Circle Padlock-Mediated\nCatalytic Hairpin Assembly\nCooperating Primer Exchange Reaction for Sensitive and Label-Free\nMicroRNA Detection

MicroRNAs (miRNAs), which play critical roles in regulating\ngene\nexpression and cell functions, are recognized as potential biomarkers\nfor various human diseases, including gastric ulcers. The reliable,\nspecific, and sensitive detection of miRNA is highly recommended for\nthe clinical diagnosis and therapy of different diseases. Herein,\nwe depict a label-free and low-background fluorescent assay for the\nhighly sensitive detection of miRNAs by coupling target miRNA-triggered\ncyclization of a padlock, circular padlock-mediated catalytic hairpin\nassembly (CHA), and primer exchange reaction (PER)-assisted signal\ngeneration. The padlock probe recognizes the target miRNA, forming\na circular padlock that subsequently facilitates the CHA. The subsequent\nPER process generates substantial quantities of G-quadruplex sequences\nthat rapidly combine with thioflavin T to create substantial fluorescence,\nthereby enabling the highly sensitive detection of the target miRNA.\nThis method demonstrated significant potential for the early diagnosis\nof diseases such as gastric ulcers, as it could conclude the detection\nprocess in human serum samples within hours.