Detection of specific sequences in RNA using differential adsorption of single-stranded oligonucleotides on gold nanoparticles

We have used the disparity in adsorption rates for single- and double-stranded RNA on ionically coated gold nanoparticles suspended in a colloid to design a rapid sequence identification assay. Unlabeled target RNA and a probe sequence are mixed prior to exposure to the gold nanoparticles to enable efficient hybridization. We have designed assays based on either color changes or fluorescence that are sensitive to a few picomoles of target. Single-base mutations on RNA sequences can be detected even in complex oligonucleotide mixtures. The assay requires less than 10 min so that RNA degradation problems are avoided.