Interaction and photo-induced cleavage studies of a copper based chemotherapeutic drug with human serum albumin: spectroscopic and molecular docking study

The interaction of new dinuclear copper(ii) complex 1; Cu(2)(glygly)(2)(ppz)(H(2)O)(4)]·2H(2)O, derived from dipeptide (glycyl glycine) and piperazine as a metallopeptide drug with human serum albumin (HSA) was examined by means of fluorescence spectroscopy which revealed that complex 1 has a strong ability to quench the intrinsic fluorescence of HSA through a static quenching procedure. The alterations of HSA secondary structure in the presence of complex 1 were confirmed by UV-visible, FT-IR, CD and 3D fluorescence spectroscopy. The binding constants (K), and binding site number (n), corresponding thermodynamic parameters ΔG, ΔH and ΔS at different temperatures were calculated. The molecular docking technique was utilized to ascertain the mechanism and mode of action towards the molecular target HSA indicating that complex 1 was located at the entrance of site I by electrostatic and hydrophobic forces, consistent with the corresponding experimental results. Complex 1 shows efficient photo-induced HSA cleavage activity, indicating the involvement of hydroxyl radicals as the reactive species. Furthermore, the cytotoxicity of 1 was examined on a panel of human tumor cell lines of different histological origins showing significant GI(50) values specifically towards MIAPACA2, A498 and A549 tumor cell lines. These results complement previous biological studies of new specific target metallopeptides, providing additional information about possibilities of their transport and disposition in blood plasma.