Fluorescent Probe Research Articles

Chromone-based fluorescent probe for peroxynitrite imaging in Arabidopsis thaliana

As a typical reactive nitrogen species, peroxynitrite (ONOO−) plays an important role in cells and organisms. But in plants, information on the role of endogenous ONOO− remains limited. In order to explore its functions, it is necessary to probe ONOO− in biological systems, especially in plants. In this paper, we report RAW-A, a chromone-based fluorescence probe, exhibits a highly selective and sensitive response to ONOO−. It is worth noting that RAW-A has good water solubility, which is beneficial for the application of biological systems. RAW-A can respond to ONOO− even at low concentrations of ONOO−, indicating that the probe is expected to monitor ONOO− in real-time in living systems. In addition, confocal imaging experiments show that RAW-A can image endogenous and exogenous ONOO− in Arabidopsis thaliana root besides HeLa cell. It shows that RAW-A has the potential to be an imaging tool for studying the biological roles of ONOO− in plants. To our knowledge, RAW-A is the first fluorescent probe with highly selective and sensitive response to ONOO− in plants.

Design of new boron-doped carbon dots for nano-level assay of nebivolol in human plasma and commercial products; Application to greenness assessments

Recently, nanomaterials have attracted a lot of attention due to their potential as effective fluorescent nano-sensor probes. They were distinguishing substitutes for other luminescent techniques, such as fluorescent dyes and luminous derivatization, because of their affordability, environmental friendliness, and special photocatalytic properties. In the suggested work, a straightforward method was used to create boron and nitrogen carbon dots (B@CDs) with a good quantum yield value of 31.15% utilizing boric acid and di-sodium EDTA. For the purpose of characterizing QDs, a variety of instruments were employed, such as transmission electron microscopy, fluorescence spectroscopy, X-ray FTIR, and UV–VIS spectroscopy. Nebivolol (NEB) is a cardiovascular medication used globally to treat congestive heart failure and hypertension, is in the meantime. For this reason, a brand-new, environmentally friendly analytical technique was created to determine the amount of human plasma, uniformity test, and commercial nebivolol (NEB) tablets. After gradually adding NEB, the response of B@CQDs was enhanced at 438 nm (excitation at 371 nm). The calibration graph ranged between 20 and 500 ng mL−1 with a quantification limit (LOQ) of 2.50 ng mL−1 and a detection limit (LOD) of 0.82ng mL−1.

A phenothiazine coumarin based fluorescent probe with AIE feature for real-time detecting lysosomal ClO– in living cell

A new phenothiazine coumarin based probe WX-Lyso for detection of ClO– was developed. The probe showed obvious aggregation-induced emission (AIE) characteristic and exhibited a highly selective and sensitive turn-on fluorescence signal at 544 nm for ClO– with a large Stokes shift of 144 nm. The limit of detection (LOD) of ClO– was measured as low as 0.99 μM and a good line equation was obtained in the 0–50 μM concentration range. The detection mechanism was elucidated FT-IR, ESI-MS analysis and DFT. Furthermore, the probe had been demonstrated successfully has good lysosomal-targeting and high-contrast imaging abilities, which has the potential to become a new chemical tool and provide help for detecting ClO– in living systems.

Regulation of cardiac fibroblasts reprogramming into cardiomyocyte-like cells with a cocktail of small molecule compounds.

