Fluorophore Group Research Articles

Regularization of Parallel Factor Analysis (PARAFAC): A New Approach to Determining Groups of Fluorophores in Fluorescence Spectra of Natural Waters

Regularization of Parallel Factor Analysis (PARAFAC): A New Approach to Determining Groups of Fluorophores in Fluorescence Spectra of Natural Waters

Water-Soluble Bimodal Magnetic-Fluorescent Radical Dendrimers as Potential MRI-FI Imaging Probes.

Dual or multimodal imaging probes have become potent tools for enhancing detection sensitivity and accuracy in disease diagnosis. In this context, we present a bimodal imaging dendrimer-based structure that integrates magnetic and fluorescent imaging probes for potential applications in magnetic resonance imaging and fluorescence imaging. It stands out as one of the rare examples where bimodal imaging probes use organic radicals as the magnetic source, despite their tendency to entirely quench fluorophore fluorescence. Opting for organic radicals over metal-based contrast agents like gadolinium (Gd3+)-chelates is crucial to mitigate associated toxicity concerns. We utilized an amino-terminated polyamide dendrimer containing a 1,8-naphthalimide (Naft) fluorescent group, amino acid derivatives as linkers to enhance water solubility, and TEMPO organic radicals as terminal groups. The same dendrimer structure, featuring an equivalent number of branches but lacking the fluorophore group, was also functionalized with amino acid and terminal radicals to serve as a reference. Remarkably, we achieved a fully water-soluble dendrimer-based structure exhibiting both magnetic and fluorescent properties simultaneously. The fluorescence of the Naft group in the final structure is somewhat quenched by the organic radicals, likely due to photoinduced electron transfer with the nitroxyl radical acting as an electron acceptor, which has been supported by density functional theory calculations. Molecular dynamics simulations are employed to investigate how the dendrimers' structure influences the electron paramagnetic resonance characteristics, relaxivity, and fluorescence. In summary, despite the influence of the radicals-fluorophore interactions on fluorescence, this bimodal dendrimer demonstrates significant fluorescent properties and effective r1 relaxivity of 1.3 mM-1 s-1. These properties have proven effective in staining the live mesenchymal stem cells without affecting the cell nucleus.

Ultrasensitive and on-site diagnosis of rice bakanae disease based on CRISPR-LbCas12a coupled with LAMP.

Rice bakanae disease (RBD) has longstanding challenges impacted rice production, which is predominantly induced by Fusarium fujikuroi Nirenberg. Early diagnosis of F. fujikuroi is important to control RBD and improve quality and quantity of rice production. This study presents a novel on-site diagnosis platform combined with CRISPR/LbCas12a and LAMP to detect F. fujikuroi. LAMP amplification of TEF1-α, a characteristic gene of F. fujikuroi were performed, followed with trans-cleavage reaction of LbCas12a, cleaving the single-stranded DNA reporter, which is modified by the terminal fluorophore and quencher groups, producing fluorescence signal. The platform was confirmed with high specificity and sensitivity (LOD <1 aM). Furthermore, we designed a lateral flow strip experiment based on the trans-cleavage activity of LbCas12a, which was identified with similar sensitivity and specificity to the fluorescence detection method. In summary, this study achieved a platform with remarkable sensitivity and specificity for F. fujikuroi detection and provide potential for on-site and ultrasensitive diagnostic tools for RBD. © 2024 Society of Chemical Industry.

Nitroquinolone Fused Salicyl and Naphthyl Hydrazone Fluorescent Probes for the Detection of Fe3+and Pb2+ Ions.

