Department of Biochemistry and Molecular Biology, Shanxi Medical University, Taiyuan 030001, P. R. China.
Analyst. 2019 Mar 11;144(6):1982-1987. doi: 10.1039/c8an02308e.
In this paper, by taking advantage of the fact that silver ions could mediate the Mg2+-dependent DNAzyme (Mgzyme) activity, we for the first time developed a turn-on fluorescent biosensor for amplified cysteine (Cys) detection. Because Mgzyme can interact with the silver ion and form cytosine-Ag+-cytosine (C-Ag+-C) base pairs, the conformation of its catalytic core was changed. As a result, the catalytic activity of Mgzyme was suppressed and the Mgzyme-Ag+ complex could not initiate the cleavage reaction. Therefore, the background fluorescence of the biosensor was very low. In the presence of Cys, Cys can bind tightly to the silver ion and disrupt the C-Ag+-C base pairs in the Mgzyme-Ag+ complex, leading to the restoration of Mgzyme activity. The activated Mgzyme could hybridize with the MB substrate and undergo many cleavage cycles, resulting in a significant increase of fluorescence intensity. This designed strategy provided amplified fluorescence detection of cysteine, with a detection limit of 2 nM. Moreover, the strong binding between Cys and Ag+ ensured that the biosensor had a desirable selectivity for Cys. This sensing system was also used to detect Cys in human urine samples and displayed satisfying results.
本文利用银离子能介导 Mg2+-依赖的 DNA 酶（Mgzyme）活性的事实，首次开发了一种用于放大半胱氨酸（Cys）检测的荧光开启型生物传感器。由于 Mgzyme 可以与银离子相互作用并形成胞嘧啶-银+-胞嘧啶（C-Ag+-C）碱基对，其催化核心的构象发生改变。结果，Mgzyme 的催化活性受到抑制，并且 Mgzyme-Ag+ 复合物不能引发切割反应。因此，生物传感器的背景荧光非常低。在存在 Cys 的情况下，Cys 可以与银离子紧密结合并破坏 Mgzyme-Ag+ 复合物中的 C-Ag+-C 碱基对，导致 Mgzyme 活性的恢复。激活的 Mgzyme 可以与 MB 底物杂交，并经历多次切割循环，导致荧光强度显著增加。该设计策略提供了对半胱氨酸的放大荧光检测，检测限为 2 nM。此外，Cys 和 Ag+ 之间的强结合确保了该生物传感器对半胱氨酸具有理想的选择性。该传感系统还用于检测人尿样中的半胱氨酸，结果令人满意。