Myocardial infarction results in extensive cardiomyocyte apoptosis, leading to the formation of noncontractile scar tissue. Given the limited regenerative capacity of adult mammalian cardiomyocytes, direct reprogramming of cardiac fibroblasts (CFs) into cardiomyocytes represents a promising therapeutic strategy for myocardial repair, and small molecule drugs might offer a more attractive alternative to gene editing approaches in terms of safety and clinical feasibility. This study aimed to reprogram rat CFs into cardiomyocytes using a small molecular chemical mixture comprising CHIR99021, Valproic acid, Dorsomorphin, SB431542, and Forskolin. Immunofluorescence analysis revealed a significant increase in the expression of cardiomyocyte-specific markers, including cardiac troponin T (cTnT), Connexin 43 (Cx43), α-actinin, and Tbx5. Changes in intracellular calcium ion levels and Ca2+ signal transfer between adjacent cells were monitored using a calcium ion fluorescence probe. mRNA sequencing analysis demonstrated the upregulation of genes associated with cardiac morphogenesis, myocardial differentiation, and muscle fiber contraction during CF differentiation induced by the small-molecule compounds. Conversely, the expression of fibroblast-related genes was downregulated. These findings suggest that chemical-induced cell fate conversion of rat CFs into cardiomyocyte-like cells is feasible, offering a potential therapeutic solution for myocardial injury.

Metal-organic frameworks constructed with base-acid mixed ligands and its potential as dual-functional fluorescent probe toward Fe3+/Al3+ ions

By virtue of mixed ligand strategy (2,5-Bis(1H-pyrazole-4-ylmethylene)-cyclopentanone and 2,5-dihydroxyterephthalic acid / terephthalic acid), four new metal–organic frameworks (MOFs) were fabricated and characterized. When 2,5-dihydroxyterephthalic acid acted as auxiliary ligand, MOFs 1–3 show 1D chain structure. 4 containing auxiliary ligand terephthalic acid (without − OH group) displays a 2D layer structure. Notably, 1 exhibits the significant selectivity toward Fe3+ and Al3+ ions, whereas the fluorescence intensity of 4 changed slightly in the presence of various metal ions, indicating that uncoordinated –OH in 1 plays an important role in sensing process. Moreover, it is revealed that 1 could act as dual-functional fluorescent probe toward Fe3+ and Al3+ with selectivity, sensitivity and reusability, and it could be prepared as fluorescent test papers for rapid on-site detection.

Peptide-Based Turn-On Fluorescent Probes for Highly Specific Detection of Survivin Protein in the Cancer Cells

Peptide-Based Turn-On Fluorescent Probes for Highly Specific Detection of Survivin Protein in the Cancer Cells

A Low-molecular-weight, Long-wavelength Emissive Coumarin: Green Synthesis, Spectral Properties, Fluorescence Enhancement and Solvatochromism Application

In this study, a novel low-molecular-weight coumarin fluorescent dye, 3,4-dicyano-7-diethylaminocoumarin, was designed. This dye features a donor-π-bridge-acceptor (D-π-A) conjugated structure, which confers superior fluorescence properties.The dye was synthesized using a simple, efficient, and environmentally friendly two-step process, facilitating the direct conversion of the key intermediate into the final product via simultaneous addition and elimination reactions. A comprehensive structural characterization of the dye was undertaken, and its UV absorption and fluorescence emission properties were extensively analyzed using spectroscopic techniques, with structural explanations of the fluorescence activities provided by the Density Functional Theory (DFT) method.Experimental results revealed that this coumarin dye emits strong fluorescence, characterized by a long wavelength, a large Stokes shift, and high fluorescence intensity. It exhibits excellent fluorescent performance in various solvents. Despite experiencing fluorescence quenching in its solid state, the formation of an inclusion complex with β-cyclodextrin restores strong red fluorescence, presenting new possibilities for biofluorescence imaging. Notably, this coumarin dye also demonstrates a significant solvatochromic effect. This effect enables rapid visual discrimination among multiple sets of structurally and chemically similar organic solvents. Consequently, the dye holds promise as a versatile solvatochromic fluorescent probe for a broad spectrum of applications.