The application of quinolones stretches over a large umbrella of medicinal field as well as chemosensor due to the presence of privileged heterocyclic aromatic rig system. Salicyl and Naphthyl Hydrazide motifs are also established fluorophore groups. Therefore in this work, we have designed and synthesized Salicyl hydrazide (3a-c) and naphthyl hydrazide fused nitroquinolones (5a-c) investigated for their fluorescent behaviour. Preliminary UV- absorption studies were carried out and the metal selectivity were examined with various metal ion. Among them, it was found that compound 3a was selective towards Fe3+ ions (λex = 330nm, 1:1 DMF:H2O at pH = 7.4 in HEPES Buffer medium). 3a shows decrease emission intensity in presence of Fe3+ ions. Compound 5a shows enhancement in fluorescence intensity upon addition of Pb2+ ion (λex = 280nm, 1:1 DMF:H2O at pH = 7.4 in HEPES Buffer medium). Further, the concentration dependence, competitive binding and EDTA reversibility were studied for selected compounds towards the respective cations selectivity. Jobs plot analysis indicate that 1:1 binding of 3a with Fe3+ ion (Ka = 3.17 x104M-1 and Limit Of Detection (LOD) = 5.1 × 10-7 M) whereas 5a showed 1:2 binding mode with Pb2+ ions (Ka = 2.14 × 106M-1 and Limit Of Detection (LOD) = 2.613 × 10-9M). Density Function Theoretical studies were performed as support for the experimental results.

1H, 1, 2, 3- Triazole Tethered imidazole-Isatin conjugates: Synthesis, DFT and optical properties

Novel functional materials, namely TPI-TAZ-ISA, NADPI-TAZ-ISA, ADPI-TAZ-ISA, and DMAPDPI-TAZ-ISA, were synthesized utilizing click chemical reactions and subjected to thorough characterization. The optical properties of these organic materials, TPI-TAZ-ISA, NADPI-TAZ-ISA, ADPI-TAZ-ISA, and DMAPDPI-TAZ-ISA, were investigated in various solvent environments. Notably, ADPI-TAZ-ISA exhibited a maximum absorption wavelength of 390 nm attributed to π – π* electronic transitions, primarily originating from the fluorophore group, while displaying a blue fluorescence at 465 nm. A comprehensive investigation combining experimental and theoretical approaches was conducted for these compounds, revealing a non-planar molecular structure and theoretical energy band gaps ranging from 4.10 to 4.73 eV. DFT studies demonstrated well-defined spatial separation of the HOMO and LUMO for all compounds in the ground state (S0). NTO studies further elucidated the spatial separation of the HONTO and LUNTO for DMAPDPI-TAZ-ISA at the excited state (S2), corroborated by CDD, hole and electron contributions, and the overlap of hole and electron densities. These findings hold promise for the development of novel luminescent materials. Moreover, on-going research is exploring the integration of ISA to enhance the functionality of these materials further.

Synthesis of an Amine Moiety‐Based Fluorescent Probe and the Relationship Between the Amino Substitution Position and Formaldehyde Detection Performance

AbstractA novel amine moiety‐based fluorescent probe (BA) was prepared using diphenylacetylene as fluorophore and amino group as acceptor. The probe achieves detection of formaldehyde through fluorescence enhancement by inhibition the photoinduced electron transfer (PET) between diphenylacetylene and amino group. And the different formaldehyde detection performance of 2‐(phenylethynyl)aniline (BA‐1), 3‐(phenylethynyl)aniline (BA‐2) and 4‐(phenylethynyl)aniline (BA‐3) indicates that the position of amino recognition group on the benzene ring of diphenylacetylene has a significant impact on the detection ability of this type fluorescent probe. When the amino group is in the ortho‐position of the benzene ring, probe BA‐1 can rapidly enhance the fluorescence intensity within 20 min with limit of detection as low as 0.75 μM; When the amino group is located in meta‐position of benzene ring, the solution of BA‐2 also exhibited a certain degree of fluorescence enhancement, but it is weaker than BA‐1; When the amino group is at the para‐position of benzene ring, BA‐3 has almost no response to formaldehyde.

Catalytic hairpin self-assembly amplification fluorescence detection of chloramphenicol based on cross-shaped DNA and UiO-66

A catalytic hairpin self-assembly (CHA) amplification method was developed for CAP detection based on cross-shaped DNA and UiO-66. MOF was used to quench the fluorescent signal of FAM labeled DNA. Cross-shaped DNA with four fluorophore group (FAM) was utilized to enhance the fluorescent intensity. CAP could open hairpin structure of H-apt and induce CHA reaction. The product of CHA hybridized with cross-shaped DNA, resulting its leaving from the surface of UiO-66 and recovery of fluorescent signal. The limit of detection (LOD) was low to 0.87 pM. This method had been successfully applied for the detection of CAP in actual samples. Importantly, the high sensitivity was attributed to the great amplification efficiency of CHA, strong fluorescent intensity of cross-shaped DNA structure and great fluorescent quenched efficiency of UiO-66.

