent supramolecular co‐assembly of amphiphilic sulfonatocalix[4]arene (SC4A), tricationic triphenylamine (TPA), and diarylethene derivative (DE). The obtained results indicate that the formed SC4A/TPA nanoparticle displays assemble‐confined behaviors and enhances the two‐photon excited NIR emission. Benefiting from the reversible ring‐opened and closed behaviors of the DE under 365 and > 600 nm light irradiation, the dicationic DE in the assembly could act as an energy acceptor after 365 nm light irradiation, then the co‐assembly of SC4A/TPA/DE could achieve a NIR fluorescence ON and OFF switch and is successfully applied in HeLa cell imaging, providing a convenient approach to supramolecular two‐photon switch for cell imaging. [ABSTRACT FROM AUTHOR]

Detection of correct oxidation state of a metal ion is important to understand its speciation and redox properties. Some of rhodamine derivatives can identify Al3+, Cr3+ and Fe3+ as the trivalent cations. We have synthesized a rhodamine derivative, HL‐qui, from the reaction of N‐(rhodamine‐6G)lactam‐ethylenediamine with quinoline‐2‐carboxaldehyde for the colorimetric as well as fluorogenic detection of all of metal ions with +3 oxidation state such as Al3+, Cr3+, Fe3+, Ga3+, In3+, Tl3+ and Gd3+. In the presence of these trivalent cations, colorless and nonfluorescent HL‐qui turns pink and strongly fluorescent in HEPES buffer (10 mM) in H2O/ethanol=1/9 (v/v) (pH 7.4) as its spirolactam ring gets open to show the changes in color and fluorescence properties. High sensitivity of the probe towards the cations is reflected from the limit of detection values that are in nM range. To the best of our knowledge, there is no such report where fluorescence sensing has been utilized to determine oxidation state. This multi‐ion sensing feature has been used for fabrication of multi input‐output based logic circuit using Boolean algebraic method. It has been used in imaging of metal ions in living cell (L6 cells). [ABSTRACT FROM AUTHOR]

By synergistically employing four key strategies: (I) introducing tetraphenylethylene groups as the central core unit with aggregation‐induced emission (AIE) properties, (II) optimizing the π‐conjugated length by extending the building block branches, (III) incorporating flexible groups containing ethylenic bonds, and (IV) applying crystal engineering to attain dense stacking mode and highly twisty conformation, we successfully synthesized a series of hydrogen‐bonded organic frameworks (HOFs) exhibiting exceptional one/two‐photon excited fluorescence. Notably, when utilizing the fluorescently superior building block L2, HOF‐LIFM‐7 and HOF‐LIFM‐8 exhibiting high quantum yields (QY) of 82.1 % and 77.1 %, and ultrahigh two‐photon absorption (TPA) cross‐sections of 148959.5 GM and 123901.1 GM were achieved. These materials were successfully employed in one and two‐photon excited lysosome‐targeting cellular imaging. It is believed that this strategy, combining building block optimization and crystal engineering, holds significant potential for guiding the development of outstanding fluorescent HOF materials. [ABSTRACT FROM AUTHOR]

By synergistically employing four key strategies: (I) introducing tetraphenylethylene groups as the central core unit with aggregation‐induced emission (AIE) properties, (II) optimizing the π‐conjugated length by extending the building block branches, (III) incorporating flexible groups containing ethylenic bonds, and (IV) applying crystal engineering to attain dense stacking mode and highly twisty conformation, we successfully synthesized a series of hydrogen‐bonded organic frameworks (HOFs) exhibiting exceptional one/two‐photon excited fluorescence. Notably, when utilizing the fluorescently superior building block L2, HOF‐LIFM‐7 and HOF‐LIFM‐8 exhibiting high quantum yields (QY) of 82.1 % and 77.1 %, and ultrahigh two‐photon absorption (TPA) cross‐sections of 148959.5 GM and 123901.1 GM were achieved. These materials were successfully employed in one and two‐photon excited lysosome‐targeting cellular imaging. It is believed that this strategy, combining building block optimization and crystal engineering, holds significant potential for guiding the development of outstanding fluorescent HOF materials. [ABSTRACT FROM AUTHOR]

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]

