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Novel patch-based systems for the localised delivery of ALA-esters

Paper ID Volume ID Publish Year Pages File Format Full-Text
30966 44522 2010 11 PDF Available
Title
Novel patch-based systems for the localised delivery of ALA-esters
Abstract

In photodynamic therapy (PDT) a combination of visible light and a sensitising drug causes the destruction of selected cells. Aminolaevulinic acid (ALA) has been widely used in topical PDT for over 15 years. However, ALA does not possess favourable physicochemical properties for skin penetration. Consequently, the clearance rates for difficult to treat lesions, such as nodular basal cell carcinomas are relatively low.For the first time, equimolar concentrations of ALA, methyl-ALA (m-ALA) and hexyl-ALA (h-ALA) have been incorporated into a bioadhesive patch-based system. In vitro penetration studies into excised porcine skin revealed that ALA patches containing relatively high loadings (226.7 μmol cm−2) were associated with significantly greater tissue concentrations (70.7 μmol cm−3) than patches containing m-ALA (16.3 μmol cm−3) or h-ALA (17.4 μmol cm−3). ALA was also found to be the most efficient inducer of protoporphyrin (PpIX) fluorescence in mice, in vivo (maximum mean fluorescence: ALA = 236.2 a.u., m-ALA = 175.1 a.u., h-ALA = 193.5 a.u.). However, when the lipophilic hexylester was formulated in a pressure sensitive adhesive (PSA) patch, significantly higher PpIX levels were achieved compared to all bioadhesive systems tested. Of major importance, PSA patches containing relatively low h-ALA loadings induced high PpIX levels, which were localised to the application area.This study has highlighted the importance of rational selection of both the active agent and the delivery system. Bioadhesive preparations containing ALA are ideal for delivery to moist environments; whereas h-ALA-loaded PSA systems may facilitate enhanced delivery to dry areas of skin. In addition, owing to the relatively low loadings of h-ALA required in PSA patches, the costs of clinical PDT may potentially be reduced.

Keywords
5-Aminolaevulinic acid; Prodrugs; Topical; Esters; Patches; Drug delivery
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Novel patch-based systems for the localised delivery of ALA-esters
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Publisher
Database: Elsevier - ScienceDirect
Journal: Journal of Photochemistry and Photobiology B: Biology - Volume 101, Issue 1, 5 October 2010, Pages 59–69
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Bioengineering
Get Full-Text Now
Don't Miss Today's Special Offer
Price was $35.95
You save - $31
Price after discount Only $4.95
100% Money Back Guarantee
Full-text PDF Download
Online Support
Any Questions? feel free to contact us