DNA-Functionalized Gold Nanorods for One-Step Simultaneous Determination of Multiple microRNAs Based upon Plasma-Enhanced Fluorescence

MicroRNAs (miRNAs) are endogenous, noncoding, and sequence-specific single-stranded RNA regulatory factors whose abnormal expression levels are closely related to various diseases, especially cancer, and are considered effective biomarkers for disease diagnosis and prognosis. Since the concentrations of miRNAs in the body are low and disease diagnosis by detecting single miRNAs may result in a high false positive, it is essential to construct a sensitive biosensor for the determination of multiple miRNAs. In this work, an enzyme-free signal amplification assay based on plasma-enhanced fluorescence (PEF) is reported for the one-step simultaneous determination of two miRNAs. Gold nanorods (AuNRs) were functionalized with fluorescein isothiocyanate (FAM)-tagged hairpin DNA1 (H1) and cyanine 5.5 (Cy5.5)-tagged hairpin DNA2 (H2). The fluorescence signals of FAM and Cy5.5 were quenched due to their proximity to the surface of the AuNRs. In the presence of target miRNA-21 and miRNA-155, H1 and H2 complemented miRNA-21 and miRNA-155, respectively, and the fluorescence signals of FAM and Cy5.5 were not only restored but amplified due to the plasma-enhanced fluorescence. A suitable linear range (0.1 to 10 nM) and low limits of detection for miRNA-21 (23 pM) and miRNA-155 (1.6 pM) were achieved. The developed assay for the one-step simultaneous measurement of two miRNAs is simple, fast and sensitive, exhibiting great potential for monitoring these biomarkers.