Aryl alcohol‐type or phenolic fluorophores offer diverse opportunities for developing bioimaging agents and fluorescence probes. Due to the inherently acidic hydroxyl functionality, phenolic fluorophores provide pH‐dependent emission signals. Therefore, except for developing pH probes, the pH‐dependent nature of phenolic fluorophores should be considered in bioimaging applications but has been neglected. Here we show that a simple structural remedy converts conventional phenolic fluorophores into pH‐resistant derivatives, which also offer "medium‐resistant" emission properties. The structural modification involves a single‐step introduction of a hydrogen‐bonding acceptor such as morpholine nearby the phenolic hydroxyl group, which also leads to emission bathochromic shift, increased Stokes shift, enhanced photo‐stability and stronger emission for several dyes. The strategy greatly expands the current fluorophores' repertoire for reliable bioimaging applications, as demonstrated here with ratiometric imaging of cells and tissues. [ABSTRACT FROM AUTHOR]

Aryl alcohol‐type or phenolic fluorophores offer diverse opportunities for developing bioimaging agents and fluorescence probes. Due to the inherently acidic hydroxyl functionality, phenolic fluorophores provide pH‐dependent emission signals. Therefore, except for developing pH probes, the pH‐dependent nature of phenolic fluorophores should be considered in bioimaging applications but has been neglected. Here we show that a simple structural remedy converts conventional phenolic fluorophores into pH‐resistant derivatives, which also offer "medium‐resistant" emission properties. The structural modification involves a single‐step introduction of a hydrogen‐bonding acceptor such as morpholine nearby the phenolic hydroxyl group, which also leads to emission bathochromic shift, increased Stokes shift, enhanced photo‐stability and stronger emission for several dyes. The strategy greatly expands the current fluorophores' repertoire for reliable bioimaging applications, as demonstrated here with ratiometric imaging of cells and tissues. [ABSTRACT FROM AUTHOR]

Organic nanomaterials, as nanocarrier platforms, have tremendous potential for biomedical applications. The authors successfully prepared novel two‐dimensional covalent organic nanosheets (CONs) that can be used as efficient in vivo bioimaging probes by condensing 1,3,5‐triformylglucinol (Tp) and 2,7‐diaminopyrene (Py) to produce TpPy covalent organic frameworks (COFs). TpPy COFs are then subjected to a liquid exfoliation process to obtain TpPy CONs (< 200 nm in size and < 1.7 nm in thickness). TpPy CONs disperse well in water to provide a stable, homogeneous colloidal suspension, which shows favorable photoluminescence properties. Cell viability tests using MDA‐MB‐231 and RAW 264.7 cells reveal that TpPy CONs are low in cytotoxicity. Confocal microscopy reveals clear fluorescent cell images after incubation with TpPy CONs for 24 h, without reduction in cell activity or cytosolic aggregation. To investigate the biological behavior of the TpPy CONs, the authors perform an in vivo fluorescence imaging study using MDA‐MB‐231 tumor‐bearing mice. After intravenous injection of TpPy CONs disperse in phosphate‐buffered saline (PBS), persistent and strong fluorescence signals are observed in the tumor region, with low background signals from normal tissues at 1, 3, 12, and 24 h after injection. Furthermore, these in vivo imaging results concurred with ex vivo biodistribution and histological results. [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]

Delayed fluorescence molecules have important applications in time‐resolved luminescence imaging (including lifetime imaging) systems. However, existing approaches of generating delayed fluorescence in organic molecules rely on triplets as long‐lived intermediate states. As such, this triplet‐based delayed fluorescence can be severely plagued by its oxygen sensitivity. As the presence of oxygen or ambient air can hardly be avoided in living biosystems, oxygen‐insensitive delayed fluorescence is highly desirable. Herein, a new pathway is reported for oxygen‐insensitive delayed fluorescence which is produced only within the singlet manifold. Such an example is found in a cyto‐compatible and water‐soluble trimethine cyanine dye C3T‐H, which bears a very high molar extinction coefficient and a narrow‐band red emission. It is demonstrated that this dye exhibits notable delayed fluorescence which cannot be diminished by the presence of oxygen or ambient air. Time‐resolved imaging of living cells in the presence of oxygen is successfully achieved. Through quantum chemical calculations, a nonemissive dark‐state structure in the S1 state is found to be thermodynamically viable (energy barrier ≈8 kcal mol−1) through the molecular twisting around the trimethine bridge of C3T‐H, which serves as a "reservoir" of the excitation energy to enable the oxygen‐insensitive delayed fluorescence. [ABSTRACT FROM AUTHOR]

