Target-induced catalytic hairpin assembly formation of functional Y-junction DNA structures for label-free and sensitive electrochemical detection of human serum proteins

The construction of simple and highly sensitive aptasensors will significantly advance the monitoring of proteins. In this work, we have developed a convenient and label-free protein-induced catalytic hairpin assembly signal amplification approach for aptamer-based sensitive electrochemical detection of thrombin in human serums. The target thrombin binds the aptamer-containing hairpin probes immobilized on the sensor electrodes and triggers catalytic assembly of other two hairpins to form many G-quadruplex Y-junction DNA structures in situ . These G-quadruplex structures further associate with hemin to form G-quadruplex/hemin complexes, which are then subject to electrochemical measurement and generate substantially amplified current output for label-free and sensitive detection of thrombin. The developed aptasensor shows a dynamic range of 0.01–1.0   nM and a detection limit of 6.0   p.m for thrombin detection. The sensor can also discriminate the target thrombin against other non-target proteins and exhibits promising results for detecting thrombin in human serums. With the successful construction of the thrombin aptasensor, our signal amplified method can be potentially applied to detect other target molecules by choosing appropriate aptamer/ligand pairs.