Fluorescent Molecular Rotors for Viscosity Sensors

Fluorescence Probes Exhibit Photoinduced Structural Planarization: Sensing In Vitro and In Vivo Microscopic Dynamics of Viscosity Free from Polarity Interference

We demonstrate the construction of wavelength λ-ratiometric images that allow visualizing the distribution of microscopic dynamics within living cells and tissues by using the newly developed principle of fluorescence response. The bent-to-planar motion in the excited state of incorporated fluorescence probes leads to elongation of the π-delocalization, resulting in microviscosity-dependent but polarity-insensitive interplay between well-separated blue and red bands in emission spectra. This allows constructing the exceptionally contrasted images of cellular dynamics. Moreover, the application of probes with increased affinity toward biological membranes allowed detecting the differences in dynamics between the plasma membrane and intracellular membrane structures. Such λ-ratiometric microviscosity imaging was extended for mapping the living tissues and observing their inflammation-dependent changes.

A Review of the Real-Time Monitoring of Fluid-Properties in Tubular Architectures for Industrial Applications

The real-time monitoring of fluid properties in tubular systems, such as viscosity and flow rate, is essential for industries utilizing liquid mediums. Nowadays, most studies of the fluid characteristics are performed off-line using laboratory facilities that can provide accurate results, yet they do not match the demanded industrial pace. Off-line measurements are ineffective and time-consuming. The available real-time monitoring sensors for fluid properties are generally destructive methods that produce significant and persistent damage to the tubular systems during the installation process. Others use huge and bulky invasive instrument methods that generate considerable pressure reduction and energy loss in tubular systems. For these drawbacks, industries centered their attention on non-invasive and non-destructive testing (NDT) methodologies, which are installed on the outer tubular surface to avoid flow disturbance and desist shutting down systems for installations. Although these sensors showed excellent achievement for monitoring and inspecting pipe health conditions, the performance was not convincing for monitoring the properties of fluids. This review paper presents an overview of the real-time monitoring of fluid properties in tubular systems for industrial applications, particularly for pipe monitoring sensors, viscosity, and flow measurements. Additionally, the different available sensing mechanisms and their advantages, drawbacks, and potentials are discussed.

Of Twists and Curves: Electronics, Photophysics, and Upcoming Applications of Non-Planar Conjugated Organic Molecules

Non-planar conjugated organic molecules (NPCOMs) contain π-conjugation across their length and also exhibit asymmetry in their conformation. In other words, certain molecular fragments in NPCOMs are either twisted or curved out of planarity. This conformational asymmetry in NPCOMs leads to non-uniform charge-distribution across the molecule, with important photophysical and electronic consequences such as altered thermodynamic stability, chemical reactivity, as well as materials properties. Majorly, NPCOMs can be classified as having either Fused or Rotatable architectures. NPCOMs have been the focus of significant scientific attention in the recent past due to their exciting photophysical behavior that includes intramolecular charge-transfer (ICT), thermally activated delayed fluorescence (TADF) and long-lived charge-separated states. In addition, they also have many useful materials characteristics such as biradical character, semi-conductivity, dynamic conformations, and mechanochromism. As a result, rational design of NPCOMs and mapping their structure-property correlations has become imperative. Researchers have executed conformational changes in NPCOMs through a variety of external stimuli such as pH, temperature, anions-cations, solvent, electric potential, and mechanical force in order to tailor their photophysical, optoelectronic and magnetic properties. Converging to these points, this review highlights the lucrative electronic features, photophysical traits and upcoming applications of NPCOMs by a selective survey of the recent scientific literature.

