A highly sensitive and selective homogenous assay for profiling microRNA expression

A highly sensitive and selective homogeneous microRNA (miRNA) assay is described in this report. It is based on the cleavage of DNAzyme moieties from miRNA-hybridized DNAzyme-capped capture probes (DZ-CPs) from magnetic beads by a duplex-specific nuclease (DSN). After removing the magnetic beads together with the unreacted DZ-CPs by using a permanent magnet, amplified colorimetric detection of the target miRNA is realized through the cleaved DNAzyme moieties-catalyzed oxidation of 3,3',5,5'-tetramethylbenzidine. The exceptional amplification power of the DSN and the cumulative nature of the signal generation process permit the colorimetric detection of miRNAs down to subfemtomolar levels. The isothermal amplification scheme together with the simple assay protocol makes direct profiling miRNA in real-world samples possible.