Epigenetically modified DNAzyme walkers for simultaneous imaging of MGMT and FTO activity in living cancer cells

Aberrant demethylase activity is intimately associated with cancer initiation and progression, necessitating sensitive detection methods for biological applications.We developed epigenetically modified DNAzyme-powered walkers (EMOWAs) immobilized on gold nanoparticles for simultaneous detection of O⁶-methylguanine-DNA methyltransferase (MGMT) and fat mass and obesity-associated protein (FTO). The 8-17 DNAzymes were inactivated by incorporating N⁶-methyladenine or O⁶-methylguanine modifications at catalytic cores, which are specifically removed by target demethylases to restore enzymatic activity. Signal amplification was achieved through autonomous walker movement along nanoparticle surfaces. The dual-EMOWA@AuNP system achieved detection limits of 8.8 ± 0.3 pM for MGMT and 5.7 ± 0.2 pM, representing approximately 100-fold improvement over existing methods. The orthogonal metal ion dependencies (Mg²⁺/Zn²⁺) ensured cross-reactivity-free multiplexed detection. Cellular imaging successfully distinguished T98G, MCF-7, and U87 cancer cell lines based on their demethylase expression profiles, with fluorescence intensities showing excellent correlation with Western blot analysis (R² > 0.98). In vivo studies in tumor-bearing mice demonstrated specific tumor accumulation, precise signal localization, and minimal systemic toxicity. This work establishes a sensitive, specific, and biocompatible platform for multiplexed visualization of demethylase activities in living cells and animals, providing a valuable tool for understanding cancer epigenetics and guiding targeted therapeutic development.