Fluorescence Turn-on Response Research Articles

Fluorescence Turn-on Detection of Perfluorooctanoic Acid (PFOA) by Perylene Diimide-Based Metal-Organic Framework.

A novel, water-stable, perylene diimide (PDI) based metal-organic framework (MOF), namely, U-1, has been synthesized for selective and sensitive detection of perfluorooctanoic acid (PFOA) in mixed aqueous solutions. The MOF shows highly selective fluorescence turn-on detection via the formation of a PFOA-MOF complex. This PFOA-MOF complex formation was confirmed by various spectroscopic techniques. The detection limit of the MOF for PFOA was found to be 1.68 μM in an aqueous suspension. Upon coating onto cellulose paper, the MOF demonstrated a significantly lower detection limit, down to 3.1 nM, which is mainly due to the concentrative effect of solid phase extraction (SPE). This detection limit is lower than the fluorescence sensors based on MOFs previously reported for PFAS detection. The MOF sensor is regenerable and capable of detecting PFOA in drinking and tap water samples. The PDI-MOF-based sensor reported herein represents a novel approach, relying on fluorescence turn-on response, that has not yet been thoroughly investigated for detecting per- and polyfluoroalkyl substances (PFAS) until now.

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.

A novel coumarin-linked tetraphenylethene fluorescent probe for simultaneous sensing of ATP and GSH

Adenosine triphosphate (ATP) as the intracellular energy currency, and glutathione (GSH) as the regulator of redox homeostasis in the cell microenvironment, are all closely associated with numerous important physiological processes in living organisms. However, the fluorescent probes that can simultaneously detect ATP and GSH are rarely reported. Herein, a bifunctional coumarin-linked tetraphenylethene (TPE) probe P1 was successfully developed, which exhibits a red emission at 633 nm owing to the fluorescence resonance energy transfer (FRET) from energy donor coumarin to energy acceptor TPE. P1 can detect ATP with a fluorescence turn-on response at 633 nm in the red channel by complexation-enhanced aggregation mechanism, and showed a ratiometric detection toward GSH through the disruption of the FRET process, accompanied by an increase in the blue channel at 467 nm and a decrease in the red channel at 633 nm. P1 also displays a superior sensitivity and high selectivity to ATP and GSH, with a detection limit of 20.80 nM for ATP and 3.47 µM for GSH. Significantly, P1 can discriminate GSH from ATP and other analytes due to the different response times. Furthermore, P1 can localize mitochondria and has been discovered to be capable of imaging ATP and GSH in living cells and zebrafish.

An Expanded Palette of Fluorescent COS/H2S-Releasing Donors for H2S Delivery, Detection, and In Vivo Application.

Hydrogen sulfide (H2S) is an important reactive sulfur species that is involved in many biological functions, and H2S imbalances have been indicated as a potential biomarker for various diseases. Different H2S donors have been developed to deliver H2S directly to biological systems, but few reports include donors with optical responses that allow for tracking of H2S release. Moreover, donor systems that use the same chemistry to deliver H2S across a palette of fluorescent responses remain lacking. Here we report five thiol-activated fluorescence turn-on COS/H2S donors that utilize blue, yellow, orange, red, and near infrared-emitting dyes functionalized with an H2S-releasing sulfenyl thiocarbonate scaffold. Upon treatment with thiols, each donor provides a fluorescence turn-on response (3-310-fold) and high H2S release efficiencies (>60%). Using combined electrode and fluorescence experiments, we directly correlate the measured H2S release with the fluorescence response. All donors are biocompatible and release H2S in live cell environments. In addition, we demonstrate that the NIR donor allows for imaging H2S release in live rats via subcutaneous injection of the donor loaded into an alginate gel, which to the best of our knowledge is the first in vivo tracking of H2S release from a fluorogenic donor in non-transparent organisms.

