Imaging nucleus viscosity and G-quadruplex DNA in living cells using a nucleus-targeting two-photon fluorescent probe

A two-photon fluorescent probe, TP-2Bz, was designed and synthesized and it exhibited good targeting capabilities toward cell nuclei. In particular, TP-2Bz demonstrated a high selectivity to both G-quadruplex DNA and viscosity inside the nucleus with significant ratiometric enhancement in fluorescence, providing a specific, versatile imaging tool for analyzing the viscosity and G-quadruplex DNA in living cells.