New Water-Soluble N-Heterocyclic Carbene-Palladium Complexes as Promising Anti-Tumor Agents: Investigating DNA and Protein Interactions

This investigation focuses on the synthesis and characterization of three new, water-soluble palladium complexes, with potential to overcome the drawbacks of platinum-based anti-cancer drugs. The complexes contain small N-heterocyclic carbene (NHC) ligands, having groups that impart water solubility. The anti-cancer effects of these complexes were evaluated in two different cancer cell lines, namely,HeLa, a cervical cancer cell line and A549,adenocarcinoma human alveolar basal epithelial cell line. Cytotoxicity of the complexes was compared with cisplatin, an established platinum-based anti-cancer moiety, using the MTT assay (MTT is 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide). Aqueous solutions of the synthesized complexes demonstrated significant cytotoxicity in both the cell lines. The synthesized metal complexes resulted in a stronger, cytotoxic effect in A549 cells (lung cancer cells), as compared to cisplatin. Furthermore, interaction of these palladium compounds with DNA was studied using gel electrophoresis and spectrometry methods. The result suggested that the complexes interacted with DNA via intercalation. Interaction with BSA (Bovine Serum Albumin) was investigated using UV-Vis spectroscopy suggesting positive interaction of palladium complex with BSA proteins. Furthermore, fluorescence studies revealed quenching of protein fluorescence thus, indicating dynamic quenching mechanism with the number of association sites being calculated as similar to 1.