Turn-on Fluorescent Probe Research Articles

Two spirobifluene-based turn-on fluorescent probes for highly selective detection of Cysteine and the applications in cells two-photon fluorescence imaging

Two spirobifluene-based fluorescent probes SPF1 and SPF2, were designed and synthesized. The probes displayed “turn-on” fluorescence response for Cysteine. One of the challenges in developing a Cysteine probe is to secure high selectivity. SPF1/SPF2 can discriminate Cysteine from GSH as well as Hcy, and showed high substrate selectivity. The detection limit of SPF1 is 36 nM, which is excellent comparing with other optical sensors for Cysteine. The sensing mechanism of SPF1/SPF2 was verified by experimental data and theoretical calculations. There was a good linear relationship between the fluorescence intensity of SPF1/SPF2 and the concentration of Cysteine. The MTT tests indicated that SPF1/SPF2 had low cytotoxicity and good biocompatibility. Theoretical calculations demonstrated that SPF1, SPF2, and their related reaction products with Cysteine exhibited good two-photon absorption properties. Finally, SPF1/SPF2 had been successfully applied to the imaging of Cysteine in living cells under two-photon excitation.

Rapid detection of hypobromous acid by a tetraphenylethylene-based turn-on fluorescent AIE probe and its applications

BackgroundSimilar to hypochlorous acid (HClO), hypobromous acid (HBrO) is one of the most notable reactive oxygen species (ROS). Overexpression of HBrO is linked to various diseases causing organ and tissue loss. Due to HBrO's role in the oxidation of micropollutants, real-time monitoring of HBrO in water-based systems is essential. Tetraphenylethylene (TPE)-based organic aggregation-induced emission luminophores (AIEgens) are an emerging category of fluorescent probe materials that have attracted considerable attentions. However, AIE probes are rarely applied to detect HBrO. Developing faster, more precise, and more sensitive AIE probes is thus crucial for detecting biological and environmental HBrO. ResultsA small molecule fluorescent probe 4-(1,2,2-triphenylvinyl)benzamidoxime (SWJT-21) was synthesized for the sensitive and selective detection of hypobromous acid (HBrO) based on aggregation-induced emission (AIE). The amidoxime unit of SWJT-21 would undergo an oxidation reaction with HBrO, leading to a structure differentiation between the probe and the product, and therefore the turn-on fluorescence by the AIE effect. The probe could recognize hypobromous acid rapidly (less than 3 s) in high aqueous phase (99 % water) with a turn-on fluorescence response. It was determined that the limit of detection for HBrO was 5.47 nM. Moreover, SWJT-21 demonstrates potential as a test strip for the detection of HBrO. SWJT-21 was also successfully used for the monitoring of HBrO in water samples and for the detection of endogenous/exogenous HBrO in living cells and zebrafish. SignificanceA special AIE fluorescence turn-on probe SWJT-21 based on tetraphenylethylene was designed for detecting HBrO in the environmental and biological systems. This probe has an extremely low detection limit of 5.47 nM and is able to detect HBrO in 99 % aqueous phase in less than 3 s.

Visualized Enzyme-Activated Fluorescence Probe for Accurately Detecting β-Gal in Living Cells and BALB/c Nude Mice.

Colorectal cancer was one of the major malignant tumors threatening human health and β-Gal was recognized as a principal biomarker for primary colorectal cancer. Thus, designing specific and efficient quantitative detection methods for measuring β-Gal enzyme activity was of great clinical test significance. Herein, an ultrasensitive detection method based on Turn-on fluorescence probe (CS-βGal) was reported for visualizing the detection of exogenous and endogenous β-galactosidase enzyme activity. The test method possessed a series of excellent performances, such as a significant fluorescence enhancement (about 11.3-fold), high selectivity as well as superior sensitivity. Furthermore, under the optimal experimental conditions, a relatively low limit of detection down to 0.024 U/mL was achieved for fluorescence titration experiment. It was thanks to the better biocompatibility and low cytotoxicity, CS-βGal had been triumphantly employed to visual detect endogenous and exogenous β-Gal concentration variations in living cells with noteworthy anti-interference performance. More biologically significant was the fact that the application of CS-βGal in BALB/c nude mice was also achieved successfully for monitoring endogenous β-Gal enzyme activity.

