Selective Turn-on Fluorescence Research Articles

Selective and sensitive fluorescence turn-on detection of bilirubin using resorcinol-sucrose derived carbon dot

Carbon dots have been prepared from resorcinol and sucrose (rsCDs) hydrothermally, which show green emission at 525 nm with a fluorescence quantum yield (PLQY) of 17.2%. The intense emission of rsCDs is quenched upon the addition of Cu2+. In the presence of bilirubin (BR), the emission intensity is enhanced due to the competitive binding of Cu2+ with bilirubin and hence releasing rsCDs to the sensing medium. It is the first time report on turn-on fluorescence sensing towards BR with a detection limit of 85 nM. Even in the presence of other comparable biomolecules, the sensor is selective and ultrasensitive to bilirubin. A cellulose paper-based sensor strip has also been designed for the naked-eye detection of BR in blood serum. Due to the specific recognition of this rsCDs towards BR, it can be applied to detect BR in practical human serum samples.

Selective and sensitive investigation of aluminium contamination from cookware based on novel water-soluble fluorescence turn-on chemosensor

The ubiquitous use of aluminium cookware raises serious concerns about the introduction of aluminium by leaching upon prolonged cooking, especially in acidic foods. To mimic a consumer-relevant exposure scenario, an experimental model design was conceptualized for the estimation of leaching from aluminium sheets in acidic additives under variable cooking conditions. A novel water-soluble receptor (Z)-2-((2-hydroxy-3-methoxybenzylidene)amino)-2-(hydroxymethyl)propane-1,3-diol (VT) was synthesized, which gave a selective and sensitive fluorescence turn-on response towards aluminium ions. The 1:1 binding stoichiometry between VT and Al3+ has been confirmed by Job's plot, which is further supported by 1H NMR, 27Al NMR, HRMS, and DFT studies. Test strips were fabricated for quick semi-quantitative estimation of aluminium ions under UV irradiation. Leaching studies show that on increasing the acidity of solution of acidic additives results in an increased aluminium leaching ranging from 4.95 to 11.43 mg/h. Surface morphology by SEM and AFM shows the pitting corrosion of Al sheets.

Synthesis, Characterization and Applications of Schiff Base Chemosensor for Determination of Cr(III) Ions.

The development of a highly sensitive, selective, and efficient sensor for the determination and detection of Cr(III) ions remains a great challenge. Recently, some fluorescent chemosensors have been developed for the recognition of Cr(III) ions. But, the main drawbacks of the reported fluorescent chemosensors are the lack of selectivity and interference of anions and other trivalent cations. Herein, we designed and synthesized a novel thiazole-based fluorescent and colorimetric Schiff base chemosensor SB2 for the detection of Cr(III) ion by chemodosimetric approach. Using different analytical techniques including UV-vis, 13C-NMR, 1H-NMR, and FT-IR analysis the chemosensor SB2 was structurally characterized. The fully characterized chemosensor SB2 was used for the spectrofluorimetric and colorimetric detection of Cr(III) ions. Interestingly, chemosensor SB2 upon interaction with various metal cations including Ni2+, Na+, Cd2+, Ag+, Mn2+, K+, Zn2+, Cu2+, Hg2+, Co2+, Pb2+, Mg2+, Sn2+, Al3+ and Cr3+ displays highly selective and sensitive fluorescent (turn-on) and colorimetric (yellow to colorless) response toward Cr(III) ions. The fluorescence and UV-vis techniques confirmed the selective hydrolysis of azomethine group (-C = N-) of Schiff base chemosensor SB2 by Cr(III) ions. As a result, the fluorescence enhancement was observed that is corresponding to 2-hydroxy-1-nepthaldehyde (fluorophore). The chemosensor SB2 exhibits high interference performance towards Cr(III) ions over other metal cations in a wide pH range. Mover, the quite low detection limit was calculated to be 0.027µgml-1 (0.5µM) (3σ/slop), lower than the maximum tolerable limits of Cr(III ions (10µM) in drinking water permitted by the United States Environmental Protection Agency (EPA). These results show that chemosensor SB2 has great potential to detect selectively Cr(III) ions in the agricultural, environmental and biological analysis system.

