Pyrene Fluorophore Research Articles

Self-correcting ratiometric fluorescence assay for H2S detection in live cells and releasing agents

Hydrogen sulfide (H2S) is both a biologically significant signaling molecule, and a harmful gas that is generated in the environment; thus, its detection and monitoring are required in range of biological and environmental systems. Most fluorescent probes for H2S detection rely on single-detection fluorescence signals, making them vulnerable to interference from other species in complex microenvironment. In this study, we developed a ratiometric fluorogenic and colorimetric assay for H2S detection, in which pyrene and naphthalimide fluorophores operate together to provide a selective and sensitive detection system. Pyrene maintains fluorescence (always ‘On’), while naphthalimide exhibits an ‘On-Off’ response through thiolysis with H2S. By measuring the ratiometric fluorescence from these moieties, a self-calibrating response can be measured that is resistant to interference from other species in the microenvironments. The probe was used to measure H2S generation from H2S donor substrates and to monitor H2S fluctuations within living cells through selective, ratiometric fluorescence changes and real-time, dual-channel fluorescence imaging.

Optical Monitoring of Supramolecular Interactions in Polymers.

Many stimuli-responsive materials harness the reversible association of supramolecular binding motifs to enable advanced functionalities such as self-healing, switchable adhesion, or mechanical adaptation. Despite extensive research into the structure-property relationships of these materials, direct correlations between molecular-level changes in supramolecular binding and macroscopic material behaviors have mostly remained elusive. Here, we show that this challenge can be overcome with supramolecular binding motifs featuring integrated binding indicators. We demonstrate this using a novel motif that combines a hydrogen-bonding ureido-4-pyrimidinone (UPy) with two strategically placed pyrene fluorophores. Dimerization of this motif promotes pyrene excimer formation, facilitating the straightforward optical quantification of supramolecular assembly under various conditions. We exploit the new motif as a supramolecular cross-linker in poly(methyl acrylate)s to probe the extent of (dis)assembly as a function of cross-linker content, processing history, and applied stimuli. We demonstrate that the stimuli-induced dissociation of hydrogen-bonding linkages strongly depends on the initial cross-link density, which also dictates whether the force-induced dissociation in polymer films correlates with the applied stress or strain. Thus, beyond introducing a robust tool for the in situ study of dynamic (dis)assembly mechanisms in supramolecular systems, our findings provide new insights into the mechanoresponsive behavior of such materials.

Optical Monitoring of Supramolecular Interactions in Polymers

AbstractMany stimuli‐responsive materials harness the reversible association of supramolecular binding motifs to enable advanced functionalities such as self‐healing, switchable adhesion, or mechanical adaptation. Despite extensive research into the structure–property relationships of these materials, direct correlations between molecular‐level changes in supramolecular binding and macroscopic material behaviors have mostly remained elusive. Here, we show that this challenge can be overcome with supramolecular binding motifs featuring integrated binding indicators. We demonstrate this using a novel motif that combines a hydrogen‐bonding ureido‐4‐pyrimidinone (UPy) with two strategically placed pyrene fluorophores. Dimerization of this motif promotes pyrene excimer formation, facilitating the straightforward optical quantification of supramolecular assembly under various conditions. We exploit the new motif as a supramolecular cross‐linker in poly(methyl acrylate)s to probe the extent of (dis)assembly as a function of cross‐linker content, processing history, and applied stimuli. We demonstrate that the stimuli‐induced dissociation of hydrogen‐bonding linkages strongly depends on the initial cross‐link density, which also dictates whether the force‐induced dissociation in polymer films correlates with the applied stress or strain. Thus, beyond introducing a robust tool for the in situ study of dynamic (dis)assembly mechanisms in supramolecular systems, our findings provide new insights into the mechanoresponsive behavior of such materials.

