Screening of broad-spectrum aptamers to construct an electrochemical aptasensor for the sensitive detection of tetracycline antibiotic residues in milk

Broad-spectrum aptamer has been shown to be an important probe for antibiotic multi-residue detection. In this study, we successfully screened a broad-spectrum aptamer (Apt-T1) that can recognize TCs with the same core structure using the graphene oxide (GO)-SELEX. Then Apt-T1 was truncated by molecular docking simulation to obtain an aptamer (Apt-T1-2) with higher specificity and affinity with a dissociation constant of 4.27-7.20 nM. On this basis, an electrochemical aptasensor based on Apt-T1-2 was constructed to achieve sensitive detection of TCs. Fe/ Zn-doped montmorillonite was synthesized by cation exchange technique for amplifying sensor signal. Under optimized conditions, the aptasensor showed a limit of detection of 0.46 nM and a linear range of 1-10,000 nM with a correlation coefficient (R2) of 0.989. Finally, the effects of the main components (fat, protein, Na+ and Ca2+) in milk on the electrochemical signal were investigated, and it was clear that fat and protein had a negative effect and so they were removed. The method was used to the determination of TCs in milk with recoveries of 98.26%-104.15%, which revealed its potential application for sensitive analysis in food safety control and also provided a new method for multi-residue detection of antibiotics in milk.