Ultrasensitive COFs electrochemical sensor for detection of bacteria by tripedal DNA walker and self-assembled nanostructure scaffolds

Ultrasensitive sensor was developed by tripedal DNA walker and nanostructure scaffolds. • The sensor could directly detect bacteria, which avoided tedious DNA extraction. • DNA tetrahedron scaffolds provide several binding sites to combine with COF-Au-MB-S5. The bacterial infections pose a significant public health challenge to public health, thus rapid and sensitive methods for bacteria detection are needed. This study developed a new functionalized covalent organic framework (COF) electrochemical sensor for detection of bacteria based on tripedal DNA walker and self-assembled nanostructure scaffolds. The DNA tracks@hairpin probes were employed to increase the effective surface area of electrode. The Staphylococcus aureus ( S. aureus ) was selected as the target to verify the approach. When the target was present in the system, specific interaction between the aptamer and target caused S6 probe to be released from the aptamer, which triggered the catalytic hairpin assembly (CHA) to form a tripedal DNA walker. The hairpin DNA track was designed and modified on surface of electrode. The “legs” of tripedal DNA walker hybridized with hairpin probe and perform directional movements along predetermined tracks to open hairpin structure. The sequence-precise, uniformly sized DNA tetrahedral (Td) scaffolds were introduced and programmed self-assembly was used to form a branched tetrahedron-hybridization chain reaction (Td-HCR) DNA complex nanostructure. The Td-HCR DNA complex hybridized with the opened hairpin structure, causing the exposure of more Td-HCR DNA binding sites to hybridize with COF-Au-MB-S5 signal probes, thus generated significant current signal for bacteria detection, with a wide linear ranging from 10 to 10 8  CFU/mL. The detection limit (LOD) was 5 CFU/mL. This sensor demonstrated excellent selectivity, high stability and reproducibility, which offered an innovative path for detection of bacteria. Ultrasensitive COFs electrochemical biosensor for detection of bacteria based on tripedal DNA walker and self-assembled nanostructure scaffolds. Download: Download high-res image (120KB) Download: Download full-size image