A turn-on fluorescent probe based on pyrene for hydrazine detection

This paper presents a novel fluorescent probe (GNEM) based on a pyrene fluorophore, with dicarboximide as the recognition unit for hydrazine. The fluorescence probe can be synthesized in a simple one-step process. A highly selective and sensitive fluorescence turn-on GNEM synthesized. GNEM react with hydrazine through nucleophilic addition, leading to the deprotection of dicarboximide and the release of dicarboximide hydrazine, resulting in significant blue fluorescence. This enhanced emission is attributed to the intramolecular charge transfer (ICT) sensing mechanism of GNEM. In addition, detection of hydrazine in soil and water is conducted. By designing a simple detection device, the hydrazine content in the air can be quantitatively measured.

Bifunctional ratiometric fluorescent membrane containing pyrene-based probe for visual monitoring and efficient removal of Al3+

A bifunctional fluorescent pyrene-based probe, PYR, was designed by incorporating pyridine and phenolic hydroxyl moieties into pyrene fluorophore, which exhibited ratiometric fluorescent response toward Al3+. PYR underwent unique monomer-excimer conversion in ratiometric manner through the formation of a 2:1 coordination complex and accomplished with fluorescent color variation from green to blue. PYR displayed excellent selectivity, high sensitivity (LOD = 0.33 μM), rapid response (<45 s), and good cytocompatibility to Al3+. Notably, a fluorescent cellulose membrane decorated with PYR was successfully developed and applied for accurately quantify of Al3+ in diverse actual samples, and high-efficiency removal (∼96%) of Al3+ from water systems, with sustainable recycling performance up to 10 times. Bifunctional membranes also played an important role in reducing the LOD of Al3+ to 16 nM through the preconcentration process. Therefore, this study is crucial to the development of environmentally sustainable strategy for monitoring and removing pollution.

Ultrafast photoactivated nitric oxide release with a pyrene fluorescence probe

Nitric oxide (NO) plays important roles in both physiology and therapeutics. Nonetheless, the in-situ monitoring of NO release from most existing donors is challenging, inhibiting advanced research in both chemistry and biology. In this study, we introduce an innovative photochemotherapeutic agent that incorporates a nitroaniline NO moiety with an integrated pyrene fluorophore. This design enables controlled NO release upon light irradiation, allowing for precise quantification through a dramatic fluorescence enhancement (with a 3000-fold increase in intensity). Ultrafast spectroscopy data revealed that the NO release process is exceptionally rapid, completing within 13.3 ps. Additionally, the donor's fluorescence was successfully utilized for in situ cell imaging upon direct photoexcitation. Consequently, using this fluorescent probe enables the accurate visualization of NO release kinetics, dosage, and localization in real-time. The unique advantages of this NO donor are anticipated to significantly advance research in NO chemistry and biology.

Association between N-Terminal Pyrenes Stabilizes the Collagen Triple Helix.

Collagen model peptides featuring the fluorophore pyrene at their N-termini have been synthesized, and their thermal denaturation has been examined using circular dichroism (CD) and fluorescence spectroscopies. Flanking the (Pro-Hyp-Gly)7 core of the peptide monomers at positions 1 and/or 23 in the primary sequence, Lys residues were introduced to ensure water solubility. Triple helices derived from such peptides show a broad excimer emission at ∼480 nm, indicative of interaction between the pyrene units. CD experiments show that the fluorophores enhance helix stability primarily through entropic effects. Unfolding temperatures (Tm) increase by up to 7 °C for systems with N-terminal lysine residues and by up to 21 °C for systems in which the first-position Lys is replaced by Ala. Tm values derived from fluorescence measurements (at 50 μM) typically lie within ∼1 °C of those obtained using CD (at 200 μM). Computational modeling in a water continuum using B3LYP-GD3 and M06-2X functionals predicts that face-to-face association of fluorophores can occur while H-bonding within the [(POG)n]3 assembly is retained. Such parallel stacking is consistent with hydrophobically driven stabilization. Labeling collagen peptides with pyrene is a synthetically simple way to promote triple helicity while providing a means to obtain Tm data on relatively dilute samples.

