Yellow Fluorescent Signals Research Articles

Effect of crosslinking density on the self-healing and self-reporting properties of epoxy anti-corrosion coatings

This work developed a novel coating with self-healing and self-reporting performance by embedding polyurethane/poly-(urea-formaldehyde) (PU/UF) microcapsules in a shape memory epoxy polymer. 2’7’-Dichlorofluorescein (DCF) and linseed oil were applied as the coloring agent and healing agent, respectively, which are encapsulated into the PU/UF microcapsules (DL@PU/UF microcapsules) via a facile one-step method. To adjust the shape memory effect and the self-reporting performance of epoxy system, two kinds of curing agents (D230 and D400) were reacted with bisphenol A diglycidyl ether epoxy monomer to design a series of coating samples, finally the optimal coating system was selected by three indexes including barrier performance, residual amino content and coating hardness. When the composite coating was damaged, DCF can flow out of the broken microcapsules and react with the residual amino groups in the epoxy coating matrix, which can be recognized red signals in natural light and yellow fluorescent signals under ultraviolet light irradiation. More importantly, the excellent self-reporting property of the coating can be achieved on various metal substrates that broaden the application range of the coating. As for self-healing performance, the damaged coating can be healed quickly due to the shape memory effect of the coating as well as the filling of linseed oil in the scratched region. The Rct value of the healed coating containing 6 % DL@PU/UF microcapsules after immersing in 3.5 wt% NaCl solution for 5 days was more than 3 times that of the scratched coating, and the Rc value was about 16 times that of the scratched coating, indicating its corrosion protection performance. The novel coting not only achieve timely self-reporting ability of color and fluorescence, but also rapidly repair the coating damage, which is essential to practical applications.

One-pot fabrication of aluminium ion anchoring boric acid-carbon dots hybrid system and its highly selective fluorescence sensing for fluorine ion in water environment

Fluorine is one of the essential trace elements for human body, which is essential for calcification process in living organisms. In the paper, a “off–on” fluorescence sensor for fluorine ion based on aluminium ion and boric acid codoped carbon dots was synthesized and characterized. According to fluorescence analysis, the water-soluble sensor exhibited highly selective and sensitive for fluorine ion. In sensing process, F- could bind to Al3+ after the addition of fluorine ion, which resulted in the decomposition of Al-BA-CDs system, then intense yellow fluorescence signal appeared. Moreover, the fluorescence sensor exhibited low detecting limit (5.0 nanomolar level) by fluorescence titration spectrum. In addition, according to evaluate the fluorescence sensing properties of F- in HepG2 cell and zebra fish, this job greatly extended the use of F- sensor from aluminium ion and boric acid codoped carbon dots in organism. The work also provided an interesting idea for fabricating water-soluble fluorescence sensor for F-.

Trident anchoring-lipid droplets strategy for fluorescence/super-resolution/lifetime imaging and diagnosis of fatty liver in vivo

Lipid droplets (LDs) are crucial dynamic organelles within cells that play an indispensable role in cellular energy supply, membrane formation, and signal transduction. Therefore, detecting and tracking LDs with high selectivity and resolution is particularly important. In this study, we describe a “trident” anchoring strategy (based on polarity, lipophilicity, and viscosity sensitivity) to achieve highly specific and dynamic imaging of LDs. A series of carbazole-substituted fluorescent protein (Car-FP) mimics conjugated with different electron-nature substituents (A–H) were synthesized and characterized. Spectroscopic properties indicate that the electron-donating triphenylamine (TPA)-conjugated H exhibits high sensitivity to polarity, viscosity response, and lipophilicity. Co-localization experiments in cells also demonstrate that H selectively localizes at LDs in living cells, displaying a bright yellow fluorescence signal (λex = 488 nm; λem = 577 nm) with a larger Stokes shift (89 nm) than the commercial LD dye bodipy 493/503 (10 nm). Super-resolution fluorescence imaging (SIM) and lifetime imaging (FLIM) are employed to visualize the distribution and aggregation in cell models of nonalcoholic fatty liver disease as well as zebrafish and mice models, demonstrating the potential applications of H in LD biology research and diagnosis of related diseases.

In Situ Optical Detection of Amines at a Parts-per-Quadrillion Level by Severing the Through-Space Conjugated Supramolecular Domino.

