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Proceedings Paper

Mechanism of in-vivo photodynamic effects
Author(s): Peter Strizhak; Tamas Kriska; Dezso Gal
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Paper Abstract

In order to compare the efficiency of the three different mechanisms suggested for photosensitization in biology and medicine: the sensitizer radical, (Type I), the singlet oxygen (Type II), and the native free radical-triplet sensitizer interaction (MTO mechanism) mediated effects, a possible mechanism is suggested including the primary steps of all three mechanisms. Simulation and sensitivity tests based on this mechanism have revealed: that (i) the main contributing elementary steps to the overall photodynamic effect are the decay of the triplet sensitizer; the interaction of sensitizer radicals with biomolecules and the interactions of native free radicals with biomolecules. (ii) The extent of the contribution of the latter is determined by the concentration of the native free radicals in the tissue preceding illumination. (iii) By changing the assumed rate constants of the triplet-doublet interactions it has been established, that with the decrease of their rate constants the overall photodynamic effect decreases. And (iv) its contribution might become negligible. Kinetic consideration has shown, that while continuous illumination results in steady states, illumination by pulsing light leads to non-steady states of the transient species and the latter enables the distinction between the mechanisms provided one of them is predominant under conditions of the measurements.

Paper Details

Date Published: 31 January 1996
PDF: 13 pages
Proc. SPIE 2625, Photochemotherapy: Photodynamic Therapy and Other Modalities, (31 January 1996); doi: 10.1117/12.230962
Show Author Affiliations
Peter Strizhak, Central Research Institute for Chemistry (Hungary)
Tamas Kriska, Central Research Institute for Chemistry (Hungary)
Dezso Gal, Central Research Institute for Chemistry (Hungary)


Published in SPIE Proceedings Vol. 2625:
Photochemotherapy: Photodynamic Therapy and Other Modalities
Benjamin Ehrenberg; Giulio Jori; Johan Moan, Editor(s)

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