DNA Tetrahedron-Based MNAzyme for Sensitive Detection of microRNA with Elemental Tagging
Shaocheng Liu, Jingyi Wu, Man He, Beibei Chen, Qi Kang, Yan Xu, Xiao Yin, Bin Hu
Abstract
Heterogeneous immunoassay based on magnetic separation is commonly used in inductively coupled plasma-mass spectrometry (ICP-MS)-based biomedical analysis with elemental labeling. However, the functionalized magnetic beads (MBs) often suffer from non-specific adsorption and random distribution of the functional probes. To overcome these problems, DNA tetrahedron (DT)-functionalized MBs were designed and further conjugated with substrate modified Au NPs (Sub-AuNP). Based on the prepared MB-DT-AuNP probes, an MB-DT based multicomponent nucleic acid enzyme (MNAzyme) system involving Au NPs as the elemental tags was proposed for highly sensitive quantification of miRNA-155 by ICP-MS. Target miRNA would trigger the assembly of MNAzyme, and Sub-AuNP would be cleaved from the MB-DT-AuNP probe, resulting in a cyclic amplification. Single-stranded DNA-functionalized MB (MB-ssDNA)-AuNP probes were prepared as well. Comparatively, the amount of Au NPs grafted onto MB-ssDNA-AuNP probes was higher than that grafted onto MB-DT-AuNP probes. Meanwhile, a higher signal-to-noise ratio was obtained by using MB-DT-AuNP probes over MB-ssDNA-AuNP probes in the MNAzyme system. Under the optimal experimental conditions, the limit of detection for target miRNA obtained by using MB-DT-AuNP probes was 1.15 pmol L–1, improved by 23 times over that obtained by the use of MB-ssDNA-AuNP probes. The proposed MB-DT-MNAzyme-ICP-MS method was applied to the analysis of miRNA-155 in serum samples, and recoveries of 86.7–94.6% were obtained. This method is featured with high sensitivity, good specificity, and simple operation, showing a great application potential in biomedical analysis.