Nontraditional small organic luminogens (NTSOLs) without classic conjugated chromophores have attracted significant attention. However, the design and synthesis of NTSOLs with fluorescence in the red region remain significantly challenging. In this study, we established a self‐catalyzed hydroxyl‐yne click reaction for preparing long‐wavelength and red‐emitting NTSOLs. Owing to their perfect reaction selectivity, high efficiency, and excellent universality, a series of compounds with well‐defined structures were obtained in high yields. Moreover, the obtained compounds showed concentration‐enhanced and excitation‐dependent emission characteristics. The compounds also exhibited dramatical chemical structure‐dependent and aggregation‐induced red‐shifted fluorescence properties, based on which we successfully obtained red‐emitting NTSOLs by simply adjusting chemical structure and concentration. Also, the compounds show good cell staining ability, which can be used in cell imaging. [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]

This paper presents the synthesis, photophysical characterization and use for cell imaging of 14 fluorophores derived from a hybrid Naphthalimide/Cinnoline fused backbone called "CinNapht". Photophysical properties of these fluorophores including absorbance, excitation and emission spectra have been recorded in CHCl3, DMSO and PBS+5 %BSA. They exhibit red emission associated to a large Stokes shift and fluorescence quantum yields up to 52 %. Theoretical calculations have been undertaken in order to provide elements of rationalization for a major part of the results. Some of these analogues have been tuned to enable imaging of cell organelles such as mitochondria, lysosome or lipid droplets. This study comes to confirm that CinNapht dyes can be considered as relevant alternatives to existing tools for cell imaging. [ABSTRACT FROM AUTHOR]

A novel ratiometric fluorescent probe HB‐2 based on benzothiazole for hypobromous acid (HBrO) was synthesized and studied. After HBrO was added to the CH3CN‐HEPES solution of the HB‐2, the probe cyclized to form a sulfimine bond, which increased the conjugated degree of the system. The fluorescence emission peak of the reaction system at 447 nm gradually decreased, while the newly generated emission peaks gradually increased at 580 nm. The ratio of the fluorescence intensity at the two wavelengths of 447 nm and 580 nm increased about 234 times. Moreover, it has successfully been used to stain and record microscopy images of 4T1 cells, and the presence of exogenous HBrO could be judged by the change of fluorescence intensity. [ABSTRACT FROM AUTHOR]

Fluorophores lay the material basis for tissue labeling and fluorescence imaging, especially for deep‐brain multiphoton microscopy (MPM) in animal models. Among various fluorescent materials, those with aggregation‐induced emission (AIE) characteristics, i.e., AIEgens, have excellent optical properties and biocompatibility and thus have found widespread applications in biomedical imaging. However, their application to deep‐brain MPM has so far been limited in imaging depth, which undoubtedly poses a hindrance to neurological research aiming to probe the deeper brain. In order to address the issue, here a novel bright AIEgen, namely MTTCM, is designed and synthesized via facile reactions routes. The self‐assembled MTTCM nanoparticles (NPs) with their water‐dispersible feature, have good biocompatibility and good photostability. Furthermore, they are spectrally advantageous for deep‐brain MPM: their emission lies in the NIR‐I region, they generate 3‐photon fluorescence with NIR‐III excitation and show only a slight blue‐shift in the emitted 3‐photon fluorescence in vivo. From a fundamental photochemical perspective, it is also confrimed that MTTCM NPs obey Kasha's rule since the measured 3‐photon and 1‐photon fluorescence spectra overlap. All these merits make MTTCM NPs the enabling fluorophores for record depth in brain imaging in vivo: 1905 µm after craniotomy and 1100 µm through an intact skull, excited at 1660 nm. Furthermore, a record 752 µm hemodynamic imaging depth before craniotomy is demonstrated, from which the blood flow speed can be measured. MTTCM NPs are thus promising fluorophores for deep‐brain 3‐photon imaging in vivo. [ABSTRACT FROM AUTHOR]

A purely organic supramolecular assembly emitting three‐photon room‐temperature phosphorescence (RTP) is constructed from a macrocyclic host, cucurbit[8]uril (CB[8]), and 4‐bromophenyl pyridine salt having an alkyl chain length of 6 or 12 carbon atoms (6C and 12C, respectively). Benefiting from macrocyclic host confined guests, the encapsulation of 12C and 6C in the CB[8] cavity results in three‐photon absorption and subsequent near‐infrared (NIR) phosphorescence emission. Notably, secondary assembly with sulfonated β‐cyclodextrin (SCD) further enhances the phosphorescence emission of the multilevel supramolecular assembly. NIR‐delayed fluorescence via a light‐harvesting phosphorescent energy transfer system is achieved by adding Nile blue as a substrate. Comparison of 12C/CB[8]/SCD and 6C/CB[8]/SCD shows that a long hydrophobic layer is more conducive to stabilizing NIR‐delayed fluorescence emission. These findings indicate that multilevel supramolecular assemblies can be used for three‐photon‐excited NIR‐delayed fluorescence and RTP imaging of cancer cells, which greatly expands the biological applications of pure organic RTP materials. [ABSTRACT FROM AUTHOR]