Imaging gastrointestinal damage due to acute mercury poisoning using a mitochondria-targeted dual near-infrared fluorescent probe

Mercury (Hg) is one of the most widespread pollutants that pose serious threats to public health and the environment. People are inevitably exposed to Hg via different routes, such as respiration, dermal contact, drinking or diet. Hg poisoning could cause gingivitis, inflammation, vomiting and diarrhea, respiratory distress or even death. Especially during the developmental stage, there is considerable harm to the brain development of young children, causing serious symptoms such as intellectual disability and motor impairments, and delayed neural development. Therefore, it’s of great significance to develop a specific, quick, practical and labor-saving assay for monitoring Hg2+. Herein, a mitochondria-targeted dual (excitation 700 nm and emission 728 nm) near-infrared (NIR) fluorescent probe JZ-1 was synthesized to detect Hg2+, which is a turn-on fluorescent probe designed based on the rhodamine fluorophore thiolactone, with advantages of swift response, great selectivity, and robust anti-interference capability. Cell fluorescence imaging results showed that JZ-1 could selectively target mitochondria in HeLa cells and monitor exogenous Hg2+. More importantly, JZ-1 has been successfully used to monitor gastrointestinal damage of acute mercury poisoning in a drug-induced mouse model, which provided a great method for sensing Hg species in living subjects, as well as for prenatal diagnosis.

Construction of a turn-on fluorescent probe for detecting formaldehyde in biological systems and real food samples

The monitoring of formaldehyde (FA) in biosystems and real foods is critical for ensuring human health and food safety. However, the development of effective and highly selective assays for sensing FA in organisms and real food samples remains challenging. Herein, a hydrophilic group-modified the probe (Nap-FA) was reported, which utilizes the specific chemical reaction between FA and hydrazino to trigger a “turn-on” fluorescence response. The probe Nap-FA displayed superior selectivity, high sensitivity, good photostability and a low detection limit in the reaction with FA. Notably, Nap-FA has been successfully used for imaging FA in cells, zebrafish, and plant root tissues. In addition, the rationally constructed probe Nap-FA could rapidly and visually detect FA in real food samples. This work provides a prospective approach for monitoring FA in complex biological systems and food fields.

The carbon dots based on Nile red: The preparation and application to probe α-synuclein fibrils

The aggregation of α-synuclein often links to the occurrence and development of Parkinson’s disease (PD). It is crucial to detect the α-synuclein fibril or monitor the aggregation of monomer for pharmacological and pathological researches, drug development and clinical diagnosis, etc. In this study, the Nile red (NR)-based carbon dots (NR-CDs) were meticulously designed and prepared. The NR-CDs were sensitive to the microenvironment, exhibiting enhanced fluorescence intensity with the elevated viscosity and decreased polarity. Thus, the NR-CDs exhibited high affinity towards α-synuclein fibril with remarkable red fluorescence enhancement, but did not respond to its monomer. Hence, the NR-CDs were used as the turn-on fluorescence probe to detect and image α-synuclein fibrils both in vitro and in vivo, as well as to monitor the aggregation process of the amyloids. Superior to NR dye, NR-CDs were characteristic of lower toxicity, better water dispersibility and anti-photobleaching resistance. In addition, the NR-CDs were demonstrated to inhibit the aggregation of α-synuclein, holding the potential as the therapeutic agent. The present study provided an effective way of designing the CDs using the small molecular dye as the carbon source to improve the biocompatibility and detectability, while reserve the selective turn-on fluorescence towards amyloid aggregates. This strategy may be generalized to construct more fluorescence probes with desired properties.

