Cerium-based metal-organic framework as a target-responsive release system in an electrochemical aptasensor with Mg²⁺-driven DNAzyme signal switch for ultrasensitive detection of ofloxacin

A porous, small-sized Ce-based metal-organic framework (Ce-UiO-66) was synthesized using a simple and mild method. By integrating this material with an Mg²⁺-driven DNAzyme signal amplification strategy, a targeted responsive release system was developed for electrochemical aptasensors, enabling sensitive and selective detection of ofloxacin (OFL). Ce-UiO-66 served as an intelligent controlled-release platform, with cleavable hairpin DNA (HP) acting as a gating element to encapsulate methylene blue (MB) within its pores. In the presence of OFL, the aptamer-DNAzyme complex transitioned from a stable to a dissociated state, releasing DNAzyme to the electrode interface, where it recognized the enzyme cleavage site on HP, initiating a catalytic cleavage cycle and releasing substantial amounts of MB. To further enhance aptasensor performance, AuPt NPs/PEI-rGO was employed as the electrode modification material, significantly improving the conductivity and increasing the electrode's surface area, thereby providing more binding sites for the released MB. Under optimized conditions, the aptasensor achieved a detection limit of 0.058 pg/mL and a broad detection range from 1 × 10⁻⁷ to 1 μg/mL. This study offers new insights into the design of targeted responsive release systems and expands their potential applications, particularly in rapid food safety detection, demonstrating both practicality and sensitivity.