A highly selective colorimetric and turn-on fluorescent probe for cyanide anion

A new colorimetric and turn-on fluorescence chemosensor was developed for cyanide anion with high selectivity in the presence of other anions in an aqueous THF solution. The sensing mechanism is attributed to the interruption of π-conjugation by a nucleophilic addition of cyanide to the β-position of a dicyanoethylene unit.     

Highly selective and sensitive fluorescence turn-on probe for proline

A weakly fluorescent coumarinyl aldehyde was transformed into a strongly fluorescent aldol product by a catalytic amount of proline. The aldehyde probe has shown a highly selective fluorescence turn-on response toward proline over other amino acids with micromolar sensitivity.     

A highly selective naked-eye probe for hypochlorite with the p-methoxyphenol-substituted aniline compound

A highly selective naked-eye detection of ClO⁻ is successfully established with probe 1 by taking advantage of the oxidation transformation of p-methoxyphenol into benzoquinone with ClO⁻ and the ICT absorption within the electron donor-acceptor compound. The color of the solution of probe 1 was changed, obviously upon addition of ClO⁻ and ClO⁻ with concentration as low as 1.74 μM can be analyzed in aqueous solution with probe 1. Moreover, the interferences of other anions can be neglected.     

A highly selective and sensitive fluorescence "turn-on" probe for Ag+ in aqueous solution and live cells

A naphthalimide-based fluorescent probe, NPQ, that contains a novel receptor was successfully developed. NPQ exhibited "turn-on" fluorescence and excellent selectivity toward Ag(+) in the presence of various other metal ions in aqueous solution. A series of control compounds were designed and synthesized in order to explore the photoinduced electron transfer (PET) quenching mechanism of NPQ and binding mode of NPQ with Ag(+). Moreover, with the NPQ-Ag(+) complex, I(-) was easily selectively recognized by a marked fluorescence quenching. The live cell imaging experiments demonstrate that NPQ can be used as a fluorescent probe for monitoring Ag(+) in living cells.     

A sensitive and selective detection method for thiol compounds using novel fluorescence probe

In this work, a sensitive and selective detection method based on fluorescence resonance energy transfer (FRET) was developed for analyzing thiol compounds by using a novel fluorescent probe. The new fluorescent probe contains a disulfide bond which selectively reacts with nucleophilic thiolate through the thiol-disulfide exchange reaction. An obvious fluorescence recovery can be observed upon addition of the thiol compound in the fluorescent probe solution due to the thiol-disulfide exchange reaction and the destruction of FRET. This novel probe was successfully used to determine dithiothreitol (DTT), glutathione (GSH) and cysteine (Cys). The limits of detection (LOD) were 2.0 μM for DTT, 0.6 μM for GSH, and 0.8 μM for Cys. This new detection method was further investigated in the analysis of compound amino acid injection.     

Development of a highly sensitive fluorescence probe for hydrogen peroxide

Hydrogen peroxide is believed to play a role in cellular signal transduction by reversible oxidation of proteins. Here, we report the design and synthesis of a novel fluorescence probe for hydrogen peroxide, utilizing a photoinduced electron transfer strategy based on benzil chemistry to control the fluorescence. The practical value of this highly sensitive and selective fluorescence probe, NBzF, was confirmed by its application to imaging of hydrogen peroxide generation in live RAW 264.7 macrophages. NBzF was also employed for live cell imaging of hydrogen peroxide generated as a signaling molecule in A431 human epidermoid carcinoma cells.     

Development of a highly selective fluorescence probe for hydrogen sulfide

Hydrogen sulfide (H(2)S) has recently been identified as a biological response modifier. Here, we report the design and synthesis of a novel fluorescence probe for H(2)S, HSip-1, utilizing azamacrocyclic copper(II) ion complex chemistry to control the fluorescence. HSip-1 showed high selectivity and high sensitivity for H(2)S, and its potential for biological applications was confirmed by employing it for fluorescence imaging of H(2)S in live cells.     

