Conventional Fluorescent Dyes Research Articles

Carbon quantum dots for the diagnosis and treatment of ophthalmic diseases.

Carbon quantum dots (CQDs), an emerging nanomaterial, are gaining attention in ophthalmological applications due to their distinctive physical, chemical, and biological characteristics. For example, their inherent fluorescent capabilities offer a novel and promising alternative to conventional fluorescent dyes for ocular disease diagnostics. Furthermore, because of the excellent biocompatibility and minimal cytotoxicity, CQDs are well-suited for therapeutic applications. In addition, functionalized CQDs can effectively deliver drugs to the posterior part of the eyeball to inhibit neovascularization. This review details the use of CQDs in the management of ophthalmic diseases, including various retinal diseases, and ocular infections. While still in its initial phases within ophthalmology, the significant potential of CQDs for diagnosing and treating eye conditions is evident.

Exploring luminescent carbon dots derived from syrup bottle waste and curcumin for potential antimicrobial and bioimaging applications

In this study, we utilized a navel hybrid material, prepared by fusing fluorescent Carbon Dots SyCDs, derived from syrup bottles, with curcumin. This innovative approach not only offers significant advancements in antimicrobial activity and bioimaging but also represents a stride in sustainable and eco-friendly nanotechnology. The core of our study is the development of an efficient, cost-effective, and environmentally conscious method for synthesizing SyCDs. This is achieved by repurposing waste syrup bottles, thus addressing the pressing issue of plastic waste. The incorporation of curcumin, renowned for its biological properties, enhances the luminescent characteristics of SyCDs and augments their functionality. This combination overcomes the inherent limitations of curcumin when used in isolation. The hybrid material exhibits enhanced antimicrobial properties and proves to be a potent alternative to conventional fluorescent dyes for bioimaging, marking a substantial leap in the field of sustainable nanomaterials. Our work not only demonstrates the versatile applications of luminescent SyCDs in health and environmental science but also underscores the potential of sustainable approaches in addressing global environmental challenges. This study, represents a significant contribution to the domain of sustainable nanotechnology, highlighting the transformative power of integrating waste management with advanced material science.

Fluorescent Nanodiamonds for Tracking Single Polymer Particles in Cells and Tissues.

Polymer nanoparticles are widely used in drug delivery and are also a potential concern due to the increased burden of nano- or microplastics in the environment. In order to use polymer nanoparticles safely and understand their mechanism of action, it is useful to know where within cells and tissues they end up. To this end, we labeled polymer nanoparticles with nanodiamond particles. More specifically, we have embedded nanodiamond particles in the polymer particles and characterized the composites. Compared to conventional fluorescent dyes, these labels have the advantage that nanodiamonds do not bleach or blink, thus allowing long-term imaging and tracking of polymer particles. We have demonstrated this principle both in cells and entire liver tissues.

Sustainable fluorescent dye-faujasite zeolite systems as tools for cancer bioimaging

The use of fluorescent nanoparticles for biological and medical applications has attracted great attention due to their several advantages compared to conventional fluorescent dyes. However, there is also a need for sustainable and versatile alternatives, alongside the streamlining of complex synthesis or preparations. In this work, we study the potential of the faujasite zeolite structure to encapsulate dye molecules and be applied as a bioimaging agent for cancer cells. The commercial zeolites NaY, USY, and NaX were used to encapsulate Rhodamine B (RhB) or Fluorescein (F) dyes, which present a similar tetracycle core structure. Different characterization techniques confirmed the encapsulation of the dyes and their stability. The photophysical characterization of the encapsulated RhB and F dyes was also elucidated by UV–visible and fluorescence spectroscopy. Biocompatibility was tested in different cancer cell lines and confocal laser scanning electron microscopy (CLSM) was used to track the fluorescent dye-containing zeolites. Remarkably, the dye-containing zeolite RhB@USY showed interesting multiluminescent labeling properties that make it a suitable agent for bioimaging applications. The economic feasibility of the developed fluorescent dye-zeolite probes was also examined through a detailed cost analysis, which further highlights their commercial potential.

Carbon Quantum Dots from Amino Acids Revisited: Survey of Renewable Precursors toward High Quantum-Yield Blue and Green Fluorescence.