New Schiff base probe for the fluorometric turn-on sensing of Cd2+ ions and bio-imaging application

We report herein a new 4-Cyanobiphenyl-based Schiff base probe, BPC for efficient fluorometric detection of highly hazardous Cd2+ ions. BPC can sense Cd2+ through selective turn-on fluorescence responses in CH3CN/H2O (3:2, v/v; Tris-HCl, pH = 7.4) solution. The 1:1 complex formation between BPC and Cd2+ could block both isomerization of CN and excited-state intramolecular proton transfer (ESIPT) process and meanwhile enhance the molecular rigidity, resulting in chelating enhanced fluorescence (CHEF). The detection limit (10.5 nM) is lower than the WHO drinking water standard (26.7 μM), which renders BPC a likely candidate for sensing of Cd2+ ions in neutral aqueous media. The analytical applicability of BPC for Cd2+ has been tested on the test paper strips. In addition, BPC was applied to image Cd2+ in living HeLa cells and zebrafish.

Supramolecular modulation in photophysical features of berberine and its application towards ATP sensing

In this study we report supramolecular interaction of the cationic dye berberine (BBR) with the highly substituted polyanionic cyclodextrin derivative, sulfobutylether beta cyclodextrin (SBE10βCD). Though interaction of BBR with parent β-cyclodextrin (βCD) host is very weak, its interaction with SBE10βCD host is significantly strong with an association constant Ka as large as ∼2.67 × 105 M−1. Strong binding of BBR with SBE10βCD is governed by cooperative effect of electrostatic attraction and enhanced hydrophobic interaction caused by extended SBE10βCD cavity for bound BBR dye. In the BBR-SBE10βCD complex, lower micropolarity and rigid microenvironment of host cavity cause a large decrease both in structural agility and intramolecular charge transfer (ICT) state formation of bound BBR. Accordingly, the non-radiative de-excitation of excited BBR in the dye-host complex is reduced significantly, causing its emission intensity to increase quite largely. The BBR-SBE10βCD complex is found to be highly sensitive towards ionic strength of the medium. This property is further explored to form a ternary complex, BBR-SBE10βCD-Cd2+, with largely reduced fluorescence intensity. Interestingly, this ternary complex exhibits selective fluorescence turn-on in response to an important bio-analyte, adenosine triphosphate (ATP). Present study, thus, demonstrates a very strong supramolecular complex, BBR-SBE10βCD, which is found to be very useful in the ATP detection in the presence of Cd2+, involving the ATP responsive fluorescence.

Target-Binding Accelerated Response for Sensitive Detection of Basal H2O2 in Tumor Cells and Tissues via a Dual-Functional Fluorescence Probe.

Aberrant production of H2O2 is involved in cancer. The levels of H2O2 are significantly higher in tumor cells than in normal cells. It is important to develop fluorescent probes to image basal H2O2 selectively in tumor cells. So far, a cancer cell-targeting probe to image basal H2O2 has not been reported. Thus, we developed a fluorescent probe, BBHP, which contains benzil as a H2O2-recognition site and biotin as a target binding motif for the selective and sufficient detection of H2O2 in tumor cells. BBHP enables a selective fluorescence turn-on response to H2O2. The binding of the probe with biotin receptors can greatly accelerate the fluorescence response to H2O2. As a result, BBHP can sufficiently image basal H2O2 in biotin receptor-positive cancer cells and tumor tissues. Finally, BBHP was successfully applied to discriminate between cancerous and normal tissues.

