A highly sensitive electrochemical aptasensor for Sonic Hedgehog biomarker based on primer exchange reaction and catalytic hairpin assembly amplifications

Sonic Hedgehog (SHh) protein is commonly over-expressed in various cancers and correlates closely to tumor generation, metastasis and drug resistance, and the detection of SHh has significances for diagnosing various cancers. In this work, by using a new SHh-specific aptamer and combining primer exchange reaction (PER) and catalytic hairpin assembly (CHA), we establish an amplified electrochemical biosensor for sensitive assay of SHh. The combination of SHh and its aptamer results in the release of a strand that can hybridize with the dumbbell-shaped hairpin to trigger PER for generation of lots of new ssDNAs. These strands further initiate CHA cycles to promote confinement of plenty methylene blue (MB)-labeled sequences on the sensor surface. Largely magnified electrochemical current signals from the surface-attached MB labels then enable amplified assay of SHh with a detection limit of 4.1 pM, due to the two-step cyclic amplifications of PER and CHA. Our developed biosensor can also be utilized to assay low concentrations of SHh that is spiked into human serum diluent, verifying its potential for sensitively detecting various molecular markers by replacing the corresponding aptamers for disease diagnosis and prognosis evaluation.