Oligonucleotide-Based Reusable Electrochemical Silver(I) Sensor and Its Optimization via Probe Packing Density

Abstract

We report herein a selective, sensitive, and reusable electrochemical sensor for the detection of silver(I) ions. This sensor detects Ag + through a structure-switching electrode-bound DNA by measuring the changes in the electron-transfer efficiency. A single-stranded DNA, featuring a methylene blue (MB)-tagged DNA hairpin structure, strategically provides selective binding for the silver-mediated coordination of cytosine–Ag + –cytosine complexes. The DNA-modified electrode produces a change in the electrochemical signal due to the redox current of the surface-confined MB tag. The “turn-on” signaling upon silver(I) ion binding could be attributed to a conformational change in the MB-tagged DNA from an open structure to a target-induced folding structure. Differential pulse voltammetry of the DNA-modified electrode showed that the MB reduction signal increased linearly with an increase in Ag + concentrations in a range of 10–200 nM, with a detection limit of 10 nM. The structure-switching silver(I) ion sensor was amenable to regeneration by simply unfolding the electrode-bound MB-tagged DNA in 100 mM ethylenediaminetetraacetic acid, and it could be regenerated with no loss in signal gain upon subsequent silver(I) ion binding. We also demonstrated that by controlling the probe packing density on the electrode surface, the fabrication parameters can be varied to achieve optimal sensor performance.

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“…3 B, the system with the highly modified SCGS showed the lowest signal gain, 738, the loosely modified SCGS showed 1586%, and mediumly modified SCGS showed the highest signal gain, 3209, which might be due to the conformation of the oligonucleotide. The oligonucleotide modified with high concentration can occur a 'standing-up' conformation on the surface of the substrate [37] , [38] . Speculatively, for the proposed DNA walker, the oligonucleotide highly modified on the SCGS kept a 'standing-up' conformation (Fig.…”

Recent Achievements in Electrochemical and Optical Nucleic Acids Based Detection of Metal Ions

“…The next example of electrochemical detection of silver ions is a ssDNA oligonucleotide-based sensor proposed by Kim [ 74 ]. The presence of Ag + influences the conformation of the DNA strand and thus changes the electron transfer efficiency.…”

Cytosine-Rich Oligonucleotide and Electrochemically Reduced Graphene Oxide Nanocomposite for Ultrasensitive Electrochemical Ag+ Sensing

“…Previously, Prof. Han's group suggested that aptasensors detect silver ions via probe packing density [57]. Their approach involved the use of cytosine-rich oligonucleotides (CRO) tagged with methylene blue, which were self-assembled onto the gold electrode surface via thiol groups from the aptamer's 5 ′ -terminal.…”