Oligonucleotide Cross-Linked Hydrogel for Recognition and Quantitation of MicroRNAs Based on a Portable Glucometer Readout

A novel sensing platform for recognition and quantification of target microRNAs (miRNAs) was developed by combining an amylase-trapped DNA hydrogel, multi-component nucleic acid enzymes (MNAzymes), and a portable glucometer (PGM) readout. First, the amylase was encapsulated inside the DNA hydrogel and physically separated from its substrate of amylose, which was in a solution outside the hydrogel. After addition of the target miRNA, the activity of the MNAzyme was restored, which cuts off the substrate linker strand. The active MNAzyme can catalytically act upon multiple substrate strands through diffusion, leading to the collapse of the hydrogel and the release of amylase, which catalyzes the hydrolysis of amylose to produce a large amount of glucose and generate a high PGM signal. The smart usage of the PGM enables simple portable detection of miR-21, with a detection limit as low as 0.325 fmol. Additionally, through the simple rational design of the target binding sensor arms, the amylase-trapped DNA hydrogel sensing platform was successfully applied in the detection of multiple endogenous miRNAs (including miR-21, miR-335, miR-155, and miR-122) extracted from HeLa cells, HepG2 cells, MCF-7 cells, and L02 cells.