Development of a ratiometric time-resolved luminescence sensor for pH based on lanthanide complexes

Area of Science:

• Analytical Chemistry
• Biotechnology
• Materials Science

Background:

• Lanthanide complexes are valuable for time-resolved luminescence bioassays in diagnostics.
• Developing novel probes for sensitive and specific detection is crucial for biotechnology.

Purpose of the Study:

• To design and synthesize a novel terpyridine polyacid derivative (HTTA) for lanthanide complexation.
• To develop time-resolved luminescence and absorption-based ratiometric pH sensors using Eu(3+) and Tb(3+) complexes of HTTA.
• To demonstrate the application of these sensors for cell imaging.

Main Methods:

• Synthesis of a novel terpyridine polyacid derivative, (4'-hydroxy-2,2':6',2''-terpyridine-6,6''-diyl) bis(methylenenitrilo) tetrakis(acetic acid) (HTTA).
• Formation of stable lanthanide complexes: HTTA-Eu(3+) and HTTA-Tb(3+).
• Characterization of luminescence and UV absorption properties in response to pH changes.
• Cell loading of complexes using an acetoxymethyl ester derivative for imaging.

Main Results:

• HTTA-Eu(3+) luminescence intensity is pH-dependent (pK(a) = 5.8, pH 4.8-7.5), while HTTA-Tb(3+) is pH-independent.
• A ratiometric luminescence sensor was developed using the intensity ratio I(540 nm)/I(610 nm) for pH detection.
• A ratiometric absorption sensor was developed using the absorbance ratio A(290 nm)/A(325 nm) for pH detection (pH 4.0-7.0).
• Successful intracellular loading and time-resolved luminescence imaging in HeLa cells were achieved.

Conclusions:

• The HTTA-Eu(3+)/Tb(3+) mixture serves as a dual-mode (luminescence and absorption) ratiometric pH sensor.
• The developed sensor system demonstrates practical utility for time-resolved luminescence cell imaging.
• This work expands the toolkit for advanced bioassays and diagnostics.