Ultrasensitive electrochemical biosensor for silver ion based on magnetic nanoparticles labeling with hybridization chain reaction amplification strategy

• DOI: 10.1016/j.snb.2017.04.108
• Publication Date: 2017-04-21T14:15:28Z
• Authors: Yanli Zhang; Haiyan Li; Meng Chen; Xiang Fang; Pengfei Pang; Hongbin Wang; Zhan Wu; Wenrong Yang
• Keywords: 01 natural sciences; 6. Clean water; 3. Good health; 0104 chemical sciences

Abstract Silver ion (Ag+) is a highly toxic heavy metal ion to aquatic organisms and accumulates in the human body via the food chain. Therefore, fast and accurate detection of Ag+ in water and food resources has become a critical issue within the scope of human health. Herein, we developed an ultrasensitive electrochemical biosensor for detection of Ag+ based on magnetic Fe3O4@gold core-shell nanoparticles (Fe3O4@Au NPs) labeling with hybridization chain reaction (HCR) amplification strategy. In this sensing strategy, the magnetic Fe3O4@Au NPs were selected for labeling with HCR product and enrichment on the surface of magnetic gold electrode. Thiolated-oligonucleotide (S1) was firstly immobilized on the surface of Fe3O4@Au NPs through Au–S chemical bond. In the presence of Ag+, cytosine-rich DNA oligonucleotide S2 hybridized with S1 to form an intramolecular duplex, in which Ag+ can selectively bind to cytosine–cytosine mismatches forming C–Ag+–C complex. The exposed stem of the C–Ag+–C complex opened two alternating ferrocene-labeled DNA hairpins (H1 and H2) in turn and triggered HCR to form a supersandwich DNA structure on the surface of Fe3O4@Au NPs. The HCR products modified Fe3O4@Au NPs were brought to the surface of magnetic gold electrode for direct electrochemical measurements. The proposed strategy led to a low detection limit of 0.5 fM and a wide dynamic range of 1 fM–100 pM for target Ag+. The developed biosensor was highly selective and its practical applicability in tap water and lake water samples was also investigated with a satisfactory result.