1.1 Porphyrins - Friedrich-Alexander-Universität Erlangen-Nürnberg

1 Introduction
1.2 Photodynamic Therapy (PDT)
1.2.1 The History of PDT
The term photodynamic therapy refers to the treatment of diseases by the use of light and
photoactive pigments. That concept is not a new-fashioned contrivance as first hints to it can
be found up to 4000 B.C. in the ancient cultures of Egypt, India and China. According to
contemporary documents like e.g. the EBERS papyrus or the Atharva Veda, then, skin
diseases, described as depigmented lesions fitting with clinical pictures of vitiligo or leprosy,
were treated by application of pastes made of plants or seeds and the successive exposure
to bright sunlight. 50 Today we know that these pastes contained psoralenes
(furanocoumarins) which represent anaerobic photosensitizers being still used in terms of
e.g. the PUVA-treatment of psoriasis or other photochemotherapies. 51
But this knowledge is quite new as it took until the end of the 19 th century when the student
O. RAAB experimentally proved that irradiation with light in combination with fluorescing
substrates like acridine dyes caused death of paramecia. 52 Based on those findings RAAB’s
supervisor H. TAPPEINER and his colleague H. JESIONEK established the term “photodynamic
action” and conducted first experiments in the photodynamic treatment of patients with
skin carcinoma in 1905 using e.g. eosin as sensitizer. 53
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Figure 7. Documentation of the first PDT
sessions on a 64 year-old patient with
rodent ulcer before treatment (left) and
one month after PDT with topical
application of Magdala-red followed by
exposure to sunlight (right).
Around that time, tetrapyrroles entered the scene when H. W. HAUSMANN (1908) and F.
MEYER-BETZ (1912) studied the effects of light exposure in combination with
hematoporphyrin (Hp 20, see Scheme 12). In unorthodox experiments with white mice,
HAUSMANN was able to prove that Hp is an effective sensitizer and that the effect is
dependent on the light dose. 54 More exceptionally, MEYER-BETZ experimented on himself and