A label-free method for identifying electroactive G-quadruplex-binding ligand

Ligands of G-quadruplex have received great attention because of their potential anticancer activity. Here, we designed a label-free electrochemical method to identify electrochemically active molecules that stabilize G-quadruplexes in homogeneous medium. Daunorubicin (DNR) was used as model drug. In the presence of GDNA, the voltammetry of DNR changed. The binding constant (β) and binding-site number (m) of GDNA – mDNR are simultaneously obtained from dependence of the current on the amount of added GDNA in voltammetry, concluding that β = (2.37 ± 2.25) × 10⁷ M^? 1and m was near 1, respectively. Control experiment was performed, indicating that this method can specific identify G-quadruplex-binding ligand. The interaction mechanism of DNR with GDNA was also investigated by circular dichroism (CD). The result demonstrated that it is a simple and selective method for identification electroactive ligand with potential anticancer activity.