A dual fragment triggered DNA ladder nanostructure based on logic gate and dispersion-to-localization catalytic hairpin assembly for efficient fluorescence assay of SARS-CoV-2 and H1N1.

DNA nanotechnology has been widely utilized in the construction of various functional nanostructures. However, most DNA nanostructures have the shortcomings of low response rate and serious background leakage. Herein, we proposed the conception of AND logic gate cascaded dispersion-to-localization catalytic hairpin assembly (AND gate-DLCHA) for the fabrication of novel DNA ladder nanostructures. In our design, the entropy-driven AND logic gate can precisely recognize two fragments of the target nucleic acid sequences. After AND logic gate activation by target nucleic acids, dispersion-to-localization catalytic hairpin assembly was initiated. Consequently, tremendous DNA ladder nanostructures were generated and the response signal was rapidly enhanced, which can be used for rapid and amplied detection of nucleic acids. Taking advantage of the sensitivity and specificity of AND gate-DLCHA strategy, the fluorescence sensors were established and successfully applied in ultrasensitive assay of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and influenza A virus (H1N1) within 45 min with the limit of detection (LOD) as low as 66 copies mL-1 (SARS-CoV-2) and 33 copies mL-1 (H1N1), which showed perspectives in pathogen identification and biomedical application. The high selectivity and reliability of established sensors was attributed to the dual-fragment analysis. Meanwhile, the sensors possessed minimal leakage and greatly enhanced signal to background (S/B) ratio owing to substrate transduction from dispersion into colocalization. This rationally developed logic gate cascaded dispersion-to-localization catalytic hairpin assembly strategy presented a new approach for the development of DNA nanostructures.