Ultrasensitive Detection of MicroRNAs with Morpholino-Functionalized Nanochannel Biosensor

Here we demonstrate a phosphorodiamidate morpholino oligos (PMO)-functionlized nanochannel biosensor for label-free detection of microRNAs (miRNAs) with ultrasensitivity and high sequence-specificity. PMO, as a capture probe, was covalently anchored on the nanochannel surface. Because of the neutral character and high sequence-specific affinity of PMO, hybridization efficiency between PMO and miRNAs was enhanced, thus decreasing background signals largely and improving the detection specificity and sensitivity highly. The miRNAs detection was realized through observing the change of surface charge density when PMO/miRNAs hybridization occurred. Not only could the developed biosensor specifically discriminate complementary miRNAs (Let-7b) from non-complementary miRNAs (miR-21) and one-base mismatched miRNAs (Let-7c), but also it could detect target miRNAs in serum samples. In addition, this nanochannel based biosensor attained a reliable limit of detection down to 1 fM in PBS and 10 fM in serum sample, respectively. It is expected that such a new method will benefit miRNA detection in clinical diagnosis.