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A BODIPY-based fluorescence turn-on probe, exhibiting high selectivity and sensitivity towards intracellular thiols with excellent lysosomal localization is reported. The probe displayed fast response towards biothiols in aqueous solution. Localization of the probe in lysosome was demonstrated by intracellular colocalization studies with the aid of LysoSensor Green.

The study on a fluorescent probe that undergoes a H2S mediated cascade reaction to form an iminocoumarin fluorophore is reported. The probe features better water solubility and fast sensing time (t1/2 = 6.1 min and response time = 24 min) as key advances compared to the reported probe that works on a similar mechanism. The sensing mechanism of the probe was demonstrated by mass spectrometric, HPLC titration and FT-IR titration methods. H2S sensing by the probe was characterized by a 31-fold fluorescence enhancement and alimit of detection of 169 nM. Application of the probe was demonstrated by imaging of H2S in live cells.

Hydrogen sulphide (H2S) is known to play a vital role in human physiology and pathology which stimulated interest in understanding complex behaviour of H2S. Discerning the pathways of H2S production and its mode of action is still a challenge owing to its volatile and reactive nature. Herein we report azide functionalized metal-organic framework (MOF) as a selective turn-on fluorescent probe for H2S detection. The MOF shows highly selective and fast response towards H2S even in presence of other relevant biomolecules. Low cytotoxicity and H2S detection in live cells, demonstrate the potential of MOF towards monitoring H2S chemistry in biological system. To the best of our knowledge this is the first example of MOF that exhibit fast and highly selective fluorescence turn-on response towards H2S under physiological conditions.

Pyranine as a new class of fluorescent chemosensor for the Cu(+) ion is reported. The probe is capable of discriminating ranges of cations from the Cu(+) ion, even in competing environment. The dye displayed a rapid fluorescence response (t1/2 = 1.66 min) towards the Cu(+) ion, and the micromolar detection limit enabled the detection of the ion in environmental samples. The observed stoichiometry of complexation between pyranine and Cu(+) was 2 : 1. Interestingly, the sensing characteristic was specific to only neutral pH. A metal-to-ligand charge-transfer (MLCT)-based mechanism of sensing was proposed based on electron spin resonance (EPR), Raman spectroscopic and cyclic voltammetric studies.

A cascade reaction-based colorimetric and fluorescent probe for selective fluoride ion detection is reported. The probe displays a fast response (t1/2 = 2.41 min) and 550-fold fluorescence enhancement during sensing of fluoride ions. Application of the probe in live cell imaging is demonstrated.

The design, synthesis and fluoride sensing ability of a 7-nitro-2,1,3-benzoxadiazole (NBD) based chemodosimeter is reported. Theoretical calculations were used to design a more applicable off-on response, by choosing NBD as the accurate fluorophore. Reaction of the NBD-probe with 300 equivalents of tetrabutyl ammonium fluoride (TBAF) exhibited a response time of 80 minutes and the reaction was selective to F(-) and sensing of the ion was marked by a 110-fold enhancement of green fluorescence. The off-on fluorescence characteristics of the probe enabled its application in live-cell imaging of intracellular F(-) ions.

A BODIPY-azide based colorimetric and fluorescence turn-ON probe for rapid, selective and sensitive detection of H2S is reported. The probe displayed a fast response time (10 min in HEPES and 30 s in serum albumin), 28-fold fluorescence enhancement and low detection limit up to 259 nM. The application of the probe to the estimation of H2S in live cells was demonstrated.

A BODIPY-based selective thiophenol probe capable of discriminating aliphatic thiols is reported. The fluorescence off-on effect upon reaction with thiol is elucidated with theoretical calculations. The sensing of thiophenol is associated with a color change from red to yellow and 63-fold enhancement in green fluorescence. Application of the probe for selective thiophenol detection is demonstrated by live cell imaging.

Prolonged exposure to radiation from radionuclei used in medical research can cause DNA damage and mutation, which lead to several diseases including cancer. Radioactivity-based experiments are expensive and associated with specialized training, dedication of instruments, approvals, and cleanup with potential hazardous waste. The objective of this study was to find an alternative to the use of radioactivity in medical research using nucleic acid chemistry. FITC-labeled oligonucleotides that contain wild-type (wt) and modified base (8-oxo-G) at the same position and their complementary unlabeled strand were synthesized. Purified DNA repair enzyme, OGG1, and nuclear lysates from MCF-7 breast cancer cells were incubated with double-stranded FITC-labeled wt and 8-oxo-G oligonucleotide to demonstrate the OGG1 incision assay. We found that FITC-coupled oligonucleotides do not impose a steric hindrance during duplex formation, and the fluorescence intensity of the oligonucleotide is comparable with the intensity of the radioactive oligonucleotide. Moreover, we have seen that the OGG1 incision assay can be performed using these fluorescence oligonucleotides, replacing conventional use of radiolabeled oligonucleotides in the assay. Although the use of fluorescent-labeled oligonucleotides was described in detail for incision assays, the technique can be applied to replace a broad range of experiments, where radioactive oligonucleotides are used, eliminating the hazardous consequences of radiation.