A one-step and label-free, electrochemical DNA detection using metal ion-mediated molecular beacon probe

Abstract We developed a one-step and label-free, electrochemical DNA detection method using metal ion-mediated molecular beacon (MB) probe specially designed to have target-specific sequence in its loop and Pb 2+ -binding aptamer in its stem. In the absence of target DNA, MB probe, after the interaction with Pb 2+ , forms the intramolecular stem-loop hairpin structure, which limits Pb 2+ to freely diffuse onto the electrode surface, leading to the low electrochemical signal. In contrast, the presence of target DNA that forms the hybridization complex with MB probe, breaks down the intramolecular stem-loop structure of MB probe, and releases Pb 2+ that is freely diffused onto the electrode surface to generate the high electrochemical signal. By employing this method, the target DNA from Chlamydia trachomatis , one of the major pathogens causing sexually transmitted disease was successfully detected with the high selectivity.