Framework Nucleic Acid-Based Spatial-Confinement Amplifier for miRNA Imaging in Living Cells

. Herein, we report a framework nucleic acid (FNA)-based nonenzymatic spatial-confinement amplifier for rapid and reliable intracellular miRNA imaging. The amplifier consists of a localized catalytic hairpin assembly (L-CHA) reactor encapsulated in the inner cavity of an FNA (a 20 bp cube). The L-CHA reactor is certainly confined to the internal frame by integrating two probes (H1 and H2) of the L-CHA within a DNA strand and harnessing it to the opposite angles of the cube. We find that the stability of the amplifier is remarkably improved due to the protection of the FNA. More importantly, the spatial-confinement effect of the FNA can endow the confined L-CHA amplifier with enhanced local concentrations of reagents (5000-fold), thereby accelerating the reaction rate and improving the dynamic performance (up to 14.34-fold). With these advantages, the proposed amplifier can enable accurate and effective monitoring of miRNA expression levels in living cells and poses great potential in medical diagnostics and biomedical research.