A tetrahedral DNA nanostructure functionalized paper-based platform for ultrasensitive colorimetric mercury detection

A novel tetrahedral DNA nanostructure (TDN) functionalized paper-based colorimetric sensor was developed for ultrasensitive analysis of mercury ion (Hg2+). On the paper-based platform, TDN was used as scaffold to anchor aptamer to improve the capture efficiency owing to the controllably specific orientation, low steric hindrance effect and well-defined spacing. In the absence of Hg2+, biotinylated aptamer would bind with streptavidin-labeled HRP. Whereas, in the presence of Hg2+, aptamer would preferentially bind to Hg2+ owing to the higher binding constant of T–Hg–T than that of T–A, which consequently leading to the biotinylated aptamer releasing from TDN. After introducing TMB-H2O2 solution, strong variation of color signal could be observed. Therefore, the quantitative analysis of Hg2+ was carried out by using smartphone to monitor the color intensity on paper chip. The proposed strategy exhibits good linearity over a wide range of 10–13–10–7 M with a low detection limit of 30 fM. And this method had been successfully applied in real water samples. Our strategy provided a versatile, low-cost and user-friendly paper-based monitoring platform for rapid and ultrasensitive analysis of heavy metal ions and thus had potential applications in food safety and public health.