Target-induced formation of gold amalgamation on DNA-based sensing platform for electrochemical monitoring of mercury ion coupling with cycling signal amplification strategy

• We report a new electrochemical sensing protocol for the detection of mercury ion.
• Gold amalgamation on DNA-based sensing platform was used as nanocatalyst.
• The signal was amplified by cycling signal amplification strategy.

Heavy metal ion pollution poses severe risks in human health and environmental pollutant, because of the likelihood of bioaccumulation and toxicity. Driven by the requirement to monitor trace-level mercury ion (Hg2+), herein we construct a new DNA-based sensor for sensitive electrochemical monitoring of Hg2+ by coupling target-induced formation of gold amalgamation on DNA-based sensing platform with gold amalgamation-catalyzed cycling signal amplification strategy. The sensor was simply prepared by covalent conjugation of aminated poly-T(25) oligonucleotide onto the glassy carbon electrode by typical carbodiimide coupling. Upon introduction of target analyte, Hg2+ ion was intercalated into the DNA polyion complex membrane based on T–Hg2+–T coordination chemistry. The chelated Hg2+ ion could induce the formation of gold amalgamation, which could catalyze the p-nitrophenol with the aid of NaBH4 and Ru(NH3)63+ for cycling signal amplification. Experimental results indicated that the electronic signal of our system increased with the increasing Hg2+ level in the sample, and has a detection limit of 0.02 nM with a dynamic range of up to 1000 nM Hg2+. The strategy afforded exquisite selectivity for Hg2+ against other environmentally related metal ions. In addition, the methodology was evaluated for the analysis of Hg2+ in spiked tap-water samples, and the recovery was 87.9–113.8%.

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