Fluorescence lifetime imaging microscopy of flexible and rigid dyes probes the biophysical properties of synthetic and biological membranes

Sensing of the biophysical properties of membranes using molecular reporters has recently regained widespread attention. This was elicited by the development of new probes of exquisite optical properties and increased performance, combined with developments in fluorescence detection. Here, we report on fluorescence lifetime imaging of various rigid and flexible fluorescent dyes to probe the biophysical properties of synthetic and biological membranes at steady state as well as upon the action of external membrane-modifying agents. We tested the solvatochromic dyes Nile red and 1,2-dimyristoyl-sn-glycero-3-phosphoethanolamine-N-(7-nitro-2-1,3-benzoxadiazol-4-yl) (ammonium salt), the viscosity sensor Bodipy C12, the flipper dye FliptR, as well as the dyes 3,3′-dioctadecyloxacarbocyanine perchlorate, Bodipy C16, lissamine-rhodamine, and Atto647, which are dyes with no previous reported environmental sensitivity. The performance of the fluorescent probes, many of which are commercially available, was benchmarked with the well-known environmental reporters, with Nile red and Bodipy C12 being specific reporters of medium hydration and viscosity, respectively. We show that some widely used ordinary dyes with no previous report of sensing capabilities can exhibit competing performance compared to highly sensitive commercially available or custom-based solvatochromic dyes, molecular rotors, or flipper in a wide range of biophysics experiments. Compared to other methods, fluorescence lifetime imaging is a minimally invasive and nondestructive method with optical resolution. It enables biophysical mapping at steady state or assessment of the changes induced by membrane-active molecules at subcellular level in both synthetic and biological membranes when intensity measurements fail to do so. The results have important consequences for the specific choice of the sensor and take into consideration factors such as probe sensitivity, response to environmental changes, ease and speed of data analysis, and the probe’s intracellular distribution, as well as potential side effects induced by labeling and imaging.

Lanthanide doped metal−organic framework: novel turn-on fluorescent sensing of iodide in kelp and seawater samples

An effective fluorescence sensor was developed for iodide detection, with copper-based metal−organic frameworks (Cu-BTC) into which Tb3+ was doped by post modification. Tb@Cu-BTC manifested the characteristic emission of Tb3+ resulted from efficient sensitization through antenna effect, which was further exploited as a “turn-on” fluorescence probe to determinate iodide in aqueous solution. The sensor exhibited two great linear ranges of 12.5 ∼ 40 μM and 40 ∼ 160 μM, with a good limit of detection of 4.7 μM for iodide. These results showed that Tb@Cu-BTC exhibited high selectivity, excellent stability and great anti-interference capability for iodide monitoring. The possible mechanism could be object-induced luminescence. In addition, recovery experiments have been carried out to determine iodide in kelp standard sample, tap water and sea water. This method based on Tb@Cu-BTC could also be potentially employed to determinate iodide in other samples.

Miniature wireless LED-device for photodynamic-induced cell pyroptosis

The inability of visible light to penetrate far through biological tissue limits its use for phototherapy and photodiagnosis of deep-tissue sites of disease. This is unfortunate because many visible dyes are excellent photosensitizers and photocatalysts that can induce a wide range of photochemical processes, including photogeneration of reactive oxygen species. One potential solution is to bring the light source closer to the site of disease by using a miniature implantable LED. With this goal in mind, we fabricated a wireless LED-based device (volume of 23 mm3) that is powered by RF energy and emits light with a wavelength of 573 nm. It has the capacity to excite the green absorbing dye Rose Bengal, which is an efficient type II photosensitizer. The wireless transfer of RF power is effective even when the device is buried in chicken breast and located 6 cm from the transmitting antenna. The combination of a wireless device as light source and Rose Bengal as photosensitizer was found to induce cell death of cultured HT-29 human colorectal adenocarcinoma cells. Time-dependent generation of protruding bubbles was observed in the photoactivated cells suggesting cell death by light-induced pyroptosis and supporting evidence was gained by cell staining with the fluorescence probes Annexin-V FITC and Propidium Iodide. The results reveal a future path towards a wireless implanted LED-based device that can trigger photodynamic immunogenic cell death in deep-seated cancerous tissue.

