Inductively coupled plasma–mass spectrometry (ICP–MS)
with elemental labeling is a promising strategy for multiplex microRNA
(miRNA) analysis. However, it is still challenging for specific analysis
of multiple miRNAs with high homology, and the development of multiplex
assays is always limited by the complexity of the sequence design.
Herein, a simple and direct ICP–MS-based assay was developed
for the simultaneous detection of three miRNAs by combining the lanthanide
labeling strategy with entropy-driven catalytic (EDC) amplification.
Owing to the specificity of EDC for nucleic acid recognition, it is
able to differentiate miRNAs with single-base mutation in each EDC
circuit. A universal biotin-labeled DNA strand was designed to hybridize
with the DNA substrates for three EDC circuits, targeting miRNA-21,
miRNA-155, and miRNA-10b, respectively. All the substrates were loaded
on the surface of streptavidin magnetic beads. In the presence of
target miRNA, the EDC reaction was initiated, and EDC substrates were
dissociated, continuously releasing reporter strands that were labeled
with lanthanides (Tb/Ho/Lu). After magnetic separation, the supernatant
containing the released reporter strands was introduced into an ICP–MS
system for simultaneous detection of 159Tb/165Ho/175Lu and quantification of miRNA-21, miRNA-155, and
miRNA-10b, respectively. The limits of detection were 7.4, 7.5, and
11 pmol L–1 for miRNA-21, miRNA-155, and miRNA-10b,
respectively. Overall, this study provides a powerful strategy for
simultaneous quantification of multiple miRNAs, with the advantages
of flexible probe design, good sensitivity, and excellent specificity.