Bis-conjugation of Bioactive Molecules to Cisplatin-like Complexes through (2,2'-Bipyridine)-4,4'-Dicarboxylic Acid with Optimal Cytotoxicity Profile Provided by the Combination Ethacrynic Acid/Flurbiprofen

Abstract

A facile route to Pt^II complexes doubly functionalized with bioactive molecules through a bipyridine-type ligand is described. Initially, ligands L^EE (containing two ethacrynic acid units), L^EF (ethacrynic acid+flurbiprofen) and L^EB (ethacrynic acid+biotin) were obtained in moderate to good yields from 2,2'-bipyridine-4,4'-dicarboxylic acid. Subsequent reaction of the ligands with [PtCl₂ (DMSO)₂ ] afforded complexes [PtCl₂ (L^EE )] (2), [PtCl₂ (L^EF )] (3) and [PtCl₂ (L^EB )] (4) in high yields. All compounds were fully characterized by analytical and spectroscopic methods. Complexes 2-4 are highly stable in water/DMSO solution at 37 °C after 72 h, whereas progressive release of the bioactive fragments was detected in a cell culture medium. The compounds were assessed for their in vitro antiproliferative activity towards tumorigenic A2780, A2780cisR and Y79 cells and non-tumourigenic HEK293 cells. In particular, the combination of ethacrynic acid and flurbiprofen in 3 overcomes cisplatin-based resistance and provides strong cancer cell selectivity. Enzyme inhibition assays on human GST P1 and human COX-2 and cross-experiments with complex 1, analogous to 2-4 but lacking bio-groups, revealed a clear synergy between the Pt^II frame and the bioactive organic components.

Keywords: anticancer agents; bioinorganic chemistry; cytotoxicity; ligand design; platinum.