Trityl-based EPR probe with enhanced sensitivity to oxygen.

Area of Science:

• Organic Chemistry
• Analytical Chemistry
• Biophysics

Background:

• Triarylmethyl radicals are widely used as spin probes in Electron Paramagnetic Resonance (EPR) spectroscopy.
• Existing triarylmethyl-based oxygen sensors, like Oxo63, have limitations in sensitivity at low oxygen partial pressures.
• Accurate measurement of oxygen levels is crucial for understanding cellular respiration and disease states like hypoxia.

Purpose of the Study:

• To synthesize and characterize a novel asymmetric triarylmethyl radical derivative, TAM-H, for EPR-based oxygen sensing.
• To evaluate the sensitivity and performance of TAM-H compared to existing oxygen probes, particularly at low oxygen pressures.
• To demonstrate the application of TAM-H in monitoring oxygen consumption in biological systems, such as cancer cells.

Main Methods:

• Synthesis of the asymmetric triarylmethyl radical derivative, TAM-H, featuring aldehyde and carboxyl groups.
• Characterization of TAM-H using Electron Paramagnetic Resonance (EPR) spectroscopy under varying oxygen conditions.
• Comparative analysis of TAM-H sensitivity against the Oxo63 probe using Met-1 cancer cells to monitor oxygen consumption.

Main Results:

• TAM-H exhibits a distinct EPR spectral signature (doublet of narrow lines) sensitive to oxygen partial pressure.
• The TAM-H probe demonstrates significantly enhanced sensitivity to oxygen compared to Oxo63, especially below 20 mm Hg.
• TAM-H enables prolonged EPR measurements of oxygen depletion in cancer cells, down to anoxic levels (

Conclusions:

• The asymmetric TAM-H radical is a highly sensitive and effective probe for EPR-based oxygen detection.
• TAM-H overcomes the limitations of existing probes, allowing measurements in a broader oxygen pressure range, including physiological hypoxia.
• This novel probe facilitates advanced studies of cellular oxygen dynamics and has potential applications in cancer research and diagnostics.