Engineering Ru(ii) Schiff base complexes as biofunctional materials: cytotoxic and cell imaging perspectives

Abstract

Four bromine-substituted Ru(II)-arene Schiff base complexes derived from bromo-picolinaldehyde and 3-(1H-pyrazol-1-yl)propan-1-amine were examined for their cytotoxic behaviour toward cervical cancer (SiHa) and normal fibroblast (3T3-L1) cells using MTT-based in vitro assays. The ligands and complexes were comprehensively characterized by FTIR; ¹H, ¹³C, and ¹⁹F NMR; and ESI-LCMS analyses. Single-crystal X-ray diffraction (SCXRD) confirmed the molecular structure of complex 3, while PXRD validated the crystalline nature of complexes 2 and 4. Density functional theory (DFT) calculations further supported the experimental data by revealing optimized geometries and key electronic descriptors. All complexes exhibited time- and dose-dependent anticancer effects, with complexes 2–4 showing the greatest cytotoxicity toward the SiHa cells (viability at 72 h: 20% ± 3%, 31% ± 3%, and 29% ± 3%, respectively) while maintaining high viability in normal fibroblasts (>90%). The IC₅₀ values for complexes 1–4 were 19.54 ± 2, 14.21 ± 4, 12.43 ± 4, and 12.43 ± 4 µM, respectively. Acridine orange (AO) and ethidium bromide (EtBr) staining and morphological analyses confirmed apoptosis as the primary mechanism of cell death, as evidenced by reduced adhesion, membrane blebbing, and cell rounding. The pronounced and selective cytotoxicity of these bromine-substituted Ru(II) complexes highlights their potential as promising biomaterial candidates for targeted anticancer therapy.