Rapid and sensitive detection of RNA biomarkers using morpholino-functionalized organic electrochemical transistor

Ribonucleic acid (RNA) biomarkers have emerged as vital molecular indicators in precision medicine, with accurate detection being essential for effective disease diagnosis. Conventional methods for RNA detection often suffer from limitations including insufficient sensitivity, lengthy processing times and limited specificity, which can lead to false negatives and hamper clinical applications. Here we present a phosphorodiamidate morpholino oligomer (PMO) functionalized organic electrochemical transistor (OECT) biosensor designed for the ultrasensitive detection of RNA biomarkers. Utilizing PMO as capture probes, its neutral charge characteristics and high sequence specificity synergize with the low background noise of OECT to enhance hybridization efficiency with target RNA and exhibiting higher sensitivity than traditional DNA probes. The RNA biosensor is fast (<15 min from sample to result), label-free and works with clinical samples. The biosensor achieves an exceptionally low detection limit of 7 aM. It reliably and specifically detects ∼43 RNA molecules in 10 μL of sample solution on millimeter-sized electrodes in uncontrolled, ambient environments. The biosensor demonstrates a wide dynamic detection range spanning 7 orders of magnitude (attomolar to nanomolar), enabling sensitive identification of trace biomarkers while supporting quantitative analysis within the linear region. Furthermore, a well-defined distinction between complementary RNA and mismatched RNA was demonstrated. This biosensor represents a significant advancement in RNA detection, potentially transforming clinical diagnostics and enhancing biomarker analysis.