SiRNA-directed self-assembled quantum dot biosensor for simultaneous detection of multiple microRNAs at the single-particle level.

MicroRNAs are essential post-transcriptional regulators and may act as the noninvasive biomarkers for disease diagnosis. Sensitive and multiplexed detection of microRNAs may facilitate the accurate and early clinical diagnosis, but the available methods are usually compromised by using organic dyes as the signal probes, laborious chemical and enzymatic manipulations, and the complicated reaction schemes. Here we reported a siRNA-directed self-assembled quantum dot (QD) biosensor for facile and simultaneous detection of multiple microRNAs. In this biosensor, the binding of microRNA targets with corresponding QD nanoprobes leads to the formation of siRNA duplexes, which not only induces the spectrally resolved coding of microRNAs, but also facilitates the assembly of QDs:magnetic nanoparticle bioconjugates for the isolation and enrichment of target microRNAs. The disassembled QDs can be sensitively detected by single-molecule detection, enabling quantitatively sensing of microRNAs at the single-particle level. This biosensor employs only QDs as the signal reporters, which can simultaneously detect multiple microRNAs from the same sample and achieves femtomolar sensitivity and single-base mismatch selectivity without the involvement of any target labeling and amplification steps. Moreover, it can be successfully applied for simultaneous detection of circulating microRNAs in clinical serum samples, holding great potential in non-invasive early diagnosis and biomedical researches.