A magnetic separated-type ultrasensitive fluorescent DNA biosensor based on hydrogen peroxide triggered chemically driven redox-cycling system

In order to meet the demand of analyzing low concentrations of DNA with high sensitivity, herein, a magnetic separated-type fluorescent biosensor has been constructed for ultrasensitive DNA assay based on chemically driven redox-cycling system. In this study, the substrate o-phenylenediamine dihydrochlorlde (OPD) could be oxidized to produce 2, 3-diaminophenazine (DAP) with strong fluorescence emission at 555 nm. In the chemically driven redox-cycling system, Cu2+ oxidized OPD to yield DAP and Cu+/Cu0. On one hand, the produced Cu0 could further oxidize OPD to form DAP. But on the other, the generated Cu+ could react with newly imported H2O2 to undergo a Fenton-like reaction to form hydroxyl radicals (•OH) and Cu2+ ion. The reproduced Cu2+ ion and generated •OH could in turn oxidize OPD to form more DAP, which touching off a chemically driven chemical redox-cycling amplification reaction. By leveraging of the magnetic separation-mode, the chemically driven redox-cycling strategy allowed quantitative detection of H1N1, exhibiting a linear ranging from 1 pM to 1 nM with a low limit of detection of 300 fM. The magnetic separation-mode could effectively minimize the background signal to obtain greatly improved sensitivity. It’s promising that the chemically driven redox-cycling strategy would provide a novel way in the fields of biosensing and biological samples assay.