Conventional fluorophores suffer from low sensitivity and selectivity in amine detection due to the inherent limitations in their "one-to-one" stoichiometric sensing mechanism. Herein, we propose a "one-to-many" chain reaction-like sensing mechanism by creating a domino chain consisting of one fluorescent molecule (e.g., PTF1) and up to 40 nonemissive polymer chains (pPFPA) comprising over thousand repeating units (PFPA). PTF1 (the domino trigger) interacts with adjacent PFPA units (the following blocks) through polar-π interactions and initiates the domino effect, creating effective through-space conjugation along pPFPA chains and generating amplified yellow fluorescent signals through charge transfer between PTF1 and pPFPA. Amine exposure causes rapid dismantling of the fluorophore-pPFPA-based domino chain and significantly reduces the amplified emissions, thus providing an ultrasensitive method for detecting amines. Relying on the above merits, we achieve a limit of detection of 177 ppq (or 1.67 × 10-12 M) for triethylamine, which is nearly 4 orders lower than that of previous methods. Additionally, the distinct reactivity of pPFPA toward different amines allows for the discrimination of primary, secondary, and tertiary amines. This study presents a "domino effect" sensing mechanism that has not yet been reported and provides a general approach for chemical detection that is beyond the reach of conventional methods.

WO3 nanosheets with peroxidase-like activity and carbon dots based ratiometric fluorescent strategy for xanthine oxidase activity sensing and inhibitor screening

The abnormal level of xanthine oxidase (XOD) often causes pathological changes, which are related to a series of diseases. Herein, a novel and sensitive ratiometric fluorescent sensing platform based on WO3 nanosheets and carbon dots (CDs) was constructed to detect XOD activity for the first time. Under the catalytic oxidation of xanthine by XOD, hydrogen peroxide (H2O2) was generated. In the presence of H2O2, WO3 nanosheets were able to catalyze the oxidation of o-phenylenediamine to generate 2,3-diaminophenazine (DAP) with a yellow fluorescence signal at 570 nm due to its great peroxidase-like activity. The oxidation product DAP was capable of quenching the fluorescence of CDs at 430 nm through the inner filter effect. Therefore, the fluorescence intensity ratio F570/F430 can be used for quantitative analysis of XOD activity. This assay displayed good linear relationships in the range of 0.005–0.05 U/L and 0.5–40 U/L with a detection limit of 0.002 U/L. In addition, this ratiometric fluorescent sensing platform was successfully applied to the determination of XOD in human serum samples and XOD inhibitor screening, demonstrating significant potential in disease diagnosis and drug-screening applications.

Construction of a Label-Free Ratiometric Biosensor Based on Target Recycling Amplification and Hg-ZnSe QDs for Assay of BChE and OPs.

Herein, we constructed a label-free ratiometric fluorescence biosensing strategy for the determination of butyrylcholinesterase (BChE) activity and organophosphorus (OPs) concentration. BChE promoted the hydrolysis of iodized s-butyrylthiocholine (BTCh) into a reducing substance thiocholine, which can decompose CoOOH nanosheets (CoOOH NSs) to Co2+. Subsequently, the single-stranded DNA (ssDNA) on the surface of CoOOH NSs was released. Then, ssDNA hybridized with hairpin DNA (h-DNA) and triggered the target recycling amplification process, producing large amounts of G-quadruplex. After adding thioflavin T (ThT), the target BChE was converted into activatable G-quadruplex/ThT with an amplified yellow fluorescence signal. The addition of OPs could significantly inhibit the hydrolysis of BTCh by BChE and thus unable to produce the yellow fluorescence G-quadruplex/ThT complex. Throughout the entire process, the fluorescence intensity of Hg-ZnSe QDs as a reference signal remained unchanged at 630 nm. Furthermore, this work provided an effective approach for detecting the BChE activity in serum samples and OPs in fruits and vegetables.

Double-site-based a smart fluorescent sensor for logical detecting of sulphides and its imaging evaluation of living organisms

Thiophenol and hydrosulphite are a group of toxic environmental pollutants, which contaminate land, water and food exhibiting a serious risk to human health. Herein, we reported a xanthene dye-based sensor (DSF) with dual well-known response sites for visual detecting PhSH and HSO3-. Specifically, when DSF reacted with PhSH firstly, the color of the solution changed to blue with bright red fluorescence emission. After added with HSO3-, the color of the solution became yellow, and emitted yellow fluorescence signal. However, DSF was first added with HSO3-, the color of the solution changed to purple with no-fluorescence emission, and then PhSH was added, the color of the solution changed to yellow with a bright yellow fluorescence. Notably, DSF exhibited high sensitivity and selectivity for PhSH and HSO3- detection with a very low detection limits of 2.27 nM and 22.91 nM, respectively. More importantly, DSF could detect PhSH and HSO3- in water, real-food and biological systems. Therefore, the experimental results showed DSF as a robust new logical monitoring tool for the detection of PhSH and HSO3- in water, real-food samples and biological systems.