Electrochemical Switching of a Fluorescent Molecular Rotor Embedded within a Bistable Rotaxane

We report how the nanoconfined environment, introduced by the mechanical bonds within an electrochemically switchable bistable [2]rotaxane, controls the rotation of a fluorescent molecular rotor, namely, an 8-phenyl-substituted boron dipyrromethene (BODIPY). The electrochemical switching of the bistable [2]rotaxane induces changes in the ground-state coconformation and in the corresponding excited-state properties of the BODIPY rotor. In the starting redox state, when no external potential is applied, the cyclobis(paraquat-p-phenylene) (CBPQT⁴⁺) ring component encircles the tetrathiafulvalene (TTF) unit on the dumbbell component, leaving the BODIPY rotor unhindered and exhibiting low fluorescence. Upon oxidation of the TTF unit to a TTF²⁺ dication, the CBPQT⁴⁺ ring is forced toward the molecular rotor, leading to an increased energy barrier for the excited state to rotate the rotor into the state with a high nonradiative rate constant, resulting in an overall 3.4-fold fluorescence enhancement. On the other hand, when the solvent polarity is high enough to stabilize the excited charge-transfer state between the BODIPY rotor and the CBPQT⁴⁺ ring, movement of the ring toward the BODIPY rotor produces an unexpectedly strong fluorescence signal decrease as the result of photoinduced electron transfer from the BODIPY rotor to the CBPQT⁴⁺ ring. The nanoconfinement effect introduced by mechanical bonding can effectively lead to modulation of the physicochemical properties as observed in this bistable [2]rotaxane. On account of the straightforward synthetic strategy and the facile modulation of switchable electrochromic behavior, our approach could pave the way for the development of new stimuli-responsive materials based on mechanically interlocked molecules for future electro-optical applications, such as sensors, molecular memories, and molecular logic gates.

2 + 2 Can Make Nearly a Thousand! Comparison of Di- and Tetra-Meso-Alkyl-Substituted Porphycenes

Two porphycenes, substituted at the meso positions with two and four methyl groups, respectively, reveal similar absorption spectra, but their photophysical properties are completely different. 9,20-dimethylporphycene emits fluorescence with about 20% quantum yield, independent of the solvent. In contrast, fluorescence of 9,10,19,20-tetramethylporphycene is extremely weak in nonviscous solvents, but it can be recovered by placing the chromophore in a rigid environment. We propose a model that explains these differences, based on calculations and structural analogies with other extremely weakly emitting derivatives, dibenzo[cde,mno]porphycenes. The efficient S₁ deactivation involves delocalization of two inner cavity protons coupled with proton translocation toward a high-energy cis tautomer. The latter process leads to distortion from planarity. The probability of deactivation increases with the strength of the intramolecular NH···N hydrogen bonds. The model also explains the observation of biexponential fluorescence decay in weakly emitting porphycenes. It can be extended to other derivatives, in particular, the asymmetrically substituted ones. We also point to the possibility of using specific porphycenes as viscosity sensors, in particular, when working in single molecule regime.

Luminescent Carbazole-Based EuIII and YbIII Complexes with a High Two-Photon Absorption Cross-Section Enable Viscosity Sensing in the Visible and Near IR with One- and Two-Photon Excitation

The newly synthesized Eu^III and Yb^III complexes with the new carbazole-based ligands CPAD^2- and CPAP^4- display the characteristic long-lived metal-centered emission upon one- and two-photon excitation. The Eu^III complexes show the expected narrow emission bands in the red region, with emission lifetimes between 0.382 and 1.464 ms and quantum yields between 2.7% and 35.8%, while the Yb^III complexes show the expected emission in the NIR region, with emission lifetimes between 0.52 and 37.86 μs and quantum yields between 0.028% and 1.12%. Two-photon absorption cross sections (σ_2PA) as high as 857 GM were measured for the two ligands. The complexes showed a strong dependence of the one- and two-photon sensitized emission intensity on solvent viscosity in the range of 0.5-200 cP in the visible and NIR region.

Two π-Electrons Make the Difference: From BODIPY to BODIIM Switchable Fluorescent Dyes

