▎ 摘　　要

A label-free ratiometric electrochemical DNA sensing strategy was established by simultaneously adopting the self-redox signal of electrode interface and signal of electrochemical indicator as ratio metric signals together. The sodium salt of flavin mononucleotide (FMNs)/reduced graphene oxide(rGO) nanocomposite was prepared by simple ultrasonication method. The obtained FMNs/rGO possesses high water dispersion and good electrochemical redox signal. FMNs/rGO was further applied as the electrode modification material to immobilize DNA probe and provide the self-redox signal for DNA detection, while the electrochemical indicator Meldola's Blue (MDB) was served as another detection signal. With the increase of target DNA concentration, the self-redox signal of the FMNs/rGO would decrease due to the formation of more DNA duplex, while more MDB would combine with the DNA duplex and resulted in higher signal of MDB. By measuring the ratios of the two signals, this novel ratiometric strategy effectively improved the reproducibility and reliability while avoided using expensive and complicated redox labels on DNA. (C) 2018 Elsevier B.V. All rights reserved.