Sensitive and rapid detection of ciprofloxacin and ofloxacin in aqueous samples by a facile and green synthesized copper nanocluster as a turn-on fluorescent probe

The present method reports a rapid, inexpensive and sensitive sensing system based on fluorescence turn-on strategy for trace detection of ciprofloxacin (CIP) and ofloxacin (OFL) in aqueous samples. In a one pot method, copper nanocluster whose dimensions are less than 15 nm, were easily prepared and decorated with sodium gluconate (Gl@CuNCs) as a biocompatible material.The Gl@CuNCs were characterized with XRD, TEM, DLS, TG-DTA techniques as well UV–Vis, FT-IR and fluorescence spectroscopies.The maximum fluorescence emission of Gl@CuNCs at 414 nm with excitation at 322 nm shifted to higher wavelength upon addition of CIP and OFL. A good linear relationship between fluorescence emission and drug concentration was achieved in the concentration range of 0.005–0.3 μg mL−1 (15–900 nM for CIP and 14–830 nM for OFL). The limits of detection (LOD) for the determinations of CIP and OFL were calculated to be 9 and 8 nM, respectively. Furthermore, even a 100-fold higher concentration of interfering species had no significant effect on the detection of CIP and OFL. The proposed method was successfully used to determine CIP and OFL in drinking water, cow milk, human urine and serum samples with satisfactory recoveries.

Fluorescent rotor: Labeling lysosomes, mitochondria and lipid droplets through polarity and viscosity assessment

The viscosity and polarity of cells are inherent physical parameters, and changes to these attributes are frequently linked to malfunctioning conditions or different diseases. Cancer cells often harbor elevated nonpolar lipid droplets (LDs), acting as energy reserves. The rise in lipid droplets (LDs) and viscosity, distinctive traits of cancer cells, has motivated us to develop a fluorescent probe based on naphthalimide. The fluorescent marker LD-VP exhibits fluorescence signals at 520 nm in nonpolar dioxane and 600 nm in highly viscous glycerol. This implies that probe LD-VP can furnish details regarding cellular microviscosity and lipid droplets within live cells by providing dual-channel images. The probe LD-VP is chemically inert and harmless, enabling its safe utilization in live cell imaging. We conducted fluorescence imaging based on viscosity using probe LD-VP in the red channel, which is found to be co-localized in both mitochondria and lysosomes. Moreover, the probe effectively marks lipid droplets in the green channel. The probe LD-VP represents a distinctive fluorescent tool capable of monitoring both viscosity and lipid droplet expression in live cells. This tool holds the potential for visualizing physiological abnormalities or pathological conditions.

Ratiometric Sensing of Azithromycin and Sulfide Using Dual Emissive Carbon Dots: A Turn On-Off-On Approach.

A novel ratiometric fluorescence probe was developed for the determination of azithromycin (AZM) and sulfide ions based on the differential modulation of red emissive carbon dots (R-N@CDs) and blue emissive carbon dots (B-NS@CDs). The addition of sulfide anion selectively quenched the red emission of R-N@CDs while the blue emission of B-NS@CDs unaffected. Upon subsequent introduction of AZM to this R-N@CDs@sulfide system, the quenched red fluorescence was restored. Comprehensive characterization of the CDs was performed using UV-Vis, fluorescence, FTIR spectroscopy, XPS, and TEM. The proposed method exhibited excellent sensitivity and selectivity, with limits of detection of 0.33 µM for AZM and 0.21 µM for sulfide. Notably, this approach enabled direct detection of sulfide without requiring prior modulation of the CDs with metal ions, as is common in other reported methods. The ratiometric probe was successfully applied for the determination of AZM in biological fluids and sulfide in environmental water samples with high selectivity. This work presents the first fluorometric method for the detection of AZM in biological fluids.

A new fluorescent probe for detection of hydrazine and extremely acidic pH in different modes

Toxic hydrazine poses a huge threat to living organisms and our environment. Extremely acidic pH is also harmful to various ecosystems. Here, a coumarin-based dye called CMM has been synthesized for the ratiometric detection of hydrazine (F504 nm/F560 nm). CMM could detect gaseous hydrazine in the environment and endogenous hydrazine in live cells. Furthermore, the fluorescence at 563 nm of CMM was stable from pH 10.0 to 2.0, whereas increased greatly from pH 2.0 to 1.2. Thus, the probe could also detect extremely acidic pH with great fluorescence enhancement. The pKa value was determined to be as low as 1.41. We anticipate that the probe could provide a good candidate for detection of toxic hydrazine and extremely acidic pH.