An easy to make Hg(II) complex as a selective and sensitive fluorescent turn-on chemosensor for iodide in an aqueous solution based on metal ion displacement mechanism

• The rationally designed receptor forms Hg(II) complex easily. • The Hg(II) complex senses I − via turn-on fluorescent in aqueous solution. • The mechanism of sensing involves displacement of metal ion from the complex. • This complex exhibited many advantages than similar in-situ generated Hg(II) complexes. A simple Schiff base ligand ( L ) bearing 3,5-dibromo-2-hyrdoxybenzaldehyde fluorophore moiety has rationally been designed, synthesized and characterized. The Hg(II) complex of L has been synthesized by simply stirring a mixture of L and HgCl 2 in ethanol at RT and the resultant non-fluorescent complex HgL is found to detect iodide ion selectively, with a turn-on fluorescence in H 2 O:DMSO (1:1 v/v) medium. The detection of iodide is performed via the metal ion displacement mechanism with a 1:2 (Probe:Iodide) stoichiometry and binding constant of 1.51x10 4 M −1 . The results indicated that novel HgL complex showed rapid response towards iodide ion with a limit of detection (LOD) as low as 60 nM. Moreover, the sensing mechanism of iodide by the complex is theoretically supported by density functional theory (DFT) and time dependent density functional theory (TD-DFT) calculations. In addition, estimation of iodide in real water samples, table salt and urine sample demonstrate the practical value of the probe.

Controlled and Selective Photo-oxidation of Amyloid-β Fibrils by Oligomeric p-Phenylene Ethynylenes.

Photodynamic therapy (PDT) has been explored as a therapeutic strategy to clear toxic amyloid aggregates involved in neurodegenerative disorders such as Alzheimer's disease. A major limitation of PDT is off-target oxidation, which can be lethal for the surrounding cells. We have shown that a novel class of oligo-p-phenylene ethynylenes (OPEs) exhibit selective binding and fluorescence turn-on in the presence of prefibrillar and fibrillar aggregates of disease-relevant proteins such as amyloid-β (Aβ) and α-synuclein. Concomitant with fluorescence turn-on, OPE also photosensitizes singlet oxygen under illumination through the generation of a triplet state, pointing to the potential application of OPEs as photosensitizers in PDT. Herein, we investigated the photosensitizing activity of an anionic OPE for the photo-oxidation of Aβ fibrils and compared its efficacy to the well-known but nonselective photosensitizer methylene blue (MB). Our results show that, while MB photo-oxidized both monomeric and fibrillar conformers of Aβ40, OPE oxidized only Aβ40 fibrils, targeting two histidine residues on the fibril surface and a methionine residue located in the fibril core. Oxidized fibrils were shorter and more dispersed but retained the characteristic β-sheet rich fibrillar structure and the ability to seed further fibril growth. Importantly, the oxidized fibrils displayed low toxicity. We have thus discovered a class of novel theranostics for the simultaneous detection and oxidization of amyloid aggregates. Importantly, the selectivity of OPE's photosensitizing activity overcomes the limitation of off-target oxidation of traditional photosensitizers and represents an advancement of PDT as a viable strategy to treat neurodegenerative disorders.

Simple and efficient synthesis of purple-red carbon spheres and construction of fluorescence resonance energy system for hypochlorite detection

A new type of purple-red carbon sphere was synthesized by efficient and convenient methods, which was designed as a colorimetric and fluorescent probe for the detection of hypochlorite, further expanding the application range of carbon spheres. This rare purple-red carbon sphere has a relatively long absorption wavelength, facilitating the design of a highly sensitive fluorescent probe through the energy transfer mechanism. When the probe reacts with hypochlorite, the purplish red color of the carbon ball fades, thus preventing the energy transfer process. More importantly, the alkaline environment provided by hypochlorite also further increases the fluorescence intensity, which was verified by density functional theory (DFT). Finally, a highly selective and ultrafast fluorescent turn-on and colorimetric probe was designed for the detection of hypochlorite in tap water.

