A europium(III) complex as an efficient singlet oxygen luminescence probe

Area of Science:

• Coordination Chemistry
• Analytical Chemistry
• Biophysical Chemistry

Background:

• Singlet oxygen ((1)O2) is a reactive oxygen species involved in various biological processes.
• Developing sensitive and selective probes for (1)O2 detection is crucial for understanding its role in biological systems.
• Existing methods for (1)O2 detection often face challenges with sensitivity, selectivity, or applicability in complex biological environments.

Purpose of the Study:

• To design and synthesize a novel europium(III) complex as a highly sensitive and selective time-gated luminescence probe for singlet oxygen ((1)O2).
• To characterize the photophysical properties and reactivity of the new probe with (1)O2.
• To demonstrate the probe's applicability in detecting (1)O2 generated in vitro and in living cells using time-gated luminescence imaging.

Main Methods:

• Synthesis and characterization of a new europium(III) complex: [4'-(10-methyl-9-anthryl)-2,2':6',2"-terpyridine-6,6"-diyl]bis(methylenenitrilo) tetrakis(acetate)-Eu(3+).
• Investigation of the probe's water solubility, stability constant, and pH range.
• Measurement of the reaction rate constant with (1)O2 and changes in luminescence quantum yield and lifetime upon endoperoxide formation.
• Demonstration of (1)O2 detection in various chemical systems and subsequent imaging in living HeLa cells.

Main Results:

• The synthesized europium(III) complex exhibits high water solubility, a large stability constant (~10^21), and a wide pH range (3-10).
• The probe reacts specifically with (1)O2 at a high rate (10^10 M(-1) s(-1)), leading to a significant increase in luminescence quantum yield (0.90% to 13.8%) and lifetime (0.80 to 1.29 ms).
• Successful detection of (1)O2 in MoO(4)(2-)/H(2)O2, TMPyP photosensitization, and HRP/IAA systems, and its imaging in living HeLa cells via time-gated luminescence imaging.

Conclusions:

• The novel europium(III) complex is a highly effective time-gated luminescence probe for singlet oxygen ((1)O2) with excellent sensitivity and selectivity.
• The probe's favorable properties and successful application in cellular imaging highlight its potential for biological research and diagnostics.
• Time-gated luminescence imaging offers a robust method for monitoring (1)O2 generation in living cells, overcoming background fluorescence interference.