Near-infrared fluorescent probe for sensitive detection and imaging of DNA G4s in living cells.

G-quadruplexs (G4s), four-stranded nucleic acid secondary structures, which formed by guanine-rich sequences play a vital role in human biological systems. Studies have shown that the formation of G4s is closely related to tumor development and apoptosis, which is considered as a new target for the development of anti-tumor drugs. Therefore, it is important to develop novel probes for G4s imaging. In this article, we engineered a near-infrared fluorescent probe (TOH) which can be activated by DNA G4s in living cells and tumor. TOH exhibits high selectivity to the structure of DNA G4s with the limit of detection for DNA G4s (Mito-0.5-2) is calculated to be 0.43 nM. Imaging studies of different cell lines revealed that the brighter fluorescence in cancer cell lines than in normal, indicating that DNA G4s maybe highly express in tumor cell lines. Simultaneously, TOH is also introduced into live tumor tissue imaging and found that the fluorescence intensity of tumor is the brightest relative to normal tissue, further validating the high expression of DNA G4s structures in tumor tissue. These features demonstrate TOH not only have the ability to image DNA G4 structures in real time, but also may have tumor diagnostic capabilities.