Ultrasensitive electrochemical DNA detection based on dual amplification of circular strand-displacement polymerase reaction and hybridization chain reaction

•An electrochemical biosensor for DNA detection was developed.•Dual signal amplification was achieved by combining CSDPR and HCR.•DNA was detected sensitively and selectively.•The biosensor worked well in complex biological samples.

We developed a novel electrochemical strategy for ultrasensitive DNA detection using a dual amplification strategy based on the circular strand-displacement polymerase reaction (CSDPR) and the hybridization chain reaction (HCR). In this assay, hybridization of hairpin-shaped capture DNA to target DNA resulted in a conformational change of the capture DNA with a concomitant exposure of its stem. The primer was then hybridized with the exposed stem and triggered a polymerization reaction, allowing a cyclic reaction comprising release of target DNA, hybridization of target with remaining capture DNA, polymerization initiated by the primer. Furthermore, the free part of the primer propagated a chain reaction of hybridization events between two DNA hairpin probes with biotin labels, enabling an electrochemical reading using the streptavidin-alkaline phosphatase. The proposed biosensor showed to have very high sensitivity and selectivity with a dynamic response range through 10 fM to 1 nM, and the detect limit was as low as 8 fM. The proposed strategy could have the potential for molecular diagnostics in complex biological systems.