Study on ESIPT process of fluorescence probe BT-ITC for detecting H2S in DMF/H2O mixed solution

A probe molecule named BT-ITC with an isothiocyanate group was synthesized and evaluated for its H2S sensing ability based on the excited state intramolecular proton transfer (ESIPT) process J K Kim, S Y Bong, R Park, J Park, D Ok Jang 2022 An ESIPT-based fluorescent turn-on probe with isothiocyanate for detecting hydrogen sulfide in environmental and biological systems, Spectrochimica Acta Part A 278 121333. The BT-ITC molecule has a large Stokes shift, short response time, and low detection limit. The end result of the reaction between the molecules BT-ITC and H2S is the BTC-NH2 molecule. The hydrogen bond of the Enol structure BTC-NH2 molecule in excited-state (S1 state) is strengthened, compared to the ground-state (S0 state). The calculated absorption and fluorescence spectra were in good agreement with the experimental values. The frontier molecule orbitals (FMOs), the potential energy curve (PEC), and scatter plots of reduced density gradient (RDG) were calculated. According to aforementioned, it was discovered that the charges of BTC-NH2 molecule were rearranged via an electron transition brought on by photoexcitation. This changes the acidity and alkaline of the proton donor and acceptor, and thus promotes the ESIPT process.

A turn-on fluorescence probe for imaging tyrosinase at the wound site in broken tail of zebrafish

Tyrosinase (TYR) is a copper-containing oxidase that affects the synthesis of melanin in the human body, which is regulate to the pigmentation of the skin. Nevertheless, abnormal expression of TYR can lead to albinism, vitiligo and other skin diseases. Excessive accumulation of TYR is a marker of melanoma cancer and an important factor leading to pigmentation during wound healing, freckles and browning of fruits and vegetables. Efficient tracking of TYR is of significance for studying its pathophysiological mechanism. Herein, we synthesized a benzindole-based fluorescent probe Pro-OH to detect TYR in living cells and zebrafish. The probe displayed a high selectivity and sensitivity in distinguishing TYR from other analytes with the low detection limit of 1.024 U/mL. Importantly, Pro-OH was successfully used to imagine TYR at the wound site of broken tail of zebrafish.

Live Cell Imaging and Real-Time Monitoring of Nucleolus Morphology and Mitophagy with a Red Fluorescent and Photostable rRNA-Specific Probe in Human Cancer Cells.

rRNAs are prevalent in living organisms. They are produced in nucleolus and mitochondria and play essential cellular functions. In addition to the primary biofunction in protein synthesis, rRNAs have been recognized as the emerging signaling molecule and drug target for studies on nucleolus morphology, mitochondrial autophagy, and tumor cell malignancy. Currently, only a few rRNA-selective probes have been developed, and most of them encounter the drawbacks of low water solubility, poor nuclear membrane permeability, short emission wavelength, low stability against photobleaching, and high cytotoxicity. These unfavorable properties of rRNA probes limit their potential applications. In the present study, we reported a new rRNA-selective and near-infrared fluorescent turn-on probe, 4MPS-TO, capable of tracking rRNA in live human cancer cells. The real-time monitoring performance in nucleolus morphology and mitochondrial autophagy is demonstrated in HeLa cells. The probe shows great application potential for being used as a rRNA-selective, sensitive, and photostable imaging tool in chemical biology study and drug screening.

A turn-on fluorescent probe based on benzothiazole for H2S detection and its multiple applications in water samples and food spoilage

Hydrogen sulfide (H2S) is a common hazardous gas, which is associated with environmental water pollution and food spoilage. Herein, a turn-on benzothiazole-based fluorescent probe (BATD) was synthesized for detecting H2S and characterized by single crystal X-ray diffraction, NMR and MS. BATD exhibited enhanced fluorescence signal at 600 nm with a remarked Stokes shift (145 nm), rapid response (within 90 s) and sensitivity (limit of detection, LOD = 76 nM) for H2S detection. The probe was significantly fluorescent enhancement in response to H2S over the other analytes. In addition, BATD was employed to detect H2S in water samples and monitor H2S gas generated from food spoilage. Benefiting from the excellent performance of the probe in recognizing H2S, a convenient H2S sensing platform for smartphones had been successfully established.

