An intelligent DNAzyme theranostic probe for in situ FTO bioimaging and real-time therapeutic efficacy evaluation in living cells.

Real-time bioimaging of epigenetic dynamics in living cells is essential for precision oncology. However, it remains technically challenging due to the lack of theranostic probes capable of both sensitive detection and dynamic efficacy feedback. Here, we report an intelligent DNAzyme-based theranostic probe (GF@ZD) for in situ bioimaging of endogenous active FTO and therapeutic efficacy evaluation in living cells. GF@ZD is constructed by encapsulating glucose oxidase (GOx) and Fe0 within a pH-responsive zeolitic imidazolate framework-8 (ZIF-8), followed by surface conjugation of an m6A-locked 8-17E DNAzyme (m6A-DNAzyme) probe. Upon exposure to the acidic tumor microenvironment, the theranostic probe degrades to release GOx, Fe2+, Zn2+, and the m6A-DNAzyme. Notably, co-released Fe2+ enhances endogenous FTO activity, while Zn2+ serves as a self-supplied cofactor for DNAzyme catalysis. FTO-mediated demethylation unlocks the m6A-DNAzyme, restoring Cy3 fluorescence for real-time, sensitive imaging of intracellular active FTO and enabling discrimination between cancerous and normal cells. For efficacy evaluation, the GOx and Fe2+ induce glucose deprivation to drive a cascade catalytic therapy and lead to FTO downregulation; this process is self-reported by GF@ZD through progressive fluorescence attenuation, enabling real-time visual assessment of the therapeutic outcome. Furthermore, using rhein as a model inhibitor, GF@ZD enables evaluation of FTO inhibitor efficacy. By integrating acidic-responsiveness, Fe2+-enhanced FTO activation, self-supplied Zn2+, m6A-DNAzyme probe-based bioimaging, and built-in glucose-regulated feedback, GF@ZD provides a powerful tool for real-time visualization of FTO activity and pioneers a feedback-driven strategy for therapeutic efficacy evaluation in drug screening and precision medicine.