Selective detection of silver ions using mushroom-like polyaniline and gold nanoparticle nanocomposite-based electrochemical DNA sensor

A highly sensitive electrochemical DNA biosensor made of polyaniline (PANI) and gold nanoparticles (AuNPs) nanocomposite (AuNPs@PANI) has been used for the detection of trace concentration of Ag+. In the presence of Ag+, with the interaction of cytosine-Ag+-cytosine (C-Ag+-C), cytosine-rich DNA sequence immobilized onto the surface of AuNPs@PANI has a self-hybridization and then forms a duplex-like structure. The whole detection procedure of Ag+ based on the developed biosensor was evaluated by electrochemical impedance spectroscopy. On semi-logarithmic plots of the log Ag+ concentration versus peak current, the results show that the prepared biosensor can detect silver ions at a wide linear range of 0.01-100 nM (R = 0.9828) with a detection limit of 10 pM (signal/noise = 3). Moreover, the fabricated sensor exhibits good selectivity and repeatability. The detection of Ag+ was determined by Ag+ self-induced conformational change of DNA scaffold that involved only one oligonucleotide, showing its convenience and availability.