Carbon quantum dots (CQDs) were synthesized via a green, one-step hydrothermal method. As CQD precursors, nine amino acids of different structural descriptors (negatively/positively charged in water, polar, hydrophobic, sulfur-containing, and other/complex ones) were surveyed: Asp, Cys, Gly, His, Leu, Lys, Phe, Pro, and Ser. The reactions were performed in an autoclave in the presence of citric acid at 180 °C for 24 h and yielded core-shell CQDs. CQDs were comprehensively characterized by transmission electron microscopy, dynamic light scattering, Raman, UV/Vis, infrared, X-ray photoelectron spectroscopy, and fluorescence spectroscopy. At the excitation wavelength of λex = 350 nm, Cys-, Phe-, Leu-, and Lys-based CQDs displayed the highest quantum yield blue fluorescence-90 ± 5, 90 ± 4, 87 ± 5, and 67 ± 3%, respectively-superior to the conventional fluorescent dyes. Strikingly, for Lys- and Phe-CQDs, dissimilar trends in the excitation-emission wavelength relationships were identified, that is, constantly strong red shifts versus excitation wavelength-independent emission. Cys- and Lys-CQDs were water-dispersible toward the narrow unimodal distribution of hydrodynamic diameters-0.6 and 2.5 nm, respectively. Additionally, Lys- and Cys-CQDs, with high absolute zeta potential values, formed stable aqueous colloids in a broad range of pH (2, 7, and 12). The results constitute important premises for water-based applications of CQDs, such as bioimaging or photocatalysis.

Synthesis and Characterization of Diketopyrrolopyrrole-Based Aggregation-Induced Emission Nanoparticles for Bioimaging.

Conventional fluorescent dyes have the property of decreasing fluorescence due to aggregation-caused quenching effects at high concentrations, whereas aggregation-induced emission dyes have the property of increasing fluorescence as they aggregate with each other. In this study, diketopyrrolopyrrole-based long-wavelength aggregation-induced emission dyes were used to prepare biocompatible nanoparticles suitable for bioimaging. Aggregation-induced emission nanoparticles with the best morphology and photoluminescence intensity were obtained through a fast, simple preparation method using an ultrasonicator. The optimally prepared nanoparticles from 3,6-bis(4-((E)-4-(bis(40-(1,2,2-triphenylvinyl)-[1,10-biphenyl]-4-yl)amino)styryl)phenyl)-2,5-dihexyl-2,5-dihydropyrrolo[3,4-c]pyrrole-1,4-dione (DP-R2) with two functional groups having aggregation-induced emission properties and additional donating groups at the end of the triphenylamine groups were considered to have the greatest potential as a fluorescent probe for bioimaging. Furthermore, it was found that the tendency for aggregation-induced emission, which was apparent for the dye itself, became much more marked after the dyes were incorporated within nanoparticles. While the photoluminescence intensities of the dyes were observed to decrease rapidly over time, the prepared nanoparticles encapsulated within the biocompatible polymers maintained their initial optical properties very well. Lastly, when the cell viability test was conducted, excellent biocompatibility was demonstrated for each of the prepared nanoparticles.

An Integrated Pulsation-Free, Backflow-Free Micropump Using the Analog Waveform-Driven Braille Actuator

The widespread adoption of long-term organs-on-a-chip culture necessitates both active perfusions that mimic physiological flow conditions and minimization of the complexity of microfluidic system and fluid handling. In particular, flow in microtissue such as microvascular is free of pulsation and backflow. The refreshable Braille actuator-based integrated microfluidic system can be employed with simple microchannels and setups. However, due to high pulsatile flow and backflow, ordinary Braille-driven micropumps generate non-physiological flow conditions. We have described a simple method for creating steady flow employing Braille actuators driven with a high-voltage analog waveform, called “constant flow waveform”, without incorporating complicated structures into the microchannel or actuator. We determined the constant flow waveform by measuring volume change of microchannel caused by actuated Braille pins using a conventional fluorescent dye and microscope. Using the constant flow waveform, we demonstrated that a Braille-driven pump reduced pulsating flow by 79% and backflow by 63% compared to conventional Braille-driven pump. Furthermore, we demonstrated that a parallel pair of three-stranded pin pumps effectively eliminated backflow by driving two pumps with the constant flow waveform half-cycle shifted to each other. Moreover, by raising the driving frequency, we could increase the average flow rate to ~2× higher than previously reported flow rate of a typical Braille-driven micropump.

COL0RME: Super-resolution microscopy based on sparse blinking/fluctuating fluorophore localization and intensity estimation.

