Here, we demonstrate a phosphorodiamidate morpholino oligos (PMO)-functionalized 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 largely decreasing background signals and highly improving the detection specificity and sensitivity. 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 noncomplementary 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.
Compared
with free miRNAs in blood, miRNAs in exosomes have higher
abundance and stability. Therefore, miRNAs in exosomes can be regarded
as an ideal tumor marker for early cancer diagnosis. Here, a peptide
nucleic acid (PNA)-functionalized nanochannel biosensor for the ultrasensitive
and specific detection of tumor exosomal miRNAs is proposed. After
PNA was covalently bound to the inner surface of the nanochannels,
the detection of tumor exosomal miRNAs was achieved by the charge
changes on the surface of nanochannels before and after hybridization
(PNA–miRNA). Due to the neutral characteristics of PNA, the
efficiency of PNA–miRNA hybridization was improved by significantly
reducing the background signal. This biosensor could not only specifically
distinguish target miRNA-10b from single-base mismatched miRNA but
also achieve a detection limit as low as 75 aM. Moreover, the biosensor
was further used to detect exosomal miRNA-10b derived from pancreatic
cancer cells and normal pancreatic cells. The results indicate that
this biosensor could effectively distinguish pancreatic cancer tumor-derived
exosomes from the normal control group, and the detection results
show good consistency with those of the quantitative reverse-transcription
polymerase chain reaction method. In addition, the biosensor was used
to detect exosomal miRNA-10b in clinical plasma samples, and it was
found that the content of exosomal miRNA-10b in cancer patients was
generally higher than that of healthy individuals, proving that the
method is expected to be applied for the early diagnosis of cancer.
The rapid extraction of high-purity nucleic acids from complex biological samples using conventional methods is complicated. Therefore, in this study, a glycine-pillar[6]arene (Gly-P6) functionalized tapered nanochannels were constructed using 32mer...
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