Digital surface plasmon resonance imaging for attomolar detection of miR-451a

Microribonucleic acids (microRNAs, miRNAs) are important emerging biomarkers, yet their detection in clinical samples remains challenging due to their low concentrations and matrix effects, which typically require complex workflows including miRNA extraction, reverse transcription, and amplification. Here, we introduce a new approach to miRNA detection that combines a digital large-field-of-view surface plasmon resonance imaging platform capable of detecting individual gold nanoparticle labels, each associated with a single target miRNA molecule, with a molecularly triggered nanoparticle release (NPR) assay. We demonstrate that this method achieves a limit of detection as low as 15 aM (≈9000 copies/mL), providing PCR-comparable sensitivity with minimal sample preparation. We further demonstrate miR-451a quantification in clinical plasma samples from myelodysplastic neoplasms (MDS) patients and healthy controls, observing reduced levels of miR-451a in MDS patients and good correlation with digital droplet PCR (ddPCR) measurements. This approach provides an ultrasensitive, amplification-free route for miRNA analysis in biofluids and is readily adaptable to other miRNA targets, supporting future research and diagnostic applications.