To overcome the physical barriers caused by light diffraction, super-resolution techniques are often applied in fluorescence microscopy. State-of-the-art approaches require specific and often demanding acquisition conditions to achieve adequate levels of both spatial and temporal resolution. Analyzing the stochastic fluctuations of the fluorescent molecules provides a solution to the aforementioned limitations, as sufficiently high spatio-temporal resolution for live-cell imaging can be achieved using common microscopes and conventional fluorescent dyes. Based on this idea, we present COL0RME, a method for covariance-based super-resolution microscopy with intensity estimation, which achieves good spatio-temporal resolution by solving a sparse optimization problem in the covariance domain and discuss automatic parameter selection strategies. The method is composed of two steps: the former where both the emitters' independence and the sparse distribution of the fluorescent molecules are exploited to provide an accurate localization; the latter where real intensity values are estimated given the computed support. The paper is furnished with several numerical results both on synthetic and real fluorescence microscopy images and several comparisons with state-of-the art approaches are provided. Our results show that COL0RME outperforms competing methods exploiting analogously temporal fluctuations; in particular, it achieves better localization, reduces background artifacts, and avoids fine parameter tuning.

Blocking Energy-Loss Pathways for Efficient All-Fluorescent Solution-processed Organic Light-emitting Diodes by Introducing Polymer Additive

Organic light-emitting diodes (OLEDs) based on thermally activated delayed fluorescence-sensitized conventional fluorescence dyes (TSCF) offer the possibility of realizing an ultimate high efficiency and long-term stability devices through solution process. However, the currently reported TSCF-OLEDs easily suffer the harmful Dexter energy transfer (DET) process and aggregation induced quenching (ACQ) effect. Herein, we proposed a new strategy to suppress the DET and ACQ effect by introducing a polymer material into TSCF system, achieving high efficiency and stability of TSCF-OLEDs. The introducing polymer material into TSCF system can not only increase the intermolecular distance between TADF matrix and traditional dyes, further restraining the harmful DET process and ACQ effect, but also improve the solubility and film quality of all TSCF system. Based on this fact, the 2-(2,7-di(9H-carbazol-9-yl)-9,9-dimethylacridin-10(9H)-yl)dibenzo[b, d]thiophene 5,5-dioxide (2Cz-DMAC-BTB) sensitizing 2,8-Di-tert-butyl-5,11-bis(4-tert-butylphenyl)-6,12-diphenyltetracene (TBRb) solution-processed device Y2 with poly ethlene oxide (PEO) was firstly fabricated and exhibits a higher maximum EQE of 6.6 % and longer half time (LT50) of 64 hours comparing to that of Y1 without PEO. Subsequently, the TSCF-solution-processed device R2 with PEO shows a maximum EQEmax of 13.1 % and LT50 of 107 hours. These results adequately demonstrate the validity of our proposed strategy and provide a new route for developing more efficient all-fluorescent solution-processed TSCF-OLEDs.

LoopTag FRET Probe System for Multiplex qPCR Detection of Borrelia Species.

Background: Laboratory diagnosis of Lyme borreliosis refers to some methods with known limitations. Molecular diagnostics using specific nucleic acid probes may overcome some of these limitations. Methods: We describe the novel reporter fluorescence real-time polymerase chain reaction (PCR) probe system LoopTag for detection of Borrelia species. Advantages of the LoopTag system include having cheap conventional fluorescence dyes, easy primer design, no restrictions for PCR product lengths, robustness, high sequence specificity, applicability for multiplex real-time PCRs, melting curve analysis (single nucleotide polymorphism analysis) over a large temperature range, high sensitivity, and easy adaptation of conventional PCRs. Results: Using the LoopTag probe system we were able to detect all nine tested European species belonging to the Borrelia burgdorferi (sensu lato) complex and differentiated them from relapsing fever Borrelia species. As few as 10 copies of Borrelia in one PCR reaction were detectable. Conclusion: We established a novel multiplex probe real-time PCR system, designated LoopTag, that is simple, robust, and incorporates melting curve analysis for the detection and in the differentiation of European species belonging to the Borrelia burgdorferi s.l. complex.

