Experimental and Computational Insights into the Apoptotic Potential of New Phenanthroline-Based Copper(II) Complexes: From Spectroscopic Characterization and In Vitro Cytotoxicity to In Silico Target Identification.

Background

Two novel copper(II) coordination complexes, PH-Cu [(1,10-phenanthroline)(malonato)copper(II)] and PC-Cu [(1,10-phenanthroline)(cyclobutane-1,1-dicarboxylato)copper(II)], were synthesized and evaluated as potential anticancer agents, aiming to characterize structural properties, explore antiproliferative activity and generate mechanistic hypotheses through experimental and computational approaches.

Methods

Complexes were characterized by EPR, FTIR-ATR, and ESI-MS, with preliminary SC-XRD data for PH-Cu. Antiproliferative activity was evaluated against six human cancer cell lines using the MTT assay (24 h). Subcellular effects were assessed by fluorescence microscopy and RT-qPCR. Computational studies included DFT geometry optimization, target prediction, molecular docking, and ADMET profiling.

Results

Based on spectroscopic and spectrometric data and comparison with analogous Cu(II) complexes, a distorted square-pyramidal coordination geometry was proposed; this assignment was not confirmed by SC-XRD. Both complexes exhibited potent antiproliferative activity, with PH-Cu showing the highest potency in HeLa cells (IC50 = 4.22 µM). Under the same conditions, cisplatin showed substantially lower activity (HepG2: 191.1 µM; Caco-2: 129.6 µM; NCI-H69: >333.3 µM; HeLa: 21.9 µM). Fluorescence microscopy at 18 h revealed pyknosis, karyorrhexis, and microtubule disorganization, consistent with regulated cell death. RT-qPCR of PH-Cu indicated intrinsic apoptotic pathway engagement (BAX +3.20-fold; BCL2 to 0.39-fold of control). DFT-optimized bond lengths were consistent with crystallographic data for analogous complexes. Molecular docking suggested PRKCG, RELA (p65), Caspase-3, and α/β-tubulin as interaction candidates, while ADMET profiling predicted favorable intestinal absorption (>92.8%) and low BBB permeability.

Conclusions

These results suggest that the [Cu(phen)] unit constitutes the primary pharmacophore, with the dicarboxylate co-ligand as a modulator of the antiproliferative profile, suggesting promising anticancer pharmacological potential.