The mechanism of Photofrin photobleaching and its consequences for photodynamic dosimetry

I. Georgakoudi, Michael G. Nichols, T. H. Foster

Research output: Contribution to journalArticle

201 Citations (Scopus)

Abstract

We report experimental results that support a theory of self-sensitized singlet oxygen-mediated bleaching of the porphyrin photosensitizer Photofrin. Microelectrode measurements of photodynamic oxygen consumption were made near the surface of individual, Photofrinsensitized EMT6 spheroids during laser irradiation. The progressive decrease in photochemical oxygen consumption with sustained irradiation is consistent with a theory in which bleaching occurs via self-sensitized singlet oxygen reaction with the photosensitizer ground state. A bleaching model based solely on absorbed optical energy density is inconsistent with the data. Photobleaching has a significant effect on calculated photodynamic dose distributions in 500 μm diameter spheriods. Dose distributions corrected for the effects of bleaching produce a new estimate (12.1 ± 1.2 mM) for the threshold dose of reacting singlet oxygen in this system.

Original languageEnglish
Pages (from-to)135-144
Number of pages10
JournalPhotochemistry and Photobiology
Volume65
Issue number1
StatePublished - Jan 1997
Externally publishedYes

Fingerprint

Dihematoporphyrin Ether
Photobleaching
Singlet Oxygen
bleaching
Bleaching
Dosimetry
dosimeters
Photosensitizing Agents
oxygen consumption
Oxygen Consumption
dosage
oxygen
Porphyrins
Microelectrodes
Oxygen
irradiation
spheroids
Lasers
Laser beam effects
porphyrins

All Science Journal Classification (ASJC) codes

  • Biochemistry, Genetics and Molecular Biology(all)
  • Biochemistry
  • Biophysics

Cite this

The mechanism of Photofrin photobleaching and its consequences for photodynamic dosimetry. / Georgakoudi, I.; Nichols, Michael G.; Foster, T. H.

In: Photochemistry and Photobiology, Vol. 65, No. 1, 01.1997, p. 135-144.

Research output: Contribution to journalArticle

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