A robust electrochemical biosensor with cascade cleavage amplification mediated Pt@CeO2 nanoprobe machine for ultrasensitive microRNA-21 assay

Herein, a biosensing system was designed based on tripedal DNAzyme walker integrated nanoprobe signal amplification strategy for realizing ultrasensitive determination of the microRNA-21. In this work, the two-dimensional MoSe 2 /MXene nanocomposite with high electronic conductivity was synthesized as electrode signal amplification materials to immobilize more capture DNA and accelerate electron transport. After adding microRNA-21, the tripedal DNAzyme walker was activated on the surface of the Pt@CeO 2 nanoclusters, which were as nanozyme to construct the high-performance nanoprobe machine. Then, the tripedal DNAzyme strands could cleave the substrate strands and walk onto the nanoprobe for amplifying the signal remarkably. Furthermore, the detectability of the electrochemical biosensor was verified by DPV, acquiring a wide linear response in a range of 0.1 fM to 1 nM, as well as the limit of detection was 0.04 fM. Hence, such double signal amplified strategy could not only provide excellent selectivity and specificity, but also achieve superior repeatability and stability in real complex serum samples. Therefore, the designed biosensing platform detected different microRNA through modulating the recognition sequence, which might provide a general strategy for various cancer analyses and have a promising potential for clinical application.