Water bridges as the trigger in an amino functionalized Zn-MOF for highly selective and sensitive fluorescent sensing of water

Water is a fundamental element for life. The highly selective and sensitive sensing of water is always attractive for mankind in activities such as physiological processes study and extraterrestrial life exploration. Fluorescent MOFs with precise channels and functional groups might specifically recognize water molecules with hydrogen-bond interaction or coordination effects and work as water sensors. As a proof of concept, herein, an amino functionalized Zn-MOF (named as complex 1) with pores that just right for water molecules to form hydrogen bond bridges is revealed for highly selective and sensitive fluorescent sensing of water. The single-crystal X-ray diffraction analysis indicates that the 3D framework of complex 1 is functionalized with free amino groups in the channels. Hydrogen bonds formed in the channel along b-axis as water bridges to connect two adjacent NH2bdc ligands and result in the restriction of intramolecular motions (RIM) which could responsible for the selective turn-on fluorescence response to water. Complex 1 exhibits high sensitive to trace amount of water in organic solvents and could be used for water detection in a wide range water contents. Take advantages of complex 1, portable sensors (complex 1@PMMA) were prepared and used in the highly sensitive water sensing.

D-A-D type based NIR fluorescence probe for monitoring the cysteine levels in pancreatic cancer cell during ferroptosis

Cysteine (Cys) as a crucial precursor for intracellular glutathione (GSH) synthesis, plays an important role in the redox regulation in ferroptosis, Therefore, evaluating intracellular Cys levels is worthy to better understand ferroptosis-related physiological process. In this work, we constructed a novel NIR coumarin-derived fluorescent probe (NCDFP-Cys) based on a dual-ICT system, the NCDFP-Cys can show fluorescence turn-on response at 717 nm toward Cys over other amino acids, and possess large Stokes shift (Δλ = 167 nm), low detection limit, hypotoxicity. More significantly, NCDFP-Cys has been utilized to monitor the intracellular Cys fluctuation in pancreatic cancer cells during ferroptosis induced by Erastin and RSL3 respectively, and revealing the difference of Cys levels changes in different activator-triggered ferroptosis pathways.

A difunctional fluorescent probe to detect hypochlorite and hydrogen sulfide ions in ferroptosis and oxidative stress induced by Aspirin

HOCl and H2S frequently coexist in living cells and work in concert to maintain the redox dynamic balance in vivo. It is challenging to precisely and simultaneously trace both HOCl and H2S using a single recognition-type fluorescence probe. Here, a novel fluorescent probe (MB-HS) for the selective detection of hydrogen sulphide (H2S) and hypochlorous acid (HOCl) has been established based on the coupling of the methylene blue fraction and the indolium fraction. For HOCl, the dual-signal probe MB-HS displays quick turn-on fluorescence responses. However, for H2S, it exhibits turn-off fluorescence at 586 nm and turn-on at 513 nm, respectively. MB-HS showed many advantages such as quick response, strong selectivity, and high sensitivity. It was effectively used to detect endogenous HOCl/H2S in ferroptosis and oxidative stress induced by Aspirin in HepG-2 cells.

Aggregation-induced emission activity of sensor TBM-C1 hybrid of methoxy-triphenylamine (OMe-TPA) and dicyanovinyl for cyanide detection in aqueous THF: Mechanistic insights and potential applications

A series fluorescent probes (TBM-Cx (x = 1, 4, 8)) were designed based on embedding various alkoxy chains on the electron donor of triphenylamine (TPA)-based dicyanovinyl (MT) compound with an electron-deficient benzothiadiazole (BTD) for sensitive, selective, and visualizing detection of cyanide in aqueous solution. Due to the nucleophilic addition of CN−, the intramolecular charge transfer (ICT) of these probes was inhibited by the destroyed conjugated structure, exhibiting excellent “turn-on” fluorescence response toward cyanide anion (CN−) in tetrahydrofuran (THF). However, the alkoxy chains with different lengths embedded in TPA not only enhance the sensitivity and solubility, but also regulate the emission behavior from ICT to aggregation-induced emission (AIE) characteristics. The binding mechanism and AIE sensing performances between the probes and CN− have been investigated and compared in THF/water mixture by spectral tools and theoretical calculations. The results showed that the ICT-based TBM-C1 probe with methoxy chain showed significantly turn-on fluorescence response to CN− as low as 0.077 μM in THF/water solution at high water fraction (90 %). Due to the AIE sensing process, TBM-C1 was successfully employed to determine CN− in food and water samples, image CN− in living cells and BALB/c mice, and prepare test kits for visualizing cyanide.

