As one kind of tetracycline antibiotics, oxytetracycline (OTC) residues in animal-derived foods can do serious harm to human health. Though aptasensors for the detection of OTC are widely reported, label-free electrochemical aptasensor with low cost, simple preparation and good applicability should be further explored to meet the current urgent needs. In this study, a label-free electrochemical aptasensor for OTC determination was designed. The detection was based on specific recognition by the aptamer covalently-bound on the sensing interface via diazonium coupling reaction, which was verified by computer simulation. Experiment results showed that the differential pulse voltammetry (DPV) current response of the constructed electrochemical aptasensor was linear with the logarithm of OTC concentration in the range of 1.0 × 10⁻⁹ g mL⁻¹–1.0 × 10⁻⁴ g mL⁻¹ (R² = 0.9897) with the limit of detection of 2.29 × 10⁻¹⁰ g mL⁻¹. The proposed aptasensor indicated good selectivity, reproducibility and stability, which could be attributed to the stable modification of aptamer on the sensing interface. The OTC in the milk sample was detected by the spiked recovery method, and good results were obtained, with the recovery rate being 87.0%-99.3%. The proposed label-free electrochemical aptasensor can provide methods for low-cost, accurate and rapid detection of antibiotic residues.

动物食品中的土霉素作为一种四环素抗生素，会严重危害人体健康。尽管用于OTC检测的适体传感器已被广泛报道，但仍需进一步探索低成本，制备简单，适用性好的无标记电化学适体传感器，以满足当前的迫切需求。在这项研究中，设计了一种用于OTC测定的无标记电化学适体传感器。该检测是基于通过重氮偶合反应在传感界面上共价结合的适体的特异性识别，并通过计算机模拟进行验证。实验结果表明，所构建的电化学适体传感器的差分脉冲伏安（DPV）电流响应与OTC浓度的对数在1.0×10范围内呈线性关系^-9  g mL ^-1 -1.0×10 ^-4  g mL ^-1（R ²  = 0.9897），检出限为2.29×10 ^-10  g mL ^-1。提出的适体传感器具有良好的选择性，重现性和稳定性，这可以归因于适体在传感界面上的稳定修饰。采用加标回收法对牛奶样品中的OTC进行检测，回收率达87.0％-99.3％，效果良好。提出的无标记电化学适体传感器可提供低成本，准确，快速检测抗生素残留的方法。