Aptamer/Dopamine Molecularly Imprinted Polymer Composite Based pH Stability Improved Electrochemical Sensor for Simultaneous Detection of Cd(Ⅱ) and Hg(Ⅱ)

Abstract

Cd(II) and Hg(II) are well-known toxic heavy metal elements that are difficult to degrade by microorganisms in the environment. Limits for Cd(II) and Hg(II) in food have been established by the Chinese Government and other authorities. Aptamer-based electrochemical sensor detection is a promising method for rapidly and sensitively detecting heavy metals. However, aptamer configurations are easily affected by the environment and their stability needs to be improved. In this study, an ultra-sensitive electrochemical sensor was successfully constructed based on aptamer/dopamine molecularly imprinted polymer composite material, to explore the simultaneous detection of Cd(II) and Hg(II). Graphdiyne nanomaterial was used to increase the load of aptamer on the electrode surface. The aptamer of Cd(II) and Hg(II) was captured by AuNPs on a modified electrode through Au-S bonds. Dopamine was used as a functional monomer for self-polymerization to form an imprinted layer, stabilizing the aptamer conformation and enhancing its environmental tolerance. Under optimal conditions, the limits of detection (LOD) for Cd(II) and Hg(II) were 7.6 and 6.0 ng/mL, respectively. Six days of good stability in the sensor response were attained. The satisfactory recovery obtained in both crab and ribbonfish samples demonstrates this sensor's potential for multi-species food analysis.