A chromogenic anthraimidazoldione probe for ratiometric analysis of Hg2+ exclusively at mesoscopic interface: Screening of real-life biological samples

In the present work, we have synthesized amphiphilic anthraimidazoldione derivative that can form nanoassembly in the aqueous medium. The π-conjugated backbone with facile intramolecular charge transfer from the substituted aryl residue to anthraquinone unit attributed to the profound orange color. Despite having the metal ion chelating aminoethyl acetamide unit, the compound showed no interaction with metal ions in the aqueous medium. However, a highly selective color-changing response, from orange to yellow (Δλ ∼52 nm), was observed upon addition of Hg2+ ion at micellar interface. Also, a turn-on fluorescence response (∼5.2-fold) was witnessed with Hg2+. It was observed that in addition to hydrophobic microenviroment, the orientation of molecules at water-surfactant interface also responsible for the chromogenic response towards Hg2+ ion. The mechanistic investigation indicated that Hg2+ ion coordinates with the aminoethyl acetamide unit, resulting restriction in the extent of intramolecular charge transfer. Considering such highly ratiometric response, the present system has been employed for analysis of Hg2+ ion in diluted urine and blood serum samples. The high recovery values (95.4 % to 104.3 %) with relatively low standard deviations (< 4.2 %) indicated that the present system is fairly successful in screening of complex real-life samples. Finally, we have designed low-cost, reusable, chemically modified paper strips for on-location, rapid analysis of mercury ions.

Development of a solid-supported light-triggered nitric oxide donor

Nitric Oxide (NO) photocleavable donors are useful tools for interrogating nitric oxide signalling and have potential use in photopharmacological applications. There is currently intensive research into newer methods to improve NO release and kinetic profiles. Herein, we report the design and synthesis of a solid-supported photocleavable NO donor synthesized by ligating an N-nitroso photocleavable nitric oxide derivative to a TentaGel® polymer resin bead. Illumination with 365 nm light released nitric oxide that could be tracked via a turn-on fluorescence response (λex = 450 nm, λem = 545 nm) and measured using the Griess assay and diaminorhodamine derivatives. These beads were further shown to be compatible with living A549 cells and had the ability to deliver greater concentrations of nitric oxide to cells proximal to a bead versus cells at more distal locations within the same well.

Surfactant-induced alterations in optoelectronic properties of perylene diimide dyes: modulating sensing responses in the aqueous environment.

The compartmentalization effect of microheterogeneous systems, like surfactant aggregates, showcases altered optoelectronic properties of a perylene diimide-based chromogenic dye (PDI-Ala) compared to bulk water. The relatively hydrophobic microenvironment, poor hydration, and exceptionally large local concentration of dye molecules in the confined environment affect their interaction with target analytes. This realization intrigued us to investigate if micellization can modify the sensing properties (selectivity, sensitivity, response kinetics, output signal, etc.) of the encapsulated dye molecules in the aqueous medium. Response comparisons of PDI-Ala to the ionic analyte (Fe3+) and biomolecule (heparin) in aqueous and surfactant-bound states highlighted significant variations. Fe3+ interaction exhibited a "turn-off" fluorescence response in a water medium, while surfactant-bound conditions triggered "turn-on" fluorescence, enhancing selectivity at the micelle-water interface. Conversely, the native probe showed no interaction with heparin in water but displayed a turn-on fluorescence response in cetyltrimethylammonium bromide (CTAB) micelles, indicating the transformation of a silent molecule into a turn-on fluorescence sensor. This study underscores the influence of micellar environments on dye molecules, altering the sensing responses and selectivity toward analytes, crucial for applications in understanding cellular pathways and toxicity mechanisms.