Modulating Energy Transfer and Light-Emitting Colors by Chiral Dye Exchange and Achiral-to-Chiral Dye Conversion.

New chiral and achiral dyes were synthesized by using clean, highly efficient Diels-Alder 'click' reactions. We prepared pure endo- and exo- stereoisomers and blue-light-emitting single crystal of an exo-isomer. 1 H NMR spectroscopy and single-crystal X-ray diffraction reveal the precise spatial configurations of endo- and exo-dye stereoisomers. Single-crystal X-ray diffraction results reveal the dynamic nature of Diels-Alder covalent bonds. By reversible formation and cleavage of dynamic covalent bonds, an achiral dye was converted to a chiral dye, where achiral dansyl dye moiety was replaced by chiral moiety. Before achiral-to-chiral dye conversion, the dye system displayed dansyl acceptor green light-emitting color due to intramolecular fluorescence resonance energy transfer, where the blue emission of pyrene donor fluorophore was not observed. After achiral-to-chiral dye conversion, light-emitting colors of dye system change from green to blue, where the pyrene-to-dansyl fluorophore energy transfer was suppressed, and pyrene fluorophore blue emission was restored. Chiral transfer occurs in a chiral dye solid from non-chromophore alky chirality to pyrene chromophore. Thus, the chiral dye solid displayed chiral optical behaviors, i. e., circular dichroism and circularly polarized luminescence.

Pyrene or dansyl fluorophore functionalized polycarbazoles assembled through a “Click” approach: Synthesis, spectral, electrochemical, and optoelectronic properties

In the present study, new multifunctional carbazole derivatives consisting of pyrene (PrCz) or dansyl (DnCz) moieties were synthesized using a click chemistry approach and characterized via FT-IR, 1H NMR, UV-Vis, and fluorescence spectroscopy techniques. After electropolymerization of the monomers on the ITO glass surface using the cyclic voltammetry technique, optical and electrochemical characteristics of the conducting polymers P(PrCz) and P(DnCz) were investigated. Spectroelectrochemical measurements were carried out to determine the colors, switching time, and optical contrast of P(PrCz) and P(DnCz) polymer films. Both polymer films exhibited transparent to green electrochromic behavior, with similar optical band gaps. However, P(DnCz) film has higher optical contrast value and faster response time compared with the P(PrCz). When surface morphologies of the polymers were investigated by SEM analysis, it was observed that surface of the P(DnCz) film consists of many spherical clusters on a rough structure.

Unprecedented formation of bis-calix[5]phyrins centrally linked with pyrene subunits

A [3+2] acid-catalyzed condensation of a tetra-functionalized pyrene fluorophore (4) with dipyrromethane dicarbinol (5) resulted in the unprecedented formation of two bis-calix[5]phyrins (bis-calix[5]-1 and bis-calix[5]-2). The solution state structure of both bis-calix[5]phyrins was found to be similar with slight variations as confirmed by NMR spectral studies. Interestingly, two different linkages between the pyrene subunits with dipyrromethane dicarbinols led to two different calix[5]phyrin systems. Although the optical features seem to be similar, the single crystal X-ray structure obtained for bis-calix[5]-1 provided the structural proof showing a non-planar, half-chair conformation with two meso-sp3 carbons. DFT studies were carried out to compare the HOMO-LUMO energy levels of both bis-calix[5]phyrins with the targetted conjugated bis-macrocycle (bis-N[Formula: see text]. Further, both the calix[5]-phyrins showed high Stokes shift (5404 cm[Formula: see text] and fluorescence quantum yield efficiency of around 90%.

β-Cyclodextrin Polymer-Based Fluorescence Enhancement Strategy via Host-Guest Interaction for Sensitive Assay of SARS-CoV-2.