Characterization of rhodamine B hydroxylamide as a highly selective and sensitive fluorescence probe for copper(II)

Rhodamine B hydroxylamide (1) is characterized as a highly selective and sensitive fluorescence probe for Cu²⁺. Under the optimized conditions, the probe exhibits specific absorbance-on and fluorescence-on responses to Cu²⁺ only. This remarkable property may allow Cu²⁺ to be detected directly in the presence of the other transition metal ions, and such an application has been demonstrated to human serum. The reaction mechanism is also investigated and proposed as that the hydroxylamide group of 1 binds Cu²⁺, and the subsequent complexation of Cu²⁺ displays a high catalytic activity for the hydrolytic cleavage of the amide bond, causing the release of fluorophore (rhodamine B) and thereby the retrievement of absorbance and fluorescence. The recovered fluorescence intensity is proportional to the concentration of Cu²⁺ in the range 1-20 μM. The detection limit for Cu²⁺ is 33 nM (k = 3). The reaction mechanism described here may be useful for developing excellent spectroscopic probes with cleavable active bonds for other analytes.     

Magic sized ZnS quantum dots as a highly sensitive and selective fluorescence sensor probe for Ag+ ions

A green and simple chemical synthesis of magic sized water soluble blue-emitting ZnS quantum dots (QDs) has been accomplished by reacting anhydrous Zn acetate, sodium sulfide and thiolactic acid (TLA) at room temperature in aqueous solution. Refluxing of this mixture in open air yielded ZnS clusters of about 3.5 nm in diameter showing very strong and narrow photoluminescence properties with long stability. Refluxing did not cause any noticeable size increment of the clusters. As a result, the QDs obtained after different refluxing conditions showed similar absorption and photoluminescence (PL) features. Use of TLA as a capping agent effectively yielded such stable and magic sized QDs. The as-synthesized and 0.5 h refluxed ZnS QDs were used as a fluorescence sensor for Ag(+) ions. It has been observed that after addition of Ag(+) ions of concentration 0.5-1 μM the strong fluorescence of ZnS QDs was almost quenched. The quenched fluorescence can be recovered by adding ethylenediamine to form a complex with Ag(+) ions. The other metal ions (K(+), Ca(2+), Au(3+), Cu(2+), Fe(3+), Mn(2+), Mg(2+), Co(2+)) showed little or no effect on the fluorescence of ZnS QDs when tested individually or as a mixture. In the presence of all these ions, Ag(+) responded well and therefore ZnS QDs reported in this work can be used as a Ag(+) ion fluorescence sensor.     

Reversible fluorescent probe for highly selective and sensitive detection of mercapto biomolecules

A coumarin-derived complex, Hg(2)L(2), was reported as a highly sensitive and selective probe for the detection of mercapto biomolecules in aqueous solution. The addition of Cys to a 99% aqueous solution of Hg(2)L(2) resulted in rapid and remarkable fluorescence OFF-ON (emission at 525 nm) due to the ligand-exchange reaction of Cys with L coordinated to Hg(2+). The increased fluorescence can be completely quenched by Hg(2+) and recovered again by the subsequent addition of Cys. Such a fluorescence OFF-ON circle can be repeated at least 10 times by the alterative addition of Cys and Hg(2+) to the solution of Hg(2)L(2), indicating that it can be used as a convertible and reversible probe for the detection of Cys. The interconversion of Hg(2)L(2) and L via the decomplexation/complexation by the modulation of Cys/Hg(2+) was definitely verified from their crystal structures. Other competitive amino acids without a thiol group cannot induce any fluorescence changes, implying that Hg(2)L(2) can selectively determine mercapto biomolecules. Using confocal fluorescence imaging, L/Hg(2)L(2) as a pair of reversible probes can be further applied to track and monitor the self-detoxification process of Hg(2+) ions in SYS5 cells.     

A highly sensitive fluorescence probe for thiophenol in living cells via a substitution-cyclization strategy

A novel fluorescent probe 1 was synthesized for the detection of thiophenol on the basis of a unique thiophenol-mediated substitution-cyclization reaction. The probe 1 displayed 420-fold fluorescence intensity enhancement and highly selective and sensitive response for thiophenol over other competing sulfur species. This probe showed an excellent linear relationship in 10–140 μM and the low detection limit of 29 nM. The recognition mechanism of probe 1 toward PhSH was supported by the NMR spectrum and ESI-MS. Furthermore, the probe 1 was successfully applied for detection of thiophenol in living HepG2 cells.     

A coumarin-derived fluorescence probe selective for magnesium

Two different coumarin derivatives have been connected via an imine linkage to obtain a new fluorescence signaling system. This compound itself does not show any emission due to rapid isomerization around the C[double bond]N bond. However, in the presence of a Mg(II) ion, this isomerization is stopped because of bonding to the metal ion resulting in high-intensity (approximately 550-fold) emission. Other metal ions like Li(I), Ca(II), and Zn(II) show very little emission, while biologically relevant transition-metal ions do not show any emission. In this way, the Mg(II) ion can be detected in the presence of these ions.     

