Mercury ion-selective fluorescent probe based on indazole fused rhodamine and cell imaging application

Developing selective and sensitive probes for mercury ion (Hg2+) is of great significance because Hg2+ exhibits high toxicity and poses a potential threat to public health and the environment. Herein, a newly designed indazole fused rhodamine dye InRh has been prepared, which shows stable fluorescent signals in water at a wide pH range of 1.0-10.0. Based on the dye InRh, a novel fluorescent probe InRhH for Hg2+ is further developed by modifying the spirolactone ring of InRh to form a closed spirolactam ring. The probe shows selective fluorescence off-on signal changes to Hg2+ with a visible color change and response time of 40 min in H2O/CH3CN (pH = 6.0, v/v = 4/1), and the detection limit for Hg2+ is measured to be 0.33 nM. The recognition mechanism for Hg2+ can be ascribed to the binding interactions between Hg2+ and probe in a 2: 1 coordination mode, which promotes the occurrence of spirolactam ring opening and further hydrolysis. In addition, the InRhH can be applied for test strip experiments and tracing 10-6 M level Hg2+ with visible color change. Furthermore, the suitable cytotoxicity allows the probe to apply for sensing Hg2+ in living HeLa cells by fluorescence imaging.

Automated summary

Developing selective and sensitive probes for mercury ion (Hg2+) is crucial due to its high toxicity and threat to public health and the environment. A new dye InRh has been prepared, which exhibits stable fluorescent signals in water over a wide pH range. A novel fluorescent probe InRhH for Hg2+ has been developed based on InRh, showing selective fluorescence off-on signal changes with a visible color change and a response time of 40 min. The probe can be applied for test strip experiments and detects Hg2+ at a level of 10-6 M with visible color change, and it can also be used for sensing Hg2+ in living cells by fluorescence imaging.