Stable terbium metal-organic framework with turn-on and blue-shift fluorescence sensing for acidic amino acids (L-aspartate and L-glutamine) and cations (Al3+ and Ga3+).

A terbium-based metal-organic framework, namely {[Tb2(ADIP)(H2ADIP)(HCOOH)(H2O)2]·2DMF·2H2O}n (Tb-MOF, H4ADIP = 5,5'-(anthracene-9,10-diyl) diisophthalic acid), was synthesized and characterized. The single-crystal structure analysis shows that the Tb-MOF crystallizes in the C2/C space group in the monoclinic system and its asymmetric unit contains two TbIII ions, one ADIP4-, one H2ADIP2-, one coordinating formic acid and two coordination water molecules. Tb-MOF has a three-dimensional porous structure with a porosity of 41.5%. Tb-MOF is a highly selective and sensitive fluorescence turn-on and blue-shift sensor for L-aspartate (Asp), L-glutamine (Glu), Al3+ and Ga3+with detection limits of 0.25, 0.23, 0.069 and 0.079 μM, respectively. Experimental studies and theoretical calculations show that the sensing process is mainly attributed to the energy transfer and the absorbance caused enhancement (ACE) mechanism. Therefore, Tb-MOF is a good multi-response fluorescence sensor for acidic amino acids and Al3+, Ga3+cations.

A Selective Fluorescent Turn-On Probe for Imaging and Activity-Based Sensing of Hydrogen Peroxide in Living Cells

A Selective Fluorescent Turn-On Probe for Imaging and Activity-Based Sensing of Hydrogen Peroxide in Living Cells

Molecular phosphonic acid-tethered tetraphenylethene AIEgen based highly selective fluorescent turn-on sensor for neomycin

We demonstrated highly selective and sensitive tetraphenylethene -tetraphosphonic acids for the facile detection of aminoglycoside antibiotic neomycin for the first time. Neomycin was found to effectively induce aggregate formation of (4-(1,2,2-tris(4-phosphonophenyl)vinyl)phenyl)phosphonic acid octasodium salt (TPPE) in aqueous solution. The aggregation-induced emission (AIE) response of TPPE was realized upon addition of neomycin in Milli-Q water at pH 7. The detection mechanism relies on electrostatic and hydrogen bonding interactions. The TPPE-based sensor system exhibited a detection limit 2.088 × 10−10 M of neomycin. Further, we demonstrate use of TPPE system for visual detection of neomycin as thin layer chromatography (TLC) sensor to develop kits for real world applications.

An indolinium-based chemo-dosimeter for highly selective dual-channel detection of cyanide ion: A combined experimental and theoretical investigations

A new highly selective fluorescent turn-on probe (RS4) possessing indolinium moiety has been designed and synthesized for the detection of cyanide ion. The probe RS4 displays instantaneous, highly selective and sensitive recognition of cyanide ion over other common anions via change in color and enhancement in fluorescence. Nucleophilic addition of cyanide to the indolinium C-atom leads to the enhancement in fluorescence (λem 481 nm; Blueish-green emission) and decolourization due to different intramolecular charge transfer (ICT) process. The binding constant of the 1:2 RS4/CN¯ adduct is determined to be 2.3 × 104 M−1. The limit of detection of cyanide by RS4 is estimated to be 21 nM. Density functional theory (DFT) based calculations strongly substantiate the results of the experimental investigations. Importantly, the probe detects cyanide ion in agro-products (cassava powder and bitter almond), which demonstrates its value to practical application.