Development of a Catalytic Hairpin Assembly-Based Fluorescent Assay for the Rapid Detection of SARS-CoV-2 Target RNA

To develop a catalytic hairpin assembly (CHA)-based fluorescent assay for the detection of the target RNA of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), so as to realize the rapid nucleic acid testing of SARS-CoV-2. A 24-nt segment of the SARS-CoV-2 nucleocapsid protein gene (N gene, NC_045512.2) was chosen as the target RNA and the hairpin motif 1 (H1) and hairpin motif 2 (H2) were designed based on the principle of CHA reaction. The H1 motif was labelled with a fluorophore group as well as a quencher group. When the target RNA was added to the hairpin motifs, CHA reaction was triggered at room temperature (25 ℃), which led to the amplification of fluorescence signal, thereby enabling the rapid detection of the target RNA. After the optimization of the hairpin motifs and the experimental conditions, the sensitivity and the specificity of the testing method were measured to evaluate its performance. We successfully constructed a CHA-based fluorescent assay specifically for the target RNA of SARS-CoV-2. With this method, testing could be completed at room temperature within 30 min. This testing method exhibited excellent specificity and could be used to accurately distinguish the perfectly-matched target RNA from the target RNA with single-base mutations. In addition, the testing method demonstrated good sensitivity, with a detection limit of 50 pmol/L. The proposed assay enables the simple and rapid detection of the SARS-CoV-2 target RNA with excellent sensitivity and specificity, showing great promise for further optimization and subsequent clinical application for the rapid detection of SARS-CoV-2 nucleic acid.

An ATMND/SGI based three-way junction ratiometric fluorescent probe for rapid and sensitive detection of bleomycin.

In this work, we developed a rapid and sensitive label-free ratiometric fluorescent (FL) probe for the detection of bleomycin (BLM). The probe consists of a DNA sequence (D6) and two fluorophore groups, 2-amino-5,6,7-trimethyl-1,8-naphthalene (ATMND) and SYBR Green I (SGI). The D6 sequence could be folded into a three-way junction structure containing a C-C mismatch position in the junction pocket. The unique "Y" structure not only could entrap ATMND in the mismatch pocket with high affinity, leading to FL quenching at 408 nm, but also embed SGI in the grooves of the double-stranded portion, resulting in FL enhancement at 530 nm. In the presence of BLM-Fe(II), the "Y" structure of D6 was destroyed due to the specific cleavage of the BLM recognition site, the 5'-GT-3' site in D6. This caused the release of ATMND and SGI and thus the ratiometric signal change of FL enhancement by ATMND and FL quenching by SGI. Under optimal conditions, the ratiometric probe exhibited a linear correlation between the intensity ratio of F408/F530 and the concentration of BLM in the range of 0.5-1000 nM, with a detection limit of 0.2 nM. In addition, the probe was applied to detect BLM in human serum samples with satisfactory results, indicating its good clinical application potential.

Azacoumarin-based "turn-on" fluorescent probe for the detection and imaging of hydrogen peroxide in living cells.

Azacoumarins are a relatively unexplored group of coumarin fluorophores, despite their excellent light-emitting properties. In this report, we detail the creation and production of a fluorescent probe (PYCB) based on azacoumarin for detecting H2O2. The probe utilizes a carboxy benzyl boronic pinacol ester as the recognition unit and displays a turn-on fluorescence response at 460 nm upon exposure to H2O2. The probe shows excellent sensitivity and selectivity to H2O2, with a detection limit of 0.385 μM. PYCB also exhibited strong pH stability and selectivity for H2O2 over other reactive oxygen species (ROS). Additionally, MTT assay results demonstrated the excellent biocompatibility of PYCB in MCF-7 cell lines. Fluorescence imaging of PYCB-treated MCF-7 cells revealed enhanced blue fluorescence corresponding to varying concentrations of exogenous H2O2.

Electronic relaxation pathways in thio-acridone and thio-coumarin: two heavy-atom-free photosensitizers absorbing visible light.

