Colorimetric and visual mercury(II) assay based on target-induced cyclic enzymatic amplification, thymine-Hg(II)-thymine interaction, and aggregation of gold nanoparticles.

A colorimetric biosensor and visual test is described for the determination of mercury(II). It relies on the specific thymine-Hg(II)-thymine (T-Hg2+-T) interaction which induces a cyclic amplification process (caused by the enzyme exonuclease III) and the aggregation of gold nanoparticles. These results in a color change from red to violet. Under optimized conditions, this colorimetric assay (best performed at 524 nm) has a detection limit as low as 0.9 nM with a detection range over 4 orders of magnitude (from 1 nM to 10 μM). Graphical abstract Schematic of a colorimetric method for determination of mercury ions (Hg2+) based on the thymine-Hg2+-thymine interaction-triggered cyclic enzymatic amplification and aggregation of gold nanoparticles with the aid of exonuclease III (Exo III).