Dual-site fluorescent probe for highly selective and sensitive detection of sulfite and biothiols

A dual-site fluorescent probe that could discriminatively respond to Cys and HSO^3- through two emission channels was reported, and it could further applied in imaging biothiols in living cells.     

A highly selective and sensitive fluorescence sensing system for distinction between diphosphate and nucleoside triphosphates

Among the numerous chemosensors available for diphosphate (P(2)O(7)(4-), PPi) and nucleoside triphosphates (NTPs), only a few can distinguish between PPi and NTPs. Hence, very few bioanalytical applications based on such selective chemosensors have been realized. We have developed a new fluorescence sensing system for distinction between PPi and NTPs based on the combination of two sensors, a binuclear Zn(II) complex (1·2Zn) and boronic acid (BA), in which one chemosensor (1·2Zn) shows signal changes depending on the PPi (or NTP) concentration, and the other (BA) blocks the signal change caused by NTPs; this system enables the distinction of PPi from NTPs and is sensitive to nanomolar concentrations of PPi. The new sensing system has been successfully used for the direct quantification of RNA polymerase activity.     

A label-free fluorescence DNA probe based on ligation reaction with quadruplex formation for highly sensitive and selective detection of nicotinamide adenine dinucleotide

A simple label-free fluorescent sensing scheme for sensitive and selective detection of nicotinamide adenine dinucleotide (NAD(+)) has been developed based on DNA ligation reaction with ligand-responsive quadruplex formation. This approach can detect 0.5 nM NAD(+) with high selectivity against other NAD(+) analogs.     

A highly sensitive and selective chemosensor for cyanide

A highly sensitive and selective cyanide chemosensor based on fused indoline and benzooxazine fragment was reported with fast response. The detection of cyanide was performed via the nucleophilic attack of cyanide anion on the oxazine. (1)H NMR and MS studies confirmed the cleavage of C-O bond of oxazine and binding of cyanide to the spiro center of oxazine. The specific reaction results in high selectivity for cyanide ion. Addition of cyanide anion to the oxazine in MeCN/H(2)O solution results in a loss in absorbance at 343 nm and an increase in new absorbance at 411 nm, thus resulting in obvious color changes. Cyanide can be detected down to 1 microM levels in a fast response of less than 30s with no interference of other anionic species. The cyanide detection method should have potential application in a variety of settings requiring rapid and accurate analysis of cyanide anion for drinking and fresh water.     

A highly selective and sensitive nanoprobe for detection and imaging of the superoxide anion radical in living cells

A novel fluorescent nanoprobe with high sensitivity and selectivity for detection and imaging of the superoxide anion radical O(2)(·-) in living cells was designed and synthesized by a simple self-assembly method based on 2-chloro-1,3-dibenzothiazoline-cyclohexene (DBZTC) and Ag@SiO(2) core-shell nanoparticles.     

A Schiff base fluorescence probe for highly selective turn-on recognition of Zn2+

A simple Schiff base CTS, synthesized between 2-hydroxy-1-naphthaldehyde and 2-benzylthio-ethanamine, was found to be a good turn-on fluorescence probe for the detection of Zn²⁺, due to the restriction of the rotation of the bond between CN and naphthalene ring and/or the blocking of the photo-induced electron transfer (PET) mechanism of the nitrogen atom to naphthalene ring. Excellent selectivity for Zn²⁺ was evidenced, over many other competing ions, including Fe³⁺, Cr³⁺, Ni²⁺, Co²⁺, Fe²⁺,Mn²⁺, Ca²⁺, Hg²⁺, Pb²⁺, Cu²⁺, Mg²⁺, Ba²⁺, Cd²⁺, Ag⁺, Li⁺, K⁺, and Na⁺, in EtOH/HEPES buffer (95:5, v/v, pH = 7.4). It was noteworthy that Cd²⁺ had no interference with Zn²⁺. The stoichiometric complex of CTS-Zn²⁺ was determined to be 2:1 for CTS and Zn²⁺ in molar, based on the Job plot and single crystal X-ray diffraction data. The binding constant of the complex was 85.7 M^?2 with a detection limit of 5.03 × 10^?7 M. The fluorescence bio-imaging capability of CTS to detect Zn²⁺ in live cells was also studied. These results indicated that CTS could serve as a favorable probe for Zn²⁺.