(aza-)BODIPY dyes (boron dipyrromethene dyes) are well-established fluorophores due to their large quantum yields, stability, and diversity, which led to promising applications including imaging techniques, sensors, organic (opto)electronic materials, or biomedical applications. Although the control of the optical properties in (aza-)BODIPY dyes by peripheral functional groups is well studied, we herein present a novel approach to modify the 12 π-electron core of the dipyrromethene scaffold. The replacement of two carbon atoms in the β-position of a BODIPY dye by two nitrogen atoms afforded a 14 π-electron system, which was termed BODIIM (boron diimidazolylmethene) in systematic analogy to the BODIPY dyes. Remarkably, the BODIIM dye was obtained with a BH2 -rigidifying entity, which is currently elusive and highly sought after for the BODIPY dye class. DFT-Calculations confirm the [12+2] π-electron relationship between BODIPY and BODIIM and reveal a strong shape correlation between LUMO in the BODIPY and the HOMO of the BODIIM. The modification of the π-system leads to a dramatic shift of the optical properties, of which the fluorescent emission is most noteworthy and occurs at much larger Stokes shift, that is, ≈500 cm-1 in BODIPY versus >4170 cm-1 in BODIIM system in all solvents investigated. Nucleophilic reactivity was found at the meso-carbon atom in the formation of stable borane adducts with a significant shift of the fluorescent emission, and this behavior contrasts the reactivity of conventional BODIPY systems. In addition, the reverse decomplexation of the borane adducts was demonstrated in reactions with a representative N-heterocyclic carbene to retain the strongly fluorescent BODIIM compound, which suggests applications as fully reversible fluorescent switch.

Mitochondria-targeted aggregation-induced emission active near infrared fluorescent probe for real-time imaging

Mitochondria are essential organelles in eukaryotic cells and act as the energy powerhouse and biosynthetic compartment. Fluorescent dyes are widely used powerful molecular tools for analytical sensing and optical imaging. Low photostability, short excitation and emission wavelengths, and aggregation-induced quenching effects restrict the application of traditional commercial mitochondrial fluorescent probes for bioimaging. In this study, using rhodamine as the acceptor and phenothiazine as the donor, we synthesized a novel mitochondrial-targeted near infrared (NIR) fluorescent probe, MIT-PZR. Due to low cytotoxicity, great photostability and high specificity for mitochondria targeting, MIT-PZR has enormous potential for cell imaging. Furthermore, with a sizeable Stokes shift (emission peak at 705 nm), MIT-PZR penetrated tissues providing stable red fluorescence for imaging in vivo. The histological assessment of various tissues after treatment with MIT-PZR indicated that it has good biocompatibility. Thus, MIT-PZR is a promising mitochondrial NIR fluorescent probe for future application in clinical diagnosis and modern biological research.

Multichromophoric COO-BODIPYs: an advantageous design for the development of energy transfer and electron transfer systems

Synthesis and photonics avails a new design for multichromophoric arrays.

A novel carbazolyl GFP chromophore analogue: synthesis strategy and acidic pH-activatable lysosomal probe for tracing endogenous viscosity changes

A novel, acidic pH-activatable carbazolyl GFP chromophore analogue was designed for tracing lysosomal viscosity changes.

Solvatochromic dual luminescence of Eu–Au dyads decorated with chromophore phosphines

Chromophore-containing phosphines produce highly solvatochromic gold(i) fluorophores. Their combination with red-emitting Eu centers offers a facile approach to dual emissive complexes with widely tunable luminescence characteristics.

Photophysical properties of some novel tetraphenylimidazole derived BODIPY based fluorescent molecular rotors

In this work, we present tetraphenylimidazole-based BODIPYs (HPIB1–HPIB4) as fluorescent molecular rotors exhibiting aggregation induced emission, solid state fluorescence and appreciable sensitivity towards viscosity.

The effect of solvent polarity and macromolecular crowding on the viscosity sensitivity of a molecular rotor BODIPY-C10

Viscosity is the key parameter of many biological systems such as live cells. It can be conveniently measured with ‘molecular rotors’ – fluorescent sensors of microviscosity. Here, we investigate one of the most applied molecular rotors BODIPY-C₁₀.

A biotin-guided fluorescent probe for dual-mode imaging of viscosity in cancerous cells and tumor tissues

A new tumor-targeted fluorescent viscosity probe Biotin-V was developed, which can be used for dual-mode imaging of viscosity in cancerous cells and tumor tissues.

Rational Design of Dual-State Emission Luminogens with Solvatochromism by Combining a Partially Shared Donor-Acceptor Pattern and Twisted Structures

We report a general design strategy for a new class of luminogens with dual-state emission (DSEgens) that are brightly emissive in both the solution and solid state, with solvatochromism properties, by constructing a partially shared donor-acceptor pattern based on a twisted molecule. The DSEgens with bright fluorescence emission in both the solid and solution state demonstrate a unique solvatochromism behaviour depending on solvent polarity and thus may have applications in anti-counterfeiting.

