Dnyaneshwar Kand

A colorimetric and fluorometric BODIPY probe for rapid, selective detection of H2S and its application in live cell imaging

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.

Structural imposition on the off–on response of naphthalimide based probes for selective thiophenol sensing

N-Phenyl-1,8-naphthalimide based fluorescent probes are reported with various positions of dinitrobenzenesulfonyl (DNs) quencher on the phenyl ring. The probe with –DNs at the ortho-position was predicted to show better response compared to those with the quencher at the meta and para positions. The probe showed selective and very fast response (response time, tR = 1 min) toward thiophenol with 20-fold off–on fluorescence sensitivity. Thiophenol sensing applications by the probe were demonstrated via water sample analysis and live cell imaging studies.

A fluorescent off–on NBD-probe for F− sensing: theoretical validation and experimental studies

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.

Pink fluorescence emitting fluoride ion sensor: investigation of the cascade sensing mechanism and bioimaging applications

A resorufin based colorimetric and fluorescence off–on probe for selective fluoride ion detection is reported. 1H-NMR and HPLC experiments confirm the formation of phthalide and resorufin in the deprotection–cyclization based sensing mechanism. The cascade reaction strategy ensures the rapid release (t1/2 = 1.96 min) of pink fluorescent resorufin dye. Selective sensing of fluoride ions results in the 1820-fold fluorescence enhancement. The probe also displays a detection limit of 60 nM (i.e. 1.15 ppb) during the sensing of the ion in water. The permeability of the probe and sensing of intracellular fluoride ions is demonstrated by live cell imaging.

Performance comparison of two cascade reaction models in fluorescence off–on detection of hydrogen sulfide

Comparative studies on the performances of two cascade reaction based fluorescent H2S probes are reported. These probes were also designed to address the solubility issues of existing probes. The Reso-N3 probe favors the H2S mediated azide-to-amine reduction followed by a cyclization to release the resorufin fluorophore. Reso-Br undergoes a bromide-to-thiol nucleophilic substitution followed by a similar cyclization releasing the same fluorophore. Reso-N3 exhibited lower background fluorescence and better H2S sensing behavior in water compared to Reso-Br. Reso-Br underwent hydrolysis in aqueous buffer conditions (pH = 7.4) while, Reso-N3 was quite stable. Reso-N3 displayed high selectivity and sensitivity towards H2S. Live cell imaging of the species by the probe was also established.