Label-free and enzyme-free detection of microRNA based on a hybridization chain reaction with hemin/G-quadruplex enzymatic catalysis-induced MoS2 quantum dots via the inner filter effect

Abstract

A new simple, sensitive and specific strategy for microRNA analysis has been described based on a hybridization chain reaction with hemin/G-quadruplex enzymatic catalysis-induced MoS₂ quantum dots via the inner filter effect. The target microRNA triggers the hybridization chain reaction between two DNA probes to generate long dsDNA with many hemin/G-quadruplex DNAzymes in the presence of hemin. With the assistance of H₂O₂, the produced hemin/G-quadruplex DNAzyme could oxidize o-phenylenediamine (OPD) to 2,3-diaminophenazine (DAP) directly, resulting in the fluorescence quenching of MoS₂ quantum dots via the inner filter effect. As an example, the fluorescence response of MoS₂ quantum dots is linearly related with the logarithm of the microRNA let-7a concentration with a detection limit of 42 fM. The proposed label-free assay has promising potential to be applied in practical diagnosis.