Ultrasensitive Controlled Release Aptasensor Using Thymine–Hg<sup>2+</sup>–Thymine Mismatch as a Molecular Switch for Hg<sup>2+</sup> Detection
Ning Ma, Xiang Ren, Huan Wang, Xuan Kuang, Dawei Fan, Dan Wu, Qin Wei
Abstract
An ultrasensitive controlled release system electrochemical aptasensor (CRSEA) has been developed for supersensitive determination of mercury ions (Hg2+), using gold nanoparticle-linked specific single-stranded DNA (Au NPs-ssDNA) as a molecular gate and mesoporous silica nanocontainers (MSNs) as containers. MSNs have a rich porous structure, thus entrapping the toluidine blue (TB) molecules inside. It is worth noting that Hg2+ binds to the ssDNA with multiple thymine (T) and induces the ssDNA to form a hairpin structure, which makes the separation of the Au NPs-ssDNA from the MSNs. Eventually, the stored TB molecules were released from MSNs. The electron transfer signals of TB were detected stably by a differential pulse voltammetry (DPV) detection method, which are correlated with the concentration of Hg2+. Therefore, the wide linear range (10 pM–100 μM) and low limit of detection (2.9 pM) were obtained, and the system also displayed an apparent electrochemical signal response in real sample detection and showed a promising possibility in actual monitoring.