Studies of the potential of 5-aminolevulinic acid in photodynamic therapy of skin cancer: obtaining and evaluating liposomes with release system

Abstract

5-aminolevulinic acid (S-ALA) have been studied in topical formulations as prodrug in association with Photodynamic therapy in the treatment of skin cancer. (KENNEDY, J.C. and POTTIER, R.H. 1992; WARLOE, T. et al.,1992; SVANBERG, K. et al., 1992). After your apply, the incidence of visible wavelenght light induces to formation of a active fluorescent and photodynamic substance, the Protoporfirin IX (PpIX). The use of ALA as a preliminary biosintese of PPIX, and their use in Photodynamic therapy, has been limited to the skin cancer. 5-ALA applied topically may be easily penetrates the abnormal stratum corneum, but not across the normal epiderm, permiting, thus, the high selective photosensibility from skin cancer. The purpose of the drug delivery systems which provides a penetration enhance and, consequently, the cancer tissue concentration of ALA, presents the way of cancer therapy improvement since the photosensibilization depends on their concentration in the target tissue. The use of liposomes as drug delivery systems to deliver drug across the skin have beenp roposed by several authors (FOLDVARI, M. 1991; BONINA, F.P. et al., 1995; VEMURI, S. and RHODE, C.T. 1995). The structural characteristics of these systems, already been knowledge, as well as your capacity to capture substances of different solubilities. Because their similarity with biological membrane, may be facilited the penetration of the encapsulated drug across the biological tissue. The aim of this work will be to obtain a drug delivery system to deliver 5-ALA into the skin in association with Photodynamic therapy, which constitutes a scientific innovation. The study of delivery systems able to provide an increase of penetration and concentration of 5-ALA in skin tissue will be improve the therapeutic effect in the treatment of sldn cancer by means of topic ALA-PDT. The significance of this study is the necessity of a practical, selective and modern treatment, which may be optimize by administration of prodrug 5-ALA in adequate delivery system, because the epidermal barrier of skin cancer tissue still constitutes a limitation for topical ALA-PDT. (BONINA, F.P., et al., 1995). Effects of phospholipid based formulation on in vitro and in vivo percutaneous absorption of methyl nicotinate... (AU)