Heavy-atom-free photosensitizers (HAF-PSs) have emerged as a new class of photosensitizers aiming to broaden their applicability and versatility across various fields of the photodynamic therapy of cancers. The strategy involves replacing the exocyclic oxygen atoms of the carbonyl groups of established biocompatible organic fluorophores with sulfur, thereby bathochromically shifting their absorption spectra and enhancing their intersystem crossing efficiencies. Despite these advancements, the photophysical attributes and electronic relaxation mechanisms of many of these HAF-PSs remain inadequately elucidated. In this study, we investigate the excited state dynamics and photochemical properties of two promising HAF-PSs, thio-coumarin and thio-acridone. Employing a combination of steady-state and time-resolved techniques from femtoseconds to microseconds, coupled with quantum chemical calculations, we unravel the electronic relaxation mechanisms that give rise to the efficient population of long-lived and reactive triplet states in these HAF-PSs.

Installing hydrogen bonds as a general strategy to control viscosity sensitivity of molecular rotor fluorophores

AbstractMolecular rotor‐based fluorophores (RBFs) activate fluorescence upon increase of micro‐viscosity, thus bearing a broad application promise in many fields. However, it remains a challenge to control how fluorescence of RBFs responds to viscosity changes. Herein, we demonstrate that the formation and regulation of intramolecular hydrogen bonds in the excited state of RBFs could modulate their rotational barrier, leading to a rational control of how their fluorescence can be activated by micro‐viscosity. Based on this strategy, a series of RBFs were developed based on 4‐hydroxybenzylidene‐imidazolinone (HBI) that span a wide range of viscosity sensitivity. Combined with the AggTag method that we previously reported, the varying viscosity sensitivity and emission spectra of these probes enabled a dual‐color imaging strategy that detects both protein oligomers and aggregates during the multistep aggregation process of proteins in live cells. In summary, our work indicates that installing intracellular excited state hydrogen bonds to RBFs allows for a rational control of rotational barrier, thus allow for a fine tune of their viscosity sensitivity. Beyond RBFs, we envision similar strategies can be applied to control the fluorogenic behavior of a large group of fluorophores whose emission is dependent on excited state rotational motion, including aggregation‐induced emission fluorophores.

Fabrication of a GUMBOS-based ratiometric organo nanosensor for selective and sensitive detection of perchlorate ions that works in 100% water

This work intends to develop sensitive and easily applicable ionic liquids (ILs)-based fluorimetric sensors for detecting the explosive perchlorate (ClO4-) anions in the presence of other hazards and interferents. We have designed and developed an IL-compromising pyrene butyrate anion-based fluorophoric group of uniform materials based on organic salts (GUMBOS), PBIL, from sodium pyrene butyrate and trihexyltetradecylphosphonium chloride (P66614Cl) by simple ion exchange mechanism. Using reprecipitation methods, pyrene-based water-suspended nano-GUMBOS, nPBIL, has been fabricated and characterized by numerous analytical methods. The fabricated nano-GUMBOS display bright cyan color photoluminescence due to the excimer-like emission confirmed from the color chromaticity diagram. Interestingly, due to the addition of ClO4- ions, there is a blue shift in the UV–visible absorption spectrum of the nPBIL solution with a simultaneous decrease in Mie-scattering. Consequently, there is a continuous decrease in the excimer-like emission of nPBIL with the synchronized increase in monomeric emission. We can conclude from both UV–visible absorption and emission spectra that the ClO4- ion displaces the anionic pyrene butyrate moiety of our nPBIL due to its high polarizability. The limit of detection (LOD) of the as-fabricated sensor is estimated to be 7.17 nM which is very much lower than the US Environmental Protection Agency (USEPA) predicted permeable level of perchlorate in drinking water (15 μgL−1). An efficient test kit has been fabricated and demonstrated for on-site detection of ClO4- ions in remote areas. This ion exchange-mediated substance release from such nano-GUMBOS systems is a distinctive and innovative way to design and develop efficient sensors for precisely detecting and quantifying ClO4- ions.

