在这里，我们巧妙地组装了一种巨型DNA纳米阵列，该纳米阵列由两种独立的四面体DNA结构组成，作为多臂三维（3D）DNA纳米机器的DNA轨道，以实现信号传导和放大的高效性能。我们将该纳米阵列改造为一种电化学生物传感器，用于快速和超灵敏地检测基质金属蛋白酶2（MMP-2）。令人印象深刻的是，与由二维（2D）探针或一维（1D）单链（ss）DNA探针组成的随机DNA轨道上低效的常规DNA行走器相比，多臂3D DNA纳米机器通过外切酶III（Exo III）酶辅助靶标循环放大，赋予了更快的反应速度和更高的行走效率，这是由于四面体DNA纳米阵列结构的良好刚性和有序性。一旦添加了携带信号物质二茂铁（Fc）的发夹H3-标签到改性电极表面，多臂3D DNA纳米机器将通过基于可组成DNA链替代的“补足域”介导而被驱动沿着精心设计的纳米阵列轨道移动，结果是大部分的二茂铁（Fc）与电极表面结合，并在60分钟内引起电化学信号的显著增加。作为概念验证，所制备的生物传感器在敏感检测目标MMP-2方面实现了低检测限（11.4 fg/mL），并在Hela和MCF-7癌细胞裂解液中进行了应用。因此，这种策略为肿瘤诊断中的蛋白质检测提供了高性能的传感平台。

Herein, a giant-sized DNA nanoarray was subtly assembled by two kinds of independent tetrahedral DNA structures as the DNA track for a multi-armed three-dimensional (3D) DNA nanomachine to perform signal transduction and amplification efficiently, which was developed as an electrochemical biosensor for the rapid and ultrasensitive detection of matrix metalloproteinase 2 (MMP-2). Impressively, in contrast to conventional DNA walkers with inefficiency, which walked on random DNA tracks composed of a two-dimensional (2D) probe or a one-dimensional (1D) single-stranded (ss)DNA probe, the multi-armed 3D DNA nanomachine from exonuclease III (Exo III) enzyme-assisted target recycling amplification would be endowed with faster reaction speed and better walking efficiency because of the excellent rigidity and orderliness of the tetrahedral DNA nanoarray structure. Once the hairpin H3-label with the signal substance ferrocene (Fc) was added to the modified electrode surface, the multi-armed 3D DNA nanomachine would be driven to move along the well-designed nanoarray tracks by toehold-mediated DNA strand displacement, resulting in most of the ferrocene (Fc) binding to the electrode surface and a remarkable increase in electrochemical signals within 60 min. As a proof of concept, the prepared biosensor attained a low detection limit of 11.4 fg/mL for the sensitive detection of the target MMP-2 and was applied in Hela and MCF-7 cancer cell lysates. As a result, this strategy provided a high-performance sensing platform for protein detection in tumor diagnosis.