Biophysical Investigation and Antitumor Potential of Heterocyclic Palladium-Based Agent: Cytotoxicity, Spectroscopic and Molecular Docking Approaches in Interaction with Human Serum Albumin

With the aim of cancer treatment, interaction between 1-hexyldithiocarbamato 1,10-phenanthrolinepalladium(II) nitrate complex ([Pd(Hex-Dtc)(Phen)]NO₃, Pd-HDP), as a potential antitumor candidate and human serum albumin (HSA), was investigated at four temperatures under physiological conditions. The cell viability of Pd-HDP on normal cell lines, HFFF2 and cancer cell lines, HeLa, and G-292 were also tested. Changes in fluorescence intensity, 3D-fluorescence, synchronous fluorescence, absorption, and circular dichroism spectra of HSA were due to binding with Pd-HDP. The quenching mechanism was suggested as a combination of dynamic and static. The binding constant (K × 10⁴) and the number of binding sites (n ≈ 1) were also determined. Thermodynamic parameters proved that the interaction process was spontaneous (ΔG < 0) and van der Waals interaction and hydrogen bonding were the predominant binding in HSA-Pd-HDP system (ΔH < 0 and ΔS < 0). Moreover; the binding distance between Pd-HDP and the tryptophan residue of HSA was studied according to Forster resonance energy transfer (FRET) theory. The site marker competitive results revealed that Pd-HDP bind to Sudlow’s site II of albumin. Furthermore; molecular docking results agreed with the results of thermodynamic and spectroscopic study.