Synthesis and fluorescence properties of a two-dimensional Cd-complex for the ratiometric fluorescence detection of Zn2+ ions

The two-dimensional complex [Cd3(L)(2,2′-bpy)2]n (1) was synthesized solvothermally from 4,5-di(3,5-dicarboxylphenoxy)phthalic acid (H6L) and 2,2′-bipyridine (2,2′-bpy) and fully characterized by elemental analysis, infrared spectroscopy, single crystal and powder X-ray diffraction. Complex 1 displays high stability in water and resistance towards acidic and basic media. Fluorescence studies revealed that it may be acted as a ratiometric fluorescence probe to detect Zn2+ ions in water with a superior detection limit of 3.48 nM. The fluorescence recognition mechanism stems from weak interactions between Zn2+ ions and complex 1. Its pronounced stability and recyclability suggest that the new material may be used for high-precision detection of Zn2+ ions in real-life aqueous samples, even under acidic and basic conditions.

Carbon quantum dots as a turn-on fluorescent probe for the sensitive detection of Cd2+

In this study, fluorescent carbon dots were synthesized for the first time using ammonium citrate and glutamic acid as precursors via a one-pot hydrothermal method. The synthesized carbon dots emit blue fluorescence at 436 nm (excited at 320 nm) and demonstrate excellent photobleaching resistance and fluorescence stability in high salt environments. Within the range of 1–25 μM, the fluorescence of CDs gradually increases with the increasing concentration of Cd2+, reaching a limit of detection as low as 13 nM. This phenomenon could be ascribed to the chelation-enhanced fluorescence, a result of Cd2+ forming complexes with the abundant surface functional groups such as CN–, –COOH, –OH, –NH2 in CDs. Furthermore, this turn-on fluorescent probe has been successfully used for the detection of Cd2+ in tap water and lake water, providing an efficient and sensitive method for the analysis of environmental metals.

Fluorescent probe-mediated labeling and real-time tracking of lipid droplet dynamics in foam cells formation

The aberrant deposition of lipid droplets (LDs) is a pivotal feature in foam cells formation and has significant implications for understanding the pathogenesis and early diagnosis of atherosclerosis (AS). In this study, we engineered a fluorescent probe, PyTPA-LD, for the reliable tracking of intracellular LDs. Through the application of PyTPA-LD, we monitored LD generation during the transition of macrophages induced by oxidized low-density lipoprotein (ox-LDL) into foam cells. Furthermore, we observed dynamic changes in lysosomes and LDs during lipophagy in this transitional process. Our study unveiled the dual role of lysosomes in LD formation: the degradation and release of ox-LDL within lysosomes promote LDs formation, while concurrently, lipophagy contributes to LDs clearance. This novel perspective provides a comprehensive understanding of the dynamic generation and clearance of LDs during foam cells formation. This work offers crucial insights into the pathogenic mechanisms underlying AS, deepening our understanding of AS development and providing valuable insights into lipid metabolism-related diseases.

Novel fluorescent sensor based on triazole-pyridine derivative for selective detection of mercury (II) ions in different real water samples: Experimental and DFT calculations

