Programmable DNAzyme Walkers on Lipid Micelles Enable Endogenous Activation and Spatially Resolved Imaging of Magnesium Ions in Cells and Animals

Abstract

Spatiotemporal imaging of intracellular metal ions is essential for deciphering their roles in disease pathogenesis, yet achieving high-contrast visualization specifically in diseased cells over healthy counterparts remains a formidable challenge. Here we engineer a programmable DNAzyme walker platform assembled on cholesterol-functionalized lipid micelles, termed a lipid-micelle DNAzyme walker (LDzW). Through hydrophobic self-assembly, cholesterol-DNA amphiphiles coalesce into lipid micelles, the surface of which then hosts a dense three-dimensional probe array built via DNA hybridization, a configuration that locally concentrates DNAzymes and fuels their processive, autonomous walking for sustained signal amplification. The DNAzyme is initially locked by a blocking strand carrying an abasic site, recognized and cleaved by apurinic/apyrimidinic endonuclease 1 (APE1), an enzyme elevated in malignant and inflamed cells. To restrict activation exclusively to diseased cells, we implement a dual-lock AND gate requiring both APE1 activity and the Mg2+ cofactor. Thus, only cells with elevated APE1 and abundant Mg2+ (e.g., tumor cells) trigger the system. Upon APE1-mediated liberation, the DNAzyme executes autonomous walking along the micelle surface, driving robust catalytic signal amplification. This integrated design achieves endogenous, background-free, tumor-selective Mg2+ imaging in living cells and tumor-bearing mice, with negligible signal in normal tissues. The modular LDzW architecture readily adapts to other metal ions or disease biomarkers by swapping the DNAzyme and locking modules. By enabling spatiotemporally precise, cell-type-specific metal ion imaging, this work establishes a versatile tool for interrogating metal homeostasis in cancer biology and other pathologies, advancing precision diagnostics.