The Midas Touch by Iridium: A Second Near-Infrared Aggregation-Induced Emission-Active Metallo-Agent for Exceptional Phototheranostics of Breast Cancer

Developing small organic molecular phototheranostic agents with second near-infrared (NIR-II) aggregation-induced emission (AIE) is paramount for the phototriggered diagnostic imaging and synchronous in situ therapy of cancer via an excellent balance of the excited states energy dissipations. In this study, a multifunctional iridium(III) complex is exploited by the coordination of an AIE-active N^N ancillary ligand with a trivalent iridium ion. The resultant complex DPTPzIr significantly outperforms its parent ligand in terms of absorption/emission wavelengths, reactive oxygen species (ROS) production, and photothermal conversion, which simultaneously endow DPTPzIr nanoparticles with matched absorption peak to commercial 808 nm laser, the longest NIR-II emission peak (above 1100 nm) among those previously reported AIE iridium(III) complexes, potentiated type-I ROS generation, and as high as 60.5% of photothermal conversion efficiency. Consequently, DPTPzIr nanoparticles perform well in multimodal image-guided photodynamic therapy-photothermal therapy for breast cancer in tumor-bearing mice, enabling precise tumor diagnosis and complete ablation with high biocompatibility. Our present work provides a simple, feasible, and effective paradigm for the development of advanced phototheranostic agents.