Toxic heavy metals, particularly mercury II ions, must be selectively detected in industrial effluent to restrict their percentage and thereby aid in environmental protection. The present study describes the synthesis of 6-(4-(4-(5-cyano-6-oxo-4-styryl)-1,6-dihydropyridin-2-yl)-5-methyl-1H-1,2,3-triazol-1-yl)phenyl)-2-oxo-4-styryl)-1,2-dihydropyridine-3-carbonitrile (TOHC) and its ability as a novel selective fluorescent probe for the detection of mercury II ions in different real water samples. The structure of the prepared TOHC was confirmed by both FTIR and 1HNMR analysis, while crystal structure and thermal stability was investigated using XRD and TGA techniques. The optical properties of TOHC were investigated using both UV–vis and fluorescence spectroscopy at different pH values. Its luminescent properties obtained when TOHC is excited by a wavelength equal to 424 nm, where a maximum emission peak has observed at a wavelength equal to 466.6 nm. Moreover, using Stern-Volmer equation indicate that there is a good correlation between the concentration of Hg2+ ions and the fluorescence intensity of TOHC accompanied with high quenching rate equal to 2.24 x 104 mol−1.L. Selectivity of TOHC toward Hg2+ ions was confirmed by the assistance of fifteen different metal cations. In addition, Job’s Plot method and UV–vis spectroscopy were used to estimate the stoichiometry as well as understand the quenching mechanism between TOHC sensor and Hg2+ ions. The applicability of TOHC sensor for the detection of Hg2+ ions in real samples was further validated using five different real water samples and exhibited excellent results. Lastly, DFT calculations were conducted to provide atomistic insights into the chemical interaction between Hg(II) and TOHC.

A dual-ratiometric strategy to design the NIR-IIb reference-based activatable nanoprobe for accurate nitric oxide detection

Fluorescence imaging offers a real-time, convenient method for detection nitric oxide (NO) in vivo, especially using the near-infrared IIb (NIR-IIb, 1500-1700nm) region. However, traditional single-ratiometric fluorescent probes for NO detection suffer from signal distortion due to inherent limitations such as signal crosstalk and component separation. Herein, we proposed a dual-ratiometric strategy to ensure detection accuracy. The detection result was considered to be reliable upon the auxiliary ratio and practical ratio exhibiting a synchronous change. Based on this strategy, we fabricated a NO-responsive probe, comprising a conjugated polymer P-NH2 and a rare-earth doped nanocrystal NaYF4:Yb,Er,Ce@NaYF4:Yb,Nd@NaYF4. When interaction with NO, the probe generated two ratiometric signals: FNIR-I/FNIR-IIb and FNIR-II’/FNIR-IIb (NIR-I, 700-900nm; NIR-II’, 1000-1400nm), where the latter acted as the practical ratio for its better imaging clarity. With an acetaminophen-induced liver injury model, the probe demonstrated the potential for precise ratiometric imaging of NO distribution in vivo. Particularly, ratio imaging revealed the intricate vascular structure of the abdomen, demonstrating the significant advantages of the NIR-IIb region. Our study offers an effective approach to reduce detection errors in the bioimaging applications and provides a powerful tool for basic biomedical research.

From cell membrane to endoplasmic reticulum: Tunable lipid membrane imaging by regulating the lipophilicity and internalization of carbon dots

The interactions between various organelles play a crucial role on cellular activity, and the design and construction of multi-organelle fluorescent probes is of great challenges. Herein, fluorescent CDs with tunable cell plasma membrane and lipid-rich organelle-targeting ability were fabricated via exquisitely regulating the ratio of tridecanedioic acid and m-diethylaminophenol as the co-precursor, combining the structure–activity relationship to modulate the CDs structure and surficial property. Condensation of m-diethylaminophenol in the presence of different amount of tridecanedioic acid was exploited to construct MCDs and ECDs for targeted cell membrane and endoplasmic reticulum imaging respectively. The appropriately incorporated alkyl chains as membrane anchoring group and the suppressed internalization by carboxyl group led to the retention of MCDs in cell membrane, while the excessive introduction of alkyl chains offered ECDs with high lipophilicity, resulting in the rapid internalization and subsequential distribution in endoplasmic reticulum membrane. The favorable membrane retention capability and excellent photostability make MCDs an excellent probe for long-term targeted-imaging of cell membrane in vitro, with remarkable tracking duration long to five passages and effectively display cell membrane morphological dynamics during cell division and cell death. Moreover, real-time evaluation of cholesterol consumption of Lo phase in cell membrane via ratiometric fluorescence imaging was achieved, attributed to the sensitive response of CDs to polarity variations.