Formation of metal complexes of tumor‐localizing porphyrins

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Abstract
Whereas the tumor localizer and photosensitizer hematoporphyrin derivative (Hpd) has its fluorescence emission maximum at 610–630 nm, several authors have reported that in aqueous solutions of hematoporphyrin (Hp) and Hpd, or in tumors after an injection of Hpd, a compound is formed which has its fluorescence emission maximum at 570–590 nm. This work (HPLC and fluorescence analysis) indicates that this peak is due to the formation of Zn‐porphyrins either in vitro or in vivo. Cu‐ and, Co‐porphyrins may be formed as well, from traces of these metallic ions. In contrast to free porphyrins and Zn‐porphyrins the latter complexes are non‐fluorescent and do not act as photosensitizers.