A highly sensitive fluorescence probe for on-site detection of nerve agent mimic diethylchlorophosphonate DCP.

Nerve agents are the most toxic chemical warfare agents that pose severe threat to human health and public security. In this work, we developed a novel fluorescent probe NZNN based on naphthylimide and o-phenylenediamine to detect nerve agent mimic diethylchlorophosphonate (DCP). DCP underwent a specific nucleophilic reaction with the o-phenylenediamine group of NZNN to produce a significant fluorescence turn-on response with high selectivity, exceptional linearity, bright fluorescence, rapid response (<6 s) and a low detection limit (30.1 nM). Furthermore, a portable sensing device was fabricated for real-time detection of DCP vapor with excellent performance. This portable and sensitive device is favorable for monitoring environmental pollution and defense against chemical warfare agents.

Real-Time Live Imaging of Osteoclast Activation via Cathepsin K Activity in Bone Diseases.

Intravital fluorescence imaging of functional osteoclasts within their intact disease context provides valuable insights into the intricate biology at the microscopic level, facilitating the development of therapeutic approaches for osteoclast-associated bone diseases. However, there is a lack of studies investigating osteoclast activity within deep-seated bone lesions using appropriate fluorescent probes, despite the advantages offered by the multi-photon excitation system in enhancing deep tissue imaging resolution. In this study, we report on the intravital tracking of osteoclast activity in three distinct murine bone disease models. We utilized a cathepsin K (CatK)-responsive two-photon fluorogenic probe (CatKP1), which exhibited a notable fluorescence turn-on response in the presence of active CatK. By utilizing CatKP1, we successfully monitored a significant increase in osteoclast activity in hindlimb long bones and its attenuation through pharmacological intervention without sacrificing mice. Thus, our findings highlight the efficacy of CatKP1 as a valuable tool for unraveling pathological osteoclast behavior and exploring novel therapeutic strategies.

A practical chromogenic and fluorogenic dual-mode sensing platform for rapid quantification of sulfite in food

Sulfur dioxide (SO2) and its derivatives (HSO3− and SO32−) are widely used in food-processing. Whereas excessive consumption of sulfur dioxide and its derivatives (>0.70 mg·kg−1day−1) severely endangers human health. In this work, we rationally constructed a practical dual-mode probe (dicyanomethylene)-1-methyl-1,4-dihydroquinolin-2-yl)vinyl)-1-methylquinolinium (QMN), which underwent a specific 1, 4-Michael addition with sulfite to afford a noticeable color change from pale yellow to red along with a high-contrast fluorescence turn-on response at 598 nm. QMN has the advantages of rapid response, high signal-to-noise ratio, excellent selectivity, good water-solubility, large Stokes shift and low detection limit (LOD = 31.9 nM). QMN has been successfully used to on-site visually determine sulfite in a diversity of foods with satisfactory recoveries (91.33–111.33 %) and high accuracy (93.74–98.71 %). Furthermore, a portable smartphone-based fluorescence sensing platform was fabricated for on-site determination of sulfite in food with good performance.

Ferrocene appended highly ICT based molecular sensor for Mg(II) ion: Application for bio-imaging and TLC strip studies

Qualitative and quantitative analysis of magnesium at concentration levels as low as parts per billion (ppb) is a basic, fundamental and practical concern. The present study displays the design and synthesis of a novel specific receptor (E)-3-((2-hydroxynaphthalen-1-yl)methylene)amino)-2-ferrocenyl-2,3-dihydroquinazolin-4(1H)-one (HnFQz) for selective recognition of Mg(II). The HnFQz shows turn-on fluorescence response from colorless to yellowish green after treatment with Mg(II) at λmax. 499 nm in aqueous acetonitrile. The experimental findings were well supported by theoretical results. The ESI-MS spectrometry and the Job’s experimental results confirm the formation of 1:1 complex between HnFQz and Mg(II). Further study demonstrates the detection limit and association constant of HnFQz for Mg(II) and were found to be 23.24 nM and 1.48 × 107 M−1 respectively. The practical application of receptor towards recognition of Mg(II) was explored through economically viable test strips and bio-imaging studies. The excellent outcome of present research suggests that the receptor HnFQz could act as an efficient Mg(II) test kit.

