Turn-on Fluorescent Probe For Detection Research Articles

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 Benzil- and BODIPY-Based Turn-On Fluorescent Probe for Detection of Hydrogen Peroxide.

Faced with rising threats of terrorism, environmental and health risks, achieving sensitive and selective detection of peroxide-based explosives (PEs) has become a global focus. In this study, a turn-on fluorescent probe (BOD) based on benzil (H2O2-recognition element) and 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY) derivative (fluorophore) was developed to sensitively and specifically detect hydrogen peroxide (H2O2). The synthesized BOD had a very weak fluorescence due to intramolecular donor-excited photo-induced electron transfer (d-PET) effect; however, it could emit a strong fluorescence since H2O2 selectively oxidized the benzil moiety and released free BODIPY fluorophore (BOD-COOH). As a result, the proposed BOD detected H2O2 in linear detection ranged from 25 to 125 µM with a detection limit of 4.41 µM. Meanwhile, the proposed BOD showed good selectivity toward H2O2, which is not affected by other common reactive oxygen species (ROS) and ions from explosive residues. In addition, a blue shift from 508 to 498 nm was observed in the absorption spectra upon addition of H2O2. More importantly, the BOD was successfully applied for rapid detection of H2O2 vapor with good sensitivity (down to 7 ppb), which holds great potential for practical use in public safety, forensic analysis and environmental monitoring.

A novel turn-on fluorescent probe for detection of pH in extremely acidic environment and its application

A water-soluble turn-on fluorescent probe PNAP for pH has been designed and synthesized. PNAP was consist of pyrene as fluorophore and morpholine as receptor. Owing to the photoinduced electron transfer (PET) effect, the fluorescence of PNAP was quenched, while PNAP exhibited a remarkable “turn-on” fluorescence with the increase of acidity. Notably for its pKa of 2.15, PNAP was one of the pH fluorescent probes used in extremely acidic environments. Furthermore, PNAP also displayed good repeatability, strong anti-ion interference ability, high sensitivity and selectivity toward pH. In addition, PNAP has been successfully applied to the test strips and monitor the pH of environment water samples and realistic samples, showing its good promising prospect.

A thiocoumarin-based turn-on fluorescent probe for hypochlorite detection and its application to live-cell imaging

A thiocoumarin-based turn-on fluorescence probe for the detection of hypochlorite anion (ClO−) was prepared and characterized. Coumarin dye (CZCN-O) exhibited intense fluorescence with good quantum yields (ΦPL = 0.98) in acetonitrile. Contrastingly, the fluorescence of thiocoumarin dye (CZCN-S) was almost completely quenched (ΦPL < 0.01) because of the efficient intersystem crossing from the emissive singlet excited state to the non-emissive triplet state. The addition of ClO− to the PBS buffer (pH = 7.4, containing 50% ACN) of thiocoumarin resulted in a remarkable fluorescence enhancement with an emission maximum at 486 nm, indicating the sensitive OFF–ON fluorescence sensing of ClO−. The calculated detection limit of ClO− in 50% aqueous ACN was 0.17 μM. An investigation of the sensing behavior to various analytes revealed that thiocoumarin dye had an excellent selectivity for ClO−. The recognition mechanism was attributed to the ClO−-induced conversion of thiocarbonyl coumarin into its oxo analogue through oxidative desulfurization. In particular, cell studies demonstrated that thiocoumarin dye could be used as an effective fluorescent probe for the detection of ClO− in living cells.

Highly selective turn-on fluorescent probe for detection of cyanide in water and food materials

A naphthoquinone-imine based fluorescent probe (R) has been synthesized and characterized by NMR and mass spectral techniques. The receptor shows high selectivity towards cyanide in water in the presence of other competitive anions with an instantaneous colour change from non-emissive to green under UV light. The turn-on fluorescence is due to deprotonation of three hydroxyl groups by cyanide ions as evidenced from 1H NMR titration experiment. The LOD of cyanide by R in water is 0.6 μM, which is much lower than the permissible limit of cyanide in drinking water according to the WHO.

Remarkably selective biocompatible turn-on fluorescent probe for detection of Fe3+ in human blood samples and cells.

The robust nature of a biocompatible fluorescent probe is demonstrated, by its detection of Fe3+ even after repeated rounds of quenching (reversibility) by acetate in real human blood samples and cells in vitro. Significantly trace levels of Fe3+ ions up to 8.2 nM could be detected, remaining unaffected by the existence of various other metal ions. The obtained results are validated by AAS and ICP-OES methods. A portable test strip is also fabricated for quick on field detection of Fe3+. As iron is a ubiquitous metal in cells and plays a prominent role in biological processes, the use of this probe to image Fe3+ in cells is a substantial development towards biosensing. Cytotoxicity studies also proved the nontoxic nature of this probe.

