Coupling of a reagentless electrochemical DNA biosensor with conducting polymer film and nanocomposite as matrices for the detection of the HIV DNA sequences

This paper describes a reagentless electrochemical DNA biosensor applied to the detection of human immunodeficiency virus (HIV) sequences based on electrochemical impedance spectroscopy (EIS). The novel DNA biosensor has been elaborated by means of an opposite-charged adsorption Au-Ag nanocomposite to a conductive polymer polypyrrole (PPy) modified platinum electrode (Pt) and self-assembly the mercapto oligonucleotide probes onto the surface of modified electrode via the nanocomposite. The duplex formation was detected by measuring the electrochemical impedance signal of nucleic acids in phosphate buffer solution (PBS). Such response is based on the concomitant conductivity changes of the PPy film and nanocomposite. The reagentless scheme has been characterised using 21-mer synthetic oligonucleotides as models: parameters affecting the hybridization assay were explored and optimized. The detection limit is 5.0x10(-10) M of target oligonucleotides at 3 sigma. The potential for development of reagentless DNA hybridization analysis in the clinical diagnosis is being pursued.