Multiplexed Electrochemical Detection of MiRNAs from Sera of Glioma Patients at Different Stages via the Novel Conjugates of Conducting Magnetic Microbeads and Diblock Oligonucleotide-Modified Gold Nanoparticles

MicroRNAs (miRNAs) serve as diagnostic and prognostic biomarkers for a wide variety of cancers. Via the novel conjugates of gold nanoparticle-coated magnetic microbeads (AuNP-MMBs) and the diblock oligonucleotide (ODN)-modified AuNPs, multiplexed electrochemical assay of miRNAs was performed. The hybridization to target miRNAs leads to the conformational change of the hairpin-structured ODN probes, and the attachment of the diblock ODN-modified AuNPs was achieved. By examining the oxidation peak currents of methylene blue (MB) and ferrocene (Fc) moieties residing on the diblock ODNs, simultaneous quantification of miRNA-182 and miRNA-381 was conducted. The detection signals were significantly enhanced due to the numerous MB and Fc tags on the AuNPs. The proposed assay was highly selective for discriminating miRNAs with similar sequences, and detection limits of 0.20 fM and 0.12 fM for miRNA-182 and miRNA-381, respectively, were achieved. The feasibility of the method for sensitive determination of miRNA-182 and miRNA-381 from serum samples of glioma patients at different stages was demonstrated. The sensing protocol thus holds great potential for early diagnosis and treatment of cancer patients.