A Ruthenium(II) Complex With a Two-Armed Benzimidazole Ligand as the G-Quadruplex Luminescent Probe

The selective detection of G-quadruplex DNA has the potential to reveal its biological function and provide important information for cancer diagnosis and treatment. Herein, a ruthenium(II) complex containing a two-armed benzimidazole ligand (bimbpy) (RC1) has been developed as a selective luminescence probe toward G4 DNA. RC1 exhibited distinguishable luminescence response to G4 DNA, such as HTDNA, c-MYC, and 22AG. Especially, in the presence of HTDNA, the luminescence intensity of RC1 increased to 6.1-fold. The limit of detection is 30 nM for HTDNA. However, it showed a small change in luminescence intensity against doubled-strand and single-strand DNA. The DNA binding experimental results indicated that RC1 effectively stabilized G4 DNA through hydrogen bonds and π-π stacking. The selectivity of RC1 to G4 DNA might be due to the increase in the rigidity of the two-armed benzimidazole ligand after binding to G4 DNA. Therefore, the design of ruthenium(II) complexes with a two-armed ligand will be an effective method to obtain Ru(II)-based G-quadruplex luminescent probes by adjusting the degree of rigidity of the two arms.