DESIGN OF PORPHYRIN-BASED PHOTOSENSITIZERS FOR PHOTODYNAMIC THERAPY

Porphyrin and metalloporphyrin derivatives are at the forefront of the photosensitizers currently investigated for the photodynamic therapy (PDT) of cancer. Earlier examples included various porphyrins and chlorins, some of them already approved for clinical work, but lately emphasis has been given to the development of stable bacteriochlorin derivatives. The spectroscopy, photochemistry, and electrochemistry of porphyrins and bacteriochlorins, and some of their representative metal complexes, are reviewed and related to the design of photosensitizers capable of producing reactive oxygen species with high quantum yields. Efficacy in vitro is evaluated in terms of a phototherapeutic index, and efficacy in vitro is assessed using tumor growth delays. Guidelines are proposed for the design of more efficient PDT photosensitizers.