Catalytic hairpin assembly-programmed formation of clickable nucleic acids for electrochemical detection of liver cancer related short gene.

DNA amplification usually takes place in an aqueous system to facilitate a highly efficient reaction. Therefore, it is a challenge to connect the DNA amplification with popular dry chemical methods, whose signal outputs usually come from a solid-liquid interface. Here, by linking catalytic hairpin assembly (CHA) with electrochemical biosensors through clickable nucleic acids, we develop a facile method for the detection of liver cancer related short gene MXR7. On one hand, the method maintains the advantages of CHA especially its high efficiency by performing the whole process of CHA in aqueous phase. On the other hand, the method realizes electrochemical detection of MXR7 by transferring a clickable double-helix production of MXR7-triggerd CHA to a dibenzocyclooctyne-functionalized electrode quickly through copper-free click chemistry. In comparison with traditional biotin-streptavidin or hybridization-assisted conjugation, the click chemistry allows quick response in a quarter of an hour, shortening the detection time greatly. In addition, owing to the lower steric hindrance as compared with streptavidin, the signal intensity is strong, making a sensitive detection possible. The detection limit reaches 125 fM, better than previous electrochemical methods. Results also reveal that CHA in solution has much better efficiency than that on interface, allowing two orders of magnitude improvement in detection limit (125 fM vs. 50 pM) with a shorter detection time (135 min vs. 165 min). This work also provides a novel concept to connect aqueous amplification system with interfacial detection method for other bio-analysis.