A 'double locked' ratiometric fluorescent probe for detection of cysteine in a viscous system and its application in cancer cells.

Intracellular viscosity is a physicochemical property that regulates the consequences of several biological progressions. Cysteine (Cys) is an important signaling molecule that commands many cellular activities, such as antioxidant generation. Predicting that both may be interconnected with a diversity of pathological processes, their contemporaneous measurement would be valuable for studying the pathological ailment of cells. Herein, we have synthesized a 'double locked' probe, acrylic acid 6-[4-(2-benzothiazol-2-yl-2-cyano-vinyl)-phenyl]-naphthalen-2-yl ester (ABN) for the detection of Cys in a viscous medium and explored its application to living cells that were exposed to dexamethasone to regulate the intracellular viscosity level. ABN displayed a satisfactory ratiometric (blue to orange) fluorescence response in solution and in living cells when Cys and viscosity coexisted. A turn-on fluorescence signal was visualized when the probe was individually treated with Cys and glycerol (a standard viscosity source). Therefore, we propose that ABN is a fluorescent probe that permits the monitoring of variations in intracellular viscosity and Cys levels in a biological environment, and it can be utilized in innumerable cellular damage models.

A chromogenic and ratiometric fluorogenic probe for rapid detection of a nerve agent simulant DCP based on a hybrid hydroxynaphthalene-hemicyanine dye.

A new cyanine dye (CYD) based on hybrid hydroxynaphthalene-hemicyanine has been synthesized and characterized. The chromogenic and ratiometric fluorogenic probe (CYD) enables a fast and highly sensitive response to an OP nerve agent mimic diethyl chlorophosphate (DCP) through tandem phosphorylation and intramolecular cyclization reaction within 1 min and with the detection limit as low as 18.86 nM. To our knowledge this is the first report of a hydroxyl assisted bathochromic shift in a selective chemodosimeter for DCP exhibiting a ratiometric response. TDDFT calculations were performed in order to demonstrate the electronic properties of the probe and the cyclized product. Moreover, the utility of the probe CYD for the detection of DCP in live cells, in the gas phase and in a spiked soil sample has also been demonstrated.

Selective fluorescence sensing and quantification of uric acid by naphthyridine-based receptor in biological sample.

Naphthyridine-based fluorescent probe H1 was synthesized and characterized for the quantification and selective detection of Uric Acid (UA) in live cell. In presence of UA, H1 forms the specific host-guest complex mainly through intermolecular hydrogen bonding and aromatic stacking which produces "turn-off" fluorescence. The probe and UA is found to be 1:1 stoichiometry on the basis of absorption and fluorescence titrations. The probe H1 has been shown to detect UA up to 0.6µM at pH 7.4. DFT-TDDFT calculations were performed in order to demonstrate the sensing mechanism and the electronic properties of the receptor-donor complex. The selectivity was evaluated in Vero cells in the presence of UA with other purine derivatives, structurally similar to UA. It was found to exhibit no cytotoxicity effect in tested concentration of H1 and good membrane permeability for the detection of UA in living cell system. The unknown concentration of UA in serum and urine can be measured easily using the fluorescence property of probe H1.

Simple Bisthiocarbonohydrazone as a Sensitive, Selective, Colorimetric, and Ratiometric Fluorescent Chemosensor for Picric Acids.

A bisthiocarbonohydrazone-based chemosensor molecule (R1) containing a tetrahydro-8-hydroxyquinolizine-9-carboxaldehyde moiety has been synthesized and characterized as a new ratiometric fluorescent probe for picric acid (PA). The ratiometric probe R1 is a highly selective and sensitive colorimetric chemosensor for PA. The association between the chemosensor and PA and the ratiometric performance enabled by the key role of excited state intramolecular proton transfer in the detection process are demonstrated. Selectivity experiments proved that R1 has excellent selectivity to PA over other nitroaromatic chemicals. Importantly, the ratiometric probe exhibited a noteworthy change in both colorimetric and emission color, and this key feature enables R1 to be employed for detection of PA by simple visual inspection in silica-gel-coated thin-layer chromatography plates. Probe R1 has been shown to detect PA up to 3.2 nM at pH 7.4. Microstructural features of R1 and its PA complex have been measured by a field emission scanning electron microscope, and it clearly proves that their morphological features differ dramatically both in shape and size. Density function theory and time-dependent density function theory calculations were performed to establish the sensing mechanism and the electronic properties of probe R1. Furthermore, we have demonstrated the utility of probe R1 for the detection of PA in live Vero cells for ratiometric fluorescence imaging.

A cyclization-induced emission enhancement (CIEE)-based ratiometric fluorogenic and chromogenic probe for the facile detection of a nerve agent simulant DCP.