Anthryl-cinnamonitrile-based supramolecular artificial light-harvesting systems with high efficiency fabricated in aqueous solution

Two highly efficient artificial light-harvesting systems (ALHSs) in water have been successfully fabricated through the supramolecular assembly of an anthryl-cinnamonitrile derivative (ABTA), a water-soluble pillar[5]arene (WP5), and two conventional fluorescent dye molecules (Nile Red (NiR) and sulforhodamine (SR101)). The fabricated ALHSs display efficient energy transfer efficiency (85.7% for WP5⊃ABTA-NiR and 83.2% for WP5⊃ABTA-SR101) and possess ultrahigh donor-acceptor molar ratio ([ABTA]/[NiR] = 250:1 and [ABTA]/[SR101] = 250:1). Significantly, the formed WP5⊃ABTA nanoparticles enhance the aggregation-induced emission ability of ABTA and function as a brilliant donor to transfer the harvested energy to acceptors NiR and SR101 in aqueous solution with high antenna effects (21.8 for WP5⊃ABTA-NiR and 26.1 for WP5⊃ABTA-SR101).

Role of Aqueous-Phase Calcination in Synthesis of Ultra-Stable Dye-Embedded Fluorescent Nanoparticles for Cellular Probing.

Fluorescence imaging is a major driver of discovery in biology, and an invaluable asset in clinical diagnostics. To overcome quenching limitations of conventional fluorescent dyes and further improve intensity, nanoparticle-based constructs have been the subject of intense investigation, and within this realm, dye-doped silica-coated nanoparticles have garnered significant attention. Despite their growing popularity in research, fluorescent silica nanoparticles suffer from a significant flaw. The degradation of these nanoparticles in biological media by hydrolytic dissolution is underreported, leading to serious misinterpretations, and limiting their applicability for livecellandinvivoimaging. Here, the development of an ultra-stable, dye-embedded, silica-coated metal nanoparticle is reported, and its superior performance in long-term live cell imaging is demonstrated. While conventional dye-doped silica nanoparticles begin to degrade within an hour in aqueous media, by leveraging a modified liquid calcination process, this new construct is shown to be stableforat least 24 h.The stability of this metal-enhanced fluorescent probe in biologically relevant temperatures and media, and its demonstrated utility for cell imaging, paves the way for its future adoption in biomedical research.

Ultrasensitive biogenic amine sensor using an enhanced multiple nanoarray chip based on competitive reactions in an evanescent field

Considering the importance of biogenic amines (BAs), such as histamine, tyramine, and putrescine, as biomarkers and the challenges in their simultaneous detection at low concentrations, a novel enhanced multiple nanoarray BA sensor was developed using a competitive reaction in an evanescent field (EF). BAs were bound to specific antibodies on different gold nanoarray islands on a multiple nanoarray sensor chip. The electromagnetic field in the EF produced fluorescence signals of BA-conjugated quantum dots with an excellent signal-to-noise ratio on the islands. Compared to conventional fluorescent dyes or plasmonic nanoparticles as detection probes, quantum dots showed improved detection sensitivity with excellent photostability. The competitive reaction in EF was simultaneously used to detect three BA molecules on the multiple nanoarray. The multiple BA sensor exhibited an excellent detection limit of 63 aM with a wide dynamic range of 100 aM–10 nM, which had a 1,000,000-fold higher sensitivity than that of previously reported methods. The proposed BA sensor was validated by high-performance liquid chromatography and enzyme-linked immunosorbent assay and was applied to identify BAs in wine samples. The results agreed with those of standard methods, showing 95 % confidence level. The combined competitive reaction and simultaneous detection of BA-conjugated quantum dots in EF on the multiple nanoarray sensor exhibited excellent enhancement of detection sensitivity. This high-throughput screening method shows highly specific labeling using promiscuous antibodies for detecting small molecules in complex matrices.

Cationic Tricyclic AIEgens for Concomitant Bacterial Discrimination and Inhibition.

New ionic compounds with aggregation-induced emission (AIE) feature has been widely studied. These AIE-based luminogens (AIEgens) not only effectively resolve aggregation-caused quenching (ACQ) problems that are encountered for most of conventional fluorescent dyes, but also exhibit promising applications in biological imaging, potentially for a wide variety of diseases. However, such an AIE system needs to be further developed. In this work, a series of novel cationic AIEgens that are comprised of tricyclic 2-aminopyridinium derivatives with seven-membered rings are designed and synthesized via a simple, multicomponent reaction. Notably, these AIEgens exhibit the ability to specifically stain gram-positive bacteria. Moreover, a specific AIEgen, BMTAP-7, possesses highly efficient bacteriostatic ability for Staphylococcus aureus (S. aureus) in both liquid medium and solid agar plates, which have a minimum inhibitory concentration (MIC) between 4 and 8 µg mL-1 . Using live-cell imaging and a wash-free process, it is observed that hydrophilic AIEgens are localized to mitochondria, whereas lipophilic AIEgens display specific staining of lysosomes. These AIEgens with bacteriostatic activity hold great promise for distinguishing between bacterial types and inhibiting bacterial infections in situ.

