An Efficient Electrochemical Biosensor for Silver Ion Detection Using Hydrogen Peroxide as a Redox Indicator

摘要

The strong and specific binding of two DNA cytosine bases by silver ion (C-Ag~+-C) was applied to develop an efficient electrochemical biosensor for the detection of silver ion in aqueous solution. As a redox indicator, the hydrogen peroxide worked to generate a readable electrochemical signal. Thiolated short oligonucleotide strands containing 5 cytosine bases served as probe and self-assembled via Au–S bonding on gold electrode. In the presence of Ag~+, the specific coordination between Ag~+ and cytosine bases resulted in more stable and porous arrangement of oligonucleotide strands. Hydrogen peroxide could adsorb onto the surface of gold electrode and produce an electrochemical signal. The cyclic voltammetry shows a linear correlation between the signal and the concentration of Ag~+ over the range 0-0.2 μM (R~2 = 0.9955) with a detection limit of 30 nM. The length of probe DNA has no significant impact on the sensor performance. This biosensor is simple, economical and reusable with good sensitivity and selectivity. We also validated the practicality for the determination of Ag+ in real water samples.