Development of a turn-on fluorescent probe for the imaging of intracellular hypochlorous acid (HClO) during ferroptosis

Ferroptosis is a burgeoning iron-dependent cell death form, and has close relation with hypochlorous acid (HClO). Exploring the fluctuation of the HClO level in living cells during ferroptosis could contribute to the profound study of the biological functions of HClO during ferroptosis. Here, we present a turn-on probe (RH-C) for the imaging of intracellular HClO during ferroptosis. The probe RH-C utilized the N,N-dimethylthiocarbamate group as a selective recognition site for HClO, and displayed desirable sensitivity and selectivity to HClO. The probe RH-C could detect the exogenous and endogenous HClO in living cells. Furthermore, RH-C was competent in monitoring the changes of endogenous HClO level during the process of ferroptosis. Biological imaging results suggested that erastin-induced ferroptosis can result in the excessive production of the endogenous HClO, and ferrostatin-1 (Fer-1) and vitamin E (VE) could block the massive accumulation of HClO in living cells.

Turn-On Fluorescent Probe for BSA Detection Constructed by Supramolecular Assembly.

The fluorescent probe method has attracted significant research attention due to its high sensitivity and reproducibility in detecting bovine serum albumin (BSA). In this study, we constructed a fluorescent probe for BSA detection by assembling an amphiphilic organic fluorescent molecule, termed 2-(2'-hydroxyphenyl) benzothiazole (HBT-11), with BSA. In an aqueous solution, HBT-11 exhibited a weak fluorescence emission at 501 nm. However, the addition of BSA substantially enhanced the fluorescence emission at 501 nm, indicating that the assembly was driven by electrostatic interactions between HBT-11 and BSA. HBT-11, serving as a fluorescent probe for BSA detection, demonstrated a limit of detection (LOD) as low as 3.92 nmol L-1, excellent photostability, high selectivity, and robust anti-interference capability. Notably, we successfully applied HBT-11 for detecting BSA in fetal bovine serum and selectively imaging BSA in HeLa cells.

A novel turn-on fluorescence sensor based on the Nd (III) complex for the ultrasensitive detection of 6-mercaptopurine

6-mercaptopurine (6MP) is a chemotherapeuticdrug widely used for treating inflammatory bowel diseases and several cancers. Nevertheless, determining and monitoring its concentration in the human body is highly important because over or under-doses of 6MP can lead to critical health issues. In this paper, we have developed a turn-on fluorescent probe for the determination of the anticancer drug 6-mercaptopurine (6-MP) based on coordination complex [Nd (Anth)3 (H2O)3]. [Nd (Anth)3 (H2O)3] has been synthesized through a simple precipitation process taking the stoichiometric ratio of Nd (III) nitrate hexahydrate and 2-aminobenzoic acid (2-ABA), commonly known as anthranilic acid (Anth). The synthesis and structure have been investigated and validated by different characterizations like UV–visible spectroscopy, FT-IR, HRMS, XPS, and SEM. The synthesized complex displayed excellent fluorescence properties, and the fluorescence intensity was enhanced with the addition of 6MP in the form of a [Fe (6MP)3]2+ mixed complex (Fe-6MP), which is formed by dissolving it in FeCl3. The fabricated sensors displayed the best linear response in a wide range of concentrations from 2.55 μM to 45.51 μM of 6MP. The lower limit of detection (LOD) of the developed sensor was found to be 0.26 μM with a linear correlation coefficient (R2) of 0.99. The synthesized probe gives an acceptable response for the sensing of 6MP in the presence of several interfering agents.