An acidic medium‐compatible deep‐near‐infrared dye for in vivo imaging

AbstractIn vivo imaging in the deep near‐infrared (NIR) spectral region, that is, beyond 800 nm, has become popular due to its penetration depth. While imaging of the neutral medium/tissue has been repeatedly showcased, imaging of the high‐acidic medium remains challenging partly because of the high‐lying HOMO orbital and hence a high pKa of the electron‐donating group of the NIR fluorophores. We devised a novel electron‐donating group (D6) with which we further synthesized ECJ. ECJ exhibits an absorption wavelength beyond 900 nm and is fluorescent. Its pKa was found to be lower than zero, rendering it suitable for bioimaging of a highly‐acidic medium. Its potential for practical applications was showcased in proof‐of‐concept in vivo imaging with a mouse model.

A multi responsive phosphonic acid based fluorescent sensor for sensing Fe3+, benzaldehyde and antibiotics

Herein, we report a multi responsive and selective fluorescent chemo sensor with anthracene as a fluorophore and phosphonic acid group as receptor (anthracene-9,10-diylbis(methylene)) diphosphonic acid (ANDP) for detecting Fe3+, benzaldehyde and few antibiotics. The sensor was characterised by single crystal X-ray diffraction and 1H NMR. ANDP could selectively and sensitively detect Fe3+ and benzaldehyde in DMSO-water with the detection limits of 5.09 µM and 39.8 µM respectively. 1H NMR, FT-IR and Fluorescence life time measurements suggests the interaction of Fe3+ with the sensor and the oxygen of phosphonic acid group is responsible for the interaction in both the sensing of iron ion and benzaldehyde. Mainly nitro group based antibiotics (NFZ, MDZ, FZD) and TCL sensitively quenched the fluorescence of the sensor with the detection limit of 2.07 µM, 1.25 µM, 1.19 µM and 0.66 µM. The quenching mechanism was further discussed and it was found that the photo induced electron transfer (PET) was responsible for the quenching of fluorescence intensity of ANDP. The HOMO and LUMO energies were estimated by DFT calculations.

Visualizing Detection of Diabetic Liver Injury by a Biomarker-Activatable Probe via NIR-II Fluorescence Imaging.

Diabetes characterized by hyperglycemia is a chronic metabolic disease with increasing prevalence worldwide, and over time it leads to damage to various organs including the liver. As the liver is the major organ for glucose metabolism, patients with diabetes are prone to liver injuries or damages; and without timely and effective treatment, diabetic liver injury may further deteriorate into serious or life-threatening complications including liver cancer or liver failure. Hence, the accurate detection of diabetic liver injury is of great significance for diabetic patients in terms of improving quality of life. Herein, a fluorescent probe (TTX-P) has been developed for in situ detection and imaging of diabetic liver injury in the near-infrared second-window (NIR-II) region. In routine clinical practice, alkaline phosphatase (ALP) is one of the most commonly assayed enzymes, and thus serving as an important diagnostic biomarker for liver dysfunction or injury. The probe TTX-P responds in situ to the overexpressed ALP in liver and thus giving out strong NIR-II fluorescence as the reporting signals for detection and imaging. The NIR-II probe TTX-P consists of the NIR-II chromophore TTX-OH as the fluorophore and phosphate group as the responsive unit. Without the presence of ALP, the probe TTX-P displays weak fluorescence because the electron-withdrawing phosphate group weakens the electron-pushing capability of the electron-donor side of the NIR-II fluorophore. While in the presence of ALP, the phosphate group is cleaved by the enzyme and consequently the fluorophore emits evident NIR-II fluorescence. The probe TTX-P has been applied in imaging liver injury in diabetic mice. The approach provides a utilitarian means for visualizing detection of diabetic liver injury in mice with NIR-II fluorescence imaging.

Macrocyclic Compounds Comprising Tris(3-Aminopropyl)Amine Units and Fluorophore Moieties: Synthesis and Spectroscopic Studies in the Presence of Metal Salts

The synthesis of a variety of polyazamacrocyclic compounds comprising structural units of tris(3-aminopropyl)amine (TRPN) and oxadiamines, decorated with one or two fluorophore groups (dansyl or quinoline) at different nitrogen atoms, was carried out using Pd(0)-catalyzed amination. The dependence of the yields of the macrocycles on the synthetic path was observed. The spectrophotometric and fluorescent properties of the target compounds were studied, and their coordination with metal cations using UV–vis, fluorescence spectra as well as NMR titration was investigated. The stoichiometry and binding constants of several complexes with Cu(II), Zn(II), Cd(II), Pb(II) and Hg(II) were established. Three of the six studied macrocycles can be judged as prospective detectors of Zn(II) cations due to the substantial enhancement of fluorescence.

