Multicolor Hg2+ sensor based on the regulation of peroxidase activity of Fe/Co-MIL-88(NH2) and etching of gold nanobipyramids

Abstract

The entry of Hg2+ into the human body can lead to serious damage to some organs and it is vital to construct some simple but sensitive Hg2+ assay methods. A multicolor sensor for Hg2+ was constructed depended on the inhibition of peroxidase activity of Fe/Co-MIL-88(NH2) mediated by DNA and color change caused by the etching of gold nanobipyramids (Au NBPs). The enzymatic activity of Fe/Co-MIL-88(NH2) can be inhibited by adsorbing the T-rich oligonucleotide sequence on its surface. Hg2+ can combine with thymine of the T-rich oligonucleotide sequence to constitute T-Hg2+-T complex, and cause the transforming of T-rich oligonucleotide sequence into three-dimensional structure and desorbed from Fe/Co-MIL-88(NH2) surface. Which results in the restoration of the peroxidase activity of Fe/Co-MIL-88(NH2), and then it catalyzes the 3,3′,5,5′-tetramethylbenzidine (TMB) to engender TMB2+, TMB2+ can etch Au NBPs, this accompanied with a peak shift of the UV–vis spectrum and recognizable color changes of the system. Semi-quantitative can be realized using the multicolor changes of the Au NBPs as the reading mode. Furthermore, quantitative sensing can be achieved by measuring the UV–vis peak shift of the system. The linear response range is 1.0 nM–10 µM, and the detection limit (LOD) is 0.28 nM.