A Turn-On Fluorescent Probe for Detection of Sub-ppm Levels of a Sulfur Mustard Simulant with High Selectivity

A new type of fluorescent probe capable of detecting a sulfur mustard (SM) simultant at a concentration of 1.2 μM in solution and 0.5 ppm in the gas phase has been developed. Owing to its molecular structure with a thiocarbonyl component and two piperidyl moieties integrated into the xanthene molecular skeleton, this probe underwent a highly selective nucleophilic reaction with the SM simultant and generated a thiopyronin derivative emitting intensive pink fluorescence. The distinct difference in electronic structure between the probe and thiopyronin derivative generated a marked shift of the absorption band from 445 to 567 nm, which enabled an optimal wavelength propitious for exciting the thiopyronin derivative but adverse to the probe. Such efficient separation of the excitation wavelength and tremendous increase in fluorescence quantum yield, from less than 0.002 to 0.53, upon conversion from the probe to the thiopyronin derivative, jointly led to a distinct contrast in the beaconing fluorescence signal (up to 850-fold) and therefore the unprecedented sensitivity for detecting SM species.

VS2 quantum dot label-free fluorescent probe for sensitive and selective detection of ALP.

As an essential enzyme highly associated with various human diseases, alkaline phosphatase (ALP) plays an important role in human tissues. Developing new materials and strategies for monitoring ALP is thus important. We have developed a novel label-free fluorescent sensing system for ALP activity that is based on the "turn-on" fluorescence of VS2 quantum dots. The fluorescence of VS2 quantum dots quenched by Fe3+ can be restored by ascorbic acid, which is generated by hydrolysis of L-ascorbic acid 2-phosphate catalyzed by ALP. Rapid, convenient, and sensitive detection of ALP is achieved in the range from 3 to 1000 U/L (R 2 =0.9985), with a detection limit of 0.27 U/L. The proposed sensor exhibits excellent selectivity for ALP compared with other enzymes and proteins, such as glucose oxidase, lysozyme, trypsin, human serum albumin, and bovine serum albumin. The reliability for ALP determination in human serum plasma has been demonstrated with satisfactory recovery, revealing promising application in clinical diagnosis and biomedical research. Graphical abstract Hydrothermally synthesized VS2 quantum dots serving as a novel turn-on fluorescent probe for detection of alkaline phosphatase (ALP) activity. AA L-ascorbic acid, AAP L-ascorbic acid 2-phosphate, NAC N-acetyl-L-cysteine.

A novel HPQ-based turn-on fluorescent probe for detection of fluoride ions in living cells

2-(2′-Hydroxyphenyl)-4(3H)-quinazolinone (HPQ) has been reported as a precipitating fluorescent molecule with excellent optical properties, such as large Stokes shift and strong fluorescence intensity. HPQF, a novel HPQ-based turn-on probe for localizable detection of fluoride ions, was designed, synthesized and fully characterized by 1H NMR, 13C NMR and HRMS. As a chemogenic fluoride probe, the tert-butyldiphenylsilane moiety of HPQF can be easily cleaved by fluoride. After spontaneous 1,6-elimination, HPQ molecule was generated to emit fluorescence under the excitation light. Further study shows that HPQF exhibited high selectivity and sensitivity for detection of fluoride. In addition, HPQF was utilized for the detection of fluoride in living cells.

A triphenylamine-based colorimetric and “turn-on” fluorescent probe for detection of cyanide anions in live cells

A triphenylamine–hemicyanine dye was developed as a colorimetric and turn-on fluorescent probe for detection of cyanide with high sensitivity and selectivity.

Rapid, photoinduced electron transfer-modulated, turn-on fluorescent probe for detection and cellular imaging of biologically significant thiols.

There is a very limited number of existing probes whose fluorescence is turned on in the presence of the class of biological thiols made up of glutathione, cysteine, and homocysteine. The extant probes for this class of biological thiols commonly have poor aqueous solubility and long analyte response times, and they demand a very high probe/thiol ratio for decreased time of significant reporter signal generation; knowledge regarding their selectivity with respect to other sulfur-based analytes is unclear. Described here is a previously unreported photoinduced electron-transfer-quenched probe (HMBQ-Nap 1) that offers highly selective and rapid in vitro detection of this class of biologically important thiols at low concentrations and low probe/thiol ratio, and importantly, very rapid imaging of these biological thiols in human cells.

A turn-on fluorescent probe for detection of hydrogen sulfide in aqueous solution and living cells

We report the design and synthesis of a turn-on fluorescence probe FD-NO2 for H2S, utilizing H2S selective reduction of the nitro group. FD-NO2 displays good water solubility, negligible background fluorescence, high sensitivity, and high selectivity for H2S over other anions, reactive sulfur, oxygen, and nitrogen species. Further confocal imaging experiments demonstrate that FD-NO2 is capable of detecting H2S in living cells.

A turn-on fluorescent probe for detection of tyrosinase activity

We have presented a fluorescent probe that exhibits a fluorescence turn-on signal upon reaction with tyrosinase, and we show that it can be readily employed for the assessment of tyrosinase activity and tyrosinase inhibitor activities in buffered aqueous solution.