Two-stage cyclic enzymatic amplification method for ultrasensitive electrochemical assay of microRNA-21 in the blood serum of gastric cancer patients

MicroRNA (miRNA) is riveting nowadays due to its close relevance to human malignancies. Exploiting a fast and convenient biosensor for sensitive and specific detecting miRNA is necessary and it has significant meaning for oncology. In this work, to understand the relationship between miRNA-21 and gastric cancer, we employ T4 RNA ligase 2 to initiate specific ligation reaction depending on the sequence of target RNA, and T7 exonuclease to catalyze the first stage cyclic enzymatic amplification method (CEAM) specifically, which also resting on the target RNA sequence , and the second stage CEAM to further amplify the response resulting from the initial target RNA. Our two-stage CEAM strategy can detect miRNA-21 as low as 0.36   fM with remarkable specificity, and most importantly, it can be used to inspect the expression level of miRNA-21 in blood serum of gastric cancer patients . This will offer new perspective for figuring out the pathways of miRNA-21 involving in cancer.