As an emerging nano‐functional material, fluorescent carbon nanodots (CDs) have made breakthroughs in many fields. In our research, graphite‐like nitrogen‐doped carbon nanodots (N‐CDs) with excellent down‐ and up‐conversion fluorescent properties were synthesized by a facile one‐step solvothermal method using tri‐isopropanolamine (TIPA) as carbon and nitrogen sources. Mean particle diameter from 2.85 to 5.62 nm can be obtained by controlling the amount of HNO3 during synthesis. With low cytotoxicity and excellent fluorescence properties, the prepared N‐CDs can well label HeLa cells, which has great potential in the field of cell imaging. This work could enrich the research on the preparation and application of N‐CDs. [ABSTRACT FROM AUTHOR]

In photoswitches that undergo fluorescence switching upon ultraviolet irradiation, photoluminescence and photoisomerization often occur simultaneously, leading to unstable fluorescence properties. Here, we successfully demonstrated reversible solid‐state triple fluorescence switching through "Pump–Trigger" multiphoton manipulation. A novel fluorescence photoswitch, BOSA‐SP, achieved green, yellow, and red fluorescence under excitation by pump light and isomerization induced by trigger light. The energy ranges of photoexcitation and photoisomerization did not overlap, enabling appropriate selection of the multiphoton light for "pump" and "trigger" photoswitching, respectively. Additionally, the large free volume of the spiropyran (SP) moiety in the solid state promoted reversible photoisomerization. Switching between "pump" and "trigger" light is useful for three‐color tunable switching cell imaging, which can be exploited in programmable fluorescence switching. Furthermore, we exploited reversible dual‐fluorescence switching in a single molecular system to successfully achieve two‐color super‐resolution imaging. [ABSTRACT FROM AUTHOR]

In photoswitches that undergo fluorescence switching upon ultraviolet irradiation, photoluminescence and photoisomerization often occur simultaneously, leading to unstable fluorescence properties. Here, we successfully demonstrated reversible solid‐state triple fluorescence switching through "Pump–Trigger" multiphoton manipulation. A novel fluorescence photoswitch, BOSA‐SP, achieved green, yellow, and red fluorescence under excitation by pump light and isomerization induced by trigger light. The energy ranges of photoexcitation and photoisomerization did not overlap, enabling appropriate selection of the multiphoton light for "pump" and "trigger" photoswitching, respectively. Additionally, the large free volume of the spiropyran (SP) moiety in the solid state promoted reversible photoisomerization. Switching between "pump" and "trigger" light is useful for three‐color tunable switching cell imaging, which can be exploited in programmable fluorescence switching. Furthermore, we exploited reversible dual‐fluorescence switching in a single molecular system to successfully achieve two‐color super‐resolution imaging. [ABSTRACT FROM AUTHOR]

Lowly expressed analyte in complex cytoplasmic milieu necessitates the development of non‐enzymatic autocatalytic DNA circuits with high amplification and anti‐interference performance. Herein, we engineered a versatile and robust stimuli‐responsive autocatalytic hybridization assembly (AHA) circuit for high‐performance in vivo bioanalysis. Under a moderately confined condition, the initiator motivated the autonomous and cooperative cross‐activation of cascade hybridization reaction and catalytic DNA assembly for generating an exponentially amplified readout without the parasite steric hindrance and random diffusion side effects. The AHA circuit was systematically investigated by a series of experimental studies and theoretical simulations. The successively guaranteed target recognition and synergistically accelerated signal‐amplification enabled the sensitive and selective detection of analyte, and realized the robust miRNA imaging in living cells and mice. This autocatalytic DNA circuit could substantially expand the toolbox for accurate diagnosis and programmable therapeutics. [ABSTRACT FROM AUTHOR]

