An 'on-off' electrochemiluminescence biosensor based on DNA nanotweezer probe coupled with tripod capture DNA for high sensitive detection of Pb~(2+)

摘要

In this work, a new DNA nanotweezers-Ag nanoparticle (NP) as signal-switching probe is designed and coupled with tripod-like capture DNA structure to construct an ultrasensitive "ON-OFF" electrochemiluminescence (ECL) biosensor for detecting Pb~(2+). The unique tweezer nanostructure has two G-base-rich sequences on different arms, and the G4-chain structure is simply constructed by switching tweezer conformation from "open" to "close", which can be controlled by alternative target released in Pb~(2+)-triggered cyclic amplification process. The activated G4-structure can specifically capture plenty of hemin to the closed state, which has a strong quenching effect on ECL of Ru(phen)_3~(2-). After reduced graphene oxide (ERGO) with good electrochemical activity and loading capacity is electrodeposited on the electrode, Ru(phen)_3~(2-) as ECL probe is strongly adsorbed on it via π-π conjugation. Then tripod-like DNA structure with spiral extensibility, good capabilities, and no backfilling was linked to the surface to capture G4-structure with hemin, resulting in significant decrease of ECL for sensitive Pb~(2+) detection. Due to the design flexibility of DNA nanotweezers structure, the strategy provides universal design of ECL biosensors in ingenious assay of a variety of metal ions and other bioassays.