An electrochemical biosensor for DNA detection based on tungsten disulfide/multi-walled carbon nanotube composites and hybridization chain reaction amplification

We report the preparation and characterization of tungsten disulfide-multi-walled carbon nanotubes (WS2-MWCNTs) composite via a simple hydrothermal process and demonstrate its application as a biosensing platform for ultrasensitive determination of hepatitis B virus genomic DNA coupled with hybridization chain reaction (HCR) signal amplification. The sensing platform includes capture DNA probe (cDNA), auxiliary DNA, two DNA hairpins, and detection signal is amplified by horse radish peroxidase (HRP) on the DNA duplex. The biosensor is fabricated with the cDNA labeled at 3′ end using thiol immobilized on the WS2-MWCNTs/Au nanoparticels modified electrode. cDNA fixed onto electrode surface then reacts with target DNA through the 3′ end of auxiliary DNA. The remaining segment on 5′ end of auxiliary DNA then takes turns to open two alternating DNA hairpins. This leads to a HCR events to produce a nicked double-helix. A large amount of HRP is then combined on DNA helix by affinity interaction of biotin-avidin, each of which amplifies the final electrochemical signal through the catalytic reaction of H2O2 and hydroquinol. Under optimal conditions, a dynamic range of 10 fM-0.1 nM is obtained with a detection limit of 2.5 fM. Synergistic effect of WS2-MWCNTs composite and HCR have proven to greatly improve sensitivity for DNA detection.