A highly emissive near infrared thiophene-benzoindolium ligand binding to mitochondrial G-quadruplexes triggers triple-negative breast cancer cell death

Abstract

Small-molecule fluorescent ligands targeting mitochondrial G-quadruplexes (mtG4s) are considered as a promising direction in tumor therapy, especially those with dual roles of both detecting the mtG4 structures and interfering with the mtG4 functions. Herein, based on our previous studies, two novel thiophene-benzoindolium ligands (YS-1 and YS-2) were designed and synthesized. One of them, YS-2, may be a potential NIR fluorescent probe, with an absorption band centered at 595 nm and an emission band centered at 685 nm, as well as a good quantum yield upon binding G4s. YS-2 was further proved to selectively bind to mtG4s in MDA-MB-231 cells, and then induce mitochondrial dysfunction, showing suppressive effects on the proliferation of tumor cells in both 2D and 3D cell models. To sum up, a novel highly emissive NIR ligand binding to mtG4s was successfully discovered, giving insights into the future development of novel G4 fluorescent ligands targeting mtG4s with therapeutic possibilities against tumors.