LAUSR

In this work, based on mesoporous silica containers (MSNs) with the programmed enzyme-free DNA assembly amplification of catalytic hairpin assembly (CHA) and hybridization chain reaction (HCR), an ultrasensitive electrochemical sensing platform with low background is developed for the detection of microRNA (miRNA). Herein, the electrochemical reporter methylene blue (MB) was sealed in the pores of MSNs by the double-stranded DNA (dsDNA) gate of hairpin DNA H1 and anchor DNA. In the absence of target, there happened neither CHA nor HCR process, which enabled a low background. After target added, DNA H1 was displaced from the MSNs surface and participated in the CHA process with the assistance of hairpin DNA H2, which accelerated the release of MB from the MSNs pore. Meanwhile, the CHA products H1-H2 were hybridized with the capture probes (SH-CP) on the electrode surface, which further initiated the HCR process. The released MB from the MSNs will effectively intercalate into long dsDNA polymers of HCR products, resulting in a significant electrochemical response. Taking miRNA-21 as the model target, the proposed sensing platform achieves a satisfactory detection limit down to 0.037 fM, which is lower than that of electrochemical assay with amplification methods. In addition, the strategy shows good selectivity against other miRNA and is capable in practical analytes. Benefited from the features of label-free, enzyme-free, low background, high sensitivity and selectivity, this strategy shows great potential in bioanalysis and clinical diagnostics.