Key Laboratory of Luminescent and Real-Time Analytical Chemistry, Ministry of Education, College of Chemistry and Chemical Engineering, Southwest University , Chongqing 400715, PR China.
Anal Chem. 2017 Aug 15;89(16):8538-8544. doi: 10.1021/acs.analchem.7b02321. Epub 2017 Aug 3.
Usually, SERS technology requires labeling of the Raman reporter to obtain characteristic spectra for detection of biological samples. However, the number of labeled Raman reporters is often limited, resulting in the restricted improvement for sensitivity of SERS biosensor. In this work, switchable target-responsive 3D DNA hydrogels were introduced to precisely control trapping and release of Raman reporter toluidine blue (TB), which not only avoid labeling signal molecule but also improve the sensitivity of miRNA detection due to immobilization of abundant TB. In the absence of target miRNA, the DNA hydrogel presented a weak Raman signal because TB was far away from SERS substrates with an "OFF" status. However, the DNA hydrogel can be opened by the target miRNA to release TB producing strong Raman signal with an "ON" status. On the basis of this sensitive strategy, this switchable DNA hydrogel-based SERS platform can achieve quantitative detection of miRNA 155. Simultaneously, flexible SERS substrate (leaf@nafion@Ag) and target miRNA-induced duplex-specific nuclease signal amplification strategy were employed to significantly improve the sensitivity of the SERS platform. As a result, the as-proposed SERS platform can sensitively and selectively detect miRNA 155 with a wide linear range of 0.1 fM to 100 pM and low detection limit of 0.083 fM, which indicated that the platform has great potential to be applied in miRNA-related clinical diagnostics and biochemical researches.
通常情况下，SERS 技术需要对拉曼报告分子进行标记，以获得用于检测生物样本的特征光谱。然而，标记的拉曼报告分子的数量通常是有限的，这导致 SERS 生物传感器的灵敏度的提升受到限制。在这项工作中，引入了可切换的靶标响应型 3D DNA 水凝胶，以精确控制拉曼报告分子甲苯胺蓝（TB）的捕获和释放，这不仅避免了标记信号分子，而且由于 TB 的固定化，提高了 miRNA 检测的灵敏度。在不存在靶标 miRNA 的情况下，由于 TB 远离具有“关闭”状态的 SERS 基底，因此 DNA 水凝胶呈现出较弱的拉曼信号。然而，DNA 水凝胶可以被靶标 miRNA 打开，从而释放 TB，产生具有“开启”状态的强拉曼信号。基于这种敏感策略，这种可切换的基于 DNA 水凝胶的 SERS 平台可以实现 miRNA 155 的定量检测。同时，采用了灵活的 SERS 基底（叶@nafion@Ag）和靶标 miRNA 诱导的双链特异性核酸酶信号放大策略，显著提高了 SERS 平台的灵敏度。结果表明，所提出的 SERS 平台能够灵敏且选择性地检测 miRNA 155，线性范围为 0.1 fM 至 100 pM，检测限低至 0.083 fM，这表明该平台在 miRNA 相关的临床诊断和生化研究中有很大的应用潜力。
