Novel integrated sensing system of calixarene and rhodamine molecules for selective colorimetric and fluorometric detection of Hg2+ ions in living cells

Three novel and facile calixarene derivatives (5, 6 and 7), which were appended with four rhodamine units at the upper rim of calixarene skeleton, were firstly prepared and evaluated for selective detection of metal ions in solution. Receptors (5) and (7) indicated immediate turn on fluorescence output toward Hg²⁺ ions over other most competitive metal ions with the ultralow detection limits, indicating their high efficiency and reliability. The binding response to Hg²⁺ ions in solution was also observed through a chromogenic change (from colorless to pale pink). Furthermore, in vitro and bio-imaging studies with MCF-7 or MIA PaCa-2 cell lines were also performed to investigate the use of receptors in biological systems in order to monitor of mercury ions. Results showed that new receptors (5) or (7) were cell permeable and suitable for real-time imaging of Hg²⁺ in living cells (MCF-7) or (MIA PaCa-2) without any damage to healthy cell lines (HEK 293).

Unusual absence of FRET in triazole bridged coumarin-hydroxyquinoline, an active sensor for Hg2+ detection

A triazole-bridged coumarin conjugated quinoline sensor has been 'click'-synthesized by Cu(i) catalyzed Huisgen cycloaddition, and it exhibited high selectivity for toxic Hg2+. Surprisingly, no evidence of energy transfer from the quinoline moiety to coumarin has been found, substantiated by time-resolved fluorescence study. The possible binding mode of this sensor to Hg2+ has been established via NMR study, steady-state and time-resolved fluorescence spectroscopy, which is further supported by TDDFT calculations. The sensor has been found to be cell membrane permeable and non-toxic, and hence is suitable for intracellular Hg2+ detection.

Thieno[3,2-c]pyran: an ESIPT based fluorescence “turn-on” molecular chemosensor with AIE properties for the selective recognition of Zn2+ ion

Thieno[3,2-c]pyran was synthesized as a fluorescent turn-on chemosensor for the selective recognition of Zn²⁺ ions with a low detection limit (0.67 μM), and it also exhibited AIE properties.

Rhodamine–benzothiazole conjugate as an efficient multimodal sensor for Hg2+ ions and its application to imaging in living cells

A rhodamine B dye bearing a benzothiazole conjugate is designed and synthesized, it shows a highly selective and sensitive naked-eye color change and turn-on fluorescence response to Hg²⁺ ions.

Water switched aggregation/disaggregation strategies of a coumarin–naphthalene conjugated sensor and its selectivity towards Cu2+ and Ag+ ions along with cell imaging studies on human osteosarcoma cells (U-2 OS)

A simple coumarin–naphthalene conjugated chemosensor (R1) exhibited an excellent AIE effect in methanol/water (1 : 1).

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.

Intracellular detection of hazardous Cd2+ through a fluorescence imaging technique by using a nontoxic coumarin based sensor

A new coumarin based turn on fluorescent sensor (R1) was reported for the detection of highly hazardous Cd²⁺ with excellent selectivity and sensitivity without any interference of other metal ions.