Lowly expressed analyte in complex cytoplasmic milieu necessitates the development of non‐enzymatic autocatalytic DNA circuits with high amplification and anti‐interference performance. Herein, we engineered a versatile and robust stimuli‐responsive autocatalytic hybridization assembly (AHA) circuit for high‐performance in vivo bioanalysis. Under a moderately confined condition, the initiator motivated the autonomous and cooperative cross‐activation of cascade hybridization reaction and catalytic DNA assembly for generating an exponentially amplified readout without the parasite steric hindrance and random diffusion side effects. The AHA circuit was systematically investigated by a series of experimental studies and theoretical simulations. The successively guaranteed target recognition and synergistically accelerated signal‐amplification enabled the sensitive and selective detection of analyte, and realized the robust miRNA imaging in living cells and mice. This autocatalytic DNA circuit could substantially expand the toolbox for accurate diagnosis and programmable therapeutics. [ABSTRACT FROM AUTHOR]

Dual red‐emitting fluorescent and water‐soluble silver nanoclusters (AgNCs) were synthesized in aqueous solutions through the reduce reaction method using lipoic acid‐modified‐poly(vinyl alcohol) as a novel protective ligand and sodium borohydride as a reducing agent. The obtained AgNCs exhibited a large Stokes shift and high stability. The fluorescence lifetime of the obtained AgNCs was 1.4×104 ns and the corresponding quantum yield reached 7.1 %. The obtained AgNCs showed highly sensitive and selective detection of Cu2+, in which the evaluation of Cu2+ was allowed in the range of 0–28 μM with a limit of detection (LOD) as low as 0.71 μM. Moreover, the obtained AgNCs are explored to application for bioimaging through incubation with ID8 cells. [ABSTRACT FROM AUTHOR]

Inside living cells, regulation of catalytic activity of artificial enzymes remains challenging due to issues such as biocompatibility, efficiency, and stability of the catalyst, by which the practical applications of artificial enzymes have been severely hindered. Here, an artificial enzyme, PTT‐SGH, with responsiveness to reactive oxygen species (ROS), was obtained by introducing a catalytic histidine residue to pentaerythritol tetra(3‐mercaptopropionate) (PTT). The artificial enzyme formed large aggregates in cells via the intracellular ROS‐mediated oxidation of thiol groups. The process was significantly facilitated in tumor cells because of the higher ROS concentration in the tumor microenvironment. The catalytic activity of this artificial enzyme was intensively enhanced through deprotonation of cross‐linked PTT‐SGH, which showed typical esterase activities. Selective fluorescence imaging of tumor cells was achieved using the artificial enzyme to trigger the cleavage of the ester bond of the caged fluorophore inside living cells. [ABSTRACT FROM AUTHOR]

Inside living cells, regulation of catalytic activity of artificial enzymes remains challenging due to issues such as biocompatibility, efficiency, and stability of the catalyst, by which the practical applications of artificial enzymes have been severely hindered. Here, an artificial enzyme, PTT‐SGH, with responsiveness to reactive oxygen species (ROS), was obtained by introducing a catalytic histidine residue to pentaerythritol tetra(3‐mercaptopropionate) (PTT). The artificial enzyme formed large aggregates in cells via the intracellular ROS‐mediated oxidation of thiol groups. The process was significantly facilitated in tumor cells because of the higher ROS concentration in the tumor microenvironment. The catalytic activity of this artificial enzyme was intensively enhanced through deprotonation of cross‐linked PTT‐SGH, which showed typical esterase activities. Selective fluorescence imaging of tumor cells was achieved using the artificial enzyme to trigger the cleavage of the ester bond of the caged fluorophore inside living cells. [ABSTRACT FROM AUTHOR]

Lipid droplets (LDs) are organelles composed of a lipid core surrounded by a phospholipid monolayer, plays an important role in a variety of physiological processes as well as diseases. In this work, TPAs‐SCH3‐2CN with an enhanced electron D‐π‐A system, is synthesized, which makes itself as an orange emission compound (Em=590 nm) and also have high polarity. It is verified that TPAs‐SCH3‐2CN is an excellent LDs‐targeted probe, and it also sensitive to the ClO− detection in vitro and in cells. Impressively, due to the high lipophilicity, TPAs‐SCH3‐2CN is able to stain the yolk lipids in zebrafish, exhibiting the potential for monitoring lipid transport and metabolism processes. [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]

