Dual-mode colorimetric electrochemical aptamer sensor based on Au@Pd bimetallic nanoparticles for the detection of Pb(II) in edible mushrooms.

Pb(II) can accumulate in the body and gradually cause irreversible harm. In this work, a dual-mode colorimetric biosensor based on an aptamer was developed as an effective method for sensitive sensing of Pb(II). The aptamers were immobilized on silver nanoparticles (Ag NPs) by Ag–S bonding to increase the active sites on the electrode surface. Gold–palladium bimetallic nanoparticles (Au@Pd NPs) can not only serve as signal indicators but also play a role as nanozymes. On the one hand, Au@Pd NPs were modified on the aptamer to improve the conductivity of the sensor for the detection of Pb(II) by the electrochemical method of differential pulse voltammetry (DPV). On the other hand, Au@Pd NPs were porous nanomaterials with numerous active sites on their surface that can catalyze the decomposition of hydrogen peroxide (H2O2) in solution to generate O2, so that 3,3′,5,5′-tetramethylbenzidine (TMB) was oxidized to blue oxTMB, enabling the visual prediction of Pb(II). At the same time, with the property that 8–17 deoxyribozyme and metal ions can co-catalyze, it promoted the binding of Au@Pd NPs functionalized aptamer to the electrode in the presence of Pb(II) and enhanced the electrochemical signal. Under optimal conditions, the detection range of Pb(II) was 1—1000 nmol L−1, and the limit of detection (LOD) was 0.4 nmol L−1. The biosensor has been successfully applied to the detection of edible mushroom samples. [ABSTRACT FROM AUTHOR]