Systematic Modifications of a Simple Tolan: Another Category of Viscosity Sensor

The first tolan derivative-based viscosity sensor (5d) has been synthesized, and its fluorescence intensity and lifetime increase when the viscosity of the solvent increases in methanol-glycerol mixtures. Phthalide (5d) was selected among structurally diverse tolan derivatives through systematic modifications of a simple tolan. To test 5d as a viscosity sensor, fluorescence lifetime imaging (FLIM) images of HeLa cells were obtained upon treatment with 5 μM of 5d to map the viscosity of the HeLa cells.

Functionalized BODIPYs as Fluorescent Molecular Rotors for Viscosity Detection

Abnormal changes of intracellular microviscosity are associated with a series of pathologies and diseases. Therefore, monitoring viscosity at cellular and subcellular levels is important for pathological research. Fluorescent molecular rotors (FMRs) have recently been developed to detect viscosity through a linear correlation between fluorescence intensity or lifetime and viscosity. Recently, 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (boron dipyrrins or BODIPY) derivatives have been widely used to build FMRs for viscosity probes due to their high rotational ability of the rotor and potentially high brightness. In this minireview, functionalized BODIPYs as FMRs for viscosity detection were collected, analyzed and summarized.

Synthesis of Pyrrolo[2,3-c]isoquinolines via the Cycloaddition of Benzyne with Arylideneaminopyrroles: Photophysical and Crystallographic Study

An efficient and quick access toward a series of (E)-2-arylideneaminopyrroles 6 and to their benzyne-promoted aza-Diels-Alder cycloaddition products is provided. These products are three pyrrolo[2,3-c]isoquinolines 8a-c substituted in position 5 with different electron-acceptor (A) or electron-donor (D) aryl groups. Intermediates and products were obtained in good yields (up to 78 and 84%, respectively), and their structures were determined on the basis of NMR measurements and HRMS analysis. Photophysical properties of 8a-c were investigated, finding good Stokes shift in different solvents, but only the product 8c showed appreciable fluorescence intensity since its 5-aryl group (2,4-Cl2Ph) could favor the twisted intramolecular charge transfer effect. In addition, a riveting relationship between solvent viscosity and fluorescence intensity was found. Structures of 6 and 8 were studied and confirmed by single-crystal X-ray diffraction, observing that their electronic distributions effect the supramolecular assembly but with only long-distance hydrophobic interactions. A CE-B3LYP model was used to study the energetic topology and understand the crystal architecture of compounds as well as find a connection with both the synthetic and photophysical results.

Microfluidic Cytometry for High-Throughput Characterization of Single Cell Cytoplasmic Viscosity Using Crossing Constriction Channels

This article presents an approach of microfluidic flow cytometry capable of continuously characterizing cytoplasmic viscosities of single cells. The microfluidic system consists of a major constriction channel and a side constriction channel perpendicularly crossing each other. Cells are forced to rapidly travel through the major channel and are partially aspirated into the side channel when passing the channel junction. Numerical simulations were conducted to model the time dependence of the aspiration length into the side channel, which enables the measurement of cytoplasmic viscosity by fitting the model results to experimental data. As a demonstration for high-throughput measurement, the cytoplasmic viscosities of HL-60 cells that were native or treated by N-Formylmethionine-leucyl-phenylalanine (fMLP) were quantified with sample sizes as large as thousands of cells. Both the average and median cytoplasmic viscosities of native HL-60 cells were found to be about 10% smaller than those of fMLP-treated HL-60 cells, consistent with previous observations that fMLP treatment can increase the rigidity of white blood cells. Furthermore, the microfluidic system was used to process granulocytes from three donors (sample size >1,000 cells for each donor). The results revealed that the cytoplasmic viscosity of granulocytes from one donor was significantly higher than the other two, which may result from the fact that this donor just recovered from an inflammation. In summary, the developed microfluidic system can collect cytoplasmic viscosities from thousands of cells and may function as an enabling tool in the field of single-cell analysis. © 2019 International Society for Advancement of Cytometry.

