Quantification of microRNA by gold nanoparticle probes.

MicroRNAs are important posttranscriptional regulators of gene expression in animals and plants. A sensitive and specific detection method is urgently needed for intensive studies on differential expression and regulatory roles of microRNA. Here we present a simple and reliable method for the quantification of microRNA. The hybridization products of target microRNA with capture probe and gold nanoparticle probe are immobilized onto the surface of a streptavidin-coated microplate, and the signal is amplified by silver enhancement. Distribution of miR-122a/miR-128 in mouse brain and liver tissue was detected by this method, and synthetic miRNA122a was quantified. This method allowed a lower detect limit of 10 fM with a linear dynamic range from 10 pM to 10 fM and a high specificity to discriminate one single oligonucleotide mismatch of the target microRNA.