A facile and sensitive electrochemiluminescence biosensor for Hg2+ analysis based on a dual-function oligonucleotide probe

In this study, a sensitive electrochemiluminescent (ECL) biosensor for the detection of Hg2+ was easily prepared by self-assembling mercury-specific oligonucleotide on the surface of gold nanoparticles (AuNPs) modified indium tin oxide (ITO) electrode. A conformation change of the oligonucleotide from linear chain to hairpin occurs upon the binding of Hg2+ through thymine-Hg2+-thymine coordination. The dual-function oligonucleotide serves as the probe to Hg2+ but also a carrier of signal-generating molecules, [Ru(bpy)(2)(dppz)](BF4)(2). It was estimated that one oligonucleotide was able to load with eight ECL signal molecules; a ratio of four or five oligonucleotides per gold nanoparticle was obtained basing on the calculation with surface density. Without tedious multiple-labeling procedures and special modification of oligonucleotide probe for signal transduction/amplification, a detection limit of 5.1 pM Hg2+ was outstanding from the interference of other ten metal ions. Results of spiked water samples were in good agreement with that obtained by atomic fluorescent spectrometry. (C) 2015 Elsevier B.V. All rights reserved.