Herein, we proposed an enzyme-free strategy for the amplified detection of DNA by combining the efficient fluorescence enhancement capability of a â-cyclodextrin-tethered cationic polymer (cationic polyâ-CD) to pyrene with the amplification capability of target DNA triggered hybridization chain reaction (HCR). Cationic polyâ-CD with positive charge was synthesized. Two hairpin probes, H1 and H2, were employed in the system and the pyrene-labelled H2 was chosen as the signal unit. The pyrene attached on the sticky end of H2 was flexible and there was strong electrostatic interaction between cationic polyâ-CD and negatively-charged H2, so pyrene could easily enter the cavity of CD that is tethered on the cationic polymer, accompanied by significant fluorescence enhancement. Once target DNA was introduced, HCR was triggered to form a rigid long dsDNA polymer with pyrene attached on it. The pyrene was hardly able to enter the cavity of cationic polyâ-CD because of steric hindrance, leading to a weak fluorescent signal. Owing to the efficient pyrene fluorescence enhancement of cationic polyâ-CD and the amplified capability of HCR, an enzyme-free sensitive detection of target DNA was achieved with a detection limit of 0.1 nM and high selectivity.
DNA Limit of Detection