Spectroscopic measurements of photoinduced processes in human skin after topical application of the hexyl ester of 5-aminolevulinic acid

Lu Zhao, Kristian P. Nielsen, Asta Juzeniene, Petras Juzenas, Vladimir Lani, Li Wei Ma, Knut Stamnes, Jakob J. Stamnes, Johan Moan

Research output: Contribution to journalArticlepeer-review

12 Scopus citations

Abstract

Although 5-aminolevulinic acid, ALA, and its derivatives, have been widely studied and applied in clinical photodynamic therapy (PDT), there is still a lack of reliable and non-invasive methods and technologies to evaluate physiological parameters of relevance for the therapy, such as erythema, melanogenesis, and oxygen level. We have investigated the kinetics of these parameters in human skin in vivo during and after PDT with the hexyl ester of ALA, ALA-Hex. Furthermore, the depth of photosensitizer (protoporphyrin IX, PpIX) production after different application times was investigated. It was found that the depth increased with increasing application time of ALA-Hex. We also investigated the depth of PpIX before and after light exposure causing 50% photobleaching at 407 nm. The PpIX localized in superficial layers of the normal tissue was removed during the bleaching. Thus, after bleaching, the remaining PpIX was localized mainly in the deeper! layers of normal tissue. We have applied fluorescence emission spectroscopy, fluorescence excitation spectroscopy, and reflectance spectroscopy in the study of the above-mentioned parameters. In conclusion, fluorescence excitation spectroscopy and reflectance spectroscopy are simple, useful, reliable, and noninvasive techniques in the evaluation of the processes taking place in human skin in vivo during and after PDT. Using these methods we were able to quantify melanogenesis, O2 level, erythema, vasoconstriction, and vasodilatation.

Original languageEnglish
Pages (from-to)307-320
Number of pages14
JournalJournal of Environmental Pathology, Toxicology and Oncology
Volume25
Issue number1-2
DOIs
StatePublished - 2006

Keywords

  • ALA-Hex PDT
  • Erythema
  • Fluorescence excitation spectroscopy
  • Melanogenesis
  • Oxygen
  • Reflectance spectroscopy

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