Sensitive DNA detection using cascade amplification strategy based on conjugated polyelectrolytes and hybridization chain reaction

In this paper, a novel homogeneous hybridization chain reaction (HCR) assay is developed by using cationic conjugated polyelectrolytes (CPEs) as an indicator for the detection of DNA. In this assay, two hairpin probes H1 and H2 are labeled with fluorescein at their 5'-end and 3'-end respectively. After the HCR, the two hairpin probes are triggered by target DNA to form a long two-stranded DNA polymer with numerous fluorescein labelling in the strand, which is resistant to the S1 nuclease degradation. When the CPEs are added, strong electrostatic interaction between fluorescein-labeled DNA and CPEs occurred, which allowed fluorescence resonance energy transfer (FRET) from the CPEs to the fluorescein-labeled DNA and an obvious fluorescence colour change of the conjugated polymer solution. With HCR amplification and CPEs to amplify the fluorescence signal, homogeneous HCR for sensitive DNA detection is performed successfully. This proposed cascade amplification strategy can not only extend the application of HCR but also provides an alternative platform for homogeneous detection of DNA.