Transforming carbon dots (CDs) fluorescent materials into smart materials with complex functions is a topic of great interest to nanoscience. However, designing CDs with regulating fluorescence/phosphorescence that can be visually monitored with the environment changes in real‐time remains a challenge. Here, a very simple strategy, one‐step solvent‐free catalytic assistant strategy, which is low cost, facile, environment‐friendly, and high throughput, is put forward. Hydrogen bond is used to manipulate nanostructure of CDs, and the obtained carbon dots (M‐CDs) show a series of attractive properties including matrix‐free room‐temperature phosphorescence, time‐dependent fluorescence, and near‐infrared emissive characteristics. Different from the traditional aggregation caused quenching or aggregation‐induced emission fluorescent materials, M‐CDs exhibit unprecedented and unique dispersion induced redshift fluorescence phenomenon, promoting the studies of fluorescence from static to dynamic. The causes of this phenomenon are further analyzed in detail. As a kind of intelligent fluorescent materials, this new designed CDs greatly enrich the basic recognition of CDs by illustrating the relationship between redshift fluorescence behaviors and the dispersion states, and may provide with an opportunity for solid‐state fluorescent materials, anti‐counterfeiting, cellular imaging, and hopefully many others. [ABSTRACT FROM AUTHOR]

Transforming carbon dots (CDs) fluorescent materials into smart materials with complex functions is a topic of great interest to nanoscience. However, designing CDs with regulating fluorescence/phosphorescence that can be visually monitored with the environment changes in real‐time remains a challenge. Here, a very simple strategy, one‐step solvent‐free catalytic assistant strategy, which is low cost, facile, environment‐friendly, and high throughput, is put forward. Hydrogen bond is used to manipulate nanostructure of CDs, and the obtained carbon dots (M‐CDs) show a series of attractive properties including matrix‐free room‐temperature phosphorescence, time‐dependent fluorescence, and near‐infrared emissive characteristics. Different from the traditional aggregation caused quenching or aggregation‐induced emission fluorescent materials, M‐CDs exhibit unprecedented and unique dispersion induced redshift fluorescence phenomenon, promoting the studies of fluorescence from static to dynamic. The causes of this phenomenon are further analyzed in detail. As a kind of intelligent fluorescent materials, this new designed CDs greatly enrich the basic recognition of CDs by illustrating the relationship between redshift fluorescence behaviors and the dispersion states, and may provide with an opportunity for solid‐state fluorescent materials, anti‐counterfeiting, cellular imaging, and hopefully many others. [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]

Photoactivated trimerization of 2,3,3‐trimethyl‐3H‐indole derivatives created near infrared fluorophore Cy5. The synthetic method is air‐tolerant, photosensitizer free, metal free, and condensation agent free. Living cells make Cy5 on a time scale of minutes under white light irradiation at a low power intensity, with the monomer as the only exogenous agent. The new method is promising to find applications in cell studies for in situ spatiotemporally controlled fluorescence imaging in living cells. [ABSTRACT FROM AUTHOR]

Photoactivated trimerization of 2,3,3‐trimethyl‐3H‐indole derivatives created near infrared fluorophore Cy5. The synthetic method is air‐tolerant, photosensitizer free, metal free, and condensation agent free. Living cells make Cy5 on a time scale of minutes under white light irradiation at a low power intensity, with the monomer as the only exogenous agent. The new method is promising to find applications in cell studies for in situ spatiotemporally controlled fluorescence imaging in living cells. [ABSTRACT FROM AUTHOR]

Embryos and microscopes share a long, remarkable history and biologists have always been intrigued to watch how embryos develop under the microscope. Here we discuss the advances in microscopy which have greatly influenced our current understanding of embryogenesis. We highlight the evolution of microscopes and the optical technologies that have been instrumental in studying various developmental processes. These imaging modalities provide mechanistic insights into the dynamic cellular and molecular events which drive lineage commitment and morphogenetic changes in the developing embryo. We begin the journey with a brief history of microscopy to study embryos. First, we review the principles and optics of light, fluorescence, confocal, and electron microscopy which have been key techniques for imaging cellular and molecular events during embryonic development. Next, we discuss recent key imaging modalities such as light‐sheet microscopy, which are suitable for whole embryo imaging. Further, we highlight imaging techniques like multiphoton and super resolution microscopy for beyond light diffraction limit, high resolution imaging. Lastly, we review some of the scattering‐based imaging methods and techniques used for imaging human embryos. [ABSTRACT FROM AUTHOR]