Hydrazine-Selective Fluorescent Turn-On Probe Based on Ortho-Methoxy-Methyl-Ether (o-MOM) Assisted Retro-aza-Henry Type Reaction

Hydrazine (N₂H₄) is one of the most widely used industrial chemicals that can be utilized as a precursor of pesticides, pharmaceutics, and rocket propellant. Due to its biological and environmental toxicity with potential health risks, various sensing tools have been developed. Among them, fluorescence-based molecular sensing systems have been highlighted due to its simple-operation, high selectivity and sensitivity, and biocompatibility. In our recent report, we disclosed a ratiometric type fluorescent probe, called HyP-1, for the detection of hydrazine, which is based on ortho-methoxy-methyl-ether (o-MOM) moiety assisted hydrazone-formation of the donor (D)-acceptor (A) type naphthaldehyde backbone. As our follow-up research, we disclose a turn-on type fluorescent probe, named HyP-2, as the next-generation hydrazine probe. The sensing rational of HyP-2 is based on the o-MOM assisted retro-aza-Henry type reaction. The dicyanovinyl moiety, commonly known as a molecular rotor, causes significant emission quenching of a fluorescent platform in aqueous media, and its cleavage with hydrazone-formation, which induces a significant fluorescence enhancement. The high selectivity and sensitivity of HyP-2 shows practical explicabilities, including real-time paper strip assay, vapor test, soil analysis, and real water assay. We believe its successful demonstrations suggest further applications into a wide variety of fields.

Cell Fuelling and Metabolic Energy Conservation in Synthetic Cells

We are aiming for a blue print for synthesizing (moderately complex) subcellular systems from molecular components and ultimately for constructing life. However, without comprehensive instructions and design principles, we rely on simple reaction routes to operate the essential functions of life. The first forms of synthetic life will not make every building block for polymers de novo according to complex pathways, rather they will be fed with amino acids, fatty acids and nucleotides. Controlled energy supply is crucial for any synthetic cell, no matter how complex. Herein, we describe the simplest pathways for the efficient generation of ATP and electrochemical ion gradients. We have estimated the demand for ATP by polymer synthesis and maintenance processes in small cell-like systems, and we describe circuits to control the need for ATP. We also present fluorescence-based sensors for pH, ionic strength, excluded volume, ATP/ADP, and viscosity, which allow the major physicochemical conditions inside cells to be monitored and tuned.

Ladder-Type Dye with Large Transition Dipole Moment for Solvatochromism and Microphase Visualization

A large transition dipole moment is usually pursued by strategies of twisted intramolecular charge transfer (TICT) or planar intramolecular charge transfer (PICT) to obtain obvious Stokes shifts and dramatic color changes with tuning of polarities. However, both strategies have their drawbacks and suffer from fluorescence quenching in solid states. Herein, a ladder-type molecule ISOAA-H with an intramolecular hydrogen bond is designed, which undergoes intramolecular charge transfer and proton shift to harvest a large transition dipole moment under light irradiation. Thanks to its out-of-plane side chains, the intermolecular π-π stacking of backbones is prohibited and solid emission is generated. ISOAA-H exhibits outstanding solvatochromic behavior with polarity changes of solvents or polymer matrixes and is successfully used to detect the microphase separation of polymer blends. These results indicate that a strategy combining the advantages of TICT and PICT is established for environment-sensitive dyes used in both solution and solid state.

Sensing and imaging of mitochondrial viscosity in living cells using a red fluorescent probe with a long lifetime

A red fluorescent probe (Mito-V) with a long lifetime was designed to monitor viscosity changes with high selectivity and sensitivity. The fluorescence intensity and lifetime of Mito-V displayed a good relationship with the viscosity value, and Mito-V was successfully applied to sensing mitochondrial viscosity changes in living cells under different biological processes.

Viscosity-sensitive thiolated gold nanoclusters with diffusion-controlled emission for intracellular viscosity imaging

A unique diffusion-dependent emission phenomenon of gold nanoclusters was discovered, and can be regulated by the variation in viscosity and temperature. This specific property of gold nanoclusters was further used for viscosity monitoring in live cells, and the results demonstrated that gold nanoclusters are capable of real-time monitoring the abnormal viscosity change inside the cells.