A highly selective turn-on fluorescence probe with large Stokes shift for detection of palladium and its applications in environment water and living cells

Nowadays, palladium has been widely used in many fields, which facilitates all aspects of our life. However, it may cause water and soil pollution and bring irreversible damage to the environment and organisms. Developing a fluorescence probe for rapid, highly sensitive and selective detection of palladium is still a poser. In this work, we designed and synthesized a novel fluorescence probe (RHS) for specific detection of palladium. Based on Pd0-mediated Tsuji-Trost reaction, the fluorescence probe was constructed by a rhodol derivative as thefluorophore and an allyl carbonate moiety as the specific palladium reactive site. The probe displayed excellent properties for detecting palladium, such as high selectivity and sensitivity, rapid response (20 min) and large Stokes shift (155 nm). The detection limit was determined to be as low as 0.140 μM with a linear range from 20 to 80 μM. After addition of palladium in RHS solution, the color of the solution turned from yellow to blue, indicating palladium could be monitored by the naked eyes. Moreover, probe RHS was successfully applied to palladium detection in environmental water samples. Importantly, with low cytotoxicity and good biocompatibility, the probe could monitor palladium in living cells.

Water-ratio directed selective turn-on fluorescence detection of copper and mercury in acetonitrile

The development of novel sensor probes to sensitively and selectively detect more than one target ion in a given condition is a challenging duty due to the deficiency of effective design strategies. In this study, we report utilizing the water-ratio-directed properties of a TPE-TSC-based turn-on fluorescent selective detection of multiple ions by using acetonitrile and acetonitrile-water. When pure acetonitrile was used as the solvent, TPE-TSC was not showed a selective and sensitive effect for any ions. Thereupon, studies were carried out in aqueous solutions of acetonitrile. As a result of studies, TPE-TSC was showed a selective and sensitive fluorescence “turn on” response towards Cu2+ and Hg2+ in CH3CN/H2O (30–50% of water for Cu2+, 70–90% of water for Hg2+). When an aqueous solution of acetonitrile (CH3CN/H2O; v/v:1/1) was used, the TPE-TSC was determined to be a sensitive and selective fluorescent “turn on” sensing for Cu2+ with a LOD value of 15.74 µM, which is the range of copper that should be in the blood (11.8–23.6 μM). In addition, when the studies were carried out in CH3CN/H2O (v/v:1/9), TPE-TSC was further determined to be a turn-on fluorescent sensing for Hg2+ with a LOD value of 18 µM. Moreover, DFT calculations confirmed the nonplanar or propeller structures. As a result of all these studies, it can be said that TPE-TSC, may be a useful and water-ratio-directed selective turn-on sensor candidate for Cu2+ and Hg2+ sensing in industrial wastewaters.

Poly-l-lysine-Functionalized Green-Light-Emitting Carbon Dots as a Fluorescence Turn-on Sensor for Ultrasensitive Detection of Endotoxin.

Herein, we report a facile, ultrasensitive, and selective fluorescence turn-on sensing strategy based on green-light-emitting functional nanodots for the detection of bacterial lipopolysaccharide (LPS) endotoxin. In this protocol, first, the pure carbon dots (CDs) with a fairly high quantum yield were prepared by microwave-assisted pyrolysis of citric acid in the presence of urea. Subsequently, the carboxyl-group-rich surfaces of the CDs were allowed to conjugate with the poly-l-lysine (PLL) using an EDC-NHS amidization method to obtain the PLL-modified CDs (PLL-CDs). The LPS could specifically bind to the PLL at the PLL-CD surfaces, and this binding enabled an electron transfer from the phosphate groups of LPS to the carbon core through the PLL bridge, thus resulting in a fluorescence enhancement. Interestingly, this fluorescent turn-on sensor provided a detection limit of 68.3 fM in PBS (pH 7.4), which is the lowest ever reported among all of the synthetic assays for LPS detection. Furthermore, our fluorescent probe was able to show a remarkable selectivity toward LPS over a range of commonly known interfering substances. Thus, this study demonstrated the feasibility of using specific LPS binding to PLL to drive molecular recognition in aqueous medium and offered an effective fluorescence turn-on sensing strategy to detect bacterial endotoxin in diverse clinical and biological applications.

