Microsphere-based suspension array for simultaneous recognition and quantification of multiple cancer-associated miRNA via DNAzyme-Mediated signal amplification

Herein, a novel suspension array of polystyrene (PS) beads for simultaneous recognition and quantification of multiple cancer-associated microRNAs (miRNAs) using flow cytometry has been reported. The suspension array contained three moieties, streptavidin-modified PS beads, biotin-labeled substrate strands (17S) of the 17–8 DNAzyme and two split DNAzyme parts (PA, PB). 17S was labeled with 6-carboxyfluorescein (FAM) and Dabcyl on both sides of the ribonucleic acid. Once the target miRNAs appear, they can bind with the corresponding PA and PB to form an active secondary structure of DNAzyme. The active DNAzyme can cleave 17S and remove Dabcyl from the bead's surface, thus recovering the FAM's fluorescence intensity. Furthermore, the released target miRNA can autonomously move to the neighboring inactive DNAzyme for further cleavage, thus amplifying the fluorescence signal. Therefore, the target miRNAs can be quantified by reading the fluorescence intensity output from flow cytometry. The PS beads-based suspension array for the target miRNA in buffer shows good selectivity and high sensitivity. Via binding with a different pair of PA and PB, this suspension sensor array has successfully typed and quantified cancer-associated miRNAs of miR-21, miR-155, miR-335, and miR-122 in buffer and serum conditions.