A functionally differentiated DNA tetrahedron-based cascaded cyclic catalytic amplification assay for detecting miR-21 in prostate cancer.

A novel multi-functional DNA tetrahedron-based target-induced cascaded cyclic catalytic amplification (TICA) assay was developed for the sensitive detection of microRNA-21 (miR-21) in prostate cancer. This strategy ingeniously integrates two distinct DNA tetrahedron with specific functions (catalytic tetrahedron (Cat-DT) and signal DNA tetrahedron (Sig-DT)) to create a self-sustaining amplification circuit. The process is initiated when miR-21 triggers the release of a DNAzyme enzymatic strand (E-DNA), which converts Cat-DT into tri-branched DNA nanostructures (TB-DNA). Critically, each TB-DNA acts as a cascaded amplifier, bearing three E-DNA units that drive the exponential generation of more catalytic sites. Furthermore, the system employs an ingenious feedback loop: the TB-DNA/Sig-DT interaction produces a fluorescent signal while regenerating a miR-21-mimetic strand to perpetuate the catalytic cycle. This "target → catalyst → new target" paradigm enables ultra-efficient amplification, achieving a wide linear range from 600 fM to 100 nM and a low detection limit of 400 fM for miR-21. Notably, the TICA strategy significantly shortens the total reaction time to 80 min, demonstrating great potential for rapid and sensitive clinical diagnostics.