A simple and sensitive DNAzyme-based colorimetric sensor for detecting Hg 2+ based on T–Hg 2+ -T base pair and magnetic beads (MBs) is proposed. In the presence of Hg 2+ , capture probes (CPs) immobilized on MBs are hybridized with the signal probes (SPs) consisting of G-quadruplex sequences with the help of T–Hg 2+ -T base pairs. The SPs are separated by MBs and used to bind hemin for the formation of catalytically active hemin/G-quadruplex DNAzymes, which catalyzes the H 2 O 2 -mediated oxidation of ABTS to produce a blue-green-colored product. A linear relationship between the absorbance and Hg 2+ concentration is observed over a range of 10–200 nM with a limit of detection 5 nM. Taking advantage of MBs separation/collection process, the sensing system can be regenerated by using EDTA as the chelator.
We demonstrated a sensitive method for detection of glutathione (GSH) based on LSPR scattering spectrum using gold core-satellite nanostructure linked by T-Hg 2+ -T base pair . The core-satellite assembly caused coupling between plasmonic nanoparticles , which inducing distinct change of LSPR peak wavelength. As the interaction between Hg 2+ and GSH, the core-satellite nanostructure would be disassembled, which accompanied with spectral blue-shift of the scattering spectrum. By using this method, GSH could be quantitatively detected, and the detection limits can reach to 0.1 µM.
An amplified colorimetric detection of Hg 2+ is proposed by combining T–Hg 2+ –T base pairs and hybridization chain reaction (HCR). Two hairpins consisting of three-fourths and one-fourth of the horseradish peroxidase (HRP)-mimicking DNAzyme in inactive configuration are used as functional elements. In the presence of Hg 2+ , one of the hairpins is opened by an assistant probe with the help of T–Hg 2+ –T base pairs and this triggers an autonomous cross-opening of the two hairpins using the strand displacement principle, resulting in the formation of DNA nanowires consisting of numerous reunited Q-quadruplex DNAzyme units. The resulting catalytically active hemin/G-quadruplex HRP-mimicking DNAzymes catalyze the oxidation of ABTS 2− by H 2 O 2 into a green-colored cationic radical ABTS •+ for the colorimetric readout. This “turn-on” sensing system enables the high sensitive and selective detection of aqueous Hg 2+ with a detection limit of 9.7 pM.
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