A target-induced displacement-assisted colorimetric aptasensor for tetracycline detection based on Co MOF@Au NPs...

Tetracycline (TC) residues in milk present a potential risk to food safety and human health, highlighting the urgent need to develop rapid and reliable detection strategies. Herein, a target-induced displacement (TID)-based colorimetric aptasensor was assembled for the sensitive detection of TC using oxidase (OXD)-like nanozymes. The flower-like gold nanoparticle-decorated cobalt-based metal-organic frameworks (Co MOF@Au NPs) were synthesized through a facile two-step strategy, exhibiting excellent structural stability and catalytic activity toward the oxidation of TMB. Reactive oxygen species analysis confirmed that singlet oxygen (¹O₂) was the dominant reactive oxygen species involved in the catalytic process. Benefiting from the enhanced OXD-like catalytic performance and high substrate affinity of Co MOF@Au NPs, (specific activities of 34.32 U/mg), a competitive colorimetric aptasensor was prepared using aptamer-functionalized magnetic beads as capture probes and cDNA-modified Co MOF@Au NPs as signal probes. In the presence of TC, probes could release lead to a concentration-dependent colorimetric response. Under optimal conditions, the sensor achieved a wide linear range (60-240 nM) and a low detection limit (18.09 nM), while demonstrating excellent selectivity against common interferents. Furthermore, the practical applicability of the sensor was validated in milk samples with high recovery rates, offering a reliable and cost-effective approach for monitoring antibiotic residues in food safety applications.