A reusable electrochemical sensor for one-step biosensing in complex media using triplex-forming oligonucleotide coupled DNA nanostructure

Highlights: • An electrochemical biosensor is developed for detection of different analytes such as DNA, protein and metal ion. • A switchable interfacial probe based on a triplex-forming oligonucleotide coupled DNA nanostructure is designed. • The sensor allows one-step detection without requiring complex operation and expensive reagents. • Sensitive detection of DNA in serum (1 pM), carcino-embryonic antigen in blood (2 pM) and Pb²⁺ in lake water (1 nM). -- Abstract: Here we report an electrochemical DNA (E-DNA) sensor to detect a variety of analytes by using a novel interfacial probe that rationally integrates triplex-forming oligonucleotide (TFO) into a tetrahedral DNA nanostructure (TDN). In the presence of analyte, the blocked TFO is released and subsequently binds the edge of TDN to form a triplex DNA structure, which confines the redox reporter to be in close proximity to the underlying electrode and enhances the electrochemical signal. Thanks to the unique design and property of the probe, the proposed sensor could efficiently suppress the background signal (from 0.69 μA to 0.092 μA) and thus enhance the signal-to-noise ratio, resulting in improved sensing performance. Furthermore, the sensor displays new merits such as rapid response (∼35 min), one-step operation, easy regeneration (buffer change) and good generality (changing recognition element) compared with traditional TDN-based E-DNA sensor using enzyme displays signal transducer. In addition, to demonstrate real-world applicability of this new sensor, we have successfully detected different analytes (e.g., DNA, protein, and metal ion) in the complex media (e.g., serum, blood, and lake water), implying its considerable potential for precise bioanalysis in the future.