Ultrasensitive electrochemical detection of cancer-associated circulating microRNA in serum samples based on DNA concatamers.

MicroRNAs (miRNAs), a kind of endogenous, noncoding RNAs (19-24 nucleotides), play vital roles in regulating gene expression and cellular processes. In recent years, it has been found that circulating miRNAs are differentially expressed in patients and healthy controls. This leads to the suggestion that circulating miRNAs are promising biomarkers for cancer classification and prognosis. However, it is still difficult to detect circulating miRNAs directly from real samples such as human serum without prior extraction and purification. In this work, we developed an ultrasensitive electrochemical biosensor for detection of cancer-associated circulating miRNAs based on DNA concatamers amplification. The proposed biosensor showed a high sensitivity for target miRNA-21 in a concentration range from 100 aM to 100 pM with a detection limit of 100 aM. Furthermore, the biosensor was successfully employed for direct detection of circulating miRNAs in human serum. Due to the high sensitivity, good selectivity and stability, the proposed electrochemical biosensor might have potential clinical application for circulating miRNAs in relation to diagnosis and prognosis.