Photochemotherapy of Infrared Active BODIPY-Appended Iron(III) Catecholates for in Vivo Tumor Growth Inhibition

Abstract

Iron(III) catecholates of BODIPY (boron-dipyrromethene)-conjugated dipicolylamine ligands, viz. [Fe(L1)(cat)Cl] (1) and [Fe(L2)(cat)Cl] (2) (H2cat = catechol), with a ligand-to-metal charge transfer band at ∼800 nm were studied for their in vivo activity in dark and infrared light in luciferase-expressing human breast adenocarcinoma (BT474luc) cells. Complex 2 displayed in vitro photocytotoxicity in BT474luc cells (IC50: 6 μM) in infrared light of 600-720 nm with moderate dark toxicity (IC50: 18 μM) as evidenced from the MTT and Annexin-V FITC/PI staining assays. The mitochondria-localizing complexes showed apoptotic cell death involving reactive oxygen species whose generation was evidenced from 2,7-dichlorofluorescein diacetate assay. In vivo studies showed tumor growth inhibition in mice with an optimized complex 2 dose of 5 mg per kg body weight on exposure to infrared light of 685 nm (dose of 20 mW/cm2). The in vivo results exemplify complex 2 as a unique iron-based infrared-active photochemotherapeutic agent.