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 0.36fM 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. [Display omitted] •An electrochemical strategy is developed for detecting microRNA-21 in the blood serum of breast cancer patients.•The specificities of T7 Exonuclease and T4 RNA ligase 2 are utilized to improve detection specificity and sensitivity.•The cyclic enzymatic amplification method is used to improve the sensitivity of this biosensor.•The proposed method showed wide linear range and low detection limit.