Development of an innovative turn-on fluorescent probe for targeted in-vivo detection of nitric oxide in rat brain extracts as a biomarker for migraine disease

Nitric oxide (NO) is one of the reactive nitrogen species (RNS) that has been proposed to be a key signaling molecule in migraine. Migraine is a neurological disorder that is linked to irregular NO levels, which necessitates precise NO quantification for effective diagnosis and treatment. This work introduces a novel fluorescent probe, 2,3-diaminonaphthelene-1,4-dione (DAND), which was designed and synthesized to selectively detect NO in-vitro and in-vivo as a migraine biomarker. DAND boasts high aqueous solubility, biocompatibility, and facile synthesis, which enable highly selective and sensitive detection of NO under physiological conditions. NO reacts with diamine moieties (recognition sites) of DAND, results in the formation of a highly fluorescent product (DAND-NO) known as 1H-naphtho[2,3-d][1,2,3]triazole-4,9-dione at λem 450 nm. The fluorescence turn-on sensing mechanism operates through an intramolecular charge transfer (ICT) mechanism. To maximize fluorescence signal intensity, parameters including DAND concentration, reaction temperature, reaction time and pH were systematically optimized for sensitive and precise NO determination. The enhanced detection capability (LOD = 0.08 μmol L−1) and high selectivity of the probe make it a promising tool for NO detection in brain tissue homogenates. This demonstrates the potential diagnostic value of the probe for individuals suffering from migraine. Furthermore, this study sheds light on the potential role of zolmitriptan (ZOLM), an antimigraine medication, in modulating NO levels in the brain of rats with nitroglycerin-induced migraine, emphasizing its significant impact on reducing NO levels. The obtained results could have significant implications for understanding how ZOLM affects NO levels and may aid in the development of more targeted and effective migraine treatment strategies.

Carbazole-alt-fluorene based π-conjugated Cu(II)-metallopolymer with pendent diketopyrrolopyrrole unit as highly selective and sensitive turn-on fluorescent probe for detection of amino acids

Highly emissive and soluble poly(carbazole-alt-fluorene) (P1) based π-conjugated alternative copolymers with thiophene-diketopyrrolopyrrole as pendent unit have been designed and synthesized via Pd(0)-catalyzed Suzuki coupling polymerization from the corresponding monomers 3,6-dibromo-9H-carbazol-3,6-di(thiophen-2-yl)pyrrolo[3,4-c]pyrrole and 2,7-bis-oxaborolan-9,9-dioctylfluorene. The well-defined copolymer P1 has been characterized by multinuclear NMR spectra as well as by tetradetector GPC showing molecular weight (Mn) of 15.6 kg/mol with the polydispersity indices of 1.38. The red emissive polymer has been explored for the detection of amino acids based on a secondary ‘‘turn-on’’ sensing approach. The thiophene-diketopyrrolopyrrole anchored carbazole-alt-fluorene copolymer shows high selectivity towards Cu2+ ions by changing the emission wavelength from red to blue due to the formation of the Cu(II)-metallopolymer (P1–Cu2+). The resulting metallopolymer P1–Cu2+ exhibits high sensitivity and selectivity towards amino acids over the other biologically relevant analytes. More importantly, the P1–Cu2+ metallopolymer exhibited higher sensitivity towards glycine, with the detection limit of 90 ppb (∼1.21 × 10−6 mol/L) along with relatively higher association constant of 2.55 × 108 M−1. To comprehend the sensing mechanism through photo-induced electron transfer (PET), the detailed photophysical studies have been carried out with P1 and its representative monomeric model compound M1. Furthermore, fluorescence anisotropy study has also been carried out to inspect the molecular interactions responsible for the sensing properties of P1–Cu2+ metallopolymer towards glycine.