A highly emissive microgel is synthesized by polymerizing tetraphenylethene (TPE) based comonomers, acrylic acid, NIPAM, and permanent crosslinker ethylenebisacrylamide (BIS) (named as TPE microgel), which exhibited temperature responsive fluorescence emission. Rhodamine B (RhB), a positively charged molecule, is then inserted onto the surface of fabricated microgels through electrostatic interaction. As a result, a novel artificial light harvesting system with high energy transfer efficiency is constructed (named as TPE microgel‐RhB light harvesting system), which is the first light harvesting system based on TPE microgels presenting dual response to pH and temperature. MTT assay indicates the fabricated TPE microgel and TPE microgel‐RhB light harvesting system has good cytocompatibility. The strong fluorescence and good cytocompatibility make them perfect candidates for cell imaging. The prepared emissive microgel and light‐harvesting system with desirable fluorescent property not only provide a new strategy for the fabrication of tunable luminescent nanomaterials, but also expand potential applications in the fields of stomach recognition, temperature sensors, and drug delivery. [ABSTRACT FROM AUTHOR]

As one of the most important minerals in the body, potassium is vital for the heart and neurons. Methods that can non‐invasively and accurately monitor changes in potassium balances would benefit disease diagnoses as well as offer insight into pathologies. Among the sensing approaches, fluorescent probes serve as a unique detection method for its simplicity, tunable detection range, and bioimaging ability. The design of new probes with highly selective K+ receptors and transduction functionality remains a challenge that is motivated by numerous sensing and detection applications. In this minireview, fluoroionophores are summarized that undergo transduction, producing fluorescence signals when interacting with, e. g. potassium ions. The properties of ionophores (afford selective interaction with potassium) and fluorophores (generate signal read‐out) are discussed. Molecular structure design and sensing mechanisms are included along with cell imaging applications. The selectivity towards K+ and the absorption/emission characteristics of the probes are of particular interest. [ABSTRACT FROM AUTHOR]

Super‐resolution optical fluctuation imaging (SOFI) is a super‐resolution microscopy technique that overcomes the diffraction limit by analyzing intensity fluctuations of statistically independent emitters in a time series of images. The final images are background‐free and show confocality and enhanced spatial resolution (super‐resolution). Fluorophore photobleaching, however, is a key limitation for recording long time series of images that will allow for the calculation of higher order SOFI results with correspondingly increased resolution. Here, we demonstrate that photobleaching can be circumvented by using fluorophore labels that reversibly and transiently bind to a target, and which are being replenished from a buffer which serves as a reservoir. Using fluorophore‐labeled short DNA oligonucleotides, we labeled cellular structures with target‐specific antibodies that contain complementary DNA sequences and record the fluctuation events caused by transient emitter binding. We show that this concept bypasses extensive photobleaching and facilitates two‐color imaging of cellular structures with SOFI. [ABSTRACT FROM AUTHOR]

NO donors have found wide medical use long before the biorelevance of nitric oxide (NO) was unveiled. From glyceryl trinitrate, amyl nitrite and nitroprusside, to nitrosothiols, NONOates and more, a wide variety of chemicals have been employed as nitric oxide donors for treating pathological conditions and investigating the NO biology. Yet, the release kinetics of these classic NO donors are hard‐to‐define and hard‐to‐monitor in biological milieu. Novel NO donors with robustly defined NO release profiles are sought after. These endeavours have introduced a plethora of novel NO donors, including stimulus‐triggered NO donors, fluorophore‐labeled NO donors. The field also sees a recent addition, i. e. photo‐triggered and photo‐calibrated NO donors, whose NO release is photo‐controlled and further accompanied by a fluorescence turn‐on as a built‐in calibration mechanism of NO release. This review provides an overview of the NO biochemistry, as a roadmap for the chemistry of NO donors. The design rationale and the release mechanism of different classes of NO donors were discussed. Some interesting and notable applications were briefly discussed, e. g. super‐resolution localization microscopic imaging of cell structures, and photo‐acoustic probes for disease diagnosis. With joint‐force, these NO donors constitutes a group of indispensable molecular tools of chemical biology and medicine in real applications. [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]

