Detecting attomolar concentrations of microRNA related to myelodysplastic syndromes in blood plasma using a novel sandwich assay with nanoparticle release.

Microribonucleic acids (miRNAs) are short noncoding ribonucleic acids that have been linked with a multitude of human diseases including lung, breast, and hematological cancers. In this work, we present a novel, extremely sensitive assay for the label-free optical biosensor-based detection of miRNAs, which is based on the oligonucleotide-triggered release of nanoparticles from a sensor surface. We combine this assay (herein referred to as the nanoparticle-release (NPR) assay) with a surface plasmon resonance biosensor and show that the assay is able to enhance the specific sensor response associated with the binding of target miRNA while suppressing the interfering effects caused by the non-specific binding. We apply the assay to the detection of miRNAs related to myelodysplastic syndromes (miR-125b, miR-16) in blood plasma and demonstrate that the assay enables detection of miR-125b with a limit of detection (LOD) of 349 aM (corresponding to the lowest detectable amounts of 419 zmol). The achieved LOD is better by a factor of ∼100 when compared to the conventional nanoparticle-enhanced sandwich assay. Moreover, we demonstrate that the NPR assay may be combined with time-division multiplexing for the multiplexed miRNA detection.