Palladium‐Imidazole Nanoparticles' Cytotoxic Effects on Colon Cancer Cells: Induction of Cell Cycle Arrest and Apoptosis Mediated via Mitochondria

ABSTRACT The present study emphasized the potential antitumor activity of compound A; [Pd (Im) 2 Cl 2 ], a nano‐sized coordination compound with a size of 23.76 nm. Characterization was performed using elemental analysis, molar conductance, magnetic measurement, FTIR, Ultraviolet–visible (UV–vis) spectroscopy, thermal analysis, mass spectrometry, and NMR. The complex showed stability up to 300°C. Furthermore, the compound's formation spontaneity was supported by activation parameters calculated from TGA. The di‐aqua form of the separated solid complex, compound B [Pd (Im) 2 (H 2 O) 2 ] 2+ , was successfully prepared. The geometry optimization of imidazole and its complexes showed that both complexes were more stable than free imidazole. The cis di‐aqua form of [Pd (Im) 2 (H 2 O) 2 ] 2+ exhibits superior stability with a more potent IC 50 value of 5.72±0.68 μg/mL. This form demonstrates greater inhibitory impacts on Caco‐2 cancer cell proliferation compared to [Pd (Im) 2 Cl 2 ]. Moreover, the cytoxicity of [Pd (Im) 2 (H 2 O) 2 ] 2+ against Caco‐2 cells was confirmed by a significant increase in LDH levels in treated Caco‐2 cells compared to untreated ones. Treatment with [Pd (Im) 2 (H 2 O) 2 ] 2+ in Caco‐2 cells markedly raised the percentage of early and late apoptotic cells, accompanied by Go/G1 phase arrest with a more intense comet nucleus. Apoptosis induction in [Pd (Im) 2 (H 2 O) 2 ] 2+ treated cells was mediated through increased reactive oxygen species (ROS) production. Moreover, [Pd (Im) 2 (H 2 O) 2 ] 2+ markedly raised the expression levels of cleaved Caspase‐3, Bax, and P53 in treated Caco‐2 cells, while concurrently dropping the levels of Bcl‐2, cyclin D1, and CDK4. Overall, these findings indicate that [Pd (Im) 2 (H 2 O) 2 ] 2+ triggers significant cytotoxicity in Caco‐2 cancer cells in a dose‐dependent manner, primarily via ROS‐mediated cell death, possibly via the mitochondrial pathway. Additionally, the active species in selected proteins related to apoptosis and cell cycle arrest were explored and compared with theoretical molecular docking results. The outcomes also validated the safety of using [Pd (Im) 2 (H 2 O) 2 ] 2+ against healthy cells, suggesting it as a promising treatment option for colon cancer in humans.