In this paper, an electrochemical aptasensor based on gold electrode (AuE)-modified Ag@Au core-shell nanoparticles was prepared. The surface of AuE was modified with Ag@Au core-shell nanoparticles to elevate APT binding sites and accelerate electron transfer properties between the electrode and ferrocene (Fc). When SM2 existed, the aptamer conformation would change and the response current intensity would increase because the Fc was pulled closer to the electrode surface. Subsequently, through a series of conditional optimization analysis, the optimal values of volume of Ag@Au core-shell, APT concentration, APT incubation time, and SM2 incubation time were 9 μL, 0.2 μmol/L, 75 min, and 40 min, respectively. Under optimum conditions, the results of differential pulse voltammetry experiments showed that the linear relationship was good in the range of 0.1~50 ng/mL, ΔI' (μA) = 1.145C (ng/mL) + 54.666, R2 = 0.964, with a detection limit of 0.033 ng/mL. The spiked recovery for SM2 in the pork samples was 92.6~101.0% and the relative standard deviation (RSD) was 2.7~4.1%, which indicated that the proposed aptasensor exhibited desirable performance in actual sample analysis. Graphical abstract An electrochemical aptasensor based on gold electrode-modified Ag@Au core-shell nanoparticles was prepared. The detection principle was on the basis of the change of current signal of DPV in Tris-HCl buffer solution before and after incubation of SM2. After the formation of APT-SM2 complex, the ferrocene modified on the aptamer was pulled closer to the electrode surface and sped up the electron transfer rate.
Keywords: Ag@Au core-shell; Aptasensor; Ferrocene; Gold electrode; Sulfamethazine.