Comparative in vitro percutaneous penetration of 5-aminolevulinic acid and two of its esters through excised hairless mouse skin.
OBJECTIVE
ALA esters have been developed to improve PpIX production in ALA-PDT, but they do not perform as well in skin as they do in cells and the bladder.


METHODS
The in vitro penetration across normal mouse skin of ALA and its methyl and hexyl ester was determined for different application concentrations. ALA and the esters were also applied to tape stripped skin to determine the effect of the stratum corneum.


RESULTS
The penetration of ALA and the esters was higher through tape stripped skin than through normal skin (P < 0.01), showing that the stratum corneum is an important barrier. The experiments with different application concentrations indicated that the skin penetration through normal skin and tape stripped skin is highest for ALA and lowest for the hexyl ester.


CONCLUSIONS
The differences in skin penetration properties could be (co-)responsible for the finding that ALA esters do not induce substantially higher PpIX levels in in vivo skin.
van den Akker
Johanna T H M
JT
School of Biochemistry and Molecular Biology, University of Leeds, Leeds LS2 9JT, United Kingdom.
Holroyd
J Andrew
JA
Vernon
David I
DI
Sterenborg
Henricus J C M
HJ
Brown
Stanley B
SB
D000279:Administration, Cutaneous; D000622:Aminolevulinic Acid / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000493:pharmacokinetics*; D000818:Animals; D046508:Culture Techniques; D004305:Dose-Response Relationship, Drug; D004817:Epidermis / Q000378:metabolism; D008297:Male; D051379:Mice; D008812:Mice, Hairless; D017319:Photosensitizing Agents / Q000008:administration & dosage / Q000493:pharmacokinetics*; D012869:Skin Absorption / Q000502:physiology*
D017319:Photosensitizing Agents; C114767:delta-aminolevulinic acid methyl ester; D000622:Aminolevulinic Acid; C419924:5-aminolevulinic acid hexyl ester