Programmable DNA nanowires mediated dispersion-to-localization catalytic hairpin assembly for high-contrast miRNA detection and imaging.

Accurate profiling of microRNAs (miRNAs) is often limited by the severe background leakage of conventional enzyme-free DNA amplification. Herein, we develop a 1D DNA nanowire-mediated dispersion-to-localization catalytic hairpin assembly (DL-CHA) platform for the highly sensitive detection of miRNAs. Methodologically, responsive hairpins are physically isolated on spatially dispersed nanowire scaffolds to rigorously suppress target-independent interactions. Upon specific recognition of miR-21, a pseudo-intramolecular cascade is triggered, dynamically cross-linking the scaffolds into a highly fluorescent DNA ladder. As a result, this DL-CHA platform yields an exceptional signal-to-background ratio of 12.4, a broad linear range of 0.05 to 250 nM, and an ultra-sensitive limit of detection of 50 pM without the need for exogenous enzymes. Furthermore, the rigid nanowire architecture ensures robust nuclease resistance and enables highly efficient, transfection-free internalization for the in situ imaging of endogenous miRNAs in living cells. Clinically, the platform accurately discriminated colorectal cancer patients from healthy controls using non-invasive liquid biopsies of human serum. This paradigm offers a robust, low-background molecular tool for precision cancer diagnostics.