Gold Nanoparticle-Based Dynamic Light Scattering Assay for Mercury Ion Detection

A gold nanoparticle (GNP)-based dynamic light scattering (DLS) assay has been developed for detecting mercury ion (Hg2+) in aqueous solution. The GNPs were able to maintain monodisperse state in relative high ionic strength (0.1 M NaCl) aqueous solution because Hg2+ aptamer 5′-TTTCTTCTTTCTTCCCCCCTTGTTTGTTGTTT-3′ (probe DNA) could adsorb on the GNP surface by electrostatic interaction. In the presence of Hg2+, the probe DNA molecules were easily desorbed from GNP surface because of T-Hg2+-T formation. The unprotected GNPs form aggregates in 100 mM NaCl solution, resulting in increased significantly the average hydrodynamic diameter of GNPs. Under the conditions of pH 7.43, 110 nM aptamer, 100 mM NaCl and 30 min incubation time of Hg2+ with aptamer, the difference of average hydrodynamic diameter (ΔD) of GNPs was increased linearly with logarithm of Hg2+ concentration over the range from 0.1 nM to 5 μM, with a detection limit of 0.1 nM. Moreover, satisfactory results were obtained when the proposed method was applied to detect Hg2+ in real samples.

In the absence of the target, GNPs can maintain monodisperse state under the high ionic strength due to the absorption of the probe DNA could adsorb on GNP surface by electrostatic attraction. After reacted with Hg2+, the formation of T-Hg2+-T complex resulted in the DNA departing from GNPs surface. Under the high ionic strength, the unprotected GNPs form aggregates lead to an increase in hydrodynamic diameter of GNPs from D0 to D.Figure optionsDownload as PowerPoint slide