An Enzyme-Triggered Au–Se Nanodevice for Precise Imaging of MicroRNA

In situ imaging of microRNA (miRNA) in tumor cells is vital for clinical diagnosis and pathological research. However, achieving high-precision imaging is always limited by undesirable background signals. Herein, we introduced a gold-selenium-based nanodevice (AuSeND) for high-fidelity imaging of miRNA via enzyme-triggered catalytic hairpin assembly (CHA). This system employs an enzyme-activatable CHA circuit, constructed by extending a short tail at the 3' end of hairpin H1 with an apurinic/apyrimidinic (AP) site. The CHA circuit components are connected to the surface of AuNPs via Au-Se bonds, forming a Au-Se nanodevice. It remains inactive in normal cells, while in tumor cells, the CHA circuit is activated by apurinic/apyrimidinic endonuclease 1 (APE1) in the cytoplasm, generating a fluorescence signal under miRNA stimulation for miRNA imaging. The developed AuSeND enables cancer cell-selective miRNA imaging and improves the signal-to-noise ratio by combining the high stability of the Au-Se bond with the specific regulation of the APE1 enzyme, offering strong potential for clinical diagnostic applications.