Synthesis and characterization of photodynamic activity of an iodinated Chlorin p6 copper complex

Abstract

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.