A Step Toward ESIPT-Based Mitochondrial Probe That Responds to ATP Level

Area of Science:

• Organic Chemistry
• Biophysical Chemistry
• Analytical Chemistry

Background:

• Excited state intramolecular proton transfer (ESIPT) probes are valuable tools in chemical sensing.
• Developing probes with large Stokes' shifts and specific cellular targeting is crucial for biological imaging.

Purpose of the Study:

• To synthesize and characterize a novel ESIPT probe with a benzoindolium terminal group.
• To investigate the probe's fluorescence properties and its potential for detecting adenosine triphosphate (ATP) in biological cells.

Main Methods:

• Synthesis of the benzoindolium-based ESIPT probe.
• Spectroscopic analysis including fluorescence emission and quantum yield measurements.
• Cellular staining and imaging experiments to assess probe localization and response to ATP levels.

Main Results:

• The synthesized probe exhibits a large Stokes' shift (Δλ≈ 250 nm) and a good fluorescence quantum yield (φfl≈0.2).
• The probe shows a minor equilibrium involving deprotonation of the phenolic proton, leading to dual-channel fluorescence responses.
• The probe selectively targets intracellular mitochondria and displays altered near-infrared (NIR) emission upon inhibition of cellular ATP production.

Conclusions:

• A novel ESIPT probe with desirable photophysical properties has been developed.
• The probe demonstrates potential as a reaction-based sensor for intracellular ATP detection in mitochondria.
• The dual-channel response and mitochondria-specific targeting offer unique advantages for biological sensing applications.