The first ratiometric fluorescent probe for the detection of a nerve agent simulant was developed based on tandem phosphorylation and intramolecular cyclization, by which high sensitivity as well as large emission shift could be achieved.

A new selective chromogenic and turn-on fluorogenic probe for copper(II) in solution and vero cells: recognition of sulphide by [CuL].

A new coumarin-appended thioimidazole-linked imine conjugate, viz. has been synthesized and characterized. has been found to recognize Cu(2+) selectively among a wide range of biologically relevant metal ions. The chemosensing behavior of has been demonstrated through fluorescence, absorption, visual fluorescence color changes, ESI-MS and (1)H NMR titrations. The chemosensor showed selectivity toward Cu(2+) by switch on fluorescence among the 18 metal ions studied with a detection limit of 1.53 µM. The complex formed between and Cu(2+) is found to be 1 : 1 on the basis of absorption and fluorescence titrations and was confirmed by ESI-MS. DFT and TDDFT calculations were performed in order to demonstrate the structure of and [CuL] and the electronic properties of chemosensor and its copper complex. This highly fluorescent [CuL] complex has been used to recognize sulphide selectively among the other allied anions. Microstructural features of and its Cu(2+) complex have been investigated by SEM imaging (scanning electron microscopy). The biological applications of were evaluated in Vero cells and it was found to exhibit low cytotoxicity and good membrane permeability for the detection of Cu(2+).

An azodye-rhodamine-based fluorescent and colorimetric probe specific for the detection of Pd(2+) in aqueous ethanolic solution: synthesis, XRD characterization, computational studies and imaging in live cells.

Azodye-rhodamine hybrid colorimetric fluorescent probe (L) has been designed and synthesized. The structure of L has been established based on single crystal XRD. It has been shown to act as a selective turn-on fluorescent chemosensor for Pd(2+) with >40 fold enhancement by exhibiting red emission among the other 27 cations studied in aqueous ethanol. The coordination features of the species of recognition have been computationally evaluated by DFT methods and found to have a distorted tetrahedral Pd(2+) center in the binding core. The probe (L) has been shown to detect Pd up to 0.45 µM at pH 7.4. Furthermore, the probe can be used to image Pd(2+) in living cells.

Unique fluorogenic ratiometric fluorescent chemodosimeter for rapid sensing of CN(-) in water.

A new benzimidazole-spiropyran conjugate chemosensor molecule (BISP) has been synthesized and characterized by (1)H NMR spectroscopy, mass spectrometry (ESI-MS), and elemental analysis. The two isomeric forms (BISP↔BIMC) were shown to be highly selective and sensitive to CN(-) among the ten anions studied in aqueous HEPES buffer, as shown by fluorescence and absorption spectroscopy and even by visual color changes, with a detection limit of 1.7 µM for BIMC. The reaction of CN(-) with BIMC was monitored by (1)H NMR spectroscopy, high-resolution mass spectrometry (HRMS), UV/Vis measurements, and fluorescence spectroscopy in HEPES buffer of pH 7.4. TDDFT calculations were performed in order to correlate the electronic properties of the chemosensor with its cyanide complex. Further, titration against thiophilic metal ions like Au(3+), Cu(2+), Ag(+), and Hg(2+) with [BIMC-CN] in situ showed that it acts as a secondary recognition ensemble toward Au(3+) and Cu(2+) by switch-on fluorescence. In addition, a reversible logic-gate property of BIMC has been demonstrated through a feedback loop in the presence of CN(-) and Au(3+) ions, respectively. Furthermore, the use of BIMC to detect CN(-) in live cells by fluorescence imaging has also been demonstrated. Notably, test strips based on BIMC were fabricated, which could serve as convenient and efficient CN(-) test kits.

Ratiometric sensing of fluoride and acetate anions based on a BODIPY-azaindole platform and its application to living cell imaging.

A new BODIPY-azaindole based fluorescent sensor 1 was designed and synthesized as a new colorimetric and ratiometric fluorescent chemosensor for fluoride. The binding and sensing abilities of sensor 1 towards various anions were studied by absorption, emission and (1)H NMR titration spectroscopies. The spectral responses of 1 to fluoride in acetonitrile-water were studied: an approximately 69 nm red shift in absorption and ratiometric fluorescent response was observed. The striking light yellow to deep brown color change in ambient light and green to blue emission color change are thought to be due to the deprotonation of the indole moiety of the azaindole fluorophore. From the changes in the absorption, fluorescence, and (1)H NMR titration spectra, proton-transfer mechanisms were deduced. Density function theory and time-dependent density function theory calculations were conducted to rationalize the optical response of the sensor. Results were supported by confocal fluorescence imaging and MTT assay of live cells.