29 December 1997 Detection of oxygen-based radicals using electron spin resonance under PDT conditions
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The standard theories about the mechanisms involved in PDT concern themselves primarily with oxygen-centered species, above all singlet oxygen (1O2) and the hydroxyl radical (OH). The efficacy of the therapy depends very much not only on the photosensitizer used, but also to a great extent on the choice of irradiation parameters, the light source, and the tissue's degree of oxygenation. Both clinical and experimental studies point to the fact that the treatment of hypoxic areas generally results in a disappointing response, and the effects of the changes in perfusion and oxygenation induced by the PDT itself certainly complicate any analysis. The radical nature both of the secondary products generated from singlet oxygen reactions and of the other hypothesized primary products themselves mean that the physical method of choice for research on PDT is electron spin resonance (ESR). The aim of our investigations was the gathering of the particular information that this method could yield in order to make a comparison of the degrees to which various photosensitizers produce both singlet oxygen and hydroxide radicals in vitro. We also dedicated part of our efforts to an investigation into the effects of a simple variation in the partial pressure of the dissolved molecular oxygen.
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Bernd Algermissen, Bernd Algermissen, Basil Jamil, Basil Jamil, Kurt Osterloh, Kurt Osterloh, Hans-Peter Berlien, Hans-Peter Berlien, } "Detection of oxygen-based radicals using electron spin resonance under PDT conditions", Proc. SPIE 3191, Photochemotherapy: Photodynamic Therapy and Other Modalities III, (29 December 1997); doi: 10.1117/12.297808; https://doi.org/10.1117/12.297808

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