Study On Detection Of Oxytetracycline In Food By Aptamer Electrochemical Sensor

Oxytetracycline(OTC)one of the tetracycline antibiotics,could promotes the growth of animals,so it is often used for disease prevention and treatment or as a growth agent during the animal breeding.However,the unreasonable use of oxytetracycline may lead to the retention of oxytetracycline in animal food,and people’s long-term intake of these foods can be harmful to our health.At present,different detection methods have been reported to analyze the residue amount of OTC,but the instruments used in the traditional methods are relatively expensive,and the operation is complicated,which is not suitable for on-site detection.Therefore,it is urgent to explore a method for detecting oxytetracycline which is simple,stable,fast,and sensitive.Based on the advantages of aptamers and the advantages of electrochemical methods,we have constructed an aptamer electrochemical sensor that can quickly and efficiently detect OTC in this experiment,and the proposed electrochemical sensor can achieve rapid detection of OTC in milk.The aptamer electrochemical sensor was constructed as follows:the electrode was pretreated firstly,and after the 4-carboxyphenyldiazonium salt was modified on the surface of the pretreated electrode,1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride(EDC)and N-hydroxysuccinimide(NHS)as activator were used to activate the carboxyl group,and the aptamer was immobilized on the electrode surface by covalent bonding between amidogen of the aptamer and the carboxyl group.Cyclic voltammetry(CV),AC impedance method(EIS)and scanning electron microscope(SEM)were used to characterize the sensor construction process.The conditions affecting the performance of the aptamer sensor were optimized,including aptamer concentration,aptamer binding time and incubation time.The experiment results showed that the optimalconcentration of aptamer was 2 μmol/L,the optimal binding time of aptamer was 12 h,and the optimal incubation time between aptamer and OTC was 1 h.The performance test of the constructed OTC aptamer electrochemical sensor including the establishment of the OTC standard curve,the selectivity,repeatability,reproducibility and stability of the sensor,were tested.The experiment results showed that the DPV current response of the constructed aptamer electrochemical sensor was linear with the logarithm of OTC concentration in the range of 1×10-9 g/m L~1×10-4 g/m L,and the correlation coefficient was 0.9897.Moreover,the sensor can specifically recognize OTC,and has almost no recognition effect on doxycycline hydrochloride and chlortetracycline hydrochloride.OTC was tested in three replicates of 10-5g/m L and 1×10-6 g/m L,and their RSD of peak current response was 3.75%and 2.16%,the OTC of 1×10-9 g/m L~1×10-4 g/m L was measured three times,and the peak current response value was recorded by DPV method.The RSD of peak current response value of different concentrations of OTC between batches were not exceed 5%,indicating that the constructed aptamer electrochemical sensor had good stability.Three parallel prepared electrodes were placed at 4°C,and DPV was used to detect 10 ng/m L OTC every 5 days.After three times,the peak current response measured in the third time was about 81% of the original measured value.The OTC in the milk sample was detected by the method of spiked recovery,and the good results were obtained,the recovery rates were 87.0%-97.7%.