Photosensitizers are light-activated compounds that play a crucial role in the field of photodynamic therapy (PDT), an emerging non-invasive therapeutic modality for the treatment of various diseases, including cancer. Photodynamic therapy combines light and photosensitizers in the presence of oxygen to generate cytotoxic reactive oxygen species (ROS) and induce cellular death. In fact, PDT relies on the ability of photosensitizers to be selectively activated by light, allowing for precise spatial over treatment, and minimizing collateral damage to healthy cells and tissues.

Amongst the well-known photosensitizers (e.g. porphyrins, chlorin, xanthene, and ruthenium-based complexes), BODIPY derivatives have shown promising potential because of their highly tunable photophysical properties and versatile synthetic accessibility. Several studies have explored the optimization of the BODIPY core to improve singlet-to-triplet intersystem crossing and efficiency to generate singlet oxygen (singlet oxygen quantum yields). For example, the halogen substitution at the BODIPY core significantly impacts their photophysical properties by enhancing intersystem crossing to the triplet state, suggesting these derivatives may act as effective PDT photosensitizers.

As an extension of the work developed in our research group, we report the design and evaluation of BODIPY derivatives functionalized with an anthracene group at meso and an iodine or formyl group at 2,6-position of the core. The photophysical characterization of the derivatives and the in vitro PDT studies in cancer cells (4T1 cell line) were performed to determine their potential as PDT photosensitizers. The formylated anthracene-BODIPY derivative exhibited the highest tumor suppression under irradiation, making it a potential candidate as PDT photosensitizer.