Near-infrared AIE-active phosphorescent iridium(III) complex for mitochondria-targeted photodynamic therapy.

Mitochondria-targeted photodynamic therapy (PDT) has recently been recognized as a promising strategy for effective cancer treatment. In this work, a mitochondria-targeted near-infrared (NIR) aggregation-induced emission (AIE)-active phosphorescent Ir(III) complex (Ir1) is reported with highly favourable mitochondria-targeted bioimaging and cancer PDT properties. Complex Ir1 has strong absorption in the visible light region (∼500 nm) and can effectively produce singlet oxygen (O) under green light (525 nm) irradiation. It preferentially accumulates in the mitochondria of human breast cancer MDA-MB-231 cells as revealed by colocalization analysis. Complex Ir1 displays high phototoxicity toward human breast cancer MDA-MB-231 cells and mouse breast cancer 4T1 cells. Complex Ir1 induces reactive oxygen species (ROS) production, mitochondrial dysfunction, and endoplasmic reticulum (ER) stress in MDA-MB-231 cells upon photoirradiation, leading to apoptotic cell death. The favorable PDT performance of Ir1 has been further demonstrated in tumour-bearing mice. Together, the results suggest that Ir1 is a promising photosensitizer for mitochondria-targeted imaging and cancer phototherapy.