Ultrasensitive electrochemical detection of miRNA based on DNA strand displacement polymerization and Ca2+-dependent DNAzyme cleavage.

miRNAs are novel diagnostic and prognostic biomarkers for a diversity of diseases like cancers. In this study, an ultrasensitive electrochemical biosensor for miRNA evaluation is fabricated. A methylene blue (MB) labeled DNA probe is firstly modified on a gold electrode. By employing target induced strand displacement amplification and subsequent DNAzyme cleavage cycles, a large number of MB molecules are released. The decreased oxidation peak current could be used to reveal the miRNA concentration. Based on the two efficient signal amplifications, this method shows ultrahigh sensitivity. Its feasibility for the analysis of miRNA in cell lysates is also demonstrated. Therefore, the method shows attractive potential for promising applications in early diagnosis of certain diseases.