Orthogonal cascade amplification via dual-stage ROMP for ultrasensitive miRNA-21 detection

Orthogonal dual-stage ROMP cascade enables ultrasensitive miRNA-21 detection. • Scaffold construction and signal amplification are decoupled. • The sensor detects miRNA-21 with a detection limit of 2.24 aM. • High selectivity and reliable performance in complex serum matrices. Traditional ring-opening metathesis polymerization (ROMP)-based biosensors typically couple scaffold construction and signal amplification within a single polymerization step, which limits the independent optimization of mechanical stability and electrochemical performance. This study developed an orthogonal two-stage ROMP cascade amplification strategy that successfully decoupled these two processes. Target-specific hybridization first triggers Zr 4+ coordination, initiating surface-mediated metal-catalyzed ROMP to construct a dense polynorbornene scaffold bearing cyclic anhydride side chains. Subsequently, metal-free ROMP driven by visible light grafts high-density ferrocene monomers onto the pre-assembled scaffold, forming electroactive bottlebrush polymers. This biosensor achieves a detection limit for miRNA-21 as low as 2.24 aM, with a linear range from 10 aM to 1 nM, and exhibits excellent selectivity against mismatched RNA sequences, as well as reliable detection performance in complex serum matrices. The orthogonal cascade strategy proposed in this study provides a modular and versatile new platform for the ultrasensitive detection of low-abundance biomarkers. Download: Download high-res image (116KB) Download: Download full-size image