Nucleocapsid protein (N protein) is an appropriate target for early determination of viral antigen-based severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). We have found that β-cyclodextrin polymer (β-CDP) has shown a significant fluorescence enhancement effect for fluorophore pyrene via host-guest interaction. Herein, we developed a sensitive and selective N protein-sensing method that combined the host-guest interaction fluorescence enhancement strategy with high recognition of aptamer. The DNA aptamer of N protein modified with pyrene at its 3' terminal was designed as the sensing probe. The added exonuclease I (Exo I) could digest the probe, and the obtained free pyrene as a guest could easily enter into the hydrophobic cavity of host β-CDP, thus inducing outstanding luminescent enhancement. While in the presence of N protein, the probe could combine with it to form a complex owing to the high affinity between the aptamer and the target, which prevented the digestion of Exo I. The steric hindrance of the complex prevented pyrene from entering the cavity of β-CDP, resulting in a tiny fluorescence change. N protein has been selectively analyzed with a low detection limit (11.27 nM) through the detection of the fluorescence intensity. Moreover, the sensing of spiked N protein from human serum and throat swabs samples of three volunteers has been achieved. These results indicated that our proposed method has broad application prospects for early diagnosis of coronavirus disease 2019.

Glucose-triggered self-assembly of peptide-based fluorescent probes for highly selective ratiometric detection of D-Glucose in aqueous solution at physiological pH and biological fluids

D-Glucose (Glu) is the principal source of energy production for important organs in human beings. We have first developed a monoboronic acid-based fluorescent sensor (1) for highly selective ratiometric detection of Glu among hexose in aqueous solution at physiological pH. The peptide-based probe bearing a pyrene fluorophore and a phenylboronic acid showed remarkable sensing ability for Glu such as high sensitivity for Glu, high enhancement (70-fold) of the excimer emissions, low detection limit (3.1 µM), fast response (< 10 mins), and high-water solubility. The fluorescent study of peptide-based probes (1−5) suggested that the amphiphilic peptide moiety consisting of the positively charged amino acid (Arg and Lys) and hydrophobic Trp residue played a critical role for the ratiometric response toward Glu. The binding mode study of 1 indicated that the probe formed a 2:1 complex with Glu and then the complexes self-assembled, resulting in significant enhancement of excimer emission, whereas the probe formed a 1:1 complex with Fru that did not assemble, resulting in no considerable fluorescent changes. We demonstrated that Glu induced the formation of nanoparticles and supramolecular gels of 1 depending on the concentration of the probe and Glu. 1 could quantify Glu in real urine and human serum samples by ratiometric response. This was the first example of self-assembling peptide-based probe triggered by Glu for fluorescent detection of Glu and hydrogel formation. Glu-triggered self-assembly of the peptide-based probes could be applied not only for novel sensing systems but also for the development of drug delivery and regenerative medicine.

Observation of strong electron-phonon interaction in polymeric diluted organic semiconductor

Incorporating organic semiconductors in insulating polymer films, creating the so‐called diluted organic semiconductors, has been successfully used in different optoelectronic devices, including organic light-emitting diodes. However, the fundamental understanding of their excited state dynamics and spin physics remains elusive. Here, we present the temperature-dependent photoluminescence (PL) and transient absorption study of a model fluorescent organic dilute semiconductor where organic fluorophore pyrene is incorporated in the insulating Poly-methyl methacrylate (PMMA) polymeric backbone as pendant unit (py-PMMA). We observe that by lowering the temperature from 300 K to 140 K, the monomer fluorescence emission from py-PMMA gets blue-shifted, and their intensity enhances, which is attributed to less charge carrier scattering lattice sites at low temperature. Interestingly, we observe additional higher energy peaks at 368 nm (∼3.36 eV) below 70 K in fluorescence emission, explained by the exciton-phonon coupling. The exciton-phonon interaction constant (γph) is determined as 168 µeV/K, higher than other reported systems. The transient absorption measurement reveals the hot band relaxation (τ1 = 1.9 ps) and exciton- acoustic phonon interaction (τ2 = 27.2 ps) dominating in the excited state. Our study establishes that the electron–phonon interaction can play significant role in determining the optoelectronic properties of the fluorescent dilute organic semiconductor.

