DESIGN OF PORPHYRIN-BASED
PHOTOSENSITIZERS FOR
PHOTODYNAMIC THERAPY
LUIS G. ARNAUT^1
Chemistry Department, University of Coimbra, Coimbra, PortugalI. Introduction 188
II. Molecular and Electronic Structure 190
III. Electronic Transitions 198
A. Absorption and Emission 198
B. Radiationless Transitions 203
C. Triplet State 208
IV. Photoinduced Reactions with Molecular Oxygen 212
V. Photodynamic Therapy 221
VI. Conclusions 228
Acknowledgments 229
References 229
ABSTRACTPorphyrin 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 sta-
ble 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 oxy-
gen species with high quantum yields. Efficacyin vitrois 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.
(^1) Also affiliated with Luzitin SA, R. Bayer, 3045-016 Coimbra, Portugal.
187
INORGANIC PHOTOCHEMISTRY #2011 Elsevier Inc.
VOLUME 63 ISSN 0898-8838 / DOI: 10.1016/B978-0-12-385904-4.00006-8 All rights reserved