The ratiometric sensing strategy, which uses dual-signal output, drastically compensates for the background noise and interference from the detection environment, compared to the sensing methods that rely on a single-signal output. However, the stability of the reference signal has become the primary challenge in constructing a ratiometric detection sensor. Therefore, in order to achieve stable ratiometric signal sensing, methylene blue (MB) was encapsulated in the UiO-66-NH₂ framework and printed as a reference signal onto a screen-printed carbon electrode (SPCE), facilitating the precise detection of miR-21-5p. Subsequently, based on the ultra-sensitive detection mechanism of catalytic hairpin assembly (CHA), the combination of miR-21-5p with H₁ sequence on the Au-deposited SPCE triggered the loop-open of H1. After that, ferrocene-labeled H₂ (H₂-Fc) and H₃-Fc sequences were sequentially added to form a stable “T-shaped” structure, and miR-21-5p was released into the next cycle. Thus, the detection of miR-21-5p was quantified by the current ratio of Fc to MB, obtaining an ultra-low detection limit of 2.7 fM. This ratiometric sensing strategy based on SPCE offers a promising pathway for highly sensitive sensing platforms.

中文翻译：

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用于 miR-21-5p 高效电化学比例定量的机械稳定 UiO-66-NH2-MB 丝网印刷碳电极


与依赖单信号输出的传感方法相比，使用双信号输出的比率传感策略极大地补偿了来自检测环境的背景噪声和干扰。然而，参考信号的稳定性已成为构建比率检测传感器的主要挑战。因此，为了实现稳定的比例信号传感，将亚甲基蓝 （MB） 封装在 UiO-66-NH₂ 框架中，并作为参考信号打印到丝网印刷碳电极 （SPCE） 上，便于精确检测 miR-21-5p。随后，基于催化发夹组装 （CHA） 的超灵敏检测机制，miR-21-5p 与 H₁ 序列在沉积的 Au SPCE 上的结合触发了 H1 的开环。之后，相铁标记的 H₂ （H_2-Fc） 和 H_3-Fc 序列依次添加，形成稳定的“T 形”结构，miR-21-5p 被释放到下一个循环中。因此，通过 Fc 与 MB 的电流比对 miR-21-5p 的检测进行定量，获得 2.7 fM 的超低检测限。这种基于 SPCE 的比率传感策略为高灵敏度传感平台提供了一条有前途的途径。