Sensitive and selective electrochemical aptasensor via diazonium-coupling reaction for label-free determination of oxytetracycline in milk samples

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.