Highly sensitive and label-free detection of DILI microRNA biomarker via target recycling and primer exchange reaction amplifications.

MicroRNAs (miRNA) are closely associated with the development of diseases in life processes, and the sensitive detection of microRNA biomarkers is beneficial to disease diagnosis and treatment at early stage. Herein, by coupling the target sequence recycling with the primer exchange reaction (PER), a highly sensitive and non-label approach is constructed to detect miRNA-122, the biomarker for drug-induced liver injury. The target sequence cyclically displaces two hairpins on the DNA track via toehold-mediated strand displacement reactions with the assistance of the fuel DNA. The released hairpins further bind the primer to trigger the polymerase-aided PER process for the yield of plenty of G-quadruplex sequences, which then combine with the thioflavin T to drastically enhance its fluorescence for sensing miRNA-122 with a low 49.4 fM detection limit. Highly specific discrimination of the target miRNA-122 can also be realized with the proposed method. Because of the non-label format, high selectivity and sensitivity, such a method can be a convenient and universal means for sensing various biomarkers for disease diagnosis at the early stages.