Intramolecular cascade reaction sensing platform for rapid, specific and ultrasensitive detection of nitrite

Nitrite is a carcinogenic substance in food. Excessive consumption of nitrite severely endangers human health. However, rapid and accurate quantification of nitrite by a simple tool is still very challenging. In this work, we designed a practical sensing platform based on 8-(o-phenylenediamine)-boron dipyrromethene (BDP-OPD) to determine nitrite in food. BDP-OPD can take a specific diazotization-cyclization cascade reaction with nitrite to form boron dipyrromethene (BODIPY), giving rise to a remarkable chromogenic reaction along with high contrast fluorescence turn-on response towards nitrite. BDP-OPD has high sensitivity, rapid response, and good selectivity. Furthermore, a portable smartphone-based fluorescence device integrated with a self-programmed Python program was fabricated, which has been successfully used to determine nitrite in food with the advantages of rapid response, low cost, ease of operation, portability, and satisfactory recoveries (92–112%). The good sensing performance rendered BDP-OPD a promising fluorescence platform for on-site visual detection of nitrite.

Robust Optical Detection of Ga3+ by a Rhodamine- and Coumarin-Based Proficient Probe: Theoretical Investigations and Biological Applications.

The present investigation highlights a rhodamine-B- and coumarin-based efficient probe that selectively detects Ga3+ over other metal ions. The active pocket of the ligand for trapping the metal ions and the binding stoichiometry of its Ga3+ complex were discovered by single-crystal X-ray diffraction (SC-XRD) analysis. This binding stoichiometry was further confirmed in the solution state by mass spectrometry and Job's plot. The detection limit was found to be at the nanomolar level. Pyrophosphate being a well-known quencher could easily quench the fluorescence intensity of the RC in the presence of Ga3+ and reversibly recognize Ga3+ in the solution. The spiro ring opening of the ligand after Ga3+ insertion is proposed to be the principal mechanism for the turn-on fluorescence response. This ring opening was confirmed by SC-XRD data and nuclear magnetic resonance (NMR) titration experiments. Both ground- and excited-state calculations of the ligand and complex have been carried out to obtain information about their energy levels and to obtain the theoretical electronic spectra. Furthermore, the live-cell imaging of the probe only and the probe after the addition of Ga3+ have been carried out in HaCaT cells and satisfactory responses were observed. Interestingly, with the help of this probe, Ga3+ can be tracked inside the intracellular organelle such as lysosomes along with other regions of the cell. The article highlights a rhodamine-coumarin-based probe for the detection of Ga3+ over other metal ions with a nanomolar level detection limit. Structural characterization of the ligand and its Ga3+ complex was investigated by SC-XRD. Density functional theory (DFT) and time-dependent DFT (TD-DFT) studies were carried out to explore the excited-state energies and electronic spectra. The application of the probe for the detection of Ga3+ in live cells has been explored, and positive responses were observed.

