Cascade toehold-mediated strand displacement reaction for ultrasensitive detection of exosomal microrna

Abstract

MicroRNA (miRNA) in exosomes is a powerful molecular signature for early diagnosis of cancers with the merits of high specificity and high stability. Herein, we report an ultrasensitive electrochemical assay to measure miRNA using a cascade toeholdmediated strand displacement reaction (SDR). In SDR, the trapped exosomal miRNA releases a large amount of single-stranded DNA in the solution. The product then triggers the downstream SDR at the electrode surface. Furthermore, reductant-assisted electrochemical amplification is introduced to adjust the recorded signal intensity. Under optimal conditions, ultrahigh sensitivity is achieved with excellent signal amplification efficiency. The proposed method also performs well in biological samples and successfully distinguishes patient samples from healthy controls in practical use. Therefore, this work provides a promising approach for exosomal miRNA analysis, which has great potential utility in cancer diagnostics.