It is not just about size: The influence of length and terminal groups of polyether chains on the photocytotoxicity of protoporphyrin IX.

Protoporphyrin IX is a natural photosensitizer used in photodynamic therapy. In this work, we present the synthesis, physicochemical characterisation, and photophysical studies of pegylated derivatives of protoporphyrin IX, two of which exhibit nanomolar activity against the A2780 and SK-Mel-28 cell lines. The most active compound exhibits IC50 values of 15.7 ± 3.4 nM for A2780 and 25.1 ± 14.3 nM for SK-Mel-28 following exposure to a light fluence of 5 J/cm2. The length of the PEG chain and the chemical group at its end both affected the observed biological activity. It was noted that the ethyl-ended polyethylene glycol chain of protoporphyrin IX influenced activity significantly less in comparison to the methyl-ended chain in the same study.