The development of an iridium(III) complex functionalized G-quadruplex probe for the stability of G-quadruplex and lifetime image in cytoplasm

G-quadruplex (G4) is widely known as a non-classical secondary structure of nucleic acid. With the in-depth study of G4, it is an urgent need for a phosphorescent probe with a high G4 binding ability to evaluate the level of G4 in the cytoplasm. Thus, this study designed and synthesized Ir-PDP where an Ir(III) complex was used as a phosphorescent emitter. Meanwhile, two installed PDPs (pyridostatin derivatives) were used to improve the combination ability with G4 and reduced the cytotoxicity of the Ir(III) complex. Compared with other nucleic acid secondary structures, Ir-PDP produced a higher phosphorescence lifetime after interacting with G4. Ir-PDP was distributed in the cytoplasm of living cells, and two-photon phosphorescence lifetime imaging can detect the binding events of the probe in the cytoplasm. The addition of G4 binder PDS significantly regulated cytoplasmic phosphorescence lifetime. The project explored a new sensing pathway to observe the binding manners of probes in the cytoplasm through the phosphorescence lifetime of probes. By installing the G4 ligand PDP on the iridium complex, we synthesized a phosphorescent probe that can label G4 in the cytoplasm, and the level of G4 in the cytoplasm can be explored through the phosphorescent lifetime of the probe.