Research progress of auxiliary groups in improving the performance of fluorescent probes.

In the design work of fluorescent probes, it is important to consider not only the factors of fluorescence properties but also the environment in which the fluorescent molecule works. This requires the design of auxiliary groups to refine the fluorescent molecule. Nowadays, more and more fluorescent molecules are not limited to the traditional fluorescent probe consisting of a fluorophore, linker arm and recognition group, but integrate the three into one, and introduce auxiliary groups where possible. Auxiliary groups are "catalytic groups" that do not interact with the substrate, or "catalyze" the interaction of the recognition group with the substrate. The introduced auxiliary groups can improve the sensitivity and selectivity of the detection to some extent, which has attracted great interest from researchers. Although previous work has focused on this aspect, no one has summarized it systematically and comprehensively. So this review summarizes the role of auxiliary groups that are classified into three categories according to the different mechanisms between the auxiliary groups and the substance, in improving the performance of fluorescent probes in recent years (2012-2022). In particular, we generalize the mechanisms of the auxiliary groups in improving the sensitivity and selectivity of fluorescent probes. Also, the fundamental principles of auxiliary groups to improve the sensitivity and selectivity of fluorescent probes are discussed and future research directions in this field are proposed.

Fluorescence ‘‘turn-on’’ probe for the selective detection of water in organic solvents based on functionalized mesoporous silica

A fluorescence ‘‘turn-on’’ probe, namely, TTA-SBA-15, for the selective detection of water (H2O) was designed by grafting terthiophene fluorophore onto ethylenediamine functionalized mesoporous SBA-15 silica. The maximum fluorescence emission peak of TTA-SBA-15 ranged from 462 nm (toluene) to 525 nm (methanol) in various organic solvents. No fluorescence was observed in H2O due to the donor-excited photoinduced electron transfer mechanism, in which terthiophene acted as the donor and the amino group acted as the acceptor. Upon adding trace amounts of H2O into the TTA-SBA-15 suspensions dispersed in various organic solvents, TTA-SBA-15 was successfully applied as a ‘‘turn-on’’ fluorescent probe for the quantitative determination of trace H2O in organic solvents with high sensitivity and low detection limit. To demonstrate the selective detection mechanism of TTA-SBA-15 for H2O, the fluorescent spectra of two control materials (TT-SBA-15 and PyA-SBA-15) were also investigated in H2O and various organic solvents. The experimental results indicated that the terthiophene fluorophore and amine functional group on TTA-SBA-15 contributed to the H2O selectivity, highlighting the structure-activity relationships in developing organic functionalized mesoporous silica for potential applications.

FRET-FLIM to Determine Protein Interactions and Membrane Topology of Enzyme Complexes.

Determining protein-protein interactions is vital for gaining knowledge on cellular and metabolic processes including enzyme complexes and metabolons. Förster resonance energy transfer with fluorescence lifetime imaging microscopy (FRET-FLIM) is an advanced imaging methodology that allows for the quantitative detection of protein-protein interactions. In this method, proteins of interest for interaction studies are fused to different fluorophores such as enhanced green fluorescent protein (eGFP; donor molecule) and monomeric red fluorescent protein (mRFP; acceptor molecule). Energy transfer between the two fluorophore groups can only occur efficiently when the proteins of interest are in close physical proximity, around ≤10 nm, and therefore are most likely interacting. FRET-FLIM measures the decrease in excited-state lifetime of the donor fluorophore (eGFP) with and without the presence of the acceptor (mRFP) and can therefore give information on protein-protein interactions and the membrane topology of the tested protein. Here we describe the production of fluorescent protein fusions for FRET-FLIM analysis in tobacco leaf epidermal cells using Agrobacterium-mediated plant transformation and a FRET-FLIM data acquisition and analysis protocol in plant cells. These protocols are applicable and can be adapted for both membrane and soluble proteins in different cellular localizations. © 2022 The Authors. Current Protocols published by Wiley Periodicals LLC. Basic Protocol 1: Protein expression in tobacco leaf cells via transient Agrobacterium-mediated plant transformation Basic Protocol 2: FRET-FLIM data acquisition and analysis.