posted on 2017-01-12, 00:00authored byPeng Miao, Yuguo Tang, Lei Wang
Driven
by the urgent need to detect trace heavy metal ions in various real
water samples, this article demonstrates for the first time an electrochemical
biosensor based on DNA modified Fe3O4@Au magnetic
nanoparticles (NPs). Three DNA probes are designed to contain certain
mismatched base pairs. One is thiolated and modified on the surface
of Fe3O4@Au NPs (DNA 1). The other two probes
(DNA 2 and 3) are labeled with two independent electrochemical species.
Stable structures of cytosine–Ag+–cytosine
and thymine–Hg2+–thymine formed in the presence
of Ag+ and Hg2+ can assist the hybridization
of DNA 1/DNA 2 and DNA 1/DNA 3, which locate corresponding electrochemical
species onto the surface of the magnetic NPs. The achieved nanocomposites
are then used as selective electrochemical probes for the detection
of heavy metal ions by recording the square wave voltammetry signals.
Simultaneous detection of Ag+ and Hg2+ is demonstrated
without significant interference, and their individual high sensitivities
are fundamentally preserved, which meet the requirements of U.S. Environmental
Protection Agency (USEPA). Furthermore, the proposed method has been
challenged by various real water samples. The results confirm the
DNA modified magnetic NPs based sensing method may have potential
applications for the monitoring of heavy metal ions in real sample
analysis.