Design of an HPPD fluorescent probe and visualization of plant responses to abiotic stress

The upregulation of 4-hydroxyphenylpyruvate dioxygenase (HPPD) can protect plants from adverse abiotic stress. Therefore, studying the changes of HPPD under abiotic stress is extremely valuable. In this study, we employed a rational molecular design strategy to prepare an HPPD-responsive fluorescent probe consisting of a pyrene fluorophore, a linker and a benquitrione skeleton recognition moiety that functions via an aggregation–disaggregation sensing mechanism. As predicted, this probe exhibited an obvious turn-on fluorescence response towards HPPD. In addition, in vivo imaging demonstrated the excellent capability of this probe to track HPPD in Arabidopsis thaliana, and the dynamic changes in HPPD were monitored under different stress degrees of high temperature and Cadmium (II) ion (Cd2+) stress. This work provides an efficient design strategy for acquiring a noninvasive HPPD fluorescence probe, which could evaluate the degree of stress and be further employed for exploring the stress resistance mechanism in plants.

Quantitative Fluorescent Detection of Antibacterial Activity with Pyrene-Bearing Tannic Acid

Abstract Quantitative evaluation of the antibacterial activity of conventional antibacterial agents in situ is difficult. In this study, we demonstrated that antibacterial activity can be quantitatively estimated from the photoluminescence intensity of pyrene fluorophores incorporated into tannic acid, a naturally occurring antibacterial agent.

Fluorescence Quenching by Redox Molecular Pumping

Artificial molecular pumps (AMPs), inspired by the active cellular transport exhibited in biological systems, enable cargoes to undergo unidirectional motion, courtesy of molecular ratchet mechanisms in the presence of energy sources. Significant progress has been achieved, using alternatively radical interactions and Coulombic repulsive forces to create working AMPs. In an attempt to widen the range of these AMPs, we have explored the effect of molecular pumping on the photophysical properties of a collecting chain on a dumbbell incorporating a centrally located pyrene fluorophore and two terminal pumping cassettes. The AMP discussed here sequesters two tetracationic cyclophanes from the solution, generating a [3]rotaxane in which the fluorescence of the dumbbell is quenched. The research reported in this Article demonstrates that the use of pumping cassettes allows us to generate the [3]rotaxane in which the photophysical properties of fluorophores can be modified in a manner that cannot be achieved with a mixture of the dumbbell and ring components of the rotaxane on account of their weak binding in solution.

Pyrene-Functionalized Fluorescent Nanojars: Synthesis, Mass Spectrometric, and Photophysical Studies.

Nanojars are a class of supramolecular coordination complexes based on pyrazolate, Cu2+, and OH– ions that self-assemble around highly hydrophilic anions and serve as efficient anion binding and extraction agents. In this work, the synthesis, characterization, and photophysical properties of pyrene-functionalized fluorescent nanojars are presented. Three pyrene derivatives, 4-(pyren-1-yl)pyrazole (HL1), 4-(5-(pyren-1-yl)pent-4-yn-1-yl)pyrazole (HL2), and 4-(3-(pyrazol-4-yl)propyl)-1-(pyren-1-yl)-1,2,3-triazole (HL3), and the corresponding nanojars were synthesized and characterized using nuclear magnetic resonance spectroscopy and mass spectrometry. Electronic absorption, steady-state, and time-resolved fluorescence measurements were carried out to understand the interaction between the pyrene fluorophore and copper nanojars. Optical absorption measurements have shown minor ground state interaction between the fluorophore and nanojars. The fluorescence of pyrene is significantly quenched when attached to nanojars, suggesting strong contribution from the paramagnetic Cu2+ ions. Significant static quenching is observed in the case of L1, when pyrene is directly bound to the nanojar, whereas in the case of L2 and L3, when pyrene is attached to the nanojars using flexible tethers, both static and dynamic quenching are observed.