Facile construction of a reusable multi-enzyme cascade bioreactor for effective fluorescence discrimination and quantitation of amino acid enantiomers

Effective discrimination and quantitation of Amino acid (AA) enantiomers is enormously pivotal in diverse fields ranging from pharmaceutics to biological systems. We herein proposed a one-step strategy to construct a novel cascade bioreactor for chiral sensing of multiple AA enantiomers by coupling L-amino acid oxidase (LAAO) and Horseradish peroxidase (HRP) into zeolitic imidazolate framework-8 (ZIF-8) (LAAO/HRP@ZIF-8). LAAO specifically catalyzes L-AAs to α-keto acid, ammonium and H2O2, and then the yielded H2O2 oxidizes o-phenylenediamine (OPD) to strong yellow fluorescence signal of 2,3-diaminophenazine (DAP) by wrapped HRP. ZIF-8 not only guaranteed free enzymes stability owing to the steric confinement effect of the framework, but also reinforced multi-enzyme cascade catalytic activity due to a preconcentration effect of the analyte inside the cavities. In view of this, the fabricated chiral sensor allowed highly sensitive enantioselectivity discrimination a range of chiral AA enantiomers, especially tryptophan (Trp), valine (Val), methionine (Met), phenylalanine (Phe), isoleucine (Ile), leucine (Leu) and alanine (Ala). According to the linear correlation between the content of L-AAs and fluorescence intensity, this sensor achieved the quantitative determination of Enantiomeric excess (ee) value with high accuracy, and the results were well matched with those obtained by High performance liquid chromatography (HPLC). Additionally, the prominent stability and satisfactory reusability of this sensor were favorably elucidated by using Trp as the model molecule. Our work provides an unprecedented protocol for enantioselective fluorescence discrimination and quantitative determination of ee value for AA enantiomers, and immensely advances the promising application field of multi-enzyme@metal-organic framework biocomposites.

A ratiometric fluorescent assay for evaluation of alkaline phosphatase activity based on ionic liquid-functionalized carbon dots.

A ratiometric fluorescent assay is fabricated for the evaluation of alkaline phosphatase (ALP) activity. This assay is composed of ionic liquid-functionalized carbon dots (IL-CDs) with blue fluorescence signal at 470nm and 2,3-diaminophenazine (DAP) with yellow fluorescence signal at 570nm. IL-CDs were synthesized via electrochemical method by using ionic liquid (1-butyl-3-methylimidazolium tetrafluoroborate) and ultrapure water as precursors. DAP is produced by the oxidation reaction between o-phenylenediamine and H2O2 under the catalysis of horseradish peroxidase. H2O2 is reduced by ascorbic acid which is the hydrolysis product of ascorbic acid 2-phosphate under the catalysis of ALP, finally reducing the amount of DAP. The activity of ALP is evaluated through the ratiometric fluorescent signal between IL-CDs and DAP via Förster resonance energy transfer. Under optimal experimental conditions, this ratiometric fluorescent assay has a response that covers the 0.04 to 3.2UL-1 (12 to 960pM) ALP activity. This assay possesses ultralow detection limit of 0.012UL-1 (3.6pM) for ALP and high selectivity forALP among several enzymes. The method was used to measure ALP activity in human serum samples with satisfying results. Graphical abstract Schematic presentation of IL-CDs-based ratiometric fluorescent assay for ALP activity evaluation via FRET strategy between IL-CDs and DAP. This ratiometric fluorescent assay possessed low detection limit of ALP activity (0.012UL-1) and high selectivity among several enzymes.

A fluorescent turn-on probe based on isophorone for the rapid detection of alkaline phosphatase and its application in bioimaging.

Biological species analyses on account of fluorescence detection technology are receiving increasing attention, because they combine the advantages both powerful detection capability and excellent imaging technology. By effectively integrating isophorone and phosphate group via p-hydroxybenzaldehyde, the alkaline phosphatase (ALP) detection probe was obtained. Based on the enzyme-catalyzed dephosphorization course, phosphate group was separated from the probe by ALP and released yellow fluorescence signal. Upon addition with ALP, the probe exhibited high selectivity, short response time (6 min) and longer emission peak shift (570 nm). Furthermore, bioimaging experiment results indicated that the probe could detect endogenous ALP effectively.

