Mercury(II) recognition and fluorescence imaging in vitro through a 3D-complexation structure.

Area of Science:

• Analytical Chemistry
• Supramolecular Chemistry
• Materials Science

Background:

• Mercury ions (Hg2+) pose significant environmental and health risks.
• Development of selective and sensitive Hg2+ sensors is crucial for environmental monitoring and biological studies.
• Existing Hg2+ detection methods often face challenges with selectivity, sensitivity, or biocompatibility.

Purpose of the Study:

• To synthesize and characterize a novel chemosensor, 8,8'-(1,4,10,13-Tetrathia-7,16-diazacyclooctadecane-7,16-diyl)-bis(methylene)diquinolin-7-ol (TTBQ), for selective Hg2+ recognition.
• To investigate the complexation behavior and sensing mechanism of TTBQ with Hg2+.
• To evaluate the sensor's performance for in vitro Hg2+ detection using fluorescence imaging.

Main Methods:

• Synthesis and single-crystal growth of TTBQ and its Hg2+ complex.
• Spectroscopic analysis (UV-Vis, fluorescence) to study Hg2+ binding.
• Association constant determination via titration experiments.
• X-ray crystallography to elucidate the complex structure.
• Evaluation of selectivity against various metal ions.
• Biocompatibility assessment and in vitro fluorescence imaging experiments.

Main Results:

• TTBQ was successfully synthesized and formed a stable Hg2+/TTBQ complex with a high association constant (Ka ≈ 1.3 x 10^4 M⁻¹).
• X-ray crystallography revealed a unique cagelike structure of the Hg2+ complex, confirming TTBQ's ability to trap Hg2+.
• The Hg2+/TTBQ complex exhibited a significant 25-fold luminescence enhancement with a sub-micromolar detection limit.
• TTBQ demonstrated excellent selectivity for Hg2+ over other common metal ions.
• The sensor performed effectively in the pH range of 5.5–7.5 and showed good biocompatibility for in vitro applications.

Conclusions:

• TTBQ is a highly selective and sensitive chemosensor for Hg2+ detection in aqueous solutions.
• The cagelike complex structure is key to the enhanced luminescence and sensing capabilities.
• TTBQ shows promise for practical applications in environmental monitoring and biological imaging of mercury.
• The sensor's performance in a biologically relevant pH range and its biocompatibility support its use in vitro.