Abstract
We reported a sensitive surface plasmon resonance (SPR) sensor for the detection of Hg 2+ in aqueous solution by using a thymine (T)-rich, mercury-specific oligonucleotide (MSO) probe and gold nanoparticles (Au NPs)-based signal amplification. The MSO probe was first immobilized on gold film through formation of Au–S bond between DNA and gold film. In the presence of Hg 2+, the MSO probe captured free Hg 2+ in aqueous media via the Hg 2+-mediated coordination of T–Hg 2+–T base pairs. This direct immobilization strategy led to a detection limit of 0.3 μM of Hg 2+. In order to improve the sensitivity, part complementary DNA (PCS)-modified Au NPs labels were employed to amplify SPR signals. We demonstrated that this Au NPs-based sensing strategy resulted in a detection limit down to 5 nM of Hg 2+, brings about an amplification factor of two orders of magnitude. This Au NPs-based Hg 2+ sensor also exhibited excellent selectivity over a spectrum of interference metal ions. Taking advantage of the high amplifying characteristic of Au NPs and the specificity of MSO to Hg 2+ recognition, we developed here a SPR sensor for specific Hg 2+ detection with high sensitivity.
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