Cytotaxonomical Study of the Chenopodium album and its Related Species in Korea

The purpose of this study was to analyze the interspecific relationships of Chenopodium album and its related taxa collected in Korea. The 18S-26S ribosomal DNA (45S rDNA) loci were detected directly on mitotic chromosomes by fluorescence in situ hybridization (FISH) and the chromosome numbers were examined using aceto-orcein methods. The chromosomal numbers of Chenopodium album var. album and C. album var. centrorubrum were 2n = 6x = 54, whereas for C. album var. stenophyllum, this number was 2n = 4x = 36. The basic chromosome number was x = 9. The biotin labeled 18S-26S rDNA probe exhibited eight yellow fluorescent signals on the metaphase chromosome of C. album var. album and var. centrorubrum respectively, while two yellow signals of C. album var. stenophyllum were noted. All of the signals on the chromosomes were located at the terminal regions. The chromosome number and FISH findings suggest that C. album var. centrorubrum is merged into var. album and that it is clearly distinguished from C. album var. stenophyllum.

Regulatory Roles of Heterogeneous Nuclear Ribonucleoprotein M and Nova-1 Protein in Alternative Splicing of Dopamine D2 Receptor Pre-mRNA

The dopamine D2 receptor (D2R) plays a crucial role in the regulation of diverse key physiological functions, including motor control, reward, learning, and memory. This receptor is present in vivo in two isoforms, D2L and D2S, generated from the same gene by alternative pre-mRNA splicing. Each isoform has a specific role in vivo, underlining the importance of a strict control of its synthesis, yet the molecular mechanism modulating alternative D2R pre-mRNA splicing has not been completely elucidated. Here, we identify heterogeneous nuclear ribonucleoprotein M (hnRNP M) as a key molecule controlling D2R splicing. We show that binding of hnRNP M to exon 6 inhibited the inclusion of this exon in the mRNA. Importantly, the splicing factor Nova-1 counteracted hnRNP M effects on D2R pre-mRNA splicing. Indeed, mutations of the putative Nova-1-binding site on exon 6 disrupted Nova-1 RNA assembly and diminished the inhibitory effect of Nova-1 on hnRNP M-dependent exon 6 exclusion. These results identify Nova-1 and hnRNP M as D2R pre-mRNA-binding proteins and show their antagonistic role in the alternative splicing of D2R pre-mRNA.

Identification of heterosomes in spermatoza of rams with 54,XX/54,XY chimerism

The aim of the study was to identify heterosomes in the semen of three Romanov rams – carriers of leukocyte chimerism (FISH technique) and to determine the proportions between spermatozoa with X and Y chromosomes. The choice of bovine probes for hybridization with ram heterosomes was dictated by genetic conservatism of bovine and ovine heterosomes. The ratio between spermatozoa with a yellow fluorescent signal containing the X chromosome in the haploid set and spermatozoa with a red-purple signal indicating the presence of the Y chromosome, taking into account spermatozoa with no signal, was 52%:43%:5% in ram No. PL100006077676; 47%:44%:9% in ram No. PL100006078031; and 48%:46%:6% in ram No. PL100006078895. The results obtained lead us to conclude that the 54,XX/54,XY chimerism has no effect on sex ratio in offspring.

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BioSpotlight

Rapid semi-quantitative fluorimetric determination of citrinin in fungal cultures isolated from cheese and cheese factories.

A new rapid semi-quantitative fluorimetric assay for citrinin production testing in mould cultures has been developed. The chemical structure of the citrinin makes it a weak native fluorophore. This fluorescence can be strongly enhanced in an acidic environment. A standard curve where the concentration of HCl needed to show the yellow fluorescence signal of different concentrations of citrinin was established, thus providing a semi-quantitative method to prove the capacity of toxin production of fungal cultures. Two Penicillium strains from the Spanish National Collection of Type Cultures, were studied for the toxin production on YES broth at 25 degrees C for 21 d. The culture was assayed daily for the presence/absence and quantification of citrinin by adding the HCl concentration set, and also quantified by RP-HPLC as a confirmation procedure. Experiments demonstrate that 5 d are necessary to show the presence of citrinin. As an illustration, a total of 48 strains of Penicillium isolated from cheese and cheese factories were analysed with the proposed method.

Fluorescentin situ hybridization to soybean metaphase chromosomes

Repetitive DNA sequences were detected directly on somatic metaphase chromosome spreads from soybean root tips using fluorescent in situ hybridization. Methods to spread the forty small metaphase chromosomes substantially free of cellular material were developed using protoplasts. The specific DNA probe was a 1.05 kb internal fragment of a soybean gene encoding the 18S ribosomal RNA subunit. Two methods of incorporating biotin residues into the probe were compared and detection was accomplished with fluorescein-labeled avidin. The rDNA probe exhibits distinct yellow fluorescent signals on only two of the forty metaphase chromosomes that have been counterstained with propidium iodide. This result agrees with our previous analyses of soybean pachytene chromosomes showing that only chromosome 13 is closely associated with the nucleolus organizer region. Fluorescent in situ hybridization with the rDNA probe was detected on three of the forty-one metaphase chromosomes in plants that are trisomic for chromosome 13.