Stimuli-responsive magnetic mesoporous silica microspheres Fe₃O₄@mSiO₂ have been widely used in biosensors. Here, we developed a CRISPR/Cas 12a system triggered Fe₃O₄@mSiO₂ for label-free detection of cancer marker miRNA-21. A lot of methylene blue (MB) molecules, as surface-enhanced Raman scattering (SERS) signal molecules, were loaded into the mesopores of Fe₃O₄@mSiO₂. G-quadruplex/hemin complexes, as gates, were capped on the surface of Fe₃O₄@mSiO₂. Target miRNA-21 initiated primer exchange reaction (PER), whose product could activate the CRISPR/Cas 12a system. Thus, the activated Cas12a non-specifically cleaved the single-stranded DNA linked between G-quadruplex and Fe₃O₄@mSiO₂, resulting in the removal of the cap and the release of the MB. The supernatant was dropped on the surface of ZnO NRs@AuNPs, and MB was detected through SERS to realize the sensitive detection of target miRNA-21. Meanwhile, the released G4/hemin complex in the supernatant was used to catalyze the oxidation of 2,2′-azinobis (3-ethylbenzothiazoline-6-sulfonic acid ammonium salt) (ABTS) for colorimetric detection. The limits of detections were 4.7 aM and 0.18 fM for SERS and colorimetry, respectively. In this way, a label-free SERS-colorimetry dual-mode sensing platform was established for highly sensitive analysis of oligonucleotides

中文翻译：

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基于 CRISPR/Cas12a 触发的 G 四链体封端磁性介孔多孔二氧化硅微球的无标记 SERS 比色双模式生物传感器


刺激响应磁性介孔二氧化硅微球 Fe₃O₄@mSiO₂ 已广泛用于生物传感器。在这里，我们开发了一种触发 Fe₃O₄@mSiO₂ 的 CRISPR/Cas 12a 系统，用于癌症标志物 miRNA-21 的无标记检测。大量亚甲基蓝 （MB） 分子作为表面增强拉曼散射 （SERS） 信号分子，被加载到 Fe₃O₄@mSiO₂ 的介孔中。G-四链体/血红素复合物作为门，被封在 Fe₃O_{4 @mSiO 2} 的表面。靶标 miRNA-21 引发引物交换反应 （PER），其产物可以激活 CRISPR/Cas 12a 系统。因此，激活的 Cas12a 非特异性地切割了 G-四链体和 Fe₃O₄@mSiO₂ 之间连接的单链 DNA，导致帽的去除和 MB 的释放。将上清液滴加在 ZnO NRs@AuNPs表面，通过 SERS 检测 MB，实现对靶标 miRNA-21 的灵敏检测。同时，上清液中释放的 G4/血红素复合物用于催化 2,2′-氮杂氮（3-乙基苯并噻唑啉-6-磺酸铵盐）的氧化 （ABTS） 进行比色检测。SERS 和比色法的检测限分别为 4.7 aM 和 0.18 fM。通过这种方式，建立了一个无标记的 SERS 比色双模式传感平台，用于寡核苷酸的高灵敏度分析