Electrochemiluminescence biosensor based on a 3D DNA walking nanomachine with a powerful payload capacity

Herein, we constructed a three-dimensional (3D) DNA walking nanomachine, just built from Watson-Crick base pairing, which had large payload capacity by using a functionalized DNA nanotube (NT) as track and was further applied to sensitive electrochemiluminescence (ECL) assay of biomarker. The NT as 3D track was composed of a long backbone chain, a triangular fixation unit (U-B) and abundant triangular rung units (U-A) that arranged along the backbone. Every U-A with three footholds could immobilize three ECL emitter (ABEI) labeled-DNA-stators, so this track exhibited a powerful payload capacity on a planar surface compared to that of the existing 1D and 2D DNA walking nanomachines due to the formation of a linear array from U-A. Moreover, an amplification strategy made tiny amounts of HIV DNA transform into numerous walkers, which then hybridized with DNA-stator chains. In the presence of Mg2+, the DNA walker initiated moving along the 3D nanotube track, causing a reduce of ECL signal intensity owing to the release of ABEI from the biosensing surface to achieve the assay for HIV DNA with a detection limit of 0.82 fM. Such a strategy and subsequent application for biosensing develop an effective signal amplification 3D DNA walking nanomachine for sensing assay.