DNA-based amplified electrical bio-barcode assay for one-pot detection of two target DNAs

A sensitive label-free bio-barcode assay provided a PCR-free method for quantitative detection of two nucleic acid targets (HTLV-I and HTLV-II) simultaneously. This DNA biosensor was fabricated with two-component oligonucleotide-modified gold nanoparticles (AuNPs) and two-component oligonucleotide-modified magnetic beads (MBs), which can sandwich a specific target. After liberating the adsorbed thiolated barcode DNA strands (poly A and poly G) from the AuNPs surface with dithiothreitol (DTT) and acidic dipurinization, the electrochemical measurements were directly performed based on the redox activity of guanine (G) and adenine (A) nucleobases. Under the optimal assembling and detection conditions, a good linearity for simultaneous detection was obtained in the range from 4.4 × 10−11 to 2.0 × 10−9 M, and the detection limit (3σ) was estimated to be 1.71 × 10−12 M for T1-DNA and 1.55 × 10−12 M for T2-DNA.