Highly Efficient Near-Infrared Thermally Activated Delayed Fluorescence Molecules via Acceptor Tuning: Theoretical Molecular Design and Experimental Verification.

Near-infrared (NIR) thermally activated delayed fluorescence (TADF) materials have shown great application potential in organic light-emitting diodes, photovoltaics, sensors, and biomedicine. However, their fluorescence efficiency (ΦF) is still highly inferior to those of conventional NIR fluorescent dyes, seriously hindering their applications. This study aims to provide theoretical guidance and experimental verification for highly efficient NIR-TADF molecular design. First, the light-emitting mechanism of two deep-red TADF molecules is revealed using first-principles calculation and the thermal vibration correlation function (TVCF) method. Then several acceptors are theoretically designed by changing the position of the cyano group or by introducing the phenanthroline into CNBPz, and 44 molecules are designed and studied theoretically. The photophysical properties of DA-3 in toluene and the amorphous state are simulated using a multiscale method combined with the TVCF method. The NIR-TADF property for DA-3 is predicted both in toluene and in the amorphous state. Experimental measurement further confirms that the TADF emission wavelength of DA-3 is 730 nm and ΦF is as high as 20%. It is the highest fluorescence efficiency reported for TADF molecules with emission wavelengths larger than 700 nm in toluene. Our work provides an effective molecular design strategy, and a good candidate for highly efficient NIR-TADF emitters is also predicted.

Multiphoton Deep-Tissue Imaging of Micrometastases and Disseminated Cancer Cells Using Conjugates of Quantum Dots and Single-Domain Antibodies.

Early detection of malignant tumors, micrometastases, and disseminated tumor cells is one of the effective way of fighting cancer. Among the many existing imaging methods like computed tomography (CT), ultrasound (US), magnetic resonance imaging (MRI), positron emission tomography (PET), and single-photon emission computed tomography (SPECT), optical imaging with fluorescent probes is one of the most promising alternatives because it is fast, inexpensive, safe, sensitive, and specific. However, traditional fluorescent probes, based on organic fluorescent dyes, suffer from the low signal-to-noise ratio. Furthermore, conventional organic fluorescent dyes are unsuitable for deep tissue imaging because of the strong visible light absorption by biological tissues. The use of fluorescent semiconductor nanocrystals, or quantum dots (QDs), may overcome this limitation due to their large multiphoton cross section, which ensures efficient imaging of thick tissue sections inaccessible with conventional fluorescent probes. Moreover, the lower photobleaching and higher brightness of fluorescence signals from QDs ensures a much better discrimination of positive signals from the background. The use of fluorescent nanoprobes based on QDs conjugated to uniformly oriented high-affinity single-domain antibodies (sdAbs) may significantly increase the sensitivity and specificity due to better recognition of analytes and deeper penetration into tissues due to small size of such nanoprobes.Here, we describe a protocol for the fabrication of nanoprobes based on sdAbs and QDs, preparation of experimental xenograft mouse models for quality control, and multiphoton imaging of deep-tissue solid tumors, micrometastases, and disseminated tumor cells.

Aggregation-induced Emission Based Fluorogens for Mitochondria-targeted Tumor Imaging and Theranostics.

Occurrence and development of cancer are multifactorial and multistep processes which involve complicated cellular signaling pathways. Mitochondria, as the energy producer in cells, play key roles in tumor cell growth and division. Since mitochondria of tumor cells have a more negative membrane potential than those of normal cells, several fluorescent imaging probes have been developed for mitochondria-targeted imaging and photodynamic therapy. Conventional fluorescent dyes suffer from aggregation-caused quenching effect, while novel aggregation-induced emission (AIE) probes are ideal candidates for biomedical applications due to their large stokes shift, strong photo-bleaching resistance, and high quantum yield. This review aims to introduce the recent advances in the design and application of mitochondria-targeted AIE probes. The comprehensive review focuses on the structure-property relationship of these imaging probes, expecting to inspire the development of more practical and versatile AIE fluorogens (AIEgens) as tumor imaging and therapy agents for preclinical and clinical use.

