NIR- and FRET-Based Sensing of Cu²⁺ and S^2- in Physiological Conditions and in Live Cells

Abstract

We have synthesized a new indole functionalized rhodamine derivative L(1) which specifically binds to Cu(2+) in the presence of large excess of other competing ions with visually observable changes in their electronic and fluorescence spectral behavior. These spectral changes are significant enough in the NIR and visible region of the spectrum and thus enable naked eye detection. The receptor, L(1), could be employed as a resonance energy transfer (RET) based sensor for detection of Cu(2+) based on the process involving the donor indole and the acceptor Cu(2+) bound xanthene fragment. Studies reveal that L(1)-Cu complex is selectively and fully reversible in presence of sulfide anions. Further, fluorescence microscopic studies confirmed that the reagent L(1) could also be used as an imaging probe for detection of uptake of these ions in HeLa cells.

Fluorescent probes for hydrogen sulfide detection and bioimaging

“…73 The probe employed the resonance energy transfer (RET) mechanism for the detection of Cu 2+ , the process of which involved a donor indole and an acceptor Cu 2+ bound rhodamine moiety. The Cu 2+ complex gave an on-off response in the presence of S 2À .…”

A “turn-on” fluorescent and colorimetric sensor for selective detection of Cu2+ in aqueous media and living cells

“…As can be found from the inset of Fig. 4, there was a good linearity between the fluorescence intensity and the concentrations of Cu 2+ in the range of 0.5 to 10 µM with a detection limit [42,43] …”

Near-infrared quantum dots based fluorescent assay of Cu2+ and in vitro cellular and in vivo imaging

“…In presence of higher concentration of aggregates, the effect was more prominent and indicated a dose-dependent cytotoxic effect on HeLa cells. This phenomenon may be caused from cytotoxic and antiproliferative effects of copper complex on cancer cells [45]. Subsequently, HeLa cells were selected as the living model to investigate the capability of CdTe/CdS QDs to monitor the change of Cu 2+ concentration.…”