title: Fluorescence photobleaching of ALA and ALA-heptyl ester induced protoporphyrin IX during photodynamic therapy of normal hairless mouse skin: a comparison of two light sources and different illumination schemes.
abstract: This study investigated photobleaching of protoporphyrin IX (PpIX) induced by 5-aminolevulinic acid (ALA) and ALA-heptyl ester during superficial photodynamic therapy (PDT) in normal skin of the female BALB/c-nu/nu athymic mouse. We examined the effects of two light sources (laser and broadband lamp) and two different illumination schemes (fractionated light and continuous irradiation) on the kinetics of photobleaching. Our results show that light exposure (0-30 minutes, 10 mW/cm2) of wavelengths of approximately 420 nm (blue light) and 635 nm (red light) induced time-dependent PpIX photobleaching for mouse skin of 2% ALA and ALA-heptyl ester. Blue light (10 mW/cm2) caused more rapid PpIX photobleaching than did red light (100 mW/cm2), which is attributed to stronger absorption at 407 nm than at 632 nm for PpIX. In the case of light fractionation, fractionated light induced faster photobleaching compared with continuous light exposure after topical application of 2% ALA and ALA-heptyl ester in vivo. These have been suggested to allow reoxygenation of the irradiated tissue, with a consequent enhancement of singlet oxygen production in the second and subsequent fractions.
authors: Department of Radiation Biology, Institute for Cancer Research, Rikshospitalet-Radiumhospitalet Medical Center, Montebello, Oslo, Norway. pu_dron9@hotmail.com
authors: Xiao
authors: X
authors: Pudroma
authors: Asta
authors: A
authors: Juzeniene
authors: Li-Wei
authors: LW
authors: Ma
authors: Vladimir
authors: V
authors: Iani
authors: Johan
authors: J
authors: Moan
mesh_terms: D000622:Aminolevulinic Acid / Q000494:pharmacology*; D000818:Animals; D004952:Esters / Q000494:pharmacology*; D005260:Female; D005453:Fluorescence; D007834:Lasers; D008027:Light; D051379:Mice; D008812:Mice, Hairless; D008807:Mice, Inbred BALB C; D023421:Models, Animal; D010100:Oxygen / Q000378:metabolism; D038761:Photobleaching / Q000187:drug effects* / Q000528:radiation effects; D010778:Photochemotherapy / Q000379:methods*; D011524:Protoporphyrins / Q000378:metabolism*; D012867:Skin / Q000187:drug effects* / Q000378:metabolism*; D013997:Time Factors
chemical_list: D004952:Esters; D011524:Protoporphyrins; D000622:Aminolevulinic Acid; C028025:protoporphyrin IX; D010100:Oxygen