Fluorescence Chemicals To Detect Insoluble and Soluble Amyloid-β Aggregates

Misfolded amyloid-β (Aβ) is the key biomarker of Alzheimer's disease (AD), and discoveries of fluorescence chemicals visualizing such Aβ aggregates in the brain have made major contributions in postmortem and antemortem diagnosis of the disorder. Insoluble senile plaques of Aβ in brain tissues are commonly stained with thioflavin and congo red dyes and observed through microscopy, while those in living patient brains are detected via radioisotope-labeled fluorescence chemicals for positron emission tomography. Clinical evidence strongly supports the view that plaques are well-associated with the onset but not with the progression of AD. Plaques could accumulate while cognitive functions of at-risk individuals are still intact, and thus, another biomarker is needed to monitor neurodegeneration. Soluble Aβ oligomers are considered to have strong correlation with neuronal loss and brain atrophy as they are the most neurotoxic forms of misfolded Aβ. However, oligomer-targeting probes encounter several major difficulties in development. There is a significant structural distinction between two Aβ species-plaques are β-sheet-rich while oligomers are unordered-and it is still difficult to isolate and stabilize the oligomeric forms of Aβ. Due to these challenges, soluble oligomer-detecting imaging probes are relatively rare compared to the plaque-targeting chemical probes. This Review describes biochemical and optical characteristics of up-to-date fluorescence chemicals targeting insoluble plaques and soluble oligomers of Aβ. We also highlight the contributions of Aβ fluorescence chemicals to the clinical diagnosis of AD and technical challenges in searching for enhanced imaging probes.

Nitration of Tyrosine Channels Photoenergy through a Conical Intersection in Water

Nitration of tyrosine occurs under oxidative stress in vivo. The product, 3-nitrotyrosine (3NY), has a dramatically decreased quantum yield and can be used as a molecular ruler. In this study, femtosecond transient absorption spectroscopy and quantum calculations were implemented to elucidate the photoinduced relaxation processes of anionic 3NY in water. Upon 400 nm excitation into an excited electronic state with notable charge-transfer (CT) character, a barrierless nitro-twisting motion rapidly (<100 fs) guides the chromophore into an adjacent twisted intramolecular CT state, therein reaching a sloped S₁/S₀ conical intersection on the ∼100 fs time scale. Once in the hot ground state, excess energy is further released through vibrational cooling with biexponential time constants of ∼140 and 680 fs in water. Nitro back-twisting occurs on longer time scales (∼1.1 and 9 ps in water), returning the system to original ground state. Systematic evaluations of excited-state potential energies of anionic 3NY were performed by density functional theory (DFT) and time-dependent DFT calculations, showing that intersystem crossing (ISC) from the first singlet state (S₁) to the first or second triplet state (T₁ or T₂) is unlikely. Inclusion of an explicit water molecule in calculations leads to improved mapping of the excited-state energy ordering of the second singlet state (S₂) and T₂, further diminishing ISC probability from S₁ and favoring an ultrafast internal conversion to S₀. These results provide deep insights into the highly efficient nonradiative decay of anionic 3NY in aqueous solution, with nitro-site-specific information that can help infer the characterization and potential optogenetic control of 3NY in protein environment.

Rational design of NIR fluorescence probes for sensitive detection of viscosity in living cells

Developing near-infrared (NIR) fluorescence probes for detection of intracellular viscosity is still sufficiently challenging. In this work, three kinds of D-A-D type naphthyl and 2,1,3‑benzoxadiazol hybrid NIR dyes functionalized with amino (NY1), N‑methylamino (NY2) and N,N‑dimethylamino (NY3) groups for intracellular micro-viscosity detection were designed and synthesized. All the probes exhibited very weak NIR emission in low viscosity environment and obvious fluorescence enhancement with the increased viscosity. Different substituent groups had a high impact on the photophysical properties and response sensitive of the probes to viscosity. The structure-property relationships were systematic investigated. The results showed that stronger electron-donating ability and larger steric effect of N,N‑dimethylamino led to a narrower energy gap and more sensitive to viscosity environment. Therefore, NY3 exhibited higher signal noise ratio for viscosity detection and was successfully applied for imaging the changes of intracellular micro-viscosity. This work provides an efficient way to design powerful NIR fluorescence probes for viscosity detection.

