Embedding oxygen heterocycles into BODIPY to enhance intersystem crossing for photodynamic therapy†

By incorporating an oxygen heterocycle into a BODIPY core, near-infrared (NIR) absorbing dyes were successfully prepared. The solid-state structures of these systems were confirmed through X-ray crystallographic analysis. The extended BODIPY compounds exhibited absorption and emission wavelengths in the NIR region (up to λ_abs = 772 nm and λ_em = 807 nm in DMSO). Notably, the inclusion of the oxygen heterocycle enhanced intersystem crossing, enabling the newly-formed BODIPY to act as a heavy-atom-free singlet oxygen generator. Upon light-irradiation, self-assembled BODIPY nanoparticles caused mitochondrial damage by reducing the mitochondrial membrane potential, thereby promoting tumor cell apoptosis in vivo. Furthermore, these self-assembled nanoparticles demonstrated a significant inhibitory effect on animal tumor tissues when irradiated with an 808 nm laser.