Synthesis and characterization of photodynamic activity of an iodinated Chlorin p6 copper complex†
We report the synthesis of a new iodinated Chlorin p6 copper complex (ICp6–Cu) and its efficacy for photodynamic treatment (PDT) of cancer cells. The metal complex is obtained by reacting Chlorin p6 (Cp6) with copper iodide (CuI). The complex formation results in a shift in the Q absorption band of Cp6 from 663 nm to 634 nm and X-ray fluorescence of the complex showed the presence of both copper and iodine. FTIR and EPR spectroscopy suggests that the copper is attached to Cp6 at the two adjacent carboxylic groups. Studies on the photochemical generation of singlet oxygen (1O2) and other reactive oxygen species (ROS) using fluorescence probes revealed that ICp6–Cu acts predominantly through the type I process. PDT of oral cancer cells with ICp6–Cu (10 μM, 3 h) and red light (630 ± 20 nm, ∼12 J cm−2) led to ∼90% phototoxicity. Furthermore, in contrast to Cp6, the phototoxicity induced by ICp6–Cu is not significantly affected under hypoxic conditions.