A graphene oxide-based enzyme-free signal amplification platform for homogeneous DNA detection

A graphene oxide (GO) based enzyme-free signal amplification platform for homogeneous DNA sensing is developed with simplicity and high sensitivity. In the absence of the target DNA, labeled hairpin probe 1 (H1) and probe 2 (H2) were adsorbed on the surface of GO, resulting in the fluorescence quenching of the dyes and minimizing the background fluorescence. The addition of the target DNA facilitated the formation of double-stranded DNA (dsDNA) between H1 and H2, causing the probes to separate from GO and release the target DNA through a strand displacement reaction. Meanwhile, the whole reaction started anew. This is an excellent isothermal signal amplification technique without the involvement of enzymes. By monitoring the change of the fluorescence intensity, the target DNA not only can be determined in buffer solution, but also can be detected in 1% serum solution spiked with a series of concentrations of the target DNA. In addition, the consumption amount of the probes in this method is lower than that in traditional molecular beacon methods.