A novel DNAzyme-driven walker-walkers serial amplified electrochemical aptasensor for ultrasensitive detection of cardiac troponin I

Sensitive and accurate detection of Cardiac troponin I (cTnI) plays an instrumental role in the prevention and management of acute myocardial infarction. Herein, a novel electrochemical aptasensor was designed for cTnI ultrasensitive detection based on DNAzyme-driven walker-walkers serial amplified strategy. The Au/NiCo2S4 nanocomposites, which possess excellent conductivity and a high specific surface area, were used to assemble on the modified electrode for the first time. The Hairpin probe I (HPI) and hairpin probe II (HP II) were selfassembled onto an Au/NiCo2S4 electrode surface through the interaction of Au-S bond. In the present of cTnI, the walker-walkers strategy was activated. After the hybridization between cTnI and HP I, the DNA walker shears the specific sequence of HP II and releases triggered DNA. Since the triggered DNA corresponds to the HP I complementary sequence, which could trigger multiple recycling and release DNA walkers. By the joint action of cTnI and triggered DNA, HP I was opened and released more DNA walkers. With the use of cDNA, capturing methylene blue (MB), resulting in the significant electrochemical signal in differential pulse voltammetry (DPV). The proposed strategy can effectively avoid problems of the insufficient distance or limited available driving force that general exist in unipedal DNA walkers. Under optimal conditions, the change of current was linearly related to the negative logarithm of cTnI concentration in the detection range of 0.01-60 ng/mL with a low detection limit of 0.26 pg/mL. Moreover, the proposed aptasensor was successfully applied in detection of human serum samples.