Detection of Metal Ions (Cu 2+ , Hg 2+ ) and Cocaine by Using Ligation DNAzyme Machinery

The Cu 2+ ‐dependent ligation DNAzyme is implemented as a biocatalyst for the colorimetric or chemiluminescence detection of Cu 2+ ions, Hg 2+ ions, or cocaine. These sensing platforms are based on the structural tailoring of the sequence of the Cu 2+ ‐dependent ligation DNAzyme for specific analytes. The tethering of a subunit of the hemin/G‐quadruplex DNAzyme to the ligation DNAzyme sequence, and the incorporation of an imidazole‐functionalized nucleic‐acid sequence, which acts as a co‐substrate for the ligation DNAzyme that is tethered to the complementary hemin/G‐quadruplex subunit. In the presence of different analytes, Cu 2+ ions, Hg 2+ ions, or cocaine, the pretailored Cu 2+ ‐dependent ligation DNAzyme sequence stimulates the respective ligation process by combining the imidazole‐functionalized co‐substrate with the ligation DNAzyme sequence. These reactions lead to the self‐assembly of stable hemin/G‐quadruplex DNAzyme nanostructures that enable the colorimetric analysis of the substrate through the DNAzyme‐catalyzed oxidation of 2,2′‐azinobis(3‐ethylbenzothiazoline‐6‐sulfonic acid), ABTS 2− , by H 2 O 2 into the colored product ABTS .− , or the chemiluminescence detection of the substrate through the DNAzyme‐catalyzed oxidation of luminol by H 2 O 2 . The detection limits for the sensing of Cu 2+ ions, Hg 2+ ions, and cocaine correspond to 1 n M , 10 n M and 2.5 μ M , respectively. These different sensing platforms also reveal impressive selectivities.