Fluorescence imaging using poly(phenylene ethynylene) (PPE) based conjugated polyelectrolytes (CPEs) has garnered considerable attention in the recent past due to their remarkable photophysical properties. In this report, we studied the fluorescence imaging properties of a set of six PPE‐based CPEs appended with side chains varying in structure and number of cationic charges. The photophysical and aggregation features of the CPEs depend on the overall charge density on the polymer in water. The cytotoxicity of the CPEs was evaluated against MCF‐7 mammalian cells, which revealed that polyelectrolytes with less cationic charge are less cytotoxic and vice versa. Confocal laser scanning microscopy (CLSM) studies showed that all the CPEs could efficiently penetrate into the MCF‐7 cells after 10 h of incubation. The transit of CPEs into the lysosomes was confirmed by comparison with the uptake of LysoTracker Red DND‐99 dye, which also revealed that the polyelectrolytes are highly photostable. We also demonstrated that the imidazolium‐functionalized CPEs could selectively stain bacteria over mammalian cells, suggesting the importance of CPEs for clinical applications. [ABSTRACT FROM AUTHOR]

In this article from Angewandte Chemie, researchers Seung Bum Park et al. discuss the development of a series of fluorogenic BODIPY-Tz probes for dual-color bioorthogonal imaging. The probes demonstrated excellent fluorescence enhancement in various wavelengths, including the far-red region, and showed BCN-selective behavior. The researchers also discovered the origin of this behavior and observed a unique fluorescence recovery in hydrophobic media. This breakthrough allows for dual-color bioorthogonal cellular imaging using a single probe. [Extracted from the article]

In the article "Inside Back Cover: Ultrafluorogenic Monochromophore-Type BODIPY-Tetrazine Series for Dual-Color Bioorthogonal Imaging with a Single Probe," the authors discuss the development of a series of fluorogenic BODIPY-Tz probes for dual-color bioorthogonal imaging. The probes demonstrated selective fluorescence enhancement in various wavelengths, including the far-red region, and allowed for dual-color bioorthogonal cellular imaging using a single probe. The authors also discovered the origin of the probes' selective behavior and observed a unique fluorescence recovery in hydrophobic media. This research opens up exciting possibilities for bioorthogonal imaging with improved efficiency and simplicity. [Extracted from the article]

A recent research article published in Angewandte Chemie by Rachel C. Evans et al. explores the use of ultra-small nanoparticle probes for anti-Stokes fluorescence lifetime imaging in living cells. The researchers designed these probes using triplet-triplet annihilation upconversion (TTA-UC) chromophores encapsulated in an organic-inorganic ureasil host. The study demonstrates that these nanoparticles can be used to map local oxygen diffusion across the subcellular structure, as evidenced by fluctuations in the upconversion lifetime in stained cells. The authors of the article include Bolong Zhang, Kieran D. Richards, Beatrice E. Jones, Abigail R. Collins, Rosie Sanders, Sarah R. Needham, Pu Qian, Amoghavarsha Mahadevegowda, Caterina Ducati, Stanley W. Botchway, and Rachel C. Evans. [Extracted from the article]

In a research article published in Angewandte Chemie International Edition, Rachel C. Evans et al. demonstrate the use of ultra-small nanoparticle probes for anti-Stokes fluorescence lifetime imaging in living cells. These probes are based on triplet-triplet annihilation upconversion (TTA-UC) chromophores encapsulated in an organic-inorganic ureasil host. The researchers found that the nanoparticles can be used to map local oxygen diffusion across the subcellular structure, as indicated by fluctuations in the upconversion lifetime in stained cells. The study provides valuable insights into the potential applications of these nanoparticles in imaging techniques. [Extracted from the article]

Fluorescent cyclic peptides are excellent chemical scaffolds to build optical agents for molecular imaging. In addition to their favorable physicochemical properties, they can be modified with multiple organic fluorophores and generate useful probes for biological assays targeting specific proteins, namely receptors or enzymes. In this article, we review recent advances in the synthetic approaches for the preparation of fluorescent cyclic peptides as well as some of their applications in biological imaging, from in vitro live‐cell imaging studies to in vivo characterization of preclinical models. [ABSTRACT FROM AUTHOR]

The design and synthesis of molecular receptors for the selective binding of nucleoside phosphate anions (e. g. ATP, ADP, GTP, GDP, UDP) in aqueous media at physiological pH is a valuable research endeavour, which could lead to new sensing tools for biomedical and drug discovery research. However, this target is very challenging due to similarities in anion size, structure and charge. This Minireview provides an account of the development of receptors capable of discriminating between ATP and ADP, and their utilisation in biological sensing applications. Particular focus is given to the application of receptors for the determination of ATP or ADP concentrations in biological media, tracking ATP levels (or the ATP/ADP ratio) in cells using fluorescence microscopy, or real‐time monitoring of enzyme reactions involving ATP and ADP in vitro. [ABSTRACT FROM AUTHOR]