Amplification-Free and Mix-and-Read Analysis of Multiplexed MicroRNAs on a Single Plasmonic Microbead

In this work, a single microbead covered with a plasmonic layer is employed as the microreactor for the multiplexed miRNA analysis without nucleic acid amplification. On the plasmonic layer, the S9.6 antibody is adopted as the universal module for binding DNA/miRNA duplexes regardless of the sequence. Meanwhile, there is also a SERS reporter gold nanoparticle (GNP) pool, in which each group of GNPs is labeled with both a Raman coding molecule and a DNA probe for recognizing a given miRNA of interest. The target miRNAs will lead to the specific capture of the corresponding SERS reporter GNPs onto the plasmonic layer, which will enormously enhance the target miRNA-induced SERS signals. Finally, the enhanced SERS signals concentrated on the microbead will be mapped out by a confocal Raman microscope. The proposed method achieves the high-precision sensing of sub-pM target miRNA in a simple mix-and-read format and possesses multiplexed assay capability.