Nucleic acid aptamer-functionalized magnetic MIL-53(Al)-NH ₂ for highly selective magnetic dispersion solid-phase extraction of chloramphenicol

Chloramphenicol (CAP), a broad-spectrum antibiotic banned in food animals due to its toxic effects (e.g., myelosuppression), requires sensitive analytical methods for the detection and monitoring of its residues in food. Herein, an aptamer-functionalized magnetic MOF composite (CAP-Apt@MMIL-53(Al)-NH₂) was prepared, coupled with a HPLC method developed for CAP detection. The material was synthesized as follows: solvothermally prepared Fe₃O₄ particles were coated with SiO₂, modified with mercaptoacetic acid, and self-assembled with Al³⁺ and 2-aminoterephthalic acid to form MMIL-53(Al)-NH₂. Its porous framework and abundant amino sites enable efficient mass transfer and aptamer immobilization. CAP aptamers were then covalently bonded to its surface amino sites, yielding CAP-Apt@MMIL-53(Al)-NH₂ with high selectivity. Notably, the material reaches extraction equilibrium within 5 minutes, with 2.2-fold higher efficiency than MMIL-53(Al)-NH₂ and 2.5-5.8-fold higher efficiency than traditional adsorbents, and exhibits significantly reduced post-extraction chromatographic interference. The analytical method exhibited a linear range of 10-1000 μg L⁻¹ (R² = 0.998) and an LOD of 4.89 μg L⁻¹. Applied to milk and honey, it yielded recoveries of 84.3%-110.1% and 88.0%-118.0%, respectively. This approach enables rapid, selective, and sensitive detection of trace CAP in complex food matrices, providing a novel strategy for food safety monitoring of CAP residues.