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Photodynamic Effectiveness and Vasoconstriction in Hairless Mouse Skin after Topical 5‐Aminolevulinic Acid and Single‐ or Two‐fold Illumination
Author(s) -
Veen Nynke,
Hebeda Konnie M.,
Bruijn Henriëtte S.,
Star Willem M.
Publication year - 1999
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/j.1751-1097.1999.tb08303.x
Subject(s) - hairless , vasoconstriction , chemistry , skin fold , fold (higher order function) , pig skin , pharmacology , medicine , biochemistry , endocrinology , computer science , food science , programming language , body mass index
Several options were investigated to increase the efficacy of photodynamic therapy (PDT) using protoporphyrin IX (PpIX) induced by topically applied 5‐aminolevulinic acid (ALA). Hairless mice with normal skin or UVB‐light‐induced skin changes were used as a model. In the first part of the study animals were illuminated immediately (t = 4) or 6 h (t = 10, PpIX fluorescence maximum) after the end of a 4 h ALA application. A total incident light fluence of 100 J/cm 2 (514.5 nm) was delivered at a fluence rate of 100 or 50 mW/cm 2 . The PDT‐induced damage to normal skin was more severe after treatment at t = 10 than at t = 4. Illumination at 50 mW/ cm 2 caused significantly more visible damage than the same light fluence given at 100 mW/cm 2 . For UVB‐illu‐minated skin, different intervals or fluence rates made no significant difference in the severity of damage, although some qualitative differences occurred. In situ fluence rate measurements during PDT indicated vasoconstriction almost immediately after the start of the illumination. A fluorescein exclusion assay after PDT demonstrated vasoconstriction that was more pronounced in UVB‐treated skin than in normal skin. The second part of the study examined the effect of two illuminations. The first illumination bleaches the PpIX fluorescence. At the start of the second illumination, new PpIX had been formed. Light of 514.5 nm was delivered at 100 mW/cm 2 to a total incident light fluence of 200 J/cm 2 at t = 4 (single illumination) or 100 J/cm 2 at t = 4 plus 100 J/cm 2 at t = 10. There was no visual difference in skin damage between 100 and 200 J/cm 2 single illumination. Two‐fold illumination (100 + 100 J/cm 2 ) caused significantly more skin damage, indicating a potentially successful option for increasing the efficacy of topical ALA‐PDT.