Synthesis of a Light-Up Probe with a Trioxazole Skeleton for Tracking G-Quadruplex Dynamic Behavior

G-Quadruplexes (G4) are noncanonical nucleic acid structures that play crucial roles in various biological processes. However, tracking the dynamic folding and unfolding processes of G4 in living cells remains challenging. Here, we synthesized a series of candidate fluorescent probes by introducing vinyl naphthyl (VN) group(s) into a trioxazole skeleton, aiming to develop a suitable light-up probe for tracking the dynamics of G4 formation in living cells. Among them, TO-2,3VN (2f), which features two VN groups, exhibited a selective interaction with G4. It nevertheless has low stabilizing ability, which is important to avoid interference with physiological G4 folding processes. It showed remarkable light-up properties and could successfully visualize the folding and unfolding processes of G4 in vitro. Furthermore, TO-2,3VN (2f) specifically interacted with RNA G4 in living cells, showing significant fluorescence intensity changes that corresponded to the dynamic processes of RNA G4 folding and unfolding in HeLa cells exposed to starvation stress. These findings highlight the potential of 2f as a tool for real-time visualization of G4 dynamics in living cells to investigate the biological functions of G4s.