An electrochemical signal ‘off–on’ sensing platform for microRNA detection

The abnormal expression of microRNAs (miRNAs) in many solid tumors makes miRNAs potential biomarkers for disease diagnosis and highlights the need for the sensitive and selective detection of miRNAs. In the present work, an ‘off-on’ signaling genosensor platform for miRNA-21 detection was well developed. This tactic was based on a locked nucleic acid-integrated nucleic acid hairpin probe, a biotin-labeled bridge DNA–AuNPs–bio-barcode signal amplification unit and enzymatic signal amplification. The test is simple, fast and ultrasensitive with a linear range of 0.01–700 pM. The detection limit was estimated to be 6 fM. The overexpression of miRNA-21 was confirmed in total RNA extracted from human hepatocarcinoma cells BEL-7402 and human HeLa cells compared with the control sample extracted from normal human hepatic L02 cells. This method does not need miRNA-21 labeling, isolation, enrichment or PCR amplification. The performance of the assay developed here could satisfy the need for rapid, easy, sensitive and specific early cancer diagnosis in clinical diagnostics.