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

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 & PRIME;,5,5 & PRIME;-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 & mu;M, and the detection limit (LOD) is 0.28 nM.