Related Experiment Video
Updated: Jul 4, 2025
Tumor Hypoxia Assessment: In Vivo 3D Oxygen Imaging Through Electron Paramagnetic Resonance
Published on: February 14, 2025
EPR Monitoring of Oxygenation Levels in Tumors After Chlorophyllide-Based Photodynamic Therapy May Allow for Early
Małgorzata Szczygieł1, Barbara Kalinowska2, Dariusz Szczygieł2
1Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University, Krakow, Poland. gosia.szczygiel@uj.edu.pl.
Purpose:
Molecular oxygen, besides a photosensitizer and light of appropriate wavelength, is one of the three factors necessary for photodynamic therapy (PDT). In tumor tissue, PDT leads to the killing of tumor cells, destruction of endothelial cells and vasculature collapse, and the induction of strong immune responses. All these effects may influence the oxygenation levels, but it is the vasculature changes that have the main impact on pO2. The purpose of our study was to monitor changes in tumor oxygenation after PDT and explore its significance for predicting long-term treatment response.
Procedures:
Electron paramagnetic resonance (EPR) spectroscopy enables direct, quantitative, and sequential measurements of partial pressure of oxygen (pO2) in the same animal. The levels of chlorophyll derived photosensitizers in tumor tissue were determined by transdermal emission measurements.
Results:
The noninvasive monitoring of pO2 in the tumor tissue after PDT showed that the higher ΔpO2 (pO2 after PDT minus pO2 before PDT), the greater the inhibition of tumor growth. ΔpO2 also correlated with higher levels of the photosensitizers in the tumor and with the occurrence of a severe edema/erythema after PDT.
Conclusion:
Monitoring of PDT-induced changes in tumor oxygenation is a valuable prognostic factor and could be also used to identify potentially resistant tumors, which is important in predicting long-term treatment response.
