Phenothiazine-rhodamine-based colorimetric and fluorogenic 'turn-on' sensor for Zn2+ and bioimaging studies in live cells.

A phenothiazine-rhodamine (PTRH) fluorescent dyad was synthesized and its ability to selectively sense Zn2+ ions in solution and in in vitro cell lines was tested using various techniques. When compared with other competing metal ions, the PTRH probe showed the high selectivity for Zn2+ ions that was supported by electronic and emission spectral analyses. The emission band at 528 nm for the PTRH probe indicated the ring closed form of PTRH, as for Zn2+ ion binding to PTRH, the λem get shift to 608 nm was accompanied by a pale yellow to pink colour (under visible light) and green to pinkish red fluorescence emission (under UV light) due to ring opening of the spirolactam moiety in the PTRH ligand. Spectral overlap of the donor emission band and the absorption band of the ring opened form of the acceptor moiety contributed towards the fluorescence resonance energy transfer ON mechanism for Zn2+ ion detection. The PTRH sensor had the lowest detection limit for Zn2+ , found to be 2.89 × 10-8  M. The sensor also demonstrated good sensing application with minimum toxicity for in vitro analyses using HeLa cells.

A Fluorescent Turn-On Carbazole-Rhodanine Based Sensor for Detection of Ag+ Ions and Application in Ag+ Ions Imaging in Cancer Cells.

Carbazole - Rhodanine conjugate is an effective fluorescent host for silver ions through fluorometric transformation from green to red color with a hyperchromic emission. An intramolecular charge transfer process derived from carbazole towards rhodanine favors interaction of thiocarbonyl S and carboxylic acid O of the rhodanine moiety towards Ag+ ion. Carbazole - rhodanine dyad accomplishes the lowest detection limit of 12.8 × 10-9 M and high quantum efficiency. A fluorescence reversibility of the probe with I- ion surges reutilization of sensor molecule as an Ag+ ion probe with minimal loss in the fluorescent efficiency. This fluorescent ligand is a biocompatible probe and is also a proficient candidate for fluorescent imaging of Ag+ ion in live cells.