Elucidating CT-DNA refolding and antitumor efficacy of novel phendione-Pd(II) complexes: A comprehensive...

The newly designed complexes of [[Pd(dach)(phendione)](NO₃)₂ (1), [Pd(bpy)(phendione)](NO₃)₂ (2), and [Pd(dpa)(phendione)](NO₃)₂ (3) (where dach is 1,2-diaminocyclohexane, phendione is 1,10-phenanthroline-5,6-dione, bpy is 2,2'-bipyridine, and dpa is 2,2'-dipyridylamine) were synthesized and characterized by various techniques such as FT-IR, ¹H NMR, 2D¹H NMR, D₂O exchange, UV-Vis spectroscopy, and elemental analysis. The theoretical studies (DFT approach) supported the formation of these complexes. The cytotoxic effects of these complexes (1, 2, and 3) on two different cell types, ovarian cancer-derived CHO cells and NIH/3 T3 fibroblasts (normal cells), were investigated and compared with cisplatin. The interaction of CT-DNA with these complexes was performed using various methods. The absorption studies show that the main mode of DNA interaction with the complexes is groove. Analysis of the fluorescence results suggest that the proposed mechanism of fluorescence quenching in DNA is static quenching, and the increasing trend of K_b values of these complexes is 1 > 3 > 2. The thermodynamic parameters (ΔH°, ΔS°) display that hydrogen bonding and the van der Waals forces play a vital role in interaction of the complexes with DNA. Furthermore, molecular docking and MD simulations provided additional evidence for these results by demonstrating that (1) had stable binding in the grooves of DNA with favorable interaction energies. In addition, DFT-based descriptors confirmed that (1) has a more favorable reactivity and a better ability to bind with DNA than the others. The experimental and computational analyses support each other and suggest that the Pd(II) complexes, including (1), have potential as antitumor agents.