Self-assembled nanoparticles based on cationic mono-/AIE tetra-nuclear Ir(III) complexes: long wavelength absorption/near-infrared emission photosensitizers for photodynamic therapy

Cyclometalated Ir(iii) complexes as photosensitizers (PSs) have attracted widespread attention because of their good photostability and efficient O-1(2) production ability. However, their strong absorption in the UV-vis region severely limits their applications in photodynamic therapy (PDT) because the short wavelength illuminating light can be easily absorbed by the skin and subcutaneous adipose tissue causing damage to the patient's normal tissue. Herein, mono- and tetra-nuclear Ir(iii) complex-porphyrin conjugates are rationally designed and synthesized, especially [TPP-4Ir](4+) exhibits obvious aggregation-induced emission (AIE) characteristics. PSs comprising Ir(iii) complex-porphyrin conjugates self-assembled as nanoparticles (NPs) are successfully achieved. The obtained [TPP-Ir](+) NPs and [TPP-4Ir](4+) NPs exhibit long wavelength absorption (500-700 nm) and near-infrared emission (635-750 nm), successfully overcoming the inherent defects of short wavelength absorption of traditional Ir(iii) complexes. Moreover, [TPP-4Ir](4+) NPs exhibit good biocompatibility, high O-1(2) generation ability, low half-maximal inhibitory concentration (IC50) (0.47 x 10(-6) M), potent cytotoxicity toward cancer cells and superior cellular uptake under white light irradiation. This work extends the scope for transition metal complex PSs with promising clinical applications.

Automated summary

In this study, cyclometalated Ir(iii) complexes were designed and synthesized, and were successfully assembled into nanoparticles. These nanoparticles exhibit long wavelength absorption and near-infrared emission, overcoming the limitation of strong absorption in the UV-vis region. Moreover, the nanoparticles show good biocompatibility, high O-1(2) generation ability, potent cytotoxicity towards cancer cells, and superior cellular uptake. This work expands the potential applications of transition metal complex photosensitizers in clinical settings.