Institute of Materials, China Academy of Engineering Physics, Mianyang, 621900, China.
Analyst. 2022 Sep 12;147(18):4158-4166. doi: 10.1039/d2an01038k.
This work presents a rapid and highly sensitive colorimetric assay using bifunctional DNA probe decorated agarose microbeads (MBs) coupled with a cascade signal amplification system, including rolling circle amplification (RCA) and the hemin/G-quadruplex-catalyzed colorimetric reaction, for visualized detection of uranyl ions. The DNA probe integrates the UO-specific DNAzyme/substrate as the target recognition unit and a DNA primer as the signal conversion unit. The presence of uranyl ions induces the efficient cleavage of the DNA substrates with the catalysis of DNAzyme. Then the conjugated primers are released from MBs, initiating the RCA reaction (the first amplification). The RCA product consists of repetitive G-quadruplexes that can lead to a second amplification by catalyzing the oxidation of ABTS with hemin binding, resulting in a coloration that is visible to the naked eye. The whole assay procedure could be finished within 40 min, including recognition of uranyl and DNA cleavage (5 min), the RCA reaction (30 min) and data readout either by eye or using a UV-vis spectrometer (5 min for each sample). In the optimal conditions, concentrations as low as 5 nM uranyl ions could be distinguished by the naked eye. With UV-vis spectrometric measurement, the visible absorbance had a linear relationship with the concentration of uranyl ions with a dynamic range from 1 nM to 50 nM, and a low detection limit of 0.48 nM ( ∼0.12 ppb) was obtained. Excellent selectivity and anti-interference capability in water samples were also certified. This facile visualized assay could be applied in detecting trace-level uranium for on-site environmental analysis.
本工作提出了一种快速灵敏的比色分析方法，使用双功能 DNA 探针修饰的琼脂糖微球（MBs）与级联信号放大系统结合，包括滚环扩增（RCA）和血红素/G-四链体催化的比色反应，用于可视化检测铀酰离子。该 DNA 探针集成了 UO 特异性 DNA 酶/底物作为靶标识别单元和 DNA 引物作为信号转换单元。铀酰离子的存在诱导 DNA 酶催化的 DNA 底物的有效切割。然后，与 MBs 结合的共轭引物从 MBs 中释放出来，引发 RCA 反应（第一轮扩增）。RCA 产物由重复的 G-四链体组成，这些 G-四链体可以通过血红素结合催化 ABTS 的氧化，引发第二个放大反应，导致肉眼可见的颜色。整个检测过程可以在 40 分钟内完成，包括铀酰的识别和 DNA 切割（5 分钟）、RCA 反应（30 分钟）以及通过肉眼或使用紫外-可见分光光度计进行数据读取（每个样品 5 分钟）。在最佳条件下，肉眼可以区分低至 5 nM 的铀酰离子。通过紫外-可见光谱测量，可见吸光度与铀酰离子浓度呈线性关系，动态范围为 1 nM 至 50 nM，检测限低至 0.48 nM（约 0.12 ppb）。在水样中还具有优异的选择性和抗干扰能力。这种简单的可视化检测方法可用于现场环境分析中痕量铀的检测。
