Aptamer functionalized gold nanoparticles based fluorescent probe for the detection of mercury (II) ion in aqueous solution

A method is proposed for the detection of Hg2+ using Hg2+ specific DNA (MSD) functionalized gold nanoparticles (AuNPs) based on the formation of T–Hg2+–T complex and the excellent quenching fluorescence property of AuNPs. The MSD is rich in thymine (T) and readily forms T–Hg2+–T configuration in the presence of Hg2+. The MSD which is labeled with a fluorescein (FAM) at the 3′-end and a thiol at the 5′-end is bounded to the AuNPs through Au–S covalent bonds to form the probes (AuNPs–MSD). Hg2+ detection can be easily realized by monitoring the change of fluorescence signal of AuNPs–MSD probes. Hg2+ can be detected in a range of 0.02–1.0 µM with a detection limit of 16 nM. Besides, the assay shows excellent selectivity for Hg2+ over other metal cations such as Fe3+, Ca2+, Mg2+, Mn2+, Cr3+, Ni2+, Cu2+, Co2+ and Pb2+. The major advantages of this Hg2+ assay are its water-solubility, simplicity, low cost and high sensitivity. Moreover, this method provides a potentially useful method for the Hg2+ detection in aqueous solution.