Optical mapping of human embryonic stem cell-derived cardiomyocyte graft electrical activity in injured hearts

BackgroundHuman embryonic stem cell-derived cardiomyocytes (hESC-CMs) show tremendous promise for cardiac regeneration, but the successful development of hESC-CM-based therapies requires improved tools to investigate their electrical behavior in recipient hearts. While optical voltage mapping is a powerful technique for studying myocardial electrical activity ex vivo, we have previously shown that intra-cardiac hESC-CM grafts are not labeled by conventional voltage-sensitive fluorescent dyes. We hypothesized that the water-soluble voltage-sensitive dye di-2-ANEPEQ would label engrafted hESC-CMs and thereby facilitate characterization of graft electrical function and integration.MethodsWe developed and validated a novel optical voltage mapping strategy based on the simultaneous imaging of the calcium-sensitive fluorescent protein GCaMP3, a graft-autonomous reporter of graft activation, and optical action potentials (oAPs) derived from di-2-ANEPEQ, which labels both graft and host myocardium. Cardiomyocytes from three different GCaMP3+ hESC lines (H7, RUES2, or ESI-17) were transplanted into guinea pig models of subacute and chronic infarction, followed by optical mapping at 2 weeks post-transplantation.ResultsUse of a water-soluble voltage-sensitive dye revealed pro-arrhythmic properties of GCaMP3+ hESC-CM grafts from all three lines including slow conduction velocity, incomplete host-graft coupling, and spatially heterogeneous patterns of activation that varied beat-to-beat. GCaMP3+ hESC-CMs from the RUES2 and ESI-17 lines both showed prolonged oAP durations both in vitro and in vivo. Although hESC-CMs partially remuscularize the injured hearts, histological evaluation revealed immature graft structure and impaired gap junction expression at this early timepoint.ConclusionSimultaneous imaging of GCaMP3 and di-2-ANEPEQ allowed us to acquire the first unambiguously graft-derived oAPs from hESC-CM-engrafted hearts and yielded critical insights into their arrhythmogenic potential and line-to-line variation.

Enhancement of Lipid Productivity of Chlorella sp. Using Light-Converting Red Fluorescent Films Based on Aggregation-Induced Emission

The conversion of light wavelength from green (500–600 nm) to red (600–700 nm) in the solar spectrum can significantly enhance the biodiesel productivity of microalgae because microalgal photosynthetic pigments utilize the red light more efficiently. Herein, we applied light-converting fluorescent films to enhance the biomass and lipid productivity of oleaginous Chlorella sp. Although the fluorescent dyes have been reported to exhibit excellent fluorescence quantum yields in the solution state, the solid film state is more preferred to overcome limitations such as low stability and potential leakage issues. However, conventional fluorescent dyes exhibit poor emission in the solid film state due to aggregation-caused quenching (ACQ). Therefore, this study utilized aggregation-induced emission (AIE)-type diketopyrrolopyrrole (DPP) fluorescent dyes to overcome the ACQ problems and to fabricate highly efficient light-converting red fluorescent films. The fabricated light-converting film showed excellent photosynthetic photon flux density increase in the red wavelength range by AIE. A maximum total fatty acid methyl ester increase of Chlorella sp. was 28.8% using a light-converting film containing a deep-red (650–700 nm) emitting dye M2. In conclusion, we confirmed that the use of solar energy with light-converting films could boost microalgal productivity efficiently, even without using light-emitting diodes that require electricity.

Detection of tannic acid exploiting carbon dots enhanced hydrogen peroxide/potassium ferricyanide chemiluminescence

Recently, ultra-weak chemiluminescence (CL) systems have become one of the focuses of increasing attention. As one of them, H2O2-K3Fe(CN)6 system had also been studied. However, no attempts had been made to investigate the analytical applications of this system based on carbon dots (CDs). In this paper, nitrogen-doped carbon dots (FNCDs) were synthesized using formaldehyde as a coreactant, and it acted as a new fluorophore instead of conventional fluorescent dyes to enhance the CL signal of H2O2-K3Fe(CN)6 system, in which the excited-state FNCDs was the final emitting species, and was probably produced by the electron transfer and energy from reactive oxygen species. Interestingly, tannic acid (TA) could dramatically suppress the CL intensity of FNCDs-H2O2-K3Fe(CN)6 system. Under the optimum conditions, a linear relationship existed between reduced CL intensity and logarithm of TA concentration in range between 0.2 and 10.0 μM with a detection limit of 39.3 nM. The method was applied to the quantitative analysis of TA concentration in red wine.