Photophysical investigations of a FRET-based bifluorophoric conjugate and its Hg(II) specific ratiometric ‘turn-on’ signalling

Anti-cancer potential of substituted "amino-alkyl-rhodamine" derivatives against MCF-7 human breast cancer cell line

Breast cancer is the most prevalent diagnosed cancer among women and the main cause of morbidity and mortality. As for breast cancer, MCF-7 cells are an important candidate since they are widely utilized in research for estrogen receptor (ER)-positive breast cancer cell assays, and various sub-clones have been identified to reflect different classes of ER-positive tumors with varied levels of nuclear receptor expression. Rhodamines and its derivatives have shown a great interest over the past two decades due to their excellent structural and spectroscopic properties. Rhodamine derivatives have been widely investigated for their mitochondrial targeting and chemotherapeutic properties. Rhodamine derivatives, in particular, have been widely investigated for their therapeutic properties. In this regard, several studies have shown that rhodamine dye derivatives have promising in vitro and in vivo therapeutic efficacy. The present study deals with potential anticancer activity of few synthesized rhodamine derivatives against MCF-7 cell lines.

A Pyrene-Rhodamine FRET couple as a chemosensor for selective detection of picric acid

Selective detection of nitroaromatic compounds such as Picric acid (PA), those being explosive materials and hazardous pollutants of environmental and biological concern is highly desirable. With the operational advantages of the chemosensing approach, a pyrene-rhodamine-B couple (1) was explored in this investigation as a ratiometric molecular probe for selective and sensitive detection of picric acid. The bi-fluorophoric probe displayed absorption and fluorescence enhancements along with colourless to reddish-brown colour transition as signaling responses in the selective presence of PA among all the nitro aromatic analyte investigated. The signaling module relies on PA- mediated modulation of various operational photo-physical processes such as (a) inhibition of photo-induced electron transfer (PET) operative from amino-donor to excited pyrene (b) a conformational translation through spiro-ring opening of rhodamine-B segment, and (c) initiation of Fluorescence Resonance Energy Transfer (FRET) between excited pyrene donor and ring-opened rhodamine acceptor. The ratio of fluorescence from both fluorophores (pyrene and Rhodamine) as output channel displayed sensitive signaling performance (LOD = 13.8 nM) in the detection of PA. The investigation that inferred to the PA-induced selectivity in signalling, higher binding affinity (log K_a≈11), a faster response time, and reversibility in signalling with a counter analyte and an operational pH range established the probe's efficacy as a chemosensor for PA detection.

A New Molecular Probe for Colorimetric and Fluorometric Detection and Removal of Hg2+ and its Application as Agarose Film-Based Sensor for On-Site Monitoring

A new molecule incorporating two units of 7-nitro-benzoxadiazole (NBD), bridged by m-xylylenediamine, was synthesized and characterized on the basis of analytical and spectroscopic techniques. The metal ion sensing property of this molecule was studied spectroscopically with a large number of metal ions. This study revealed that it can perform as a dual-channel probe for colorimetric as well as fluorometric detection of Hg²⁺. In presence of Hg²⁺, a substantial change in UV-Vis spectrum with the appearance of a new band at 545 nm and a distinct colour change from yellow to red was observed. In the fluorescence spectrum, the intensity of the emission band was substantially quenched only upon addition of Hg²⁺. No significant interference from any other metal ion used in this study was noted, the limit of detection (LOD) for Hg²⁺ was found to be 60 and 10 nM for colorimetric and fluorometric detection method, respectively. This new chemosensor was used for removal of Hg²⁺ from aqueous solution with 92% efficiency. For on-site monitoring and field application, this molecule was immobilized into the agarose based hydrogel film, which was used successfully for detection of Hg²⁺ in water. The study on reversible behaviour of this chemosensor revealed that it can be recycled in solution as well as in solid phase by treatment with Na₂S.

Two-step FRET mediated metal ion induced signalling responses in a probe appended with three fluorophores

A tri-fluorophore appended Tren receptor based probe exhibited chelation induced ratiometric fluorescence signalling through a two-step FRET process; enhancement of F_An→ F_Rhenergy transfer efficiency through an F_NBDintermediate was observed.

Rhodamine-based ratiometric fluorescent probes based on excitation energy transfer mechanisms: construction and applications in ratiometric sensing

Rhodamine is a convenient platform for the construction of “OFF–ON” ratiometric excitation energy transfer fluorescent probes.