3D DNA nanosphere-based photoelectrochemical biosensor combined with multiple enzyme-free amplification for ultrasensitive detection of cancer biomarkers

In this work, a new 3D DNA nanosphere was ingeniously designed and fabricated, which was used to combine with multiple enzyme-free amplification strategy to develop a photoelectrochemical (PEC) biosensing platform for ultrasensitive detection of carcinoembryonic antigen (CEA). The 3D DNA nanostructure was self-assembled by base complementary pairing in a few minutes and rolling circle amplification (RCA) reaction. The intense photocurrent derived from Au NPs/ZnSe QDs can be effectively decreased by 3D DNA nanospheres assembled on the electrode, making photoelectric signal present "off" state. The specific binding of target CEA with its hairpin (HP1) aptamer opens HP1 structure, which initiated multiple enzyme-free strand displacement amplification (SDA) reaction and generated a large number of single strands DNA SI. Then S1 competitively binds to capture DNA on the electrode to release 3D DNA nanospheres, thus the photocurrent signal became "on" state for achieving amplified assay of target CEA. The proposed PEC biosensor exhibits excellent performance with a wide linear range of 1.0 fg/mL to 10 ng/mL and a low detection limit of 0.12 fg/mL for CEA, which was successfully applied for the assay of real serum samples with good precision. The reported strategy opens a new simple way for PEC biosensor using DNA nanostructure, showing huge potential in clinical application research.

在这项工作中，巧妙地设计并构建了一种新型的三维DNA纳米球，它与多重无酶扩增策略相结合，开发了一种用于癌胚抗原（CEA）超灵敏检测的光电化学（PEC）生物传感平台。这种三维DNA纳米结构是通过碱基互补配对以及滚环扩增（RCA）反应在几分钟内自组装而成的。金纳米粒子/硒化锌量子点产生的强光电流可被组装在电极上的三维DNA纳米球有效降低，使光电信号呈现“关闭”状态。目标CEA与其发夹（HP1）适体的特异性结合打开了HP1结构，从而引发多重无酶链置换扩增（SDA）反应，并产生大量单链DNA S1。然后S1竞争性地与电极上的捕获DNA结合，释放三维DNA纳米球，从而使光电流信号变为“开启”状态，以实现对目标CEA的放大检测。所提出的PEC生物传感器表现出优异的性能，对CEA的检测线性范围为1.0飞克/毫升至10纳克/毫升，检测下限低至0.12飞克/毫升，并成功应用于实际血清样本的检测，具有良好的精密度。所报道的策略为利用DNA纳米结构的PEC生物传感器开辟了一种新的简便途径，在临床应用研究中显示出巨大的潜力。