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Comparison of ALA- and ALA hexyl-ester-induced PpIX depth distribution in human skin carcinoma

Paper ID Volume ID Publish Year Pages File Format Full-Text
30480 44481 2008 9 PDF Available
Title
Comparison of ALA- and ALA hexyl-ester-induced PpIX depth distribution in human skin carcinoma
Abstract

Photodynamic therapy (PDT) based on the use of photoactivable porphyrins, such as protoporphyrin IX (PpIX), induced by the topical application of amino-levulinic acid (ALA) or its derivatives, ALA methyl-ester (m-ALA), is a treatment for superficial basal cell carcinoma (BCC), with complete response rates of over 80%. However, in the case of deep, nodular-ulcerative lesions, the complete response rates are lower, possibly related to a lower bioavailability of PpIX. Previous in vitro skin permeation studies demonstrated an increased penetration of amino-levulinic acid hexyl-ester (h-ALA) over ALA. In this study, we tested the validity of this approach in vivo on human BCCs. An emulsion containing 20% ALA (w/w) and preparations of h-ALA at different concentrations were applied topically to the normal skin of Caucasian volunteers to compare the PpIX fluorescence intensities with an optical fiber-based spectrofluorometer. In addition, the PpIX depth distribution and fluorescence intensity in 26 BCCs were investigated by fluorescence microscopy following topical application of 20% ALA and 1% h-ALA. We found that, for application times up to 24 h, h-ALA is identical to ALA as a PpIX precursor with respect to PpIX fluorescence intensity, depth of penetration, and distribution in basal cell carcinoma, but has the added advantage that much smaller h-ALA concentrations can be used (up to a factor 13). We observed a non-homogenous distribution in BCCs with both precursors, independent of the histological type and depth of invasion in the dermis.

Keywords
Basal cell carcinoma (BCC); Photodynamic therapy (PDT); 5-aminolevulinic acid (ALA); 5-aminolevulinic acid ester (ALA-ester); Protoporphyrin IX (PpIX); Fluorescence spectroscopy
First Page Preview
Comparison of ALA- and ALA hexyl-ester-induced PpIX depth distribution in human skin carcinoma
Publisher
Database: Elsevier - ScienceDirect
Journal: Journal of Photochemistry and Photobiology B: Biology - Volume 93, Issue 3, 11 December 2008, Pages 140–148
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Bioengineering