Application of 5-Aminolevulinic Acid and Its Derivatives for Photodynamic Therapy In Vitro and In Vivo
Photodynamic therapy (PDT) with 5-aminolevulinic acid (ALA) is the most widely used form of PDT in clinical practice. Topical application of ALA leads to overproduction of the endogenous photosensitizer protoporphyrin IX (PpIX). ALA-PDT is efficient treatment of superficial skin lesions, but not for thicker lesions. The main reason for this is suboptimal penetration of ALA molecules through cellular membranes and through stratum corneum of intact skin. Different approaches (formulations, mechanical and physical penetration enhancers, ALA derivatives) are currently used to increase the penetration. The content and distribution of ALA intracellularly and in tissues is difficult to measure, but PpIX content, on a relative scale, can be easily measured by fluorimetric assays.
Key wordsPhotodynamic therapy 5-aminolevulinic acid 5-aminolevulinic acid derivatives protoporphyrin IX fluorescence spectroscopy extraction method
We appreciate financial support from the Norwegian Cancer Society (Kreftforeningen). As well P. Juzenas would like to acknowledge researcher grant received from the Research Council of Norway (Forskningsrådet). The authors also thank Vladimir Iani and Dr. Li-Wei Ma for technical assistance, reading the manuscript and giving valuable comments and suggestions.