Homogenous fluorescence polarization assay for the DNA of HIV A T7 by exploiting exonuclease-assisted quadratic recycling amplification and the strong interaction between graphene oxide and ssDNA

The authors describe a fluorescence polarization (FP) based strategy for HIV detection. The assay is based on T7 exonuclease assisted quadratic recycling amplification using graphene oxide (GO) as an amplifier of FP. The effect is caused by the finding that the binding forces between GO and ssDNA are much stronger than those between GO and dsDNA. The two probes, P1 and dye labeled P2, resist digestion by T7 exonuclease (T7exo) due to the 5'-termini protrusion. The hairpin probes are absorbed on the surface of GO without the target DNA. While the presence of the target DNA leads to two independent and simultaneous recycling processes with the assistance of T7exo. Due to this quadratic amplification, a large quantity of ssDNA will be absorbed onto the surface of GO, and this will cause a strong enhancement of FP. This polarization assay was applied to design a method for the determination of HIV DNAwhich displays a detection limit of 9.12 pmol.L-1. It is highly selective and can be performed in homogeneous solutions. The cascade amplification strategy is not limited to this particular DNA but is perceived to provide a universal platform for sensitive determination of a wide spectrum of DNA target analytes.