The Applicability of 2-amino-4,6-diphenyl-pyridine-3-carbonitrile Sensors for Monitoring Different Types of Photopolymerization Processes and Acceleration of Cationic and Free-Radical Photopolymerization Under Near UV Light

The performance of a series of 2-amino-4,6-diphenyl-pyridine-3-carbonitrile derivatives as fluorescent molecular sensors for monitoring photopolymerization processes of different monomers by the Fluorescence Probe Technique (FPT) was studied. It has been shown that the new derivatives are characterized by much higher sensitivity than the commercially available 7-diethylamino-4-methylcoumarin (Coumarin 1) and trans-2-(2',5'-dimethoxyphenyl)ethenyl-2,3,4, 5,6-pentafluorobenzene (25ST) probes. It has been discovered that the 2-amino-4,6-diphenyl-pyridine-3-carbonitrile derivatives accelerate the cationic photopolymerization process initiated with diphenyliodonium photoinitiators at the wavelength where the photoinitiator alone does not work. They are particularly efficient for the photoinitiation of cationic photopolymerization of an epoxide and vinyl monomers. Consequently, the application of the 2-amino-4,6-diphenyl-pyridine-3-carbonitrile derivatives in a dual role: (a) as fluorescent sensors for monitoring the free-radical, thiol-ene and cationic polymerization progress, and (b) as long-wavelength co-initiators for diphenyliodonium salts initiators, is proposed.

Characterization of cytoplasmic viscosity of hundreds of single tumour cells based on micropipette aspiration

Cytoplasmic viscosity (μ c) is a key biomechanical parameter for evaluating the status of cellular cytoskeletons. Previous studies focused on white blood cells, but the data of cytoplasmic viscosity for tumour cells were missing. Tumour cells (H1299, A549 and drug-treated H1299 with compromised cytoskeletons) were aspirated continuously through a micropipette at a pressure of -10 or -5 kPa where aspiration lengths as a function of time were obtained and translated to cytoplasmic viscosity based on a theoretical Newtonian fluid model. Quartile coefficients of dispersion were quantified to evaluate the distributions of cytoplasmic viscosity within the same cell type while neural network-based pattern recognitions were used to classify different cell types based on cytoplasmic viscosity. The single-cell cytoplasmic viscosity with three quartiles and the quartile coefficient of dispersion were quantified as 16.7 Pa s, 42.1 Pa s, 110.3 Pa s and 74% for H1299 cells at -10 kPa (n cell = 652); 144.8 Pa s, 489.8 Pa s, 1390.7 Pa s, and 81% for A549 cells at -10 kPa (n cell = 785); 7.1 Pa s, 13.7 Pa s, 31.5 Pa s, and 63% for CD-treated H1299 cells at -10 kPa (n cell = 651); and 16.9 Pa s, 48.2 Pa s, 150.2 Pa s, and 80% for H1299 cells at -5 kPa (n cell = 600), respectively. Neural network-based pattern recognition produced successful classification rates of 76.7% for H1299 versus A549, 67.0% for H1299 versus drug-treated H1299 and 50.3% for H1299 at -5 and -10 kPa. Variations of cytoplasmic viscosity were observed within the same cell type and among different cell types, suggesting the potential role of cytoplasmic viscosity in cell status evaluation and cell type classification.

A red-emissive mitochondrial probe for imaging of the viscosity in living cells

L can exclusively stain mitochondria and monitor the mitochondrial viscosity changes.

Solution versus solid-state dual emission of the Au(i)-alkynyl diphosphine complexes via modification of polyaromatic spacers

Single molecule luminophores capable of multiple emissions are essential for the development of new materials with unconventional photophysical behavior.

Photophysical investigation of two emissive nucleosides exhibiting gigantic stokes shifts

We present discovery of two highly emissive nucleoside analogs with gigantic Stokes shifts and use in silico methods for rationalizing their striking fluorescent properties.