A pyrene-derived fluorescence probe based on π-π stacking and excimer formation for DNA detection and intracellular visualization.

A novel fluorescent probe L for DNA detection was designed by linking a pyrene fluorophore to a naphthalimide-imidazole unit via a benzene spacer. The probe operates through a π-π stacking-driven intercalation and excimer formation mechanism, offering an immediate "turn-off" fluorescence response with high selectivity and a detection limit of 4.41 nM under physiologically relevant pH conditions. In cellular environments, Ca2+ enables probe release from DNA, restoring cytoplasmic fluorescence and thereby allowing indirect visualization of nuclear DNA via enhanced cytoplasmic signals. This strategy demonstrates the potential of probe L for effective bioimaging in living cells.