A selenium-based fluorescent probe for the sensitive detection of hypochlorous acid and its application in cell and zebrafish imaging

Hypochlorous acid (HOCl) is a significant reactive oxygen species within biological systems, and its anomalous metabolism has been linked to a range of diseases. Therefore, it is crucial to track and monitor the concentration of HOCl in living organisms to understand its biological functions and study its pathogenic mechanisms. In this study, we developed a photoinduced electron transfer (PeT) mechanism-based benzo-fused bodipy fluorescence probe, named BBy-Se, for highly sensitive and selective detection of HOCl in aqueous solutions. BBy-Se demonstrated a good turn-on fluorescence response to HOCl by specifically oxidizing the selenium atom. It exhibited significant Stokes shift (82 nm), low detection limit (10.9 nM) and rapid response (less than 10 s). Furthermore, the probe was successfully employed for real-time fluorescence imaging of HOCl in living HeLa cells and zebrafish, as demonstrated by the bioimaging results. The development of BBy-Se presents a new approach to explore the biological roles of HOCl and offers a valuable tool for studying its function in diseases.

Nanomolar detection of hypochlorite in ground water samples by a norbornene-based polymeric sensor via unusual fluorescence turn-on response

Hypochlorite anion has been widely used as a bleaching and disinfecting agent in daily life. Selective and sensitive identification ofOCl-ions from water is very important for researchers. For this purpose, monomeric (NPh), and polymeric (PNPh-Peg) novel fluorescent sensors have been established for the specific and excellently unique sensors that exhibit selective characteristics like excellent resistance to bleaching and a high fluorescence brightness. A multi-functional random polymer (PNPh-Peg) with ICT (intramolecular charge transfer) active para–amino phenol functionality and reactive oxygen species (ROS) responsive, PEG attached are readily prepared via ROMP (ring-opening metathesis polymerization).: An ICT-active random polymer (PNPh-Peg) exhibited an unexpectedly strong cyan blue emission in a water medium compared to that in other common organic solvents, which was dramatically increased by adding a trace amount of NaOCl.: Incorporating PEG moiety in the polymeric backbone increases the water solubility of a copolymer, and the ROS-responsive groups make the polymer a good ROS scavenger. Upon oxidation of the phenol group into carbonyl, both the monomeric (NPh) and polymeric (Norp-PEG oh) sensors showed a selective, noticeable, unusual fluorescence turn-on response towardsanalyteOCl-ions with a very fast response (within three minutes). The detection limit (59.14 nM) and (126.93 nM) were calculated for monomeric and polymeric sensors, respectively. This was a selective, specific oxidation reaction of the completely water-soluble random polymeric sensor (PNPh-Peg) for hypochlorite anions and can be applicable for quantitative measurement of aqueous OCl-. This ICT-active random polymeric molecule (PNPh-Peg) can also be used as a fluorescent sensor for unique OCl- detection from contaminated water by preparing a sensor-coated paper strip. Thus, these multi-functional monomeric (NPh) and polymeric (PNPh-Peg) sensors are anticipated to apply to the environment.

A coumarin-based multifunctional chemosensor for Cu2+/Al3+ as an AD theranostic agent: Synthesis, X-ray single crystal analysis and activity study

The pathogenesis of Alzheimer's disease (AD) is complex. So far there is no effective drug to treat the disease. The pathological changes of AD began 30 years before symptoms, so early diagnosis is considered to be important for AD treatment. Integrating diagnosis and therapy into a single regent has provided a new opportunity for AD treatment. Given that metal dyshomeostasis is thought to be one of the key factors to cause AD, a Schiff base substituted coumarin (probe 1) has been designed and synthesized as a selective metal chelator for multi-factor anti-AD in this work. The results of metal ions recognition showed that probe 1 had high selective fluorescent turn-on response to Al3+ and fluorescent turn-off response to Cu2+, due to intramolecular charge transfer (ICT) mechanism. Meanwhile, the results of both in vitro and in vivo bioactivities evaluation including metal chelation, reactive oxide species (ROS) elimination, self-/Cu2+-induced Aβ aggregation showed that 1 and 1-Cu(II) complex had excellent synergistic anti-AD activities. In addition, 1 had low cytotoxicity and was predicted to cross the blood-brain barrier (BBB). Noticeably, X-ray single crystal diffraction of 1-Cu(II) provided molecular level information to explain the structure and theranostic activity relationship. To sum up, 1 may be a promising candidate for the development of AD theranostic agent.