Photodynamic therapy (PDT) is characterized by a set of physical, chemical and biological processes that occurs after administration of photosensitizing compounds which become trapped exclusively in tumor tissue followed by irradiation with visible light. Shortly thereafter occurring mechanisms of energy transfer between the photosensitizer and molecular oxygen present in tissues generating reactive oxygen species capable of carrying the tumor tissue death. It can be said that the clinical application of photosensitizers in PDT therapy is a result of specific and controlled action, between photosensitizer, which acts as an optical finder and selective destructive purpose of tumor cells, as the light used for excitation its. PDT with 5-aminolevulinic acid (ALA) and its derivatives (methyl-ALA), as precursors to the formation of Protoporphyrin IX, see been used for the treatment and diagnosis of various types of skin cancers and that each occupying a space increasingly. However topical application of ALA and Methyl-ALA has several advantages of a localized application and not systemic, but also presents some limitations to drug penetration into the skin, limiting therefore the effectiveness of PDT. With this work we will investigate the possibilities of scientific and clinical applications of a conceptual shift that should make the PDT using topical application, applied much more efficient and overcoming thus the limiting of this technique related to ALA penetration at skin.
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