In-situ integrated Ce-MOF-808@CeO2 as bifunctional matrix for sensitive electrochemical-aptasensing of tetracycline in shrimp

The integration of aptamer chemistry with innovative functional materials such as nanozymes offers new opportunities for the development of the superior electrochemical biosensors. Herein, we introduce a rod-like nanocomposite of Ce-MOF-808@CeO₂ bearing intense nanozymatic activity that prepared through in-situ partial oxidation of Ce-MOF-808 to CeO₂. Then, the aptamer for tetracycline (TC-Apt) with 5’-PO₄³⁻ end was anchored on Ce-MOF-808@CeO₂ modified screen-printed electrode, thereby assembling a label-free electrochemical aptasensor. Electrochemical and spectroscopic assays reveal that the derived CeO₂ can effectively promote the nanozyme activity of Ce-MOF-808 as a cocatalyst. Electrochemical biosensing shows that, the capture of tetracycline (TC) to the electrode surface by the aptamer chemistry significantly inhibits the catalytic activity of Ce-MOF-808@CeO₂. Thus, TC can be analyzed by monitoring the catalytic signal of the biosensor to H₂O₂. Leveraging the exceptional catalytic activity of Ce-MOF-808@CeO₂, coupled with the high specificity of the aptamer, TC can be analyzed in a wide kinetic range from 1 pM to 100 nM, with a low detection limit of 0.21 pM. The aptasensor is also applicable for the accurate detection of TC residues in fresh shrimp samples, showcasing its potential for practical applications in the monitoring of food safety.