New iron(III) anti-cancer aminobisphenolate/phenanthroline complexes: Enhancing their therapeutic potential using...

Malignant melanoma is an aggressive and deadly form of skin cancer and novel and improved therapeutic options are needed. A promising strategy involves the use of metallodrugs combined with liposomes for targeted delivery to cancer cells. In this work, a family of iron(III) complexes was synthesized bearing a trianionic aminobisphenolate ligand (L) and phenanthroline-type co-ligands (NN). Four ternary iron complexes of general formula [Fe(L)(NN)] were obtained: [Fe(L)(amphen)] (1), [Fe(L)(phen)] (2), [Fe(L)(Clphen)] (3), and [Fe(L)(Mephen)] (4), as well as a fifth complex [Fe(L)(NEt₃)(H₂O)] (5) without the bidentate co-ligand. All complexes were characterized by analytic and spectroscopic techniques and demonstrated to be stable in aqueous environment. Complexes 1 and 2 were able to bind DNA and presented high cytotoxic activity towards human cancer cells. Complex 1 (IronC) was selected for incorporation into different liposomal formulations, which were fully characterized and screened against murine melanoma cells. The IronC liposomal formulation with the highest incorporation efficiency (∼95%) and a low IC₅₀ value (7.1 ± 0.7 μM) was selected for in vivo evaluation. In a syngeneic murine melanoma model the liposomal formulation of IronC yielded the highest impairment on tumour progression when compared with the control, temozolomide, and with the iron complex in free form.