Electrochemical biosensor for silver ions based on amplification of DNA–Au bio–bar codes and silver enhancement

A highly sensitive and selective electrochemical DNA biosensor for detection of Ag + was developed based on amplification of DNA–Au bio–bar codes and silver enhancement. Cytosine-rich single stranded DNA oligonucleotide (sub–DNA) was immobilized on the surface of the gold electrode via Au–S chemical interaction. In the presence of Ag + , with the interaction of cytosine–Ag + –cytosine (C–Ag + –C), cytosine-rich DNA oligonucleotide probes-labeled AuNPs have a hybridization with sub–DNA and then form a duplex-like structure, following the AuNPs-catalyzed silver enhancement. The whole detection procedure of Ag + based on the developed biosensor was evaluated by electrochemical techniques. Owing to the hybridization of sandwich assay format and distinct electrochemical signal amplification of silver enhancement, the proposed biosensors exhibited a good analytical performance for sensitive transduction of Ag + recognition with a wide detection linear range from 5 pM to 50 μM, and a low detection limit of 2 pM. The developed biosensor was highly selective and its practical applicability in real water samples was also tested with satisfactory results.