Kinetics of Photobleaching of Protoporphyrin IX in the Skin of Nude Mice Exposed to Different Fluence Rates of Red Light |
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Authors: | Roar Sorensen Vladimir Lani Johan Moan |
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Institution: | Department of Biophysics, Institute for Cancer Research, Oslo, Norway |
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Abstract: | Abstract— The purpose of the present study was to determine the kinetics and the fluence rate dependency of the photo-bleaching of protoporphyrin IX (PpIX) in normal skin of Balb/c nude mice after systemic and topical application of 5-aminolevulinic acid (ALA). ALA was administered systemically (200 mg/kg body weight, i.p.) and topically (20% w/w ALA cream) to the mice. Fluences of up to 40 J/cm2 were delivered by a dye laser (636 nm) at fluence rates of 37.5, 75, 150, 300 and 500 mW/cm2. The photo-bleaching rate was constant within this range of fluence rates. This result suggests that there is no oxygen effect for PpIX photobleaching in this region for the skin of Balb/c nude mice. During light exposure the fluorescence decay followed neither first- nor second-order kinetics. The decay rate was slightly faster after systemic application than after topical application of ALA, but did not depend on the time (1–8 h) between application and analysis. |
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