Aza-BODIPY photosensitizer substituted with phthalonitrile groups: Synthesis, photophysical properties and in vitro tests for breast cancer

In photodynamic therapy (PDT), reactive oxygen species (ROS) are generated through dynamic interactions between light of a specific wavelength, a photosensitizer (PS) and molecular oxygen. Nowadays, there has been an increment in the number of studies evaluating the possible utilization of BF₂ chelated tetraarylazadipyrromethanes (aza-BODIPYs) as photosensitizers in PDT. In this study, a novel aza-BODIPY with phthalonitrile substituents was synthesized by the esterification reaction of a phthalonitrile derivative namely, 4-((3,4-dicyanophenyl)sulphanyl)benzoic acid with an aza-BODIPY bearing hydroxy groups on the para positions of distal phenyl groups. Aza-BODIPY compound bearing phthalonitrile substituents was characterized by using UV–Vis, fluorescence, ¹H-NMR and mass spectroscopy techniques. Photophysical and photochemical properties including fluorescence quantum yield and singlet oxygen yield were determined. In order to explore its photodynamic efficacy, it was tested on a breast cancer cell line (MCF-7 cells) and on a normal healthy cell line (L929 cells) through dark and light cytotoxicity.