A dual-colorimetric signal strategy for DNA detection based on graphene and DNAzyme

In this work, by employing graphene together with a peroxidase-mimic DNAzyme, we have developed a novel dual-colorimetric strategy for DNA detection. In this strategy, a bi-functional probe DNA with both the sequence to have peroxidase activity and the sequence to be complementary to the target DNA is designed. Through pi-pi stacking, the probe DNA can interact with graphene; however, when the target DNA is present, the graphene-probe DNA interaction will be interrupted, resulting in the peroxidase activity being transferred from the precipitated graphene to the supernatant under centrifugation. Consequently, colorimetric signals can be obtained due to the catalytic reactions by the formed peroxidase-mimic DNAzyme. By observing the changes of the color depth of either the precipitate or the supernate, we are able to detect the target DNA very easily and sensitively with the naked eye. The dual colorimetric signals (signal-off for the precipitate and signal-on for the supernate) can also be integrated through mathematical operations, which may greatly improve the performance of the sensing platform.