3-D DNA walker-mediated ultrasensitive dual-signal biosensor for HIV DNA detection

Here, we successfully designed a dual-signal sensing system based on 3-D DNA walker signal amplification and target recycling amplification strategies for ultrasensitive determination of the human immunodeficiency virus（HIV）DNA. The DNA walker is constructed by locked swing arm and track strand onto the surface of the magnetic beads (MBs). After adding HIV DNA, the swing arm was activated to hybridize with the track strand to form ds-DNA, which could be cleaved by Exonuclease III (Exo III) to release G-quadruplex. Subsequently, hemin combined with G-quadruplex to construct DNAzymes, which catalyzed the oxidation of o-phenylenediamine (OPD) into the yellow product 2,3 diaminophenazine (DAP), resulting in the fluorescence quenching of MoS2 QDs at 420 nm, and the fluorescence enhancement of DAP at 560 nm. Therefore, the amounts of HIV DNA can be detected by Uv-vis absorbance and fluorescence dual-signal changes. Besides, each swing arm cleaved multiple track strands to amplify the signal, while the target recycling amplification was also in progress. Such double-amplified signal strategy not only provided excellent sensitivity and selectivity, but also realized magnetic separation, eliminating interferences in complex samples. In addition, our designed sensing platform can detect different DNAs by adjusting the recognition sequence, providing a general strategy for various virus analysis.