A turn-on fluorescent probe for the detection of hydrogen sulfide and thiophenol in water and beer samples

Hydrogen sulfide (H2S) and thiophenol (PhSH) are toxic pollutants that can affect the quality and safety of food and water. It is of importance to detect these analytes. However, developing fluorescent probes that can selectively discriminate H2S and PhSH is challenging due to their similar reactivity. In this work, we reported a dual-functional probe N-(4-(benzo[d]thiazol-2-yl)phenyl)− 2,4-dinitrobenzenesulfonamide (NBT) that could synchronously and selectively respond to H2S and PhSH in different solvents. NBT exhibited high selectivity, a low detection limit (82.66 nM for H2S, 21.44 nM for PhSH), and a wide linear range (5–70 μM for H2S, 5–35 μM for PhSH). Therefore, NBT was successfully applied to detect H2S and PhSH in water and beer samples with excellent recovery and precision. This probe provides a simple and effective method for the simultaneous and quantitative detection of H2S and PhSH in water and beer samples without the need for sophisticated instruments.

A Turn-On Fluorescent Probe for Highly Selective Detection and Visualization of Hydrogen Sulfide in Fungi.

Hydrogen sulfide (H2S) is a significant actor in the virulence and pathogenicity of fungi. The analysis of endogenous H2S in fungi benefits the prevention and treatment of pathogenic infections. Herein, a H2S-activated turn-on fluorescent probe named DDX-DNP was developed for the sensitive and selective detection of H2S. Using DDX-DNP, the ability of several oral fungi strains to produce H2S was identified, which was also validated using a typical chromogenic medium. In addition, DDX-DNP was successfully used for the visual sensing of endogenous H2S in fungal cells via microscope, flow cytometry, and colony imaging, along with a specific validation with the co-incubation of H2S production inhibitors in living cells. Above all, DDX-DNP could be used for H2S detection, the fluorescent imaging of fungi, and even the identification of related fungi.

Highly selective near-infrared fluorescent turn-on probe with a large Stokes shift for the detection of hydrogen sulfide and imaging in live cells

The signalling molecules of hydrogen sulphide (H2S) play an important role in a variety of physiological and pathological processes, and its abnormal concentration causes Down's syndrome, Alzheimer's disease and diabetes mellitus. Thus, the development of an effective detection tool is of vital importance and challenge. In this paper, we synthesized a new “turn-on” hydrogen sulfide near-infrared fluorescent probe (DCM-H2S). Remarkably, this probe demonstrated an unanticipated level of selectivity for hydrogen sulfide (H2S) over other analytes, rendering it suitable for the precise determination of H2S in both in vitro and in vivo settings. Expectedly, the probe exhibited unexpectedly heightened selectivity for H2S compared to other analytes, making it a viable option for the specific determination of H2S in both in vitro and in vivo applications. With the addition of H2S, the probe exhibited distinct turn-on near-infrared (NIR) fluorescence intensity alterations in the DMSO/H2O system, together with a high sensitivity (LOD = 0.13 μM) and large Stokes shift (121 nm). More importantly, the probe has been successfully applied to bioimaging for real-time, dynamic tracking of exogenous and endogenous H2S. The outcomes showed that the probe (DCM-H2S) provides a rapid and effective detection tool for monitoring H2S in vivo.

Application and Cell Imaging of Turn-On Fluorescent Probe for Hydrogen Sulfide Based on Benzopyran in Food Samples

Application and Cell Imaging of Turn-On Fluorescent Probe for Hydrogen Sulfide Based on Benzopyran in Food Samples

Turn-on fluorescent probe based on dicyanoisophorone for bioimaging and rapid detection of peroxynitrite in aqueous media.

A novel dicyanoisophorone-based colorimetric fluorescent probe 3 has been prepared for recognizing peroxynitrite in aqueous conditions. A large bathochromic shift of the absorption band is observed upon titration with ONOO-, inducing a clearly visible solution color change from yellow to pale pink, which makes "naked-eye" detection possible. Moreover, probe 3 can react instantly with ONOO- and is accompanied by a significant fluorescence enhancement at 621 nm while the detection limit is as low as 37 nM. Most importantly, probe 3 exhibits high selectivity and sensitivity towards ONOO- in the presence of other competitive ions in aqueous solution. Probe 3 has also been successfully applied in living MCF-7 cells, and the results suggest that probe 3 could be applied as a potential candidate for the detection of ONOO-.