Shape-coded hydrogel microparticles integrated with hybridization chain reaction and a microfluidic chip for sensitive detection of multi-target miRNAs

The abnormal expressed miRNAs have been suggested as important biomarkers for disease diagnosis and prognosis. It is imperative to develop rapid, cost-effective, sensitive, and multiplexed detection of miRNAs. Taking advantages of hydrogel microparticles and the microfluidic techniques, a simple enzyme-free method based on shape-coded hydrogel microparticles combined with hybridization chain reaction (HCR) and a microfluidic chip was developed for multiplexed miRNA detection. Cascades of hybridization between carboxyfluorescein (FAM)-labeled hairpin probes were triggered to form long dsDNA products in hydrogel microparticles, which led to deposition of FAM in them. The proposed method exhibited good sensitivity with the limits of detection (LODs) of 27.8 pM and 24.7 pM for miRNA 21 and miRNA let-7a, respectively. Furthermore, one-base-mismatched sequences can be discriminated, which indicated the high specificity of the approach. Moveover, the proposed method were applied to parallel detection of multi-target miRNAs in real biological samples with favorable results. Finally, by integration of the proposed method with a microfluidic chip, the detection time was significantly shortened, the detection throughput was further enlarged, and the whole operations were greatly simplified.