A highly sensitive and selective fluorescence turn-on probe for the sensing of H2S in vitro and in vivo

A fluorescence turn-on probe, 2-butyl-1,3-dioxo-2,3-dihydro-1H-benzo[de]isoquinolin-6-yl 2,4-dinitrobenzenesulfonate (NT-SH), has been constructed for sensing of hydrogen sulfide (H2S). NT-SH exhibited excellent detection performance including favorable water solubility, low fluorescence background, high enhancement (45-fold), large linear response range (0–50 μM) and low detection limit (80.01 nM) for H2S in aqueous. In addition, the response mechanism of NT-SH for H2S was confirmed by the theoretical calculation and mass spectral analysis. More importantly, the imaging experiments of H2S in vitro and in vivo confirmed that NT-SH had low cytotoxicity, and favorable biocompatibility. In addition, it illustrated that NT-SH was able to detected exogenous H2S in living cells and zebrafish. These results suggested that NT-SH can be act as a potential molecular tool for detecting of H2S in aqueous solution, in vitro and in vivo.

Anthracene possessing amide functionality as a turn-on fluorescent probe for Cu2+ and Zn2+ ions

An anthracene appended PET chemosensor, anthracene-9-carboxylic acid (3,4-dimethoxy-phenyl)-amide (A1 ), has been synthesized through condensation of corresponding acyl chloride and 3,4-dimethoxyaniline containing C = O and NH as receptors. The sensor A1 exhibited selective fluorescence turn-on behavior towards Cu2+ and Zn2+ ions in CH3CN. Cu2+ ions displayed 18-fold enhancement (Φ = 0.006→0.071) in the fluorescence spectrum of A1 , which are otherwise well known for fluorescence quenching phenomenon. Moreover, A1 could easily discriminate between Zn2+ and Cd2+ ions, the two metal ions of similar nature. The Job’s plots analysis determined 2:1 (A1 :Cu2+/Zn2+) stoichiometry between the sensor A1 and Cu2+/Zn2+ ions. The LOD values were calculated to be 1.75 and 3.08 µM for Cu2+ and Zn2+, respectively.

Thioglycolic acid capped cadmium sulphide quantum dots as a turn-on fluorescence sensor for the determination of 5-hydroxyindoleacetic acid

A simple and highly selective turn-on fluorescence sensor has been developed for 5-hydroxyindoleacetic acid (5-HIAA) using thioglycolic acid capped cadmium sulphide quantum dots (TGA-CdS QDs). 5-HIAA enhances the fluorescence intensity of CdS QDs via aggregation-induced emission enhancement mechanism [AIEE]. Different sensor conditions have been optimized and under such conditions, the sensor achieved the quantification of 5-HIAA in the range of 2.5 × 10−6 M to 8.0 × 10-5 M with a limit of detection (LOD) of 8.4 × 10-7 M. The reliability of the sensor towards 5-HIAA detection has been proved by its successful application in synthetic urine and blood serum.

Porphyrin-Based Metal-Organic Framework Probe: Highly Selective and Sensitive Fluorescent Turn-On Sensor for M3+ (Al3+, Cr3+, and Fe3+) Ions.

The development of porphyrin-based metal-organic frameworks (MOFs) has attracted significant interest in the scientific community in recent years because of their versatile applications particularly in optical and electronic fields. In this study, a highly selective and sensitive fluorescent turn-on sensor using a porphyrinic MOF, Tb-TCPP, is presented, which displays a 10-fold fluorescence enhancement in the presence of Al3+, Cr3+, and Fe3+ ions. The detection limit is in the nM region. For the Al3+ ion, it could be visually detected at concentrations as low as 5 mM within 15 min. Tb-TCPP could also be used as an indicator for acidic or alkaline solutions at pH values of >9 and <3. The studies on the detection mechanism illustrate that cation exchange proceed between Tb-TCPP and these M3+ ions, and consequently, energy transfer from TCPP to Tb3+ is suppressed and π*-π energy transfer of the porphyrin ligand is significantly enhanced.