Two-way nanopore sensing of sequence-specific oligonucleotides and small-molecule targets in complex matrices using integrated DNA supersandwich structures.

Recent advances in molecular science and nanotechnology offer unprecedented opportunities to miniaturize chemical analysis systems into nanofluidic devices that mimic ion channels and have single-molecule sensitivity, target-specific selectivity, and reduced consumption of materials. When analytes are present in the nanofluidic sensing system, they temporarily or permanently block the pathway for ion conduction, yielding characteristic changes in background current that serves as a signature for target identification, or concentration qualification. Although the sensitivity approaches a relatively high level, this technique is still challenging for treating multi-component or complex clinic samples. In recent years, the sequence-specific and label-free detection of DNA targets associated with many crucial pathogenic diseases has attracted a broad interest. To meet the requirements of this application, these nanofluidic devices have been endowed with chemical selectivity by integration with nucleic-acid-based sensing elements. For example, simple-structured DNA components were used for oligonucleotide detection using the hybridization technique. Intermolecular DNA duplexes, forming T-Hg-T structures, have been used for nanopore-based sensing of mercury. We used DNA molecular motors, showing a conformational change in response to external stimuli, to construct adaptive DNA-nanopore switches. In conventional DNA-based nanopore sensors, a single capture DNA hybridizes to a single target strand or binds to a single molecular target (Figure 1, insert), which restricts their performance. On the