A novel electrochemical aptasensor based on gold electrode decorated Ag@Au core-shell nanoparticles for sulfamethazine determination.

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 SM 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 SM 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 0.150 ng/mL, ΔI' (μA) = 1.145C (ng/mL) + 54.666, R = 0.964, with a detection limit of 0.033 ng/mL. The spiked recovery for SM in the pork samples was 92.6101.0% 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 SM. After the formation of APT-SM complex, the ferrocene modified on the aptamer was pulled closer to the electrode surface and sped up the electron transfer rate.