MicroRNA Imaging Encounters Rolling Circle Amplification: Intracellular Na⁺‑Fueled Linear Programmable DNAzyme Nanostructure

DNAzyme motors are widely used for the sensitive detection of intracellular miRNAs due to their excellent signal response. Generally, the addition of exogenous mental ions to DNAzyme motors is crucial for the efficient operation of the system. Moreover, the position of the DNAzyme relative to the substrate has a significant impact on the cleavage rate during the reaction. Herein, we proposed a highly loaded Na⁺-fueled linear programmable DNAzyme nanostructure (LPDN) composed of long, single-strand DNA produced by rolling circle amplification reactions that served as binding partners for Na⁺-specific DNAyme and substrate. In the meantime, the long, programmable scaffolds can precisely control the position of the DNAzyme and substrate for the optimal effect. During the assay, miR-21 and endogenous Na⁺ can specifically trigger multiple adjacent substrate-cleaving reactions, resulting in a significant recovery of the Cy3 fluorescence signal in living cells. This method could enable in situ real-time imaging and biocompatibility-enhancing evaluation of intracellular miR-21-level changes. Furthermore, LPDN’s ability to distinguish normal cells from cancer cells makes it a promising candidate for early cancer diagnosis and imaging analysis of cancer.