Construction of Magneto‐Fluorescent Bifunctional Spin‐Crossover Fe(II) Complex from Pyrene‐Decorated Pybox Ligand

AbstractThe construction of magneto‐fluorescent bifunctional complexes is a feasible approach toward multifunctional molecular materials. Herein we report the synthesis and properties studies of a mononuclear Fe(II) complex [FeL2](ClO4) (1), where L is a pyridine‐2,6‐bis(oxazoline) (pybox) ligand decorated by the pyrene fluorophore. Magnetic susceptibility measurement of desolvated complex 1‐d shows an incomplete and gradual spin‐crossover in the temperature range 50–300 K, which is further confirmed via 57Fe Mössbauer spectroscopy study. Light‐induced excited spin state trapping (LIESST) is also observed below 70 K when the powder sample is irradiated by a 532 nm laser. The change in absorption during the spin‐crossover (SCO) process is investigated via the temperature‐dependent UV‐vis spectroscopy. As expected, through introducing the chromophore, 1 displays fluorescence in both solution and solid state, achieving the coexistence of spin‐crossover and fluorescence in one compound.

Polydopamine loaded fluorescent nanocellulose–agarose hydrogel: A pH-responsive drug delivery carrier for cancer therapy

Herein, PDA-Py–CNC–AG composite hydrogel was developed by agarose, polydopamine and pyrene fluorophore labeled nanocellulose through interpenetrating polymer network strategy, which exhibited both fluorescent characteristics and pH responsive properties. Moreover, the adhesion to cells and controlled release performance to drug of the developed hydrogel was enhanced by the incorporation of polydopamine. As compared with single network hydrogel, the composite hydrogel yield a drug release up to 86.3% through a sustained drug release for 8 days at pH 5.5, the cytotoxicity was also enhanced obviously. More significantly, the fluorescent chromophore, pyrene was covalently linked to the amino group of amino-derivative nanocellulose, thereby providing attractive fluorescence properties to the synthesized hydrogel. Therefore, this composite hydrogel with multifunctional properties provides enhanced ability to cope with complexed tumor microenvironment and other challenging applications.

Rapid and sensitive fluorescence sensing detection of nitroaromatic compounds in water samples based on pyrene functionalized nanofibers mat prepared via green approach

Pyrene functionalized polyacrylonitrile nanofibers mat (Py-PAN NFM) was prepared via a green approach based on deep eutectic solvents. The Py-PAN NFM was further employed as solid-state fluorescent sensors for determining 2,4,6-trinitrotoluene (TNT) and 2,4-dinitrotoluene (DNT) in real water samples. In order to adapt to the hydrophobicity of Py-PAN NFM surface, the water samples were extracted by dichloromethane, and then the extraction solvents were directly dropped onto the Py-PAN NFM. The conversion of sample polarity ensures that Py-PAN NFM does not need to be immersed in the water samples for a long time. The target TNT and DNT can immediately interact with the pyrene fluorophores on surface of Py-PAN NFM, thus accelerating the detection speed. Because the targets were also enriched through the conversion process, the sensing sensitivity has been significantly improved and the limits of detection of TNT and DNT can reach 8.81 × 10−9 M and 2.74 × 10−8 M, respectively. The Stern–Volmer plots for fluorescence quenching by TNT and DNT displayed an overall linearity in the entire tested concentration range with quenching constants of 2.57 × 106 M−1 and 3.15 × 105 M−1, respectively. Moreover, the selectivity study indicated that other nitro compounds have an insignificant effect on the fluorescence sensing detection of TNT and DNT, and Py-PAN NFM can be reused at least 6 times without degradation in fluorescence-quenching performance. The theoretical calculations demonstrated that photoinduced electron transfer was involved in the quenching process and the fluorescence lifetime measurements revealed that a static quenching mechanism was suitable to explain the quenching behavior. The experimental results fully proved the practicability of this method in the rapid and sensitive monitoring of nitroaromatic compounds.