Primer exchange reaction transcribed DNAzyme catalyzed DNA walker for sensitive cerebral infarction-related microRNA analysis by coupling plasma mass spectrometry

Abstract Cerebral infarction remains a leading cause of long-term disability and mortality, necessitating sensitive and reliable methods for early diagnosis. Herein, we develop a novel biosensing platform based on a primer exchange reaction (PER)-transcribed DNAzyme-catalyzed DNA walker coupled with inductively coupled plasma mass spectrometry (ICP-MS) for the detection of cerebral infarction-related microRNA-124. The target miRNA triggers split DNAzyme assembly, which cleaves a dumbbell-structured tracker to release a PER template. The PER process generates numerous DNAzyme strands that cyclically cleave Pt-labeled substrates, releasing platinum for ICP-MS quantification. This cascade amplification strategy achieves a detection limit as low as 0.11 fM with a linear range from 1 fM to 100 pM. The method exhibits excellent single-nucleotide discrimination capability, satisfactory recovery (94.1%–102.4%) in spiked serum samples, and high consistency with qPCR (correlation coefficient 0.9943). When applied to clinical serum samples, the platform successfully distinguishes cerebral infarction patients from healthy controls by detecting significantly elevated miRNA-124 levels. This PER-transcribed DNAzyme walker platform offers a highly sensitive, specific, and robust tool for early diagnosis and prognostic monitoring of cerebral infarction, and can be readily adapted for other low-abundance disease biomarkers.